Global water-aid projects have greatly expanded access to drinking water in underserved regions. The recent $40 million TeamWater campaign built hundreds of wells in more than 20 countries, including Bangladesh, Colombia, and Nigeria (1, 2). These gains are impressive, but wells may be drawing from shallow aquifers that are easily polluted by farm runoff, leaking septic tanks, industrial waste, and seawater intrusion. Today, at least 1.7 billion people use drinking-water sources contaminated with feces, which may include groundwater sources (3). Without safeguards, wells that are intended to improve health could instead deliver harm.
