Bioaccumulation, contamination and health risks of trace elements in wild fish in Chongqing City, China: a consumer guidance regarding fish size.

Trace elements generally contaminate wild fish, particularly in megacities, necessitating guided consumption practices. This study investigated the bioaccumulation of trace elements in wild fish from Chongqing City in June 2021. We evaluated their contamination and associated health risks to establish consumption guidance based on fish size. Our results indicate that the concentrations of Zn, Pb, Cr, and As were relatively high, with some fish exceeding the maximum residue limits. Herbivorous and pelagic fish generally exhibited lower bioaccumulation of most trace elements, except for Cr and As, which were higher in pelagic species. The contamination indices (Pi) for Cr, Pb and As were consistently above 0.2, indicating widespread contamination. The most contaminated fish typically measured around 19 cm in length and weighed approximately 90 g. Only the maximum target hazard quotients (THQ) for As, Cr, and Hg exceeded 1, with a notably high ratio of THQ(As) > 1, highlighting concerns over arsenic contamination. The THQ(As) remained below 1 for adults across all fish species, whereas for children, species such as Onychostoma sima, Pseudohemiculter dispar, and Parabramis pekinensis exceeded this threshold. Fish safe for adult consumption generally measured 13 cm in length and weighed 20 g, and for children, 16 cm and 25 g. Consequently, selecting larger fish is likely to reduce the consumption of contaminated fish, thereby decreasing health risks to the public. The centralization of contaminated fish with high risk in specific size range confirmed fish size could be used to gauge the contamination and health risk of fish.