Invisible threats: environmental asbestos exposure and water contamination in a former mining area of Northeastern Brazil.

Asbestos, a mineral fiber historically used in construction and industry due to its durability and resistance, is recognized as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC), based on sufficient evidence of carcinogenicity through inhalation exposure. Although chrysotile asbestos was banned in Brazil in 2017, former mining areas remain major environmental liabilities, potentially sustaining long-term contamination of surrounding ecosystems. This study aimed to identify and characterize the qualitative presence of chrysotile asbestos fibers in surface waters and sediments in Bom Jesus da Serra, Bahia, Northeastern Brazil, where the São Félix mine operated for nearly three decades without subsequent remediation. Between August and November 2022, eight sampling sites were monitored across five field campaigns. Water and sediment samples were collected and analyzed for physicochemical parameters according to ABNT and CETESB standards, while asbestos fibers were detected and confirmed using phase-contrast microscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy, and transmission electron microscopy. Chrysotile fibers were consistently detected in water and sediment samples from all sites, with higher accumulation in sediments, indicating persistent contamination of aquatic ecosystems. Most conventional water quality indicators complied with Brazilian standards. However, asbestos fibers were not quantified using regulatory metrics, preventing comparison with international guidelines and limiting exposure assessment. Their recurrent qualitative detection indicates environmental persistence and supports continued monitoring and future quantitative investigations to inform public health strategies in vulnerable communities.