Published Online: January 2012
Allergic diseases constitute one of the most prevalent childhood illnesses. Several population studies have reported increased risks of developing allergy in relation to ambient air pollution exposure. However, there are only few studies on specific sensitization following children over longer time periods, with detailed assessment of exposure to air pollution.
In a Research article in The Journal of Allergy & Clinical Immunology (JACI), Gruzieva et al. hypothesized that air pollution exposure may contribute to the development of allergic sensitization in children up to school age. They used data collected on more than 2,500 children followed from birth in the BAMSE project in Stockholm, Sweden. The children had blood tests for antibodies (IgE, immunoglobulin E) to common allergens at 4 and 8 years old, and extensive information was available from repeated questionnaires on lifestyle characteristics, allergies within the family, as well as on environmental exposures. The assessment of exposure to locally emitted air pollution from traffic was based on a methodology developed to estimate long-term source-specific exposure using dispersion models. Time-activity patterns were taken into account, considering the time children spent at home, daycare and/or school, to increase the precision in the exposure assessment.
A total of 614 children (24%) were sensitized to inhalant or food allergens at 4 years old and 765 children (35%) at 8 years old. The results showed that exposure during the first year of life was associated with an elevated risk of sensitization to pollen at 4 years old and to food allergens at 8 years old, and the latter was particularly strong in subjects without earlier sensitization. No associations between air pollution exposure after the first year of life and sensitization were seen. Among possible explanations of the observed results the authors discuss the infancy period as a potentially important time window of susceptibility to various risk factors, including air pollution, as well as a higher precision of the exposure assessment during that period. Cross-reactions between pollen and certain food allergens, such as between birch pollen and peanut allergens, were suggested to contribute to the observed change in allergic pattern with age.
The authors’ findings indicate that air pollution exposure during infancy may contribute to the development of sensitization to certain inhalant and food allergens later in childhood.
The Journal of Allergy and Clinical Immunology (JACI) is the official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.