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Canadian Ozone and PM2.5 Standards

Canada-Wide Standards (CWSs) for particulate matter (PM) and ozone were passed at a meeting in Quebec City in June 2000. The ozone standard is the 3-year average of the 4th highest daily maximum 8-hour average concentration set at a level of 65 ppb. In addition to the 8-hour ozone standard, a Canadian PM2.5 standard of 30 ug/m3 for 24 hours at the 98th percentile averaged over 3 years was passed. The compliance dates for both standards is 2010. Additional information can be found by clicking here.

The Canadian ozone standard is near natural background ozone levels. Although there are provisions in the implementation of the ozone standard to consider background levels, the ability to achieve the ozone standard is very much in doubt. Science appears to have played a minor role in determining the level of the proposed ozone standard. It appears that a regression has been done between the 3-year average of the 4th highest 8-hour daily maximum concentration and the daily hourly maximum concentration. The assumption is that it is possible to develop a mathematical relationship that results in the 3-year average of the 4th highest daily maximum 8-hour concentration of 65 ppb being comparable to the past Canadian hourly objective concentration of 82 ppb. Experiences have shown that such is not the case. The most current 8-hour maps illustrating Canadian ozone exposures can be found in our mapping web site.

The Canadian government has realized that, in some cases, exceedances of the two standards may be due to activities not related to environmentally derived Canadian air pollution sources. In jurisdictions highly impacted by transboundary air pollution from the United States, achieving the CWSs will be strongly dependent on reductions of this transboundary contribution. Also,
high background levels of PM and ozone that may occur through natural events, such as forest fires, natural formation, and stratospheric intrusion, will need to be considered in assessing
achievement of the CWSs.

Any party may withdraw from the Canada-Wide Standards upon three month's notice. The Canada-Wide Standards come into effect on the date of signing.


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