January 29 | 2018

Human Health Risk Assessment for Gasoline Exhaust

Prepared by: Fuels Assessment Section Water and Air Quality Bureau Healthy Environments and Consumer Safety Branch Health Canada November 2017


Excerpt from Executive Summary

Gasoline, or spark ignition, engines are used throughout Canada, representing 92% of on-road vehicles and 87% of off-road engines or equipment. It is reasonable to assume that exposure to gasoline engine exhaust (GE) is nearly ubiquitous, particularly for Canadians living in urban areas or in close proximity to a major roadway: it is estimated that approximately 2 million people live within 50 m of a major road in Canada. GE is a highly variable and complex mixture of particulate and gaseous pollutants, the composition of which depends on numerous factors, including fuel quality, engine and pollution control technologies, vehicle operating conditions and ambient temperature. GE is an important source of criteria air contaminants (CACs) associated with adverse effects on human health, including fine particulate matter (PM2.5), ground-level ozone (O3), nitrogen dioxide (NO2), volatile organic compounds (VOCs) and carbon monoxide (CO). In addition, GE constituents include air toxics that are recognized internationally as carcinogens, such as benzene and polycyclic aromatic hydrocarbons (PAHs).

Gasoline fuel, vehicles and engines are subject to multiple federal regulations that have successfully reduced air pollutant emissions from gasoline mobile sources, representing a major success in the management of air quality in Canada and the protection of human health. However, given the number of vehicles and engines in use, the age structure of the in-use fleets, and the vehicle kilometres travelled by Canadians, gasoline engines remain a key source of air pollution. The adverse health effects of individual pollutants in GE or produced secondarily in the atmosphere from primary GE emissions (e.g. PM2.5, O3, NO2, benzene and PAHs), are well characterized in the scientific literature and include increased risk of cardiorespiratory mortality and morbidity and of cancer, among other outcomes.

This report is a comprehensive review and analysis of the potential adverse health effects associated with gasoline fuel use in Canada. Two distinct approaches are used. Part A provides an evaluation of scientific studies that have examined the health effects associated with exposure to GE as a mixture. Studies on the health effects of individual GE constituents, such as PM2.5 and benzene, were not considered, as these substances have been extensively reviewed by Health Canada elsewhere. Part B provides a quantitative assessment of the contribution of on-road and off-road gasoline mobile source emissions to individual air pollutant concentrations in Canada and the population health impacts associated with that incremental contribution. The health impact analysis in Part B, which is based on well-established quantitative estimates of risk of adverse health impacts associated with incremental changes in air concentrations of individual pollutants, is complementary to the traditional risk assessment approach presented in Part A.