Residents of Clairton and Glassport are exposed to toxic air pollutants that make their risk of getting cancer around 20 times greater than the national average, according to a new report by the federal Environmental Protection Agency.

The national Air Toxics Assessment report released yesterday calculated the cancer risk for Clairton residents at 762 in 1 million, and for Glassport residents at 700 in 1 million, the third- and fourth-highest risk rates in the nation.

For Tarah Wilcher, whose family has for five decades owned the Clairton News, a North State Street convenience store that backs on U.S. Steel's Clairton Coke Works, only the numbers are news. "There are certain days where there is smog, and it's hard to breathe," said Ms. Wilcher, 26, who has asthma, and whose father suffers from emphysema. "There are a lot of people who have cancer, but I don't know what it's caused from."

The average national cancer risk is 36 in a million. That's down from 41.5 in a million in 2006, when the EPA released its last assessment. But more than 2 million people across the United States still live in areas like Clairton and Glassport, where the lifetime cancer risks from air toxics exceeded 100 in a million -- a rate the federal government deems unacceptable.

"There's been some improvement nationwide since the last time we did this assessment, but this is still a great concern to us," said Dave Arnold, director of EPA's air division in Philadelphia. "I think a lot of the new federal programs are going to help improve the situation -- like new toxic standards for industry and motor-vehicle emission standards, but it will take a while."

Parts of Los Angeles, where vehicle emissions are high, and heavily industrialized Madison County, Ill., near St. Louis, had the highest cancer risks in the nation, at 1,200 and 1,000 in 1 million, respectively.

Weirton, W.Va., where pollutants from industries and coal-fired utilities are high, and parts of Philadelphia, where the air quality is affected by heavy vehicle use, industry and port activity, also had cancer risks that topped 100 in a million.

The cancer risk assessment is based on a 70-year, or lifetime, exposure to predicted concentrations of 124 hazardous air pollutants known to cause cancer, respiratory problems and other health problems. The assessment, based on emissions numbers from 2002, is intended to be used by the EPA and state and county agencies to identify areas of the country in need of more monitoring, analysis and perhaps pollution controls.

"The first thing we need to do is target for further study those areas highlighted as high risk, so we can find out exactly what's going on now," said Dr. Dave Guinnup, an EPA scientist and head of the agency's air pollution risk assessment group.

In Clairton, the monitoring focus is obvious. U.S. Steel's coke works, despite spending hundreds of millions of dollars to reduce air pollution over the last 20 years, remains one of the county's biggest air pollution sources. This year, because of the economic downturn, the steelmaker has suspended a planned $1 billion facility modernization that would have significantly reduced emissions. But it also idled seven of 12 coke batteries, which had the same effect.

"We know there are risks associated with industrial pollutants in the Mon Valley including particulates, organics and heavy metals, but we've seen a tremendous increase in our air quality since 2002," said Dr. Bruce Dixon, director of the Allegheny County Health Department, which monitors coke works emissions.

"You wouldn't build a coke works in a river valley today, but that's how they did it back then, and U.S. Steel has been aggressively trying to reduce its emissions," Dr. Dixon said.

U.S. Steel spokeswoman Erin DiPietro declined substantive comment on the EPA report and the facility's effect on the health of local residents, saying only that the company is reviewing it. Environmental leaders and local residents were less cautious.

John Kaczka, owner of John's Barber Shop in Glassport, said his wife, Betty, often cleans the windows of their house because they are dirtied by the plant's soot particles. "I'm just so disgusted at that place," said Mr. Kaczka, 75, although he did allow that conditions have improved significantly over the past 20 years.

Heather Segina, 34, who has owned her Out of the Ordinary Music and Gifts store on Monongahela Avenue in Glassport for six years, said she notices the coke works' distinct smell every morning when she lets her dogs out. She said her uncle worked there and died of cancer, and her aunt, who has asthma, tells her the condition is worst when she is in Glassport.

Still, she knows the Clairton Works employs a lot of people in the area. "I know it creates jobs," she said. "I know it is important to have people with jobs."

The EPA study is the fourth recently to identify concerns about Allegheny County air quality, including an April American Lung Association ranking that placed Pittsburgh first in the nation for soot pollution and a USA Today report that found four of the seven U.S. schools most at-risk for air pollution are in Allegheny County.

In March, a Carnegie Mellon University study found that when the wind is from the southeast, emissions from U.S. Steel's coke works in Clairton and its Edgar Thomson steel plant in Braddock push fine-particle soot levels above the national health standards in Oakland and Squirrel Hill.

Tom Hoffman, Western Pennsylvania director for Clean Water Action, said the EPA report shows that there are dangerous hot spots of pollution in the county that are unhealthy for residents.

"There have been enough reports to make the case that the air in Allegheny County is not healthy," he said. "It is time to stop attacking the reports and roll up our sleeves and clean up the air."