Abstract
OBJECTIVES: Erionite, a naturally occurring fibrous zeolite classified as a human carcinogen, is believed to be more potent than asbestos in causing mesothelioma. However, unlike asbestos, erionite has rarely been used for commercial purposes and, as a result, knowledge about exposure pathways is limited. This paper provides a narrative review of the current knowledge regarding the associations between erionite exposure, health effects and exposure circumstances. METHODS: Medline/PubMed and Scopus were systematically searched up to the end of 2024 using keywords related to erionite exposure and health outcomes. RESULTS: We identified 26 peer-reviewed journal articles reporting on the health effects of erionite exposure, specifically mesothelioma and lung cancer, with mesothelioma being the most extensively studied outcome. Of these, 12 studies focussed on erionite-exposed populations in Turkey, 8 examined health effects among Turkish migrants in northern Europe, and 6 investigated erionite-related health risks in North America (3 in the United States and 3 in Mexico). These studies showed a very high incidence of mesothelioma, often in relatively young individuals, from the Cappadocia region of Turkey, with well-documented environmental exposures to erionite, contributing to a high proportion of all deaths (21% to 51%) in affected villages. Evidence of lung cancer associated with erionite exposure was also found. There is also evidence of erionite exposure-associated mesothelioma in Guanajuato, central Mexico. In the United States, erionite exposure-associated health effects (not mesothelioma) have been reported among people occupationally exposed to erionite. Studies on environmental exposures have shown outdoor concentrations ranging from 0.001 f/ml to 0.3 f/ml, while indoor concentrations have ranged from 0.005 to 1.38 f/ml. Occupational exposure to erionite has been less studied, with only one study in forestry workers showing elevated exposures to erionite ranging from non-detectable to 0.36 f/cc. Erionite deposits have also been identified in other countries such as Italy and New Zealand, but exposures and associated health effects have not yet been studied in these regions. CONCLUSION: There is clear evidence that environmental exposure to erionite in the Cappadocia region of Turkey, and Guanajuato in central Mexico are causally associated with the high mesothelioma rates observed in these areas. Evidence for other parts of the world where there is naturally occurring erionite is limited. This review has highlighted significant knowledge gaps, and advocates for further research on occupational exposure to erionite fibres and associated health effects.