Priority toxic metals arsenic, cadmium, mercury, and lead in ecosystems: A review of sources, toxicity, and regulatory approaches

<p>Heavy metals pose a persistent and escalating threat to ecosystems and human health due to their environmental persistence, bioaccumulative potential, and pronounced toxicity. This systematic review synthesizes current knowledge on the distribution, mechanisms of toxicity, regulatory approaches, and analytical strategies concerning four priority toxic metals: arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb). Relevant literature published between 2020 and 2025 was retrieved from Scopus, Web of Science, and PubMed, focusing on peer- reviewed studies. Included publications address contamination sources, toxicodynamics, international standards (WHO, EFSA, EU, Codex), and monitoring practices. Marked discrepancies in permissible exposure limits were identified across jurisdictions, while the neurotoxic, nephrotoxic, and carcinogenic effects of these metals are well documented. Particular concern arises from chronic low-dose exposure, combined metal exposure, and the emergence of nanoparticulate forms—areas where regulatory frameworks remain insufficient.<br>The findings highlight the urgent need for harmonized standards, expanded biomonitoring efforts, and improved risk assessment methodologies to better safeguard environmental and public health.</p>