Spatial Health Lab

Canadian cities generally have good air quality; however, exposure to outdoor air pollution continues to elicit considerable negative health effects. Estimates suggest that there are 21 000 premature deaths attributable to air pollution in Canada each year,1 nearly 9 times higher than the number of deaths due to motor vehicle collisions. Emerging evidence specifically links the traffic-related component of air pollution to negative effects on health. A comprehensive critical review of the epidemiologic and toxicologic literature published in 2010 concluded that exposure to traffic-related air pollution was causally linked to worsening asthma.2 The evidence was characterized as bordering on sufficient for a causal link with incident childhood asthma,2 whereas associations with adult-onset asthma, deteriorating lung function, cardiovascular death, myocardial infarction and the progression of atherosclerosis were deemed suggestive but insufficient to infer causality. Subsequent evidence shows a strengthened case for causal relationships between exposure to traffic-related air pollution and incident asthma, as summarized in a meta-analysis,3 and with lung cancer, as stated by the International Agency for Research on Cancer’s classification of diesel engine exhaust as carcinogenic to humans.4 Increasing support for the role of traffic-related air pollution in cardiovascular morbidity and mortality is summarized in a recent scientific statement from the American Heart Association, which concluded that “traffic-related pollution as a whole appears to be a specific source associated with cardiovascular risk.”5 This conclusion is supported by experimental and epidemiologic evidence that suggests that air pollution leads to systemic inflammation, oxidative stress and imbalance in the autonomic nervous system.5