Mercury contamination in imported shark meat (“cação”) and implications for human exposure in Brazil

Abstract

Brazil is the largest global consumer of shark meat, marketed as “cação,” yet traceability and risk assessment are limited due to unclear labeling and insufficient monitoring. Shark meat is a source of toxic elements, particularly mercury (Hg), posing significant health risks, especially for children and vulnerable populations. Total Hg (THg) was quantified in dorsal muscle samples obtained from carcasses of animals marketed in Brazil as “cação”. Based on DNA barcoding, Prionace glauca (blue shark) was identified in 38 samples and Makaira nigricans (blue marlin) in one sample. Total Hg concentrations ranged from 0.336 to 2.758 mg kg⁻¹ wet weight (mean: 1.363 ± 0.559 mg kg⁻¹), with 95% and 77% of samples exceeding international and national safety limits, respectively. Estimated weekly Hg intake for children (6–13 years) ranged from 0.805 to 6.613 µg kg⁻¹, with 91% above the provisional tolerable weekly intake (PTWI). For adults, weekly intake ranged from 0.525 to 4.315 µg kg⁻¹, with 71% exceeding the PTWI. Based on the 90th percentile of maximum safe consumption quantity values, a weekly intake of approximately 40 g of imported shark meat was recommended for children and 75 g for adults. However, the consumption of shark meat should be avoided whenever possible. Significant public health risks were associated with imported shark meat sold as “cação” due to elevated Hg concentrations and the frequent mislabeling of threatened species. Stricter inspection protocols, improved traceability systems, and broader monitoring efforts are needed to reduce Hg exposure and improve species identification in shark products.