1. a U.S. Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory , Research Triangle Park , NC , USA
2. b Envair/Aerochem , Placitas , NM , USA
3. c Envair , Pasco , WA , USA
4. d Aerodyne Research, Inc. , Billerica , MA , USA
5. e MACTEC Federal Programs, Inc. , Durham , NC , USA
6. f National Oceanic and Atmospheric Administration, Earth System Research Laboratory , Chemical Sciences Division , Boulder , CO , USA
7. g North Carolina State University, Department of Civil, Construction, and Environmental Engineering , Raleigh , NC , USA
8. h Instituto Nacional de Ecología, Dirección General de Investigación Sobre la Contaminación Urbana, Regional y Global , Mexico City , Mexico
9. i Environment Canada , Criteria Air Contaminants , Gatineau , Quebec , Canada
10. j NARSTO, Columbia Research and Education Associates , Pasco , WA , USA
11. k U.S. Environmental Protection Agency , Office of Research and Development, National Exposure Research Laboratory , Research Triangle Park , NC , USA