he most toxic and bioaccumulative form of mercury in the environment is methylme
ID: 146162 • Letter: H
Question
he most toxic and bioaccumulative form of mercury in the environment is methylmercury (MeHg), which affects the central nervous system in humans and causes long-term delays in neurocognitive development of children. Consumption of marine fish is the greatest source of MeHg exposure to United States residents. Consumers along the Gulf of Mexico coast are at enhanced risk because of their high levels of seafood consumption and the likelihood that many species of the Gulf of Mexico fish have higher levels of mercury than the same species harvested on other coasts. It has been estimated that perhaps 30% of the Gulf coastal population exceeds EPA's reference dose (RfD) for MeHg, which is used as a criterion to protect human health. Table 1 summarizes the annual commercial harvest and the mean Hg concentration in edible muscle tissue of seafood species from the Gulf of Mexico. You can assume all Hg in seafood tissues are in form of MeH (a) Find the three seafood species of the highest Hg concentration and the three seafood species of the lowest Hg concentration from Table 1. What are the possible causes for the gap of Hg concentrations between these two groups of seafood species? (b) Evans et al. (2015) reported the average surface water concentration of MeHg in the Gulf of Mexico to be 0.0035ng/L. Calculate the bioconcentration factors (BCF) of MeHg in the seafood species in part (a) (c) If you eat one quarter pound of the seafood species in part (a), how much MeHg will you ingest? (Perform the calculation for each species) (d) If you swallow one liter of water during a day while water skiing in the gulf, how much MeHg will you ingest? (e) The reference dose (RfD) of MeHg suggested by EPA is 0.1 ug/kg/day. Would the activities in part (c) and (d) lead to an ingested amount of MeHg exceeding the RfD? (Assume you eat the one quarter pound seafood in one day)Explanation / Answer
A) The three seafood species that have the highest concentration of Hg are King mackerel, Golden tilefish and sharks.
The three seafood species that have the lowest Hg concentration are striped mullet, oysters and brown shrimp.
B) Bioconcentration factor is the ratio of concentration of a substance in an organism to its environment.
BCF of king mackerel = 1.111× 10^-3 / 35 × 10^-13 = 3.17 x 10^8
BCF of golden tilefish = 1.014×10^-3/35×10^13 = 2.89 x 10^8
BCF of sharks = 0.743×10^-3/35×10^-13 = 2.12 x 10^8
BCF of striped mullet = 0.062×10^-3/35×10^-13 = 1.77 x 10^7
BCF of oysters = 0.072×10^-3/35×10^-13 = 2.06 x 10^7
BCF of brown shrimps = 0.078×10^-3/35×10^-13 = 2.23 x 10^7
C)
King mackerel = 1.111 × 0.11 = 0.12 mg
Golden tilefish = 1.014 × 0.11 = 0.111 mg
Sharks = 0.743×0.11 = 0.081 mg
Striped mullet = 0.062×0.11 = 0.007 mg
Oysters = 0.072×0.11 = 0.008 mg
Brown shrimps = 0.078×0.11 = 0.009 mg
D) One liter of water contains 0.0035 ng of mercury
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