Updated

Faced with a natural gas drilling boom that has sullied the air in some parts of the country, the Environmental Protection Agency on Thursday proposed for the first time to control air pollution at oil and gas wells, particularly those drilled using a method called hydraulic fracturing.

The proposal, issued to meet a court deadline, addresses air pollution problems reported in places such as Wyoming, Texas, Pennsylvania and Colorado, where new drilling techniques have led to a rush to obtain natural gas that was once considered inaccessible. More than 25,000 wells are being drilled each year by "fracking," a process by which sand, water and chemicals are injected underground to fracture rock so gas can come out.

The proposed regulations are designed to eliminate most releases of smog- and soot-forming pollutants from those wells. New controls on storage tanks, transmission pipelines and other equipment — at both oil and gas drilling sites on land — would reduce by a quarter amounts of cancer-causing air pollution and methane, the main ingredient in natural gas, but also one of the most powerful contributors to global warming.

The rules, according to the EPA, actually would save energy companies about $30 million a year because the companies could sell the gas they are forced to collect.

EPA Assistant Administrator Gina McCarthy said the steps announced Thursday will help ensure "responsible production" of domestic energy. The agency is also in the process of studying whether hydraulic fracturing is polluting water, research that also could lead to more regulations on the practice.

In March, pollution from natural gas drilling in the Upper Green River Basin in western Wyoming triggered levels of ground-level ozone, the main ingredient in smog, worse than those recorded in Los Angeles, one of the smoggiest cities in the U.S.

In Dish, Texas, a rural town northwest of Dallas, the state's environmental regulators detected levels of cancer-causing benzene, sometimes at levels dangerous to human health, likely coming from industry's 60 drilling wells, gas production pads and rigs, a treating facility and compressor station.

At the same time, a state study in Pennsylvania of air quality near Marcellus Shale drilling sites in four counties found no emissions at levels that would threaten the health of nearby residents or workers.

The gases escape into the atmosphere during drilling, from storage tanks, compressors along pipelines and other equipment. Until now, the EPA has mainly controlled pollution from natural gas processing plants. States have started to crack down on some emissions from well sites, and industry has voluntarily taken steps to reduce pollution.

The American Petroleum Institute, the main lobbying arm of the industry, pressed the agency to push back by six months its February 2012 deadline for finalizing the rules.

Environmental groups, who sued in 2009 to force the EPA to act, said the action Thursday was already overdue.

"Solutions for clearing the air mean keeping more product in the pipelines," said Jeremy Nichols of WildEarth Guardians, an advocacy group.

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Follow Dina Cappiello on Twitter: (at)dinacappiello