Substantially underestimated PFAS pollution in diverse Ghana’s land-use types revealed by a refined TOP assay

Per- and polyfluoroalkyl substances (PFAS) research in developing countries has largely focused on imported sources such as e-waste, but contributions from local land-use activities remain poorly understood. This study selected Ghana as a model to investigate PFAS contamination in sediments from riverine ecosystems across four land-use types: mining, municipal & electronic waste, and agriculture. In addition to conventional target analysis, we refined the direct total oxidizable precursor (dTOP) assay by applying direct oxidation to sediments, with the highest PFAS yields achieved using an eightfold increase in oxidizing agents. Target PFAS concentrations were relatively low, likely reflecting the impact of global regulations, but post-dTOP concentrations increased by 239-65,400% across all sites, ranging from 27.7 to 112 ng/g. Over 99% of detected PFAS were attributed to previously untargeted precursors, emphasizing the iceberg nature of PFAS contamination, where routine methods capture only a small visible fraction. Mining and agricultural areas showed higher PFAS levels than the e-waste zone, suggesting that locally driven sources are dominant contributors. The tailored dTOP approach proved essential in revealing these hidden PFAS burdens, highlighting the need for broader monitoring frameworks to inform environmental risk assessment and sustainable land-use management in developing regions. • Direct TOP assay on sediments produced PFAS concentrations an order of magnitude higher than assays on extracts. • Optimizing oxidant and alkali dosages is critical, as excessive or insufficient amounts significantly reduce PFAS yields. • Post-dTOP PFAS levels increased by 239-65,400%, exposing a substantial hidden contamination burden in Ghana. • Higher PFAS levels in Ghana’s mining and agricultural sites than in e-waste areas highlight local contamination in developing countries.