1. Primary Care and Population Health Research Program, Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada
2. Air Health Science Division, Health Canada, Ottawa, Ontario, Canada
3. Department of Epidemiology, Biostatistics and Occupational Health, Faculty of Medicine, McGill University, Montreal, Quebec, Canada
4. Department of Applied Immunization Research, Public Health Ontario, Toronto, Ontario, Canada
5. Divisions of Clinical Public Health and Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
6. Department of Family and Community Medicine, Faculty of Medicine, University of Toronto and University Health Network, Toronto, Ontario, Canada
7. Population Studies Division, Health Canada, Ottawa, Ontario, Canada
8. Department of Civil Engineering and Applied Mechanics, Faculty of Engineering, McGill University, Montreal, Quebec, Canada
9. Department of Environmental Health Sciences, Fielding School of Public Health, University of California, Los Angeles, Los Angeles, California
10. Department of Physics and Atmospheric Science, Faculty of Science, Dalhousie University, Halifax, Nova Scotia, Canada
11. Smithsonian Astrophysical Observatory, Harvard-Smithsonian Centre for Astrophysics, Cambridge, Massachusetts
12. Division of Occupational and Environmental Health, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
13. Department of Environmental and Occupational Health, Public Health Ontario, Toronto, Ontario, Canada