A federal study that reviewed 177 chemical pollutants found that New York State has the dirtiest air in the nation and an elevated cancer risk that goes with it.

The Environmental Protection Agency, which released the study, immediately drew criticism.

Some scientists said the agency was not doing enough to crack down on industrial polluters, while other environmental specialists said there is not enough scientific evidence to link poor air quality to cancer, and that doing so was alarmist.

“Air pollution has been trending downward,” a senior policy analyst on energy and environment at the Heritage Foundation, Ben Lieberman, said. “The problem today is much smaller than it was 10 or 20 years ago.”

“The risk of these chemicals in the air, I believe is overstated,” he said.

The study, which was released last month, found that 68 of every million New Yorkers are at additional risk of developing cancer because of the air here, compared to 66 in California and 41.5 nationwide.

The data showed an even higher risk in the five boroughs, where it’s estimated that 136 of every million people in Manhattan will develop cancer because of air pollution. In the Bronx, that number is 106, in Brooklyn it’s 95, in Queens it’s 92, and in Staten Island it’s 81.

Environmental experts said that while New York has been leading the way with strong environmental policy, they were not surprised at the high levels of toxins in the air.

The director of the Yale Center for Environmental Law and Policy, Daniel Esty, said part of the problem is that New York is downwind of industrial sites in New Jersey, Pennsylvania, and the Midwest.

“A lot of that mercury is coming out of coal-burning power plants in the Midwest,” he said. “Until the federal government gets serious about reducing those emissions there will be problems that New York can’t fix on its own.”

An associate professor at Columbia University’s Mailman School of Public Health, Patrick Kinney, said that the diesel fuel and exhaust from cars and trucks was also a major factor in contaminating the air.

“A lot of this is related to having a lot of people living in one area and emitting exhaust and diesel fuels from their tailpipes,” said Mr. Kinney, who specializes in environmental health science.

He pointed out that the country has made significant strides in making the air here cleaner, but said that given how much more experts know, it is reasonable to question whether more should be done. But he said there are other factors like smoking and diabetes that contribute to cancer, so it makes sense to debate how to expend resources to tackle toxic exposures.

The National-Scale Air Toxic Assessment, as the study is called, is a national, county-by-county snapshot that examines cancer, respiratory, and other health risks from air toxins. The data are from 1999, the most recent on record, and does not take into account emission risk reductions in the seven years since.

A spokesman for the EPA, John Millett, defended the agency on two fronts.

He said the cancer-risk methodology relied on “sound and widely accepted science” and that the EPA was doing plenty to enforce federal pollution regulations.

He said regulations that focus on coal-fired power plants, will cut interstate pollution by 60% to 70% by 2014 and that certain toxins will be slashed by even more.

The long list of toxins includes heavy metals such as lead; volatile chemicals such as benzene; combustion byproducts such as acrolein, and solvents including methylene chloride.

The assessment, according to the Associated Press, found the cleanest air in rural places like Wyoming, South Dakota, and Montana. Oregon, Washington, D.C., and New Jersey ranked behind California, which had the dirtiest air after New York.

Mr. Esty of Yale said Los Angeles, where risks of cancer are said to be twice the national average, as they are in New York, has a unique problem because of its geography.Whatever chemicals are released in the air become trapped in its bowl-like atmosphere.

A spokesman for the American Council on Science and Health, Jeff Stier, said that while exposure to high levels of toxic chemicals over a long period of time was something to worry about, it is not credible to suggest that the level of those toxins in the air is cancer-causing.

In an essay on the ACSH’s Web site, he writes that the EPA “declares chemical carcinogens … based solely on the creation of tumors in lab rodents through the administration of superhigh doses that are irrelevant to ordinary human exposure.”

Officials at the EPA said since the Clean Air Act was amended in 1990, it has issued 96 standards for different industrial air toxins and 15 for smaller sources like dry cleaners, smelters, and other facilities. The next assessment will be based on 2002 data.