Baseline mercury concentrations and dietary risk assessment in blue shark (Prionace glauca) from Ilo, southern Peru.

Total mercury (THg) was quantified in dorsal muscle from 12 blue sharks (Prionace glauca; six males and six females; 167-230 cm total length) landed at the artisanal fishing port of Ilo, southern Peru, in October 2021. THg was determined by cold-vapour atomic absorption spectrometry at an ISO/IEC 17025-accredited laboratory. Concentrations ranged from 0.021 to 0.330 mg kg-1 wet weight, with a mean of 0.156 ± 0.102 mg kg-1. All samples were below the applicable regulatory limits for shark and represented 1.3-20.6% of the Codex Alimentarius maximum level for methylmercury (1.6 mg kg-1), for which THg may be used as a screening measure. THg increased significantly with total length (Pearson r = 0.768, p = 0.003). Females had higher mean concentrations than males, although the difference was not statistically significant and should be considered preliminary. Dietary exposure was evaluated using fresh-products (40 g day-1) and total-products (70 g day-1) screening scenarios derived from Peruvian apparent-consumption statistics. Under the fresh-products scenario, Target Hazard Quotient (THQ) values were 0.98 for general adults and 2.09 for children aged approximately 9-10 years; under the total-products scenario, they increased to 1.71 and 3.65, respectively. Estimated weekly intake remained below the methylmercury Provisional Tolerable Weekly Intake (PTWI) for adults but reached 159.7% for children under the total-products scenario. These findings provide an independent preliminary local reference dataset for P. glauca landed at Ilo. Although measured THg concentrations were low, the conservative exposure scenarios indicated potential concern for children, highlighting the need for larger monitoring datasets, methylmercury speciation, and local shark-consumption surveys.