Overview: Pollutants and Programs
Mobile Source Air Toxics
- Basic Information
- Health Effects & Risk
- Monitoring & Exposure
- Related EPA Programs
What Are Mobile Source Air Toxics?
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Mobile source air toxics are compounds emitted from highway vehicles and nonroad equipment which are known or suspected to cause cancer or other serious health and environmental effects. Mobile sources are responsible for direct emissions of air toxics and contribute to precursor emissions which react to form secondary pollutants. Examples of mobile source air toxics include benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein, polycyclic organic matter (POM), naphthalene, and diesel particulate matter.
EPA has conducted an extensive review of the literature to produce a list of the compounds identified in the exhaust or evaporative emissions from onroad and nonroad equipment, using baseline as well as alternative fuels (e.g., ethanol, biodiesel, compressed natural gas). This list, the Master List of Compounds Emitted by Mobile Sources, and the documentation for the development of the list are available here:
- Master List of Compounds Emitted by Mobile Sources (16 pp, EPA420-B-06-002)
- Final Report Master List prepared by ENVIRON International Corporation (PDF) (58 pp, 717K, EPA420-R-06-005, February 2006)
Cancer and noncancer health effects can result from exposures to air toxics. EPA’s Integrated Risk Information System (IRIS) features a database of human health effects that may result from exposure to various substances found in the environment. See Health Effects and Risk page for more information on the health effects of mobile source air toxics.
What is EPA Doing About Mobile Source Air Toxics?
In February 2007, EPA finalized a rule to reduce hazardous air pollutants from mobile sources (Control of Hazardous Air Pollutants from Mobile Sources, February 26, 2007). The rule will limit the benzene content of gasoline and reduce toxic emissions from passenger vehicles and gas cans. EPA estimates that in 2030 this rule would reduce total emissions of mobile source air toxics by 330,000 tons and VOC emissions (precursors to ozone and PM2.5) by over 1 million tons. See Regulations page for more information on this program and other EPA regulations specifically targeting mobile source air toxics.
EPA has adopted many mobile source emission control programs that, in addition to controlling pollutants such as hydrocarbons, particulate matter, and nitrogen oxides, will also result in large air toxic reductions. Examples of these control programs include the following:
- Heavy-duty Onboard Diagnostic Rule (PDF) (74 FR 8310, 119 pp, 825K, published February 24, 2009)
- Small SI and Marine SI Engine Rule (PDF) (73 FR 59034, 347 pp, 3.69MB, October 8, 2008)
- Locomotive and Commercial Marine Rule (PDF) (73 FR 25098, 255 pp, 2.08MB, published May 6, 2008)
- Clean Air Nonroad Diesel Rule (PDF) (69 FR 38957, 316 pp, 1,87K, published June 29, 2004)
- Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements (PDF) (66 FR 5002, 192pp, 1.71MB, published January 18, 2001)
- Tier 2 Motor Vehicle Emissions Standards and Gasoline Sulfur Control Requirements (PDF) (65 FR 6698, 173 pp, 1.14MB, published February 10, 2000)
- Tier 3 Final Rulemaking (PDF) (1,069 pp, 7.0MB, pre-publication, signed March 3, 2014)
EPA has developed additional diesel-related programs to reduce diesel particulate matter under the National Clean Diesel Campaign, which encompasses a variety of programs to reduce diesel emissions.
Further details on EPA’s efforts to assess air toxics health effects and risk, emissions, and air quality and exposure, as well as related EPA programs can be found by clicking the relevant tabs above.
What You Can Do
EPA has developed a variety of information materials on how you can help reduce emissions and exposure to air pollutants from mobile sources.