Exposure to ambient fine particulate matter components during pregnancy and early childhood and its association with asthma, allergies, and sensitization in school-age children.

Background: Exposure to fine particulate matter (PM_2.5) has been associated with allergic diseases, including asthma. However, information about the effects of specific PM_2.5 components is limited. This study aimed to investigate the relationship of exposure to chemical components of PM_2.5 during pregnancy and early childhood with the development of asthma, allergies, and sensitization in school-age children.

Methods: This study included 2,408 children in the second grade of elementary school. Questionnaire surveys of respiratory/allergic symptoms and measurements of serum total IgE and specific IgE levels to house dust mite (HDM) and animal proteins were conducted. Exposures to ambient PM_2.5 mass, sulfate (SO₄^2-), nitrate (NO₃^-), ammonium (NH₄⁺), elemental carbon (EC), and organic carbon (OC) of PM_2.5 in participants' residences from conception to age six were estimated using predictive models. Multiple logistic regression analysis was used to analyze the association of respiratory/allergic symptoms and allergen sensitization with estimated exposure concentrations, after adjustment for survey year, sex, season of birth, feeding method during infancy, presence of siblings, history of lower respiratory tract infection, use of childcare facilities, passive smoking, presence of pets, mother's age, history of allergic diseases, smoking during pregnancy, and annual household income.

Results: No significant association was found between PM_2.5 and its component concentrations and asthma. However, wheezing significantly increased with mean NO₃^- concentrations during pregnancy (odds ratio of 1.64 [95% confidence interval: 1.10, 2.47] for an interquartile range increase). Significant associations were also found between EC in the second trimester of pregnancy and PM_2.5, NO₃^-, EC, and OC concentrations in early childhood. Higher PM_2.5, SO₄^-, and NH₄⁺ concentrations during the second trimester increased the risk of rhinitis. Sensitizations to HDM and animal proteins were significantly associated with exposure to components such as SO₄^2- and NH₄⁺ during pregnancy but not with postnatal exposure.

Conclusions: Exposures to NO₃^-, EC, and OC during pregnancy and early childhood were associated with wheezing. SO₄^2- and NH₄⁺ exposures during pregnancy were associated with sensitization to HDM and animal proteins. Asthma was not associated with exposure to PM_2.5 and its main components at any period.