Air Toxics
Americans Have Increased Risk of Developing Cancer Due to Exposure to Toxics, EPA Says
The entire U.S. population lives in areas where exposure to airborne hazardous pollutants puts them at an elevated risk of developing cancer, according to an Environmental Protection Agency analysis released March 11.
According to EPA's 2005 National-Scale Air Toxics Assessment, all people in the United States have an increased cancer risk of greater than 10 in one million due to exposure to hazardous air pollutants—also known as air toxics.
This level of risk was essentially unchanged from the cancer risk estimate that was included in the last version of the assessment released by EPA in 2009 (40 ER 1485, 6/26/09).
However, hazardous air pollutant emissions from industrial and mobile sources dropped 42 percent between 1990 and 2005 EPA said.
EPA generally deems a lifetime cancer risk greater than one in 1 million to be unacceptable.
The 2005 National-Scale Air Toxics Assessment evaluated the risk of developing cancer as a result of exposure to individual hazardous air pollutants over a lifetime for 177 of the 187 air toxics regulated under the Clean Air Act, including benzene and polyaromatic hydrocarbons, using inventory data from 2005, the most complete year available.
The assessment is the fourth issued by the agency since 1996. The next assessment will be based on 2008 emissions and will be released in 2012, it said.
Nearly 14 Million Have 100:1 Million Risk
Less than 5 percent of the population, 13.8 million people, live in areas where they have cancer risk of greater than 100 in 1 million from exposure to air toxics, EPA said. In its previous assessment, the agency estimated that 2 million Americans lived in areas where there was a cancer risk exceeding 100 in 1 million.
However, because of improvements to EPA methodology, results from the latest assessment cannot be directly compared to results from previous years, EPA said. In addition, some of the data used are provided by states and can vary in detail from state to state, EPA said. The assessment also is subject to limitations due to gaps in data or risk assessment science, it said.
EPA said the latest assessment does not include cancer-causing dioxins; the agency is reassessing the health effects of many pollutants considered in the assessment.
EPA said the average cancer risk posed by hazardous air pollutants was 50 in 1 million in 2005, resulting in about one in 20,000 people having an increased likelihood of developing cancer as a result of breathing hazardous air pollutants from outdoor sources.
The principal non-cancer hazard from hazardous air pollutants was respiratory effects from exposure to acrolein, a chemical used in the plastics and chemical industry. EPA considers the existing data on acrolein inadequate for assessing human carcinogenic potential.
Based on 2005 Inventory
The latest assessment classified pollutants as national or regional cancer risk drivers based on the level of risk a pollutant creates and the number of people exposed.
Formaldehyde was the only national cancer-risk driver, while benzene, polyaromatic hydrocarbons, and naphthalene were regional cancer risk drivers.
Acrolein was the only non-cancer hazard driver.
The assessment did not address the potential cancer risk from particulate matter emissions from diesel engines because no risk estimate is available. According to an EPA fact sheet said, though, “EPA has concluded that diesel exhaust is among the substances that may pose the greatest risk to the US population.”
However, the Clean Air Task Force used a cancer risk factor adopted by the California Air Resources Board and found that the cancer risk posed by diesel exhaust is three times greater than the risk of all of the air toxics tracked by EPA combined. According to the task force, the nationwide average lifetime cancer risk posed by diesel exhaust is 159 times greater than the 1-in-1 million risk of developing cancer that EPA deems an acceptable level.
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