Fine particulate matter exposure during pregnancy and infancy and incident asthma.

BACKGROUND

Lung development is a multistage process from conception to the postnatal period, disruption of which by air pollutants can trigger later respiratory morbidity.

OBJECTIVE

We sought to evaluate the effects of weekly average fine particulate matter (particulate matter with an aerodynamic diameter less than 2.5 μm [PM]) exposure during pregnancy and infancy on asthma and identify vulnerable times to help elucidate possible mechanisms of the effects of PM on asthma symptoms.

METHODS

A birth cohort study including 184,604 children born during 2004-2011 in Taichung City was retrieved from the Taiwan Maternal and Child Health Database and followed until 2014. A daily satellite-based hybrid model was applied to estimate PM exposure for each subject. A Cox proportional hazard model combined with a distributed lag nonlinear model was used to evaluate the associations of asthma with PM exposure during pregnancy and infancy.

RESULTS

The birth cohort contained 34,336 asthmatic patients, and the mean age of children given a diagnosis of asthma was 3.39 ± 1.78 years. Increased exposure to PM during gestational weeks 6 to 22 and 9 to 46 weeks after birth were significantly associated with an increased incidence of asthma. The exposure-response relationship indicated that the hazard ratio (HR) of asthma increased steeply at PM exposure of greater than 93 μg/m during pregnancy. Additionally, the HRs remained significant with postnatal exposure to PM between 26 and 72 μg/m (range, 1.01-1.07 μg/m), followed by a sharp increase in HRs at PM exposure of greater than 73 μg/m.

CONCLUSION

Both prenatal and postnatal exposures to PM were associated with later development of asthma. The vulnerable time windows might be within early gestation and midgestation and infancy.