Household mold exposure in association with childhood asthma and allergic rhinitis in a northwestern city and a southern city of China.

Background: The prevalence of asthma and allergic diseases has increased rapidly in Chinese cities over the past decades. Few studies have examined the potential role of household mold in asthma and allergies in Chinese cities. Methods: A cross-sectional survey in 4,691 school-age children was performed in Lanzhou and Wuhan. The two cities represent distinct climate conditions, as Lanzhou, located in northwestern China, has dry and cold winter and relatively cool summer whereas Wuhan, located in central-southern China, has hot and humid summer and mild winter temperatures. Two schools were randomly selected from a suburb and an urban area of each city, respectively. Data were collected using a modified Chinese version of the American Thoracic Society (ATS) standard respiratory health questionnaire for children, regarding asthma, substance allergy, allergic rhinitis, presence of mold in residence, and household characteristics. Logistic regression models were applied to identify the odds ratios of childhood asthma and allergies with regard to mold. Results: The prevalence rates of asthma, substance allergy, allergic rhinitis, and mold, were all higher in Wuhan than in Lanzhou. We observed significant associations of household mold with increased prevalence for both asthma [odds ratio (OR) =2.399, 95% confidence interval (95% CI): 1.309-4.398], substance allergy (OR =1.729, 95% CI: 1.282-2.332) and allergic rhinitis (OR =1.969, 95% CI: 1.491-2.600), with spatial heterogeneity across urban versus suburban schools. The mold effect was modified by age group and breast-feeding status. Conclusions: Across two climatically distinct cities, household mold exposure was significantly associated with an increased risk for asthma and allergies. Younger children and children from the suburbs were more likely to be affected by mold. Whether breastfeeding enhanced or weakened the mold effects were inconsistent across the cities and across the health outcomes.