Polychlorinated Biphenyls in a Ramsar Wetland: Occurrence, Source Apportionment Using PMF, and Probabilistic Human Health and Ecological Risk Assessment in Water and Sediments of Ashtamudi Lake, India

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that are of global concern due to their environmental persistence, bioaccumulation potential, and adverse ecological and human health impacts. This study presents the first comprehensive baseline assessment of the distribution, sources, and risks of the indicator PCBs in the Ashtamudi Wetland listed in Ramsar, a tropical estuarine ecosystem on the southwest coast of India. Surface sediment and water samples were analyzed for six indicator PCB congeners (PCB-28, 52, 101, 138, 153 and 180). Total PCB concentrations in sediments ranged from 0.20 to 2.99 µg/kg dry weight, with a mean of 0.70 ± 0.65 µg/kg dw, indicating moderate contamination compared to global coastal environments. The congener distribution followed the order: hexa-CBs > tri-CBs > penta-CBs > tetra-CBs > hepta-CBs. Elevated concentrations near urban and industrial discharge zones indicate localized anthropogenic sources. Multivariate statistical analyzes, including Cluster Analysis and Positive Matrix Factorization (PMF), identified three primary contributors: Aroclor-type mixtures, open waste burning, and legacy e-waste contamination. The ecological risk assessment showed low potential for adverse effects, while the human health risk assessment revealed no unacceptable non-carcinogenic or carcinogenic risks through sediment ingestion or dermal contact. Because only six congeners were analyzed, the findings reflect a conservative estimate of overall PCB contamination. The study underscores the importance of integrated monitoring through chemical analysis, source allocation, and risk assessment to manage persistent pollutants in ecologically sensitive wetland ecosystems.