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Analysing health data from rare occupational cohorts
  1. Thomas F Bateson
  1. Correspondence to Dr Thomas F Bateson National Center for Environmental Assessment, U.S. EPA, Washington DC 20460, USA; bateson.thomas{at}

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In Occupational and Environmental Medicine, Allen et al1 describe the “Mortality experience among taconite mining industry workers” in Minnesota. Interest in the potential health effects of exposures related to taconite mining stems from the detection of elongated mineral particles, including amphiboles, in the water supply of Duluth, Minnesota, USA traced to the disposal of taconite tailings into Lake Superior, the local source of municipal drinking water supplies. According to Allen et al,1 ingestion effects in laboratory animals or in humans were not identified, and interest eventually turned to the potential inhalation effects among exposed mining industry workers. Other groups of mining workers exposed to different forms of amphibole and non-amphibole asbestos have long been the subject of epidemiological investigations.2–5

Allen et al1 describe mortality patterns in a cohort of 68 737 workers from seven mining operations within Minnesota's Mesabi Iron Range, a geological area unusually rich in iron deposits. Some workers in the enumerated cohort were understandably excluded from the study's mortality follow-up due to a focus on exposures related to taconite mining rather than on the earlier Iron Range mining of an even more iron-rich ore called haematite which was not considered to have been associated with coexposures to elongated mineral particles. Additional workers were excluded from the …

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  • Competing interests None.

  • Provenance and peer review Commissioned; internally peer reviewed.

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