Prenatal exposure to ambient fine particulate matter and child lung function in the CANDLE cohort

Abstract

Background: Ambient fine particulate matter (PM_2.5) exposure adversely impacts child airway health; however, research on prenatal PM_2.5 exposure, and child lung function is limited. We investigated these associations in the ECHO-PATHWAYS Consortium, focusing on the role of exposure timing during different phases of fetal lung development.

Methods: We included 675 children in the CANDLE cohort born between 2007 and 2011 in Memphis, TN, USA. Prenatal exposure to ambient PM_2.5 was estimated using a spatiotemporal model based on maternal residential history and averaged over established prenatal periods of lung development. Forced expiratory volume in the first second (FEV1) and forced vital capacity (FVC) were measured by spirometry at age 8-9 years. We used linear regression and Bayesian Distributed Lag Interaction Models (BDLIM) to estimate associations between exposure and lung function z-scores, adjusting for maternal/child characteristics, prenatal/postnatal tobacco exposure, and birth year/season, and evaluating effect modification by child sex and allergic sensitization.

Results: The average ambient concentration of PM_2.5 during pregnancy was 11.1 µg/m³ (standard deviation:1.0 µg/m³). In the adjusted linear regression and BDLIM models, adverse, but not statistically significant, associations were observed between exposure during the pseudoglandular (5-16 weeks of gestation) and saccular (24-36 weeks) phases of lung development and FEV1 and FVC. The strongest association was between a 2 μg/m³ higher concentration of PM_2.5 during the saccular phase and FEV1 z-score (-0.176, 95% Confidence Interval [CI]: -0.361, 0.010). The FEV1/FVC ratio was not associated with PM_2.5 in any exposure window. No effect modification by child sex or allergic sensitization was observed.

Conclusions: We did not find strong evidence of associations between prenatal ambient PM_2.5 exposure and child lung function in a large, well-characterized study sample. However, there was a suggested adverse association between FEV1 and exposure during late pregnancy. The saccular phase of lung development might be an important window for exposure to PM_2.5.

Keywords: PM2.5; air pollution; airway; children’s health.

Figure 1.

(A) Association between prenatal PM_2.5 exposure during mutually-adjusted periods of fetal lung development and child lung function. Estimated coefficients (β) and 95% confidence intervals (CI) represent the change in lung function GLI-Global z-scores associated with a 2-µg/m³ increase in PM_2.5 concentration in linear regression models. Minimally adjusted models were adjusted for child age at assessment and child sex. Primary models were additionally adjusted for recruitment site, maternal education at enrollment, NDI, child race, child height, household income, maternal report of smoking during pregnancy, postnatal smoke exposure, recent asthma medication use, and maternal history of asthma. Extended models were additionally adjusted for gestational age, birth weight, maternal BMI, firstborn status, season of outcome assessment, and the ambient concentration of PM_2.5 in the two weeks prior to spirometry. (B) Results of BDLIM analysis of association between prenatal PM_2.5 exposure throughout gestation (per 2-µg/m³ increase in PM_2.5 during a given two-week period) and child lung function, using primary model adjustment.

Figure 2.

Effect modification by (A) child sex and (B) allergic sensitization in the association between prenatal PM_2.5 exposure during periods of lung development and child lung function. Estimated coefficients (β) and 95% confidence intervals (CI) show the change in lung function GLI Global z-scores associated with a 2 µg/m³ increase in PM_2.5 concentration. Strata-specific results were derived from interaction models; p-values are for the interaction term between the modifier and PM_2.5 concentrations. Models were adjusted for child age at assessment, child sex, recruitment site, maternal education at enrollment, NDI, child race, child height, household income, maternal report of smoking during pregnancy, postnatal smoke exposure, recent asthma medication use, and maternal history of asthma.