The latest announcement from the Minnesota Health Department serves as a grim reminder of the potential health dangers facing the state's miners.
In a Tuesday morning release, officials say they've found 21 new cases of mesothelioma – a rare form of lung cancer often caused by asbestos exposure.
The MDH says the cases are the latest to be identified in a group of 69,000 mine workers who have been under study since the late 1990s. The announcement brings the total number of mesothelioma cases to 101.
The workers were employed in Minnesota’s iron mining industry between the 1930s and 1982. However, the release points out that those miners worked in a "number of places across the Iron Range, and were not limited to any one" mining operation.
Officials say their study of the mine worker group has gone on amid "generally elevated mesothelioma rates in northeastern Minnesota," which is dominated by the mining industry. They point out, however, that the disease is primarily a workplace threat and not a community-wide one.
"The state’s long-term study determined that this is no broader threat to communities, noting that even spouses of miners did not have a higher disease rates -- only the miners themselves," the Duluth News Tribune said.
The MDH can't rule out the "dust generated by taconite processing...and other mineral fibers" as a possible cause of the lung disease, according to the release.
How does mesothelioma work?
A disturbing aspect of the disease is that it can take decades to appear after exposure to asbestos or other cancer-causing materials.
“This form of cancer has an extremely long latency period,” said Dr. Ed Ehlinger, Minnesota Commissioner of Health. “The interval between exposure to the agent that causes the cancer and the time when the cancer appears can be as long as 40 or 50 years, possibly even longer."
He added that the health department expects to see more cases going forward.
Asbestos, which is frequently linked to the cancer, is a strong mineral fiber used in a wide variety of construction and automotive materials for its flame-retardant properties, according to the U.S. Environmental Protection Agency.
The agency points out that while it has been banned for some uses, the fiber remains legal and widespread.