US: The Environmental Protection Agency (EPA) has approved a new measure meant to help approve US state Montana's levels of haze pollution. The signing 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 US$85m in upgrades needed at the state's major contributors of small particles that contribute to park haze, mainly at the Colstrip coal power plant. Holcim's cement plant near Three Forks requires selective non-catalytic reductions totalling US$1.32m to achieve annual NOx emissions reductions of 556t/yr. Ash Grove cement plant near Montana City requires selective non-catalytic reductions and low NOx burners totalling US$1.19 to achieve annual NOx emissions reductions of 1088t/yr.

Many of the commenters, including Holcim and Pennsylvania Power and Light, questioned the computer models used to calculate the effect of various technologies on emissions. Companies also complained that the EPA underestimated the costs required to retrofit their plants with new equipment. In response to a Holcim comment, the EPA decided that Holcim did not have to install lime injection and scrubbers because the reduction in emissions didn't justify the cost. The total price tag for Holcim was originally estimated at US$6.2m.

Under the Clean Air Act, the air in national parks and wilderness areas in the US is supposed to be as clean as possible. To achieve that goal, regional haze programmes in several states set pollution limits on industries. The goal is to restore visibility to natural conditions in national parks and wilderness areas from Idaho to North Dakota by 2064.