Human health is essential to economic activity, and is often compromised in developing countries due to poor nutrition and exposure to pollution. Ill-health causes loss of income both for the victim and for family members that need to care for them or pay for their treatment. In Bangladesh, the principal source of drinking water for households - tube wells - contains water often contaminated with inorganic arsenic, a toxic pollutant that can affect digestion and inhalation, and cause diarrhea and organ failure. This project identifies how the ingestion of inorganic arsenic causally affects health, productivity and incomes at the individual level based on newly-acquired survey data on members of rural households throughout the country. The study is based on the latest round of a large-scale longitudinal survey of 13,000 individuals in 2,480 households who originally resided in 14 villages in Bangladesh in 1982, in which for each respondent aged eight years and above clippings from all ten toenails were collected. Our study exploits variation in food prices over time and space, information on kin who reside in different households, and the known genetic links in arsenic metabolism to identify from non-experimental data how reductions in arsenic contamination would improve productivity, incomes and health. By understanding how interventions or improved diet reduce the toxic effects of arsenic exposure and how arsenic contamination in humans causally affects health and productivity, we will be better able to conduct cost-benefit analyses of governmental programs to alleviate the effects of environmental arsenic exposure. Moreover, because income growth changes the composition of food intakes, improved knowledge of the nutrition-arsenic link can help us forecast some of the health consequences of economic growth.