Methods: The study population was derived from a prospective 2-year follow-up survey of Children’s Health and Environmental Research (CHEER). 5,443 children from 16 elementary schools in seven cities were enrolled in the CHEER. Parents of the participants were asked to respond to an International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire to evaluate the presence of allergic diseases and risk factors. IL-13 (rs20541) genotypes were determined by TaqMan assay. PM10 exposure was estimated by the kriging method.
Results: The parental history of asthma (adjusted odds ratio [aOR], 3.73; 95% confidence interval [CI], 2.63-5.31), and bronchiolitis history within the first 2 years of life (aOR, 4.77; 95% CI, 3.66-6.21) were independent risk factors for physician-diagnosed asthma. But high PM10 exposure for recent 5 years was not significant. When past episodes of bronchiolitis and high exposure to PM10 were combined, the prevalence of asthma was significantly increased (aOR, 5.28; 95% CI, 3.61-7.72; P for interaction=0.007), also increased risk of asthma especially in children with GA+AA type of IL-13 polymorphism (aOR, 4.13; 95% CI, 1.89-9.07; P for interaction=0.101). New asthma diagnosis during follow-up period increased with higher PM10 exposure and bronchiolitis history (aOR, 3.18; 95% CI, 1.49-6.80, Pfor interaction = 0.107).
Conclusions: PM10 exposure and bronchiolitis history synergistically increased asthma risk and new development of asthma in children, particularly if they had the IL-13 (rs20541) polymorphism. These findings suggest that PM10exposure and bronchiolitis in early life contribute to the development of asthma, especially in susceptible children.
Keywords: Bronchiolitis; Particulate matter; Asthma; Interleukin-13; Polymorphism