dc.description.abstract | Introduction:
Outdoor air pollution had adverse effects on human health. Several studies indicated that outdoor air pollution was associated with respiratory symptoms and morbidity. These respiratory adverse effects on children’s health may lead to school absences in children that affect children’s learning and school performance. To assess the adverse effects of outdoor air pollution on children’s health, illness-related school absences, especially respiratory illness-related absences, was an important outcome. There were few studies for the association between air pollution and school absenteeism, and the results were inconsistent.
Purpose:
The aim of the study was to investigate the effects of outdoor air pollution on school absenteeism among elementary school children in Taiwan, with focus on illness-related and respiratory illness-related school absences.
Materials and Methods:
This was a longitudinal cohort study that recruited 2,915 5th-grade school children from16 elementary schools in 10 communities in Taiwan from August 2010 to April 2011. The information of school absences including absence date, daily counts and causes of school absences were collected. Data of air pollutants including particulate matter with a aerodynamic diameter less than 10 μm (PM10) and 2.5 μm (PM2.5), sulfur dioxide (SO2), nitrogen oxides (NOx), nitrogen monoxide (NO), nitrogen dioxide (NO2), ozone (O3), and carbon monoxide (CO) were obtained from Taiwan Environmental Protection Agency (EPA) air monitoring stations. Except daily 8-h average from 10 am to 6 pm of O3, daily 24-h average concentrations of air pollutants were used. We conducted case-crossover design with time-stratified strategy for control sampling to examine the association between concentrations of air pollutants and the risk of school absences. Conditional logistic regression with single pollutant model was applied in statistic analysis. Daily average ambient temperature and rainfall were adjusted in regression models. Different lag periods including same-day lag (lag0) and 3 single-day lags (lag1, lag2, lag3) were tested. The effect estimates were presented as odds ratios (ORs) per 1 unit increase in CO and per 10 units increase in other pollutants. Single community-level effect estimate of each air pollutant on different types of school absences was obtained for each of ten communities. We further combined community-level effect estimates according to area where the community located, including Northern, Central, Southern and Eastern area to get area-level effect estimate.
Results:
There were total 1,396 school absence counts during study period and the most were respiratory illness-related school absences. In single-community level, short-term exposure to NOx, NO and NO2 was associated with the risk of illness-related and respiratory illness-related school absences. In area-level with focus on the effects of NOx, NO and NO2 at different lags on illness-related and respiratory illness-related school absences, the effects varied among areas. In Northern area including communities of Wanhua, Pingzhen, Jhudong and Shinchu, acute exposure to NOx, NO and NO2 was significantly associated with the risks of illness-related and respiratory illness-related school absences. The largest effects of NOx, NO and NO2 on illness-related and respiratory illness-related school absences were all at same-day lag (for illness-related school absences: OR=1.24, 95% confidence interval (CI)=1.13-1.37; OR=1.41, 95% CI=1.18-1.70; OR=1.42, 95% CI=1.19-1.68; for respiratory illness-related school absences: OR=1.20, 95% CI=1.07-1.34; OR=1.38, 95% CI=1.12-1.69; OR=1.30, 95% CI=1.07-1.58, for every 10 ppb increase in NOx, NO and NO2 respectively). As for respiratory illness-related school absences in Northern area, there was a trend of NO2 effect that was largest at same-day lag and decreased with increasing day lags (from lag 0 to lag 3).
Conclusion:
This study indicated that in Northern area in Taiwan, short-term exposure to NOx, NO and NO2 was associated with the schoolchildren’s risks of illness-related and respiratory illness-related school absences and the largest effects were at same-day lag. In Northern area, the effect of acute exposure to NO2 on respiratory illness-related school absences was largest at same-day lag and declined with increasing day lags from same-day lag to 3-day lag. | en |