Résumé

In developing countries, untreated sewage exposes people to alarming water pollution levels, yet there is limited knowledge about the effectiveness of wastewater treatment investments. I evaluate the impact of wastewater treatment on water quality and infant mortality in India, exploiting the staggered introduction of urban sewage treatment plants over the period 2010-2020. I match granular data on sewage treatment plants, river water quality, as well as child births and deaths using the hydrological network. I show that after initiating wastewater treatment, levels of fecal coliforms – a commonly used measure of fecal contamination in water – decreased by 53% (95% CI: [7; 99]). Mortality under the age of six months – a critical period for digestive system development – declined by 20% (95% CI: [3; 36]) downstream of the plants, with larger effects observed for boys and children from the lowest wealth quintiles. The results are consistent across several estimators robust to heterogeneous treatment effects, are not driven by selective migration, and are found only downstream of the plants, which rules out confounding effects from other local policies. Wastewater treatment is cost-effective according to GDP-based thresholds, with a cost of INR 6 million per life saved and INR 85,000 per DALY averted for children under six months.

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