U scientists study reasons for higher mesothelioma rate.
The number of Iron Rangers known to have died from a rare form of lung cancer has risen to 82, up from the 63 reported last year by state health officials.
Health officials say they found the additional cases of mesothelioma by checking death records in other states for former Iron Range residents who moved out of Minnesota, the Duluth News Tribune reported Tuesday. The numbers came Monday from a University of Minnesota team leading the long-term Taconite Workers Health Study.
Dr. Jeffrey Mandel, with the university's School of Public Health and the lead researcher on the 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. It also remains unclear where the victims were exposed to asbestos.
Mesothelioma is a rare but almost always fatal lung cancer caused by exposure to asbestos fibers. The disease often takes 30 years or more after exposure to show up.
Earlier reports on the elevated numbers on the Iron Range 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-like fibers within taconite rock released during processing may be causing the mesothelioma -- 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 born since 1920 who worked in the industry, developed some sort of lung cancer.
The study has five parts: an occupational exposures assessment to determine how and where the asbestos came from; a mortality study that reviews the cause of death of 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 will be made public after they are completed, and then a final, overall report is expected to follow.
"We're on target" to have results within five years, Mandel said.
Mandel also said results from more than 2,000 air samples taken over the past two years at Minnesota's six operating taconite operations show no signs of dangerous dust levels, including asbestos. Asbestos levels were extremely low and overall dust levels nearly all met permissible exposure levels under federal guidelines. Silica levels were higher than acceptable 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 in addition to protect workers from dust, he said.