Background Recent studies in Minnesota showed an increased risk of mesothelioma among iron miners, and a significant dose-response relationship with cumulative exposure to elongate mineral particles (EMPs). This prompted us to assess the state of knowledge on potential contribution of EMPs in the aetiology of occupational lung diseases in iron and gold miners.
Methods We first systematically reviewed epidemiologic studies on iron and gold miners’ health, and animal studies on health effects of EMPs (published since 1990), and then conducted an exploratory study of the geological characteristics of iron and gold mines in Quebec. Following a literature review of mines for which health problems have been reported worldwide, a petrographic study was done on rock-specimens from several active and inactive mines in Quebec to identify mineral species that could have an EMP morphology.
Results Between January 1990 and February 2016, 24 epidemiological articles published in 7 countries mentioned cancer risks: only the Minnesota studies reported an increased risk of mesothelioma in iron miners, whereas 2 articles mentioned a few mesothelioma cases in gold miners. Three available animal studies and 4 toxicological literature reviews inferred that other parameters than dimension may modulate toxicity. The geological literature review indicated that EMPs are expected in host rocks of gold mines (tremolite and actinolite), and in rock-deposits of iron mines (grunerite). The identification of amphibole-EMPs in several specimens during our petrographic study confirmed these expectations.
Conclusion The epidemiological literature does not describe adequately dimensional characteristics of the particles, and animal studies point to possible toxicity of cleavage fragments that meet dimensional criteria of WHO fibres. Geological settings of iron and gold mines in Quebec seem to favour the formation of amphibole EMPs. In the absence of fibre measurements in the mines, the precautionary principle should be applied in order to protect workers adequately.
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