Air Toxics Lifetime Cancer Risk High for U.S. City Dwellers

WASHINGTON, DC, February 22, 2006 (ENS) - Residents of most U.S. cities have an air toxics lifetime cancer risk greater than 25 in a million - a rate above the risk of people in the general population, according to the second National-Scale Air Toxics Assessment, released today by the U.S. Environmental Protection Agency (EPA).

Lifetime cancer risk in transportation corridors and some other locations is greater than 50 in a million, the assessment shows.

The National-Scale Air Toxics Assessment (NATA) is a screening tool that estimates cancer and other health risks from exposure to emissions of air toxics in 1999.

The assessment estimates that in most of the United States people have a lifetime cancer risk from air toxics between one and 25 in a million. This means that out of one million people, between one and 25 people have increased likelihood of developing cancer as a result of breathing air toxics from outdoor sources, if they were exposed to 1999 levels over the course of a lifetime of 70 years.

By contrast, one out of every three Americans - 330,000 in a million - will develop cancer during a lifetime, when all causes, including exposure to air toxics, are taken into account, the assessment shows.

Air pollution in Houston, Texas, 2000. (Photo courtesy UT)

The assessment provides a snapshot of air quality and the risks that would result if 1999 emissions levels remained unchanged. It does not reflect reductions in air toxics that have occurred since 1999 or those anticipated to occur in the future.

The EPA develops NATA in cooperation with state and local environmental agencies. The results of the assessment are intended to help the EPA, and state and local air quality regulators identify pollutants and sources of greatest concern and set priorities for addressing that pollution.

The assessment also will help identify areas where EPA needs to collect additional information to improve the understanding of risks from air toxics exposure.

NATA covers 177 of the Clean Air Act's list of 187 air toxics plus diesel particulate matter.

This assessment includes heavy metals, such as lead; volatile chemicals, such as benzene; combustion byproducts, such as acrolein; and solvents, including perchloroethylene and methylene chloride.

For 133 of these air toxics - those with health data based on chronic exposure - the assessment includes estimates of cancer or non-cancer health effects including non-cancer health effects for diesel particulate matter.

The nonprofit organization Clean Air Task Force says diesel exhaust is the most hazardous air toxic to which Americans are exposed.

Using the EPA's NATA diesel exhaust concentrations combined with a cancer risk factor developed by the California Air Resources Board, the Clean Air Task Force quantified national risk from exposure to diesel exhaust.

CATF found the nationwide average lifetime cancer risk posed by diesel exhaust to be 365 times greater than EPA's "acceptable" level of one cancer per million people.

The lifetime cancer risk of diesel exhaust was more than eight times higher than the risk of the 133 air toxics tracked by EPA combined.

Toxics contained in diesel exhaust pose a high lifetime risk of cancer. (Photo credit unknown)

"The single most important step in reducing cancer risk from air toxics is to reduce diesel exhaust, and today's retrofit technologies can reduce particulate matter exhaust from many diesel engines by up to 90 percent. Congress should act this year to fully fund the 'Diesel Emissions Reductions Act' so that we can begin now to clean up America's dirty diesels," urged Hill.

The EPA says that from a national perspective, benzene is the most significant air toxic for which cancer risk could be estimated, contributing 25 percent of the average individual cancer risk identified in this assessment.

The key sources for benzene are onroad (49 percent) and nonroad mobile sources (19 percent), and open burning, prescribed fires and wildfires (14 percent). Residential heating from wood combustion accounts for approximately six percent of the total benzene emissions.

EPA projects that onroad and nonroad mobile source benzene emissions will decrease by about 60 percent between 1999 and 2020, as a result of motor vehicle standards, fuel controls, standards for nonroad engines and equipment, and motor vehicle inspection and maintenance programs. Most of these programs reduce benzene simultaneously with other volatile organic compounds.

The second National-Scale Air Toxics Assessment expands on the EPA's first national-scale assessment with a more complete emissions inventory and the latest health effects information. The first assessment, based on 1996 data, was released in 2002.

The methods used for the assessments were peer-reviewed and endorsed by EPA's Science Advisory Board in 2001.

For a NATA fact sheet visit: http://www.epa.gov/ttn/atw/nata1999/natafinalfact.asp