Updated

The Environmental Protection Agency is delaying new rules that would impose stricter limits on several harmful air pollutants — smog, mercury and soot — drawing complaints from environmental groups who say the Obama administration appears to be caving in to political pressure from congressional Republicans.

Republicans took control of the House and gained in the Senate in the midterm elections, and many GOP lawmakers have vowed to target the EPA for what they call a series of job-killing regulations.

"We're not going to let EPA regulate what they've been unable to legislate," said Rep. Fred Upton, R-Mich., the incoming chairman of the House Energy and Commerce Committee. Upton promised numerous hearings on the EPA under his watch.

Lawmakers from both parties — especially in industrial states in the Northeast and Midwest — have complained about an EPA proposal that would slash mercury and other hazardous air pollutants from boilers and solid waste incinerators, saying it would impose a tremendous cost on manufacturers that could lead to job losses.

Still, environmental groups said the two delays — announced on successive days — appeared to be an attempt to placate GOP critics and stave off efforts in Congress to thwart EPA regulation.

"It is hard to avoid the impression that EPA is running scared from the incoming Congress," said Frank O'Donnell, president of the advocacy group Clean Air Watch.

O'Donnell called the seven-month delay in the smog rule "a bitter pill to swallow" and said the EPA has had nearly a year to evaluate the rule since it was proposed in January.

An EPA spokesman denied that politics played a role and said the delays were needed to ensure the agency's final decisions were grounded in the best science.

While delaying the smog and mercury rules, "EPA is moving forward with a number of national rules that will significantly reduce pollution and improve public health for all Americans," EPA spokesman Brendan Gilfillan said Wednesday.

The rules include steps designed to reduce harmful emissions from cars, power plants and other industrial facilities that contribute to ozone formation, Gilfillan said, adding that the delays would not affect public health.

Sen. Tom Carper, D-Del., chairman of a Senate clean air subcommittee, said he was disappointed by the delay in the ozone rule, which would mean that strict new standards on lung-damaging smog will not take effect Jan. 1 as expected. The EPA now says the rule would take effect by the end of July.

Once in place, the new rules would greatly expand the number of areas in the country exceeding smog standards. Hundreds of communities far from congested highways and belching smokestacks could join big cities and industrial corridors in violation of federal air pollution limits. The proposal presents a range for the allowable concentration of ground-level ozone, the main ingredient in smog, from 60 parts per billion to 70 parts, down from 75 parts per billion as set by the Bush administration.

The delay leaves millions of Americans "unprotected from harmful ozone air pollution under an outdated, ineffective ozone standard," Carper said. "This decision also keeps states in limbo about what standards they need to meet, forcing them to continue to postpone significant decisions today to clean our air tomorrow."

Carper urged EPA Administrator Lisa Jackson to move quickly to finalize plans for new ozone air quality standards.

Gilfillan said the new smog standards would help prevent up to 12,000 premature deaths, 58,000 cases of aggravated asthma and save up to $100 billion in avoided health care costs. The proposed standard would replace a standard set by the Bush administration, which many clean-air advocates called inadequate.

The EPA said 5,000 deaths could be prevented each year under new rules to limit the amount of mercury and other harmful pollutants released by industrial boilers and solid waste incinerators.

The planned rules are intended to cut mercury emissions in half by requiring costly pollution-control equipment to be installed on some 200,000 boilers and heaters at factories, commercial buildings, hotels and universities.

Industrial boilers and heaters are the second largest source of mercury emissions in the United States, after coal-fired power plants. The boilers burn coal and other fuels to generate heat or electricity and are used by petroleum refiners, chemical and manufacturing plants, paper mills, municipal utilities and even shopping malls and universities.

The EPA is under court order to issue final rules by Jan. 16, but the agency in court papers Tuesday asked for an extension until April 2012.

The American Petroleum Institute said it was pleased with EPA's request to delay the ozone rule.

"We also hope EPA will now reconsider other costly and unworkable proposals," such as a planned rule to regulate greenhouse gas emissions, said Howard Feldman, API's director of regulatory and scientific affairs.