Air pollution and allergy.

Epidemiological studies have found a recent increase in the prevalence of allergic diseases, especially in industrialized countries. A change in environmental factors may be considered as one of the causes of this increase. It has been reported that the prevalence of allergic diseases is higher in polluted areas than in unpolluted ones. Therefore, we focused on the effect of one air pollutant, suspended particulate matter (SPM), on allergic responses. We showed that SPM had an enhancing effect on the IgE antibody production in mice. In Japan, the number of cars with diesel engines has increased rapidly, and it has been calculated that 35-80% of SPM in large cities consists of diesel exhaust particulates (DEP). We demonstrated that DEP had an adjuvant effect on the IgE antibody production in mice when administered intraperitoneally or intranasally. In humans, it has been shown that nasal challenge with DEP enhanced total IgE and specific IgE production in nasal lavages. Furthermore, it has been demonstrated that DEP had an enhancing effect on Th2-type cytokine synthesis in both mice and humans. It cannot be excluded that DEP may be related to the increase in prevalence of allergic diseases through the effect on the IgE antibody production and Th2-cytokine synthesis.