Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are chemicals used in consumer products since the 1940s, and studies show they are pervasive in drinking water across parts of the USA. A study by Shiwen Li and colleagues, published on Jan 9, 2025, analysed data from nearly half of the US population to support a link between exposure to PFAS-contaminated drinking water and cancer incidence. The study found significant associations between PFAS in drinking water and cancers affecting the endocrine, digestive, and respiratory systems, and the oral cavity, pharynx, and skin.