|Abstract:||Air toxics is an emerging area that receives more and more attention—from transportation/environmental agencies, academic researchers, and
the public—because of potential health issues and uncertainties with modeling and the science behind MSAT. Currently 188 air toxics are
identified in the Clean Air Act as hazardous air pollutants. Among them, 21 are labeled as mobile source air toxics (MSAT) by the U.S.
Environmental Protection Agency (EPA). In particular, 6 of the 21 MSATs are priority MSATs. They are benzene, formaldehyde,
acetaldehyde, diesel particulate matter/diesel exhaust organic gases, acrolein, and 1,3-butadiene. There are no regulatory concentration
standards set up for the six MSATs. In response to the need for federal guidance in documenting MSAT impacts by state DOTs, the Federal
Highway Administration (FHWA) issued Interim Guidance on February 3, 2006 to advise state Departments of Transportation (DOT) on when
and how to analyze MSATs in the National Environmental Policy Act (NEPA) process for highway projects. As the science progresses, FHWA
will update the MSAT guidance.
Given many uncertainties with the new guidance that is still evolving, on October 5-6, 2006 the Mobile Source Air Toxics Peer Exchange
Meeting was successfully held at Allerton Park, Monticello, Illinois, facilitated by University of Illinois at Chicago (UIC). Twenty-one
participants from the six state DOTs (Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin), FHWA, US EPA Region 5 Office, Illinois
EPA and UIC attended the meeting. The meeting covered both the technical and practical issues/uncertainties emerging from the new MSAT
guidance and exchanged ideas and experiences in documenting MSATs in the NEPA documents. These proceedings summarize the topics and
issues covered in the presentations and roundtable discussion at the meeting.