[1] Simon Fraser Univ, Fac Hlth Sci, Burnaby, BC V5A 1S6, Canada
[2] Univ Toronto, Inst Med Sci, Toronto, ON M5S 3H7, Canada
[3] Queens Univ, Dept Biomed & Mol Sci, Kingston, ON K7L 3N6, Canada
[4] Queens Univ, Dept Med, Div Allergy & Immunol, Kingston, ON K7L 3N6, Canada
[5] Kingston Gen Hosp, Allergy Res Unit, Kingston, ON K7L 2V7, Canada
[6] Univ Toronto, Dalla Lana Sch Publ Hlth, Toronto, ON M3H 5T4, Canada
[7] Hlth Canada, Air Qual Hlth Index, Ottawa, ON K1A 0K9, Canada
[8] Environm & Climate Change Canada, Hlth & Air Qual Serv, Ottawa, ON K1A 0H3, Canada
[9] BC Ctr Dis Control, Environm Hlth Serv, Vancouver, BC V5Z 4R4, Canada
[10] Univ British Columbia, Sch Populat & Publ Hlth, Vancouver, BC V6T 1Z3, Canada
[11] Hlth Canada, Air Hlth Sci Div, Ottawa, ON K1A 0K9, Canada
[12] Univ Ottawa, Sch Epidemiol & Publ Hlth, Ottawa, ON K1G 5Z3, Canada