Infants who live near roads with lots of stop-and-go bus and truck traffic are significantly more likely to develop wheezing than those who live near steady traffic or those who aren't exposed to much traffic, Patrick Ryan and his associates reported.
The association may be related to increased amounts of diesel exhaust particles (DEP) shed when the vehicles accelerate from a stop, said Mr. Ryan, of the University of Cincinnati, and his colleagues. Other studies have shown that acceleration from stop increases this particulate matter.
The researchers examined wheezing without cold over 1 year in 622 infants (median age 7.5 months). The infants were part of the Cincinnati Childhood Allergy and Air Pollution Study; all had at least one atopic parent (J. All. Clin. Immunol. 2005;116:279–84).
Most (374) of the infants were unexposed to traffic; 176 lived near moving bus and truck traffic, and 99 lived near stop-and-go traffic. Infants exposed to stop-and-go traffic were more likely to be black, have out-of-home care, and have a father with asthma, and they were less likely to have been breast-fed. The researchers adjusted for these variables.
Of the 622 infants, 8% (50) reported wheezing without a cold. The prevalence of wheezing in the unexposed infants was 5.8%. The prevalence was 7.4% in infants exposed to moving traffic, and 17.2% in infants exposed to stop-and-go traffic.
The prevalence of wheezing was three times higher (19%) in infants who lived less than 50 meters from moving traffic compared with the unexposed group. The prevalence of wheezing in those who lived 200–300 meters from moving traffic was 12%.