3 June 2002

The US Environmental Protection Agency published an updated analysis of health risk estimates for 33 toxic air pollutants nationwide. Toxic air pollutants are substances classified by the Clean Air Act (CAA) as known to or suspected of causing cancer or other serious health problems. The published analysis covered a subset of 32 air toxics on the CAA list of 188 air toxics plus diesel particulate matter (PM). The assessment was based on 1996 emission inventories.

EPA concluded that more than 200 million people in the US live in areas where the combined upper bound lifetime cancer risk from the studied compounds exceeded 10 in 1 million risk, while 20 million people live in areas where the risks are 100 additional lifetime cancers for every 1 million people. The EPA looked for pollutants whose cancer risks were above an arbitrary level of 1 in a million. The determination of what is an acceptable or unacceptable risk was not a part of the study.

Commenting on the study, the EPA said that the risks of cancer from toxic chemical exposure are “very, very small” when compared with overall cancer risks from all sources. The real cancer risks are likely smaller than suggested by the study and “have been reduced significantly” since 1996.

Cancer risks were estimated for 32 air toxics, 29 of which were classified as carcinogens. Example substances identified as posing highest cancer risks include benzene, chromium, arsenic, coke oven emissions, 1,3-butadiene and polycyclic organic matter (POM).

The EPA said that diesel particulate emissions also had a potential for lung cancer risk. However, the cancer risk from diesel PM was not calculated. According to the EPA, existing scientific data are not sufficient to develop a numerical estimate of carcinogenic potency for diesel particulate matter.

The complete results of the technical analysis, as well as background and supporting information are available at http://www.epa.gov/ttn/atw/nata/.

Source: US EPA