Atmospheric pollution and allergic asthma

The prevalence of asthma and allergic diseases is increasing in all industr ialized countries. Genetic and environmental factors, and their interaction s, are responsible for this increasing prevalence. A certain number of gene s are currently screened to determine their suspected role in the immunogen esis of asthma, but in themselves, they cannot explain the increasing preva lence of asthma observed over the last 20 years. Environmental factors appe ar to be the most plausible explanation. Among these factors, air pollution and changing lifestyle as well as lower resistance due to fewer infectious diseases during childhood may be the most important factors. Experimental studies have shown that some pollutants such as ozone or diese l exhaust particles can interact with allergens, amplifying allergic reacti ons. Epidemiological studies have provided contradictory results. Acutely high c oncentrations of different pollutants can induce transient respiratory symp toms in asthmatic subjects but the long-term effects of air pollution on th e genesis of asthma are still quite unclear.