June 25, 2009 -- Thirty-six out of 1 million U.S. residents will develop cancer due to breathing toxic air pollution, according to estimates by the Environmental Protection Agency (EPA).
The estimate is based on 2002 levels of air pollution from gasoline cars, factories, and other sources. It represents a drop from a 2006 estimate, when the EPA predicted an average of 42 cancer cases per million people based on 1999 air pollution levels.
The EPA stressed that its figures, based on 180 pollutants, represents a national average. Many people face little cancer risk due to air pollution, though more than 2 million people live in areas where the added cancer risk exceeds 100 in 1 million.
Most of those people are in large cities like Los Angeles, New York, Chicago, and Pittsburgh.
Large cities appear to carry greater cancer risk because of a higher volume of cars, trucks, construction equipment, gas stations, and in some cases, dry cleaners, says David Guinnup, PhD, the lead EPA scientist for the study, known as the National-Scale Air Toxics Assessment.
But there are also many rural industrial areas where residents have an elevated risk, according to the report.
Cancer risks for an area in northern Mississippi, were estimated to exceed 100 per 1 million, and estimates were also high in central southern Kentucky.
"Usually these are industrial facilities focused on chemical production or processes involving chemicals," Guinnup tells WebMD. "We're going to go into these areas and follow up and see if there's something we can do about it."
Meanwhile, rural states like Wyoming, Montana, Nebraska, and the Dakotas carry the lowest amount of increased cancer risk due to pollution, according to the EPA.
The EPA's estimates assume people are exposed to pollutants continuously over their lifetime. That means it doesn't account for rises or drops in risk as people move around the country. It also doesn't account for cancer risk from diesel engines, which EPA considers one of the riskiest pollutants.
Air pollution is only one source of cancer risk. Controllable factors like smoking contribute much more risk. The EPA says improved fuel standards and fuel efficiency are causing drops in levels of most carcinogenic environmental pollutants.