The 1994 discovery of arsenic in groundwater in Bangladesh prompted a massive public health campaign that led 20% of the population to switch from backyard wells to less convenient drinking water sources that had a higher risk of fecal contamination. We find evidence of unintended health consequences by comparing mortality trends between households in the same village that did and did not have an incentive to abandon shallow tubewells. Post-campaign, households encouraged to switch water sources have 46% higher rates of child mortality than those not encouraged to switch. Switching away from arsenic-contaminated wells also increased adult mortality.