The Oxford Research Encyclopedia of Global Public Health has moved behind the paywall. For information on how to continue to view articles visit the how to subscribe page.
Dismiss
Show Summary Details

Page of

Printed from Oxford Research Encyclopedias, Global Public Health. Under the terms of the licence agreement, an individual user may print out a single article for personal use (for details see Privacy Policy and Legal Notice).

date: 30 September 2022

The Evidence Base for Cognitive, Nutrition, and Other Benefits From Water, Sanitation, and Hygiene Interventionsfree

The Evidence Base for Cognitive, Nutrition, and Other Benefits From Water, Sanitation, and Hygiene Interventionsfree

  • Jennifer Orgill-MeyerJennifer Orgill-MeyerGovernment and Public Health, Franklin and Marshall College

Summary

Cost-benefit analysis of WASH (water, sanitation, and hygiene) interventions have traditionally focused on two primary benefits: improved health outcomes, usually measured as reduced diarrheal disease incidence, and reduced time burdens from collecting water, treating water, or traveling to open defecation or shared sanitation sites. However, there are also many other important benefits of water, sanitation, and hygiene interventions for policymakers and researchers to consider, such as improved nutrition and decreased stunting, improved cognitive development and educational attainment, and quality-of-life improvements for women.

Reduced fecal exposure from improved WASH may decrease not only diarrheal disease incidence but also the risk of environmental enteropathy, a condition that reduces the nutritional absorptive capacity of the gut. Environmental enteropathy results in a range of outcomes associated with malnutrition, such as wasting, stunting, and anemia. A growing body of literature has explored the direct relationship between improved sanitation environments and stunting. There are mixed findings from these research studies, suggesting that intervention adherence and baseline sanitation conditions may be important to realizing any potential stunting benefits. The economics literature has documented a strong inverse relationship between childhood stunting and lifetime earnings.

Reduced absorptive capacity from environmental enteropathy may also hinder cognitive development in children. Recent research documents a strong relationship between improved sanitation environments and cognitive development in children, though some studies find no relationship. Beyond cognition, improved health from reduced fecal exposure may also affect a child’s ability to attend school, and research shows a relationship between WASH environments and school attendance and enrollment. Monetizing the benefits of improved schooling in a low-income country context is challenging due to high variation in school quality as well as high rates of self-employment.

Quality-of-life benefits for women are a third category of benefits that are often omitted from WASH cost–benefit analyses. Mostly qualitative research highlights that poor sanitation and water insecurity is associated with safety, security, privacy, and dignity concerns for women. While these concerns and experiences are difficult to quantify in many cases, they should not be ignored when considering WASH benefits.

Subjects

  • Environmental Health
  • Global Health

Introduction

Cost–benefit analyses (CBAs) of water, sanitation, and hygiene (WASH) interventions have traditionally focused on two primary benefits: improved child health outcomes from reduced fecal exposure and reduced time burdens (Cha et al., 2020; Hutton, 2013; Hutton et al., 2007; Radin, Jeuland, et al., 2020; Radin, Wong, et al., 2020). Typically, child health benefits are measured by reduced cost-of-illness from diarrhea and mortality risk reduction, while reduced time burdens are measured by time savings from shorter water collection times and/or time to defecation site. While there is a large evidence base for both of these benefits, there is also growing evidence that improved WASH provides additional nutritional, educational/cognitive, and quality-of-life benefits, particularly for women. Considering these benefits in future WASH CBAs is critical to understanding the full scope of benefits that WASH interventions may offer. This article, first, briefly introduces the potential mechanisms for each of these benefits, before reviewing the current state of the literature and discussing how future WASH CBAs might incorporate each of these benefits.

The reduced fecal exposure from improved WASH decreases the risk of environmental enteropathy, a “syndrome of inflammation, reduced absorptive capacity, and reduced barrier function in the small intestine” (Crane et al., 2015, p. 1). Epidemiological evidence has shown that environmental enteropathy can result in stunting as well as increasing the odds of being underweight (Griffiths & Kikafunda, 2015; Guerrant et al., 2016; Lin et al., 2013; Mbuya & Humphrey, 2016; Petri et al., 2014). If WASH improvements can produce long-term benefits such as reduced stunting, then existing WASH CBAs may miss important long-term economic benefits associated with linear growth (Galasso & Wagstaff, 2019). However, there is mixed existing causal evidence on whether WASH interventions do, in fact, reduce rates of stunting (Cumming et al., 2019; Hammer & Spears, 2016).

Environmental enteropathy may also affect the cognitive development of children. Stunting resulting from environmental enteropathy is significantly associated with lower cognition (Berkman et al., 2002; Fischer Walker et al., 2012; Tartelton et al., 2006). Furthermore, cognitive development may also be affected by low-weight children suffering from nutrient absorption issues (Jiang et al., 2014; Petri et al., 2008). There is a growing causal empirical literature linking WASH, particularly improved sanitation, to long-term cognitive development (Orgill-Meyer & Pattanayak, 2020; Spears & Lamba, 2016). Additional research suggests that improvements in WASH, and sanitation in particular, improve school enrollment and attendance outcomes (Orgill- Meyer, 2020; Santiago Ortiz-Correa et al., 2016).

Finally, WASH improvements provide quality-of-life improvements, particularly for women. Improved sanitation, relative to open defecation, has privacy and dignity benefits that are acutely felt by women. Furthermore, beyond the commonly acknowledged time costs associated with gathering water or traveling to and from open defecation sites, women also face risks of assault and rape during these trips. Given the difficulty in quantifying such benefits, they have often been ignored or overlooked in CBAs of WASH interventions.

This article reviews the current state of the literature on WASH-related nutritional, educational/cognitive, and empowerment benefits. Additionally, it seeks to provide guidance on how to best incorporate these potential benefits into future WASH CBAs. It is important to note a few caveats. First, this article focuses exclusively on the benefits of household-level WASH. While there is a growing literature on the educational benefits of school sanitation (Adukia, 2017; Sclar et al., 2017), the focus here is on household and community-level WASH literature that can be extrapolated to future CBAs focusing on WASH interventions at the household or community level. Second, most of the literature measuring these three types of benefits—nutrition, cognition/education, and quality of life for women—focuses primarily on sanitation. While such returns might exist for water and hygiene interventions as well, these benefits are less studied in those contexts, and thus this article focuses more on the potential benefits of improved sanitation. Finally, there are growing empirical literatures for each of these potential benefits, and this article primarily restricts its review to peer-reviewed publications.

Nutrition and Stunting

Reduced diarrheal disease from improved WASH environments has implications for child nutrition. Epidemiological evidence suggests that children in environments with high levels of diarrheal disease are more likely to lose nutrients due to diarrhea; expend energy fighting diarrheal disease; contract worm and parasitic infections; and experience inflammation in the gut, causing malabsorption of nutrients due to repeated infections (Checkley et al., 2008). Indeed, chronic environmental enteropathy or environmental enteric infection from repeated exposure to fecal material has been shown to reduce nutrient absorption capacity and contribute to childhood stunting (Cumming & Cairncross, 2016; Humphrey, 2009). Linear growth and stunting are widely used biomarkers of environmental enteropathy (Keusch et al., 2013; Korpe & Petri, 2012; Prendergast & Kelly, 2012; Syed et al., 2016). Large-scale ecological analyses suggest a significant relationship between open defecation prevalence and childhood stunting (Spears et al., 2013). Furthermore, improved sanitation environments may result in reduced childhood anemia due to increased absorption capacity (Coffey et al., 2017).

Despite these potential epidemiological pathways through which improved WASH may improve nutritional outcomes, studies quantifying these benefits—child height and stunting in particular—have shown mixed results. A number of recent studies in India have shown a positive causal relationship between improved sanitation environments and child height (Augsburg & Rodríguez-Lesmes, 2018; Dickinson et al., 2015; Hammer & Spears 2016). Vyas et al. (2016) and Pickering et al. (2015) presented similar evidence from Cambodia and Mali, respectively.

Earlier randomized control trials showed no effect of sanitation interventions on child height outcomes (Clasen et al., 2014; Patil et al., 2014); however, uptake and compliance was low in both studies (Cumming & Cairncross, 2016). Three more recent cluster-randomized control trials with different WASH arms show no impacts of any of the WASH intervention arms on linear growth, despite high compliance with the interventions (Humphrey et al., 2019; Luby et al., 2018; Null et al., 2018). Only one of these trials also produced any significant changes in diarrheal disease outcomes (Luby et al., 2018), suggesting that the WASH interventions on their own may not have induced enough of a change in the disease environments to affect linear growth outcomes (Cumming et al., 2019). One potential reason for the lack of observed impacts on linear growth was low baseline rates of open defecation in two of the studies (Luby et al., 2018; Null et al., 2018) in comparison to studies that found a positive relationship between improved sanitation environments and child height outcomes (Coffey & Spears, 2018).

Looking beyond sanitation, there have been very few studies that explore the relationship between water and/or hygiene and child height outcomes. One randomized control trial of a solar disinfection intervention in Kenya found significant improvements to height-for-age Z-scores (Du Preez et al., 2011). Both Luby et al., 2018 and Null et al., 2018 found that the chlorine disinfection arms of their study had no significant impact on height-for-age Z-scores, though the combined water, sanitation, and hygiene arms did result in significant improvements. Other research investigating the role of water and/or hygiene on child height tends to be cross-sectional in nature (Rah et al., 2015; Torlesse et al., 2016), making it difficult to tease out the role of potential confounding factors.

Given the role that WASH, and sanitation in particular, may play in reducing malnutrition and stunting, how should analysts account for these benefits in cost-benefit analyses? Evidence suggests that even universal coverage of improved sanitation is insufficient on its own to eliminate childhood stunting (Bhutta et al., 2013). Table 1 summarizes the quasi-experimental and experimental studies discussed previously studying the effect of sanitation on child height to highlight the range of effect sizes observed in the literature. Taken together, the collective evidence suggests that a lower bound for the effect of improved sanitation on child height outcomes is zero. However, studies may have been limited in their ability to observe statistically significant effects due to low adherence and persistent open defecation (Patil et al., 2014) and/or low rates of baseline open defecation (Luby et al., 2018; Null et al., 2018). In the literature showing positive effect sizes, improvements to the sanitation environment (increases in sanitation coverage ranging from 10% to 100%) are shown to increase height-for-age Z-scores by 0.17 to 0.52 standard deviations.

Table 1. Summary of Existing Research (as of 2022) of Sanitation Interventions on Height-for-Age and Stunting Outcomes

Study

Location

Independent Variable of Interest

Change in Independent Variable Observed Due to Intervention

Outcome Variable

Observed Effect Size

Clasen et al. (2014)

Odisha, India

Village-level latrine coverage

Intervention villages: 9% to 63%a Control villages: 8% to 12%

Height-for-age Z-score

No significant effect

Patil et al. (2014)

Madhya Pradesh, India

Village-level latrine coverage

Intervention villages: 13% to 41% Control villages: 12% to 22%

Height-for-age Z-score

No significant effect

Dickinson et al. (2015)

Odisha, India

Village-level latrine coverage

Intervention villages: 7% to 35% Control villages: 15% (no change)

Height-for-age Z-score

Between 0.37–0.52 in one-year period

Pickering et al. (2015)

Rural Mali

Cluster-level latrine coverage

Intervention clusters: 33% to 64% Control clusters: 35% to 34%

Height-for-age Z-score, prevalence of stunting and severe stunting

HAZ SD: 0.18 Reduction in stunting: 6% in two-year period

Hammer and Spears (2016)

Maharashtra, India

Village-level latrine coverage

Intervention villages: 6% to 22% Control villages: 5% to 14%

Height-for-age Z-score

Between 0.37–0.44 in one-year period

Vyas et al. (2016)

Cambodia

Local open-defecation rates

No intervention—estimated effect from moving from 100% open defecation to 0% open defecation

Height-for-age Z-score

Between 0.3–0.5 in five-year period

Augsburg and Rodríguez-Lesmes (2018)

Madhya Pradesh, India

Village-level latrine coverage

No intervention—estimated effect from a 10% increase in sanitation coverage

Height-for-age Z-score

0.17

Luby et al. (2018)b

Rural Bangladesh

Cluster-level coverage of latrines with a functional water seal

Intervention clusters: 30% to 97% Control clusters: 31% to 31%

Length-for-age Z-score, prevalence of stunting and severe stunting

No significant effect

Null et al. (2018)b

Western Kenya

Cluster-level coverage of improved latrine

Intervention clusters: 16% to 78% Control clusters: 17% to 20%

Length-for- age Z-score

No significant effect

Humphrey et al. (2019)c

Rural Zimbabwe

Received WASH intervention (included providing study latrines to intervention households)

Intervention clusters: 36% to 99% any latrine ownership Control clusters: 33% to 43% any latrine ownership

Length-for-age Z-score

No significant effect

a While village-level latrine coverage increased substantially in treatment villages, the coverage of functional and usable latrines was noticeably smaller: 38% functional latrines and 36% latrines with indications of present use in treatment villages.

b These cluster-randomized control trials all had other WASH intervention arms. For the purposes of comparison with other studies in the table, only the sanitation arms are reported here. In each of the studies, there was no observed effect with any of the WASH intervention arms and child height.

c This study had only combined WASH intervention arms with no independent sanitation arm.

The economic and monetary benefits of reduced childhood stunting are well-documented. Early-life stunting is strongly associated with poorer cognitive development (Kar et al., 2008) and lower educational attainment (Victora et al., 2008). Furthermore, growth failure early in life is strongly correlated with adult height (Alderman, 2010; Coly et al., 2006; Stein et al., 2010), and adult height is an important predictor of labor market outcomes (Deolalikar, 1988; Schultz, 2002; Thomas & Strauss, 1997). Because of these well-documented benefits, there is already a strong literature discussing the economic costs of early-life stunting and delayed growth (Alderman, 2010; Fink et al., 2016). Research from nutritional interventions found large long-term economic returns (Hoddinott et al., 2008; McGovern et al., 2017).

From one such nutritional intervention in Guatemala, researchers used instrumental variables to account for endogeneity of child height and found that a one-standard-deviation increase in height-for-age at 36 months of life increased hourly adult earnings by 14.8% and total per capita consumption by 19.5% (Hoddinott et al., 2011). They also found that per capita adult consumption was 66% lower among children who were stunted at 36 months of age compared to those who were not stunted (Hoddinott et al., 2011). Galasso and Wagstaff (2019) used a development accounting approach to compare countries with different levels of stunting and estimated a much lower benefit than what was found in the Hoddinott et al. (2008) and Hoddinott et al. (2011) studies. They found that adults who were stunted in childhood face an average income penalty of 5%–7% (Galasso & Wagstaff, 2019).

McGovern et al. (2017) provided a review of the literature on stunting and economic outcomes to consolidate estimates across several randomized control trials, quasi-experimental studies, and observational studies. They found that, on average, across these studies, a 1-cm increase in adult height is associated with a 4% increase in wages for men and a 6% increase in wages for women (McGovern et al., 2017). Combining these estimates with a study from Ghana showing that reduced childhood stunting is associated with a 6-cm gain in adult height (Schultz, 2003), Aryeetey et al. (2020) concluded that a reduction in childhood stunting results in an 30% increase in adult income.

Combining the range of potential effect sizes for child height returns from sanitation interventions with the economic literature on returns from reduced stunting introduced here provides researchers and policymakers with a way of incorporating nutritional and reduced stunting benefits into cost-benefit models of WASH interventions.

Cognitive and Educational Benefits

Cognition

To date, there are two categories of research that study the causal impacts of improved WASH on cognitive development: (a) studies of early-childhood exposure to improved WASH on medium- to long-term cognitive development and (b) studies of in utero childhood exposure to improved WASH on short-term cognitive development. The existing studies in these areas are summarized in Table 2.

Both studies that examined how improved WASH in early childhood affects medium- to long-term cognitive development took place in India. Spears and Lamba (2016) examined whether children living in districts exposed to the Total Sanitation Campaign (TSC) in India at age zero performed higher on reading and math test scores at six years of age compared to children born in the same district in different years or in different districts in the same year. Using measures of intensity of the TSC allowed the authors to identify which districts experienced greater latrine coverage during roll-out of the TSC. Results from a difference-in-differences estimation reveal that children in districts with more TSC latrines per capita at age zero were better able to recognize letters and numbers at age six. Orgill-Meyer and Pattanayak (2020) similarly found positive long-term effects of early childhood exposure to improved sanitation in India. They measured the effects of a randomized control trial (RCT) that increased village latrine coverage (Pattanayak et al., 2009) on child cognitive test scores ten years later. Children ages 7–15 in villages receiving the sanitation intervention scored significantly higher on the Raven’s Colored Progressive Matrix Test than children in control villages. Importantly, these effects were observed only for girls; there was no difference in boys’ test scores between treatment and control villages.

The research on in utero exposure to short-term cognitive development has more mixed findings. Stewart et al. (2018) and Tofail et al. (2018) conducted cluster-randomized trials in Kenya and Bangladesh, respectively, in which pregnant women in their second and third trimesters were recruited and babies born to these women completed the Extended Ages and Stages Questionnaire (EASQ) at age 2. Both studies divided their clusters into six treatment arms: chlorinated drinking water, improved sanitation, handwashing with soap, combined WASH, improved nutrition, and combined WASH + nutrition. By age 2, Stewart et al. (2018) found no differences in EASQ scores between children in any of the treatment arms and the control arms. This study suffered from very high attrition (27% of children at year 2), which may affect the validity of the findings. Tofail et al. (2018), however, found positive and statistically significant effects for all of the treatment arms, with the largest effects in the combined WASH + nutrition groups and the smallest effects in the chlorinated drinking water groups. They also found positive effects of intervention arms on the MacArthur Bates Communicative Development Inventories but found no statistically significant effects on measures of executive function. Gladstone et al. (2019) conducted a similar study in Zimbabwe with three intervention arms—combined WASH, nutrition, and WASH + nutrition. They found modest effects of the WASH intervention on the MacArthur Bates CDI when controlling for other mother, household, and child characteristics. However, there was no effect of the WASH intervention on the other cognitive assessments.

Given the different results these studies produced, it is important to think carefully about potential inclusion of cognitive gains as benefits in WASH CBAs. Research in both economics and psychology shows that cognitive advantages in early life have persistent effects on future earnings (Knudsen et al., 2006). Ideally, data would exist examining how improvements in each of the cognitive assessments discussed are associated with future adult earnings. However, to date there is no research measuring the association of the childhood cognitive assessments used in these WASH studies and future earnings, making it challenging to identify parameters to use as cognitive benefits in WASH CBAs. Hanushek (2009) provided an overview of the literature presenting returns to improvements in cognitive skills, though the cognitive skills in the studies all are measured at adulthood, and thus are not directly relatable to the WASH studies discussed here. Importantly, because many of the benefits from improved cognition are linked to decreased stunting, counting both returns to stunting and cognition in WASH CBAs will likely result in some degree of double-counting benefits.

Table 2. Summary of Existing Research (as of 2022) of Causal Research on Sanitation and Cognition

Article

Country

Sample

Study Design

Age of Exposure to Improved WASH

WASH Intervention(s)

Age of Cognitive Assessment

Type of Cognitive Assessment

Findings

Spears and Lamba (2016)

India

47,612 children

Difference-in-differences

Early childhood

Improved sanitation (district-level)

Age 6

Reading and math tests

Positive and statistically significant effect

Orgill-Meyer and Pattanayak (2020)

India

1,825 children

RCT long-term follow-up

Early childhood

Improved sanitation (village-level)

Ages 7–15

Raven’s Colored Progressive Matrix

Positive and statistically significant effect

Stewart et al. (2018)

Kenya

6,107 children from 702 clusters

Clustered RCT

In utero

Chlorine treatment of drinking water; improved sanitation; handwashing with soap; combined WASH; WASH + nutrition

Age 2

Extended Ages and Stages Questionnaire (EASQ)

Some differences observed at age 1, but no differences observed after age 2

Tofail et al. (2018)

Bangladesh

4,403 children from 720 clusters

Clustered RCT

In utero

Chlorine treatment of drinking water; improved sanitation; handwashing with soap; combined WASH; WASH + nutrition

Age 2

Extended Ages and Stages Questionnaire (EASQ); MacArthur Bates Communicative Development Inventories; Executive Function

Positive and statistically significant effect for EASQ scores in all intervention groups

Gladstone et al. (2019)

Zimbabwe

1,655 children

Clustered RCT

In utero

Combined WASH

Age 2

Malawi Developmental Assessment Tool (MDAT); MacArthur-Bates Communicative Development Inventories; A-not-B test

No statistically significant effects for any of the assessments

School Attendance and Educational Attainment

In a systematic review by Sclar et al. (2017), the authors posited two mechanisms through which improved sanitation may affect school outcomes. First, improved household or community sanitation means that children face lower rates of fecal exposure and thus lower rates of infection and illness, thus increasing their ability to attend school. These lower rates of infection and illness may also directly contribute to improved cognitive development, as discussed. Cognitive development is also likely to be enhanced through improved school attendance. Second, school sanitation provides a more comfortable learning environment and thus increases the desire to attend school. This article focuses exclusively on the first mechanism, which considers household and community sanitation, though there is a growing body of literature on the educational benefits of school sanitation (Adukia, 2017; Garn et al., 2013). Finally, while Sclar et al. (2017) focused their review exclusively on sanitation, the mechanisms of reduced fecal exposure and thus reduced rates of infection and illness are likely to also apply to improvements in household water and hygiene.

Most studies to date focusing on household WASH and educational outcomes considered both water supply and sanitation factors. Water supply may affect educational outcomes due to the time costs of water collection. Dreibelbis et al. (2013) examined how different household WASH characteristics correlate with school absences in western Kenya. They found that further water sources (greater than 20 minutes from the household) are associated with an increased likelihood of school absences for both girls and boys, while involving children in water collection is associated with an increased likelihood of school absenteeism only for girls. In this study, household latrines are associated with a decreased likelihood of school absence for boys only.

Other studies use a mix of quasi-experimental techniques to attempt to identify the causal impact of water supply and sanitation on school outcomes. Rauniyar et al. (2011) used propensity score matching to identify the effects of a program that rehabilitated water supply and drainage systems as well as provided hygiene education in rural Pakistan. They found that the project improved school attendance for adolescent-aged girls, which they attributed to the reduced time costs associated with fetching water. Klasen et al. (2012) showed a contrary result for an improved water supply program in Yemen. Using a range of quasi-experimental methods, they found that improvements in water supply actually decreased school attendance. They also showed that the water supply improvements resulted in increased rates of diarrhea incidence, suggesting that the water supply intervention may have decreased water quality, thus resulting in higher rates of fecal exposure and infection. On the other hand, a randomized control trial of improved access to credit for piped water connections in Morocco showed no impact on school attendance (Devoto et al., 2012).

One of the primary mechanisms through which improved water supply may affect schooling outcomes is through reduced water-fetching times. There are a number of studies that examine this relationship directly. Nauges and Strand (2017) used constructed panel data from Ghana’s Demographic and Health Surveys to estimate that halving water collection time increases school attendance by 7%. Using an instrumental variables technique, Hamlet et al. (2021) found that higher water-fetching times reduce school test scores for girls, in particular. They attributed this finding to the likelihood of water fetching affecting school attendance for girls. A randomized control trial of water deliveries in Kenya provided further evidence of the relationship between water fetching and school attendance. In this study, children who belonged to treatment households that were randomly assigned to receive water deliveries increased school attendance by 3.6%, on average (Cook et al., 2021).

Rather than examining effects on school attendance, Santiago Ortiz-Correa et al. (2016), showed that access to water and sanitation services in Brazil increases the total number of years of schooling. Similarly, Orgill-Meyer (2020) found that higher village-level latrine coverage is correlated with reduced school dropout rates for girls in India. A study on the effects of clean water on school outcomes in Indonesia indicated that household access to private water facilities is correlated with higher school enrollment and lower school absenteeism (Komarulzaman et al., 2019).

There has been considerable research quantifying and monetizing the returns to additional schooling (Card, 1999; Carneiro et al., 2011; Harmon & Walker, 1995; Trostel et al., 2002). Recent estimates for high-income countries are 1.9% lost lifetime earnings for losing one quarter of a school year and 7.7% lost lifetime earnings for a full school year (Hampf et al., 2017; Hanushek & Woessmann, 2020). Similar estimates are more challenging to obtain for low-income countries because of higher variance in school quality and the large proportion of self-employment in the labor force (Glewwe, 2002). For these reasons, in a low-income country context, much of the research shows that skills and cognitive test scores are more predictive of earnings than educational attainment (Al- Samarrai & Reilly, 2008; Alderman et al., 1996; Boissiere et al., 1985; Glewwe, 1996).

Despite these challenges, there is a large body of literature estimating large returns to educational attainment in a low-income context (Psacharopoulos, 1994; Psacharopoulos & Patrinos, 2010, 2018), though this literature is not always able to fully account for the issues previously discussed. Indeed, Glewwe and Jacoby (1994) found that improvements to school quality that increase grade attainment have strong economic returns; they estimated a 4%–6% return to one additional year of schooling in Ghana. A voucher program for private primary schools in Colombia increased the rate of tertiary education attainment; voucher winners had annual incomes that were 8% higher than non-voucher winners 20 years later (Angrist et al., 2002; Bettinger et al., 2019). Similarly, (Duflo, 2001) found that a school construction project in Indonesia increased total educational attainment by 0.12 to 0.19 years, which resulted in a 1.5%–2.7% increase in wages. However, with each of these studies, it is difficult to disentangle whether improvements to school quality or school attainment drove the economic returns. One recent study found that while free scholarships for secondary schools did increase educational attainment in Ghana, there were no long-term effects on earnings between those who received the scholarship and those who did not (Duflo et al., 2021). However, the confidence intervals on these effect sizes are quite large, and so the null result should be taken in the context of the broader literature discussed. In their most recent review of over 1,120 global estimates in 139 countries, Psacharopoulos and Patrinos (2018) estimated that the average private return to an additional year of schooling is 9% per year, and that this return is higher for women than men. This literature on the economic returns to additional schooling can help researchers and policymakers incorporate the benefits of improved cognition and educational attainment into WASH CBAs, with the caveat that school quality, which varies greatly in low-income countries, plays an important mediating role in realizing these monetary returns (Glewwe, 2002).

Quality of Life for Women

In addition to the nutrition, cognitive, and educational benefits that WASH may offer, there is also a growing literature documenting gender-specific benefits. Historically, this literature has focused primarily on the time-saving benefits of reduced water collection from improved water supply or reduced time to defecation sites from improved on-site sanitation options. More recently, research has found that open defecation causes a variety of psychosocial stressors for women. Indeed, women who rely on open defecation or shared community latrines report fear of being victim to crime or robberies (Khanna & Das, 2016; Shiras et al., 2018; Winter et al., 2018), physical violence (Abu et al., 2019; Kwiringira et al., 2014; Routray et al., 2015), and sexual assault (Hulland et al., 2015; Shiras et al., 2018). Additional research reports women feeling a loss of dignity and privacy from open defecation or shared latrine use (Azeez EP et al., 2019; Caruso et al., 2017; Schmitt et al., 2017).

There are some notable quantitative studies measuring the relationship between water access and quality of life measures for women. Choudhary et al. (2020) found that poor water access is positively associated with increased intimate partner violence in Nepal, perhaps due to women’s inability to complete certain household tasks such as cooking and cleaning that rely on water. This finding remains after controlling for a suite of covariates that might also affect intimate partner violence. Using a randomized control trial of access to credit for water connections in Morocco, Devoto et al. (2012) found that improved water access increases leisure time for women and reduces intra-household conflicts about water. Furthermore, women in households with higher levels of water insecurity are more likely to report being stressed and to score higher on depression scales (Aihara et al., 2016). Using an experience sampling method in Kenya, Cook et al. (2022) found that primary water collectors report lower levels of happiness, safety, and energy while participating in water-collecting activities. A randomized control trial of in-home water delivery confirmed these findings; individuals in households that were randomly assigned to receive water deliveries report higher levels of happiness, safety, and energy (Cook et al., 2021).

Reducing physical and sexual violence and providing improved safety, privacy, and dignity for women are obvious benefits that should be considered by policymakers considering WASH interventions. However, much of the research done in these areas to date is qualitative in nature, making it difficult to assess the extent to which switching to improved on-site sanitation options reduces the risk of physical and sexual violence. Where there is quantitative research, it is often cross-sectional and associational in nature, and the benefits are difficult to monetize. Thus, systematically including these benefits in a cost-benefit analysis is challenging. However, such benefits should not be ignored, and at the very least should be included as a benefit that is not quantifiable. For WASH interventions that do not appear to produce positive net benefits based on cost-benefit analyses, policymakers should consider whether such interventions are likely to provide some of the gender-specific benefits discussed in this section.

Conclusions

There is a growing body of research exploring WASH-related benefits that extend beyond the traditionally considered benefits of reduced diarrheal disease and time savings. Reduced fecal exposure from WASH interventions may decrease the risk of environmental enteropathy, resulting in nutritional status improvement. Causal research has provided mixed evidence for the direct link between improved sanitation, in particular, and stunting, though intervention adherence and baseline open defecation rates seem to play an important role in observing such a relationship. Beyond stunting, epidemiological evidence suggests that reduced environmental enteropathy can improve cognitive development, and indeed new research has established a direct causal relationship between sanitation environments and children’s subsequent cognitive development. Decreased illness incidence from reduced fecal exposure also seems to improve children’s educational outcomes, with improved household or community water and sanitation services being linked to increased school enrollment and decreased absenteeism. Finally, recent qualitative literature has shown that both sanitation and water security can have important quality-of-life benefits for women in particular. Women practicing open defecation or using shared latrines report concerns about theft, physical violence, and sexual assault. Women in households with high levels of water insecurity are more likely to face intimate partner violence and depression.

Incorporating the wide-ranging benefits of WASH interventions into systematic CBAs can be challenging. Much of the literature is still new, so analysts must rely on relatively few studies for ranges of plausible benefits. While existing economics literature has produced credible monetary estimates for the returns of increased stunting and increased educational attainment, there are fewer estimates that monetize the benefits of improved cognition and reduced concerns of physical or sexual assault. Based on the available literature, CBA practitioners should incorporate stunting and educational attainment benefits into sensitivity analyses of WASH CBAs. Additional research is needed to monetize the benefits of improved cognition and improved quality of life for women. However, it is important for analysts to flexibly consider these types of benefits as potentially non-monetizable benefits in WASH CBAs, that likely still enlarge the net present value of WASH interventions.

Further research both quantifying and monetizing these types of benefits is needed to add additional credibility to the range of potential benefits. Research on cognitive returns to WASH interventions and the monetary returns associated with particular cognitive measures is particularly needed. Additionally, while there has been excellent qualitative research exploring women’s safety and privacy concerns with open defecation and shared sanitation, quantitative research is needed to measure how much improved sanitation decreases risks of physical and sexual violence. Finally, in all of these domains—nutrition and stunting, cognition and education, and quality of life for women—the majority of research focuses on improved sanitation. Future research should explore the extent to which improved water supply, improved water quality, and hygiene interventions might also produce similar returns.

Further Reading

References