New Analysis Provides Additional Information About Miners Diagnosed with Mesothelioma

Critically important information on where miners worked--and for how long--will be used in preparing and executing proposed studies  

(Dec. 7, 2007) -- The Minnesota Department of Health (MDH) has completed a new analysis of available information about 58 mine workers who have previously been diagnosed with mesothelioma.

The analysis showed great variation in the length of time the workers were employed in the industry, that they worked at locations all across Minnesota's Iron Range, and that they were not diagnosed with mesothelioma until decades after they first started work in the mines.

"The Minnesota Department of Health has been studying elevated rates of mesthothelioma on the Iron Range for a number of years," said Minnesota Commissioner of Health Dr. Sanne Magnan. "This new analysis provides additional insights that will help to answer questions and prepare for additional work."

The analysis was performed in preparation for studies to be conducted by the University of Minnesota, in collaboration with MDH, aimed at determining what might have caused the illness.

"This analysis provides us with an important piece of the puzzle as we prepare to study this issue," said John R. Finnegan Jr., Dean of the University of Minnesota School of Public Health. "Questions about mining work and respiratory health have been with us for a long time. This is an important first step in finding some answers."

The 58 miners--all of whom are men--are part of a group of 72,000 people who worked in the state's iron mining industry between the 1930s and 1982. MDH has been tracking the occurrence of mesothelioma in this group using information from the Minnesota Cancer Surveillance System (MCSS).

Mesothelioma is a rare, fatal form of cancer seen almost exclusively in people who have been exposed to asbestos. Unusually high rates of mesothelioma have been reported among men in northeastern Minnesota since the late 1980s, raising questions about a possible relationship between respiratory disease and mining work. Those questions include the possible role of mineral fibers found in taconite dust as a cause of mesothelioma. 

Among the findings of the new MDH analysis:

• Almost one-fourth of the 58 workers were employed in the industry for less than one year, while over a fourth were employed for 30 years or more.
• All but one of the miners who developed mesothelioma were diagnosed 30 years or more after they first went to work in the industry. In five of the cases, the time lag was 60 years or longer.
• The miners worked at locations scattered across the Iron Range, including all but one of the seven mining operations that were active during the period when they were employed. The exception -- Inland Steel -- employed only 618 of the 72,000 miners in the group being followed by MDH.
• Only three of the 58 miners ever worked at the former Conwed plant in Cloquet, which manufactured asbestos ceiling tiles between 1958 and 1974. The Conwed facility is believed to have contributed significantly to elevated mesothelioma rates in northeastern Minnesota, accounting for 25 cases of the illness among the 5,200 people who worked there.