Exposure to motor vehicle traffic and allergic sensitization

We examined the association between the presence of an allergic sensitizati on and seasonal allergic diseases or symptoms and the exposure to road traf fic in Basel, Switzerland. Traffic counts at the domiciles of subjects rang ed from 24 to 32,504 cars per 24 hours, with a median of 1,624. To investig ate the relation of road traffic and allergies, we matched the data of the traffic inventory of Basel with those of the 820 participants of the SAPALD IA study (Swiss Study on Air Pollution and Lung Diseases in Adults), ages 1 8-60 years, who had completed a detailed respiratory health questionnaire a nd had undergone allergy testing (skin prick tests and serologic examinatio ns). We observed a positive association with a sensitization to pollen that was most pronounced among persons with a duration of residence of at least 10 years. The odds ratios (adjusted for educational level, smoking behavio r, number of siblings, age, sex, and family history of atopy) for cars, con trasting four exposure categories with the lowest quartile as referent cate gory, were 1.99 [95% confidence interval (CI) = 0.91-4.38], 2.47 (95% CI = 1.06-5.73), and 2.83 (95% CI = 1.26-6.31). These results suggest that livin g on busy roads is associated with a higher risk for a sensitization to pol len and could possibly he interpreted as an indication for interactions bet ween pollen and air pollutants. We did not, however, find a similar relatio n between motor vehicle traffic and hay fever or seasonal allergic symptoms , and we saw no trend that increasing traffic exposure was associated with a rise in sensitization rates to indoor allergens.