Increase of blood mercury level with shark meat consumption: A repeated-measures study before and after Chuseok,...

Sharks are known to contain high levels of mercury in their meat. However, few studies have directly assessed the changes in mercury concentration in the human body according to shark meat intake. One hundred and ninety-seven participants that traditionally consume shark meat during the Chuseok holiday were recruited from two areas of Gyeongsangbuk-do, South Korea to examine their blood mercury level before and after the holiday season. Blood mercury levels were measured before and after the holiday season. Characteristics such as the consumption of shark meat, intake amount, and the effect on mercury concentration were assessed during the survey. Univariable and multivariable analysis (Linear Mixed Model) were done for assessing the association between shark meat consumption of holiday season and blood mercury level. Among the total participants, 83 consumed shark meat during holiday. In the univariable analysis, a significant increase in blood mercury levels before and after Chuseok was observed only for the group that consumed shark meat during holiday. The multivariable analysis (adjusted for identified confounders that affect both exposure and outcome considering repeated measurements) showed that consuming shark meat was significantly associated with increased blood mercury levels by 3.56 μg/L (95% confidence interval [CI], 2.64-4.67 μg/L). In the model considering the amount consumed as two group, the level of increase was 2.61 μg/L (95% CI, 1.63-3.58 μg/L) for those consuming <100 g, and 6.20 μg/L (95% CI, 4.77-7.62 μg/L) for those consuming ≥100 g compared to group without consuming shark meat. Considering amount consumed as continuous value, 0.02 μg/L (95% CI, 0.01-0.02 μg/L) of blood mercury increase was significantly associated with consuming 1 g. Consumption of shark meat significantly elevated blood mercury levels, exceeding commonly suggested reference concentrations in less than 2 weeks. These findings suggest the need for public health warnings and regulations regarding shark meat consumption.