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Summary

Thirty-years after the first edition of this report in 1971, there has been consistent improvement in the state of air quality in Ontario despite significant increases in population, economic activity and vehicle travel. Significant decreases have been achieved for sulphur dioxide, carbon monoxide, nitrogen dioxide, nitrogen oxides and total reduced sulphur compounds.

Encouraging as this is, there remains a great deal of work to be done. The Ontario government is directing increased emphasis on two key components of smog, namely ozone and particulate matter, which recent scientific evidence suggest have significant health effects.

Data analysis strongly indicates that neighbouring U.S. states – namely Ohio, Illinois and Michigan – are significant contributors to elevated levels of ozone and inhalable particles in southern Ontario. The contributions from long range transport and trans-boundary movement of these pollutants need further assessment. Continued monitoring is required to evaluate trends and determine the effectiveness of reduction and abatement strategies.

Ontario has continued to review and expand its existing air monitoring network by deploying real-time monitors of inhalable and respirable particles. In 2000, there were 43 ambient PM₁₀/PM_2.5 monitors operating across the province. The collection and assessment of such data will allow for improvement to the reporting of important air quality information to all Ontarians.