Changes in the relationship between ambient fine particle concentrations and childhood lung function over 5 years

Background: Exposure to ambient fine particles, particulate matter with an aerodynamic diameter of ≤2.5 μm (PM_2.5), is a public health concern. Concentrations of ambient PM_2.5 have changed temporally in the past 10 years after a series of action policies for improving air quality were implemented in Taiwan. In this study, temporal changes in the relationship between PM_2.5 and lung function among children were investigated.

Methods: A nationwide respiratory health survey was conducted among Taiwanese elementary and middle school students in 2011 and again in 2016-2017. A questionnaire was administered to students, for whom forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV₁) were measured using spirometry. During the study period, monthly concentrations of ambient PM_2.5 were obtained from the monitoring stations of the Environmental Protection Administration. Lung function measurements were compared with ambient PM_2.5 exposure using mixed-effects models.

Results: In the 2011 survey (mean PM_2.5: 40.6 μg/m³), exposure to PM_2.5 in the preceding 1-2 months was associated with a 2.2% decrease (95% confidence interval [CI]: -4.1%, -0.3%) in FVC and a 2.3% decrease (95% CI: -4.0%, -0.5%) in FEV₁. By contrast, a significant relationship between PM_2.5 concentrations and lung function was not observed in the 2016-2017 survey (mean PM_2.5: 30.0 μg/m³).

Conclusions: As improvement in air quality over time, the negative relationship between PM_2.5 and childhood lung function tend to be not significant.