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Study: Iron Range miners show higher cancer rates but reasons unclear

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U of M researchers presented findings
University of Minnesota epidemiologist and principal investigator Jeffrey Mandel and other public health researchers discuss the results of the Taconite Worker Health Study with a crowd of about 50 mineworkers and others at the Hibbing Memorial Building on Monday, Dec. 1, 2014.
Dan Kraker / MPR News

Updated 8:30 a.m. | Posted 4:30 p.m.

Iron Range miners show higher than expected rates of cardiovascular disease, lung cancer and a rare cancer known as mesothelioma — but it's not clear if taconite ore is what's making them sick. 

Those are the conclusions from the final report of a six-year University of Minnesota study into the health of Iron Range miners released Monday.

For decades, some miners have wondered if microscopic needle-like fibers found in the dust of crushed taconite iron ore can lodge into workers' lungs and cause respiratory diseases including mesothelioma, a deadly cancer of the lining of the lungs that's killed 80 former mine workers on the Iron Range. 

The $4.9 million study, which began in 2008, linked time spent working in the taconite industry to a higher risk of mesothelioma.

It found every year spent working in the industry increased the risk of contracting mesothelioma by 3 percent and that Iron Range mine workers suffered the disease at three times the rate of Minnesota's general population. It also linked exposure to the tiny fiber-like particles to mesothelioma.

University researchers, however, said they were unable to pinpoint an exact cause of the diseases. 

Many early workers in the taconite industry frequently handled asbestos, a known cause of mesothelioma, and researchers were unable to distinguish between exposure to those fibers from commercial asbestos and exposure to fibers in taconite dust. 

"It's really difficult to separate out the different fiber types," said Jeffrey Mandel, principal investigator of the Taconite Workers Health Study. "All we can say is there is a relationship between fiber-like exposure and the mesothelioma, but we can't break it down any further than that."

Officials unveiled the findings Monday in Hibbing to a room filled with former miners and their families, state legislators and others.

Miners and others with a deep stake in the matter were frustrated by the lack of a conclusion after six years of study and millions of dollars spent.

"It's exactly what I thought they would come up with — very vague, saying one thing, like there's a relationship between the exposure, but the dust is not attributable to it. Well, that's just nonsense," said Robert Bassing, who worked for 33 years at MinnTac, the state's largest taconite plant, in Mountain Iron.

"How can you have a relationship to the dust causing something, but it's not a factor?" he asked.

Former state legislator Tom Rukavina
Former state legislator Tom Rukavina helped secure $4.9 million for the study back in 2008. ''I think the U of Minnesota did what we asked them to do,'' he said at the meeting on Dec. 1, 2014, in Hibbing, Minn. ''Can you specifically say that our taconite ore is causing our miners to have lung disease and get mesothelioma? And I think the answer is, we can't say that.''
Dan Kraker / MPR News

Long search for a cause

Questions about the potential health dangers of working in the taconite mines have vexed people in northeast Minnesota for decades. 

In 1973, mineral fibers were found in the Duluth water supply and traced to taconite waste rock dumped into Lake Superior in Silver Bay. In the 1980s, an Iron Range radiologist reported unusual numbers of lung abnormalities in his patients' X-rays.

The Minnesota Department of Health in 1999 confirmed a much higher rate of mesothelioma among men in northeast Minnesota than men in the rest of the state. Four years later a Health Department study concluded the most likely cause was the commercial asbestos mine workers handled in various parts of the taconite production process. That doesn't happen anymore in modern taconite facilities.

But some workers still wondered whether tiny particles found in the dust of crushed taconite rock might be causing mesothelioma and the other diseases.

Those fears resurfaced in 2007, when it was discovered the state Health Department withheld findings of additional mesothelioma victims for a year while it conducted more research. That outraged Iron Range legislators, and led to state financing of the study, and the final results released Monday. 

Higher rates of heart disease

In addition to mesothelioma, the study also found taconite workers had higher than expected death rates from lung cancer and heart disease when compared to the general population in Minnesota. 

But while exposure to the fiber-like minerals was linked to the increased levels of mesothelioma — workers with above-average exposure to dust containing the particles were twice as likely to develop mesothelioma as workers with below-average exposures — it was not found to be a cause of the elevated rates of lung cancer. 

Similarly, workers who worked for a longer length of time in the industry had a greater risk of contracting mesothelioma, but a similar connection was not found with lung cancer. 

"Even though lung cancer is present in amounts higher than expected," said Mandel, an epidemiologist and physician, "the lung cancers don't appear to be related to those exposures (to the fiber-like materials)."

Researchers also found increased mortality from cardiovascular disease among mine workers. "We didn't expect to find elevated rates of heart disease," said Mandel. 

The study found mine workers on the Iron Range had a 30 percent greater chance than expected to die from heart disease. Mandel called it an important finding, given that heart disease is much more common than either mesothelioma or lung cancer. 

There are many risk factors that could contribute to those high rates, including smoking, high blood pressure and cholesterol. 

But researchers also said recent medical literature suggests a relationship between exposure to tiny dust particulates and heart disease — particulates smaller than the fiber-like particles linked to mesothelioma examined in this study, but that are common in dusty mining operations and other industrial facilities. 

The University of Minnesota study wasn't set up to find a potential link between the smaller airborne dust particles and elevated rates of cardiovascular disease. But given the elevated rates they found, and evidence in other studies of a link to dust exposure, the researchers recommend mining companies, unions and Iron Range communities make efforts to control known risk factors. 

The scientists also say they should consider "the potential for cardiovascular disease to be related to dust exposure." 

David Mlaker, safety chair at Keewatin Taconite
David Mlaker, safety chair at Keewatin Taconite and member of the Steelworkers local union 2660 questions public health researchers Dec. 1, 2014 at a meeting in Hibbing, Minn.,, about the cause of elevated rates of mesothelioma among mineworkers on the Iron Range. ''The one part of the study that we were really looking to find out... basically wasn't answered,'' he said.
Dan Kraker / MPR News

'A very dusty industry'

The Iron Range's six operating taconite mines and processing facilities generally meet federal air quality standards, and are safe places to work under normal operating conditions, researchers stressed. "I think that question (whether it's safe to work in the industry) is no longer on the table," Mandel said. 

Still, "by its very nature, it's a very dusty industry," said environmental sciences professor Gurumurthy Ramachandran. 

While researchers found that dust consistently meets federal occupational health standards for longer fiber-like minerals found, for example, in commercial asbestos, those federal standards don't measure for the shorter particles found in taconite rock. 

The mining operations also don't always meet federal standards for silica dust, a known toxin, said Ramachandran. "With respect to the silica exposures, the companies could do a better job," he said. But elevated silica levels are not unique to the taconite industry," he added. "That is common across any dusty industry across the country."

Chest X-rays also revealed higher than expected rates of lung scarring among mine workers. Researchers attempted to find a link between silica exposure and the scarring, but said it was difficult to do accurately. 

"It's still possible that the scarring is from silica," said Ramachandran. "It's definitely higher than it should be compared to the non-exposed population. So we know something is going on, but we can't get our arms around it entirely as being one type of exposure or another." 

Edward Alto, who worked for 33 years at LTV Steel outside Hoyt Lakes, has been diagnosed with scarring of the lining of the lungs. Doctors have told him it's not pre-cancerous, but Alto says still it's "like living with a time bomb."

He remembers dusty conditions at the mine.  

"Maybe down the road there will be some answers for the future generations," Alto said. "The future miners will be better armed to protect themselves, with better engineering controls, to handle the dust."

Recommendations

Researchers made 10 recommendations based on their findings. Among them: mining operations should consider the mandatory use of personal protective equipment, or PPE, in "high-exposure circumstances," or where the exposure potential is high or unknown. 

"There is a general understanding that PPE is not being used to the extent that it should be," said Ramachandran. "There are good reasons why somebody might not want to do it, he said, noting that some workers find the equipment cumbersome, hot and bulky. "But in terms of health protection, it's important you do wear them."

Researchers also recommended programs to get miners to quit smoking, and to evaluate the medical monitoring programs currently in place at the mines. 

Despite the study's failure to find a conclusive cause of mesothelioma and other diseases, researchers say they developed a broader understanding of the risks that mine workers face in the taconite industry. 

"It underscores that this is not a risk-free industry," said John Finnegan, dean of the U's School of Public Health. "Mining isn't going to go away in Minnesota. This is something that for the health of the community, for the health of the workers, it really does require ongoing examination and care."