From Kathleen MacNaughton, R.N.,
Your Guide to Asthma.
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About.com Health's Disease and Condition content is reviewed by Sanja Jelic, MD

Air pollution is yet another asthma trigger. Air pollutants such as smoke, ground level ozone, vehicle exhaust, and others are in the class of asthma triggers known as irritants.

An irritant is so named because it irritates already inflamed asthma airways. Irritants don't produce the same type of immune response that an allergen does. But they can make existing asthma symptoms worse.

Examples of Air Pollutants

Air pollutants are known as one of the main risk factors for developing asthma in urban environments. Changes in our environment over the past few decades have resulted in higher levels of air pollutants all the time in our atmosphere. This is one possible explanation for the increased rates of asthma in developed countries.

Common air pollutants include:

• Tobacco smoke
• Wood smoke from campfires and woodstoves
• Exhaust, soot and fumes from cars and other road vehicles
• Ground level ozone
• Other chemical fumes in the air