Environment

Urban air quality is a major concern in both developed and developing countries. Besides being affected by human activities such as traffic congestion problems, air quality is also affected by the SO₂ emitted from smelters, electricity generators, iron and steel mills, petroleum refineries, and pulp and paper mills. Smaller sources include residential, commercial, and industrial space heating. Concentrations of SO₂ are toxic, contributing to poor air quality in cities and outlying areas, and harming human health and quality of life.

Canada earns a “B” grade for urban SO₂ concentration and ranks 13^th out of 17 peer countries. Most of the western European nations rank higher than Canada; only Belgium, Australia, the U.S., and Japan receive a lower ranking.

In this category, Italy was the best performer with an urban SO₂ concentration of 1.33 micrograms per cubic metre in 2004. Canada’s urban SO₂ concentrations were seven times greater than Italy’s, amounting to 9.32 micrograms per cubic metre. At the other end of the spectrum, Japan, the worst performer, had urban SO₂ concentrations more than twice those of Canada.

Historical data for urban SO₂ concentration are not available. However, data on overall (urban and non-urban) SO₂ emissions per capita are available from 1990.

Between 1990 and 2005, Canada decreased its per capita SO₂ emissions by 44 per cent. While any reduction is good, Canada’s progress was weaker than the progress made by 14 of the 16 peer countries. For example, Germany reduced its per capita emissions by 92 per cent, Denmark by 88 per cent, and the U.K. by 82 per cent. Japan’s reduction of 26 per cent was lower than that of Canada. Only one country—Australia—increased its SO₂ emissions between 1990 and 2005.

Increases in Australia’s SO₂ emissions can be attributed to its thermal electricity generation mix, which is dominated by fossil fuels, in particular coal. Over 1990 to 2005, demand for electricity in Australia grew at a consistent rate. Large industrial emitters such as the mining and metal industries also contributed to the increase in SO₂ emissions.

Use the drop-down menu to compare the change in Canada’s SO₂ emissions with that of its peer countries.

Since historical data for urban SO2 concentration are not available, the report card showing grade changes over time uses per capita total emissions, not urban concentrations. So even though Canada earns a “B” for urban SO2 concentration, it has only improved its grade for total per capita emissions from a “D” in the 1990s to a “C” grade in the current decade. Canada’s report card improvement was moderate relative to its peers. The U.S. improved to a “B” grade; Germany, Ireland, and the U.K. improved to an “A.” Only Australia remains with a lower grade than Canada.

The European peer countries have long outperformed both Canada and the U.S. on reductions in total SO₂ emissions and in SO₂ emissions per capita. Like Canada, the U.S. has reduced its emissions per capita only moderately.

The Europeans have shown that substantial reductions in SO₂ are possible over a relatively short time period. In 1990, for example, Germany’s total annual SO₂ emissions exceeded Canada’s by 2.2 million tonnes. By 2005, however, Germany had reduced its SO₂ emissions by a whopping 92 per cent—more than double Canada’s reduction over the same time period.

Germany’s reduction in SO₂ emissions has been due to replacing old combustion facilities with new ones that have the best available technology. Germany has also regulated desulphurization of flue gases in large combustion plants in the eastern part of the country and switched from solid to gaseous and liquid fuels. Since 2001, the national government has gone further, encouraging the consumption of low-sulphur fuel for vehicles by offering a tax discount.¹

The result? Germany decreased its total annual SO₂ emissions by 4.8 million tonnes within 15 years. In 2005, its emissions were 1.5 million tonnes lower than those in Canada.

Canada has ratified the United Nations Convention on Long-range Transboundary Air Pollution (LRTAP Convention), which has three international protocols to reduce SO₂ emissions. The first, the 1985 Sulphur Protocol, adopted a flat-rate target to reduce national annual sulphur emissions by at least 30 per cent between 1980 and 1993. The next two, the 1994 Sulphur Protocol and the 1999 Gothenburg Protocol to Abate Acidification, Eutrophication and Ground-level Ozone, are based on effects.² They aim to reduce sulphur emissions where environmental effects are most severe.

The 1985 Sulphur Protocol called for Canada to cap national SO₂ emissions permanently at 3.2 million tonnes by 1993. Canada met this cap in 1992, with national emissions of 3.1 million tonnes. The 1994 Sulphur Protocol allows emission reductions to be geographically targeted to achieve maximum environmental benefit. This approach is important for large, sparsely populated countries like Canada.

Canada has met all its current protocol commitments, including capping regional SO₂ emissions in the sulphur oxide management area (which includes parts of Quebec and Ontario, and all of New Brunswick, Nova Scotia, and P.E.I.) at 1.75 million tonnes by 2000.³

In 1998, Canada’s energy and environment ministers signed The Canada-Wide Acid Rain Strategy for Post-2000 to address the remaining acid rain problem in eastern Canada and to ensure Canada meets its international commitments to reduce emissions that cause acid rain. The strategy outlines actions to achieve critical loads (levels of acid rain that do not cause harm), establish new SO₂ emission reduction targets in eastern Canada, and pursue further reduction commitments from the United States.⁴

In 2000 and 2001, Ontario, Quebec, New Brunswick, and Nova Scotia established new provincial targets for SO₂ reductions under the strategy.⁵ In the future, targets and timelines will be developed for Canada’s sulphur oxide management area as part of the UN Protocol to Abate Acidification, Eutrophication and Ground-level Ozone. To ratify the protocol, Canada must specify emission ceilings for SO₂, nitrogen oxides, and volatile organic compounds.

SO₂ can directly harm human and animal respiratory systems, triggering respiratory illness and worsening existing respiratory and cardiovascular diseases. When dissolved by water vapour to form acids, it can further harm respiratory systems.

Combined with nitrogen oxides, these gases react with other substances to form acid precipitation, in the form of rain, fog, or snow. Acid rain damages vegetation, buildings, and materials, and it contributes to acidification of aquatic and terrestrial ecosystems.

When transformed into sulphate particles and combined with other particles in the atmosphere, SO₂ can contribute to the secondary formation of particulate matter (PM_2.5). PM_2.5 harms human health and the environment, and contributes to visibility impairment and regional haze.

¹ V. Vestreng et. al., “Twenty-five years of continuous sulphur dioxide emission reduction in Europe,” Atmos. Chem. Phys. Discuss, 7 (2007), p. 5119.

² United Nations Economic Commission for Europe, Convention on Long-range Transboundary Air Pollution, March 14, 2008, [online, cited August 19, 2008],

³ Environment Canada, What’s being done?, December 19, 2002, [online, cited August 19, 2008].

⁴ Canadian Council of Ministers of the Environment, Five-year Review of the Canada-Wide Acid Rain Strategy for Post-2000 (Ottawa: Canadian Council of Ministers of the Environment, December 2005).

⁵ Canadian Council of Ministers of the Environment, Five-year Review of the Canada-Wide Acid Rain Strategy for Post-2000 (Ottawa: Canadian Council of Ministers of the Environment, December 2005).

See discussions on other indicators
Urban NO2 concentration	Forest cover change
Urban SO2 concentration	Organic farming
VOC emissions	Use of forest resources
Urban PM10	Marine Trophic Index
Municipal waste generation	GHG emissions
Water Quality Index	Low-emitting electricity production
Water consumption	Energy intensity
Threatened species