HIBBING, Minn. – University of Minnesota researchers have discovered fresh evidence linking inhaled taconite dust to lung disorders in miners on the Iron Range, including scarring around the lungs and a rare cancer called mesothelioma that has killed 80 workers.

The final report in a six-year study, released Monday, found that workers exposed to high levels of airborne mineral fibers were more than twice as likely to develop the cancer than miners exposed to low levels. The finding fortifies the scientists' earlier discovery that miners who worked more years in the taconite industry stood a higher risk of mesothelioma.

Researchers said the historic study, funded by a $5 million grant from the Minnesota Legislature, underscores mining's risks, but doesn't mean the industry is unsafe. No risk was found to communities surrounding the mines, nor did spouses show elevated rates of lung diseases or abnormalities.

"Under most normal operating conditions, the plants are safe," said Dr. Jeffrey Mandel, a University of Minnesota physician and epidemiologist who headed the study. "But it is an inherently dusty industry. And it has risks."

Over six years, researchers studied disease incidence and mortality among miners, conducted comparative studies of workers who got sick and those who didn't, assessed dust exposure in mines and communities, and screened workers and spouses using X-rays and breathing tests.

Among other results, the study found that taconite workers with at least 21 years on the job are 60 percent more likely to have scarring on the lining of their lungs than workers with less time in the industry. The scarring, a potential early warning of disease, also was twice as common in workers exposed to high levels of fiberlike dust, the study found.

Scientists released the results at a community meeting in Hibbing. About 70 people attended, including Edward Alto, 65, of Aurora, a retiree from the LTV mine. Using statistics provided by the U study, he figured his 33 years of mining almost doubled his risk of mesothelioma. He discovered abnormalities in his lungs through participation in the research, and knows the findings won't help him much.

"There's no going back," he said, "but maybe for the next generation of miners."

During Monday's presentation, researchers urged the use of respirators and other protective gear. "The whole key to this is avoiding exposure," Mandel said.

Response to findings

Mining companies, which contributed data but no funding to the U research, declined to answer questions, but said in statements or through a trade group that they were encouraged by the results.

"Going forward, the taconite industry continues to be committed to providing a safe working environment for our employees," said Craig Pagel, president of the Iron Mining Association of Minnesota.

Christopher Weis, a toxicologist and senior adviser in the National Institute of Environmental Health Sciences, said the findings support earlier research linking dusts produced by taconite mining to asbestos-related disease. He said regulators will need to rethink how they classify hazardous mineral fibers. Federal rules focus on longer fibers found in commercial asbestos, and don't address the predominately shorter fibers in taconite dust.

"Our use of old fiber measurement techniques, designed for protecting asbestos production workers, do not accurately define exposures," said Weis, who was not involved in the study and did not attend the meeting.

The United Steelworkers, which represents 3,300 workers in Iron Range mines, said it has long pushed the Mine Safety and Health Administration (MSHA) for tougher standards on fiberlike and silica dust. "Hopefully this will be enough to push the federal regulators and maybe see some positive changes," said John Rebrovich, assistant to the director of USW District 11.

MSHA spokeswoman Amy Louviere said the agency had not seen the report and could not comment.

Rebrovich said taconite companies have upgraded dust-collection equipment, but said the study shows a need for better dust control. "It is going to cost some money," he said. "But what is the cost of a person's life?"

Mandel said the research team's most unexpected discovery — a roughly 30 percent higher-than-expected death rate from heart disease among miners when compared with the overall working population — could be linked to inhaling ultrafine dust particles in mines. He said the finding gives miners a powerful reason to confront known heart disease risks — smoking, high blood pressure and elevated cholesterol.

Risk on the job

The final report brings scientists closer to understanding the health risks to more than 16,000 current and former miners at eight operating and closed taconite operations from Nashwauk to Babbitt.

The study was launched after the Minnesota Health Department linked additional miner deaths to mesothelioma in 2006, but withheld the research for a year. When the Star Tribune revealed that the agency had suppressed the study, it provoked a public outcry that led to legislative funding of the study.

Matthew Struna is fairly confident that 30 years of inhaling dust while working in heavy equipment maintenance for Reserve Mining contributed to the death of his father, Joseph "Fishy" Struna, at age 86 two years ago. Matthew Struna said he had never really asked his dad about his work until after his diagnosis with mesothelioma, and then he discovered his father rarely wore masks or protective equipment.

"He worked servicing brakes … on some of the big shovels up there," Struna said. "He would have been in confined work spaces, using air hoses, blowing out brake drum dust and all of that kind of stuff back in the day."

Questions unanswered

Scientists said key questions remain unanswered, especially whether the mines' use of commercial asbestos decades ago still haunts the taconite industry today.

Fear of asbestos on the Iron Range emerged after 1973, when fibrous minerals showed up in Lake Superior from tailings dumped by Reserve Mining Co. It ignited a debate over the risk on the Iron Range. Commercial asbestos is a known cause of mesothelioma, a cancer of the lung lining that usually surfaces years after exposure. Like asbestos, taconite dust particles can have a needlelike shape, but are shorter and chemically different.

U scientists said they can't rule out historic exposures to commercial asbestos in the Iron Range diseases, and urged continued study. The university is seeking $6.25 million in mining research funds from the Legislature in 2016-17.

"This is something that for the health of the workers really does require ongoing examination and care," said Prof. John Finnegan, dean of the U's School of Public Health.

Dr. Michael Harbut, a professor at Wayne State University who is an expert on asbestos-related disease, said screening with X-rays can undercount lung disorders in a population, and more advanced testing might show more disease on the Iron Range.

"It doesn't tell us as much," said Harbut, who was not involved in the study but reviewed the results for the Star Tribune.

Struna, a retired FedEx pilot in Tennessee, wasn't at Monday's presentation, but said he hopes the research continues because premature death of miners like his father is tragic. He said he misses fishing at the cabin near Ely with his father, and hearing him play his accordion for his grandchildren and at local events.

"He was a good old Joe, so to speak, a great father," Struna said. "Wish we had him around yet."

Staff writer Glenn Howatt contributed to this report. jeremy.olson@startribune.com • 612-673-7744

david.shaffer@startribune.com • 612-673-7090