First Report on Metal Contamination and Associated Human Health Risks in the Smooth Butterfly Ray Gymnura cf. micrura (Myliobatiformes: Gymnuridae) from the Brazilian Amazon Coast.

Metal accumulation in batoids reflects both environmental exposure and physiological regulation, although studies concerning this group are still scarce. The Smooth butterfly ray (Gymnura cf. micrura) is consumed in northeastern Brazil, yet information on metal contamination and associated health risks are unavailable to date. This study assessed metal and metalloid concentrations, muscle metallothionein (MT) levels, elemental associations, and human health risks in specimens collected off the Maranhão coast. No significant sex-related differences were observed in element concentrations or MT levels, and MT showed no significant correlations with metals, suggesting limited muscle involvement in detoxification or exposure levels below induction thresholds. Multivariate and correlation analyses indicated distinct accumulation patterns, with rare earth elements associated with lithogenic inputs and some essential-toxic element relationships suggesting possible antagonistic interactions, particularly involving Se and Hg. A risk assessment showed that estimated daily and weekly intake values remained below guidance limits under realistic inorganic As assumptions. However, non-carcinogenic and carcinogenic risks increased under conservative scenarios, especially for infants at higher consumption frequencies. Although a positive HBVSe value suggests possible Se-mediated protection against Hg toxicity, this effect does not eliminate overall contaminant-related health risks.