Traffic air pollution raises risk of atopic eczema

Living near a busy road is an independent risk factor for atopic eczema in girls, it was reported at the 10th Congress of the European Academy of Dermatology and Venereology.

The culprit is likely traffic-related air pollution. The air near major roads contains high concentrations of small-diameter diesel exhaust particles. NO2, and volatile organic compounds such as benzene and tolvene. All have been linked to increase allergic rhinitis, hay fever, wheezing, and sensitization to common antigens. These pollutants also are associated with increased rates of atopic eczema, at least in girls, through a mechanism unrelated to the pollutants’ propensity to enhance allergic sensitization. The gender difference points to a possible genetic environmental interaction at work. One doctor reported on 4,000 randomly selected German six-year-old who participated in one of four cross-sectional studies conducted in 1991, 1994, 1997, and 2000. All had a thorough skin exam and skin-prick testing for grass pollen, birch pollen, and hose dust mite. A total of 11 percent of girls and eight percent of boys were diagnosed by dermatologists as having atopic eczema. In contrast, 15 percent of girls and 21 percent of boys were sensitized to birch pollen, grass pollen, or house dust mites.

Half of the boys with atopic eczema were sensitized to one or more of the test antigens, compared with 20 percent of girls with atopic eczema. She and her co-workers then looked at the impact of traffic emissions. Because airborne traffic pollutants are found in much higher concentrations within 50 m of a street than further away, investigators separated the children into those who lived within that distance of a busy street and those who didn’t. The investigators did a regression analysis adjusting for parental education, dampness of the dwelling, and whether or not the child shared a bedroom.

The six-year old girls without allergic sensitization, as evidenced by negative skin-prick tests, had a 1.8-fold higher risk of atopic eczema if they lived within 50 m of a busy street than if they lived further off the road. The risk was identical in girls who had one or more positive skin prick tests and lived within 50 m of a major road.