IN many parts of the world, including Africa, people rely on rainwater as a source of drinking water, as well as for other household and livelihood uses. One of the reasons is water scarcity – sub-Saharan Africa has the largest number of water-scarce countries in the world. But there are concerns about how safe rainwater is to drink. It can be contaminated by dust and ash in the surroundings or by heavy metal from roofing material. Another concern is the presence of manufactured chemicals called perfluoroalkyl and polyfluoroalkyl substances (PFAS), or “forever chemicals”. As environmental scientist Ian Cousins and his…