While open defecation has declined only very
slowly in India, other countries have experienced faster improvements in WASH, which has some- times contributed to improvements in child nutri- tion. Below, we review new evidence from such periods of rapid improvement in sanitation and highlight emerging biological research that is help- ing researchers beter understand the mechanisms of the nutritional effects of WASH. We will especially focus on evidence that has emerged in the past year. Te chapter particularly focuses on the links
between WASH and child height. A child’s height reflects her health and nutrition in her first few years of life, including in utero. Tis is because children with a healthier start in life come closer to achieving their genetic potential height. Height is a marker for the development of bodies, brains, and skills—all of which are influenced by health and nutrition. On average, children who have the early health that allows them to grow taller are also likely to grow into health- ier, more productive, and longer-lived adults. Te average size of children predicts the health and human capital of the next generation of workers and parents.3 Tus, the impacts of WASH on child height are critical.
JUSTIFICATION FOR ACTION
Te evidence base is now sufficient for policymak- ers to invest in improving WASH in contexts where exposure to fecal pathogens is an important threat to child nutritional outcomes. Much of this evidence comes from studies of entire populations—includ- ing both the current experiences of modern develop- ing countries and the sanitary history of developed countries. Tis is appropriate because the effects of sanitation are population-level processes, where neighbors influence neighbors. Demographers, epi- demiologists, and historians first documented the importance of fecal germs by studying urbanizing Europe.4 A new analysis of more than a century of adult male heights in 15 European countries found that the most important cause of the historical increase in European height was improvement in the disease environment.5 Disease still maters for nutritional outcomes
in developing-country populations today. Prelimi- nary research suggests that during the past 40 years,
20 WHY SANITATION MATTERS FOR NUTRITION
improvements in water and sanitation have been one of the key drivers in reductions in child stunting across 116 countries.6 However, many countries still face a threatening disease environment. Demographic and Health Survey data show that differences in exposure to open defecation can statistically explain more than half of the variation in average child height across developing countries.7 Moreover, new research suggests that the longstanding puzzle of the “Asian enigma”—that children in India are shorter, on aver- age, than much poorer children in Africa south of the Sahara—can be entirely statistically accounted for by the much greater density of open defecation to which children are exposed in India.8
Evidence from Changes in Bangladesh Open defecation has fallen dramatically in Bangla- desh over recent decades—from 34 percent of peo- ple defecating in the open in 1990 to 2.5 percent in 2012, according to data provided jointly by UNICEF and WHO. Tis important change has provided researchers with a special opportunity to investigate the nutritional consequences of changes in exposure to poor sanitation. Te fast improvement in child height in Bangla-
desh over recent years has been called the “other Asian enigma.” Particularly given that nutritional improvements in neighboring India have been so slow, why have children in Bangladesh grown so much taller so quickly?9 Data suggest that, along- side improvements in overall economic well-being and in parents’ education, a reduction in the amount of open defecation to which children are exposed is among the important factors that can account for the improvement over time in average child height.10 Other recent research on Bangladesh uses Geo-
graphic Information System data to study differ- ences in child height within small geographic areas. Tese studies pay special atention to an interaction between sanitation and population density because open defecation maters more for infant mortal- ity and child height where population density is greater.11 Bangladesh is relevant because population density is extremely high, and open defecation has declined dramatically. Evidence points to a strong association between reductions in the density of open defecation and improvements in child height.
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