Fine particulate matter exposure and incident atopic dermatitis: a birth cohort study.

Background: The association between exposure to fine particulate matter (PM2.5) from conception to 1 year after birth and the later development of atopic dermatitis (AD) has not been completely elucidated.

Objectives: To investigate the effects of PM2.5 exposure during pregnancy and infancy on the later development of AD, and to explore vulnerable time periods to identify biologic pathways that may result in AD after exposure to PM2.5.

Methods: We conducted a birth cohort study comprising 564 869 term births born between 2004 and 2013. The infants were followed-up until 5 years after birth. A satellite-based model was used to calculate PM2.5 exposure for each child. A Cox proportional hazards model combined with a distributed lag nonlinear model was created to examine the associations of AD with PM2.5, as well as the dose-response relationship.

Results: The birth cohort comprised 76 944 infants diagnosed with AD. Increased cumulative exposure to PM2.5 from 34 weeks' gestation until birth, as well as from 33 weeks after birth, was significantly associated with a higher incidence of AD. With regard to the dose-response relationship, exposure to > 65 μg m-3 PM2.5 sharply increased the risk of AD.

Conclusions: Prenatal and postnatal exposure to PM2.5 was related to later development of AD. The sensitive time periods may be late gestation and early life after birth.