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Sunflower Electric Cooperative's coal-fired power plant churns out electricity on Feb. 2, 2007, in Holcomb, Kan. The EPA has proposed the first national standards for limiting mercury and other toxic emissions. (Charlie Riedel, file/The Associated Press)

The U.S. Environmental Protection Agency proposed on Wednesday the first national standards for limiting mercury, arsenic and other toxic air pollution from power plants in the United States.

If the proposal becomes law, it would force many plants to install pollution-control technologies to cut harmful emissions.

Canadian municipalities have long called on the EPA to mandate reduced emissions from coal-fired plants in U.S. Midwestern states.

According to the Ontario government, about half of the 5,000 premature deaths caused by smog in the province every year can be attributed to air pollution that crosses the Canada-U.S. border.

There are currently no limits on how much mercury or other pollutants can be released from a power plant's smoke stacks in the U.S. The EPA said the new regulations — which, if passed, could go into effect by 2014 — would reduce mercury emissions from these power plants by 91 per cent.

In the U.S., power plants are responsible for half of mercury and more than half of acid gas emissions, according to the EPA, which says that in the power industry, coal-fired plants are responsible for 99 per cent of mercury emissions.

"Currently, more than half of all coal-fired power plants already deploy the widely available pollution-control technologies that allow them to meet these important standards," the EPA said Wednesday in a release. "Once final, these standards will ensure the remaining coal-fired plants, roughly 44 per cent, take similar steps to decrease dangerous pollutants."

Such rules would have the greatest impact on Texas, which is home to more coal-fired power plants than any other state. Texas has at least 17 coal-fired plants and about a dozen more in various stages of the permitting process.

Mercury can cause neurological damage, including lower IQ in children exposed in the womb and during early developmental stages. Arsenic, chromium and nickel — also targeted for emission reduction — have been linked to cancer.

The EPA's proposal is in response to a court order to regulate mercury and other air pollutants. The agency will be holding public hearings in the proposal in the coming months.

With files from The Associated Press