<mark>other stakeholders, sewage and organic solid wastes are some of the fastest growing sources of nitrogen pollution in the country (INA, 2017).</mark> Most previous work that provides causally interpretable estimates has primarily focused on short‐run and immediate birth outcomes (Brainerd and Menon, 2014; Jones, 2019).<sup>4</sup> These studies show that early‐life exposure to nitrogen‐related pollution can lead to infant mortality (Brainerd and Menon, 2014) and low birthweight (Jones, 2019). The well‐established fetal origins literature suggests that intrauterine health impacts can lead to lasting health damages, and that low birthweight is associated with shorter height in adulthood (Barker, 1990; Almond and Currie, 2011; Currie and Vogl, 2013; Christian et al., 2013; Almond, Currie and Duque, 2018). And low birthweight is a well‐known marker for many health problems later in life, including coronary heart disease (Barker 1995), decreased glucose tolerance (and thus a higher propensity for obesity) (Ravelli et al. 1998), and increased rates of all‐cause mortality (Risnes et al. 2011). Still, there has been no attempt to quantify the full extent of health damages, especially the irreversible and lagged human capital impacts, as a result of nitrogen pollution in water.

Evidence for lagged human capital impacts in environmentally vulnerable and poor locations is severely limited due to the paucity of longitudinal data that can trace long‐term impacts. This is particularly challenging for water pollution, since monitoring of water quality is sparse in space and time and is site‐specific. In this paper, we exploit temporal and geographic variation in nitrogen pollution exposure with a newly constructed database of water quality that combines in situ monitoring station data with a geospatial statistical model for stream networks developed by ver Hoef and Peterson (2010). We carefully integrate early‐life exposure to nitrogen pollution between the critical years of development – from the period of birth up until year three – with women’s health outcomes, climatic factors, correlated pollutants, household inputs and other socioeconomic demographics for our analysis.

Our research design exploits the direction of river flow and the upstream‐downstream geographic relationship used in past literature (Do et al. 2018; Garg et al. 2016) to estimate a pollution‐health relationship. Because the costs imposed by water pollution are largely felt in downstream regions, the analysis focuses on the impact of upstream pollution on health outcomes in downstream regions. To isolate the average pollution spillover at downstream locations, the analysis uses a rich set of controls. These are meant to control for time‐invariant, location‐specific characteristics such as local soil quality and natural resource endowments, as well as factors that vary by year and month, such as weather, and national trends in economic

> 4 A number of biomedical and epidemiological studies in the United States and other countries have documented a relationship between agrichemical exposure and birth defects such as Down’s syndrome and Spina Bifida, especially for children conceived during the crop-sowing months, and among children of agrichemical applicators who are consistently exposed to toxins.

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