Trophodynamics features and potential human health risk of arsenic and cadmium in marine fauna from the Yellow River Estuary, China

Toxic arsenic (As) and cadmium (Cd) pollution threatens organisms and humans in coastal ecosystems, but their biomagnification in marine systems remains under debate. This study investigated the levels and trophodynamic features of As and Cd, and potential human health risks of marine fauna within continuous trophic levels (TLs) from the Yellow River Estuary, China, and adjacent sea (YRE), as indicated by nitrogen stable isotope analyses. Individual faunal samples were grouped into continuous TL ranges and analyzed separately in fish and in-vertebrates. As and Cd concentrations varied significantly between fish and invertebrates within different TL ranges. Trophic magnification factors (TMFs) also revealed different bioaccumulation features of As and Cd with increasing TL via trophic transfer in the food chain. Although As and Cd were biodiluted in marine organisms overall from the YRE, they were biomagnified in invertebrates through trophic transfer, with TMFs of 1.91 and 1.70, respectively. As and Cd biomagnification in invertebrates was hidden by overall evaluation of toxic element bioaccumulation in marine fauna. Crustacea accounted for 55% of the invertebrate taxa in the study, which could have an important role in the biomagnification of these two elements in invertebrates as a whole. Given that marine organisms occupying higher trophic positions at higher risk of As and Cd biomagnification might be underestimated in the analyses of mean values at the species level, the target hazard quotient through fish and invertebrate consumption was calculated separately based on individuals distributed within continuous TL ranges corresponding to element concentrations, and the health risks to adults and children were evaluated. Results indicated that, in the study area, the non-carcinogenic health risk associated with As and Cd from consuming invertebrates was higher than that from fish, especially for children. In addition, estimation of As carcinogenic risk (>10-4 in both invertebrates and fish) also indicated that ingestion of seafood from the YRE with suggested meal size would cause cancer risk with long-term consumption, especially of invertebrates. Therefore, it is necessary to monitor toxic metal concentrations in aquatic organisms to devise regulations around seafood consumption by humans.