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Review article, effects of water pollution on human health and disease heterogeneity: a review.


  • 1 Research Center for Economy of Upper Reaches of the Yangtse River/School of Economics, Chongqing Technology and Business University, Chongqing, China
  • 2 School of Economics and Management, Huzhou University, Huzhou, China

Background: More than 80% of sewage generated by human activities is discharged into rivers and oceans without any treatment, which results in environmental pollution and more than 50 diseases. 80% of diseases and 50% of child deaths worldwide are related to poor water quality.

Methods: This paper selected 85 relevant papers finally based on the keywords of water pollution, water quality, health, cancer, and so on.

Results: The impact of water pollution on human health is significant, although there may be regional, age, gender, and other differences in degree. The most common disease caused by water pollution is diarrhea, which is mainly transmitted by enteroviruses in the aquatic environment.

Discussion: Governments should strengthen water intervention management and carry out intervention measures to improve water quality and reduce water pollution’s impact on human health.


Water is an essential resource for human survival. According to the 2021 World Water Development Report released by UNESCO, the global use of freshwater has increased six-fold in the past 100 years and has been growing by about 1% per year since the 1980s. With the increase of water consumption, water quality is facing severe challenges. Industrialization, agricultural production, and urban life have resulted in the degradation and pollution of the environment, adversely affecting the water bodies (rivers and oceans) necessary for life, ultimately affecting human health and sustainable social development ( Xu et al., 2022a ). Globally, an estimated 80% of industrial and municipal wastewater is discharged into the environment without any prior treatment, with adverse effects on human health and ecosystems. This proportion is higher in the least developed countries, where sanitation and wastewater treatment facilities are severely lacking.

Sources of Water Pollution

Water pollution are mainly concentrated in industrialization, agricultural activities, natural factors, and insufficient water supply and sewage treatment facilities. First, industry is the main cause of water pollution, these industries include distillery industry, tannery industry, pulp and paper industry, textile industry, food industry, iron and steel industry, nuclear industry and so on. Various toxic chemicals, organic and inorganic substances, toxic solvents and volatile organic chemicals may be released in industrial production. If these wastes are released into aquatic ecosystems without adequate treatment, they will cause water pollution ( Chowdhary et al., 2020 ). Arsenic, cadmium, and chromium are vital pollutants discharged in wastewater, and the industrial sector is a significant contributor to harmful pollutants ( Chen et al., 2019 ). With the acceleration of urbanization, wastewater from industrial production has gradually increased. ( Wu et al., 2020 ). In addition, water pollution caused by industrialization is also greatly affected by foreign direct investment. Industrial water pollution in less developed countries is positively correlated with foreign direct investment ( Jorgenson, 2009 ). Second, water pollution is closely related to agriculture. Pesticides, nitrogen fertilizers and organic farm wastes from agriculture are significant causes of water pollution (RCEP, 1979). Agricultural activities will contaminate the water with nitrates, phosphorus, pesticides, soil sediments, salts and pathogens ( Parris, 2011 ). Furthermore, agriculture has severely damaged all freshwater systems in their pristine state ( Moss, 2008 ). Untreated or partially treated wastewater is widely used for irrigation in water-scarce regions of developing countries, including China and India, and the presence of pollutants in sewage poses risks to the environment and health. Taking China as an example, the imbalance in the quantity and quality of surface water resources has led to the long-term use of wastewater irrigation in some areas in developing countries to meet the water demand of agricultural production, resulting in serious agricultural land and food pollution, pesticide residues and heavy metal pollution threatening food safety and Human Health ( Lu et al., 2015 ). Pesticides have an adverse impact on health through drinking water. Comparing pesticide use with health life Expectancy Longitudinal Survey data, it was found that a 10% increase in pesticide use resulted in a 1% increase in the medical disability index over 65 years of age ( Lai, 2017 ). The case of the Musi River in India shows a higher incidence of morbidity in wastewater-irrigated villages than normal-water households. Third, water pollution is related to natural factors. Taking Child Loess Plateau as an example, the concentration of trace elements in water quality is higher than the average world level, and trace elements come from natural weathering and manufacture causes. Poor river water quality is associated with high sodium and salinity hazards ( Xiao et al., 2019 ). The most typical water pollution in the middle part of the loess Plateau is hexavalent chromium pollution, which is caused by the natural environment and human activities. Loess and mudstone are the main sources, and groundwater with high concentrations of hexavalent chromium is also an important factor in surface water pollution (He et al., 2020). Finally, water supply and sewage treatment facilities are also important factors affecting drinking water quality, especially in developing countries. In parallel with China rapid economic growth, industrialization and urbanization, underinvestment in basic water supply and treatment facilities has led to water pollution, increased incidence of infectious and parasitic diseases, and increased exposure to industrial chemicals, heavy metals and algal toxins ( Wu et al., 1999 ). An econometric model predicts the impact of water purification equipment on water quality and therefore human health. When the proportion of household water treated with water purification equipment is reduced from 100% to 90%, the expected health benefits are reduced by up to 96%.. When the risk of pretreatment water quality is high, the decline is even more significant ( Brown and Clasen, 2012 ).

To sum up, water pollution results from both human and natural factors. Various human activities will directly affect water quality, including urbanization, population growth, industrial production, climate change, and other factors ( Halder and Islam, 2015 ) and religious activities ( Dwivedi et al., 2018 ). Improper disposal of solid waste, sand, and gravel is also one reason for decreasing water quality ( Ustaoğlua et al., 2020 ).

Impact of Water Pollution on Human Health

Unsafe water has severe implications for human health. According to UNESCO 2021 World Water Development Report , about 829,000 people die each year from diarrhea caused by unsafe drinking water, sanitation, and hand hygiene, including nearly 300,000 children under the age of five, representing 5.3 percent of all deaths in this age group. Data from Palestine suggest that people who drink municipal water directly are more likely to suffer from diseases such as diarrhea than those who use desalinated and household-filtered drinking water ( Yassin et al., 2006 ). In a comparative study of tap water, purified water, and bottled water, tap water was an essential source of gastrointestinal disease ( Payment et al., 1997 ). Lack of water and sanitation services also increases the incidence of diseases such as cholera, trachoma, schistosomiasis, and helminthiasis. Data from studies in developing countries show a clear relationship between cholera and contaminated water, and household water treatment and storage can reduce cholera ( Gundry et al., 2004 ). In addition to disease, unsafe drinking water, and poor environmental hygiene can lead to gastrointestinal illness, inhibiting nutrient absorption and malnutrition. These effects are especially pronounced for children.

Purpose of This Paper

More than two million people worldwide die each year from diarrhoeal diseases, with poor sanitation and unsafe drinking water being the leading cause of nearly 90% of deaths and affecting children the most (United Nations, 2016). More than 50 kinds of diseases are caused by poor drinking water quality, and 80% of diseases and 50% of child deaths are related to poor drinking water quality in the world. However, water pollution causes diarrhea, skin diseases, malnutrition, and even cancer and other diseases related to water pollution. Therefore, it is necessary to study the impact of water pollution on human health, especially disease heterogeneity, and clarify the importance of clean drinking water, which has important theoretical and practical significance for realizing sustainable development goals. Unfortunately, although many kinds of literature focus on water pollution and a particular disease, there is still a lack of research results that systematically analyze the impact of water pollution on human health and the heterogeneity of diseases. Based on the above background and discussion, this paper focuses on the effect of water pollution on human health and its disease heterogeneity.

Materials and Methods

Search process.

This article uses keywords such as “water,” “water pollution,” “water quality,” “health,” “diarrhea,” “skin disease,” “cancer” and “children” to search Web of Science and Google Scholar include SCI and SSCI indexed papers, research reports, and works from 1990 to 2021.

Inclusion-Exclusion Criteria and Data Extraction Process

The existing literature shows that water pollution and human health are important research topics in health economics, and scholars have conducted in-depth research. As of 30 December 2021, 104 related literatures were searched, including research papers, reviews and conference papers. Then, according to the content relevancy, 19 papers were eliminated, and 85 papers remained. The purpose of this review is to summarize the impact of water pollution on human health and its disease heterogeneity and to explore how to improve human health by improving water pollution control measures.

Information extracted from all included papers included: author, publication date, sample country, study methodology, study purpose, and key findings. All analysis results will be analyzed according to the process in Figure 1 .


FIGURE 1 . Data extraction process (PRISMA).

The relevant information of the paper is exported to the Excel database through Endnote, and the duplicates are deleted. The results were initially extracted by one researcher and then cross-checked by another researcher to ensure that all data had been filtered and reviewed. If two researchers have different opinions, the two researchers will review together until a final agreement is reached.

Quality Assessment of the Literature

The JBI Critical Appraisal Checklist was used to evaluate the quality of each paper. The JBI (Joanna Briggs Institute) key assessment tool was developed by the JBI Scientific Committee after extensive peer review and is designed for system review. All features of the study that meet the following eight criteria are included in the final summary:1) clear purpose; 2) Complete information of sample variables; 3) Data basis; 4) the validity of data sorting; 5) ethical norms; (6); 7) Effective results; 8) Apply appropriate quantitative methods and state the results clearly. Method quality is evaluated by the Yes/No questions listed in the JBI Key Assessment List. Each analysis paper received 6 out of 8.

The quality of drinking water is an essential factor affecting human health. Poor drinking water quality has led to the occurrence of water-borne diseases. According to the World Health Organization (WHO) survey, 80% of the world’s diseases and 50% of the world’s child deaths are related to poor drinking water quality, and there are more than 50 diseases caused by poor drinking water quality. The quality of drinking water in developing countries is worrying. The negative health effects of water pollution remain the leading cause of morbidity and mortality in developing countries. Different from the existing literature review, this paper mainly studies the impact of water pollution on human health according to the heterogeneity of diseases. We focuses on diarrhea, skin diseases, cancer, child health, etc., and sorts out the main effects of water pollution on human health ( Table 1 ).


TABLE 1 . Major studies on the relationship between water pollution and health.

Water Pollution and Diarrhea

Diarrhea is a common symptom of gastrointestinal diseases and the most common disease caused by water pollution. Diarrhea is a leading cause of illness and death in young children in low-income countries. Diarrhoeal diseases account for 21% of annual deaths among children under 5 years of age in developing countries ( Waddington et al., 2009 ). Many infectious agents associated with diarrhea are directly related to contaminated water ( Ahmed and Ismail, 2018 ). Parasitic worms present in non-purifying drinking water when is consumed by human beings causes diseases ( Ansari and Akhmatov., 2020 ) . It was found that treated water from water treatment facilities was associated with a lower risk of diarrhea than untreated water for all ages ( Clasen et al., 2015 ). For example, in the southern region of Brazil, a study found that factors significantly associated with an increased risk of mortality from diarrhoea included lack of plumbed water, lack of flush toilets, poor housing conditions, and overcrowded households. Households without access to piped water had a 4.8 times higher risk of infant death from diarrhea than households with access to piped water ( Victora et al., 1988 )

Enteroviruses exist in the aquatic environment. More than 100 pathogenic viruses are excreted in human and animal excreta and spread in the environment through groundwater, estuarine water, seawater, rivers, sewage treatment plants, insufficiently treated water, drinking water, and private wells ( Fong and Lipp., 2005 ). A study in Pakistan showed that coliform contamination was found in some water sources. Improper disposal of sewage and solid waste, excessive use of pesticides and fertilizers, and deteriorating pipeline networks are the main causes of drinking water pollution. The main source of water-borne diseases such as gastroenteritis, dysentery, diarrhea, and viral hepatitis in this area is the water pollution of coliform bacteria ( Khan et al., 2013 ). Therefore, the most important role of water and sanitation health interventions is to hinder the transmission of diarrheal pathogens from the environment to humans ( Waddington et al., 2009 ).

Meta-analyses are the most commonly used method for water quality and diarrhea studies. It was found that improving water supply and sanitation reduced the overall incidence of diarrhea by 26%. Among Malaysian infants, having clean water and sanitation was associated with an 82% reduction in infant mortality, especially among infants who were not breastfed ( Esrey et al., 1991 ). All water quality and sanitation interventions significantly reduced the risk of diarrhoeal disease, and water quality interventions were found to be more effective than previously thought. Multiple interventions (including water, sanitation, and sanitation measures) were not more effective than single-focus interventions ( Fewtrell and Colford., 2005 ). Water quality interventions reduced the risk of diarrhoea in children and reduced the risk of E. coli contamination of stored water ( Arnold and Colford., 2007 ). Interventions to improve water quality are generally effective in preventing diarrhoea in children of all ages and under 5. However, some trials showed significant heterogeneity, which may be due to the research methods and their conditions ( Clasen et al., 2007 ).

Water Pollution and Skin Diseases

Contrary to common sense that swimming is good for health, studies as early as the 1950s found that the overall disease incidence in the swimming group was significantly higher than that in the non-swimming group. The survey shows that the incidence of the disease in people under the age of 10 is about 100% higher than that of people over 10 years old. Skin diseases account for a certain proportion ( Stevenson, 1953 ). A prospective epidemiological study of beach water pollution was conducted in Hong Kong in the summer of 1986–1987. The study found that swimmers on Hong Kong’s coastal beaches were more likely than non-swimmers to complain of systemic ailments such as skin and eyes. And swimming in more polluted beach waters has a much higher risk of contracting skin diseases and other diseases. Swimming-related disease symptom rates correlated with beach cleanliness ( Cheung et al., 1990 ).

A study of arsenic-affected villages in the southern Sindh province of Pakistan emphasized that skin diseases were caused by excessive water quality. By studying the relationship between excessive arsenic in drinking water caused by water pollution and skin diseases (mainly melanosis and keratosis), it was found that compared with people who consumed urban low-arsenic drinking water, the hair of people who consumed high-arsenic drinking water arsenic concentration increased significantly. The level of arsenic in drinking water directly affects the health of local residents, and skin disease is the most common clinical complication of arsenic poisoning. There is a correlation between arsenic concentrations in biological samples (hair and blood) from patients with skin diseases and intake of arsenic-contaminated drinking water ( Kazi et al., 2009 ). Another Bangladesh study showed that many people suffer from scabies due to river pollution ( Hanif et al., 2020 ). Not only that, but water pollution from industry can also cause skin cancer ( Arif et al., 2020 ).

Studies using meta-analysis have shown that exposure to polluted Marine recreational waters can have adverse consequences, including frequent skin discomfort (such as rash or itching). Skin diseases in swimmers may be caused by a variety of pathogenic microorganisms ( Yau et al., 2009 ). People (swimmers and non-swimmers) exposed to waters above threshold levels of bacteria had a higher relative risk of developing skin disease, and levels of bacteria in seawater were highly correlated with skin symptoms.

Studies have also suggested that swimmers are 3.5 times more likely to report skin diseases than non-swimmers. This difference may be a “risk perception bias” at work on swimmers, who are generally aware that such exposure may lead to health effects and are more likely to detect and report skin disorders. It is also possible that swimmers exaggerated their symptoms, reporting conditions that others would not classify as true skin disorders ( Fleisher and Kay. 2006 ).

Water Pollution and Cancer

According to WHO statistics, the number of cancer patients diagnosed in 2020 reached 19.3 million, while the number of deaths from cancer increased to 10 million. Currently, one-fifth of all global fevers will develop cancer during their lifetime. The types and amounts of carcinogens present in drinking water will vary depending on where they enter: contamination of the water source, water treatment processes, or when the water is delivered to users ( Morris, 1995 ).

From the perspective of water sources, arsenic, nitrate, chromium, etc. are highly associated with cancer. Ingestion of arsenic from drinking water can cause skin cancer and kidney and bladder cancer ( Marmot et al., 2007 ). The risk of cancer in the population from arsenic in the United States water supply may be comparable to the risk from tobacco smoke and radon in the home environment. However, individual susceptibility to the carcinogenic effects of arsenic varies ( Smith et al., 1992 ). A high association of arsenic in drinking water with lung cancer was demonstrated in a northern Chilean controlled study involving patients diagnosed with lung cancer and a frequency-matched hospital between 1994 and 1996. Studies have also shown a synergistic effect of smoking and arsenic intake in drinking water in causing lung cancer ( Ferreccio et al., 2000 ). Exposure to high arsenic levels in drinking water was also associated with the development of liver cancer, but this effect was not significant at exposure levels below 0.64 mg/L ( Lin et al., 2013 ).

Nitrates are a broader contaminant that is more closely associated with human cancers, especially colorectal cancer. A study in East Azerbaijan confirmed a significant association between colorectal cancer and nitrate in men, but not in women (Maleki et al., 2021). The carcinogenic risk of nitrates is concentration-dependent. The risk increases significantly when drinking water levels exceed 3.87 mg/L, well below the current drinking water standard of 50 mg/L. Drinking water with nitrate concentrations lower than current drinking water standards also increases the risk of colorectal cancer ( Schullehner et al., 2018 ).

Drinking water with high chromium content will bring high carcinogenicity caused by hexavalent chromium to residents. Drinking water intake of hexavalent chromium experiments showed that hexavalent chromium has the potential to cause human respiratory cancer. ( Zhitkovich, 2011 ). A case from Changhua County, Taiwan also showed that high levels of chromium pollution were associated with gastric cancer incidence ( Tseng et al., 2018 ).

There is a correlation between trihalomethane (THM) levels in drinking water and cancer mortality. Bladder and brain cancers in both men and women and non-Hodgkin’s lymphoma and kidney cancer in men were positively correlated with THM levels, and bladder cancer mortality had the strongest and most consistent association with THM exposure index ( Cantor et al., 1978 ).

From the perspective of water treatment process, carcinogens may be introduced during chlorine treatment, and drinking water is associated with all cancers, urinary cancers and gastrointestinal cancers ( Page et al., 1976 ). Chlorinated byproducts from the use of chlorine in water treatment are associated with an increased risk of bladder and rectal cancer, with perhaps 5,000 cases of bladder and 8,000 cases of rectal cancer occurring each year in the United States (Morris, 1995).

The impact of drinking water pollutants on cancer is complex. Epidemiological studies have shown that drinking water contaminants, such as chlorinated by-products, nitrates, arsenic, and radionuclides, are associated with cancer in humans ( Cantor, 1997 ). Pb, U, F- and no3- are the main groundwater pollutants and one of the potential causes of cancer ( Kaur et al., 2021 ). In addition, many other water pollutants are also considered carcinogenic, including herbicides and pesticides, and fertilizers that contain and release nitrates ( Marmot et al., 2007 ). A case from Hebei, China showed that the contamination of nitrogen compounds in well water was closely related to the use of nitrogen fertilizers in agriculture, and the levels of three nitrogen compounds in well water were significantly positively correlated with esophageal cancer mortality ( Zhang et al., 2003 ).

In addition, due to the time-lag effect, the impact of watershed water pollution on cancer is spatially heterogeneous. The mortality rate of esophageal cancer caused by water pollution is significantly higher downstream than in other regions due to the impact of historical water pollution ( Xu et al., 2019 ). A study based on changes in water quality in the watershed showed that a grade 6 deterioration in water quality resulted in a 9.3% increase in deaths from digestive cancer. ( Ebenstein, 2012 ).

Water Pollution and Child Health

Diarrhea is a common disease in children. Diarrhoeal diseases (including cholera) kill 1.8 million people each year, 90 per cent of them children under the age of five, mostly in developing countries. 88% of diarrhoeal diseases are caused by inadequate water supply, sanitation and hygiene (Team, 2004). A large proportion of these are caused by exposure to microbially infected water and food, and diarrhea in infants and young children can lead to malnutrition and reduced immune resistance, thereby increasing the likelihood of prolonged and recurrent diarrhea ( Marino, 2007 ). Pollution exposure experienced by children during critical periods of development is associated with height loss in adulthood ( Zaveri et al., 2020 ). Diseases directly related to water and sanitation, combined with malnutrition, also lead to other causes of death, such as measles and pneumonia. Child malnutrition and stunting due to inadequate water and sanitation will continue to affect more than one-third of children in the world ( Bartlett, 2003 ). A study from rural India showed that children living in households with tap water had significantly lower disease prevalence and duration ( Jalan and Ravallion, 2003 ).

In conclusion, water pollution is a significant cause of childhood diseases. Air, water, and soil pollution together killed 940,000 children worldwide in 2016, two-thirds of whom were under the age of 5, and the vast majority occurred in low- and middle-income countries ( Landrigan et al., 2018 ). The intensity of industrial organic water pollution is positively correlated with infant mortality and child mortality in less developed countries, and industrial water pollution is an important cause of infant and child mortality in less developed countries ( Jorgenson, 2009 ). In addition, arsenic in drinking water is a potential carcinogenic risk in children (García-Rico et al., 2018). Nitrate contamination in drinking water may cause goiter in children ( Vladeva et al.., 2000 ).


This paper reviews the environmental science, health, and medical literature, with a particular focus on epidemiological studies linking water quality, water pollution, and human disease, as well as studies on water-related disease morbidity and mortality. At the same time, special attention is paid to publications from the United Nations and the World Health Organization on water and sanitation health research. The purpose of this paper is to clarify the relationship between water pollution and human health, including: The relationship between water pollution and diarrhea, the mechanism of action, and the research situation of meta-analysis; The relationship between water pollution and skin diseases, pathogenic factors, and meta-analysis research; The relationship between water pollution and cancer, carcinogenic factors, and types of cancer; The relationship between water pollution and Child health, and the major childhood diseases caused.

A study of more than 100 literatures found that although factors such as country, region, age, and gender may have different influences, in general, water pollution has a huge impact on human health. Water pollution is the cause of many human diseases, mainly diarrhoea, skin diseases, cancer and various childhood diseases. The impact of water pollution on different diseases is mainly reflected in the following aspects. Firstly, diarrhea is the most easily caused disease by water pollution, mainly transmitted by enterovirus existing in the aquatic environment. The transmission environment of enterovirus depends on includes groundwater, river, seawater, sewage, drinking water, etc. Therefore, it is necessary to prevent the transmission of enterovirus from the environment to people through drinking water intervention. Secondly, exposure to or use of heavily polluted water is associated with a risk of skin diseases. Excessive bacteria in seawater and heavy metals in drinking water are the main pathogenic factors of skin diseases. Thirdly, water pollution can pose health risks to humans through any of the three links: the source of water, the treatment of water, and the delivery of water. Arsenic, nitrate, chromium, and trihalomethane are major carcinogens in water sources. Carcinogens may be introduced during chlorine treatment from water treatment. The effects of drinking water pollution on cancer are complex, including chlorinated by-products, heavy metals, radionuclides, herbicides and pesticides left in water, etc., Finally, water pollution is an important cause of children’s diseases. Contact with microbiologically infected water can cause diarrhoeal disease in children. Malnutrition and weakened immunity from diarrhoeal diseases can lead to other diseases.

This study systematically analyzed the impact of water pollution on human health and the heterogeneity of diseases from the perspective of different diseases, focusing on a detailed review of the relationship, mechanism and influencing factors of water pollution and diseases. From the point of view of limitations, this paper mainly focuses on the research of environmental science and environmental management, and the research on pathology is less involved. Based on this, future research can strengthen research at medical and pathological levels.

In response to the above research conclusions, countries, especially developing countries, need to adopt corresponding water management policies to reduce the harm caused by water pollution to human health. Firstly, there is a focus on water quality at the point of use, with interventions to improve water quality, including chlorination and safe storage ( Gundry et al., 2004 ), and provision of treated and clean water ( Khan et al., 2013 ). Secondly, in order to reduce the impact of water pollution on skin diseases, countries should conduct epidemiological studies on their own in order to formulate health-friendly bathing water quality standards suitable for their specific conditions ( Cheung et al., 1990 ). Thirdly, in order to reduce the cancer caused by water pollution, the whole-process supervision of water quality should be strengthened, that is, the purity of water sources, the scientific nature of water treatment and the effectiveness of drinking water monitoring. Fourthly, each society should prevent and control source pollution from production, consumption, and transportation ( Landrigan et al., 2018 ). Fifthly, health education is widely carried out. Introduce environmental education, educate residents on sanitary water through newspapers, magazines, television, Internet and other media, and enhance public health awareness. Train farmers to avoid overuse of agricultural chemicals that contaminate drinking water.

Author Contributions

Conceptualization, XX|; methodology, LL; data curation, HY; writing and editing, LL; project administration, XX|.

This article is a phased achievement of The National Social Science Fund of China: Research on the blocking mechanism of the critical poor households returning to poverty due to illness, No: 20BJY057.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

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Keywords: water pollution, human health, disease heterogeneity, water intervention, health cost

Citation: Lin L, Yang H and Xu X (2022) Effects of Water Pollution on Human Health and Disease Heterogeneity: A Review. Front. Environ. Sci. 10:880246. doi: 10.3389/fenvs.2022.880246

Received: 21 February 2022; Accepted: 09 June 2022; Published: 30 June 2022.

Reviewed by:

Copyright © 2022 Lin, Yang and Xu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Xiaocang Xu, [email protected]

This article is part of the Research Topic

Bioaerosol Emission Characteristics and the Epidemiological, Occupational, and Public Health Risk Assessment of Waste and Wastewater Management

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Institute of Medicine (US) Forum on Microbial Threats. Global Issues in Water, Sanitation, and Health: Workshop Summary. Washington (DC): National Academies Press (US); 2009.

Cover of Global Issues in Water, Sanitation, and Health

Global Issues in Water, Sanitation, and Health: Workshop Summary.

  • Hardcopy Version at National Academies Press

4 Addressing Risk for Waterborne Disease

Contributors to this chapter discuss a broad range of responses to the threat of waterborne disease, including drinking water disinfection, increasing access to water, improving sanitation, and investment in and implementation of public health interventions. Among these, the most seemingly straightforward approach—water treatment—is actually far from simple, as Philip Singer, of the University of North Carolina at Chapel Hill, demonstrates in the chapter’s first paper. Singer provides a quantitative overview of water quality and disinfection, emphasizing the use of chlorine as a disinfectant. He describes water quality factors (e.g., reduced inorganic material, dissolved organic carbon, and microbial contents) that influence chlorine’s effectiveness, and explains how sanitary engineers use the concept of “chlorine demand” to assess and address these factors in order to achieve water disinfection with chlorine. He also discusses parameters and limitations of various approaches to water treatment, including solar radiation, giving special attention to the significant barrier to disinfection posed by particulate matter and its removal by various filtration and flocculation methods.

In the developing world, the profound disease burden attributed to diarrhea makes it the most important target for waterborne disease prevention, according to workshop speaker Thomas Clasen of the London School of Hygiene and Tropical Medicine. Following a systematic review of interventions to improve water quality for preventing diarrheal disease ( Clasen et al., 2007a ), which compared interventions at the both the source (protected wells, bore holes, and distribution to public standpipes) and in the household (improved water storage, solar disinfection, filtration, and combined flocculation -disinfection), he and coauthors concluded that household-based interventions were nearly twice as effective as source-based measures. Clasen and coworkers subsequently conducted a cost-effectiveness analysis to determine the cost per disability-adjusted life year (DALY, a measure of disease burden) averted for a similar range of source and household interventions ( Clasen et al., 2007b ). The researchers found that upon reaching 50 percent of a country’s population, interventions involving household chlorination and solar disinfection paid for themselves and that all interventions were cost-effective.

The most prevalent method of home water treatment worldwide, boiling, was not included in these analyses. Although highly effective in reducing microbiological contamination, boiled water can be readily recontaminated; moreover, Clasen noted, boiling is relatively costly, is associated with risk for burn accidents, and results in indoor air pollution as well as carbon emissions ( Clasen, 2008 ). Because of boiling’s prominence, Clasen’s group has conducted assessments of its microbiological effectiveness and cost in several developing country settings in order to establish a benchmark against which other safe drinking water interventions can be compared. For example, in a recent study in semirural India, where more than 10 percent of households disinfect their drinking water by boiling, the researchers found that boiling, as practiced in these communities, significantly improves the microbiological quality of water (on a par with water filters), but does not fully remove the potential risk of waterborne pathogens ( Clasen et al., 2008 ). They also calculated that while the entry costs of boiling are the least of any water treatment option in this setting, the cost of continuing the practice annually is greater than the ongoing out-of-pocket cost of treating the same volume of water with sodium hypochlorite, or solar disinfection, and the five-year cost of boiling would also exceed most filtration options.

Efforts to increase the availability, uptake, and correct, consistent use of household water treatment and safe storage systems are spearheaded by the International Network to Promote Household Water and Safe Storage, a consortium of interested UN agencies, bilateral development agencies, international nongovernmental organizations (NGOs), research institutions, international professional associations, and private sector and industry associations ( Clasen, 2008 ; WHO, 2008 ). The Network now claims more than 100 members from government, UN agencies, international organizations, research institutions, NGOs, and the private sector and has accomplished much in terms of advocacy, communication, research, and implementation. However, despite these achievements, the mission of the Network to “achieve a significant reduction of waterborne disease, especially among children and the poor” is far from realization. Presently, only a tiny fraction of the millions of people who could benefit from household water treatment and safe storage (HWTS) interventions—far more than the one billion who use “unimproved” water sources, as previously noted—are being served, and those who need them most are the most difficult to reach.

In a recent report authored for the World Health Organization (WHO), Clasen (2008) examined efforts to scale up other important household-based interventions (e.g., oral rehydration salts, treated mosquito nets) for lessons of potential value to scaling up HWTS. He found several important recurring themes applicable to scaling up HWTS. These include the need to

  • focus on the user’s attitudes and aspirations;
  • take advantage of simple technologies (minimize behavior change);
  • promote nonhealth benefits, such as cost savings, convenience, and aesthetic appeal;
  • use schools, clinics, and women’s groups to gain access to more vulnerable population segments;
  • take advantage of existing manufacturers and supply channels to extend coverage;
  • provide performance-based financial incentives to drive distribution;
  • align international support and cooperation to encourage large-scale donor funding;
  • use free distribution to achieve rapid scale-up and improve equity;
  • use targeted subsidies, where possible, to leverage donor funding; and
  • encourage internationally-accepted standards to ensure product quality.

In his workshop presentation, Clasen noted that all introductions of novel health interventions to low-income populations face similar challenges—creating awareness, securing acceptance, ensuring access and affordability, establishing political commitment, addressing sustainability—but several additional barriers exist that must be overcome to scale up HWTS. These include

  • the widely held belief that diarrhea is not a disease;
  • skepticism about the effectiveness of water quality interventions;
  • technology shortcomings with the available interventions;
  • need for correct, consistent, sustained use (as compared with one-time interventions, such as vaccines);
  • the existence of several transmission pathways for waterborne disease;
  • suspicion on the part of the public health sector regarding the commercial agenda and lack of standards governing HWTS products;
  • the orphan status of HWTS within governmental ministries; and
  • the lack of focused international commitment and funding for diarrheal diseases.

“The goal of scaling up HWTS will not be achieved simply by putting more resources into existing programmes or transitioning current pilot projects to scale,” Clasen (2008) concludes.

The gap between where we are and where we need to be is to great given the urgency of the need. What is needed is a breakthrough. The largely public health orientation that has brought HWTS to its present point now need to enlist the help of another group of experts: consumer researchers, product designers, educators, social entrepreneurs, micro-financiers, business strategists and policy advocates. The private sector is an obvious partner; they not only possess much of this expertise but also the incentive and resources to develop the products, campaigns and delivery models for creating and meeting demand on a large scale. At the same time, market-driven, cost-recovery models are not likely to reach vast populations at the bottom of the economic pyramid where the disease burden associated with unsafe drinking water is heaviest . . . mass coverage among the most vulnerable populations may be impossible without free or heavily subsidized distribution. For this population segment, the public sector, UN organizations and NGOs who have special access to these population segments must engage donors to provide the necessary funding and then demonstrate their capacity to achieve both scale and uptake. Governments and international organizations can also help encourage responsible action by the private sector by implementing performance and safety standards and certification for HWTS products; reducing barriers to importation, production and distribution of proven products; and providing incentives for reaching marginalized populations. ( Clasen, 2008 )

Many of the ideas raised by Clasen regarding appropriately scaled water and sanitation infrastructure for developing countries are expanded upon by workshop speaker Joseph Hughes and coauthors, who offer an engineer’s perspective on water infrastructure in the developing world in the chapter’s second paper. Caravati et al. envision a new model for water and sanitation infrastructure that addresses global complexities, rather than a “one size fits all” approach based on developed-world systems. The authors describe several promising technologies that may help to address water and sanitation challenges in developing countries. First, however, they provide comprehensive background information on the dynamics of natural water movement, as well as the passage of water through the “engineered hydrologic cycle” of water and wastewater collection, treatment, and distribution.

Conventional, developed-world water and sanitation technologies “are often chemical-, energy- and operational-intensive, are based on heavy infrastructure systems (i.e., dams, pumps, distribution grids, etc.), and require considerable capital and maintenance, all of which hinder their use in much of the world,” the authors note. “If safe water and appropriate sanitation are to become accessible to those who are not currently served, new approaches and modern technologies must be employed. This will require a significant change in the way water and wastewater treatment systems are conceived and how they interact with other infrastructures systems (i.e., energy).” They outline a “new paradigm” for water and sanitation infrastructure and describe how progress under way in three vital areas—increased energy efficiency, availability of capital for business creation, and technology development—can advance this paradigm. Their contribution concludes with a review of research needed to fully develop a new, globally-appropriate model for water and sanitation infrastructure.

Given the global trend toward urbanization, particular attention must be paid to water and sanitation challenges for humans—tens of millions of them in megacities—living in close proximity to each other. The chapter’s third contribution, by workshop speaker Pete Kolsky of the World Bank and coauthors Kristof Bostoen and Caroline Hunt, focuses on the complex relationships that must be understood in order to recognize and address the threat of waterborne disease in urban settings, particularly in low-income communities. This essay originally appeared as a chapter in the book Scaling Urban Environmental Challenges: From Local to Global and Back ( Marcotullio and McGranahan, 2007 ).

Bostoen et al. begin by reviewing the effects of water supply, sanitation, and hygiene on health as viewed through two common models that clarify the complex interrelationships among these elements: classifications of water-related infections (see also Bradley in Chapter 1 ) and the F-diagram (depicted in Figure WO-13 ), a model of fecal-oral disease transmission. They then examine goals set by the international community for water and sanitation, along with obstacles that must be overcome in order to meet these goals, including the need to develop reliable measures of progress toward these goals. Following an examination of the significance of boundaries—“limits beyond which and individual or group feels no responsibility”—to urban water and sanitation issues, the authors conclude that institutional boundaries (which are central to many enviromental problems) must be identified and acknowledged. Improvements in water and sanitation services are significant only if they lead to change at the household level, they contend; therefore, household access to these services must be monitored and evaluated.

Ultimately, the threat of waterborne disease must be addressed through investment in safe water and sanitation interventions. Such investments are drastically underfunded, according to workshop speaker Vahid Alavian of the World Bank, who noted that the annual investment in water and sanitation needed to meet the MDGs exceeds $25 billion; only about half that sum is currently being spent. The World Bank is the largest global investor in water/sanitation investment, he added, but its portfolio of about $11 billion cannot begin to meet demand. His colleague Kolsky pointed out that the World Bank’s water and sanitation program at the Bank has received a grant of $20 million from the Bill and Melinda Gates Foundation to support sanitation scale-up and hygiene promotion projects, of which a significant fraction (15 to 20 percent) will be spent to evaluate the effectiveness of scaled-up interventions.

The chapter’s final essay, by speaker Sharon Hrynkow of the National Institute of Environmental Health Sciences (NIEHS) introduces a potential engine to drive the improvement of water quality and access in low-income settings: the phenomenon of social entrepreneurship. Using illustrative examples, she contrasts the social entrepreneur’s approach to solving these problems by focusing on delivering interventions or gathering information for policy purposes with that of medical researchers, who attempt to identify connections between toxins or microbes and illness, and then to reduce human exposure to disease agents.

“Increasing the dialogue between the medical research community and the social entrepreneur community would likely enhance operations on both sides,” Hrynkow concludes. In particular, she envisions an alternative to traditional medical grants, which rarely support policy development, that could support both medical research and social entrepreneurship and thereby encourage the transition of solutions for safe water and sanitation from basic science into practice.


Philip C. Singer, Ph.D. 1

University of North Carolina at Chapel Hill

This paper provides a discussion of important water quality factors impacting disinfection, with an emphasis on the use of chlorine as a disinfectant. It has been prepared to be somewhat tutorial in nature in an attempt to educate those unfamiliar with the complexities of water disinfection by chlorine. There are numerous textbooks with chapters on this subject ( Letterman, 1999 ; MWH, 2005 ).

Drinking Water Disinfectants

Several different types of disinfectants are used to treat drinking water:

  • free chlorine (HOCl/OCl − )
  • combined chlorine (i.e., monochloramine [NH 2 Cl])
  • ozone (O 3 )
  • chlorine dioxide (ClO 2 )
  • ultraviolet (UV) irradiation

When chlorine is added to water, it hydrolyzes to form hypochlorous acid (HOCl) and the hypochlorite ion (OCl − ). Hence, free chlorine in water is a combination of HOCl and OCl − . Chlorine is the most widely used disinfectant for the purification of drinking water in the world. Ozone and chlorine dioxide are also used to disinfect drinking water in the United States, western Europe, and in some of the advanced Pacific Rim nations, but not in the developing world. UV irradiation—including simple solar irradiation methods employed in the developing world—is a growing technology to disinfect drinking water.

Disinfection Kinetics

Free chlorine is an effective disinfectant for inactivating waterborne bacteria, viruses, and a variety of protozoan cysts (e.g., Giardia ), but it is not effective against Cryptosporidium . Its effectiveness for inactivating microorganisms can be quantified under various conditions by a measure known as CT. 2 CT values are derived from the CT term in the Chick-Watson expression

in which N is the number concentration of microorganisms, k is a rate constant, C is the concentration of the disinfectant, and T is time. Integration of Equation (1) yields the log of inactivation as a function of the concentration of disinfectant multiplied by the contact time, expressed in units of milligram-minutes per liter.

The rate constant, k, depends on the specific disinfectant, the type of organism, and temperature. N o is the initial concentration of organisms. Requisite CT values to achieve various degrees of inactivation are temperature-dependent.

Table 4-1 shows CT values for the inactivation of Giardia and viruses by chlorine over a range of temperatures. In water at 5°C, at a concentration of 1 milligram per liter (mg/L) of chlorine, it will take 149 minutes to achieve 3-log inactivation of Giardia . For colder waters, more chlorine and/or longer contact times are needed to achieve the same degree of inactivation. Table 4-1 also shows that the CT values for virus inactivation are smaller than those for Giardia , reflecting the fact that viruses are easier to inactivate with chlorine than Giardia. At residual chlorine levels of 0.2 to 0.3 mg/L under the same conditions, 3-log inactivation of Giardia will require on the order of 12.5 hours (not shown).

TABLE 4-1. CT Values (mg-min/L) for Microbial Inactivation by Free Chlorine residual) (pH 7.0, 1.0 mg/L Cl2.

CT Values (mg-min/L) for Microbial Inactivation by Free Chlorine residual) (pH 7.0, 1.0 mg/L Cl 2 .

Factors Affecting Disinfection with Chlorine

Several factors, in addition to temperature, influence the disinfectant potency of chlorine. The pH is an important consideration because it determines the form of chlorine present (HOCl or OCl − ). Hypochlorous acid is a more potent disinfectant than the hypochlorite ion; therefore, disinfection tends to be more effective with decreasing pH.

Chlorine Demand/Reducing Agents

Because chlorine is also a good oxidant, its stability in water is influenced by the presence of reduced inorganic and organic materials in the water, which exert a chlorine demand and chemically reduce the chlorine concentration. Additionally, the type and state of the microbial agents (i.e., whether the organisms occur as single cells or are associated with particles suspended in the water) affect the ability of chlorine to disinfect the water.

All of these factors determine the dose of chlorine that must be applied to a given water so that the target residual chlorine concentration (C) remaining at the end of a given contact time (T) can be achieved in order to meet the requisite CT value to ensure the desired degree of inactivation. The dose of chlorine applied, minus the chlorine residual, is known as the “chlorine demand” associated with a particular water supply. In a municipal water treatment facility, chlorine is usually applied to the raw water at the head of the treatment plant or after sedimentation or filtration, and the residual is measured at the point of entry to the distribution system. The difference between the dose and the residual is the chlorine demand and is due to consumption of chlorine by reduced organic and inorganic substances in the water. The higher the concentration of reduced organic or inorganic material, the greater the requisite chlorine dose needed to achieve a target residual and, hence, the greater the chlorine demand. In a village in which a woman collects water and carries it to her home where she adds chlorine to it, the chlorine demand reflects the amount of chlorine that must be added to the water in the container in order achieve the desired degree of inactivation in a specified time period, after which the water is presumed to be safe to drink.

To achieve the desired residual chlorine concentration to meet a target degree of inactivation as characterized by CT, one needs to calculate the dose of chlorine that must be added to any given water. To do this properly, one needs to know the degree to which reduced substances present in the water can lower the concentration of chlorine. This relationship is depicted in Figure 4-1 , which compares chlorine dose and residual free chlorine concentrations for several raw and partially treated waters (labeled here as MIEX ® effluents). The figure shows that, for the raw waters, 5–6 mg/L of chlorine must be applied in order to achieve a free chlorine residual of 1.0 mg/L. In this figure, the contact time is 24 hours. Hence, the chlorine demand of the raw water is 4–5 mg/L. For the treated waters, because a significant amount of dissolved organic material has been removed by treatment, the chlorine doses needed to achieve the same 1.0 mg/L free chlorine residual is 2–3 mg/L, reflecting a chlorine demand of 1–2 mg/L over 24 hours. Hence, in this case, treatment removed approximately 50 percent of the chlorine-demand associated with the dissolved organic material in the raw water.

Chlorine demand of several raw waters and partially treated waters (MIEX ® effluents). SOURCE: Reprinted from Boyer and Singer (2006) with permission from Elsevier.

Table 4-2 presents some examples of chlorine-demanding reactions with four inorganic reducing agents commonly found in raw water supplies: reduced (ferrous) iron (Fe(II)), (manganous) manganese (Mn(II)), sulfide (S(−II)), and ammonia (N(−III)). These balanced stoichiometric reactions illustrate the amount of chlorine that must be added to water to overcome the chlorine demand of these reducing agents. Iron, manganese, and sulfide typically derive from natural sources, whereas ammonia is often associated with municipal and agricultural discharges.

TABLE 4-2. Chlorine Demand of Various Inorganic Reducing Agents.

Chlorine Demand of Various Inorganic Reducing Agents.

Drinking water sources contaminated by sewage contain not only fecal bacteria and potentially pathogenic microorganisms but also organic material and ammonia, both of which exert substantial chlorine demands. As shown in Table 4-2 , the chlorine demand associated with ammonia is significant. Figure 4-2 depicts the progression of reactions that occur when increasing amounts of chlorine are added to water containing ammonia at a concentration of 0.5 mg/L as N. The first 2.5 mg/L of chlorine is converted to monochloramine; the next 2.5 mg/L of chlorine destroys the monochloramine. After this breakpoint is reached, free chlorine concentrations increase at essentially a 1:1 ratio as more chlorine is added. Thus, in order to get a free chlorine residual (the concentration of free chlorine beyond the breakpoint) necessary to meet the CT requirements for disinfection in water containing 0.5 mg/L of ammonia, at least 5 mg/L of chlorine must be added.

Breakpoint chlorination curve when chlorine is added to an ammonia-containing water. SOURCE: Reprinted from Water Chlorination/Chloramination Practices and Principles (M20) , with permission. (more...)

Natural organic material contains aromatic structures, unsaturated double bonds, and organic nitrogen, all of which react with chlorine. In addition to these oxidation reactions, chlorine participates in substitution and addition reactions to produce potentially carcinogenic halogenated byproducts. These include trihalomethanes, which are regulated in the United States by the Environmental Protection Agency and elsewhere in accordance with World Health Organization guidelines. On average, 1 to 1.5 mg/L of chlorine is consumed per mg/L of dissolved organic carbon (DOC) over the course of 24 hours, at pH 8 and 25°C.

Raw drinking waters generally contain a combination of chlorine-demanding impurities. A poor-quality surface water, for example, might contain 0.5 mg/L of ammonia and 6 mg/L of dissolved organic carbon, giving a total chlorine demand of 11-14 mg/L (5 mg/L to oxidize the ammonia in accordance with the breakpoint curve in Figure 4-2 and 6 to 9 mg/L for the 6 mg/L of dissolved organic carbon). For a better-quality surface water with 0.2 mg/L ammonia and 2 mg/L DOC, the chlorine demand would be 4-5 mg/L. For groundwater containing 1 mg/L iron, 0.5mg/L manganese, and 1 mg/L DOC, the chlorine demand would be on the order of 2.4 mg/L. Thus, different amounts of chlorine must be added in each case to achieve the same residual free chlorine levels needed for effective disinfection.

Measurement of Chlorine Residual

The most common method for measuring chlorine residual in treated water, the N,N -diethyl- p -phenylenediamine (DPD) colorimetric/spectrophotometric method, can distinguish between free and combined (monochloramine) chlorine species. However, because this method is subject to certain interferences, it must be performed and interpreted carefully, especially at low free chlorine concentrations and in waters containing dissolved organic nitrogen. Organic chloramines that are formed when free chlorine is added to water containing dissolved organic nitrogen, a component of the breakdown of proteinaceous material, also tend to react like free chlorine in the DPD colorimetric analysis. Because these organic chloramines do not have the disinfecting power of free chlorine, their presence gives an artificially high apparent free chlorine residual and a false sense of disinfection effectiveness. Additionally, while the minimum “detectable residual” with the DPD test is 0.2 mg/L chlorine, there are many instances where such detectable residuals have been measured by the DPD test but these waters have also been found to contain coliform bacteria that should not survive in the presence of chlorine at that concentration. Thus, measurements of free chlorine residual are subject to some uncertainty and must be interpreted carefully depending on water quality conditions.

Turbidity and Particle Content

The effectiveness of disinfection is impacted by the presence of particulate material in the water. Particles tend to protect the microorganisms from exposure to the disinfectant, especially if the microorganisms are present in an aggregated state. In the latter case, the organisms at the surface of the particle are exposed to the disinfectant but the organisms inside the aggregate are protected from exposure.

The turbidity of water is used as a surrogate for particle content. In the United States, water turbidity is monitored continually using a simple, relatively inexpensive device called a turbidimeter or nephelometer, which measures the light-scattering properties of particles at 90° to the incident light (see Figure 4-3 ). The intensity of scattered light is a function of the number, size, and shape of the particles present in the water (as well as of the wavelength of incident light, geometry and detection characteristics of the instrument, and its method of standardization and calibration). Water turbidity is therefore a collective reflection of a property of the particles (their light scattering characteristics) rather than a specific measure of particle size, number, or morphology.

Schematic of a nephelometer used to measure turbidity. SOURCE: Reprinted from http://www.eoc.csiro.au/instrument/html/marine/marine_images/hach_diagram.gif (accessed April 16, 2009) with permission from Hach Company.

In general, small particles scatter light more than larger particles, with the greatest degree of scattering resulting from particles that are about 0.5 microns (μm) in diameter, which is equivalent to the wavelength of the incident light. Viruses, which are much smaller in size (on the order of 0.03 μm), do not scatter light, whereas bacteria (0.5 to 1 μm in size), Cryptosporidium oocysts (3 to 5 μm), and Giardia cysts (10 to13 μm) do scatter light. Hence, the absence of a measurable turbidity does not guarantee that the water is free of harmful microorganisms.

A better measure of particle content can be achieved with particle size analyzers. A variety of particle size analyzers are commercially available for characterizing particles in water. Particle counters can measure particle size and concentration, providing information about size distribution (i.e., the number concentration of particles of various sizes) in the water. Optical methods (see Figure 4-4 ) compare light blockage by the different particles as a known volume of water is drawn through an orifice. The degree of blockage is proportional to the cross-sectional area of the particle. As particles of different size are drawn through the sensing zone of the instrument, the extent of blockage of the incident light is sorted into different channels according to the amount of light blocked, giving rise to a particle size distribution based on the diameter of an equivalent sphere with the same cross-sectional area. Resistivity-based methods, which measure the volume displacement of water by particles of different sizes in a salt solution, provide information on the size distribution of particles according to their volume-equivalent particle diameter.

Schematic of an optical particle counter. SOURCE: http://www.oilanalysis.com/backup/200207/PartCount-Fig1.jpg (accessed April 16, 2009) © Noria Corporation.

Image analyzers are recent additions to particle characterization techniques in water quality analysis. With these instruments, water samples can be continuously examined under a microscope, photographed, and the images stored in a computer file for subsequent review and analysis. These instruments permit identification of particle type and morphology. As previously noted, microorganisms in a sample may be present as single cells or as aggregates, and it is important to determine their degree of aggregation in order to assess their susceptibility to be inactivated by chlorine or any other disinfectant.

Particle Removal

Because microorganisms are often found in an aggregated state, and because particle-associated microorganisms are difficult to inactivate, the first line of defense against microorganisms of potential public health concern is filtration. Filtration removes particles, both particles that are present in an aggregate state and free, single-cell organisms which are themselves particulate in nature. Dis- infection with chemicals, such as chlorine, and physical inactivation methods, such as UV light, cannot be relied upon to safely disinfect water that has not undergone filtration. Effective filtration can occur via natural means (e.g., filtration that occurs by flow through porous media in a groundwater aquifer), engineered filtration (e.g., granular media filtration in a water treatment plant), or household filtration (e.g., filtration in a biosand or ceramic pot filter, both of which are being widely promoted for use in rural villages in developing countries). Once the raw water is relatively free of particulate material, chemical disinfectants or UV light can provide effective disinfection, provided the dose and contact time are sufficient.


Kevin C. Caravati

Georgia Tech Research Institute

Zakiya A. Seymour 3

Georgia Institute of Technology

Joseph B. Hughes, Ph.D., P.E., BCEE 4


Civil infrastructure can be broadly described as the systems, services, and facilities needed for a functioning community or society. Examples of easily recognized civil infrastructure include dams, bridges, buildings, roads, transmission and distribution lines, and communication technologies. These and other infrastructure systems, collectively, are central to the improvement of health, quality of life, and prosperity of communities. Among the most basic of all civil infrastructure systems are those that store, convey, treat, and provide potable water, as well as collect, treat, and safely discharge wastewater. Together, these systems have a dramatic impact on human health and the health of the environment in which people live.

Engineers and scientists have studied methodologies to purify water contaminated with biological, chemical, and physical contaminants for centuries, and well-accepted techniques for water and wastewater treatment have been employed in the United States and other parts of the developed world for many decades. Yet access to water and sanitation remains one of the largest challenges for societies around the globe. Of the world’s 6.5 billion-plus inhabitants, an estimated 1.2 billion people lack access to safe drinking water and 2.6 billion, or 42 percent of the world’s population, lack access to basic sanitation ( World Water Assessment Programme, 2006 ). Concerns of water access and improved sanitation are compounded by threats associated with climate change and a projected growth in population to 8 billion people by the year 2030. According to the Organisation for Economic Co-operation and Development (OECD), the number of persons in water-stressed countries is expected to increase to nearly four billion ( OECD, 2008 ). By 2025, more than half the nations in the world will face freshwater stress or shortages, and by 2050 up to 75 percent of an estimated 9.1 billion people could face freshwater scarcity ( Hightower and Pierce, 2008 ).

The future health, prosperity, and security of the human race will be strongly influenced by our ability to access clean water. Growing populations, rapid urbanization, expanding industrialization, changes in climate, growth in irrigated agriculture, and the globalization of corporations further contribute to our global water challenge. Infrastructure models deployed in the developed world over the past century are often ill suited to provide sustainable, scalable solutions. A new model is needed that addresses the complexities around global water and sanitation infrastructure.

Presented herein is an analysis of impediments to the solution of the world’s water and sanitation needs through existing technology. First, a background section is prepared to provide brief reviews of (1) the cycle of water in nature and (2) the cycle of water through engineered systems. Second, an examination of well-established water and wastewater infrastructure models detail a range of factors that exist as barriers to the translation of models globally. Finally, a discussion of the potential for technological innovations to provide advances in improving water and sanitation challenges in developing countries is presented.

Water is a widely occurring compound on Earth that is found in liquid, gaseous, and solid forms. Oceans cover approximately three-quarters of the Earth’s surface and contain over 97 percent of the world’s water supply. Oceanic water contains high salt concentrations and is unfit for human consumption without extensive treatment. Less than 3 percent of the Earth’s water is “fresh water,” and nearly 70 percent is in glaciers and icecaps, providing a mere 0.3 percent accessible for human consumption in lakes, reservoirs, rivers, and aquifers.

To understand water as a resource for human consumption, it is important to understand the dynamics of natural water movement among its three phases and the reservoirs for water that provide storage. Correspondingly, it is necessary to understand the flow, storage, and treatment of water through engineered systems used for the collection, treatment, and distribution of potable water and wastewater. For the purposes of clarity and consistency, the process of water movement and storage on Earth without human intervention is referred to as the “natural hydrologic cycle.” Water movement through infrastructure systems for the delivery of clean drinking water to the public is referred to as the “engineered hydrologic cycle.”

Natural Hydrologic Cycle

The largest reservoir for water is in the oceans. Evaporation 5 results in the transfer of water to the atmosphere. Condensation of gaseous water to the liquid state occurs within the atmosphere forming clouds and precipitation. A diagram of the natural hydrologic cycle is presented in Figure 4-5 . Roughly three-quarters of global precipitation results in water returning to the oceans. The fraction that falls on land initiates the terrestrial component of the water cycle. On land, water will be present as a solid (ice and snow) and as a liquid. The inflow, or precipitation that falls on land, is the predominant source of water required for human consumption, agriculture and food production, industrial waste disposal processes, heat dissipation in energy production, and for support of natural and seminatural ecosystems ( World Water Assessment Programme, 2003 ). Outflow of the natural water cycle includes drainage to the oceans via rivers, lakes, and wetlands; evapotranspiration of water to the atmosphere from soils by plants; and evaporation from fresh water reservoirs. Water that collects into flowing bodies of water is categorized as surface water (streamflow). Water that seeps through soils into underlying rock layers is contained as groundwater. Surface water systems are more rapidly recharged than groundwater. In fact, the flow of groundwater systems is very slow and the volume of water they can produce is often finite.

The hydrologic cycle. SOURCE: USGS (2008).

Engineered Hydrologic Cycle

Engineered water systems are processes that convey, store, and alter water quality. Many of these processes are designed to enhance what characteristically occurs in the natural environment (i.e., the breakdown of organic contaminants in wastewater by bacterial communities). A vast network interlinking water, sanitation, and energy infrastructure systems has been built to ensure clean drinking water and mitigate the impacts of waste on human and environmental health. The development and reliability of this network, collectively referred to as the “engineered hydrologic cycle,” are critical factors in the growth and health of populations. Major components to describe the details of this network consist of (1) water supply creation and protection, (2) water and wastewater treatment, and (3) water quality.

Creation and Protection of Water Supply

An estimated 48 percent of the freshwater supply in the United States is used for energy production. The remaining percentage is classified into irrigation (34 percent), public use (11 percent), industrial use (5 percent), and mining, livestock, and aquaculture (less than 2 percent; USGS, 2005 ). While the focus of this discussion is public use, the largest supply issues are driven by the energy and agriculture sectors.

Due to the scarcity of freshwater throughout the world, careful consideration must be given to create and protect water supplies. Over the past 200 years, human activities have developed to such an extent that only a few natural water bodies remain ( World Water Assessment Programme, 2003 ). Water management over the past century has focused on large-scale diversions of water out of natural systems; more than 60 percent of the world’s rivers have undergone major hydrological alterations ( Revenga et al., 1998 ). Throughout much of the developed world, large reservoirs with intake structures, dams, and distribution facilities provide clean water to millions over vast areas. Well fields that tap highly productive aquifers can do the same. Additional infrastructure changes also include extensive channelization of river systems, massive pumping of aquifers, and long-distance water conveyance systems. These engineered systems, representing the conventional approach for creating water supplies, have significantly altered lifestyles and the environment by ensuring the sustainability of water resources ( Gleick, 2006 ).

In conjunction with creating water supplies, the development of resource protection programs ensures water quality. Resource protection involves several stakeholders, including regulatory agents, governments, commercial users, and residential consumers. It comprises a variety of watershed protection practices, including restricting land use in sensitive areas, managing solid wastes, and preventing saltwater intrusion. Collectively, through the application of these methods and the cooperative assistance of involved stakeholders, water supplies are safeguarded and public health is protected. The New York City Watershed Partnership project, described in Box 4-1 , is an example of a successful large-scale water supply protection and infrastructure project. This partnership provides unfiltered drinking water to nine million people while preserving the economic viability and social character of the communities located in the upstate watershed ( EPA, 2006 ).

Unfiltered Drinking Water for Millions: The New York City Watershed Partnership. New York City’s water managers face two challenges: protecting the public health of both the city’s (more...)

Water and Wastewater Treatment

To ensure clean water supplies in the developed world, engineers have created treatment systems to provide safe drinking water from both surface water and groundwater sources, and to return the resulting wastewater to surface waters (on rare occasions water is returned to aquifers). These systems, which include drinking water and wastewater treatment facilities, conveyance systems, above-ground storage facilities, and residuals management sites, are necessary for providing water for public use as well as for disposing of wastewater and wastes in a safe and efficient manner. A graphic depiction of these water and wastewater treatment systems is shown in Figure 4-6 .

Detailed diagram of conventional water and wastewater treatment systems. SOURCE: Reprinted from ABB (2007) with permission, www.abb.com/water.

Initially, surface water and groundwater are directed to a drinking water treatment plant. The water is then treated to remove particulate matter (i.e., solids) and dissolved contaminants and is disinfected. Additional treatment for taste, appearance, hardness, and odor occurs before it is stored and/or piped to a distribution system. This distribution system delivers drinking water for consumption. After the public use, wastewater, through a collection system, is sent to a wastewater treatment plant for solids removal and biological and chemical treatment. Afterward, treated wastewater is discharged to a river, lake, reservoir, ocean, or aquifer system.

Water and wastewater treatment methodologies involve physical, biological, and chemical processes; these treatments are usually completed in series, and are, subsequently, also known as primary, secondary, and tertiary treatments. In potable water treatment, physical (i.e., filtration) and chemical (i.e., chlorination) are most common. In wastewater treatment, biological treatment is used to remove organic matter (i.e., biochemical oxygen demand or BOD) and treat residuals (i.e., anaerobic digestion). Physical treatment (i.e., gravity separations) and chemical treatment (i.e., chlorination) are also essential in wastewater treatment facilities. If the wastewater has been created in an industrial facility, additional treatment(s) may be required prior to its discharge. Listed in Table 4-3 , as modified from Tchobanoglous et al. (2003) and in Viessman and Hammer (1985) , are various methodologies that treat water and wastewater.

TABLE 4-3. Conventional Water and Wastewater Treatment Methodologies.

Conventional Water and Wastewater Treatment Methodologies.

Treating water before and after public use is essential; often, surface waters that receive wastewater discharges are typically a drinking water source for communities downstream. Practices implemented in one part of a watershed have the capacity to impact its potential use as a water source. Consequently, the conventional engineered solution for drinking water and wastewater treatment, as seen in the developed world, imparts its own engineered hydrologic cycle in concert with the natural water cycle, providing integrated resource protection to reduce vulnerability and maintain the quality of water sources.

Water Quality

The quality of water found in rivers, lakes, reservoirs, and groundwater depends on several linked factors. These factors include geology, climate topography, biological processes, land use, and water residence time. Nonetheless, the degree of sanitation practiced is the most critical determinant of contamination of drinking water with pathogens.

Programs dedicated to water and sanitation typically spend 95 percent of their resources on water ( Black, 2008 ), yet the global return on investments in low-cost sanitation provision may be in the range of $9 for each $1 spent ( Hutton et al., 2006 ). Human and agricultural wastes pose a remarkably high risk to waterborne disease. The principal bacteria that cause intestinal disease include several genera of Salmonella, Shigella, Vibrio cholerae, Leptospira , and Yersinia enterocolitica . An average bowel movement weighs 250 grams and an average human produces 77 pounds of excrement per year ( George, 2008 ); one gram of feces can contain 10 million viruses, 1 million bacteria, 1,000 parasite cysts, and 100 worm eggs ( George, 2008 ), carrying the potential to threaten any water source. In nature, there is no pure water, but water that has been tainted due to poor sanitation is particularly poor quality.

The measurements of certain physical, chemical, and biological water quality parameters assist in determining the suitability of water for various purposes, the effectiveness of water and wastewater systems, and its potential impacts on public health. Water quality regulations in the United States and other developed countries require that water be properly managed to improve human health and minimize environmental degradation. In the United States, the number of water quality parameters evaluated on a routine basis at water treatment and wastewater treatment plants is considerable. A short list of examples includes pH, dissolved oxygen, hardness, turbidity, BOD, nitrate, ammonia, color, fecal coliform bacteria, heavy metals, and toxic organic pollutants, among others. Table 4-4 , as provided by the American Water Works Association ( AWWA, 1999 ), summarizes the source and significance of certain water quality parameters.

TABLE 4-4. Water Quality Parameters.

Water Quality Parameters.

Established Water/Wastewater Infrastructure Models

The development of the engineered hydrologic cycle is the basis for establishing water/wastewater infrastructure models. For discussion purposes, currently established water/wastewater infrastructure models common in the United States are referred to as the “conventional infrastructure model.” Where traditional infrastructure models are not used, the term “household water treatment and storage model” is employed. Components of each model are discussed in the following section along with the barriers for increased implementation of both.

Conventional Water/Wastewater Infrastructure Model

The overall success of conventional water infrastructure in the developed world is attributed to the complementary advancements in engineered, economic, and societal systems since the mid-1800s. Conventional water and sanitation technologies, as seen in most developed regions, were mature decades ago—although through research engineers have continued to improve the performance of treatment systems. These technologies are often chemical-, energy-, and operational-intensive, are based on heavy infrastructure systems (i.e., dams, pumps, distribution grids, etc.), and require considerable capital and maintenance, all of which hinder their use in much of the world ( Shannon et al., 2008 ). The success of the U.S. water infrastructure improvements relies on several interrelated and critical elements. Examples are provided below:

  • Energy Use . Energy consumption represents the largest operational cost in water and wastewater treatment. It is essential for source collection and conveyance systems, distribution systems, and treatment. It is also needed for pumps (within wells, at surface water intakes, and for distributing water), aerators, chemical feed systems, and biological treatment systems.
  • Chemical Use . Water and wastewater treatment require large quantities of chemicals to treat water efficiently and to remove elements that may inhibit water quality. Chemicals are also used for corrosion control and disinfection within the distribution systems. Chemical use can include ammonia, chlorine compounds, antiscalants, ozone, permanganate, alum, ferric salts, sodium hydroxide, hydrochloric acid, and ion exchange resins.
  • Subsidies. Subsidies are often required to ensure widespread acceptance and adoption of water supply and wastewater treatment to the public. Additionally, certain subsidies, such as those provided to the agricultural industry within the United States, can deeply impact the availability of water. Regulatory agencies and governments must consider the interests of the public.
  • Regulatory Frameworks. Regulatory frameworks are needed to establish ownership rights, to set standards for drinking water and industrial waste-water treatment, to develop water permitting requirements, and to determine resource allocations (power generation, recreation, agriculture).
  • Available Capital . Determining the upfront capital available for the design and construction costs of a water infrastructure system is essential. Furthermore, careful consideration must be given to the long-term operation and maintenance needs of the facilities. In most developed countries, these expenditures are typically financed by the public sector.
  • Property Ownership. Obtaining the appropriate property rights-of-way is necessary to protect the components of the water infrastructure system, including the watersheds, reservoirs, piping, and distribution sites. Additionally, determining property ownership will provide useful knowledge for the system users and the ability to establish a payment system for water usage.
  • Social Acceptance. While regulatory frameworks establish the legality frameworks, the public must also accept components of a water infrastructure system. There are several decisions made when developing a water infrastructure system, such as determining financing options, permitting restrictions, and treatment and sludge disposal methods. These alternatives highlight the complexity of decision matrices and stress the need for collaboration with the public.

Barriers for Expanded Application of Conventional Infrastructure Models

The components essential for building conventional water infrastructure systems often do not exist in developing countries. Reliable, consistent supplies of energy are required, and chemicals for treatment may not be obtainable. Governments in developing nations often lack the authority and resources to implement large-scale programs, or they may be plagued by corruption or governance issues. Organizations may be able to obtain the initial funding but may not have sufficient revenue collection systems needed for operational costs. Additionally, concerns exist about the development of water resources through major dam-building programs. This lack of resources, revenue, and regulation impedes the successful development of the conventional water infrastructure model in developing countries. Specific examples of barriers that effectively prohibit the reliable and effective use of conventional water and wastewater infrastructure systems are illustrated below.

Water supply stress Worldwide water supplies and the quality of freshwater are being impacted by climate change, demographic shifts, and population growth, creating regions experiencing water stress. The traditional solution to water stress has been to enhance the water supply through conveyance from increasingly distant sources. Often, these systems include well-field and water distribution networks, household connections for wastewater conveyance and treatment, and the installation of dams for combined hydroelectric power generation and water supply reservoirs. Yet, this approach is frequently found unreliable in developing countries due to environmental, social, and economic reasons ( Gleick, 2000 ). Traditional water management methods to divert water out of natural systems, if built, have not been maintained effectively; thus, much of the water supply is restricted to nearby surface water or shallow groundwater, making it more difficult to find and retain water supplies for croplands and urban centers. Both surface and groundwater supplies can become contaminated from human, industrial, and animal waste; depending on water demands, groundwater water tables can fall below acceptable recharge levels.

Concentrated population growth places a particular stress on water supplies. Over the next century, an additional three billion people will live in urban areas ( Zimmerman et al., 2008 ), further focusing water demand and waste production. Outside of urban areas, the loss of forests and vegetation to support urbanization causes increased sedimentation, loss of wetlands, and eutrophication ( Zimmerman et al., 2008 ). By the year 2025, water withdrawals are expected to increase from current levels by 50 percent in developing countries and 18 percent in developed countries ( Zimmerman et al., 2008 ). Demands from the agricultural, industrial, and energy sectors will compete with the needs of coastal developments; economic development will likely take precedence over resource protection. Lacking strong governance systems, agencies are subject to corruption and an inability to create or enforce environmental protection practices to ensure the sustainability of water resources.

Energy The lack of reliable energy is problematic for establishing conventional solutions in developing regions. Energy requirements for water and wastewater treatment are staggering. Without reliable energy systems, conventional treatment processes simply fail. Equally important to having energy to treat water will be the impact of energy systems on water stress. Growth in future energy production is projected to be highest in water poor regions. Furthermore, the regions with the highest increased projected energy demand will include coastal North and South America, the Middle East, India, and China. Increasing energy production will require a reevaluation of water resources and reduce freshwater availability.

Poor sanitation The effect of poor or nonexistent sanitation on water resources can overwhelm the ability of conventional water treatment systems to provide safe water. Without regulations, surface and groundwater systems are subject to contamination with fecal matter, rendering them unfit for use as a drinking water source without advanced treatment systems. For millions of people, water is simply too precious to be used for disposal of waste, therefore the waste will not enter or be conveyed through a sewer system even if one existed. Conventional wastewater treatment requires that waste be conveyed by water. In many locations that simply will not occur and the engineered water cycle is “short circuited.”

Economics and regulatory needs The price one actually pays for water is but a small fraction of what it truly costs to extract it, deliver it to users, and treat it after its use ( Revenga, 2009 ). Subsidies that hide the true costs of water or subsidies for programs that can pay for themselves have proven to be ineffective. Furthermore, governments are less willing to subsidize large dam or water infrastructure projects and are shifting more responsibility to regional and local governments ( Gleick, 2000 ).

Privatization of water services (and energy services) has been a “widespread failure” according to a recent United Nations Development Program study ( Bayliss and McKinley, 2007 ). Private investors have shied away from investing in public utilities, and the private enterprises have focused primarily on cost recovery and not the provision of services at equitable prices to the poor. Current efforts tend to focus on building the capacity of the public sector, but funding sources for such projects are scarce. Energy subsidies in India encourage ground-water users to pump more than they actually need, leading to massive declines in local and regional water tables ( Gleick, 2000 ). Agricultural subsidies in Asia encourage the consumption of inflows to the Aral Sea, resulting in shrinkage of the Sea and loss of species and livelihoods ( Gleick, 2000 ).

Policies and pricing decisions that do not effectively price water lead to misuse. The poor pay more for water that is delivered from private sources compared to water provided by a municipality ( World Water Assessment Programme, 2006 ). The World Health Organization defines reasonable access as the availability of at least 20 liters per capita per day from a source within one kilometer of the user’s dwelling ( WHO, 2008 ).

Regulatory frameworks are particularly important for sanitation services, but sanitation is typically underfunded. Waste disposal services are often nonexistent in poor rural areas or crowded urban centers or are unaffordable. Subsidies often are needed to promote access to utility services ( Bayliss and McKinley, 2007 ), and some utilities have introduced “lifeline tariffs” in which minimal levels of utility services are provided free or at low cost. Oftentimes, utility connections to poor neighborhoods are subsidized; water delivery from these connections needs to be safe and reliable; otherwise public trust in the local authorities is lost.

Issues of property ownership plague megaslums and rural areas, which complicates the delivery of water and energy services. The ability of dwellers or residents to pay for services and the ability to collect connection fees and monthly user fees can be barriers to improvements.

The adoption of a traditional water infrastructure system by many institutions has reached a plateau as environmental and social concerns have increased. Population growth and changing demographics have limited unbridled expansion opportunities that existed in the nineteenth and twentieth centuries. Financing of major projects has declined due to rising material costs, legal opposition from stakeholders, and now a tightened credit market.

Household Water Treatment and Storage Water Treatment Model

The most common household water treatment and safe storage systems include chlorination, filtration (biosand and ceramic), solar disinfection, combined filtration/chlorination, and combined flocculation /chlorination. Lantagne et al. (2006) provide a thorough review of these systems with a summary of performance criteria for each option. These systems focus on point-of-use or point-of-entry drinking water treatment and storage. Chlorination and flocculation/chlorination methods are scalable at the village and national level; scalability issues exist for biosand, ceramic, solar disinfection, and filtration/chlorination options. The adoption of household water treatment and storage systems has increased in developing nations in recent years. These systems are small-scale applications of certain basic processes in the engineered hydrologic cycle discussed previously, but the treatment is not as comprehensive as is typically done in conventional systems.

This model has been most successful when local organizations have the capacity to provide materials and replacement parts, can provide technical assistance, and can facilitate behavior change communications ( Lantagne et al., 2006 ). Significant challenges for these systems include evaluating the health impacts of these interventions in “real-world” settings, sustainability of the projects, and scalability in terms of reaching people without access to improved water sources ( Lantagne et al., 2006 ).

Barriers for the Household Water Treatment System Model

Community education is often necessary to ensure adoption of the intervention and to ensure community acceptance. These efforts are labor- and time-intensive, and success is measured in small steps. Cultural traditions can impact the adoption rates of practices that are generally accepted in the developed world. For example, in Western Cameroon, it is considered “taboo” by some to use household chlorination (locally known as “poison”) in drinking water (personal communication with P. Njodzeka of the Life and Water Development Group, Cameroon, December 30, 2008).

In rural farming villages, household water treatment systems are simply unaffordable to many where household income can be $0.25 per day or less, and residents collect water from springs or often drink from contaminated streams.

The adaptability rate of a household intervention is an area for further research. While knowledge of the intervention may be widespread, actual adoption rates may lag due to economic factors, a perceived lack of personal benefit from the intervention, and cultural or political issues.

A Paradigm Shift for Water and Sanitation Infrastructure

Variability exists in the designs and operation of conventional water infrastructure systems, but these generally follow a “prescriptive approach” based on Victorian age (or older) methodologies. Even if the capital and human will existed to create conventional systems for all people, it would take decades to build and it is uncertain that these systems are well suited to meet the demands of population growth and urbanization. If safe water and appropriate sanitation are to become accessible to those who are not currently served, new approaches and modern technologies must be employed. This will require a significant change in the way water and wastewater treatment systems are conceived and how they interact with other infrastructure systems (i.e., energy). Proposed features of a paradigm shift to address the complex challenges around global water and sanitation are shown in Table 4-5 .

TABLE 4-5. Paradigm Shifts Addressing Water and Sanitation Infrastructure.

Paradigm Shifts Addressing Water and Sanitation Infrastructure.

The Innovation Challenge

The benefits of conventional water infrastructure systems are undeniable. Human health has been improved as has life expectancy. Water supplies in most developed nations are relatively clean and reliable. Many of the water-related diseases rampant in Europe and North America in the late 1800s are no longer a concern in those regions ( Gleick, 2000 ). However, the implementation of these systems carried a tremendous economic cost, and they require a continuous investment in operations and maintenance. In addition, they have greatly disturbed many ecosystems, displaced populations, and created new health concerns such as the formation of trihalomethanes, a disinfection byproduct linked to cancer.

Research activities in the United States, and other parts of the developed world, have focused on advancing the water and sanitation approaches within the conventional water and wastewater treatment paradigm. By comparison, research and technology for the development of nonconventional water and sanitation has been very limited, and market penetration of many of the proposed solutions has been inadequate and difficult to sustain. In order to make rapid progress in solving the world’s water challenge, it is essential that research be directed at approaches that can be developed within the “new paradigm” presented earlier. In addition, research must be focused on water efficiency in the major water usage areas of energy and agriculture. Whether interest is directed to new treatment systems or to increased efficiency, there is reason to believe that new solutions are possible and with focused and sustained efforts, significant improvements in water access and sanitation can be realized. In this section, three specific areas where innovation yields interest today are presented. First, are changes in the water-energy nexus. Second, is the availability of capital for business creation in developing countries. Third, are examples of technology development that suggest that nonconventional approaches to treat water and wastewater are in existence and could be refined to meet the conditions of a “new paradigm.”

The Water-Energy Nexus

Energy and water use are intimately linked. Domestic water use requires significant energy for pumping and treatment. American public water supply and treatment facilities consume about 56 billion kilowatt-hours per year—enough electricity to power more than 5 million homes for an entire year ( EPA, 2009 ). Thus, saving water saves energy and results in fewer greenhouse gas emissions. On the other hand, energy production uses and impacts domestic water supplies. As stated previously, cooling water represents nearly half of the volumetric water use in the United States annually. The power industry requires reliable supplies of water for cooling, for flue gas desulfurization and ash handling, and for hydroelectric power generation. As population grows, so does the demand for electric power and water for agricultural, municipal, residential, commercial, industrial, and power generation uses, potentially straining water supplies. Because the water supply is limited, growth in demand can only be met by developing technologies that reduce the volume of water required per kilowatt-hour of power generated. In short, the ideal way to reduce water consumption is to increase energy efficiency.

Rapidly developing nations must be able to realize the benefits of energy efficiency while building their infrastructure. A study by the McKinsey Global Institute (2007) reported that the global demand for energy is estimated to grow at a rate averaging 2.2 percent a year up to the year 2020, a rate that is the fastest since 1986. Developing countries will account for an overwhelming 85 percent of energy demand growth to the year 2020. However, the McKinsey study reported that it is possible to improve energy efficiency in a manner that could cut energy demand growth by at least half. The greatest productivity improvement opportunity is in the global residential sector (the world’s largest consumer of energy). Bringing the preferred existing, or yet to be discovered, ways to increase energy efficiency in buildings, residences, and other operations that derive electricity from stationary power sources is essential to mitigate water stress and decrease water use.

The water-energy nexus extends beyond efficiency. Today, a transition in energy production is occurring for a model of distributed power systems ( Platz and Schroeder, 2007 ). While most of the world’s power produced today comes from centralized power plants using fossil fuel combustion or nuclear fission to drive steam turbines, these centralized power systems require significant capital investments and extensive distribution networks to reach consumers. The development of small-scale, distributed energy systems is an area of research and development today. This includes solar generation, wind and water turbine generators, and other technologies that create electricity at the point of demand. As markets increase, the cost of onsite power generation will decrease due to economies of scale and it should be possible to infuse developing countries with power generation without the 10 to 20 years of construction of conventional stationary power systems. With the advent of distributed energy comes the potential for distributed water and wastewater treatment, using technologies or approaches that differ significantly from conventional water and wastewater systems. In fact, it is possible to create wastewater treatment systems that generate electricity that would themselves be a distributed power generator.

Innovative Financing and Business Models for the Water, Sanitation, and Energy Sectors

Intermediate solutions that address the technical and financial gap between point-of-use technologies and the heavy infrastructure projects require innovative financing approaches. National governments often lack the financial means to extend water, sanitation, and energy coverage through infrastructure investments. Cardone and Fonseca (2006) describe innovative financing trends and case studies for small-town water and sanitation services.

In most developing countries, financial services such as bank loans, insurance, and pension funds are not readily accessible by the poor ( NWP, 2007 ). Microfinancing services supply capital to poor people considered “unbankable” by the conventional financial sector, with loans for as little as $50 ( Morgan Stanley, 2007 ). Since 1976, microfinancing mechanisms have been providing small loans to the poor and the microfinance sector has grown significantly despite the absence of specific financial sector policies.

Microfinancial institutions (MFIs) differ from traditional banking institutions in several ways ( J. P. Morgan, 2009 ). MFIs emphasize both their financial profitability and their social impact (i.e., double bottom line). MFIs also have higher net interest rate margins compared to commercial banks. This is due to the relatively high interest rates charged to microfinance clients typically resulting from higher administrative expenses because of the location of clients, small transaction size, and frequent interaction with MFI staff. In 2006, the average worldwide microfinance lending rate stood at 24.8 percent ( J. P. Morgan, 2009 ). Furthermore, MFIs have typically had a stronger asset quality than mainstream banks in emerging markets, due to a good knowledge of customers and strong incentives for clients to pay and establish a good credit history ( J. P. Morgan, 2009 ).

Microfinancing has typically not been available for financing water supply and sanitation activities primarily because of a lack of awareness of the business case for water and sanitation projects. Water and sanitation projects become bankable when assets such as pumps, turbines, and solar panels are introduced. These assets provide collateral and the means for generating recurring income streams and fee-based services. Emphasized investment in distributed energy technologies for the poor combined with local currency lending mechanisms may flourish as the microfinancing markets mature and infrastructure spending increases.

Microfinancing mechanisms can serve those at the household and small community levels. Platz and Schroeder (2007) provided case studies in Africa and Latin America that describe how larger scale programs can be financed and implemented. The delivery of water and electricity to the poor is characterized by low levels of cost recovery and requires long-term financial investments. Full cost recovery in the least developed countries can be problematic, and targeted subsidies often are needed to finance large projects.

Although the current financial crisis is not expected to affect long-term investment in energy infrastructure projects, delays in bringing current projects to completion are expected ( IEA, 2008 ). Privatization projects in the water and sanitation sector have largely failed ( Bayliss and McKinley, 2007 ), and global private water investments in 2007 were low, at just $3.2 billion ( World Bank, 2008 ). Substantially more funding is needed to strengthen public sector services, and clean renewable technologies have the potential to attract new significant investment while offering a return on investment and societal benefits. Bringing these opportunities to fruition requires strong collaboration between the engineering, financial, and health sectors to ensure community acceptance and economic sustainability.

New Water and Sanitation Technologies

As was discussed previously, most research in the United States and elsewhere has focused on improving conventional infrastructure. In some cases, the impediments to improve existing technology have resulted in the development of new approaches to replace older technology. Examples of this, which have applications in developing countries, are membrane separations and UV disinfection. Membrane processes are advanced filters that are capable of removing particulate and, in some cases, dissolved contaminants of water. They are effective in the removal of bacteria and viruses and can also remove other contaminants depending on the fabrication of the membrane itself. Much of the most recent research has focused on reducing the pressure needed to drive water through the membrane, and considerable progress has been made in this area. Decreasing pressure results in lower energy needs and should allow for membrane treatment using some of the distributed power systems discussed previously. Small-scale household or community production of water for drinking and body contact using coupled energy production-membrane filtration units may represent an area of study.

UV disinfection has been an area of research to replace existing disinfection strategies (e.g., chlorination) that result in the formation of unwanted disinfection byproducts. Classic UV disinfection uses mercury vapor lamps, which are not likely to be used in the developing world due to cost, poor durability, energy consumption, and the potential effects of mercury wastes. Considerable technology development has been occurring in the area of light emitting diodes and other “lamps” that are far less energy consuming than traditional light bulbs. They also offer increased durability and longevity. The development of low power lamps that produce UV in a spectrum similar to a mercury vapor lamp would be ideal for use in the developing world to disinfect water, again coupled with a distributed energy source.

Microbial Fuel Cells

One promising technology for the treatment of human and animal wastes is microbial fuel cells (MFCs). While simple in design, MFCs harness the natural ability of bacteria to break down organic matter and create electricity directly. MFCs function with bacteria to oxidize organic matter (i.e., the electron donor) on the anode under anoxic conditions and transfer the electrons to a cathode through a wire. Oxidation of these recently fixed sources of organic carbon does not contribute net carbon dioxide to the atmosphere and, unlike hydrogen fuel cells, there is no need for extensive preprocessing of the fuel or for expensive catalysts ( Lovley, 2006 ). By converting biochemical to electrical energy, their most likely near-term application is as a method of producing energy from wastewater ( Logan and Regan, 2006 ). What currently is not known is how best to integrate MFC approaches in systems such as latrines or small-scale waste facilities. Electricity production from waste is an interesting possibility that may create a market for sanitation that currently is not in existence.

Geographic Information Sciences for Decision Makers

Geographic information sciences (GIS) combine remote sensing, geographic information systems, cartography, and surveying, interrelating with mathematics, and the physical, biological, and social sciences. It empowers researchers and decision makers to evaluate complex environmental systems and the interconnections with human health. New tools for modeling, predicting, and forecasting the water resources sustainability, quantity, and quality are being used in developing countries. The use of novel sensors, wireless and broadband technologies, high-performance computing, and real-time data assimilation is being promoted with the objective of better understanding the Earth’s water resources and related biogeochemical cycles; this goal could lead to better management of activities that impact human health ( Schnoor, 2008 ). Multidisciplinary innovations such as these provide a foundation for better decision making on global issues of water quality, water resources, and sanitation.

Nanomaterials Applications of nanoscience for water treatment are in the market and expanding (Hillie et al., 2007). They include

  • nanofiltration membranes for removal of salts and micropollutants, and for wastewater treatment;
  • use of Attapulgite clay, zeolite, and polymer filters, which can be manipulated on the nanoscale for greater control over pore size of filter membranes;
  • nanocatalysts and magnetic nanoparticles that will enable the use of heavily polluted water for drinking, sanitation, and irrigation; and
  • nanosensors for detection of chemical and biochemical contaminants.

The impact of nanotechnologies on human health is a growing research need. Risks and social issues associated with promoting advanced filtration techniques in developing countries need to be understood and communicated to promote transparency and adoption of the technologies.

Research Needs for a New Water and Sanitation Infrastructure Model

The development of a new water and sanitation infrastructure model requires multidisciplinary, systems-based thinking and innovations that vary from successful approaches adopted by developed nations. Advances and improvements in the necessary disciplines are occurring on a global scale; integrating the health, engineering, economic, political, technological, and social aspects for sustainable solutions for the world’s poor calls for research in the following subjects:

  • Development of robust and appropriate water technologies to create safe drinking water;
  • Development of robust and appropriate wastewater and dry sanitation technologies;
  • Technology transfer and development of markets for these technologies;
  • Development of best practices in watershed protection, water conservation, and sustainable energy systems for rural and urban populations;
  • Tailoring water and sanitation for microfinanced enterprises and investment banking institutions;
  • Scalability of innovative technologies for maximum impact;
  • Health and epidemiological concerns of a successful implementation; and
  • Outreach and education to improve transparency at all levels of government.


Kristof Bostoen, Ph.D., M.Sc.

London School of Hygiene and Tropical Medicine

Pete Kolsky, Ph.D.

The World Bank

Caroline Hunt, Ph.D.

Those who live in cities depend upon resources from outside city boundaries. Use of external water resources is one of the important ways a city affects, and is affected by, its surroundings. During rapid urban growth, these interactions become increasingly important for both the city and its environment.

Water flows back and forth between the natural environment and the urban community ( Figure 4-7 ). Water supply brings water from the broader environment into the community, while drainage and sewerage returns it to the ‘natural’ environment. Water in such transfers is never pure H 2 O, but is always mixed with other matter, as illustrated in Figure 4-7 . Often this ‘other matter’ includes pathogens (disease-causing organisms).

The water balance.

Whatever water comes into a community has to be returned to the natural environment. Even with recycling and storage, the outflow must more or less equal the inflow, or else flooding will occur. Despite this fairly obvious fact, efforts are frequently made to improve community water supply without improving drainage. If water is returned to the natural environment with chemical or biological pollution, the contamination does not always disappear or die off, but can return to threaten the health of the polluting community or that of one downstream.

This chapter examines issues related to water supply and sanitation services, which are of particular relevance to low-income communities. The second section of this chapter looks at health issues relating to water, while the third section examines the targets set by the international community for water and sanitation and the challenges regarding the achievements of these targets.

As problems of water shortages and pollution are transferred from the local to the broader environment, the challenge shifts from one of maintaining human health to one of preserving the integrity of life-support systems for future generations ( McGranahan et al, 2001 ). These transitions are well known and documented with regards to the water cycle.

The water cycle within the urban area, as illustrated in Figure 4-7 , occurs at each spatial scale of the city; for a given neighbourhood, the rest of the city is seen as the broader environment. These different subdivisions, or boundaries, often create institutional issues which in turn have an impact upon service quality and health; these are explored in the fourth section of the chapter.

How Water Supply, Sanitation and Hygiene Affect Health

Below, in the following two sub-sections is a description of two common models to describe the relationships between water supply, sanitation, hygiene and human health, as they are understood at present. The third sub-section refers to recent and forthcoming research in this field.

Classifications of Water-Related Infections

The first model has evolved from earlier work, grouping water-related infectious diseases by broad routes of transmission ( Feachem et al, 1977 ; White et al, 1972 ). The categories are defined by the types of intervention that can control morbidity and mortality, rather than by the biological taxonomy of the organisms that cause them. As such, this model has helped engineers and public health professionals to work together on practical control strategies ( Kolsky, 1993 ). A similar classification exists for excreta-related diseases ( Feachem et al, 1983a ) but has been less widely used. There are four categories in the Bradley-Feachem classification of water-related disease:

  • Faecal-oral (waterborne and waterwashed). These include infections that are transmitted by swallowing faecally contaminated matter (food and water) containing pathogens. They can be caused by lack of sufficient water to maintain personal and domestic hygiene as well as by drinking contaminated water. Diseases in this group include, among others, diarrhoeal diseases, typhoid, cholera and hepatitis A and E.
  • Strictly water-washed (skin and eye infections). These are conditions that are exacerbated by lack of water for washing and hygiene, but are not faecal-oral. These diseases are largely related to skin and eyes, such as scabies, trachoma and conjunctivitis.
  • Water-based aquatic intermediate host . Aquatic organisms such as snails act as hosts to parasites, which then infect humans either by being swallowed or through contact in water (e.g. by piercing the skin of those wading in the water). Diseases in this group include guinea worm and schistosomiasis.
  • Water-related insect vector . These diseases depend on insect vectors, such as mosquitoes and flies, which breed in or near water. They transmit disease to humans, for example, through bites. The diseases involved include malaria, filariasis, yellow fever, dengue and onchocerciasis (river blindness).

From the four categories in the Bradley-Feachem classification it becomes clear that interventions focused on water quantity have broader impact than those focused on water quality. Water quality only affects faecal-oral diseases, whereas quantity affects both faecal-oral and water washed diseases. The relative importance of water quantity and its quality will be discussed later in this chapter.

Diarrhoeal diseases, which are faecal-oral, are responsible for the greatest number of episodes of illness (morbidity) and deaths (mortality) worldwide, compared to any other single classification of water and sanitation-related disease. This is shown in Table 4-6 , based on data presented for World Health Organization (WHO) member states. It has been estimated that diarrhoeal disease represents 90 per cent of the health impact associated with water supply and sanitation ( White et al, 1972 ). Diarrhoeal diseases are estimated to kill around 1.8 million people every year worldwide ( WHO, 2004 ) of which the overwhelming majority is children. This toll is equivalent to 12 jumbo jet crashes every day or almost twice (1.9) the number of people who ‘died in the World Trade Center on the 11th of September 2001’ per day. There is some reason to believe that the number of deaths has fallen since the 1980s, possibly due to water and sanitation programmes and increased use of oral rehydration therapy ( Bern et al, 1992 ). However, it appears that the number of episodes of diarrhoeal disease has remained constant.

TABLE 4-6. Health Impacts of Water- and Sanitation-Related Diseases.

Health Impacts of Water- and Sanitation-Related Diseases.

Approximately 90 per cent of diarrhoeal disease cases are estimated to be attributable to environmental factors ( Murray and Lopez, 1996 ). Apart from water supply, sanitation and hygiene, diarrhoeal disease is also associated with a number of other risk factors including age, malnutrition, lack of breastfeeding, and seasonality.

The F-Diagram

A second model is the F-diagram, depicted by Wagner and Lanoix (1958) ( Figure 4-8 ), which has been widely used as a model of faecal-oral disease transmission. Unless faeces are isolated from potential contact with humans, animals and insects, pathogens may be carried on unwashed hands, in contaminated water or food, or via flies and other insects on to further human hosts. The first way to stop or reduce transmission is to ensure the safe disposal of faeces, through sanitation. Safe excreta disposal and washing hands following defecation is referred to as ‘the first barrier’ and considered the most important health intervention, as it keeps faecal pathogens out of the living environment. Children’s faeces in particular are known to contain a high load of pathogenic organisms, such as Ascaris and Trichuris, but are also least likely to be safely disposed of ( Cairncross, 1989 ; Kolsky, 1993 ). The secondary barriers to faecal-oral disease transmission protect people from whatever faecal contamination of the environment is present. These are based on hygienic practices, such as washing hands before handling food, fly control, safe food storage and the use of footwear.

F-diagram. SOURCE: After Wagner and Lanoix (1958). With permission from the World Health Organization.

The F-diagram graphically presents multiple routes of transmission. A single type of pathogen may be transmitted by several of these routes, and the population at risk may be vulnerable to many different pathogens, which may favour different routes. Numerous commentators have advocated integrated measures to control diarrhoeal disease by combating multiple routes of transmission ( Lewin et al, 1996 ; Curtis et al, 2000a ). The greater the range of interventions, the greater the chance in successfully reducing diarrhoeal disease transmission. The F-diagram also shows that while water quality only affects one route, the quantity of water available for personal and domestic hygiene affects almost all routes.

Following the discovery in the 19th century of the undeniable role that water quality played in the epidemics of cholera and typhoid, there was a natural focus on the improvement of drinking water quality. This focus produced dramatic results in the reduction of waterborne epidemics. The F-diagram clearly shows that this would be the case where water contamination is the main route of transmission.

Where routes other than water consumption are more important for disease transmission, however, improving water quality will have far less effect. While waterborne epidemics are dramatic and alarming surprises, the sad truth is that the everyday endemic (non-epidemic) toll of faecal-oral disease is far, far higher, and most of the latter seems to be transmitted through routes other than water. While improving water quality does not necessarily affect endemic transmission, increasing the quantities of water available to improve personal and domestic hygiene can have a greater effect on this unacceptable toll ( Cairncross, 1995 ). Most health benefits will be obtained from large amounts of water of a good quality. But if resources are scarce, public health professionals generally recognize the greater importance of access to water in quantity for hygiene, compared with the quality of that water ( Esrey et al, 1985 , 1991 ). Unfortunately, in practice, the main efforts in ‘water and sanitation for low-income areas’ are often still directed towards the improvement of the water quality of the public water supply, rather than improving access by poor households, and thus the quantity of water that those households can use. The beneficiaries of such efforts are more likely to be people who already have access to water than people with no access. Sanitation and hygiene promotion are even lower priorities in practice, although the principles of the F-diagram suggest that they should have equal or higher priority ( Curtis et al, 2000b ).

Recent and Forthcoming Research

Most studies of the impact of water quality have been based upon water quality measurements at the source or collection point. It is known however, that the degree of faecal contamination of water increases during transport to the household ( Clasen and Bastable, 2003 ). There is also increasing evidence that improving water quality at the point of use has a positive health impact ( Conroy et al, 2001 ; Iijima et al, 2001 ; Fewtrell et al, 2005 ; Clasen, 2006 ). This is regarded by some as an exception to the dominant paradigm ( Clasen and Cairncross, 2004 ). While data support health benefits for people that have at least 15 litres of water per capita per day there are reasons to believe that benefits are reduced when access levels to water are lower ( Clasen, 2006 ). However, at this time not enough data are available to substantiate this ( Clasen, 2006 ). Systematic reviews and meta-analyses, such as those of the Cochrane Library infectious diseases group ( Clasen et al, 2004 ) and field research will be needed to clarify these new findings and examine if these are in conflict with the current paradigm.

What Does All This Mean?

These models clarify the complex relationships between water, sanitation, hygiene behaviour and health. For example, good hygiene is more important in low-income areas where environmental exposure to pathogens is greater; residents of relatively clean areas can (and often do!) get away with lower standards of hygiene. Those who practise poor hygiene are certainly at greater risk than those who practise good hygiene, even in relatively clean environments. Water quantity is generally more important than water quality, because increased quantities of water promote good hygiene, and can prevent faecal-oral transmission by a number of different routes; increased quantities of water also reduce skin and eye infections. Only when drinking water is the main source of infection will water quality be more important than quantity. This is rarely the case where diarrhoea is endemic.

This means that in most cases within an urban setting, water distribution (access to water in quantity) is more important than public water treatment (its quality) until a certain relatively high level of environmental hygiene has been reached. Water treatment at the point of use seems to give health benefits, but it is not clear if a certain level of access to water is required to profit from such an approach. Finally, the quantity of water which people can actually use is vitally dependent upon access, as shown by Figure 4-10 ; the issue of access will be further explored in the following section.


Relation between water consumption and time involved in water collection. SOURCE: Reprinted from Cairncross and Feachem (1993) with permission from John Wiley (more...)

Access to Improved Sanitation and Water Sources

‘Water for life’, the 2005 global water and sanitation assessment, contains the most up-to-date coverage data for most of the countries in the world ( WHO/UNICEF, 2005 ). Since the Global Assessment 2000 Report (GA2000) ( WHO/UNICEF, 2000 ) the United Nations (UN) Joint Monitoring Programme (JMP) does not report on ‘safe’ drinking water and ‘adequate’ sanitation. Instead, access to ‘improved’ water supply and sanitation technology types are now reported (see Table 4-7 ). This change in terminology reflects both past misrepresentation, and future uncertainty, in judging and defining services as safe in terms of human health. According to the report, over 2.6 billion people worldwide are without access to improved sanitation and over 1.1 billion do not have access to improved water supply. While many people have gained access since 2000, the number without access has remained the same ( WHO/UNICEF, 2006 ).

TABLE 4-7. Water Supply and Sanitation Technologies Considered to Be Improved and Unimproved in WHO/UNICEF Global Assessment 2000.

Water Supply and Sanitation Technologies Considered to Be Improved and Unimproved in WHO/UNICEF Global Assessment 2000.

Asia and Africa have the lowest levels of service coverage. In Asia, less than half the region’s population have access to adequate sanitation. When comparing individual countries, the African region has the highest proportion of countries with less than 50 per cent water supply and sanitation coverage. In all regions, apart from North America, rural coverage is lower than urban coverage for both water supply and sanitation.

The Global Assessment 2000 presented the status of the sector using consumer-based data for the first time. These data were drawn from large nationally representative household sample surveys, such as the United States Agency for International Development’s (USAID) Demographic and Health Survey (DHS) and United Nations Children’s Fund’s (UNICEF) Multiple Indicator Cluster Survey (MICS) and national census data. The GA 2000 thus presented a better baseline for future targets than previous reports. The WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation (JMP), which published the GA 2000, continues to update these data to monitor progress to the Millennium Development Goal Target for water and sanitation. The latest report to date is Meeting the MDG Drinking Water and Sanitation Target ( WHO/UNICEF, 2006 ), which is available together with current data at the JMP website ( www.wssinfo.org ).

Targets For the Future

The UN Millennium Summit adopted the target of halving the proportion of people who are unable to reach, or to afford safe drinking water by the year 2015. The 2002 UN World Summit on Sustainable Development (WSSD) in Johannesburg has adopted the same target for access to sanitation facilities and the application of hygiene practices.

The compilation of the GA2000 has greatly improved data quality, using survey data. However, there is still a need to standardize survey outcomes to make results comparable. Figure 4-9 shows the typical scatter of results of the different surveys over the last 20 years for access to improved water in urban Niger. The variation in results is less for urban than for rural areas. Variations between different surveys are also less for household connections than for other improved access, which is probably a reflection of the interest of the water utility in keeping track of its customers and the ease of defining this way of delivering water to households.

Variation on access in various surveys. NOTE: HC = household connections. SOURCE: UNICEF. NOTE: The original source of this figure is http://www.childinfo.org/files/NER_wat.pdf.

Urban populations in Asia and Africa are predicted to almost double over the next 30 years. Against this trend, meeting the International Development Target of halving the proportion of those unserved by water by 2015 would mean providing water services to more than 300,000 additional people every day over the next 15 years. Halving the number unserved by sanitation requires provision of services to over 400,000 additional people per day.

Limitations to the Use of Routine Data Sources

The use of existing surveys such as the DHS, MICS and national censuses, as in the GA 2000, has the advantage of being cost efficient, but it also has its drawbacks. These surveys have usually been designed to give a picture of ‘the average household’ on a national level and sometimes on a regional scale. Designed for other purposes, they cannot provide sector-specific (water, sanitation and hygiene) data at a local level that can be used for project implementation, evaluation and local decision making.

Large surveys such as the DHS require major administrative and organizational work, which means that they are unlikely to take place in countries or areas experiencing conflict or natural disasters.

To achieve better measurements in the field of water, sanitation and health practices there is a need for a simple standardized sample technique and a standardized set of indicators. Moreover, not only the collection techniques, but the interpretation and the type and extent of analyses need to be agreed upon if results are to be compared worldwide.

Access to Improved Services and Its Relation with Health

The level and type of service both have the potential to influence health. However, numerous other factors, which influence the use and nature of the service, also affect health risk, in some cases to a greater extent than the level or type of service itself. These factors include: access to, and use of services; system maintenance; treatment; seasonality; water sources; and pathogenspecific factors. Poverty is very often a key variable behind many of the factors listed above, most notably access to services.

The improvement of water supply and sanitation has attracted particular interest in reducing diarrhoeal disease ( Feachem et al, 1983b ; Esrey et al, 1985 ). These environmental improvements, together with improvements in living standards, played a major role in reducing diarrhoea rates and controlling endemic typhoid and cholera in Europe and North America between 1860 and 1940 ( Esrey et al, 1985 ). Similar effects were anticipated from equivalent improvements in low income countries, and these expectations contributed to the declaration of the Water Decade. In 1977, the UN Water Conference at Mar del Plata set up an ‘International Drinking Water Supply and Sanitation Decade’ for 1981–1990. Its aim was to make access to clean drinking water available across the world.

Although improving access to water and sanitation projects improves health ( Feachem et al, 1983b ; Esrey et al, 1985 ), it is difficult to link these achieved health benefits back to specific improvements. Many attempts have been made to measure the health impact from water supply, sanitation and, more recently, hygiene practices. Even attempts under the supervision of eminent specialists to measure the health impacts of water supplies and sanitation have produced almost useless or meaningless results ( Cairncross, 1999 ). Health impact studies are, for that reason, not an operational tool for project evaluation or ‘fine tuning’ of interventions ( Cairncross, 1990 ). This led various organizations like the WHO and the World Bank to adopt the Minimum Evaluation Procedure ( WHO, 1983 ), which concentrates on measuring functioning and use of services rather than measuring their health impacts ( World Bank, 1976 ; Briscoe et al, 1985 ; Esrey et al, 1985 ; Cairncross, 1999 ).

While the health benefits of increased water quantity are known, they are difficult to measure and to attribute back to increases in supply. There is, for example, a clear but counterintuitive relation between the time needed to collect water and the amount of water collected ( Figure 4-10 ). It is known that an increase in water consumption increases the water used for hygiene, which improves health. So, one might expect that reducing the time it takes to secure daily supplies to below 30 minutes would have a beneficial health impact. However, a reduction of the collection time of between 30 and 3 minutes will actually have little impact. Those who spend less than 3 minutes for water collection usually have a house-hold connection. Note also that collection time includes queuing time, which can be significant in areas with relatively closely spaced taps with intermittent service, or in areas that are serving large populations. In various parts of Africa, reports show that while distance to source diminished or stayed the same, collection times for water increased ( Thompson et al, 2002 ; UN-Habitat, 2003 ).

While the main ways water, sanitation and health practices relate to health are broadly understood in theory, their real-world interactions are far more complex. However, increasing access to water and sanitation is clearly recognized as leading to health benefits, and new international targets have been set for that reason. Although improved access might improve health, it is methodologically extremely difficult to attribute improvements in health exclusively to specific interventions, on a project-by-project basis. This makes health impact an unsuitable outcome measure for project evaluation. The current indicators based on level and type of service also have their limitations. Better sector specific indicators and survey tools need to be developed.

Boundary Issues and the Urban Environment

Differing perspectives.

Figure 4-11 shows the urban environment from the point of view of the householder. The home is at the centre, and is the householder’s first priority for environmental management. If the householder is able to maintain the home in a relatively clean and pleasant condition, the next priority becomes the surrounding street (peri-domestic). Local and informal lane arrangements may, for example, develop among neighbourhoods to ensure that rubbish does not pile up in the street, or clog drains. If the home and street are relatively clean, then some citizens will be concerned about the state of the environment in their larger neighbourhood (ward); when these problems are addressed, attention can then be focused on the rest of the city, and eventually, on the environment outside the city. It is natural that the focus of environmental concern spreads further outwards as the problems at each of the smaller (inner) scales are resolved.


Scales of the urban environment, as seen by a householder. SOURCE: Kolsky (1996) unpublished lecture notes, London School of Hygiene and Tropical Medicine.

It turns out that the householder’s perspective and priorities are similar to those that emerge from a public health perspective. As most of the victims of poor environmental health are children under five, it makes sense to focus attention on where they spend the most time, which is at home. We have also seen that water access at the household scale is critical to increasing the quantity of water used to improve hygiene. The construction of public toilets half a kilometre from the house may offer limited improvement in convenience and dignity of some adults, but will not significantly improve the health of children in the community, who will rarely if ever use such services. Improving the quality of river water by controlling the quality of the wastewater discharge may be of ecological benefit, but it makes no difference to a household’s health unless that improvement is translated into improved drinking water quality at the household scale. The public health priority for environmental improvement thus becomes the household, followed by its immediate neighbourhood.

These differing scales of the urban environment are reflected in the structure of environmental service provision. Water supply, sewerage, storm drainage and solid waste management all involve the flow of mass between the individual household and the larger environment. Figure 4-12 shows the superimposition of a water supply system upon the scales of the environment shown in Figure 4-11 , and similar sketches can be prepared for the other environmental services such as sewage disposal and solid waste management. Table 4-8 also shows the physical infrastructure associated with each level of aggregation.


Scales of water supply infrastructure matched to the urban environment. SOURCE: Kolsky (2006) unpublished lecture notes, London School of Hygiene and Tropical Medicine.

TABLE 4-8. Scales of the Urban Environment and Water, Sewerage and Drainage and Solid Waste-Related Infrastructure Issues.

Scales of the Urban Environment and Water, Sewerage and Drainage and Solid Waste-Related Infrastructure Issues.

The perspective of the service provider (e.g. the sewerage utility, the water supply engineer, and so on) is often different from that of the householder and public health specialist. They will look at the same system, but usually focus on different concerns, as shown in Figure 4-13 . The highest priority of the water engineer is often the intake and central treatment works. Their attitude is, if this link of the chain fails, all the rest will fail.


Water supply infrastructure and priorities, as seen by technical professionals. SOURCE: Kolsky (2006) unpublished lecture notes, London School of Hygiene and Tropical Medicine.

Construction of centralized works often involves substantial amounts of financial capital and technical sophistication, both of which contribute to the professional standing of the individuals involved. Primary mains are the second priority after the central works, because of the relatively large impact of the failure or inadequacy of these links in the chain. While central pipes are more expensive per metre, the majority of the cost in the distribution system is tied up in the large number of small outlying lines. Individual street mains and house connections are often at the periphery of the technical professional’s vision. Indeed, in many cases the ‘outermost rings’ of the technical professional are virtually ignored; water is provided to a public tap to serve a neighbourhood, and what happens to the water after that is not the practical concern of the utility. This focus on centralized works is even less appropriate for sanitation infrastructure, where large amounts of resources may easily be spent upon centralized waste treatment works of marginal public health benefit in comparison with the provision of basic household access.

Unfortunately, the poor live in the outermost ‘marginal’ rings. These ‘rings’ often represent very clearly definable neighbourhoods which are rarely laid out for service provision, have dubious tenure relationships, and are thus not a priority for service delivery. They are therefore easily excluded, yet it is here where the battle for urban public health is won or lost.

Boundaries and Their Impact on Services

We define a boundary as the limit beyond which an individual or group feels no responsibility. Boundaries can be marked by physical, legal, bureaucratic, psychological or customary limits. They can include formal district boundaries in rural areas, and ward boundaries in urban areas; they may also be as informal, but also as strong, as the sense of community around a courtyard or square.

The use of a subjective word like ‘feels’ in the definition seems odd, but the reason for its use is a pragmatic one. The world is filled with legal or administrative boundaries without practical meaning because those within the boundary do not feel, directly or indirectly, the consequences of their actions.

Boundaries permit the breakdown of complex problems into simpler parts, and the corresponding delegation of responsibilities and tasks. By limiting responsibilities, they become manageable, both for the person delegating and for the person performing the task. It is difficult to be responsible for everything, but we can accept responsibility within given boundaries.

Classification of Boundary Problems

While boundaries are a useful political, social and administrative device, they are not without drawbacks. There are, at least, four related categories of problems arising from boundaries.

Complete externalities When the damage of my actions to others does not affect me, I have no incentive to change my behaviour. This situation is known to economists as an ‘externality’, and in this case, explains why wastewater treatment always lags behind drinking water as a community priority. Drinking water affects the members of a community directly, so it is in their interest to take appropriate action to ensure its quality. Sewage effluent quality affects only downstream users; upstream community members causing the problem have no direct interest in resolving it for their downstream neighbours. Government action is often required to solve such problems. Although environmental pollution is the classic example of such a boundary problem, there are also administrative examples of externalities, as described below.

Partial externalities In some cases, I do care about the damage I cause outside my boundaries, but if most of that damage will occur in any event, why should I change my behaviour? Hardin describes this in his classic paper The Tragedy of the Commons ( Hardin, 1968 ). The paper examines the behaviour of individual shepherds responsible for grazing on common land. Collectively, it is clear that they would be better off with fewer sheep grazing on the commons, because in the long term, overgrazing will destroy the resource. Individually, however, each shepherd is better off grazing as many of his sheep on the land as possible; after all, if he restrains his behaviour, the commons will still be destroyed by others, and he will have sacrificed in vain. Some form of social arrangement needs to be worked out, or else the commons will be finished. The difficulty of working out such social arrangements, complete with effective sanctions against those who violate them, lies at the heart of many environmental and social problems. Rubbish dumping in urban slums often falls within this category.

Badly drawn boundaries In some cases, things could work better if boundaries were simply redrawn. Engineers often refer to drainage networks and other urban infrastructure as trees. Such trees have large ‘trunk’ mains, and smaller ‘branch’ lines, and the image of a tree effectively conveys the notion of many smaller entities combining into a larger one. Most of the length of a drainage network, and most of the cost, lies in the many small branches rather than in the trunk line. While trunk lines are certainly more expensive per metre, the total cost of a network is dominated by the smaller branches at a smaller unit cost making up the outer branches. Such lines are often technically simple and individually not expensive; added up they represent the main cost of the network.

Traditionally, centralized authorities have taken responsibility for entire drainage networks on the grounds that all drains up to the individual property boundaries are public goods. This model was developed in the industrialized world and has served quite well there. Alternative approaches, however, have emerged in the cities of the developing world. Municipal authorities there are devolving the responsibility for these smaller lines to local community groups or non-governmental organizations (NGOs). This can be done because small branches are technically simple, and can be managed better by closer supervision within the community than by the distant municipal authorities. This does not mean that central authority should disengage totally in regards to compliance and appropriateness of these activities.

Redrawing boundaries in the water sector is not a new idea; the regional water authorities in Britain ( Okun, 1978 ) are another practical demonstration of the benefits of more rational boundary definition. The environmental economics literature ( Ruff, 1970 ) stresses the need to draw boundaries so that benefits and costs of activities are felt by those who take the action, thus reducing the boundary problem of externalities.

The category of badly drawn boundaries includes also cases where there are gaps between boundaries (so no group feels responsible), and cases where boundaries overlap (where more groups claim the same responsibility or authority).

Boundaries as barriers Movement of ideas and resources across boundaries is always more difficult than within boundaries. For example, at the start of the International Drinking Water Supply and Sanitation Decade, a need was recognized to integrate the services of water supply and ‘sanitation’, used here as a euphemism for excreta disposal. This made sense both in conceptual public health terms (as both are involved in the spread of faecal-oral disease) and in practical engineering terms where water-based sewerage is the main means of excreta disposal, and thus depends directly on the water supply. Communications between these services improved as intended, under the new boundaries.

Redrawing the boundaries around water supply and excreta disposal, however, caused the nominal separation of sanitary sewerage and surface water drainage even where these systems are physically interconnected. In the same street separate crews clean these ‘separate’ drains, requiring separate transport and equipment at different times. Because of the new administrative boundaries, these crews no longer communicate, and no longer share access to the same resources.

Other types of boundary create other communications problems in water, sanitation and other sectors. Because external support agencies do not wish to become entangled in an open-yended [ sic ] commitment to paying recurrent costs, they have traditionally limited their involvement to capital investment. This means that both international and local resources are drawn to the investment sector, to the neglect of the operational aspects. Recently created municipal development authorities created in recent decades are responsible for municipal investment, but not for the day-to-day maintenance of the infrastructure they develop. There is often a strong feeling among those running the infrastructure that those planning and designing it don’t understand basic operational reality.

Boundaries define the problem considered by those with responsibilities within these same boundaries. There is, for example, an administrative boundary between street sweeping and drain maintenance. The street sweeper’s boundary extends only to keeping the street clean, so sweeping sediment and debris into a drain is seen as perfectly acceptable. Similarly, the drain cleaner’s boundary extends only to keeping the drain clean, so that emptying debris onto the street for subsequent pick-up by the solid waste department is also seen as acceptable. If the street sweeper returns before the solid waste department picks up the debris, then it will be swept back into the drain, thus achieving the environmental goal of perfect recycling! In this case, the real issue is ‘solid waste management’ which cuts across the pre-existing boundaries of street sweepers and drain cleaners.

Public and Private Domains as a Special Example of Boundary Problems

For a long time public health engineering has been focused on public domains to bring health improvements to deprived populations. This has involved construction of large-scale urban water and sanitation infrastructure. A spatial model of disease transmission in public and private domains illustrates the move away from this traditional, engineering approach to public health ( Cairncross et al, 1996 ). Diseases transmitted on the household level have to be dealt with via interventions that reach the household level. This puts more emphasis on private health at household level and the need to understand decisions made and actions taken at household level and their relation to environmental health. The private domain is distinctly different from the public domain in which the intervention of a public authority is required to prevent disease transmission. Some of these spatial problems relating to this model have been discussed in the paragraphs above. This model acknowledges the importance of household practices and behaviour without ignoring the public domain.

Many studies have investigated the links between public water supplies and household contamination of stored water ( Kirchhoff et al, 1985 ; Deb et al, 1986 ; Jonnalagadda and Bhat, 1995 ; Mintz et al, 1995 ; Jagals et al, 1997 ; Quick et al, 1999 ). Findings have been rather mixed. There is a growing consensus that diarrhoeal disease pathogens originating within the home, as found in household water storage vessels, are less of a threat to household health than pathogens found in source water supplies (e.g. from public wells) ( VanDerslice and Briscoe, 1993 ). There appears to be degrees of immunity to pathogens commonly found within the household. These complexities are acknowledged and explored within the public-private domain model. The recent literature on point-of-use treatment of drinking water ( Conroy et al, 2001 ; Hellard et al, 2001 ; Iijima 2001 ; Fewtrell et al, 2005 ; Clasen, 2006 ) seems to indicate that there are health benefits from improving drinking water quality at the household level. Further research will be required to determine if this is true for households with limited access to water.

Several studies have looked at the impact of interventions at household scale when the neighbourhood is contaminated with faeces ( Cairncross et al, 1996 ). Others have logically argued that interventions should be targeted at those most in need. It has been suggested that children who are not breast-fed are more susceptible to diarrhoeal disease and as such may benefit more from water supply and sanitation interventions than breast-fed infants ( Esrey et al, 1985 , 1991 ). The logistical difficulties in carrying out this approach may, however, make it impracticable.

Water Stress at Global and Household Scales, a Boundary Point of View

At the International Conference on Freshwater in Bonn in 2001, water scarcity was attributed to growing demand and increasing pollution and waste of freshwater sources. There is confusion between water stress at the household and regional scales. Regional water stress is sometimes portrayed as the major determinant of households’ access to adequate water and sanitation, as well as the prevalence of water-related diseases ( UN-Habitat, 2003 ). The amounts of water required to meet basic needs are relatively modest. It is estimated that on a worldwide basis, agriculture accounts for about 69 per cent of annual water withdrawals; industry about 23 per cent, and domestic use about 8 percent ( Hinrichsen et al, 1997 ). In Africa the percentage of domestic water use is estimated to be 7 per cent, while in Asia only 6 per cent ( Hinrichsen et al, 1997 ).

The most common measure for water stress at a national level is the Falkenmark indicator ( Falkenmark et al, 1989 ) which estimates the amount of freshwater available per capita per year. Benchmark values for the Falkenmark indicator are less than 1700m 3 per capita per year, which indicates water stress, while less than 1000m 3 per capita per year indicates severe water stress. In Figure 4-14 the relationship between urban water access, national water stress and national gross domestic product (GDP) per capita is shown based on data from the United Nations Environment Programme (UNEP) Data Compendium ( UNEP, 2002 ). The figure shows the counter-intuitive relationship that water stressed nations have a larger proportion of their populations with access to water than those nations not considered ‘water stressed’. Figure 4-14 shows that it is an erroneous over-simplification to extrapolate freshwater stress at a national level to imply similar reduced access to water at the household level, regardless of the GDP per capita. Apart from a variety of other possible explanations, it is crucial to bear in mind that domestic drinking water supply and sanitation make up a very small fraction of any nation’s demand for water resources.


Relationship between urban water access, national water stress, and national GDP per capita. SOURCE: UN-Habitat (2003).

Solutions to Boundary Problems?

Boundaries at different levels can be helpful in identifying problems within environmental services. Water provision by a utility to the neighbourhood level, but not to the individual household, invites the creation of an informal sector that may or may not operate as an extortionate cartel. The interface between differing levels can also be critical where the volumes in and out of the interface do not match. In the case of solid waste management, waste may be carried to a neighbourhood bin, but not picked up from that bin by the municipal service. Local drains that serve one neighbourhood by flooding their neighbour can also reflect a failure to consider the whole system. So service provision must extend to the true ‘end user’ in the outer boundaries to ensure that the goals of access are really achieved.

Solutions to boundary problems are rarely obvious, or else sound trite. Nevertheless, two strategies emerge:

  • Careful definition of boundaries, with flexible mechanisms for redefining them . Redrawing boundaries along hydrological rather than political lines has worked well in some European watersheds ( Okun, 1978 ). This has resulted in the advocacy for an integral holistic and transboundary management system of river basins ( BHS, 1998 ). Unforeseen problems will, however, still arise, and there must be a reasonable way to refine or redraw the boundaries in the light of experience.
  • Good mechanisms to identify and confront cross - boundary problems. Identification of cross-boundary problems is not so difficult, especially if a group is given the task of finding out, for example, why government services don’t perform properly. Resolution of inter-departmental conflicts, however, is a timeless management problem ( Handy, 1985 ). ‘Interdepartmental Task Forces’ can be effective, or simply a sop offered in order to appear to be doing something about the problem.
The problems of the poor, are suffered by the poor, and dealt with by the poor, The problems of the rich, are suffered by the public, and dealt with by the Government. Marianne Kjellen

Scale of the Problem

At present, an estimated 2.6 billion people lack access to improved sanitation and 1.1 billion people lack access to improved water supply. While there is substantial uncertainty about the definition or measurement of these terms, there is no doubt that a very large proportion of the human race does not have what public health authorities could accept as reasonable access to water and sanitation, and thus to the prerequisites for better hygiene. The toll of this inadequate access is high in terms of health, time, money, comfort and dignity. More than 2 million people, mainly children, die every year from diarrhoeal disease, equivalent to a jumbo jet crash every two hours. Unfortunately, this burden falls almost exclusively upon the poor, and most of it could be avoided with promotion of better water, sanitation and hygiene services.

Water, Sanitation, Hygiene and Health

It has been well established for nearly 30 years that the quantity of water that people use for personal and domestic hygiene is more important in maintaining health than the quality of the water they drink. While recent epidemiology on household water treatment justifies greater attention to this intervention, the implications for the public utility remain the same: that physical access to nearby waterpoints is a key aspect of service provision. The importance of excreta disposal and hygiene practices such as handwashing are obvious from the models mentioned and clearly visualized in the F-diagram.

Access to Services

The practical interrelationship between water, sanitation and hygiene in relation to health are far more complex than the theoretical links. This makes health impacts difficult to attribute to improved services, and the measurement of health impacts unsuitable for routine project evaluation. Increasing the access to water and sanitation is widely recognized as leading to health improvements, and new targets have been set by the international community to improve worldwide morbidity and mortality.

So far, the type of technology used at household level has been used as the main proxy for access and health impact. More careful consideration shows that this idea has severe limitations, and that better indicators of access to environmental health services need to be developed. Reasonable access to services such as ‘improved’ water is a complex idea with many facets, encompassing not just water quality, but also its quantity, cost, operational reliability, seasonal availability and collection time and effort. Measuring access to improved services, although essential, is not straightforward. To measure progress on these targets, more powerful and sector specific survey tools will need to be developed, along with the will to use them.

Domestic water consumption increases greatly with convenient and affordable water delivery to the household, reflecting the importance of collection time as a determinant in the amount of water used. These types of proxy indicators are easier to measure than the health impacts obtained by these improved services.

Boundaries, Scales of Environmental Challenges and Access

Before they can be expanded, services have to become more efficient. Institutional boundaries are central to many environmental problems, and are closely linked to the economist’s idea of ‘externalities’, which occur when individuals or agencies are unaffected by the consequences of their actions. In many cases, these boundaries are regarded as immutable, because of institutional resistance to change. Identifying, acknowledging and addressing the various problems associated with institutional boundaries requires time, energy and goodwill. Successful models can evolve only after trial and error, careful monitoring and evaluation and honest documentation of both success and failure.

Environmental health operates on a variety of levels. One simple spatial division is between public and domestic domains of infection. The most vulnerable groups in society in terms of mortality and morbidity (children and the elderly) spend most of their time in the domestic domain. Recent epidemiology of disease transmission and hygiene has stressed the need to create conditions in which households can manage the domestic domain more effectively, through increased water use, household sanitation and improved personal hygiene.

Regional water stress is sometimes portrayed as the major determinant of households’ access to adequate water and sanitation. Household consumption in the world is below 8 per cent of the global water use, and this chapter shows that household access to water in urban areas is, on average, higher in water-stressed nations than in countries where there is no water stress, according to the Falkenmark indicator.

This chapter has also presented a range of scales in which to examine environmental challenges, varying from that of the household up through street, ward and city levels. These scales often reflect their own boundary problems, as when the capacity to collect waste at one point is not equal to the capacity to remove it to the next stage. Householders, public health experts, and infrastructure professionals view these environmental scales differently. Both householders and public health experts see the household as the natural focus for environmental service provision, while infrastructure professionals tend to focus, for good and bad reasons, upon the centralized infrastructure (treatment works, centralized pumping, and so on). Environmental service provision is a chain, and, like all chains, is only as strong as its weakest link. Improvements in environmental health infrastructure will only be significant if they lead to changes at the household level. This public health reality underscores the need for improved access to environmental services at the household level. We need reliable measures of such access if we are to improve it, and the need for better practical indicators of access to environmental services is thus critical for the sector at this time.

The findings, interpretations and conclusions expressed in this article are entirely those of the authors, and should not be attributed to the World Bank.


Sharon H. Hrynkow, Ph.D. 7

National Institutes of Health

A wave of enthusiasm for “social entrepreneurship” is sweeping across university campuses in the United States, the not-for-profit or citizen sector, and the private sector. While the concepts underpinning social entrepreneurship are not new, having been introduced as a discipline nearly 30 years ago, the vigor with which theses concepts are being applied to tackle tough societal problems is new and increasingly sophisticated. And, the numbers of individuals, nongovernmental organizations (NGOs), and for-profit entities applying the principles are only increasing.

At the same time, the health and medical research community in the United States recognizes that new approaches in the research arena are needed in order to translate basic science knowledge into public health practice. As stated in the 2009 Budget Request Congressional Justification for the National Institutes of Health (NIH), “health care costs will not be tempered unless we accelerate the discovery of transformative ways of practicing medicine—which can only happen through research” ( NIH, 2008 ). The principles and successes of social entrepreneurship, which introduce new and sometimes disruptive ideas and completely new delivery mechanisms, bear examination as nations work to lower health care costs.

This paper examines four strategies to provide clean water or sanitation in resource-poor settings. Each case is examined through the lens of social entrepreneurship and with a view toward identifying lessons learned to inform future efforts in the medical research arena. Examples are not delineated in depth but were chosen to offer illustrative examples. Clean water and sanitation was selected as the topic area in part because of the enormous toll in death, disability, and human suffering exacted due to poor water quality and sanitation: nearly 10 percent of the global burden of disease could be prevented by improving water, sanitation, and hygiene, and in the 32 worst-affected countries, this figure would be 15 percent ( Prüss-Üstün, 2008 ).

What Is a Social Entrepreneur?

Much has been written about social entrepreneurs and the movement in the past two decades, and there have admittedly been many champions. Bill Drayton, founder of Ashoka, the first and one of the best known organizations that invests in social entrepreneurs, states that “There is nothing more powerful than a new idea in the hands of a true social entrepreneur” ( Ashoka, 2009a ). But what is a social entrepreneur? Most agree that social entrepreneurs are “individuals with innovative solutions to society’s most pressing social problems” ( Ashoka, 2009b ). Among the qualities that typify a social entrepreneur, they are determined, ambitious, and persistent; they persuade societies to take new leaps; and they are visionaries and ultimate realists at the same time. In his book How to Change the World: Social Entrepreneurs and the Power of New Ideas , David Bornstein examines the social entrepreneurship wave and offers perspectives on the qualities that typify these innovative leaders: willingness to self-correct, share credit, break free of established structures, cross disciplinary boundaries, work quietly, and with strong ethical impetus ( Bornstein, 2004 ).

Examples of social entrepreneurs are many and they can be found through time. While not necessarily viewed as social entrepreneurs at the time, many well-known historical figures have worked tirelessly to change minds and systems. Florence Nightingale established nursing as a profession, while at the same time transforming how hospitals operate. John Muir fought to preserve and conserve nature’s beauty by changing the way people experienced it, leading to the establishment of the U.S. National Park System and helping to found The Sierra Club. More recently, Nobel Prize winner Muhammad Yunnus showed that lending small amounts of money to impoverished people, against all instincts of traditional banks, can spur sustainable small businesses, lifting families out of hopelessness through enterprise and full economic citizenship, rather than through charity or government services. These visionaries represent only a small sampling of true social entrepreneurs.

Many foundations have realized the role of social entrepreneurs as mass mobilizers of citizens and as good value for the initial investment, leveraging dollars with the promise of high impact. There are now more than a dozen major grant-making organizations devoted specifically to the support of social entrepreneurs, in addition to Ashoka’s focus on institution building and transformation of the entire citizen sector in entrepreneurial directions. Efforts to provide sustainable energy and clean water in remote villages, to conserve rainforests, to ensure quality education for all, to dismantle landmines, and to teach children living in poverty how to become self-sufficient are just some of the challenges being supported by social entrepreneur organizations. Efforts in the not-for-profit sector are complemented by those in the private sector, which has also taken up the mantle of social entrepreneurship. Bill Gates, Jr., is in every sense a business entrepreneur, but through the Bill and Melinda Gates Foundation he is working for the global public good through a range of innovative, large-scale programs. Furthermore, the for-profit sector has increasingly incorporated concepts of social entrepreneurship into corporate strategies: FastCompany and others track the social entrepreneurial movement embedded within the private sector. 8 Between 1990 and 2005, FastCompany trends show that for-profit companies involved in social entrepreneurship grew from about a dozen to more than 30. And more sophisticated approaches toward social entrepreneurship are being developed and tested. For example, Ashoka is now developing new approaches for combining multiple social entrepreneurs and innovative ideas in creative forums in order to refine and accelerate the most promising ideas and to spark entirely new insights based on the dynamic engagement of multiple entrepreneurs working together.

Clean Water and Sanitation—Consideration of Two Social Entrepreneurial Approaches

Boxes 4-2 and 4-3 provide snapshots of two Ashoka Fellows in Indonesia, each of whom approached the clean water challenge differently. 9 Both cases represent operational strategies related to collection and use of water data or to provision and marketing of sanitation services. In one case, river water was collected and analyzed from multiple locations across the span of several years to show the burden of pollution to nearby inhabitants. The volume of credible data collected by ordinary citizens, including school children, in a methodical and persistent way was used as a platform to engage journalists and policy makers, leading to reform. The second example focuses on delivery of sanitation measures in an urban slum. Using a business model and training for a local family, the program led to sustained used of toilet facilities for a small fee. Anecdotal evidence suggests that health was improved due to reductions of raw sewage in the streets.

Communities Develop Evidence Base for Water Quality Policies. Ashoka Fellow Prigi Arasandi works in 51 Indonesian villages with the goal of cleaning the water of the Surabaya River, a large drainage from the interior (more...)

Community Leadership to Improve Sanitation. Ashoka Fellow Hamzah Harum Al’Rasyid works in poor urban areas in Indonesia to provide “community-based sanitation centers.” Mr. Al’Rasyid works with (more...)

There are many strengths in the social entrepreneur approach as currently deployed in both cases in Indonesia. First, both models depend on a firm understanding of local communities, cultures, and norms. Ashoka Fellows, who themselves are from the same countries in which they conduct their work, spend time with community members to define project parameters, gain trust, and learn essential insights for successful implementation. Second, both models turn on its head the expectation of whose job it is to solve social problems, engaging community members as “experts,” not just for the purpose of consultation but to invest community members with decision-making authority. Project development is informed by the community experts and then executed in close partnership with them. Both programs valued community members from the start, to be consulted and respected and vested with responsibility instead of treating them as uninformed future beneficiaries. At least in part because of this approach, important cobenefits were realized: The citizen base developed feelings of ownership for the river and its quality in the first case, which led to further direct river stewardship actions and to mobilization as a political constituency when needed. In the second case, cobenefits included awareness of and pride in, and sometimes substantial revenue from, the health benefits of good sanitation measures. Mr. Al’Rasyid’s project, along with a handful of other social entrepreneurs in other countries, 10 also shows that very poor people are willing to pay to use community toilets. Because of the delivery methodology used, locals report feelings of ownership and interest in helping to keep the facilities clean and well maintained.

Third, solid data is the foundation of both programs. In Mr. Arisandi’s work, schools along the river were identified and teachers were trained to teach children about hydrology, water use and sources, and environmental connectedness through classroom work and field trips. This was complemented by additional outreach to those not associated with schools. Indeed, one of the foundations to the success of the whole effort was in convincing citizens, often uneducated adults or children, to rigorously test water quality at more than 50 sites for several years and in a way which is credible (using bioindicators). With large volumes of credible data, efforts to engage policy makers were facilitated. And, not incidentally, the process of collecting those data from the citizen base also created an important political constituency that then became influential in the public policy process.

Fourth, in the case of the river clean-up, the engagement of journalists to help spread information and awareness about the effort was an integral and successful component. Mr. Arisandi provided weekly information updates to 14 journalists who then collaborated with him on pieces for a range of outlets. Such outreach paved the way for policy maker involvement, leading directly to new laws requiring the monitoring of the river’s water quality.

Finally, both cases point to the benefits of systems thinking. What changed in each case was not so much the data collected or the service provided but rather the ways in which the business was conducted. This comprehensive approach places the effort on a broader backdrop of activity, thereby integrating it more fully into the fabric of the community. It successfully puts the financial, educational, and other incentives directly in front of the people whose behavior needs to change in order to achieve the goals. Furthermore, once the work is understood in this way, both systemic models can be replicated with appropriate modification in other locales.

Rigorous evaluation of the programs has not yet been completed. While anecdotal evidence points to success, evaluation may provide insights that could further strengthen the programs and suggest future actions.

Clean Water—Consideration of Two Health Research Approaches

Many of the qualities ascribed to social entrepreneurs may be attributed to those health researchers who have worked over long periods to achieve success on a single goal. As social entrepreneurs, medical researchers can best be described as “driven,” “willing to work across confines of fields and geography,” and having “long-term vision,” as just some examples of the similarities. The work of two such “driven” researchers is outlined in Boxes 4-4 and 4-5 . Dr. Rita Colwell has contributed to the knowledge base to understand the life cycle of the pathogenic agent for cholera, Vibrio cholerae , and its copepod vector. Over decades, she and her colleagues showed that a variety of characteristics of water, including temperature and salinity, affect the spread of the cholera bacterium. She also showed that the copepod vector could be effectively filtered out using readily available sari cloth in poor villages, leading to reduced illness.

A Multidisciplinary Approach to Prevent Cholera. Dr. Rita Colwell, now at the University of Maryland, and her colleagues have studied transmission dynamics of cholera in the Bangladeshi villages for more (more...)

Basic and Behavioral Science to Reduce Arsenic Exposures. Dr. Joseph Graziano and his colleagues have worked over many years to understand the dose-response relationships between exposure to arsenic and (more...)

Dr. Joseph Graziano and his colleagues provided critical insights into the health impacts of arsenic, including the molecular mechanisms underlying disease. Recent work ( Gamble et al., 2006 ) has led to interventional studies focused on folic acid as a means to assist subsets of the population in metabolizing arsenic to inactive forms. Moving from the bench back to the field, Dr. Graziano and his colleague Dr. Alexander van Green worked with a community-based effort to localize wells with high- or low-arsenic levels. With thousands of participants and attendant data, it was found that within a single village both high- and low-arsenic wells can exist. More recent studies have shown that, even when presented with information on arsenic impacts, other factors come into play when determining whether to use water from high- or low-arsenic wells. While roughly half of residents with high-arsenic wells switched to low-arsenic wells, others did not, largely because the distances to the safer wells were too long. The “durability” of well-switching over time is not clear, and other options such as the provision of a deep, low-arsenic community well appear to have much greater promise as a longer term solution.

Both of these examples show the impact and import of sustained hypothesis-driven research efforts over time. With the dedicated support and vision of these medical researchers over decades, new knowledge was gained to underpin intervention efforts related to cholera and arsenic-related disease. Both examples also show the ability of the researchers to engage communities as part of the interventional research. In the case of the folded sari intervention for cholera, the community played a leadership role in ensuring that the interventional pilot study was conducted. Some in the research community were concerned that the pilot would fail since it was believed that men would not drink water that had been filtered through sari cloth. It was discovered, however, that men had already been using the same sari cloth as part of the process for their local production of fermented drinks. In this case, the community voice allowed an intervention to be tested that might otherwise have been left off the drawing board.

In terms of scale-up and long-term adoption of the interventions, both examples illustrate the challenges in moving from a basic research understanding of a problem to a populations-based intervention strategy. In the case of the folded sari intervention, despite its clear effectiveness in filtering out the cholera vector, and demonstrated reduction in illness after filtering, uptake of the intervention was sustainable in that filtration continued after the project was completed, but the details, namely, the number of folds effective for filtering out the plankton were not adhered to in every case. Similarly, there was a lack of permanent switching to the use of low-arsenic wells. Two challenges present themselves. First, the incomplete uptake of the intervention may be due to a lack of local reinforcement of the links between clean water and better health within the community. Continued efforts to raise awareness are needed. Second, given the number of donors working in the region, questions may also be raised as to why the simple sari intervention or well-switching interventions were not incorporated into larger development programs. Placing these simple interventions into broader development perspective bears examination.

The global burden of illness and death directly related to lack of clean water and sanitation demands that we consider all possible strategies. As various groups take on this challenge, new ideas and programs will be put in place. By merging the best features of different approaches, even better strategies may surface.

This paper juxtaposes two approaches to improving clean water and sanitation in resource-poor settings. The social entrepreneur approach focuses on delivery of interventions or gathering of information for policy purposes. The medical research approach focuses on understanding the links between toxins or microbes and attendant ill health, then working to mitigate exposures. Both approaches have yielded immense data sets and new knowledge that has led to improved health.

There are similarities and differences between the approaches. Some of the key features of the two approaches are outlined in Table 4-9 . Closer examination of two features in particular provide insights into potential future actions. First, how community members were included in the work had an impact on the overall outcomes. The social entrepreneurship model embraces community perspectives as true experts, thereby ensuring that voices heard from the earliest of stages are those from ultimate beneficiaries, and that the work witnesses and subsequently accounts for the incentives faced by those whose social behavior it seeks to change. Interventions based on community involvement had a high degree of uptake. This particular approach leads to feelings of “ownership” of the work, driven by educational or economic incentives, and efforts to ensure its sustainability. The medical research model includes important elements of community engagement, particularly during data gathering for pilot efforts and as part of educational efforts related to scale-up of interventions. Long-term sustainability of effective interventions might improve if community engagement were viewed through another lens. Increased community involvement, including consults with local social entrepreneurs, may lead to more effective and long-lasting uptake of interventions, both geographically and on a long-term timescale. One can easily imagine the impact that the folded sari intervention might have in the hands of a social entrepreneur. By the same token, linking information about low- and high-arsenic wells in particular villages to motivated community members or social entrepreneurs might yield new insights on critical operational aspects.

TABLE 4-9. Key Features of the Two Approaches on Clean Water and Sanitation.

Key Features of the Two Approaches on Clean Water and Sanitation.

Second, the type of funding for the two approaches dictates in many ways the range of activities that may be supported. Medical research grants supported by governments tend to limit activities to those that lead to new knowledge about population-based health risks, outcomes due to exposures, including cellular and subcellular responses, and effectiveness of clinical interventions, for example. The development of policy-relevant data has not been a traditional focus of medical research grants. Given the priorities, funding cycles tend to be on the four- to five-year range. The researchers described in the present text pieced together long-term funding strategies over time using multiple sources. This is in contrast to the Ashoka model, which provides support with relatively few conditions for a critical phase of start-up activity intended to lead to population-based policy or intervention results and intended to get the entrepreneurial work to a solid enough footing that more traditional organizations will step in to support and/or replicate. Looking at the two models, it could be speculated that some medical researchers would benefit from a granting system that provided longer term support, perhaps on a 10-year cycle, which included a mid-term review timed to moving basic science knowledge into practice. Such an approach could capture the best elements of both systems.

Increasing the dialogue between the medical research community and the social entrepreneur community would likely enhance operations on both sides. Formal and informal means could be identified for exchange of views and expertise. Such exchanges might lead to exciting new actions and programs. Possible mechanisms to bolster communication are many and include, first, nominations of social entrepreneurs to public slots on governmental research agency advisory boards and, second, linking social entrepreneurs on the ground with researchers funded through medical research councils or other national or international grant-making bodies. In the latter case, ambassadors, aid mission directors, and other senior government officials, including military, agricultural, and health attachés, could play a role in brokering and facilitating the exchange of ideas between the two communities on the ground. Third, efforts to raise awareness within the medical research community about the social entrepreneurship movement through conferences and lectures would spark ideas for action, particularly from those already attuned to this wave—the next generation. Finally, medical researchers, public health professionals, students, and others should be made aware of new tools such as Changemakers.com, a partnership supported by Ashoka, the Robert Wood Johnson Foundation, and the Global Water Challenge. Through that tool, ideas and entrepreneurial approaches to providing clean water and other seemingly intractable problems, including strengthening of health-care systems, have been identified. Encouraging deposits of good ideas and mining the site for good ideas would be useful undertakings. This would in fact be in line with the next-generation vision of Ashoka, “Everyone is a Changemaker.”

  • Acknowledgments

I am very grateful to Rita Colwell and Joseph Graziano for allowing me to tell their stories in this context, and also for their generosity in reviewing and editing the draft paper. David Strelneck of Ashoka provided invaluable insights at every step of the way. He and former Ashoka colleague Carol Grodzins reviewed the draft and made extremely helpful suggestions. Appreciation also goes to NIH colleagues Patricia Mabry (OBSSR) and Claudia Thompson (NIEHS) for their guidance and perspectives early on in the framing of this effort.

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The Palgrave Encyclopedia of Global Security Studies pp 1–7 Cite as

Water-Borne Diseases

  • Kinga Szálkai 4  
  • Living reference work entry
  • First Online: 29 April 2019

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In the field of health security, adequate, safe, and accessible water supplies and satisfactory sanitation are of key importance. “Pure water is the world’s first and foremost medicine,” says a Slovakian proverb, and the sentence has a similarly important meaning in its reversed form: contaminated water as the transmitter of water-borne illnesses is one of the leading causes of death globally.

Between 1980 and 2015, the average annual number of deaths due to water unsafe for human health amounted to 780,000 – dwarfing the number of deaths as a consequence of natural disasters (63,000) and in conflicts (75,000) (Ligtvoet et al. 2018 , p. 38). According to the estimations of the World Health Organization (WHO, see chapter “World Health Organization (WHO)” ), the overall number of people who die in diarrheal diseases per year totals 1.5 million, among whom 502,000 people die of diseases related to contaminated drinking water. Cases related to the lack of sanitation and hand...

  • Health security
  • Contamination
  • Water-borne
  • Microorganisms
  • Bradley categorization
  • Climate change
  • Inequalities

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Bartram, J., & Hunter, P. (2015). Bradley classification of disease transmission routes for water-related hazards. In J. Bartram et al. (Eds.), Routledge handbook of water and health (pp. 20–37). London/New York: Routledge.

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Singh, P. P., & Sharma, V. (2014). Prelude. In P. P. Singh & V. Sharma (Eds.), Water and health (pp. vii–viii). New Delhi: Springer.

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Eötvös Loránd University, Budapest, Hungary

Kinga Szálkai

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Péter Marton

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Szálkai, K. (2019). Water-Borne Diseases. In: Romaniuk, S., Thapa, M., Marton, P. (eds) The Palgrave Encyclopedia of Global Security Studies. Palgrave Macmillan, Cham. https://doi.org/10.1007/978-3-319-74336-3_562-1

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DOI : https://doi.org/10.1007/978-3-319-74336-3_562-1

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essay on water borne diseases

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One health and disease: water-borne disease, water-borne disease, general water-borne disease information, geographic distribution.

Water-borne diseases are found worldwide.

Hosts and Transmission

Water-borne disease is found in lakes or streams that have been infected by animal or human feces or urine. Many water-borne diseases are also found in contaminated soil, food, and surfaces, or can be passed from person to person.

Drinking untreated water from springs, streams, or lakes while hiking or camping in the parks could put you at risk for infection.

Signs and Symptoms

Water-borne diseases can cause symptoms in humans and animals. Symptoms in humans typically occur within 10 days of infection and can include:

  • Stomach aches or pain
  • Dehydration
  • Nausea and vomiting
  • Weight loss

Prevention and Control

You can lower your risk of getting water-borne illness while visiting the parks by:

  • Filtering and disinfecting or boiling fresh water before drinking. Water should be boiled longer at higher elevations.
  • Washing your hands before handling or eating food and after using the toilet. Alcohol-based hand sanitizers can be used when soap and water isn't available but are not a substitute for hand washing.
  • Cleaning up after pets and keeping them on a leash.
  • Viewing animals in the wild from a safe distance and not handling wild animal feces.

Testing and Treatment

Some animals and humans with water-borne illness can get better on their own without treatment. Drinking lots of fluids can help prevent dehydration from diarrhea.

If you think you have the symptoms of water-borne disease and have been exposed to potentially contaminated soil, food, or water, consult your healthcare provider.

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One Health and Water-Borne Disease

Water-borne diseases.


Cryptosporidium, which causes the diarrheal disease cryptosporidiosis or “Crypto”, is a tiny parasite that infects humans and animals worldwide.

Cryptosporidium is found in water, soil, and food, as well as on surfaces that have been contaminated by feces of an infected person or animal.

The major reservoirs for Cryptosporidium in humans are humans, cattle, and sheep. It is also found in lakes or streams that have been infected by human or animal feces. Animals and humans with cryptosporidiosis often get better on their own without treatment in a few days. Giardiasis

Giardia is a tiny parasite that is found worldwide in water, soil, and food as well as on surfaces that have been contaminated by feces of an infected person or animal. Giardiasis is the most common water-borne disease in the United States.

Humans are the major reservoir for human infections, although other strains from animals may infect humans occasionally. It is spread from person-to-person by hand-to-mouth transfer of cysts from the feces of an infected individual.

Giardia is also found in lakes or streams that have been infected by human or animal feces. Humans with Giardia often get better on their own within a few weeks. Leptospirosis

Leptospirosis is a bacterial zoonotic disease that affects humans and animals, most often occurring in tropical or subtropical regions.

While most infected individuals do not show any signs or symptoms, the bacterial disease can cause a wide range of symptoms, similar to other water-borne diseases but also including fever, chills, headache, jaundice, and red eyes.

Without treatment the disease can lead to kidney damage, meningitis, liver failure, and respiratory distress.

Leptospira is spread through the urine of infected animals and is associated with recreational water sports that take place in contaminated lakes and rivers.

Salmonellosis is a bacterial infection that is usually caused by eating foods contaminated with animal feces. The bacteria can also contaminate water.

These are often foods from animals, such as beef, poultry, milk, or eggs; however, any food may become contaminated. Food may also become contaminated if an infected food handler fails to wash their hands with soap after using the bathroom. Additionally, Salmonella can also be found in pet feces, particularly reptiles and young birds.

Always wash your hands immediately after handling animals and also after contact with raw meat or poultry. Other prevention methods include cooking poultry, beef, and eggs thoroughly and not consuming foods containing raw eggs, or raw (unpasteurized) milk. E. coli E. coli are a large and diverse group of bacteria. While most strains are harmless, others can make you sick with diarrhea, stomach cramps, and vomiting. Symptoms are usually resolved within 5–7 days.

E. coli infections can be prevented by thoroughly washing hands after using the bathroom, after changing diapers and before preparing or eating food.

Related Links

For more information from the Center for Disease Control, visit their website, here . Learn more about the One Health concept and in practice, here . Learn more about the Biological Resources Division by exploring their organization page, here .

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Waterborne Disease in the United States

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The United States has one of the safest drinking water supplies in the world. Yet, the water we use for drinking, swimming, and even cooling high-rise buildings can be safer. About 7.2 million Americans get sick every year from diseases spread through water.

CDC’s first estimates of the impact of waterborne disease in the United States cover illnesses tied to all types of water use. They detail how many waterborne diseases, emergency department visits, hospitalizations, and deaths occur every year, and what these cost our healthcare system. This type of information is referred to as the burden of waterborne disease.

While the United States has made tremendous strides in preventing waterborne disease over the last century, these new estimates provide a better understanding of the waterborne disease challenges we face in the 21 st century. CDC, policymakers, related industries (for example, owners of large buildings and recreational water facilities), the public health community, and others can use this information to prioritize next steps in protecting the public from waterborne disease.

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