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Water and sanitation 

Water and sanitation
Chapter:
Water and sanitation
Author(s):

Thomas Clasen

DOI:
10.1093/med/9780199661756.003.0011
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date: 04 August 2020

Introduction to water and sanitation

Background

Safe drinking water and sanitary waste disposal are among the most fundamental of public health interventions. When readers of the British Medical Journal were asked in 2006 to name the ‘greatest medical advance’ since 1840, their top choice was clean drinking water and waste disposal, beating antibiotics, anaesthesia, vaccines, and germ theory (Ferriman 2007). Deaths from diarrhoeal diseases and typhoid fever showed dramatic declines in Europe and North America when cities and towns began filtering and chlorinating their water and safely disposing of human and animal excreta (Cutler and Miller 2005). The field of epidemiology arguably has its origins in John Snow’s nineteenth-century mapping of cholera cases and the eventual intervention at London’s Broad Street pump that demonstrated waterborne transmission of the disease.

While diseases associated with poor water and sanitation are now comparatively unknown in higher-income countries, they still impose a heavy burden elsewhere, especially among young children, the infirm, the poor, the immunocompromised, and the displaced. The World Health Organization (WHO) estimates that diarrhoeal diseases alone are responsible for 1.5 million deaths annually, including 760,000 among children under 5 years (WHO 2013). Diarrhoea is the third leading cause of deaths of children <5 years in low-income countries, accounting for 11% of the overall disease burden in this population. Improvements in water, sanitation, and hygiene have the potential to reduce this disease burden by an estimated 58% (Prüss-Ustün et al. 2014). As discussed below, poor water and sanitation is also associated with a heavy disease burden from malnutrition, parasite and worm infection, trachoma, and environmental enteropathy. Water and sanitation are not only a matter of public health, but also of poverty, equity, and justice (United Nations Development Programme 2007). Because they are less likely to have access to safe water and sanitation, the poor bear most of the burden of water-related diseases, driving them further into poverty through lost productivity and expenditure on treatment (Blakley et al. 2005). Time spent in collecting water from distant sources and the inability to procure sufficient quantities of water for irrigating crops, watering animals, and carrying out other productive activities aggravates poverty. While urban-rural disparities in water and sanitation coverage are well documented (WHO and UNICEF 2014), a recent analysis of sub-Saharan Africa also demonstrated important geographic inequalities in use of water and sanitation previously hidden within national statistics (Pullan et al. 2014). These results confirm the need for targeted policies and metrics that reach these marginalized populations. (Pickering and Davis 2012). Inadequate water and sanitation are also associated with poor school attendance (Hutton et al. 2007). For these and other reasons, water and sanitation have been recognized as a fundamental human right (United Nations 2010).

Nevertheless, basic water security and sanitation still elude much of the world’s population living in low-income countries. An estimated 748 million people lack improved access to water supplies; hundreds of millions more rely on water that is unsafe for drinking (WHO and UNICEF 2014). An estimated 2.5 billion people—40 per cent of the world’s population—lack access to improved sanitation; more than 1 billion of those still practise open defecation. Coverage is lowest in developing regions, where people are most vulnerable to infection and disease. In sub-Saharan Africa, improved water and sanitation coverage is just 63 per cent and 30 per cent, respectively. Rural areas also lag behind their urban counterparts. By the end of 2011, 83 per cent of the population without access to an improved drinking-water source lived in rural areas. If current trends continue, more than half of the rural population will still be without sanitation coverage in 2015, and more than 700 million mainly poor rural dwellers will still lack improved water (WHO and UNICEF 2014).

The shortfall in water and sanitation coverage is not the result of a failure to recognize the need or declare goals at the highest international levels. The 1977 Mar del Plata Declaration by the United Nations (UN) expressed the goal of providing safe water and sanitation for all by 1990, launching the Water and Sanitation Decade (1981–1990) (Cairncross 1992). In 1990, the UN renewed the call and extended the deadline to the end of the century. The UN Millennium Development Goals (MDGs) call for halving, by 2015, the portion of the population without sustainable access to safe drinking water or basic sanitation (United Nations 2000). As the research described in this chapter suggests, such coverage would not only advance the environmental security targets under MDG 7, but also make contributions to reducing poverty (MDG 1), increasing primary education (MDG 2), promoting gender equality (MDG 3), reducing child mortality (MDG 4), and combating major diseases (MDG 6). In a further effort to attract attention to this deficit and additional priority to the sector, the UN General Assembly declared 2005–2015 as the Decade for Action, Water for Life (WHO and UNICEF 2005), and 2008 as the International Year of Sanitation. Proposals for post-2015 goals call for universal access to drinking water at home, schools, and clinics, greater progress on sanitation coverage, and improved equity in access (WHO and UNICEF 2014).

Traditionally, much of the work in water and sanitation has been undertaken by engineers and has consisted of infrastructural improvements. Low-cost community- and household-based interventions, such as protected wells, boreholes, and communal stand pipes for improved water supplies, and various types of latrines, septic tanks, and composting systems for improved sanitation, have been largely conceived by and constructed with the assistance of engineers. There are numerous books, manuals, and other resources that describe these systems in detail, including Cairncross and Feachem (1993), the UK Department of International Development (1998), Davis and Lambert (2002), the quarterly Waterlines, and the World Bank Water and Sanitation Programme (WSP) ‘Field Notes’ (World Bank n.d.). Readers are encouraged to refer to such sources for details on the design, installation, and operation of such systems, technology innovations, and the programmatic challenges associated with achieving widespread use on a sustained basis.

This chapter focuses solely on the public health issues concerning water and sanitation. After introducing some basic terminology, it begins by describing the diseases associated with inadequate water and sanitation and their contribution to the overall burden of disease. It then presents evidence of the effectiveness of water and sanitation interventions to prevent such diseases, the economic implications (especially cost-effectiveness and cost–benefits) of such interventions, and some of the other non-health benefits associated therewith. Recent and emerging developments in water, sanitation, and health are then discussed, along with some issues relevant to water and sanitation interventions. The chapter closes with a discussion of some of the continuing challenges in water and sanitation.

Terminology

At the outset, it is useful to understand some of the terminology used in describing the diseases, transmission routes, and interventions associated with the water and sanitation sectors. Water-related diseases are sometimes classified according to their disease transmission routes as waterborne (ingested in drinking water), water-washed (associated with inadequate supplies of water for proper personal hygiene), water-based (transmitted through an aquatic invertebrate host), or linked to a water-related vector (involving an insect vector breeding in or near water) (White et al. 1972). Most waterborne organisms that are human pathogens colonize the gut of humans and certain other mammals and are transmitted through the faecal–oral route. The transmission of common waterborne diseases can thus be interrupted by improvements in sanitation (excreta disposal), personal hygiene (especially hand washing with soap), and microbiological water quality, while those that are water-washed are impacted by improvements in water supplies (quantity and access) for personal hygiene. Improving water supplies can also help prevent water-based diseases (such as schistosomiasis and dracunculiasis) by reducing the need to enter infected water bodies.

The term ‘sanitation’ is vague and has multiple meanings. Within the public health sector two definitions are used. Under the broader definition, sanitation extends to the process whereby people demand, effect, and sustain a hygienic and healthy environment for themselves. This definition could include safe food production, solid waste management, industrial waste, animal waste, control of chemicals, environmental pollution, storm water drainage, wastewater disposal, human settlements, personal and domestic hygiene, vector and vermin control, occupational health and safety, mining and quarrying, port health, and disposal of the dead. A second definition is more specific, extending only to the process of separating humans from their excreta. This chapter uses this second, more specific definition and regards sanitation as a system in which excreta is: (1) collected safely and with dignity, (2) transported to a suitable location, (3) treated or contained to eliminate pathogenicity, and (4) reused and/or discharged to the environment.

The MDG targets for water and sanitation are expressed in terms of sustainable access to safe drinking water and of basic sanitation. The water target has been interpreted as ‘sufficient drinking water of acceptable quality as well as sufficient quantity of water for hygienic purposes’ (UN Millennium Project 2005). Basic sanitation, in turn, has been defined as ‘the lowest-cost option for securing sustainable access to safe, hygienic, and convenient facilities and services for excreta and sewage disposal that provide privacy and dignity, while at the same time ensuring a clean and healthy living environment both at home and in the neighbourhood of users’ (UN Millennium Project 2005). Progress toward the MDGs, however, is measured with reference to the Joint Monitoring Programme (JMP) that adopts an indicator approach based on facilities or level of service. For water supplies, the JMP distinguishes only between improved water supplies (piped-in tap water, public tap/standpipe, borehole/tubewell, protected well/spring, rainwater harvesting), and unimproved water supplies (surface water, unprotected well/spring, tankered water, bottled water) (WHO and UNICEF 2013). Improved sanitation includes a private flush or pour-flush toilet or latrine connected to a piped sewer system or septic system, simple pit latrine with slab, ventilated improved pit (VIP) latrine, or composting toilet; unimproved sanitation includes any other flush or pour-flush latrine, open pit latrine, bucket latrine, hanging latrine, any public or shared facility, or open defecation (WHO and UNICEF 2014). Some of these definitions are being reconsidered in the context of developing a set of post-MDG water and sanitation targets (WHO and UNICEF 2014).

Burden of disease

General

Poor water and sanitation are associated with a variety of infectious diseases transmitted through various pathways by helminths, protozoa, bacteria, and viruses. Table 2.6.1 summarizes the most important of these diseases, their transmission routes, aetiological agents, and epidemiological significance. Some of these diseases also contribute to malnutrition, a separate cause of substantial morbidity and mortality that is not reflected in the direct burden of disease figures cited in this chapter (Black et al. 2003).

Table 2.6.1 Principal infectious diseases, disease agents, transmission routes, and annual morbidity and mortality related to poor water and sanitation

Disease

Aetiological agent

Transmission

Infected1 (millions)

Mortality1 (thousands)

Diarrhoea (dysentery, cholera)

    Virus

  • Rotavirus

Faecal–oral

4000 (annual morbidity)

1400–1800

    Bacteria

  • Escherichia coli (ETEC)

  • Shigella spp.

  • Salmonella spp.

  • Vibrio spp.

  • Campylobacter sp.

Faecal–oral

    Protozoa

  • Giardia lambia

  • Cryptosporidium parvum

  • Entamoeba histolytica

Faecal–oral

Schistosomiasis

  • Schistosoma haematobium

  • S. mansoni

  • S. japonicum

Penetration through skin exposed to contaminated freshwater

207

15–280

Ascariasis

Ascaris lumbricoides

Faecal–oral

1221–1472

3–60

Trichuriasis

Trichuris trichuria

Faecal–oral

759–1050

3–10

Hookworm infection

Necator americanus

Penetration through skin exposed to faecally-contaminated soil

740–1300

3–65

Ancylostoma duodenale

Faecal–oral

Typhoid and paratyphoid fever

Salmonella spp.

Faecal–oral

26

216

Trachoma

Chlamydia trachomatis

  • Fingers

  • Clothing

  • Eye-seeking flies (Musca sorbens)

  • Coughing/sneezing

  • Blind from trachoma: 1.3

  • Active trachoma: 40

  • Trachiasis: 8.2

Note: 1 estimates vary according to method.

Morbidity and mortality estimates for diarrhoeal disease: data from World Health Organization and UNICEF, Progress on Sanitation and Drinking Water: 2013 Update, World Health Organization and UNICEF Joint Monitoring Programme on Water and Sanitation, New York, USA, Copyright © 2013.

Schistosomiasis and soil-transmitted helminth infections (STH) (ascariasis, trichuriasis, hookworm): data from

Lustigman et al., A research agenda for helminth diseases of humans: the problem of helminthiases, PLoS Neglected Tropical Diseases, Volume 6, Issue 4, e1582, Copyright © 2012 Lustigman et al.

Typhoid and paratyphoid: data from Crump et al., The global burden of typhoid fever, Bulletin of the World Health Organization, Volume 82, Number 5, pp. 346–53, Copyright © 2004.

Trachoma figures: data from Burton MJ and Mabey DC, The global burden of trachoma: a review, PLoS Neglected Tropical Diseases, Volume 3, Issue 10, e460, Copyright © 2009 Burton, Mabey.

Certain diseases associated with water are not addressed in this chapter. First, in addition to microbial agents, water is a medium for the transmission of chemical pathogens, including arsenic and other metals, fluoride, nitrates, and volatile organic compounds (including pesticides and herbicides). Accordingly, WHO guidelines and many national water standards establish maximum allowable limits for such chemicals (WHO 2012). However, except for arsenicosis and fluoridosis, which are especially serious in focal areas in Asia and parts of Africa, most of these contaminants represent hazards to health only over the longer term. Second, although improvements in water supplies (to discourage contact with water) and point-of-use water treatment (with filters) are important interventions in preventing dracunculiasis (Cairncross et al. 2002), efforts to control Guinea worm infection have been largely successful and the disease is now of public health interest in limited areas. Finally, this chapter does not address a variety of diseases associated with waterborne pathogens, such as poliomyelitis and hepatitis A and E, which are controlled mainly by vaccines and other non-environmental measures (Leclerc et al. 2002).

Diarrhoeal diseases

Diarrhoeal diseases represent the leading cause of mortality and morbidity associated with unsafe drinking water and poor sanitation. For those infected with the human immunodeficiency virus (HIV) or who have developed acquired immune deficiency syndrome (AIDS), diarrhoea can be prolonged, severe, and life-threatening (Hayes et al. 2003). Diarrhoea is characterized by stools of decreased consistency and increased number. The clinical symptoms and course of the disease vary greatly with the age, nutritional and immune status, and the pathogen (Black and Lanata 1995). Most cases resolve within a week, though a small percentage continue for 2 weeks or more and are characterized as ‘persistent’ diarrhoea. Dysentery is a diarrhoeal disease defined by the presence of blood in the liquid stools. Though epidemic diarrhoea such as cholera and shigellosis (bacillary dysentery) are well-known risks, particularly in emergency settings, their global health significance is small compared to endemic diarrhoea (Hunter 1997). The immediate threat from diarrhoea is dehydration, a loss of fluids and electrolytes. Thus, the widespread promotion of oral rehydration therapy (ORT) has significantly reduced the case-fatality rate associated with the disease. Such improvements in case management, however, have not reduced morbidity, which is estimated at 4 billion cases annually (Kosek et al. 2003). And since diarrhoeal diseases inhibit normal ingestion of foods and adsorption of nutrients, continued high morbidity is an important cause of malnutrition, leading to impaired physical growth and cognitive function, reduced resistance to infection, and potentially long-term gastrointestinal disorders.

The infectious agents associated with diarrhoeal disease are transmitted chiefly through the faecal–oral route (Leclerc et al. 2002). Safe excreta disposal thus represents a primary barrier that should contribute to the prevention of indirect transmission via food, water, hands, fomites, and mechanical vectors (flies) (Fig. 2.6.1). A wide variety of bacterial, viral, and protozoan pathogens excreted in the faeces of humans and animals are known to cause diarrhoea. While the importance of individual pathogens varies among settings, seasons, and conditions, a recent multicountry study has shed important light on the principal aetiological agents responsible for much of the disease burden in Africa and South Asia (Kotloff et al. 2013). Investigators found that most attributable cases of moderate-to-severe diarrhoea were due to four pathogens: rotavirus, Cryptosporidium, enterotoxigenic Escherichia coli producing heat-stable toxin (ST-ETEC) and Shigella. Aeromonas, Vibrio cholerae O1, and Campylobacter jejuni were also important in selected sites. They reported that the odds of dying during follow-up were 8.5 times higher in patients with moderate-to-severe diarrhoea than in controls (odd ratio (OR) 8.5; 95 per cent confidence interval (CI) 5.8–12.5, p < 0.0001) and that 88 per cent of deaths occurred during the first 2 years of life. Pathogens associated with increased risk of case death were ST-ETEC (hazard ratio (HR) 1.9; 95 per cent CI: 0.99–3.5) and typical enteropathogenic E. coli (HR 2.6; 95 per cent CI: 1.6–4.1) in infants aged 0–11 months, and Cryptosporidium (HR 2.3; 95 per cent CI: 1.3–4.3) in toddlers aged 12–23 months. Although diarrhoea is also associated with the ingestion of metals, nitrates, organics, and other chemicals, the burden of disease arising from such exposure is small relative to infectious diarrhoea (Hunter 1997).


Fig. 2.6.1 The F-diagram.

Fig. 2.6.1 The F-diagram.

Reproduced with permission from Wagner, EG and Lanois, JN, Excreta disposal for rural areas and small communities. WHO monograph series No.39, World Health Organization, Geneva, Switzerland, Copyright © 1958.

Schistosomiasis

Schistosomiasis affects 200 million people all over the world, with Schistosoma haematobium and S. mansoni being the most common species. The schistosomiasis life cycle involves contamination of freshwater by eggs carrying excreta and urine and an intermediate host, a freshwater snail. Larvae released in the water infect humans by penetrating through the skin. Parasites develop and migrate to the intestines and bladder where thousands of eggs are produced. Like other intestinal helminths, schistosomes are associated with impaired physical and mental development and anaemia. Furthermore, schistosomiasis may cause serious damage to the bladder and intestine walls as a result of parasite egg entrapment within tissues. Chronic infection with S. haematobium has been associated with increased risk of bladder cancer in adulthood (Gryssels et al. 2006).

Soil-transmitted helminth infection

More than 2 billion of the world’s population are infected with soil-transmitted helminths. A disproportionate burden of helminthiasis occurs in marginalized, low-income, and resource-constrained regions of the world, largely in developing areas of sub-Saharan Africa, Asia, and the Americas (Lustigman et al. 2012). About 300 million people suffer from heavy worm load and related severe morbidity (deSilva et al. 2003). Ascaris lumbricoides, Trichuris trichuria, and hookworm (Ancylostoma duodenale and Necator americanus) are the most prevalent intestinal helminths. Transmission occurs via ingestion of eggs present in faecally contaminated soil, or via penetration of the larvae through the skin. Children are particularly vulnerable to chronic and heavy infections, which result in malnutrition, stunted growth, reduced physical fitness, and impaired cognitive development (Stephenson et al. 2000). Hookworm infection is an important cause of anaemia, not only in children, but also among women of reproductive age and pregnant women leading to premature birth and low birth weight (Hotez et al. 2004).

Typhoid and paratyphoid fevers

While enteric fevers such as typhoid and paratyphoid were leading causes of waterborne disease in previous centuries, morbidity and mortality diminished dramatically with the provisions of disinfected water supplies and improved sanitary facilities (Cutler and Miller 2005). The aetiological agents for typhoid and paratyphoid fevers are Salmonella enterica serovar Typhi (formerly S. typhi) and S. enterica serovar Paratyphi A and B (formerly S. paratyphi). There are an estimated 21 million cases of typhoid annually, causing 216,000 deaths (Crump et al. 2004). The milder paratyphoid accounts for an additional 5 million cases each year.

Trachoma

Trachoma accounts for 15 per cent of world blindness, with 6 million people affected and 150 million at risk of visual impairment (Kumaresan and Mecaskey 2003). Trachoma is caused by repeated eye infection with Chlamydia trachomatis. Children are the main reservoir for infection, with high prevalence of active trachoma (Mabey et al. 2003). Repeated infections result in deformation of the upper eye lid, abrasion of the cornea, and progressive loss of vision in later life. C. trachomatis is transmitted from the discharge of an infected eye via contaminated fingers, clothing, and eye-seeking flies (Musca sorbens) (Hu et al. 2010). Although the role of flies in the transmission of infection remains unclear, studies have shown that M. sorbens breed mainly in solid human faeces present in the environment and not in latrines (Emerson et al. 2000). Thus, safe excreta disposal may play an important role in reducing trachoma transmission. Improving water supplies and sanitation is part of the WHO-backed SAFE (surgery, antibiotics, facial hygiene, environmental improvement) strategy for controlling and preventing the disease.

Malnutrition

Water and sanitation are also linked to malnutrition, a separate source of significant morbidity and mortality. An estimated 165 million children under 5 are stunted (i.e. have a height-for-age Z score of less than −2); 55 million children are wasted (i.e. have a weight-for-height Z score of less than −2), of whom 19 million have severe wasting (weight-for-height Z score of less than −3) or severe acute malnutrition (weight-for-height Z score of –3 or lower or associated oedema) (Bhutta et al. 2013). Child underweight or stunting causes about 20 per cent of all mortality of children younger than 5 years of age; it also contributes to long-term cognitive impairment, poorer performance in school, fewer years of completed schooling, and lower adult economic productivity.

Effectiveness of water and sanitation in preventing disease

Barriers to transmission of faecal–oral diseases

As illustrated by the so-called ‘F-diagram’ (Fig. 2.6.1), the safe disposal of human faeces is the primary barrier in preventing faecal–oral transmitted diseases. Without removing excreta 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. Whether or not sanitation is adequate, hands can become contaminated with faeces, especially during anal cleansing following defecation or in cleaning a child after defecation. This may result in further transmission, either directly or indirectly through food, water, or other beverages, or fomites. Accordingly, hand washing is an important secondary barrier to faecal–oral disease transmission (Curtis and Cairncross 2003). Other secondary barriers include: (1) water quality interventions (e.g. safe distribution and storage or use of boiling or other point of use water treatment), (2) water supply interventions to increase the quantity and availability of water for personal and domestic hygiene, (3) proper cooking and food handling, and (4) control of mechanical vectors such as flies.

Evidence of effectiveness

Scores of studies have been conducted and published on the effectiveness of water, sanitation, and hygiene interventions to prevent infection and disease. Systematic reviews (Chapter 5.15) are a means of identifying, summarizing, synthesizing, explaining, and assessing the methodological quality of evidence of the effectiveness of health interventions with a variety of studies relating to a particular health intervention. In some cases, such reviews also employ meta-analyses or other statistical methods to estimate the pooled effect of the intervention across the studies included in the review. A number of such reviews have examined the evidence of effectiveness of water, sanitation, and hygiene interventions to prevent disease and infection.

Diarrhoeal diseases

Table 2.6.2 summarizes the results of five different systematic reviews of water and sanitation interventions to prevent diarrhoeal diseases published over the last 25 years. While there is conflicting evidence on the impact of water supply (quantity and access), there is consistent evidence that improvements in water and sanitation can make substantial contributions to the prevention of diarrhoeal diseases.

Table 2.6.2 Estimate of effect1 (and number of studies in square brackets) of systematic reviews of water and sanitation interventions to prevent diarrhoeal diseases

Intervention (Improvement)

Esrey et al. (1985) (range)

Esrey et al. (1991)

Fewtrell et al. (2005) (95% CI) (No. studies)

Clasen et al. (2006) (95% CI) (No. studies)

Waddington et al. (2009) (95% CI) (No. studies)

Wolf et al. (2014) (95% CI)2

Water quantity

25% (0–100%) (17)

27% (7)‌

Water quality

0.69 (0.53–0.89) (15)

0.57 (0.46–0.70) (38)

0.58 (0.50–0.67) (31)

   Source

16% (0–90%) (9)

17% (7)

0.89 (0.42–1.90) (3)

0.73 (0.53–1.01) (6)

0.79 (0.62–1.02) (3)

0.89 (0.78–1.01)

   Household (point-of-use)

0.65 (0.48–0.88) (12)

0.53 (0.39–0.73) (32)

0.56 (0.45–0.65) (28)

   Chlorination

0.63 (0.52–0.75) (16)

0.63 (0.55–0.72)

   Filtration

0.37 (0.28–0.49) (6)

0.41 (0.33–0.50)

   Solar disinfection

0.69 (0.63–0.74) (2)

0.63 (0.55–0.72)

   Floc-disinfection

0.69 (0.58–0.82) (6)

Water supply (point-of-distribution)

37% (0–82%) (8)

16% (22)

0.75 (0.62–0.91) (6)

0.73 (0.53–1.01) (6)

0.98 (0.89–1.06) (8)

0.89 (0.78–1.01)

Water supply and sanitation/hygiene

20% (7)

0.43 (0.33–0.55) (3)

Sanitation

22% (0–48%) (10)

22% (11)

0.68 (0.53–0.87) (2)

0.63 (0.43–0.93) (6)

0.84 (0.77–0.91)

Note: 1 for studies by Esrey and colleagues, estimate of effect is the median reduction in diarrhoeal disease from the reported studies; for other studies, estimate of effect is the pooled risk ratio from meta-analysis using random effects model. To compare results, the percentage reduction is 1 − RR (e.g. RR of 0.69 implies a 31 per cent reduction in risk).

2 Pooled estimates of effect in settings with unimproved water supply and prior to adjustment for non-blinding. For household interventions, estimates are for studies that combine treatment with safe storage.

Soil-transmitted helminth infection

A more recent review assessed not only the impact of sanitation interventions on soil-transmitted helminth infections but also water and hygiene (Strunz 2014). The review covers 94 studies, though only 5 were randomized controlled trials. Use of treated water was associated with lower odds of infection from any soil-transmitted helminth (OR 0.46, 95% CI 0.36–0.60). Piped water access was associated with lower odds of A. lumbricoides (OR 0.40, 95% CI 0.39–0.41) and T. trichiura infection (OR 0.57, 95% CI 0.45–0.72), but not any STH infection (OR 0.93, 95% CI 0.28–3.11). Access to sanitation was associated with decreased likelihood of infection with any soil-transmitted helminth (OR 0.66, 95% CI 0.57–0.76), T. trichiura (OR 0.61, 95% CI 0.50–0.74), and A. lumbricoides (OR 0.62, 95% CI 0.44–0.88), but not with hookworm infection (OR 0.80, 95% CI 0.61–1.06).

In one systematic review, the authors reported larger protective effect of sanitation interventions to prevent soil-transmitted helminth infection despite acknowledging significant imitations (most studies used a cross-sectional design and were of low quality, with potential biases and considerable heterogeneity) (Ziegelbauer et al. 2012). Availability of sanitation facilities was associated with significant protection against infection with soil-transmitted helminths, with ORs ranging from 0.46–0.58 depending on the type of helminth. Pooling studies reporting on latrine use yielded ORs of 0.54 (95 per cent CI: 0.28–1.02), 0.63 (95 per cent CI: 0.37–1.05), and 0.78 (95 per cent CI: 0.60–1.00) for Trichuris trichiura, hookworm, and Ascaris lumbricoides, respectively. The overall ORs, combining sanitation availability and use, were 0.51 (95 per cent CI: 0.44–0.61) for the three soil-transmitted helminths combined, 0.54 (95 per cent CI: 0.43–0.69) for A. lumbricoides, 0.58 (95 per cent CI: 0.45–0.75) for T. trichiura, and 0.60 (95 per cent CI: 0.48–0.75) for hookworm.

Schistosomiasis

Esrey and colleagues (1991) reported a median reduction in the prevalence of schistosomiasis of 73 per cent (range 59–87 per cent) from four water and sanitation interventions; the reduction was 77 per cent among the three studies they deemed rigorous. Piped-in water supplies and community washing and bathing facilities that reduced contact with surface waters were especially protective, leading to reductions in both prevalence and severity (Esrey et al. 1991). The reviewers noted that in Kenya, the installation of boreholes without laundry or shower facilities failed to reduce infection.

Two quasi-randomized, controlled interventional studies from China also suggest that improved excreta disposal is protective against schistosomiasis. In a 3-year quasi-randomized controlled trial (RCT), Chen et al. (2004) recorded a 43 per cent reduction from combined water, sanitation, and hygiene interventions that also included a snail control component. Zhang et al. (2005) reported a 45 per cent reduction in a 2-year quasi-RCT that included water, sanitation, and hygiene. Once again, these trials did not include sufficient clusters to reliably calculate confidence intervals around the point estimates of effect.

Typhoid and paratyphoid

No RCTs of water or sanitation interventions to prevent typhoid or paratyphoid have been reported. A recent review of global trends in these enteric fevers identified little direct evidence of the potential contribution of water or sanitation interventions (Crump and Mintz 2010). Nevertheless, there is evidence suggesting the effectiveness of water quality interventions. Cutler and Miller (2005) have shown the historical evidence on reductions in mortality associated with the introduction of clean water and sanitation in the United States. Case–control studies do suggest that the diseases are still associated with unsafe water and sanitation. In a study in Uzbekistan where typhoid remains endemic, cases were more likely to drink unboiled surface water outside the home (OR 3.0; 95 per cent CI: 1.1–8.20) (Srikantiah et al. 2007). In a similar case–control study in Bangladesh, drinking unboiled water at home was a significant risk factor (OR 12.1; 95 per cent CI: 2.2–65.6) (Ram et al. 2007). Among the risk factors for typhoid and paratyphoid in an urban setting in Indonesia were lack of a toilet in the household (OR 2.20; 95 per cent CI: 1.06–4.55) and use of ice cubes (OR 2.27; 95 per cent CI: 1.31–3.93). Enteric fevers are also a risk among travellers to endemic area, but effective vaccines are usually recommended against the risk of waterborne or foodborne transmission.

Trachoma

The evidence of the effectiveness of environmental interventions (including water and sanitation) alone to prevent active trachoma is not clear (Rabiu et al. 2012). Reviews of the WHO-backed SAFE strategy for trachoma control conclude that there is comparatively weak evidence of the effectiveness of the ‘F’ (facial cleanliness) and ‘E’ (environmental improvement) components that encompass improved access to water and better sanitation (Emerson et al. 2000a; Kuper et al. 2003). In a 6-month cluster RCT of 21 villages in the Gambia, Emerson and colleagues (Emerson et al. 2004) reported a reduction in fly catches among study clusters receiving latrines. However, the prevalence of active trachoma associated with the intervention was not statistically lower than among seven control clusters (RR 0.81; 95 per cent CI: 0.54–1.22). The study has not been repeated. In another review, access to sanitation was associated with lower trachoma as measured by the presence of trachomatous inflammation-follicular or trachomatous inflammation-intense (TF/TI) (OR 0.85, 95% CI 0.75–0.95) and C. trachomatis infection (OR 0.67, 95% CI 0.55–0.78) (Stocks et al. 2013). Hygiene practices that require adequate supplies of water, such as facial cleansing, were also protective against trachoma. However, living within 1 km of a water source and the use of sanitation facilities was not found to be significantly associated with TF/TI.

Malnutrition

Malnutrition is linked to water and sanitation, both through food production (irrigation and safe use of waste for fertilizer) and by preventing diarrhoea and enteric infections that interfere with normal adsorption of nutrients (Fewtrell et al. 2007). An association of malnutrition with diarrhoea has been well established, but the impact of interventions is less clear. In a pooled analysis of nine studies with diarrhoea and growth data for 1393 children, the probability of stunting at 24 months of age increased by 2.5 per cent per episode of diarrhoea, and 25 per cent of all stunting in 24-month-old children was attributable to having five or more episodes of diarrhoea in the first 2 years of life (Checkley et al. 2008). The Maternal and Child Undernutrition Series in The Lancet estimated that sanitation and hygiene interventions implemented with 99 per cent coverage would reduce diarrhoea incidence by 30 per cent, which would in turn decrease the prevalence of stunting by only 2.4 per cent (Bhutta et al. 2013). A report for the World Bank suggests that open defecation explained 54 per cent of international variation in child height by contrast with gross domestic product, which only explained 29 per cent (Spears 2013). However, a recent systematic review and meta-analysis of water, sanitation, and hygiene interventions on nutritional status found no evidence on impact on weight-for-age Z-scores and only a small benefit on height-for-age Z-scores in children under 5 years of age (Dangour et al. 2013).

Economic implications of water and sanitation interventions

Cost-effectiveness and cost–benefit analyses

Hutton and colleagues (Hutton et al. 2007) assessed the cost–benefit ratios in 17 WHO epidemiological subregions of five categories of water and sanitation interventions based on the MDG water and sanitation targets and additional steps to minimize environmental exposure. The interventions included: (1) improvements required to meet the MDGs for water supply, (2) interventions to meet the water and sanitation MDG, (3) increasing access to improved water and sanitation for everyone, (4) providing disinfection at point-of-use over and above increasing access to improved water supply and sanitation, and (5) providing regulated piped water supply in house and sewage connection with partial sewerage for everyone. The study found that all water and sanitation improvements were cost-beneficial in all developing world subregions. The main contributor to economic benefits was timesaving associated with better access to water and sanitation services, contributing at least 80 per cent to overall economic benefits. A more recent analysis confirmed these results, concluding that the global return per dollar invested was $5.50 for sanitation, $2.0 for water supply, and $4.30 for combined sanitation and water supply (Hutton 2013). It estimated the global costs of universal access amount over the 5-year period 2010–2015 to US$ 35 billion per year for sanitation and US$ 17.5 billion for drinking-water.

A more recent economic analysis estimated the cost–benefit ratios of water quality (point-of-use filtration or chlorination) and sanitation (community-led total sanitation) interventions and placed them in the context of other comparable interventions (long-lasting insecticide treated nets and cholera vaccination (Whittington et al. 2012)). The study also found the water and sanitation interventions to be cost-beneficial. Most of the benefits, however, arose from improved health outcomes, principally reductions in mortality. Significantly, the study found substantial heterogeneity among the results; it also emphasized the sensitivity of the findings to assumptions about benefits, uptake, and usage. It cautions against generalizing the results to settings where the underlying assumptions about the population and the intervention can vary dramatically. It recommends decentralized decision-making and priority setting of water and sanitations in contrast to setting targets and subsidies by international organizations and large donors.

Willingness to pay; pricing strategies

Despite fairly consistent evidence that water and sanitation interventions are cost-effective and cost-beneficial, consumer demand varies with the type of products and services offered. Demand for piped water services in developing countries is especially inelastic (Nauges and Whittington 2009), even though their corresponding health benefits are not well established as noted earlier. This is likely to be due to the perceived value of timesaving. On the other hand, point-of-use water chlorination, though potentially among the most cost-effective of WASH interventions, has achieved only limited market penetration despite large-scale social marketing campaigns (Clasen 2009).

There is also continuing debate over user fees and subsidies to support the dissemination of interventions such as water and sanitation. Public health officials generally support free or heavily subsidized services, citing positive externalities, price elasticity, and the need to reach the lowest income households with services. On the other hand, water and sanitation officials as well as governments often insist on the need for user fees, noting the need for cost recovery strategies to ensure expansion and maintenance of services.

Cost-effectiveness analyses and cost–benefit analyses suggest that improvements in water and sanitation yield both health and other valuable benefits, not only to those who receive the intervention but also to the public sector. Inadequate water and sanitation services also have significant negative externalities (costs imposed on others), such as the costs of over-extraction from water supplies, pollution of water sources, and environmental degradation. Even those who promote water as a basic right accept that some value must be attached to water to reduce waste, encourage conservation, and promote higher value uses. Infrastructural improvements in water and sanitation often fail to be initiated or sustained because of a reluctance to charge fully for the cost of delivering the services, inefficiency in collecting such charges, or diversion of the fees away from operation and maintenance. Understanding who benefits from improvements in water and sanitation can help justify the allocation of costs and secure financing.

Other benefits of water and sanitation interventions

Improving water availability (quantity and access)

As the section ‘Evidence of effectiveness’ suggests, improving water availability—even without a corresponding improvement in water quality—is associated with reductions of diseases transmitted through waterborne, water-washed, and water-based routes. This is partly due to the well-established relationship between the amount of water that people use and the time required to collect it (Cairncross and Feachem 1993). Fig. 2.6.2 shows the L-shaped curve that characterizes water consumption patterns based on service levels. While significant quantities of water are used if delivered directly to the home, the quantity used is fairly constant when the collection time is 5–30 minutes and further diminishes for longer collection times. In lower-income settings, average daily per capita consumption is about 150 L for those with household connections, 50 L for yard taps, and just 15 L for communal sources such as stand posts, wells, and springs. Thus, assessments of water availability are expressed in terms of distance: normally 1 km or round trip collection time (normally 30 minutes) (WHO and UNICEF 2013) but 0.5 km in disaster response (Sphere Project 2004).


Fig. 2.6.2 Time travel (in minutes) versus consumption (in litres per capita per day).

Fig. 2.6.2 Time travel (in minutes) versus consumption (in litres per capita per day).

Reproduced from Cairncross, S. and Feachem, R., Environmental health engineering in the tropics: An introductory text, Second Edition, John Wiley and Sons Ltd., Chichester, West Sussex, UK, Copyright © 1993, by permission of John Wiley and Sons Ltd.

A WHO report concluded that a minimum quantity of water for basic health protection is 20 L/person/day (Hutton and Bartram 2003). Of this, 7.5 L is for consumption (hydration and food preparation) and therefore must be of a quality to present minimal health risk; the balance is for basic personal and domestic hygiene. The report recognizes, however, that in addition to the direct health benefits associated with improving water supplies, there are indirect health and other benefits. Indirect health benefits may accrue from reducing the amount of time collecting water which can then be used more effectively at home caring for children or engaging in other productive activities (Cairncross 1987). Services at clinics, medical posts, and other healthcare facilities also benefit from improved water supplies. Sufficient water for irrigating gardens and crops can improve nutrition and generate income (Thompson et al. 2001). Vending water and making and selling beverages can also impact poverty. Finally, to the extent that people are paying for water, improved water supplies may result in savings that can be used for food and other necessities that may impact health outcomes.

Ecological sanitation

Within the sanitation sector there is an active group of advocates who promote the use of ecological sanitation (Winblad and Simpson-Hébert 2004). Ecological sanitation (EcoSan) works on the principle that urine and faeces are not just waste products, but assets that if properly managed, can contribute to better health and food production and reduce pollution. Managing such assets includes reducing pathogen loading to a safe level which is achieved by a combination of drying the faeces, increasing the pH, and storage for at least 12 months. Without good latrine management, pathogens can survive and create a risk to public health. The pathogen that causes greatest concern is Ascaris, which has a long persistence in the environment and a low infective dose (Cairncross and Feachem 1993). Public health risks need to be balanced against the potential benefits. In areas where land fertility is low, artificial fertilizer is expensive, and livelihoods are dependent on subsistence farming, the benefits of using excreta as a fertilizer/soil amendment could be considerable. Even when potential benefits can be demonstrated, local beliefs and taboos may limit acceptability or prevent adoption of the practice (Jackson 2005).

Improved school attendance

Although weaker than often asserted, there is some evidence that water and sanitation interventions at schools can improve school attendance, at least among girls (Freeman et al. 2012). This may be due to reduced incidence of disease resulting in fewer days of school missed as a result of illness. In Africa alone, Hutton et al. (2007) estimated that meeting the MDGs for water and sanitation would increase school attendance by 99 million days annually; full access to basic water and sanitation for all would increase school attendance by 140 million days each year. The sanitary needs of girls and the negative impact of lack of sanitation adversely impacts their attendance levels. In a recent trial in Kenya, schools with poor water access during the dry season that received combined water supply, hygiene promotion and water treatment together with improvements in sanitation experienced an increase in average attendance equal to 26 additional pupils per school on average (Garn et al. 2013). The proportion of girls enrolled in school also increased by 4%. In Uganda, 94 per cent of girls reported problems at school during menstruation and 61 per cent reported staying away from school (IRC International Water and Sanitation Centre 2006). Cultural and religious constraints in many settings make menstruation a taboo. If menstruation lasts over a week, there is a tendency for girls to skip the entire school year (Bharadwaj and Patkar 2004). Sanitation can play an important role in improving educational access for children with disabilities, through the improvement of paths, latrine floors, and installation of handrails (Bannister et al. 2005).

Security and gender equality

Improved sanitation and water supplies advance security and gender equality for women and girls. Household sanitation can increase their safety by avoiding the dangers of sexual assault and harassment faced when practising open defecation or using latrines away from their homes. Safe, private, and proximate latrines are now considered a basic human right (United Nations 2010); they are a particular issue for women in emergencies and conflicts (Sphere Project 2004). Research in Kenya revealed that women would defecate into plastic bags and throw them into streets (‘flying toilets’) because they feared being raped when using latrines shared with men (Maili Saba Research Report 2005). They were also afraid of being seen to be using latrines too regularly and preferred to bathe within their own homes after dark where they felt safer. Young children often prefer open defecation due to fear of falling into pits in poorly-designed or unsuitably-adapted latrines.

HIV/AIDS

It is well known that access to safe drinking water and sanitation prolongs the lives of people living with HIV/AIDS (PLWHA) by reducing the risk of opportunistic infections, including diarrhoeal diseases (Peletz et al. 2013). Household-based water treatment has been shown to be an effective intervention in preventing mortality and morbidity in a population with one or more persons infected with HIV (Colford et al. 2005; Lule et al. 2005; Peletz et al. 2012). There is also evidence that household-based water filters and insecticide treated bednets for malaria slow the progression of HIV (Walson et al. 2012). Water and sanitation are now recognized as particular priorities in home-based care of PLWHA (WHO 2008). Point-of-use water treatment products are now included in health kits for people living with HIV/AIDS (Colindres et al. 2007). Efforts are also encouraged to ensure that mothers infected with HIV have safe drinking water (or point-of-use water treatment products) to prepare infant formula for use as an alternative to breastfeeding in order to minimize mother–child transmission.

Recent and emerging developments in water and sanitation

Post-2015 goals in water and sanitation

The MDG water and sanitation targets—to halve the proportion of the 1990 population without sustainable access to safe drinking water and basic sanitation—have been a major factor in mobilizing efforts to expand water and sanitation coverage. While there is still some controversy about JMP claims on the water target and overall disappointment on progress to the sanitation target, efforts are now underway to establish successor goals. As this chapter goes to press, it is still unclear what form these goals and the corresponding targets will take. However, recent proposals have included four possible targets: (1) by 2025, no one practises open defecation; (2) by 2030, everyone uses a basic drinking-water supply and handwashing facilities when at home, all schools and health centres provide all users with basic drinking-water supply and adequate sanitation, handwashing facilities, and menstrual hygiene facilities; (3) by 2040, everyone uses adequate sanitation when at home, the proportion of the population not using an intermediate drinking-water supply service at home has been reduced by half, the excreta from at least half of schools, health centres, and households with adequate sanitation are safely managed; and (iv) all drinking-water supply, sanitation, and hygiene services are delivered in a progressively affordable, accountable, and financially and environmentally sustainable manner (WHO and UNICEF 2014). In addition, there are proposals to change certain definitions used in monitoring these targets. A ‘basic drinking-water supply’ would include the JMP’s current ‘improved’ water supplies (excluding protected wells or springs in urban areas) provided the time for collection/return does not exceed 30 minutes. An ‘intermediate’ water supply would mean an improved drinking-water source on premises that delivers acceptable quantities at least 12 of the past 14 days of water with <10 cfu (colony-forming units) of Escherichia coli per 100mL. ‘Adequate’ sanitation would mean use of an ‘improved’ sanitation facility at home, and shared sanitation would be treated as ‘improved’ if it otherwise meets the required service level and was shared by no more than five households or 30 people. Future developments on the post-2015 water and sanitation targets can be followed by consulting the JMP website: http://www.wssinfo.org/post-2015-monitoring/overview.

Systems approach to understanding enteric pathogen transmission

Much of the research described in previous sections regarding the health impact of water and sanitation interventions has focused on assessing the impact of interrupting particular transmission pathways. Increasingly, epidemiologists are recognizing the interaction and interdependencies that characterize the transmission of enteric pathogens. This is leading to calls for a systems approach that not only acknowledges the multiple transmission pathways and varied aetiological agents involved in diarrhoea and other enteric diseases but also their dynamism and the community level impact of interventions (Eisenberg et al. 2012). Examples of this community effect are the health benefits that inure to non-adopters who live adjacent to households with latrines or who practise effective household water treatment. Interventions that interrupt transmission of one or more pathways can also impact transmission through other pathways of one or more pathogens. It is important that studies endeavour to capture externalities and the wider impact of an intervention at the community level, both to understand and design interventions that that optimize this larger effect and to correctly assess the impact (and cost-effectiveness) of the interventions.

Water safety plans and microbial risk assessment

Traditionally, the water sector relied on compliance with end-product standards to ensure the safety of drinking water. Most drinking water standards are based on WHO guidelines that establish maximum limits for known or suspected microbial and chemical pathogens as well as physical/aesthetic characteristics. Under this approach, drinking water is to be free of pathogens at the point of delivery as demonstrated by the absence of a prescribed indicator of faecal contamination, such as Escherichia coli or thermotolerant coliforms (TTCs). However, the WHO adopted a risk assessment and risk management approach for improving drinking water quality (WHO 2012). The approach calls on water providers to develop and implement water safety plans similar to the hazard assessment critical control point (HACCP) approach used in the food industry to identify and control potential threats to safety. This latest rolling revision to the GDWQ also encourages greater surveillance to verify compliance.

This risk-based approach uses health-based targets for water quality. This is based on quantitative microbial risk assessment (QMRA), an approach developed for calculating the burden of disease from potential pathogens. QMRA sets pathogen limits based on the evidence concerning exposure assessment, dose–response analysis, and risk characterization (Haas et al. 1999). Risk assessment and acceptable levels of risk are expressed in terms of DALYs. Reference pathogens are defined for each category of microbes. Significantly, these do not necessarily coincide with long-standing indicator organisms and may require capacity building in new laboratory techniques. Limited country-specific data and other resources may also delay full implementation of this approach in many countries.

Need for consistency/adherence in safe water consumption

Epidemiological modelling using QMRA has also been used to estimate the impact of sporadic exposure to contaminated drinking water, either as a result of interruptions in water supplies (Hunter et al. 2009) or from inconsistent use of point-of-use water treatment (Brown and Clasen 2012; Enger et al. 2013). The models show that in settings with moderately contaminated water supplies, much of the health benefit from improved drinking water quality is vitiated by even occasional consumption of untreated water. These results raise questions about the health benefits that can be gained from unreliable water supplies. Moreover, insofar as point-of-use water treatment campaigns often fail to achieve high levels of adherence, these models raise questions about the potential health benefits from household-based water treatment.

Wastewater reuse

QMRA is also used in the second edition of the WHO’s Guidelines for the Safe Use of Wastewater, Excreta and Greywater for agriculture and aquaculture (WHO 2006). As an estimated 70 per cent of water withdrawals from surface and subsurface sources are used for agricultural purposes (Water Resources Institute 2007), the agricultural sector is particularly eager to develop safe, economical, and effective water sources for crop irrigation. Wastewater can be high in plant nutrients (nitrogen, phosphorus, and potassium), minimizing the need for chemical fertilizers and producing higher incomes for farmers (Ensink and van der Hoek 2007). As municipalities in lower-income settings struggle to treat even drinking water, however, few are able to remove potential pathogens from wastewater, leaving an estimated 80 per cent of sewage untreated. The WHO Guidelines attempt to balance the benefits of wastewater reuse with the need for food security. As treated wastewater is also being increasingly viewed as a potential source of drinking water in water stressed regions, additional guidance based on public health evidence will be necessary.

Household-based water treatment

For the hundreds of millions who lack household water connections that provide drinking water on a 24/7 basis, water is often collected and stored in the home until needed. It is well known that even water that is safe at the point of collection undergoes frequent and extensive re-contamination during collection (or compromised distribution), storage, and use in the home (Wright et al. 2004). While providing safe, piped in, disinfected water to each household is an important goal, even the purported achievement of the MDG water target leaves more than three-quarters of a billion people without access to improved water and hundreds of millions more without safe drinking water (Clasen 2012). Accordingly, the WHO and others have called for other approaches that will accelerate the heath and economic gains associated with safe water while progress is made in improving infrastructure.

Household water treatment and safe storage (HWTS) represent one such alternative (Sobsey 2002). Boiling, filtering, and chemically disinfecting water in the home are already in use, with more than 1 billion people reportedly treating their water at home before drinking it (Rosa and Clasen 2009). In many settings, both rural and urban, populations have access to sufficient quantities of water, but that water is unsafe. Because point-of-use interventions can improve the microbiological integrity of the water at the point of ingestion, they can reduce exposure if used correctly and consistently (exclusively) by a vulnerable population. Recent systematic reviews have shown household-based interventions (home-based boiling, chlorination, filtration, solar disinfection, and flocculation/disinfection) to be significantly more effective than traditional, non-reticulated source-based interventions (protected wells and springs, boreholes, communal tap stands) in improving microbiological water quality and reducing diarrhoeal disease (Fewtrell et al. 2005; Clasen et al. 2006; Waddington et al. 2009). The up-front cost of treating such water at the point-of-use can be dramatically less than the cost of conventional water treatment and distribution systems. Point-of-use water treatment, such as household-based chlorination, is the most cost-effective intervention to prevent diarrhoeal disease across a wide range of countries and settings (WHO and UNICEF 2002; Clasen et al. 2007). It is also among the most cost-beneficial (Hutton et al. 2007).

In 2003, the WHO helped organize the International Network for the Promotion of Safe Household Water Treatment and Storage, a global collaboration of UN and bilateral agencies, non-governmental organizations, research institutions, and the private sector committed to improved household water management as a component in water, sanitation, and hygiene programmes. The Network’s website contains a considerable amount of information on household water management (http://www.who.int/household_water/en).

There is evidence, however, that the health impact from HWTS intervention trials may be exaggerated due to placebo effect and reporting bias. While more than three dozen studies of HWTS interventions reported a protective effect, none of the blinded studies that attempted to blind the intervention with a placebo found the effect to be statistically significant (Clasen et al. 2006). A large-scale double blind trial of chlorine tablets in India reported no impact of the intervention on diarrhoea or weight-for-height Z-scores in children under 5 years old (Boisson et al. 2013). This and other evidence of the lack of successful strategies for achieving adoption of HWTS interventions at scale has led some investigators to conclude that further efforts to scale up the intervention are not supported by the evidence (Schmidt and Cairncross 2009). Other investigators have noted, however, that if the estimates of effect of HWTS interventions are discounted by the exaggerated effect associated with open trials of reported outcomes (like self-reported diarrhoea), the interventions are still protective, particularly for those HWTS methods whose sustainability can be maintained (Hunter 2009; Wolf et al. 2014).

There is a need for additional assessments of HWTS interventions using placebos and objective outcomes in order to determine the actual protective effect of HWTS interventions to prevent diarrhoea. Even so, the size of the effect, if any, is likely to depend largely on the level of exposure, principal aetiological agent, other potential sources of exposure, the efficacy of the HWTS method, the consistency of its use, and other factors that research may not yet have identified.

Shared and public sanitation

An estimated 450 million people—including a fifth of the population of sub-Saharan Africa and Eastern Asia—rely on public or other shared sanitation facilities (WHO and UNICEF 2013). Historically, such shared facilities are excluded from the definition of ‘improved’ sanitation for purposes of monitoring progress toward the MDG sanitation target, regardless of the level of service or number of people sharing them, because they are deemed unacceptable, unhygienic, and inaccessible. The JMP is currently considering a revision to this policy that would allow shared latrines to be considered ‘improved’ if they otherwise meet the required service level and are shared by no more than five households or 30 persons. However, there is little evidence to support this change. A systematic review and meta-analysis of 11 studies reporting on diarrhoea found increased odds of disease associated with reliance on shared sanitation (OR 1.39; 95 per cent CI: 1.14–1.70) (Heijnen et al. 2014). While there was some evidence of increased risk with the number of households sharing, there was an elevated risk at any level of sharing. An analysis of JMP data also found evidence of increased risk of diarrhoea associated with sharing latrines, even after adjusting for likely confounders (Fuller et al. 2014).

There are various reasons why observational studies might find shared sanitation to be associated with adverse health outcomes. These include differences in the underlying risk profile of people who rely on shared sanitation rather than individual household latrines, differences in latrine maintenance and use, increased exposure to pathogens circulating in the public domain, and differences in sludge management that increase community exposure. Shared sanitation is likely a necessity, particularly in high-density urban settings. It represents an increasing proportion of the types of sanitation on which populations in low-income settings rely. It is therefore necessary for research to determine whether shared sanitation actually increases risk, and if so, the reasons therefor and the interventions that can be implemented to mitigate any such increased risk.

Safe disposal of child faeces

While there are few published studies, the evidence suggests that in many low-income settings, nappies and potties are rarely available or used, making the hygienic collection of early child faeces difficult; if collected, such faeces are often disposed of in a manner that does not prevent further exposure (Gil et al. 2004). In fact, the unsanitary disposal of child faeces may present a greater health risk than that of adults. First, young children represent the highest incidence of enteric infections, and their faeces are most likely to contain agents. Second, young children tend to defecate in areas where susceptible children could be exposed. Third, young children who are also most at risk of mortality and the serious sequelae associated with enteric infection are most likely to be exposed to these ambient agents due to the time they spend on the ground, their tendency to put fingers and fomites in their mouths, and common behaviours such as geophagia. In a meta-analysis of ten observational studies published between 1987 and 2001, Gil et al. (2004) found that child faeces disposal behaviours considered risky (open defecation, stool disposal in the open, stools not removed from soil, stools seen in household soil, and children seen eating faeces) were significantly associated with an increased risk of diarrhoeal diseases (relative risk (RR) 1.23; 95 per cent CI: 1.15–1.32); behaviours considered safe (use of latrines, nappies, potties, toilets, washing diapers) was borderline protective (RR 0.93; 95 per cent CI: 0.85–1.00).

There is evidence that even households with latrines often fail to disposal of child faeces safely; more commonly, they are either not collected or are disposed of with the household’s other solid waste (Majorin 2012). By definition, this renders the practice ‘open defecation’ even though these households are usually counted as having ‘improved sanitation’ due to the presence of the latrine (WHO and UNICEF 2013). Efforts to end open defecation will not be successful unless they include interventions to ensure the safe disposal of child faeces.

Technological and programmatic innovations

Steps to improve water supplies and sanitation, particularly in rural and remote locations, have proved especially challenging. Despite concerted efforts over past decades, vast numbers in Africa and South/South East Asia still lack improved water and sanitation (WHO and UNICEF 2014). While a variety of communal and household-level options have been promoted as alternatives to customary approaches in order to improve water quality, quantity, and proximity, some of these have been found wanting in terms of technological suitability, cost, and sustainability. New challenges include natural or man-made chemical contamination, saline intrusion, increasing urbanization, falling water tables, threats associated with climate change, and increasing demand for agricultural and industrial uses of water. High upfront costs, lack of financing, uncertain land tenure, inadequate skilled masons for construction, pit-emptying, longer-term waste disposal, and urbanization are major challenges in sanitation.

Public health professionals, donors, programme implementers, social entrepreneurs, and the private sector have responded to these challenges by developing and promoting a variety of technological and programmatic innovations for improving water supplies and sanitation, especially among low-income populations. In water, these include developments in rainwater harvesting, water locating, borehole drilling, well digging, locally-fabricated pumps and other water lifting devices, self-supply strategies, small community water treatment and/or distribution systems, water filling stations/kiosks, and a variety of point-of-use water treatment technologies. In sanitation, much of the effort in low-income settings focuses on improved on-site solutions in rural settings and alternatives to conventional sewerage in urban settings. Communal private latrines have been promoted widely in India and elsewhere. New technologies include cheaper, lightweight squatting slabs, composting toilets, digestion chemicals, multichamber pits, pit-emptying, and improved separation of liquid and solid excreta. Sludge is increasingly being viewed as a useful product rather than waste, with innovations in collection and processing. Many of these innovations are accompanied by entrepreneurial initiatives and public–private partnerships; others through micro-finance and base-of-the-pyramid marketing. While some of these innovations appear promising, lessons from the past suggest that understanding and responding to the particular circumstances present in a given setting—and especially what the target population itself wants and is willing to pay for—are especially important in achieving large-scale sustainable improvements that will also impact public health. Technical innovations in water and sanitation that do not address the need for behaviour change are also unlikely to achieve optimal uptake and impact.

Water and wastewater testing and microbiology

American Public Health Association (APHA), the American Water Works Association (AWWA), and the Water Environment Federation (WEF) jointly publish Standard Methods for the Examination of Water and Wastewater, the definitive guide for water quality testing. The 22nd edition published in 2012 and available online (APHA et al. 2012) contains methods for assessing physical properties, metals, inorganic non-metallic constituents, aggregate organic constituents, individual organic compounds, radioactivity, toxicity, microbiological examination, and biological examination (APHA et al. 2012). Nevertheless, there are continuing debates about even fundamental issues, such as the use of indicators of faecal contamination such as coliforms, thermotolerant coliforms (TTC), and Escherichia coli (Gleeson and Gray 1997). The International Water Association’s Health Related Water Microbiology Specialist Group is a rich source of research and new developments in the microbiology of water and waste, including water and wastewater treatment and its effects on health and the environment (including chlorinated by-products), methods in microbiology, microbe tracking and behaviour in water systems and the environment, rapid testing and monitoring, issues presented by bioterrorism, epidemiology and microbial risk assessment, and treatment processes.

Community-led total sanitation

First developed in Bangladesh in 1999 and expanding widely elsewhere, community-led total sanitation (CLTS) is an approach that empowers local communities to stop open defecation and to build and use latrines without the support of external hardware subsidies. Through the use of participatory techniques, community members analyse their own sanitation situation, including the extent of open defecation and the possibilities of faecal–oral contamination. This is designed to ignite a personal sense of disgust and shame that translates into collective action to reduce the impact of open defecation (Kar 2003). By triggering collective behaviour change, CLTS places the community, rather than the household, at the centre of the decision-making process. Peer pressure and civic pride are important motivating factors. The particular design of a latrine is secondary to the emphasis on 100 per cent coverage. The results can be impressive, with whole communities changing from open defecation to latrine use in a matter of months (Kar 2003). The approach has since been rolled out in Africa and Asia, and there is some evidence of its sustainability (Kar and Bongartz 2006). Nevertheless, the use of shaming and other social pressure to encourage latrine ownership is controversial (Bartram et al. 2012). Recent reconsideration of various aspects of the approach has resulted in proposed changes that are now promoted under the moniker ‘CLST+’.

Sanitation marketing

Sanitation marketing uses a commercial approach to the production and delivery of sanitation technologies and engages the private sector for production and delivery in a financially and institutionally sustainable manner (Jenkins and Sugden 2006). Such a marketing approach has been recommended over typical public-sector promotion of sanitation since it helps ensure that people choose to receive what they want and are willing to pay for, is financially sustainable, is cost-effective, and can be taken to scale (Cairncross 2004). Sanitation marketing adopts a consumer perspective, starting with an understanding of which products and services the target population wants, will pay for, will maintain, and are appropriate to the local context. It seeks to develop a sustainable sanitation industry, which is not dependent on external donors for hardware subsidies or long-term support for its continuation (Water and Sanitation Program n.d.). It recognizes the household as the key decision-maker regarding their defecation practice and the importance of effective public private partnerships. The extent to which the approach is capable of reaching the base of the economic pyramid has not yet been shown.

Scaling up sanitation; subsidies

Research has begun to explore the drivers and constraints toward latrine adoption (Jenkins and Curtis 2005; Jenkins and Scott 2007). Results demonstrate that while public health and economic benefits are the main societal reasons for investing in sanitation, householders have different reasons for wanting a latrine (Table 2.6.3). Research has shown that the rate of uptake of sanitation interventions increases as information spreads from one household to another, much like the adoption curves that characterize many new innovations (Cairncross 2004; Jenkins and Curtis 2005). Householder-perceived advantages of using a latrine become apparent as housing density starts to increase and when the need for privacy, convenience, and maintaining dignity become more important.

Table 2.6.3 Inventory of stated benefits of improved sanitation from the private vs. public perspectives

Household perspective1

Society–public perspective2

  • Increased comfort

  • Increased privacy

  • Increased convenience

  • Increased safety, for women, especially at night, and for children

  • Dignity and social status

  • Being modern or more urbanized

  • Cleanliness

  • Lack of smell and flies

  • Less embarrassment with visitors

  • Reduced illness and accidents

  • Reduced conflict with neighbours

  • Good health in a very broad cultural sense, often linked to disgust and avoidance of faeces

  • Increased property value

  • Increased rental income

  • Eased restricted mobility due to illness, old age

  • Reduced fertilizer costs (ecological sanitation)

  • Manure for crop production (ecological sanitation)

  • Reduced excreta-related disease burden (morbidity and mortality) leading to:

    • Reduced public healthcare costs

    • Increased economic productivity

  • Increased attendance by girls at school (for school sanitation) leading to broad development gains associated with female education

  • Reduced contamination of ground water and surface water resources

  • Reduced environmental damage to ecosystems

  • Increased safety of agricultural and food products leading to more exports

  • Increased nutrient recovery and reduced waste generation and disposal costs (for ecological sanitation)

  • Cleaner neighbourhoods

  • Less smell and flies in public places

  • More tourism

  • National or community pride

2 Reasons for public action stated in studies and documents but rarely quantified or ranked, see Evans et al. (2004); Jenkins and Sugden (2006).

Subsidizing latrine construction is a controversial issue within the sanitation sector. Public incentives to private individuals are justified in an economic sense when there are externalities—social benefits that go beyond the private benefits associated with a given private action. As the public health benefits of limiting open defecation are greater than the private benefits an individual gains by choosing use of latrines over open defecation, sanitation may constitute a public good, thus justifying subsidies. However, for scaling up of sanitation to be successful, subsidies must be used to encourage householders to build and use latrines and help them overcome the constraints rather than to cover the actual costs of construction. Moreover, the public service priority needs to focus on safely and efficiently managing excreta within the larger community, especially in dense urban slums, after it has left the private domain of households (Evans et al. 2004; Methra and Knapp 2005). Inappropriately applied subsidies also have the negative effects of creating dependency, distorting the behaviour of the private supply market, and perhaps most importantly, not reaching the poor.

Enteropathy

Beyond the impact of diarrhoea on malnutrition, researchers have postulated that repeated exposure to faecal pathogens may be a significant cause of environmental (tropical) enteropathy, a subclinical condition characterized by malabsorption, villus atrophy, crypt hyperplasia, T-cell infiltration, and general inflammation of the jejunum (Humphrey 2009). Enteropathy is caused by faecal bacteria ingested in large quantities by young children living in conditions of poor sanitation and hygiene. Humphrey has suggested that that the primary causal pathway from poor sanitation and hygiene to undernutrition is tropical enteropathy and not diarrhoea. If so, current estimates may have substantially underestimated the contribution of sanitation and hygiene to growth because the effect is modelled entirely through diarrhoea. A recent study in Bangladesh found that markers of enteropathy linked to unhygienic environments (Lin et al. 2013). Further research is underway to assess the impact of water and sanitation interventions on this condition (Arnold et al. 2013).

Challenges in water and sanitation

Failure to treat diarrhoea as a serious disease

One of the threshold constraints to scaling up water and sanitation is the belief that diarrhoea—the main health threat associated with poor water and sanitation coverage—is not a disease. Figueroa and Kincaid (2010) cite numerous studies from various countries in which participants reported diarrhoea to be a natural and even desirable condition, especially in young children, not worthy of special preventative measures. Although health benefits often lack significant motivational impetus for driving preventative measures, the fact that diarrhoea is not even considered a disease by many of the most vulnerable populations further limits this strategy. Among policymakers and health officials faced with a variety of life-threatening diseases, diarrhoea may not receive the commitment of resources that its status as the third leading cause of morbidity and mortality from infectious disease would suggest it deserves.

Lack of public-sector coordination

In most countries, a variety of agencies and authorities are responsible for some part of water and sanitation. These typically include the ministries of water, health, water resources, environment, local government, rural development, and education. In many cases, there are also federal, regional, district, and local levels of government. Rarely do any of these ministries take full responsibility for all aspects of water or of sanitation. The result is often a patchwork effort that lacks funding and coordination. There are important examples of successful coordinated public sector efforts. In South Africa, strides in sanitation are occurring because of a national decision and plan which set out targets, clear strategies, significant resources, and accountability (Muller 2002). Ethiopia has also achieved considerable success in improving water and sanitation coverage, particularly in the Southern Nations, Nationalities and Peoples Region, where a commitment at the senior levels translated into coordinated and sustained action (Bibby and Knapp 2007).

Bias toward large, infrastructural solutions

Public-sector advocacy, funding, and support has been shown to be an important factor in the successful scaling up of oral rehydration salts, insecticide-treated nets, and other interventions directed at environmental health. To date, however, governmental support for community and household-based water and sanitation interventions programmes has not been extensive in most countries. This is due in part to the engineering orientation of the applicable ministries, and their emphasis on larger-scale, infrastructural improvements, especially in urban and peri-urban settings. Nearly all populations who do not enjoy piped-in water on a 24/7 basis express priority for increasing the quantity and access to water over improving its quality. Governments respond accordingly, aware not only of the political value from these popular projects (and the particularly photogenic value of water emerging from massive new pipes), but also the economic gains that are available from reducing the time people spend collecting and transporting water to their homes and from the productive use of water in agricultural activities. Multilateral and bilateral funding also tends to focus on such infrastructural water projects, despite compelling evidence that HWTS is more cost beneficial and highly cost-effective (Clasen et al. 2007; Hutton et al. 2007).

Uncertainty about the role of the private sector

Water and sanitation have traditionally been supplied by the public sector, particularly in Europe and North America where coverage, service levels, and costs are optimal. As governments, particularly in lower-income settings, have been unable to deliver services such as power, transportation, and even health and education to much of the population, they are increasingly relying on the private sector to provide such services. There are some apparent success stories where the private sector, through concessions, public–private partnerships, or other vehicles, enhances the coverage and service level of water and sanitation through increased investment and improved management of fee collection and delivery. At the same time, there are at least some notorious cases, such as Cochabamba, Bolivia, where a concession was opposed due to the perception at least that the private-sector partners were putting profits ahead of performance. There is certainly a need for regulation, as these services are usually a natural monopoly and market forces, if left unchecked, will favour delivery to higher-density and higher-income areas where paybacks are faster and costs/risks lower. The United Nations Development Programme (UNDP), World Bank, and others have examined the constructive role that the private sector can play in helping scale up the delivery of water and sanitation services (UNDP 2007). Balancing the potential contribution of the private sector against the needs of the target population will continue to represent a significant challenge for policymakers.

Decoupling sanitation from water

Since the 1990s, there has been an effort to always integrate water supply, sanitation, and hygiene promotion in developing countries within the same project. As a result, sanitation and hygiene have piggybacked on the political and community demand for improved water supplies. However, many effective interventions to improve excreta disposal do not require improvements in water supplies. While the water supply sector is dominated by engineers who lean towards technical solutions, sanitation, and hygiene promotion rely more heavily on understanding and changing behaviour, a different set of skills. As a result, staff in integrated projects naturally concentrate on water supplies, whilst excreta disposal fails to receive the resources it requires. The sanitation element is usually built around the process of providing the water supply; in fact, sanitation differs in that it requires a household rather than a community decision, requires more time, and is more complex from a behaviour change perspective. By decoupling sanitation from water, it may be possible to increase coverage more rapidly, particularly in remote areas in which water interventions are unlikely to reach in the near future.

Excreta disposal in urban unplanned areas

While urban areas generally have higher rates of sanitation than rural areas, the rapid growth of informal settlements and urban slums presents a particular challenge for sanitation (WHO and UNICEF 2014). The lack of planning controls can result in ever increasing housing densities as plots are divided and subdivided either to house expanding extended families or to increase rental income. Eventually the area becomes saturated. This complicates excreta management in two ways: (1) streets and passages become very narrow making it impassable for latrine- and septic-emptying vehicles, and (2) the space available in each compound is insufficient to build initial or replacement latrines.

Another important and sensitive question with urban sanitation is the divide between public and private responsibility. Public funds are used to install, manage, and maintain public sewers and tariffs or taxation used to recover costs. No such publicly funded services are provided for the poor living in the unplanned high-density areas, and excreta disposal is regarded as being the sole responsibility of the household. It is arguable that the public health benefits from providing an appropriate pit emptying service could be so great that it warrants total public funding and provided free of charge to the poor.

Conflicting objectives in sanitation

Sanitation projects usually aim for a combination of four often-conflicting objectives. The first is to build a large number of latrines in a relatively short time, driven in part by the MDGs or national targets. In such cases, projects often use a supply-driven approach that coerces, entices, or persuades householders to build latrines by providing a generous subsidy, normally in the form of free hardware and/or labour. But when funding ends, the delivery and support mechanisms dissolve and the community members are left, as they started, with a lack of latrine component supply chains and nowhere to turn to for support. The second objective is to develop a sustainable sanitation industry that can continue providing latrines for many generations to come. This requires a good understanding of demand, the motivations and constraints of households in building and using latrines, and the use of marketing techniques to develop, promote, and supply better latrine components. This is a longer-term process which will not result in a large number of latrines being built in a short period of time and is therefore not attractive to politicians, donors, government officials, and implementers wanting instant MDG-driven solutions and to be seen to be doing something. The third objective driving sanitation is to enhance sustainable livelihoods and envir- onmental improvements. This can be achieved by taking an ecological sanitation approach to latrine building which ensures that the nutrients in the excreta are reused to grow crops. The fourth objective is organizational insistence that their work must be targeted at the poorest of the poor. These are the most risk adverse, hardest to reach, price-sensitive members of the population who are also likely to be the least well educated and socially or politically connected. This makes them the least likely people to benefit from either a supply- or a demand-driven approach. While a targeted, sustainable, demand-driven, livelihood-enhancing latrine building programme that builds a large number of latrines in a short period of time is the ideal, decision-makers need to understand the weaknesses of each approach and prioritize their expect- ations accordingly.

Conclusion

Unlike many of the other challenges in public health, the solutions for eliminating most of the disease burden associated with poor water and sanitation are well known. All but the poor have enjoyed the health, economic, and other benefits associated with safe drinking water and basic sanitation for decades. The fact that hundreds of millions still lack access to these fundamental resources is a scandal that generations have allowed to persist simply as a matter of misguided priorities. And as the ‘haves’ continue to make rapid gains, they are not only increasing the gap over the ‘have-nots’ but also using up larger amounts of the world’s limited water supplies and capacity for waste disposal, making it more difficult and costly for others to join their privileged club.

The need to extend water and sanitation coverage is acknowledged at the highest international levels, and progress is being made. Whether these efforts will be any more successful than those expressed in previous international declarations and goals is not yet clear. As the poor continue to wait for the piped-in water supplies and sanitary disposal that they deserve, however, it is incumbent on the public health community to develop, assess, and promote effective, low-cost, and sustainable alternatives and creative delivery strategies in order to accelerate access to the health gains associated with safe drinking water and basic sanitation.

Key points

  • While safe drinking water and sanitation are widely recognized as fundamental public health interventions, more than a sixth of the world’s population still lack improved water supplies and 40 per cent lack basic sanitation.

  • The infectious diseases associated with unsafe drinking water and poor sanitation impose a heavy burden, especially on the poor, the very young, and the immunocompromised; they also aggravate poverty, education, and economic development.

  • There is strong evidence that interventions to improve water supplies or sanitation can be effective in preventing diarrhoea, soil-transmitted helminth infections, schistosomiasis, and typhoid fevers.

  • Water and sanitation interventions have also been shown to be cost-effective and cost-beneficial, with significant savings to the public sector from reduced healthcare costs; there is also evidence of other economic and developmental benefits from improved access to water and sanitation.

  • A variety of recent and emerging developments, including new methods for assessing and monitoring the risk of diseases associated with water and sanitation as well as alternative technologies, programmatic approaches, and implementation strategies, may contribute to improved targeting, coverage, uptake, and sustainability.

  • Nevertheless, significant political, social, economic, and developmental challenges must be addressed in order to successfully scale up some of these interventions on a sustainable basis and thus provide the most vulnerable populations with the health and other benefits of safe drinking water and sanitation.

Acknowledgements

The author acknowledges the contributions of Steven Sugden to a previous version of this chapter.

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