Ecological and health risk assessment of PCBs and DDTs in mangrove sediments: A source-oriented study in southern China

Occurrence of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethanes (DDTs) in mangrove sediments from southern China and their ecological/health risks were assessed in this study. According to our results, concentrations of PCBs and DDTs in mangrove sediments from the Pearl River Estuary (PRE) ranged of 0.30-7.11 and 1.00-57.20 ng/g dry weight, respectively, with the local human activities and the historical inputs as the major sources. Contamination levels in the PRE mangrove sediments were lower than the national average, as were the associated ecological and health risks. PCBs were predominantly from industrial source (84.80 %), while DDTs were predominantly from agricultural source (86.02 %) in southern China mangrove sediments. Risk assessment results confirmed that the non-carcinogenic human health risk remained within safety thresholds (Hazard Index <1). PCBs contributed more to the non-carcinogenic risk across all population groups than DDTs. Children were found to be more susceptible to carcinogenic and non-carcinogenic risks. Industrial source (77.64 %) and runoff source (12.13 %) emerged as the main drivers of both risk categories. While the ecological risk of PCBs was considered negligible, the carcinogenic risk potential requires careful attention. The study identified priority controls for industrial source and PCBs, providing theoretical support for mangrove pollution control and human health risk reduction.