Elevated levels of air pollution increase the risk of asthma hospitalization associated with allergy to aeroallergens

Published Online: October 31, 2011

Outdoor aeroallergens and air pollution have each been associated with asthma morbidity and mortality. Several clinical laboratory studies demonstrated that the effect of allergen challenge on asthma was greater following prior exposure to an ambient air pollutant. The clinical significance of this synergistic effect in the general population is uncertain.

To investigate this, Cakmak et al compared the effect of ambient aeroallergens on hospitalization for asthma between higher and lower air pollution days in eleven large Canadian cities between April 1, 1994 to March 31, 2007. Potential effects of day-of-the week, temperature, barometric pressure, relative humidity were accounted for in the analysis.

As reported in The Journal of Allergy & Clinical Immunology (JACI), hospitalizations for asthma were more frequent on days of elevated pollen and fungal spores.  Relative to lower air pollution days, on higher air pollution days the risk of tree pollen-associated hospitalization was 44% greater and the risk of Basidiomycetes-associated hospitalization was 169% greater. These findings suggest that minimizing exposure to air pollution may reduce allergic exacerbations of asthma.


The Journal of Allergy and Clinical Immunology (JACI) is the official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

AAAAI - American Academy of Allergy Asthma & Immunology