What’s going on with taconite miners in northeastern Minnesota? Over the past decade, nearly sixty workers in the Minnesota iron mining industry have been diagnosed with mesothelioma, according to a state health department report, and the true figure may be much higher, since prior to 1999, mesothelioma was reported on state death certificates as simply “cancer.” In any event, the rate of mesothelioma in this area is easily twice that of other parts of Minnesota. Taconite is a silicate type of rock, similar to flint, that has a high iron content. The taconite that is mined from Minnesota’s Mesabi Iron Range makes up most U.S. iron production today. Despite its silicate structure, taconite has not been known to emit fibers like asbestos. It does, however, emit large amounts of silicate dust. Or does it? Over thirty years ago, when demand from China started to make iron extraction profitable enough to justify re-opening the mines, fibers similar to those produced by asbestos were found in municipal water supplies in the area.
They were traced to an operation managed by the Reserve Mining Company. A Minnesota Department of Health (MDH) study later showed that local mesothelioma rates were 70% higher than the statewide average. Recent studies have now been taken over by University of Minnesota’s School of Public Health, as the MDH studies failed to provide any information on health risks caused by airborne fragments of taconite ore. Up until now, asbestos was considered to be the sole cause of mesothelioma. The current situation in northeastern Minnesota raises two questions: (1) Is taconite dust also responsible for the development of mesothelioma? (2) Is the taconite contaminated with asbestos fibers? Asbestos is the broad term for an entire class of silicate minerals that are soft and flexible, yet retain the strength and fire- and heat-resistance of other kinds of rock. Although there are many different kinds of asbestiform fibers, only a few of these, primarily chrysotile, crocidolite, tremolite and amosite, are subject to any regulation in the U.S. Other types, predominantly richterite and winchite, are not subject to regulation, and are still found in many commercial products. The current challenge is to determine whether mesothelioma in these cases is caused by taconite dust itself, or if there are asbestos particles present.