The characteristic and bio-accessibility evaluation of mercury species in various kinds of seafood collected from Fujian of China for mercury risk assessment.

Seafood consumption is the major source of total Hg (tHg) and methyl mercury (MeHg) for humans. Lack of broad-representative bio-accessibility of mercury species makes accurate assessment on health risk of seafood's mercury impossible. Herein, the concentrations and in vitro bio-accessibilities of mercury species in 93 seafood samples with 71 different species were extensively investigated. Results indicated that all shellfish and fish samples, and most seaweed samples contained both Hg2+ and MeHg, while some seaweed samples contained only Hg2+. The concentrations of mercury species varied depending on the differences in species/individuals of seafood and sampling regions. MeHg in seafood can be partly de-methylated into Hg2+ during gastrointestinal digestion, which reduced the toxicity of mercury in seafood. The mean demethylation rate of MeHg varied as follows: seaweeds (⁓62.1 %) > shellfishes/shrimps (⁓19.7 %) > fishes (⁓9.2 %). The mean bio-accessibility of Hg2+ and tHg varied as follows: seaweeds (⁓97.7 % and ⁓90.1 %) > shellfishes/shrimps (⁓65.1 % and ⁓67.9 %) ≈ fishes (⁓65.1 % and ⁓66.7 %), while that of MeHg varied as follows: fishes (⁓57.7 %) > shellfishes/shrimps (50.8 %) > seaweeds (⁓11.6 %). The simulated calculation of target hazard quotient (THQ) revealed that the health risk of seafood's mercury may be accurately assessed using tHg, not mercury species, even without considering bio-accessibility. This offers a simple but protective approach for assessing the health risk of seafood's mercury. Results of this study provide the potential broad-representative bio-accessibilities of mercury species existing in various kinds of seafood and novel insights for scientifically assessing the health risk of seafood's mercury and revising the mercury limitation in seafood.