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

Our plain-English summary of Invisible threats: environmental asbestos exposure and water contamination in a former mining area of Northeastern Brazil, by O.S. Brito, M.F.M. Pereira, C.S.M.C. Lima, et al (Cadernos de Saúde Pública, 2026).

The study

• Authors: O.S. Brito, M.F.M. Pereira, C.S.M.C. Lima, G.A. Carrijo-Gonçalves
• Journal: Cadernos de Saúde Pública
• Published: 2026;42:e00271425
• Read it: PubMed · Publisher · Free full text

Abstract

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.

In plain English

This environmental monitoring study looked for chrysotile asbestos fibers in surface water and bottom sediments near the former São Félix asbestos mine in Bom Jesus da Serra, Bahia, Brazil, which operated from 1936 to 1967. In five field campaigns between August and November 2022, the authors sampled eight sites, collecting 120 water samples and 40 sediment samples. Fibrous particles seen under a stereoscopic microscope were examined by scanning electron microscopy with elemental analysis. Two sediment samples were sent to an outside laboratory, where the fibers were confirmed as chrysotile asbestos. The authors reported repeated detection of fibrous material in both water and sediment, mainly in fine-grained sediment. Total coliforms and E. coli were found in water at several sites. Fibers were not counted, so the results could not be compared with regulatory limits. The authors concluded that residues from the former mine remain detectable in the environment. They said their results describe environmental occurrence rather than a direct assessment of human health risk.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Environmental monitoring study: field sampling of surface water and bottom sediment, with physicochemical, microbiological and microscopic laboratory analysis
• Who was studied: Eight surface water sites, each with a matching bottom-sediment point, near the former São Félix mine in Bom Jesus da Serra, Bahia, Northeastern Brazil. There were five campaigns between August 12 and November 4, 2022, giving 120 water samples (triplicates) and 40 sediment samples. No people were studied.
• Exposure: Chrysotile asbestos in the environment from the deactivated São Félix asbestos mine, which operated from 1936 to 1967 and was not remediated afterward
• Main results:
  • Initial stereoscopic screening found elongated, fibrillar particles mostly in fine-grained sediment, especially at sites downstream of the former mine
  • Fibrous material was detected repeatedly in both sediment and water samples
  • Elemental analysis by scanning electron microscopy showed oxygen, silicon, magnesium, aluminum and carbon. The authors described this composition as consistent with chrysotile or asbestos minerals.
  • Two sediment samples examined by polarized light microscopy and transmission electron microscopy at an outside laboratory were confirmed as chrysotile asbestos
  • Elemental analysis of the confirmed samples showed mostly magnesium (54%) and silicon (40%), with iron at 1%
  • Total coliforms and E. coli were detected in surface water samples from several sampling points. These results were recorded as present or absent.
  • Turbidity reached 104 NTU at site WP4 and 721 NTU at site WP7 in particular campaigns
  • Dissolved oxygen fell below 1 mg/L at some sites after rainfall
• The authors' conclusion: The authors concluded that, although their approach was qualitative, the consistent identification of fibers across campaigns suggests that residues from the former mine remain detectable in surface water and sediment
• Limitations the authors state:
  • The fiber analysis was qualitative only
  • Fiber concentrations were not measured (no fibers per liter and no mass per unit of sediment), so the results could not be compared with regulatory limits
  • The physicochemical and microbiological measurements do not establish a causal link with the presence of asbestos fibers
  • The results show environmental occurrence and are not a direct assessment of human health risk
  • Microbiological results were reported only as presence or absence

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Mineral Fiber, IARC, Chrysotile, Scanning Electron Microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Transmission Electron Microscopy (TEM).

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