Assessment of Metal Contamination and Human Health Risks in the Amapari River, Brazilian Amazon

The contamination of water by heavy metals is a great concern for many countries worldwide because of their potential to harm human health and biota. Although bordered by a mosaic of conservation units, the Amapari River (Brazil) is impacted by legal and illegal mineral exploitation. However, data on metal concentrations and related risks remain scarce. This study aimed to evaluate the concentrations of Cr, Cu, Fe, Hg, Ni, Mn, Pb, and Zn in Amapari River water and to assess compliance with environmental and drinking-water standards. We also calculated the Risk Indexes (RI), Chronic Daily Intake (CDI), Risk Quotients (RQ), and Carcinogenic Risk (CR) for ingestion and dermal pathways. Cr, Cu, Fe, Ni, Mn, Pb, and Zn were quantified using flame atomic absorption, and Hg was measured with hydride generation coupled to ICP-MS. Pb, Cu, and Hg exceeded CONAMA 357, and Pb exceeded Ordinance 888. The mean CDI values for ingestion were higher than those for dermal exposure for all analyzed metals. RQ values for ingestion were greater than those for dermal contact. RI was 3.03, showing the potential for adverse noncarcinogenic effects on human health. CR values for Pb and Cr through ingestion were both above 10–4, reflecting a high risk of cancer. CR values for dermal exposure to both metals were also above 10–4. This study demonstrated that the Amapari River is contaminated by multiple metals and poses potential risks to human health. These findings highlight the urgent need for environmental monitoring, regulatory enforcement, and mitigation measures.