Metallic Makos: Metal and Metalloid Levels and Human Health Risks Arising from the Consumption of Shortfin Makos (Isurus oxyrinchus) from Southeastern Brazil.

Sharks are among the most threatened vertebrate groups, facing pressures from overfishing, habitat loss, and pollution, with the latter posing risks not only to marine ecosystems but also to human health due to the global consumption of shark meat. This study assessed the concentrations of essential, potentially toxic, and toxic metals in the muscle tissue of 61 shortfin makos (Isurus oxyrinchus), an endothermic pelagic species, caught by industrial fleets off the coast of São Paulo, Southeastern Brazil. Several elements, including Co, Ni, V, Rb, and Ti, are reported herein for the first time in this species, expanding the understanding of metal bioaccumulation in pelagic sharks. High levels of toxic elements such as As, Cd, Cr, Hg, and Pb, along with potentially toxic elements like Ti, were detected, with concentrations of As and Hg exceeding food-safety thresholds, raising significant public health concerns. Shortfin makos may present partial physiological resilience to environmental stressors due to endothermy; although, the elevated concentrations of neurotoxic metals like Hg and significant levels of Cu and Ti detected herein highlight its vulnerability to contamination. Moderate positive correlations between metallothionein (MT) and Ti and Rb, and a moderate negative correlation with Co, suggest selective detoxification pathways; although, the limited correlation with other elements points to restricted MT-mediated protective mechanisms in muscle tissue. The relatively high MT levels observed may reflect an adaptive response to chronic exposure rather than effective detoxification. An elevated hazard index indicates that even when individual contaminants are within acceptable limits, their combined effects pose considerable health risks. Given species-specific variability in metal accumulation and the absence of toxicological thresholds for elasmobranchs, future research should aim to define these limits to guide both conservation strategies and public health policies. Ecotoxicological assessments can serve as indirect conservation tools by highlighting human health risks associated with the consumption of threatened species, potentially discouraging their exploitation.