1. U.S. Environmental Protection Agency, National Exposure Research Laboratory,
MD-305-01, Research Triangle Park, North Carolina 27711, United States
2. U.S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, MD-C504, Research Triangle Park, North Carolina 27711,
United States
3. U.S. Environmental Protection Agency, National Center for Environmental
Economics, MC 1809T, Washington, DC 20460, United States
4. RTI International, P.O. Box 12194, Research Triangle Park, North Carolina 27709, United
States