The fallout of nitrogen pollution is considered one of the largest global externalities facing the world, impacting air, water, soil, and human health. This paper combines data from the Demographic and Health Survey data set across India, Vietnam, and 33 African countries to analyze the causal links between pollution exposure experienced during the very earliest stages of life and later-life health. The results show that pollution exposure experienced in the critical years of development-from birth until age three-is associated with decreased height as an adult, a well-known indicator of overall health and productivity, and is robust to several statistical checks. Because adult height is related to education, labor productivity, and income, this also implies a loss of earning potential. The analysis begins within an assessment in India, where the data are more available, and is then extended to geographic settings including Vietnam and 33 countries in Africa. The results are consistent and show that early-life exposure to nitrogen pollution in water can lower height-for-age scores during childhood in Vietnam and during infancy in Africa. These findings add to the evidence on the enduring consequences of water pollution and identify a critical area for policy intervention.