The number of Iron Rangers who died of mesothelioma has reached 82, up from 63 when last reported by state health officials in 2010.
Health officials say they found the additional cases by checking death records in other states for former Iron Range residents who moved out of Minnesota.
That was the report today from the University of Minnesota team that is heading the long-term Taconite Workers Health Study. The study, which started in 2008, could be completed as early as mid-2012.
Dr. Jeffrey Mandel, an associate professor at the University of Minnesota's School of Public Health and lead researcher in the Iron Range study, said a "back-of-the-envelope" analysis shows the mesothelioma rate is considerably higher than it should be.
"But we are still doing the analysis to find out how much so," Mandel said in a telephone news conference.
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It also remains unclear where the exposure to asbestos occurred.
Mesothelioma is a rare but always fatal lung disease, caused only by exposure to asbestos fibers, which often takes 30 years or more after exposure to show up.
Earlier reports on the Iron Range phenomenon suggested the asbestos exposure came from workers who dealt with commercial asbestos, such as insulation on pipes, furnaces and boilers. But others have speculated that asbestos fibers within taconite rock released during processing may be causing the mesothelioma problem -- speculation that spurred the $4.9 million health study approved by state lawmakers in 2008.
"We've basically concluded our data collection phase," said John Finnegan, dean of the University's School of Public Health. "It's an enormous number of people we have data on now... people who worked in mining back to the 1920s."
Early results also show that 1,681 taconite workers, of about 46,000 who ever worked in the industry, developed some sort of lung cancer. Again, it's not clear if that rate is higher than normal, and it may never be clear if the cancers were caused by exposure to taconite dust, smoking or a combination of factors.
It's estimated about 80,000 workers have been involved in mining since the first operations began in Minnesota in the late 1800s. Researchers are focusing on the roughly 46,000 people born since 1920 who worked in the production of taconite -- a low-concentrate iron ore that has been mined and processed in Minnesota since the 1950s.
The study has five parts, including: an occupational exposures assessment to determine how and where the asbestos came from; a mortality study that reviews the cause of death for deceased taconite workers; a cancer incidence study to see whether cancer rates are higher on the iron Range; an environmental study of current airborne particulates to check for asbestos levels; and a respiratory health study of living taconite workers and their spouses.
Results from each study will be made public after they are completed, and a final, overall report is expected after that.
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"We're on target" to have results within five years, Mandel said.
CURRENT DUST LEVELS OK
Mandel also reported Monday that results from more than 2,000 air samples taken over the last two years at Minnesota's six operating taconite operations show no signs of dangerous dust levels, including for asbestos.
Asbestos levels were extremely low and overall dust levels nearly all met permissible exposure levels under federal guidelines. Silica levels were found to be higher than acceptable levels in some cases, but researchers who went into the plants found that the dust control technology in use was appropriate.
"That's good news," Mandel said. "There's nothing missing" that taconite companies should be doing to protect workers from dust.
Meanwhile, data is still being crunched from health testing conducted last year on 1,300 current and former taconite workers and 500 of their spouses. The Rangers, randomly selected by university researchers and who participated voluntarily, filled out health questionnaires, provided blood samples, had chest X-rays and completed tests to measure their lung function.
