ion that has iron particles in it, and it'll be the entirety of all those that probably will lead us to a conclusion one way or the other," he said.
About a hundred residents of the Iron Range gathered to hear the results of the study, and some in the audience questioned researchers about how it was conducted.
Bob Tammen, a retired mine worker, asked if it included enough sampling stations to measure the air quality in Iron Range communities.
"When you get a tailings pond where the beaches dry out and you get a hot dry wind, we've had communities that get tons of dust," Tammen said. "They don't have a sampling station there; they don't pick that up. So we do have situations where we don't have a complete understanding of what the mining companies are doing to our communities."
Researchers said short-term exposure was unlikely to cause health problems.
Some audience members also expressed disappointment that the study was not more conclusive. But overall the response seemed to be one of appreciation that the researchers were taking such care and were continuing to pursue the research.
"We fully understand it's about real people. This is not the last you'll year from us," said Finnegan, the university's public health dean. And he said a nurse line for concerned workers will still be available.
One of the remaining questions is whether federal air safety standards are adequate. Study authors say the air in taconite plants generally meets federal safety standards now. But those standards permit exposure to the extremely small, potentially dangerous mineral particles present in taconite facilities.