Status and Trends

Smog relates to both emission and ambient components. The emission component pertains to the sources of the smog-forming pollutants and their emissions. The ambient component pertains to the levels in the ambient (i.e. the outside) air of some or all of the pollutants that comprise smog.

This section presents general information on the status of smog in Canada and the trends of the pollutants in Canada involved in smog formation.

Reports:

Fine Particles (PM_2.5) and Ozone in Canada, A Canada-wide Standards Perspective,  2003 National Summary

Report Highlights

• In 2001-2003, one in every two Canadians lived in communities with ozone levels above the Canada-wide Standards (CWS) for ozone.
• For the same period, one in every three Canadians lived in communities where the levels of fine particles (PM_2.5) were above the corresponding CWS.
• Nationally, PM_2.5 and ozone levels in 2003 were slightly higher than in previous years.
• Nationally, the annual average of all daily maximum 8-hour ozone levels (Dmax 8-hour O₃) increased on average by 4.5% over the period 1989-2003, while the annual 4th highest Dmax 8-hour O₃ remained essentially unchanged.
• Regionally, the annual average Dmax 8-hour O₃ increased in all regions of the country, with the trends being statistically significant only in southern Ontario and southern British Columbia. Although increases were recorded at most monitoring stations, statistically significant trends were mostly limited to urban stations.
• Regionally, the annual 4^th highest Dmax 8-hour O₃ decreased in southern British Columbia and Atlantic Canada, and increased in the other regions. These trends, however, were not statistically significant. The annual 4^th highest increased at most urban stations in eastern Canada, and decreased at many rural stations.
• The increase in ozone levels at urban stations may be a reflection of the reduced emissions of nitrogen oxides (NOx) from vehicles. While NOx is a precursor to ozone, it also reacts with ozone itself leading to ozone destruction. This phenomenon is referred to as "ozone scavenging".

2003 National Summary - Executive Summary report

Download a PDF copy of the Executive Summary

The full report can be downloaded at the following address: http://www.ccme.ca/assets/pdf/2003_pm_oz_ntnlsmryrpt_e.pdf