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Minnesota : Proposed Studies Would Address Health Concerns Associated With Mining Activity In Northeastern Minnesota
One of the studies would focus on new concerns about asbestos-related cancer in mine workers
March 28, 2007 -- Minnesota - The Minnesota Department of Health (MDH) is proposing two new health studies addressing potential health concerns in northeastern Minnesota.
One of the studies would focus on the health of mine workers in the region. The other would assess the potential health impact of specific types of airborne mineral fragments generated by ore processing activity on the east end of Minnesotas iron range. The assessment would then be used to set regulatory exposure limits for those materials.
MDH proposed the new mine worker study after receiving reports of additional mesothelioma cases in a group of mine workers who had been the subject of an earlier study, completed in 2003.
Mesothelioma is a rare, fatal form of cancer seen almost exclusively in people who have been exposed to asbestos. When the earlier study was conducted, MDH had identified 17 diagnosed cases of mesothelioma in a group of 72,000 people who worked in Minnesotas iron mining industry between the 1930s and 1982.
MDH has since identified 35 additional cases of mesothelioma in that group, raising the total number of cases to 52. MDH officials say it's not surprising to see additional reports of the illness among the miners in the 2003 study, since it can take as long as 40 or 50 years to develop mesothelioma following exposure to asbestos.
The earlier study concluded that the 17 original mesothelioma cases were most likely caused by exposure to forms of asbestos that are found in a variety of industrial settings, and are not unique to the mining industry.
The mesothelioma issue has been with us for a long time, said Minnesota Health Commissioner Dianne Mandernach. There are important, unresolved questions that we need to address, and we believe this new study will help us provide some of the answers.
Although the new mesothelioma cases are a major health concern in their own right, theyre just part of a larger picture, she added. Since mesothelioma is usually an indicator of asbestos exposure, the workers we studied may also be at risk for other asbestos-related illnesses like lung cancer and asbestosis. Those diseases potentially affect much larger numbers of people.
The new study will focus on the same group of workers, comparing workers who developed mesothelioma with those who did not, in an effort to determine what aspects of their jobs might have placed them at risk.
The second MDH study would assess the health risks associated with airborne mineral fragments from ore mined in some areas on the east end of the range. The risk assessment will assist in setting airborne exposure limits designed to protect the general public from any potential health effects associated with those materials.
The new regulatory exposure limits will be established using a new methodology, to be developed as part of the study. In developing the new methodology, MDH will use data from animal studies that had previously been collected by the U.S. Environmental Protection Agency (EPA).
This new methodology may also be useful in setting site-specific exposure limits at other locations in the state where ore could contain mineral fragments posing a potential health concern.
MDH plans to seek federal funding for the mesothelioma study from the National Institute for Occupational Safety and Health (NIOSH) and other sources. Once funding is obtained, the study is expected to take three years to complete, at a cost ranging from $750,000 to $1 million.
The mineral fragment study is expected to take about a year once the animal study data becomes available from EPA, at an estimated cost of $250,000.
The proposed study of mesothelioma in mine workers will expand and build on the 2003 study, which was the first to ever conclusively document the occurrence of mesothelioma in Minnesota mine workers.
The earlier study looked at the work histories of the 17 miners with mesothelioma, in an effort to determine what might have exposed them to asbestos. While MDH investigators were conservative about drawing conclusions from the 2003 study, they suggested that the 17 original mesothelioma cases were most likely caused by exposure to commercial asbestos.
Commercial asbestos includes a variety of products and materials that have commonly been used in industrial settings, but are not unique to mining operations including materials used in plumbing, carpentry, boiler operation, and maintenance work.
The new study would differ from the earlier one in two important ways. First, it would focus on possible past exposure of workers to taconite dust, as well as potential exposure to commercial asbestos. Second, it would use a case-control strategy to compare the work experience of people who developed mesothelioma and those who did not.
The relationship between respiratory disease and mining work has been a continuing concern in northeastern Minnesota, where unusually high rates of mesothelioma have been reported among male residents in the general population since the late 1980s. Between 1988 and 2005, 136 cases of mesothelioma were diagnosed in men who live in that part of the state more than twice the expected number.
Some of the elevation in men can be explained by the fact that over 5,000 people once worked at an asbestos ceiling tile factory in Cloquet. However, officials say that doesnt account for all of the additional cases. Its not clear how many of the 136 cases have occurred in men who were among the 72,000 mine workers included in the 2003 study. The new study will attempt to clarify that connection.
There has been no elevation in mesothelioma rates among women who live in that region of the state.
Cancer Incidence Rates in Northeastern Minnesota with an Emphasis on Mesothelioma - PDF
The Minnesota Department of Health first documented the rates of mesothelioma and other cancers in Northeastern Minnesota in a 1997 report, Cancer Rates and Trends in Northeastern Minnesota, 1997. This analysis, using data from 1988-1994, showed that overall cancer rates in Northeastern Minnesota were virtually identical to statewide rates. For several specific types of cancer, some differences were observed, typical of almost all such geographic comparisons of cancer rates. However, a large and significant elevation was found for mesothelioma a rare cancer that typically occurs several decades after exposure to asbestos. These findings were confirmed in a 1999 analysis that included two additional years of cancer data (see Cancer Incidence Rates in Northeastern Minnesota, 1999). Between 1988 and 1996, 54 cases of mesothelioma were diagnosed among men in northeastern Minnesota. This was 73% higher than the expected number of cases (31) based on the statewide average and the population of the region. Mesothelioma rates were not elevated among women (3 cases, 8 expected).