Can air pollution cause asthma?
Smog and particles certainly trigger attacks in some people who already have asthma. For a long time it was thought that air pollution could not cause asthma to develop in previously healthy people. Some recent experiments challenge this belief. Scientists have shown that people exposed to ozone or nitrogen dioxide are more likely to react to allergens such as grass pollens and housedust mites than those who are not exposed. Thus a combination of air pollution and allergens could cause some cases of asthma. Across the board, other factors including allergens, colds, cigarette smoking and exposure to fumes and dust at work are probably more important.
