Air pollution and atopy

One possible explanation to account for the current increase in the prevalence of respiratory allergic diseases concerns the facilitating influence of air pollutants. Pollen grains collected in polluted areas could have a higher allergenic content. In vitro exposure of pollen grains to current levels of air polluants can induce a change in protein and allergenic content. Animal experiments demonstrate that pre-exposure to high levels of SO2, NOx and diesel-exhaust particulates enhances specific responses to inhaled or intra peritoneally administered pollutants. Few studies have been performed in man. They also suggest an increased response to allergenic challenge after pre-exposure to a moderate concentration of SO2, NO2 and Ozone. Epidemiological surveys comparing the prevalence of atopy in urban vs rural settings usually demonstrate a higher prevalence in the former. However, no survey can attribute this difference to urban pollutants. It is more probably due to overall differences in daily living conditions. Comparative studies performed in groups of schoolchildren living in former Fast and West Germany show a two-fold higher prevalence of atopy and atopic diseases such as hay fever and asthma in former West Germany. It is hypothesized that the western way of life, including a lower rate of recurrent early childhood infections and a higher allergenic exposure could explain these differences.