The Environmental Protection Agency on Friday issued its first major regulation since the Nov. 6 election, imposing new air quality rules on soot pollution in what critics called evidence of a post-election "regulatory cliff."

The EPA rule reduces by 20 percent the maximum amount of soot released into the air from smokestacks, diesel trucks and other sources of pollution.

EPA Administrator Lisa Jackson said the new standard will save thousands of lives each year and reduce the burden of illness in communities across the country, as people "benefit from the simple fact of being able to breathe cleaner air."

But the new soot standard has been highly anticipated by environmental and business groups, who have battled over whether it will protect public health or cause job losses.

The American Petroleum Institute warned Friday that the new rule "is unnecessary and could drive up costs for new and expanding businesses trying to hire employees."

"There is no compelling scientific evidence for the policy decision to develop more stringent standards. The existing standards are working and will continue improving air quality," API Director of Regulatory and Scientific Affairs Howard Feldman said in a statement. "We fear this new rule may be just the beginning of a 'regulatory cliff'."

Feldman was referring to a host of forthcoming environmental regulations. Sen. James Inhofe, R-Okla., who for months has been warning about those regulations, called Friday's announcement "the first in an onslaught of post-election rulemakings that will place considerable burdens on our struggling economy."

"And so it begins," Inhofe said.

Announcement of the new standard met a court deadline in a lawsuit by 11 states and public health groups. The new annual standard is 12 micrograms per cubic meter of air, down from the current 15 micrograms per cubic meter.

Soot, or fine particulate matter, is made up of microscopic particles released from smokestacks, diesel trucks, wood-burning stoves and other sources and contributes to haze. Breathing in soot can cause lung and heart problems, contributing to heart attacks, strokes and asthma attacks.

Environmental groups and public health advocates welcomed the new standard, saying it will protect millions of Americans at risk for soot-related asthma attacks, lung cancer, heart disease and premature death.

Dr. Norman H. Edelman, chief medical officer for the American Lung Association, said a new standard will force the industry to clean up what he called a "lethal pollutant."

Reducing soot pollution "will prevent heart attacks and asthma attacks and will keep children out of the emergency room and hospitals," Edelman said in a statement. "It will save lives."

But congressional Republicans and industry officials called the new standard overly strict and said it could hurt economic growth and cause job losses in areas where pollution levels are determined to be too high.

Ross Eisenberg, vice president of the National Association of Manufacturers, said the new rule is "yet another costly, overly burdensome" regulation that is "out of sync" with President Barack Obama's executive order last year to streamline federal regulations.

The new rule will "place many promising new projects --and the jobs they create -- into permit limbo," Eisenberg said.

Jackson and other administration officials said the new rule was based on a rigorous scientific review. Only 66 of more than 3,000 U.S. counties would fail to meet the proposed standard, which takes effect in 2014. All but seven counties should meet the proposed standard by 2020 with no additional actions needed beyond compliance with existing and pending rules set by the EPA, the official said.

The administration has said it will work with states and counties to ensure they can meet the new soot standards by 2020, when stronger enforcement of the rule is expected.

The Obama administration had sought to delay the new soot standards until after the November election, but a federal judge ordered officials to act sooner, and the administration released a draft proposed rule in June.

The Associated Press contributed to this report.