Traffic-related air pollution and health in Canada

Exposure to traffic-related air pollution in Canada

Based on available data on census block points and the National Road Network,2^,6 about 10 million people — 32% of the Canadian population — live in areas where they are exposed to traffic-related air pollution (exposure zones). These elevated exposure zones are defined as the 500 m on either side of highways (average daily traffic ≥ 18 000 vehicles) or the 100 m on either side of major urban roads (average daily traffic ≥ 15 000 vehicles, ≥ 2 lanes spanning several kilometres, speed limit > 50 km/h).6 Using alternative metrics gives a lower-bound estimate of 4.1 million people (people living within 100 m of a major road or highway; ~13% of the Canadian population) and an upper-bound estimate of 16.9 million people (people living within 500 m of a major road or highway; ~54% of the Canadian population) living in areas of high exposure. This high prevalence of exposure, in addition to evidence of associated health problems, suggests that traffic-related air pollution is a substantial public health concern in Canada and points to the need for policies to reduce population exposure.

Mitigating exposure and risks

Reducing exposure to a hazard that is deeply integrated within modern society is difficult and must be addressed with diverse, coordinated policies. In a review of the published and grey literature,6 we identified 4 broad and potentially overlapping mitigation strategies: reducing vehicle emissions; modifying existing infrastructure; land-use planning and transportation management; and encouraging behavioural change (Box 1). In the short term, policies and regulations that target existing infrastructure and vehicles are likely to be most effective in reducing exposure because they operate at the population level. In the long term, land-use planning that incorporates health impact assessments can influence the siting of new buildings or roads such that exposure is minimized.

Although studies directly measuring health benefits related to mitigating traffic emissions are limited, a recent review concluded that there is consistent evidence that interventions targeting air pollution in general lead to a reduction in adverse health effects.7 For example, a scheme in London, United Kingdom, in which drivers of vehicles operating within a “congestion charge zone” were charged a fee, reduced traffic volume and congestion, resulting in an estimated gain of 183 years of life per 100 000 residents within the zone over a 10-year period.8 Similarly, the establishment of low-emission zones and the consequent decrease in pollution in Rome, Italy, was estimated to have resulted in 921 years of life gained per 100 000 residents living near major roads over 10 years.9

Although these interventions alone benefit health,7 combining strategies can result in more cost-effective policies and greater improvements to population health. In particular, policies that encourage integrated land-use planning or that increase active transportation would lead to decreases in air pollutants and greenhouse gas emissions, and increases in physical activity. In the Midwestern United States, replacing short car trips (≤ 1.6 km) with active commuting had an estimated net health benefit of $4.94 billion per year from reduced air pollution and $8 billion per year from the combined benefits of improved air quality and physical fitness.10

• Epidemiologic studies suggest causal links between exposure to traffic-related air pollution and negative effects on health.

• One-third of Canadians live in areas with high exposure to traffic-related air pollution.

• Exposure to traffic-related air pollution can be reduced by targeting vehicle emissions, modifying structures, land-use planning, transportation management and changing behaviour.

• Policies to reduce Canadians’ exposure to traffic-related air pollution should be aligned with efforts to increase physical activity and decrease emissions related to climate change.