Total mercury, methylmercury, and selenium in aquatic products from coastal cities of China: Distribution characteristics and risk assessment

This study analyzed total mercury (THg), methylmercury (MeHg) and selenium (Se) in 114 aquatic product samples (representing 39 species) from eight coastal cities of China. The THg and MeHg levels in different parts of the same sample species were in the order of muscle ≥ skin/shell > roe, whereas Se levels were much higher in roe. Concentrations of THg, MeHg, and Se in the muscles were between 2.27–154, 0.36–135, and 57.8–1.20 × 103 ng g−1 wet weight (ww), respectively. Although significant differences in analyte concentrations were not observed among cities, they existed among three species; marine fish, freshwater fish, and shellfish. Shellfish had generally lower Hg content (mean: 20.2 ng g−1 ww THg, 6.71 ng g−1 ww MeHg, and 30.9% MeHg/THg ratio); however it had higher Se content (528 ng g−1 ww) than the other types of fish (mean: 33.3 ng g−1 ww THg, 28.2 ng g−1 ww MeHg, and 79.2% MeHg/THg ratio, 257 ng g−1 ww Se). In addition to species, the individual growth and HgSe interaction influenced Hg distribution. Evident correlations were observed between several individual body features and Hg content, and between Se and THg concentrations (p 1 and positive HBVSe values suggest that aquatic products from these sites will not pose immediate health problems to consumers. Fish was the dominating contributor for MeHg intake whereas shellfish was the dominating contributor for Se intake. To safeguard against mercury exposure, residents in these areas can appropriately increase shellfish intake (especially bivalves), rather than exclusively consuming marine fish. [Display omitted] •Muscle and skin/shell accumulated more Hg than roe whereas the latter was rich in Se.•Remarkable differences in the analyte content existed among aquatic product species.•Whilst shellfish had less MeHg, they had greater Se than marine/freshwater fish.•Hg content was related to Se content and individual growth features.•Food safety was affirmed by THg, MeHg, and Se intakes; Se:Hg molar ratio; and HBVSe.