Air pollutants study offers recommendations to fight rise in Canada’s diesel truck traffic

overview of highway intersection traffic
Over the past decade truck sales have risen 20% (in particular harmful diesel-emission trucks), and it’s a recipe for concern, according to a new study. Photo credit: Denys Nevozhai, Unsplash.

A new report has a series of recommendations for Canadian cities to battle air pollution, stemming not only from a growth in major roadway traffic, but a jump in dangerous diesel truck traffic that may be linked to the online shopping boom.

While nearly one-third of Canadians live within 250 metres of a major road and are exposed to traffic emissions, six monitoring sites across Vancouver and Toronto found that Canada’s largest cities have the highest concentrations of vehicle air pollution.

The two-year (2015–2017) study into traffic-related pollutant concentrations near major roadways considers that almost 25 million cars and trucks were on Canadian roads in 2017, and that the number of people commuting into cities by car has also increased by 28% in the past two decades. Add to this that over the past decade truck sales have risen 20% (in particular harmful diesel-emission trucks), and it’s a recipe for concern.

“Exposure to traffic emissions has been associated with a wide range of adverse health outcomes, including increased risk of respiratory diseases such as asthma, birth and developmental concerns, cancer, and cardiovascular and respiratory mortality,” the study’s authors report. “While some individual pollutants in traffic exhaust are toxic, it is the combination of the many pollutants present in emissions that is of concern.”

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Led by the Southern Ontario Centre for Atmospheric Aerosol Research (SOCAAR) at the University of Toronto, in collaboration with Environment and Climate Change Canada, the Ontario Ministry of the Environment, Conservation and Parks, and Metro Vancouver, the new study found that the average concentrations of ultrafine particles at highway sites were four times higher than at a background site away from traffic.

Additionally, over 80% of the nitrogen monoxide and 60% of the black carbon found also came from nearby traffic at highway sites. The majority of black carbon emissions are due to diesel trucks at the highway site, the study found. Diesel exhaust, the study’s authors say, is a recognised human carcinogen that contains a large number of chemical compounds both as gases and within particles. Some of these compounds, such as black carbon and nitrogen oxides are commonly used as markers to estimate exposure to diesel exhaust.

Not surprisingly, the study found that the concentrations of traffic pollutants were highest on weekdays during morning rush hour. Concentrations were lower in the morning on weekends, consistent with lower weekend morning traffic.

Study Recommendations

Target highly polluting trucks. Methods are needed to distinguish between low-emitting, average, and highly-polluting trucks. Technologies need to be developed and validated to more easily allow on-road or roadside identification and testing of truck emissions.

Eliminate tampering. Substantial fines or loss of license should be imposed on operators caught tampering with vehicle emission systems. Trucks equipped with modern emission treatment systems should not be highly polluting.

Repair, retrofit, retire or relocate. Older trucks identified as highly polluting should be repaired, retrofitted, retired or restricted in their operation away from neighbourhoods or facilities with vulnerable populations. Exposure could also be reduced by constraining their operation to designated off-hour time windows.

Recognize and reward low emitters. Government should create standards and processes to identify and certify diesel vehicles that are low emitting.

Improve data on truck traffic. Better estimates are needed of the proportion of trucks of different sizes on major roads across Canada. The data will allow better estimation of the number of Canadians being exposed to diesel exhaust.

Develop ambient air quality standard for diesel exhaust. Canada should develop an index or ambient air quality standard for diesel exhaust. Such a standard will provide a useful reference to assess and compare the levels at different sites.

Incorporate Canada’s winters in emission regulations. The effect of cold winter temperatures on emission of nitrogen oxides from trucks needs to be better understood. Specifically, more direct testing of the associated emission treatment technologies is needed.

Investigate the influence of seasonal fuel formulations. Higher concentrations of black carbon were observed at the Toronto sites in summer. This may be due to increased emissions from diesel vehicles caused by changes in diesel.

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