Trace metals contamination in freshwater fish in Brazil: related factors, environmental impacts, and risks to human health.

Freshwater fish are essential components of the aquatic food chain and an important source of protein and nutrients for various communities, especially riverine populations. However, water pollution is one of the main causes of metal bioaccumulation in the organs of these animals. This study conducted a systematic review of the scientific literature on trace metal contamination in freshwater fish in Brazil. The methodological procedure was structured in three stages: definition of the research problem, application of a relevance test with inclusion and exclusion criteria, and selection of eligible studies for the review. Regional heterogeneity was observed in the scientific production on metals in freshwater fish in Brazil, with a higher concentration of studies in the Northern region. The studies indicate a predominance of native species and demonstrate that trophic level, feeding habits, and interaction with the habitat influence the bioaccumulation of metals in freshwater fish in Brazil. There was also consensus that the metals of greatest toxicological and environmental relevance are Pb, Cd, Cr, and Hg, which were the most frequently identified in the studies. The contamination profile of metals in fish varies regionally and is directly related to anthropogenic activities such as mining, intensive agriculture, urbanization, and effluent discharge. Health risk assessment studies indicate that the daily intake of some potentially toxic trace metals (cadmium, lead, and mercury) may exceed the maximum limits established by legislation, mainly affecting populations with high fish consumption, such as Amazonian riverine and Indigenous communities.