Federal regulators have approved a new measure meant to help turn Montana's Big Sky Country into Clear Sky Country.

But the Environmental Protection Agency rule signed Wednesday to reduce haze pollution in Montana follows widespread criticism by industry, conservationists and even other federal agencies.

The proposal aims to reduce emissions of sulfur dioxide and nitrogen oxides that cause haze. It details $85 million in upgrades needed at the Colstrip coal power plant, Ash Grove cement plant near Montana City and Holcim cement plant near Three Forks.

The goal is to restore visibility to natural conditions in national parks and wilderness areas from Idaho to North Dakota by 2064. But conservationists complain the Montana plan would take more than 400 years to do so.

Industry representatives say the rule underestimates costs and overestimates future air improvements.