50 years of trace element pollution: mammals as biomonitors of environmental degradation in Latin America

Abstract

Mammals are excellent biomonitors for pollutants such as trace elements; however, there is a lack of studies on this subject in wild mammals across Latin America. This review provides a comprehensive and updated overview of the current state and trends in mammalian toxicology, offering an integrative regional perspective. A systematic literature review was conducted, identifying and synthesizing data on date of publication, country of study, analyzed pollutants, taxonomic group and trophic guild involved, biological matrix used, analytical techniques, and sample origin. Publications show a constant increase in their number and diversity. However, research remains concentrated in high-biodiversity or polluted areas within large countries such as Brazil, Mexico, and Argentina, leading to significant geographical biases. At present, the most frequently analyzed elements have been Hg, Pb, and Cd, reflecting their relevance as environmental pollutants generated from extractive industries and fossil fuel combustion. Aquatic carnivores are highly susceptible to bioaccumulation, making the order Cetacea and the piscivorous trophic guild the most studied groups, underscoring their well-documented issue of mercury contamination in aquatic ecosystems. On the other hand, terrestrial mammals remain comparatively understudied. Due to their central role in metabolic pathways and detoxification of contaminants, liver and kidney have been the most analyzed matrices. Atomic absorption spectrometry has been the most frequent quantification technique, favored for its suitable cost-benefit balance. Future research should incorporate non-invasive techniques and reevaluate the importance of scientific collections, as they offer valuable historical baselines for ecotoxicological studies. We strongly recommend prioritizing further research in mammal species populations living in urban areas and mining regions, to better understand and mitigate the ecological impacts of metal pollution in these threatened ecosystems.