A six-year study of the taconite industry's effects on air quality in northeastern Minnesota is sparking scientific criticism that the still-unpublished findings won't reveal much about residents' exposure to mining dust.

Outside scientists advising the University of Minnesota-Duluth research team have questioned the study's methods, according to e-mails obtained by the Star Tribune.

One has even questioned the researchers' assertion that air on the Iron Range is "safe to breathe," which was presented as a key finding at a community meeting in 2013.

"This may indeed be true, but not if the statement is based on the data from this study," wrote Daniel Vallero, a research scientist at the National Exposure Research Laboratory in North Carolina.

The air quality research is part of a broader $5 million study prompted by high rates of a rare, deadly lung cancer called mesothelioma in iron ore miners. The most pointed critique of the community study has come from Vallero, a top U.S. Environmental Protection Agency (EPA) scientist, who says it was an "inherent flaw" for UMD researchers to sample air on eight rooftops and inside six taconite plants without developing a plan to ensure quality science and clearly define research objectives up front. At the EPA, such research blueprints are required.

"Indeed, collecting information first and then applying the results is akin to shooting an arrow at the wall and then drawing the target around it," Vallero said in e-mails.

The UMD air-sampling results were once portrayed as findings about "community exposure" to pollutants, but the lead researcher says that was never the intent of the study.

George Hudak, who leads the minerals division at UMD's Natural Resources Research Institute, said researchers are removing the word exposure from descriptions of the work to avoid misunderstanding.

"It is a characterization study, not an exposure study," Hudak said.

UMD researchers studied the size and makeup of airborne dust, and detailed results will be submitted in April to the Legislature, which funded the study, he said.

At a recent presentation in Hibbing, researchers said Iron Range air has low concentrations of mineral dust, with rare detections of longer particles, which are a focus of the health concerns. Particle concentrations were lower in the Iron Range samples than on a rooftop at the U in Minneapolis, and about the same as a remote sampling site near the Boundary Waters.

Only the study of Iron Range communities' air has received such criticism from its Science Advisory Board. A related study of disease in miners by U health researchers in the Twin Cities has not faced similar questions.

Hudak said the UMD research team will address concerns by Vallero and another scientific adviser in the final report. He said one reason that the study started before completing the research blueprint is that some taconite operations temporarily shut down in 2008, and researchers moved quickly to sample the air at inactive plants.

Another science adviser, D. Wayne Berman, a California-based expert in asbestos risks, also has been critical. In an e-mail, Berman questioned the "evolving sampling design," and warned that it "weakens the overall power of the study." A study blueprint, known as a Quality Assurance Project Plan, is needed "before we can be fully confident we are addressing the right issues," he wrote more than three years into the study.

Dust worries residents

Mining dust has long been a concern for Iron Range communities such as Keewatin, Minn., which received $60,000 for a new street sweeper from U.S. Steel in a 2008 agreement over dust rising from the company's iron ore tailings basin to the south. Two years later, the town haggled with Magnetation about dust rising from that company's mineral extraction operations to the north. Dust clouds are common when the wind is up and the weather is dry, said Mayor Bill King.

"Health issues were a big concern in all of our community meetings," King said.

Mike Sinko of Chisholm is a former miner who has lung scarring similar to what U researchers found when they examined a sampling of current and former miners. He lives near Hibbing Taconite, and the prevailing west winds often bring dust that grays the snow or dulls his glass patio table. Last month, he said, a dust cloud was so thick he thought it was snowfall.

While he believes the companies are making an "honest effort" at solutions, he has been disappointed so far that the U research hasn't clarified the potential health hazards beyond the mines.

"You never get a thorough answer," he said. "That's the way it is."

'Not qualified'

Hudak said the UMD work was not intended to assess the human health risk of dust in Iron Range communities. Studying residents' exposure to dust would require a more exhaustive and expensive approach — an idea that scientists considered as a follow-up to this characterization study, but haven't pursued.

The UMD researchers are "mineralogists and geologists," he said. "So we are not able to make statements regarding whether it is safe or not safe to breathe the air. We're not qualified to do that."

The most significant community-based finding of the U miner research has come from health tests of miners' spouses. Unlike the miners, they do not show elevated rates of lung abnormalities or disease. Last week, the state Health Department released new data showing 21 additional miners stricken with mesothelioma, for a total of 101 since the cluster was first identified in 2003. Almost all have died.

University health researchers have found that iron ore workers are stricken with mesothelioma at more than double the expected rate for the asbestos-related cancer. The research has linked miners' illnesses to taconite dust exposure over many years, but has not explicitly blamed taconite particles. Commercial asbestos used decades ago in mining operations remains the prime suspect in the cancers.

When disease is linked to an industrial source, it's not uncommon for researchers to check nearby communities' air for hazards. Chris Weis, a toxicologist formerly employed by the EPA, said the agency carefully studied community exposures in Libby, Mont., site of a former vermiculite mine. Since 1999, hundreds of cases of mesothelioma have been linked to asbestos exposures at the mine and in the town.

In an interview, Weis said it would be unfair to the UMD researchers to judge their work before the final study results are released. But he said monitoring the air on rooftops is not the same as testing residents' exposure

In Libby, researchers wore air-sampling devices to mimic what people breathe in the community, he said. On the Iron Range, that kind of sampling was done in the mines, but not in the community.

"Without that monitoring," Weis said, "you absolutely don't know what people are exposed to."