1. Department of Environmental and Occupational Health, Public Health Ontario, Toronto, ON, Canada
2. Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada
3. Population Studies Division, Health Canada, Ottawa, ON, Canada
4. Primary Care & Population Health Research Program, Institute for Clinical Evaluative Sciences, Toronto, ON, Canada
5. Department of Family and Community Medicine, University of Toronto, Toronto, ON, Canada
6. Toronto Western Hospital Family Health Team, University Health Network, Toronto, ON, Canada
7. Department of Applied Immunization Research, Public Health Ontario, Toronto, ON, Canada
8. College of Public Health and Human Studies, Oregon State University, Corvallis, OR, USA
9. Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada
10. Air Quality Research Division, Environment Canada, Toronto, ON, Canada
11. Department of Medicine, McGill University, Montreal, QC, Canada
12. Division of Clinical Epidemiology, McGill University Health Centre, Montreal, QC, Canada
13. Department of Health Sciences, Carleton University, Ottawa, ON, Canada
14. Smithsonian Astrophysical Observatory, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA
15. Department of Medicine, University of Toronto, Toronto, ON, Canada
16. Division of Neurology, Sunnybrook Health Sciences Centre, Toronto, ON, Canada