Environment

Nitrogen oxides contribute to smog and acid rain and are hazardous to human health and the environment. Nitrogen dioxide (NO₂) is released during the combustion of fossil fuels, mainly by vehicles, electricity generation, and manufacturing processes.¹ NO₂ is primarily a traffic-related pollutant, and emissions are highest in urban areas. It can block the transmission of light, reducing visibility in urban areas. On a larger scale, nitrogen oxides can originate in one place and be transported long distances by prevailing winds, contributing to poor air quality and acid rain in other urban and rural areas.

Canada ranks 6^th out of 17 peer countries. In 2004, Canada’s urban NO₂ concentration was 35 micrograms per cubic metre (population-weighted)—more than double the concentrations in Australia, the leader on this indicator.

Italy, Ireland, and the U.S. all received “D” grades. Their urban NO₂ concentrations are about twice that of Canada.

A combination of favourable geography and good policy put Australia in the top spot on this indicator. Australia benefits from a low population and low population density, relative to its peers in the OECD. Its island geography prevents any transboundary air pollution from entering via neighbouring countries. In Australia, local winds tend to rapidly disperse pollution over coastal cities, reducing urban air pollution concentrations.² The Australian government—along with state and territorial governments—has also developed national standards for six key air pollutants, including NO₂.³

Sweden and Finland also receive “A” grades. Sweden introduced an innovative fee-bate system for nitrogen oxide emissions in 1992. Large combustion plants are charged a fee for their emissions in proportion to the amount of energy they produce. The fee-bate system refunds the most efficient energy producers, while providing incentives for companies to become more efficient.⁴ Urban NO₂ concentration in Sweden is almost 50 per cent less than in Canada.

Historical data for urban NO₂concentration are not available. However, data on total (urban and non-urban) NO₂ emissions per capita are available from 1990. The good news is that Canada’s per capita total NO₂ emissions fell by 15 per cent between 1990 and 2005. The bad news is that Canada’s progress was weaker than 13 of the 16 comparator countries. Germany reduced its per capita emissions by 61 per cent, Switzerland by 52 per cent, and the U.K. by 48 per cent.

Grading countries by their per capita emissions changes some of their report cards dramatically. Although Australia’s urban NO₂ concentration is relatively low compared with the other OECD countries, its overall per capita NO₂ emissions are the highest of the peer countries. In urban Australia, the main sources of air pollution are motor vehicle emissions, wood smoke from home heating, and industrial pollution. Bushfires are another important source of air pollution in some parts of Australia. Between 1990 and 2005, higher vehicle and industrial emissions led to an increase in total NO₂ emissions in Australia, the only country to record an increase.

Use the drop-down menu to compare the change in Canada’s per capita NO₂ emissions with that of its peer countries.

No. Since historical data for urban NO2 concentration are not available, the report card showing changes over time grades per capita total emissions, not urban concentration. So even though Canada earns a “B” for urban NO2 concentration, it receives a “D” in the 1990s and most recent decade for per capita total emissions. Although Canada reduced its per capita NO2 emissions, other countries made larger reductions. The U.S. also receives a “D” grade in both periods, but it managed to reduce per capita NO2 emissions between 1990 and 2005 more than Canada did. In 2005, U.S. per capita NO2 emissions were about 37 per cent lower than in 1990. This suggests that Canada needs to do more to reduce NO2 emissions from its transportation, electricity, and industrial sectors.

Canada’s Clean Air Act, 2006, targets NO₂ emissions by regulating off-road and on-road vehicles and engines. Regulations on fuel consumption under the Motor Vehicle Fuel Consumption Standards Act have also been amended to sustain improvements in fuel efficiency after a voluntary agreement with the auto industry expires in 2010.

Polluting emissions ignore geographical borders and therefore require international partnerships to find sustainable solutions. Air pollution from the U.S., for example, is carried into southern Ontario, southern Quebec, and the Atlantic provinces, raising ambient air pollutant levels in these regions. Emissions transported from the U.S. can increase Canada’s NO₂ concentration and contribute to increases in ground-level ozone, a precursor to smog.

In 1991, Canada and the United States entered into the Canada–U.S. Air Quality Agreement to reduce emissions of nitrogen oxides (NO_x). Canada agreed to a 10 per cent reduction in projected emissions of NO_x by 2000. The Ozone Annex was added to the agreement in December 2000 to address the increasing problem of transboundary air pollution and its impact on ground-level ozone in Canada.

Ontario and Nova Scotia have provincial NO₂ emission reduction targets.

Nitrogen dioxide can irritate the lungs and lower resistance to respiratory infection. People with respiratory problems such as asthma and bronchitis, as well as children and the elderly, are particularly at risk.

NO₂ chemically transforms into nitric acid, which, when deposited as acid rain, contributes to lake acidification and harms aquatic ecosystems. It can also damage trees and crops, resulting in substantial environmental losses.

When NO₂ undergoes a chemical transformation in the atmosphere, it becomes a component of ground-level ozone and smog. Exposure to smog impairs lung function in the short term and accelerates deterioration in lung function over the long term.

¹ David Suzuki Foundation, The Maple Leaf in the OECD: Comparing Progress Toward Sustainability (Vancouver: The David Suzuki Foundation, 2005).

² Commonwealth Scientific and Industrial Research Organisation, Urban and Regional Air Pollution Information Sheet, April 11, 2006, [online, cited August 19, 2008].

³ Australian Government, National Standards for Criteria Air Pollutants in Australia, October 29, 2007, [online, cited July 10, 2008].

⁴ International Institute for Sustainable Development, The Nitrogen Oxide Charge on Energy Production in Sweden, [online, cited August 19, 2008].

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