Polychlorinated naphthalenes in freshwater fish from Beijing markets: Species-specific differences, effects of cooking, and health risk assessment.

Fish are an important source of human dietary exposure to polychlorinated naphthalenes (PCNs). The occurrence and sources of PCNs in different species of freshwater fish are unknown, and few studies have assessed human exposure risks to PCNs through freshwater fish. In this study, 140 freshwater fish samples from 10 species were collected from Beijing markets, China. The ΣCNs concentration range in the fish was 20.7-1310 pg/g wet weight (ww). The highest median ΣPCNs concentration (80.4 pg/g ww) was found in mandarin fish (Siniperca chuatsi), and the lowest (29.6 pg/g ww) in snakehead (Channa argus). Di- and tri-CNs were the dominant PCN homologues with contributions of 35.3 % and 30.8 %, respectively. Unintentionally produced PCNs from metal smelting might be the source of PCN contamination in freshwater fish. The cooking temperature and time did not significantly affect the PCN concentrations in fish or the PCN homologue profiles. The highest toxic equivalent (TEQ) value was observed in sturgeon (Acipenser sinensis), followed by mandarin fish. Hexa-CNs were the most abundant homologue for the PCN TEQs. A risk assessment indicated that the dietary exposure risks for local residents to PCNs through freshwater fish were low. However, the relatively high concentrations of PCNs in the samples deserve attention to avoid PCNs exposure risks for groups with high fish consumption rates. Furthermore, freshwater fish likely contain a mixture of contaminants including dioxin and furans which also display a similar mode of toxicity as the PCNs and could enhance the risk to fish consumers.