摘要：Primary ambient air pollutants, namely particulate matter ([PM.sub.2.5]), sulphur dioxide (S[O.sub.2]) and nitrogen dioxide (N[O.sub.2]), are largely emitted by anthropogenic sources such as vehicular traffic and industry. (1-3) Exposure to ambient air pollution has been associated with a range of adverse health outcomes in children. (1-3) Short-term (hours to days) exposure to [PM.sub.2.5], S[O.sub.2] and N[O.sub.2] has been associated with the exacerbation of existing respiratory conditions and symptoms (including asthma, pneumonia, bronchiolitis, decreased lung function) and with increases in emergency department visits and hospitalizations for respiratory diseases and symptoms in both healthy and asthmatic children. (1-4) Longer-term (months to years) exposure to [PM.sub.2.5], S[O.sub.2] and N[O.sub.2] has been associated with the development of chronic respiratory diseases or conditions, including asthma and decreased lung function and growth. (1-4) Recent studies also indicate adverse effects of air pollution on childhood neurodevelopment and cognition. (5)
Children are particularly vulnerable to the exposure to air pollution due to higher respiratory rates, larger lung-to-body size ratios, and more time spent outdoors than adults. (4) Further, children's organs and immune systems are in a critical period of development and thus the health effects of exposure to air pollution may be stronger. (4)
Studies in Europe and North America found that children of lower socio-economic status (SES) are more likely to live in homes that are closer to vehicle traffic (6,7) and industrial facilities, (8,9) and also have higher exposures to ambient [PM.sub.2.5]10 and N[O.sub.2]. (11-13) Children typically have less control over their living conditions, including their home or school location, which can result in involuntary exposure to environmental pollutants. Previous studies of children evaluating the associations between SES and exposure to air pollution have mainly focused on urban or traffic pollution sources near their homes. Quebec children spend at least 1080 hours per year at school and on school playgrounds, (14) and any exposures in these environments may pose a risk to their health. Previous studies from Europe and North America indicate that socially deprived children may be more likely to be exposed to air pollution and its resulting health impacts, including acute and chronic respiratory and neurocognitive outcomes. (5,15) Yet very few studies have evaluated school exposure to industrial-related air pollution (9) or its association with levels of socio-economic deprivation. Moreover, no studies have evaluated correlations for varying indicators of socio-economic conditions of children.
