US: A proposed clean-up of Montana's air pollution by the Environmental Protection Agency (EPA) could cost nearby cement plants up to US$10m. Plans to improve visibility in public land, including Yellowstone and Theodore Roosevelt National Parks, would require upgrades within five years at the Ash Grove cement plant near Montana City and Holcim cement plant near Three Forks.

The EPA's action has been prompted partly by a legal challenge from environmentalists who sued the agency to set deadlines to follow through on haze rules adopted in 1999. Two of the groups involved, WildEarth Guardians and the Montana Environmental Information Center, said that the agency's proposal does not go far enough. Representatives of the groups criticised the EPA's rejection of even stricter pollution limits that would have required tens of millions of dollars in additional spending by the plants.

"People might gasp a little bit and say that's a lot of money but you have to look at how much these companies are profiting off these facilities. It dwarfs these costs," said Anne Hedges with the Montana Environmental Information Center.

The first phase of the EPA's program is aimed at plants built between 1962 and 1977 that churn out at least 250t/yr of pollutants. The goal is to eliminate haze in parks and wilderness areas by 2064. The cost of reducing haze across the US has been estimated at US$1.5bn/yr. Spin-off benefits from reduced health care spending on pollution-related illnesses were estimated at US$8.4bn/yr or more.

The proposal could become final after a 60-day public comment period. Public hearings in Montana hosted by the EPA are scheduled for 15 May 2012 in Helena and 16 May 2012 in Billings.