Ambient air pollution causes substantial environmental effects ranging from changes in air quality to changes in temperature. Over time, these effects have the potential to modify the way we function. Epidemiological studies on the effects of air pollution on healthy adult subjects suggest an association between exposure to ambient air pollution and heightened risk of chronic diseases. It remains unclear to what extent do the heightened health risks associated with air pollution take hold at an early age and in what way do these risks contribute to the onset of long-term disease. Epidemiological studies of asthmatic children have shown an association between pollution and baseline lung function. However, few studies have assessed the effects of ambient air pollution on lung function in healthy children. Such an association, if found, would suggest that the effects of air pollution may be cumulative and could start at an early age.
In this retrospective cross-sectional analysis, we assess whether there is a potential relationship between air pollution on the day of testing and risk of exercise-induced bronchospasm (EIB) in healthy children and asthmatic children. The cohort used in this study comprises all of the 2469 school children from grades one through six in the town of Port Alberni on the west coast of the island of Vancouver, Canada. Each child underwent a pre-exercise and post-exercise spirometry test. We analyze change in lung performance relative to the concentration of airborne particulate matter (PM) while controlling for ambient weather conditions (temperature, humidity, etc.) on the day of testing.
By determining whether these daily environmental effects bear a relationship to the risk of EIB, we determine: 1) whether airborne particulate matter concentration affects the exercise-induced fall in lung function in healthy children, and 2) whether the effect differs when comparing non-asthmatic to asthmatic children (effect modification by asthma).
Our analysis concludes that lower airborne water concentration (a function of temperature and humidity) increases the risk of EIB. Contrary to our hypothesis, lower particulate matter concentrations increase the risk of EIB. There are substantive differences in EIB prevalence between asthmatics and non-asthmatics. These findings have potential implications for recommendations regarding exercise outdoors on cold, low humidity days. It remains unclear whether the effects of air pollution start at an early age and could lead to the onset of long-term asthma.