SUSTAINING the ENVIRONMENT and RESOURCES for CANADIANS

What is the issue?

Ground-level ozone and fine particulate matter (PM_2.5 ) are two key components of smog and have significant negative impacts on human health, on the natural environment and, consequently, on economic performance. Human exposure to these pollutants is of concern because there are no established thresholds below which these pollutants are safe and do not pose a risk to human health.

What is happening?

• At the national level, from 1990 to 2004, the ground-level ozone indicator showed year-to-year variability with an average increase of 0.9% per year.
• 2004 ground-level ozone values were the highest at monitoring stations in southern Ontario, followed by Quebec/eastern Ontario. Southern Ontario has exhibited increasing trends since 1990, while other regions showed no noticeable increase or decrease.
• The highest PM_2.5 levels for 2004 were in southern Ontario, although some areas in eastern Quebec also showed high levels. There was no discernible national trend for PM_2.5 during the period 2000 to 2004.

Why is it important?

Ground-level ozone and PM_2.5 have been linked to health impacts ranging from minor respiratory problems to cardiovascular disease, hospitalizations and premature death. Related economic effects include absenteeism, lower labour force participation and increased health care costs.

Why is it happening?

Ozone is formed by chemical reactions involving nitrogen oxides (NO_x) and volatile organic compounds (VOC) in the presence of sunlight. Human activities contribute to the formation of ground-level ozone by increasing the concentrations of NO_x and VOC, primarily through the burning of fossil fuels in motor vehicles, homes, industries and power plants. Paints, cosmetics and the evaporation of liquid fuels and solvents also add VOC to the air. Ozone concentrations are affected not only by local activities, but also by weather conditions and the movement of pollutants from other regions and countries.

The sources of PM_2.5 are varied. NO_x, sulphur dioxide, ammonia and VOC emissions all contribute to its formation and their interaction is affected by meteorological conditions. PM_2.5 is also emitted directly as a pollutant. Transportation and industrial emissions are the main contributors, but wood burning for home heating is also a significant source, especially in the winter. Dust from wind erosion and ash from forest fires are natural sources of PM_2.5 and contribute to the overall total.

What’s next?

Indicator development

The current indicators represent separate estimates of average population exposure to both ozone and PM_2.5. This pair of indicators represents a midway point on the continuum from ambient air quality data towards an indicator that uses pollution exposure estimates to derive an indicator based on risk to human health. Health Canada is examining the feasibility of a broader indicator based on the health risk caused by exposure to a combination of several air pollutants (an Air Health Indicator).

Monitoring

Environment Canada will continue to invest in new instruments to fill gaps in pollutant coverage at existing monitoring facilities and to establish new stations.A priority will be placed on upgrading existing continuous PM_2.5 monitoring instruments and improving the sampling and consistency for monitoring of PM_2.5 during cold seasons.

Analysis

Work is progressing to provide means of fully exploiting the available data to obtain better estimates of national and regional trends in air quality through the use of interpolation and modelling.

Another important area of research is determining the relative importance of the various factors that affect observed levels of air pollution. For instance, long-range transport of pollutants, sunlight, temperature and pollutant emissions all contribute to observed levels of ozone and PM_2.5, but the extent of their contributions remains unknown.

Surveys

In early 2006, Statistics Canada surveyed Canadian households regarding selected environmental practices, such as commuting practices and ownership of household gasoline-powered equipment, to provide additional context for the air quality indicators. Initial results of this survey will be available in late 2006, and full results will come out in 2007.