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Do taconite fibers cause cancer?
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NorthShore Mining Company now operates the former Reserve mine and taconite plant. Waste rock is deposited on land a few miles from Lake Superior. Questions remain about whether taconite fibers pose a human health risk. (Photo courtesy Cleveland Cliffs)
Researchers from around the world are gathering in St. Paul to talk about the possible dangers in fibers in taconite ore. Those microscopic fibers are a lot like asbestos, and asbestos causes cancer. Some studies show the fibers in taconite cause cancer too. Organizers of this week's conference will try to determine once and for all whether taconite fibers pose a health risk. The answer could have a big impact on future mining projects, and the economy of northeastern Minnesota.

Duluth, Minn. — The fibers in taconite first made big news thirty years ago. Reserve Mining Company was dumping its waste rock in Lake Superior, and taconite fibers turned up in Duluth's drinking water.

People panicked and started drinking bottled water, until a special filtration plant was built. Reserve was forced to dump its waste rock on land.

But the jury is still out on whether the fibers are dangerous.

Phil Cook is one of the people who discovered the fibers in the water supply. He's a chemist at the National Water Quality Lab in Duluth. He studied the fibers for years.

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Image Dr. Philip Cook

The fibers are so small, you can't see them even with a regular microscope. Cook and his team pioneered use of the electron microscope to get a handle on the fibers.

"I had people working with me who did an excellent job on the electron microscope," he says. "Hundreds of hours of looking at many fields of view, and counting particles of all sizes and shapes, and identifying them specifically as to what their mineral nature was."

Cook has been asked to bring his research to the conference.

He conducted animal studies to see how likely the fibers were to cause cancer. He compared the fibers in taconite with asbestos fibers, which are known to cause cancer. He injected a carefully controlled number of each type into rats' lungs. After two years, the taconite fibers had produced at least as much cancer as the asbestos, and in some cases more.

He then used an electron microscope to count the fibers still in the lung tissues. The taconite fibers had actually multiplied during their two years in the rats' lungs.

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Image Taconite fiber

"So there was some kind of slow leaching going on while the fibers were in tissue," Cook says. "Blocky particles would become thinner fibers. So the number of fibers were increasing and the dose was increasing." Cook says the very thin, short particles in the taconite fibers caused more cancer than the longer fibers typical of asbestos.

But one of the outstanding questions is: are people who live near the mine exposed to enough fibers to worry about cancer?

For two winters, Phil Cook and his colleagues collected dust from the snow at various locations between the mine and Duluth.

"It was very interesting," he says. "You could see very clear signatures of magnetite from the taconite industry, and I can't tell you from memory right now how far that was, but certainly 20 miles away you could find a trace."

Cook says that means in principle the taconite dust can be transported large distances.

We've got to search out for those young miners that are working now, so they don't end up like some of my friends did at LTV Steel. They're in their 60s and 70s, and can hardly breathe.
- David Trach, retired steelworker, on the importance of screening for lung abnormalities

"Whether or not this has any significance in terms of human exposure as you get further and further away from the source, it's questionable," he adds.

Cook says the way to assess the risk to humans is to nail down how many fibers it takes to cause cancer, and then find out how many fibers are in the air.

NorthShore Mining Company currently operates the former Reserve mine and processing plant. NorthShore monitors its fiber emissions. Millions of fibers pour from the smokestacks. But at monitoring stations about a mile away, the numbers drop to a level comparable to the city of St. Paul.

But some people worry even that level could make people sick.

There are no standards for fibers in the air, either on the national level or in Minnesota.

There are some rules for workplaces. The rules are controversial. Federal mining and occupational health agencies use detection techniques and standards that only look for fibers longer than five microns. Nearly all the fibers in NorthShore's emissions are shorter than that.

Miners and taconite workers are exposed to a lot more fibers than people who live nearby.

Northeastern Minnestoa has a much higher rate of mesothelioma than the rest of the state. Mesothelioma is a rare form of lung cancer caused by asbestos. Some miners are concerned taconite could cause mesothelioma too.

The state Health Department recently completed a study of taconite workers who died of mesothelioma. The study found most of them were exposed to commercial asbestos as well as taconite dust. For many years, asbestos was used in insulation around boilers and pipes. The Health Department study concluded the commercial asbestos was the most likely cause of the miners' disease.

The study looked only for mesothelioma. Some miners say it should have looked for other diseases too. David Trach is president of a Steelworker retiree group. He says 450 former LTV workers got x-rays, and 30% of them had some kind of lung abnormality. Only a very few of them had mesothelioma.

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Image Patricia Bloomgren

"We've got to search out for those young miners that are working now," Trach says, "so they don't end up like some of my friends did at LTV Steel. They're in their 60s and 70s, and can hardly breathe."

The Health Department has file cabinets full of information about the health of miners and taconite workers. Pat Bloomgren directs the environmental division of the state Department of Health.

"There's been a lot of data gatherered that hasn't been analyzed yet on worker health," she says. "And that would help fill out some of the blanks. But we're not sure there'll be an opportunity to do that."

The Health Department had a plan to analyze the data to look for all kinds of lung diseases, but last year the Legislature eliminated the money for the project.

There's a lot riding on whether taconite fibers are safe. Lake County, where NorthShore's plant is located, would like to use the plant's waste rock to build roads. Until now the company has been prohibited from selling its waste rock by the court ruling in the Reserve case.

Also, several companies have been prospecting in the region. New mines for copper, nickel, and other minerals could provide much-needed jobs in a region reeling from closures and cutbacks in the taconite industry.

Brian Hiti is acting commissioner at the Iron Range Resources and Rehabilitation Agency. He says the information coming out of the conference will help state agencies make decisions about those possible projects.

"Looking at new mining projects, or even utilizing mining wastes as aggregate for instance," Hiti says, "this would all be new information that could be used towards that decision-making process."

Papers presented at the symposium will be published a year from now, after a peer review process. Then it's up to the state Health Department to try to determine the risk - if any - from taconite fibers.

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