Long-term exposure to PM10 and NO2 in association with lung volume and airway resistance in the MAAS birth cohort

Abstract

Background: Findings from previous studies on the effects of air pollution exposure on lung function during childhood have been inconsistent. A common limitation has been the quality of exposure data used, and few studies have modeled exposure longitudinally throughout early life.

Objectives: We sought to study the long-term effects of exposure to particulate matter with an aerodynamic diameter ≤ 10 μm (PM10) and to nitrogen dioxide (NO2) on specific airway resistance (sR(aw)) and forced expiratory volume in 1 sec (FEV1) before and after bronchodilator treatment. Subjects were from the Manchester Asthma and Allergy Study (MAAS) birth cohort (n = 1,185).

Methods: Spirometry was performed during clinic visits at ages 3, 5, 8, and 11 years. Individual-level PM10 and NO2 exposures were estimated from birth to 11 years of age through a microenvironmental exposure model. Longitudinal and cross-sectional associations were estimated using generalized estimating equations and multivariable linear regression models.

Results: Lifetime exposure to PM10 and NO2 was associated with significantly less growth in FEV1 (percent predicted) over time, both before (-1.37%; 95% CI: -2.52, -0.23 for a 1-unit increase in PM10 and -0.83%; 95% CI: -1.39, -0.28 for a 1-unit increase in NO2) and after bronchodilator treatment (-3.59%; 95% CI: -5.36, -1.83 and -1.20%; 95% CI: -1.97, -0.43, respectively). We found no association between lifetime exposure and sR(aw) over time. Cross-sectional analyses of detailed exposure estimates for the summer and winter before 11 years of age and lung function at 11 years indicated no significant associations.

Conclusions: Long-term PM10 and NO2 exposures were associated with small but statistically significant reductions in lung volume growth in children of elementary-school age.

Figure 1

Outline of exposure assessment showing methods used to estimate concentrations in each microenvironment (with relevant references). The same methods were used at all time points except for the year before the age 11 review. A detailed indoor model could be used to estimate concentrations inside the kitchen, living room, and child’s bedroom. Abbreviations: I/O, Indoor to outdoor ratio; MEEM, micro­environmental exposure model.

Figure 2

Flow diagram of MAAS cohort showing participation rates at each review, the number of lung function measurements collected, and the number of exposure estimates available.