Air Pollution and Allergies: A Connection?
"air pollutants act more as irritants that can aggravate allergies and asthma, rather than as true promoters of allergy or asthma."

medicinenet.com

Smog: Not an Allergen,but an Irritant
"Air pollution from high-ozone smog can make existing asthma symptoms worse as well as triggering the onset of the condition in the first place"

webmd.com
What Do I Need To Know About Air Pollution?
"Research shows that air pollution can worsen asthma symptoms. A study of young campers with moderate to severe asthma showed they were 40 percent more likely to have acute asthma episodes on high pollution summer days that on days with average pollution levels."

aafa.org