1. Public Health Ontario, Toronto, Ontario, Canada
2. Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
3. Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada
4. Population Studies Division, Health Canada, Ottawa, Ontario, Canada
5. Department of Family and Community Medicine, University of Toronto, Toronto, Ontario, Canada
6. Department of Health Sciences, Carleton University, Ottawa, Ontario, Canada
7. Department of Medicine, McGill University, Montreal, Quebec, Canada
8. Division of Clinical Epidemiology, McGill University Health Centre, Montreal, Quebec, Canada
9. Division of Cardiovascular Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
10. Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
11. Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, Berkeley, California, USA
12. Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA
13. Air Quality Research Division, Environment Canada, Toronto, Ontario, Canada
14. Division of Cardiology, Schulich Heart Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada