1. Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, Berkeley, California, USA;
2. Department of Family and Community Medicine, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada;
3. Meteorological Services, Environment Canada, Toronto, Ontario, Canada;
4. School of Geography and Earth Science, McMaster University, Hamilton, Ontario, Canada;
5. Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada;
6. Program in Occupational Health & Environmental Medicine, McMaster University, Hamilton, Ontario, Canada;
7. Division of Respirology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada;
8. Division of Respirology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada