Associations between prenatal and early-life air pollution exposure and lung function in young children: Exploring influential windows of exposure on lung development

Abstract

Background: Evidence in the literature suggests that air pollution exposures experienced prenatally and early in life can be detrimental to normal lung development, however the specific timing of critical windows during development is not fully understood.

Objectives: We evaluated air pollution exposures during the prenatal and early-life period in association with lung function at ages 6-9, in an effort to identify potentially influential windows of exposure for lung development.

Methods: Our study population consisted of 222 children aged 6-9 from the Fresno-Clovis metro area in California with spirometry data collected between May 2015 and May 2017. We used distributed-lag non-linear models to flexibly model the exposure-lag-response for monthly average exposure to fine particulate matter (PM_2.5) and ozone (O₃) during the prenatal months and first three years of life in association with forced vital capacity (FVC), and forced expiratory volume in the first second (FEV₁), adjusted for covariates.

Results: PM_2.5 exposure during the prenatal period and the first 3-years of life was associated with lower FVC and FEV₁ assessed at ages 6-9. Specifically, an increase from the 5th percentile of the observed monthly average exposure (7.55 μg/m³) to the median observed exposure (12.69 μg/m³) for the duration of the window was associated with 0.42 L lower FVC (95% confidence interval (CI): -0.82, -0.03) and 0.38 L lower FEV₁ (95% CI: -0.75, -0.02). The shape of the lag-response indicated that the second half of pregnancy may be a particularly influential window of exposure. Associations for ozone were not as strong and typically CIs included the null.

Conclusions: Our findings indicate that prenatal and early-life exposures to PM_2.5 are associated with decreased lung function later in childhood. Exposures during the latter months of pregnancy may be especially influential.

Keywords: Air pollution; Distributed lag-models; Influential windows of exposure; Lung function.

Figure 1:

Exposure-response corresponding to the cumulative effect of PM_2.5 exposure during the prenatal months and first 3 years of life for FVC. The exposure-response is centered so that the null corresponds to the lowest observed exposure (3.69 μg/m³), while the boxplot at the bottom of the figure corresponds to the monthly average exposure distribution for the window of interest across participants.

Figure 2:

Exposure-response corresponding to the cumulative effect of PM_2.5 exposure during the prenatal months and first 3 years of life for FEV₁. The exposure-response is centered so that the null corresponds to the lowest observed exposure (3.69 μg/m³), while the boxplot at the bottom of the figure corresponds to the monthly average exposure distribution for the window of interest across participants.

Figure 3:

Lag-response for the effect on FVC of monthly average exposure to PM_2.5 set at 10 μg/m³ compared to the lowest observed exposure (3.69 μg/m³) for each month in the exposure window of interest. The x-axis represents month of exposure with zero corresponding to the first month of pregnancy.