Is urban wastewater treatment effective in India? Evidence from water quality and infant mortality

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 leverage the national inventory of sewage treatment plants in India and various granular datasets on river water quality measures, as well as geo-localized information on child births and deaths, to identify robust effects of wastewater treatment installations. To do so, I use estimators robust to staggered adoption within a difference-indifferences design and compare urban areas that started wastewater treatment from 2010 onwards and urban areas where such treatment was planned or under construction in 2020. I show that after starting wastewater treatment, levels of fecal coliforms decreased by 50%, and downstream mortality under the age of six months declined by 20%. A back-of the-envelope calculation suggests that starting wastewater treatment earlier-from 2010 onwards-in urban areas later selected into treatment-after 2020-would have prevented over 40,000 child deaths in downstream sub-basins.