St. Paul, Minn. – A rare form of cancer linked to asbestos exposure has been found in another 35 miners on the Iron Range, the Minnesota Health Department reported Wednesday, and the state said it planned two studies to examine potential health concerns.
One study would focus on the health of mine workers in the region. The other would assess the potential impact of airborne mineral fragments created during ore processing.
The cancer, known as mesothelioma, is seen almost exclusively in people who have been exposed to asbestos. In a 2003 study, state researchers identified 17 diagnosed cases of mesothelioma in a group of 72,000 people who worked in Minnesota's iron mining industry between the 1930s and 1982.
Further analysis found 35 additional cases of mesothelioma in that group, raising the total number to 52, the department said in a prepared statement. Officials said the additional cases aren't surprising because it can take 40 or 50 years to develop mesothelioma after exposure to asbestos.
The earlier study found the 17 original mesothelioma cases were most likely caused by exposure to commercial asbestos used in mining and other industries. The cases aren't unique to ore mining.
"The mesothelioma issue has been with us for a long time," Health Commissioner Dianne Mandernach said in a statement. "There are important, unresolved questions that we need to address, and we believe this new study will help us provide some of the answers."
The mining study will focus on the same group of workers, comparing those who have developed mesothelioma with those who did not. Officials hope to determine what aspects of their jobs might have put workers at risk.
That study is projected to cost as much as $1 million over three years. The state will seek federal funding from the National Institute for Occupational Safety and Health and other sources.
The second study, estimated to cost $250,000, would assess health risks associated with airborne mineral fragments from ore mined in some parts of the region. Officials hope to set airborne exposure limits to protect the public from potential health effects, the department said.
The relationship between respiratory disease and mining work has been a concern for people in northeastern Minnesota, where unusually high rates of mesothelioma have been reported among males, the department said. Between 1988 and 2005, 136 cases of the cancer were diagnosed in men who live in that part of the state-more than twice the expected number.
Some of the elevation can be explained by the fact that more than 5,000 people once worked at an asbestos ceiling tile factory in Cloquet. It's not clear how many of the 136 cases occurred in men who were among the 72,000 miners studied in 2003, the department said.
There has been no elevation in mesothelioma rates among women who live in the region.
Also Wednesday, Ohio-based Cleveland-Cliffs Inc. announced it will fund a health study of current and former workers at the Babbitt iron ore mine and Silver Bay processing operations currently operated by Northshore Mining Co.
Cleveland-Cliffs said in a statement that the study will be conducted by an independent firm approved by the state health department and the Minnesota Pollution Control Agency. The Cleveland-Cliffs study is designed to identify whether there are potential health risks associated with mining and processing ore.
A spokesperson for Cleveland-Cliffs did not immediately return a phone message seeking further comment.