Pollution Portrait: The Fourth National-Scale Air Toxics Assessment

Abstract

Taken at face value, the results of the fourth edition of the U.S. Environmental Protection Agency’s (EPA) National-Scale Air Toxics Assessment (NATA), released 11 March 2011 are sobering.1 Every person in the country is at 10 times or greater risk for getting cancer from outdoor air pollutants than the agency’s general goal of 1 in 1 million,2 the average risk is 50 times greater than the goal, and about 5% of the population is at more than 100 times the risk. Almost one-quarter of the population is at increased risk for certain noncancer health effects, primarily respiratory effects. A closer look reveals the risks might be substantially lower, however. These estimates are based on 2005 emissions, and the EPA says numerous regulations approved and implemented since then have significantly reduced some emissions. The agency also notes that the total cancer toll exacted by the toxics tracked in NATA is very small compared with the risk posed by other known factors. Those combine to create a total risk of 336,000 in 1 million (based on the number of actual cancer cases), with the bulk of the risk widely attributed to lifestyle factors such as tobacco use, diet, lack of exercise, certain types of infections, and radiation.3 For additional context, the EPA says radon, which isn’t among the Clean Air Act toxics assessed for NATA, poses a cancer risk of about 2,000 in 1 million. But Mary Sullivan Douglas, a senior staff associate with the National Association of Clean Air Agencies, cautions that NATA remains incomplete. “There’s a lot that’s not known about the emissions and effects of toxic air pollutants,” she says. “Things could look much worse if we had all the data. We think hazardous air pollutants are very dangerous and need to be addressed, especially for some of the small sources that together form a large part of the NATA inventory.”