Mining companies in northern Minnesota could face penalties and dust-control mandates under a new federal regulation that sharply limits asbestos in workplace air.

Under a regulation issued Feb. 29, the amount of asbestos allowed in mine air is 5 percent of what's now permitted. The new rule gives miners the same protection that other workers have had since 1994.

The federal Mine Safety and Health Administration since 2003 has identified five U.S. mine operations that have asbestos above the new limit. Two of them are in Minnesota.

Now, under the rule that takes effect April 29, federal regulators have the authority to order companies to reduce dust if testing shows that airborne asbestos is above the new limit. In the past, mine regulators urged mine companies to voluntarily meet the lower target.

That's what has happened at Northshore Mining's ore plant in Silver Bay, Minn., where needle-shaped asbestos fibers have been detected repeatedly since 2003, according to federal test results.

Testing at Northshore's mine in Babbitt, Minn., also found asbestos in the air.

Dana Byrne, spokesman for Northshore owner Cleveland-Cliffs Inc., said the company has installed additional dust collectors and other equipment to protect workers.

"The health and safety of our employees comes first," he said.

Byrne said the fibers in Northshore air samples are not asbestos, but non-asbestos fragments. If future federal tests indicate asbestos above the new limit, the company may challenge the regulators' methods, he added.

Federal air sampling at four other mines on the Iron Range turned up no asbestos.

Asbestos causes a rare, deadly cancer called mesothelioma, which affects Minnesota miners at higher rates than other workers. State-funded studies aim to settle whether the source of the dangerous fibers is mining dust or commercial asbestos that was widely used in the mining industry.

Gerald Holeman the Duluth-based assistant district manager for the Mine Safety and Health Administration, said asbestos air sampling will continue in Minnesota mines where there is an "overexposure potential," though he would not identify the mines. The testing requires workers to wear air-sampling devices for an entire shift.

If a mine exceeds the new asbestos limit, he said, regulators would issue a citation and order workers to wear approved respirators. Regulators also can levy fines and order the company to install ventilation and dust-collection equipment or to take other preventive measures, such as spraying water to reduce dust.

Mike Wright, who oversees worker safety issues for the United Steelworkers, said the union is studying the new regulation, and intends to push for improved dust control in mines.

David Shaffer • 612-673-7090