Assessment of Quantitative Mobile Source Air Toxics in Environmental Documents

Mobile source air toxics (MSATs) are substances that are emitted from motor vehicle and other mobile source exhaust that have been identified as “hazardous air pollutants” with potential human health risks. Numerous MSATs have been identified with varying degrees of scientific knowledge and uncertainty over their health impacts. There currently are no regulations specifying either maximum levels of MSATs in vehicle exhaust, or maximum MSAT ambient concentrations. MSATs continue to be raised as concerns, however, in environmental impact studies for transportation projects. Responding to such concerns, the Federal Highway Administration (FHWA) has provided guidance on addressing MSATs in highway project environmental documentation prepared pursuant to the National Environmental Policy Act (NEPA). The U.S. Environmental Protection Agency’s (EPA's) MOVES emission factor model expands the number of MSATs that can be modeled, encompassing those that have been identified as being most significant. The Moving Ahead for Progress in the 21st Century Act (MAP-21) also provides for a study of mobile source air pollutants and associated health effects. This research project is intended to expand the base of knowledge regarding the MSAT impacts of transportation projects, and in particular, to provide additional information to help practitioners understand the degree of MSAT analysis that may be most warranted for transportation projects.

  • Record URL:
  • Summary URL:
  • Supplemental Notes:
    • This study was requested by the American Association of State Highway and Transportation Officials (AASHTO), and conducted as part of the National Cooperative Highway Research Program (NCHRP) Project 25-25. Project 25-25 is intended to fund quick response studies on behalf of the AASHTO Standing Committee on the Environment.
  • Corporate Authors:

    Cambridge Systematics, Incorporated

    100 Cambridge Park Drive, Suite 400
    Cambridge, MA  United States  02140

    Cambridge Environmental Incorporated

    Cambrige, MA  United States 

    Sonoma Technology, Incorporated

    1360 Redwood Way, Suite C
    Petaluma, CA  United States  94954-1169
  • Authors:
    • Porter, Christopher
    • Kear, Tom
    • Kall, David
    • Zemba, Stephen
    • Eisinger, Douglas S
  • Publication Date: 2012-8


  • English

Media Info

  • Media Type: Digital/other
  • Features: Appendices; Figures; References; Tables;
  • Pagination: 109p

Subject/Index Terms

Filing Info

  • Accession Number: 01497104
  • Record Type: Publication
  • Report/Paper Numbers: NCHRP 25-25 Task 70
  • Files: TRIS
  • Created Date: Oct 17 2013 3:31PM