The Benefits of These Interventions Are Greater Than the Health Benefits Alone

Environmentally caused mortality and malnutrition have substantial economic costs. In Ghana and Pakistan, for example, the indirect effect on child mortality of environmental risk factors mediated by malnutrition adds more than 40% to the cost of directly caused child mortality (Figure 4) [22]. If one takes into account the effect of such malnutrition on impaired school performance and delayed entry into the labour market, the cost doubles to 9% of gross domestic product (GDP). With the possible exceptions of malaria and HIV/AIDS in Africa, it is hard to think of another health problem so prejudicial to household and national economic development.

Figure 4. The cost to two national economies of inadequate HSW.

The “direct” effect is mortality attributable to these environmental risk factors, “indirect” effect includes mortality mediated by environmentally caused malnutrition, and “education” includes the effects of that malnutrition on (i) grade attainment; (ii) school achievement (learning productivity) in terms of grade equivalents; (iii) delayed primary school enrolment; and (iv) grade repetition. The latter two effects result in delayed labour force entry. Source: [22].

doi:10.1371/journal.pmed.1000367.g004

Lack of sanitation also leads to intestinal helminth infections, which cause stunting, late entry to school, and impaired cognitive function [23],[24]. Furthermore, inadequate sanitation and water supply are associated with much loss of time spent on water collection or seeking a place to defecate. An analysis of survey data from 39 African countries showed that for 160 million people (many of them women), collection of each container of water took substantially more than 30 minutes [4],[25]. A World Bank study [26] found that, even ignoring the effect of water supplies on health, the value of time saved from water collection alone was sufficient to justify investments in rural water supply in most settings. Finally, a WHO report suggests that the time lost in collecting water and seeking somewhere to defecate could be valued at US$63 billion annually [27].

When all these benefits are accounted for, many HSW investments yield a net benefit in the range US$3–46 per dollar invested [19],[27], and some additional benefits remain unquantified. For example, there are suggestions that sanitation and water supply boost school attendance and reduce dropout rates—presumably in part by reducing the demand on children's time to collect water. Well-run sanitation facilities in schools might also help to prevent girls from dropping out after menarche [28]. Overcoming such constraints to education can yield real benefits. Thus, at the beginning of the 20^thcentury, 40% of schoolchildren in the southern US were infected with hookworm. When the disease was eradicated early in the century, school enrolment, attendance, and literacy increased, and there was a long-term gain in incomes [29].

These benefits are substantive at macroeconomic as well as household levels, as shown by the World Bank study cited above [22], and by a study for the Commission on Sustainable Development. This second study found that the per capita GDP growth of poor countries with improved access to water and sanitation was much higher than that of equally poor countries without improved access (3.7% and 0.1%, respectively) [30].