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History of the Minnesota Iron Mining Cohort

Investigation into potential health issues of iron mining workers began in the early 1980s when University of Minnesota School of Public Health researchers created a roster of some 70,000 unique individuals who worked for a year or longer sometime prior to 1982. The roster was constructed using records from seven mining companies with operations on the Mesabi Iron Range. The companies included: Reserve, Inland Steel, U.S. Steel, Jones and Laughlin, Hanna, Erie, and Eveleth Mining. Some of the miners worked at more than one company and worked at different locations across the range, thus nearly 90,000 employment records were abstracted to create the mining roster. Efforts were made to capture general work history information; however the funding was exhausted before this work could be completed. For this reason no health assessments of the mining workers could be done at that time.

 

In the late 1990s, the Minnesota Department of Health (MDH) began monitoring the cancer rates in this group of mining workers using the Minnesota Cancer Surveillance System (MCSS). The MCSS was established in 1988 to track all diagnoses of cancer in Minnesota residents. Through this process, the MDH measured an increase in observed mesothelioma cases compared to expected cases for the northeastern part of Minnesota. As of 2009, 63 cases had been identified from within the mining cohort originally identified by the University of Minnesota. The occurrence of these cases has raised questions about the relationship of mining to mesothelioma.

 

In 2007, the University of Minnesota's School of Public Health was funded by the Minnesota Legislature to conduct a thorough investigation into the mesothelioma cases, and to assess the health of taconite workers more broadly through mortality and cancer incidence studies.

 

The Minnesota Taconite Workers Health Study will use the 1980s roster of mining workers for several components of the study. Detailed job histories will be abstracted from the employment records collected in the 1980s so that exposure assessments can be constructed that include number of years worked, jobs held, and location of mine or processing facilities where employed.