Ambient Levels of Nitrogen Dioxide

Nitrogen dioxide (NO2) belongs to a group of nitrogen-containing substances called nitrogen oxides (NOx). NOx are emitted to the atmosphere from high-temperature combustion processes such as car engines, power plants and industrial processes. Although primarily emitted as nitric oxide (NO), NO2 is rapidly formed when NO reacts with ozone (O3) and volatile organic compounds (VOCs). The major sources of NO2 in Canada are on-road and off-road vehicles, the oil and gas industry, and the use of fuel for electricity generation and heating. NO2 plays an important role in the formation of O3 in the atmosphere. It is a precursor to fine particulate matter (PM2.5), and contributes to acid rain. NO2 also has adverse health effects: it can irritate the lungs, decrease lung function, and increase susceptibility to allergens for people with asthma.

National ambient level of nitrogen dioxide

In Canada, the annual average concentration of nitrogen dioxide (NO2)Footnote[1] in the air for 2011 was 10.6 parts per billion (ppb), less than 1% lower than in 2010. A declining trend was detected from 1997 to 2011, representing a decrease of 41% over that period. The decrease for the NO2 indicator is consistent with the reduction in NOx emissions from cars and trucks as a result of the introduction of more stringent emissions standards by the federal government.

Nitrogen dioxide concentrations, Canada, 1997 to 2011

Nitrogen dioxide concentrations, Canada, 1997 to 2011

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How this indicator was calculated

Note: The national NO2 indicator is based on the annual average of the daily concentrations recorded at 68 monitoring stations across Canada. A trend line is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2013) National Air Pollution Surveillance (NAPS) program.

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Regional ambient levels of nitrogen dioxideFootnote[2]

Southern Quebec

In southern Quebec, the annual average concentration for nitrogen dioxide (NO2) in outdoor air for 2011 was 10.3 parts per billion (ppb), 2% lower than in 2010. A declining trend was detected from 1997 to 2011, representing a decrease of 41% over that period. This decrease is mostly attributable to the reduction in nitrogen oxide (NOx) emissions from cars and trucks, as a result of more stringent emissions standards.

Nitrogen dioxide concentrations, southern Quebec, 1997 to 2011

Nitrogen dioxide concentrations, southern Quebec, 1997 to 2011

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How this indicator was calculated

Note: For southern Quebec, the NO2 indicator is based on the annual average of the daily concentrations recorded at 14 monitoring stations. A trend line is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2013) National Air Pollution Surveillance (NAPS) program.

Southern Ontario

In southern Ontario, the annual average concentration of nitrogen dioxide (NO2) in the air for 2011 was 11.1 parts per billion (ppb), or 2% lower than in 2010. A declining trend was detected from 1997 to 2011, representing a decrease of 49% over that period. This decrease is mostly attributable to the reduction in nitrogen oxide (NOx) emissions from cars and trucks, as a result of more stringent emissions standards.

Nitrogen dioxide concentrations, southern Ontario, 1997 to 2011

Nitrogen dioxide concentrations, southern Ontario, 1997 to 2011

View data for this chart
How this indicator was calculated

Note: For southern Ontario, the NO2 indicator is based on the annual average of the daily concentrations recorded at 16 monitoring stations. A trend line is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2013) National Air Pollution Surveillance (NAPS) program.

Prairies and northern Ontario

In the Prairies and northern Ontario, the annual average concentration of nitrogen dioxide (NO2) in the air for 2011 was 10.9 parts per billion (ppb), or 4% lower than in 2010. A declining trend was detected from 1997 to 2011, representing a decrease of 33% over that period. This decrease is mostly attributable to the reduction in nitrogen oxide (NOx) emissions from cars and trucks, as a result of more stringent emissions standards.

Nitrogen dioxide concentrations, Prairies and northern Ontario, 1997 to 2011

Nitrogen dioxide concentrations, Prairies and northern Ontario, 1997 to 2011

View data for this chart
How this indicator was calculated

Note: For the Prairies and northern Ontario, the NO2 indicator is based on the annual average of the daily concentrations recorded at 15 monitoring stations. A trend line is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2013) National Air Pollution Surveillance (NAPS) program.

British Columbia

In British Columbia, the annual average concentration of nitrogen dioxide (NO2) in the air for 2011 was 10.5 parts per billion (ppb), or 3% higher than in 2010. A declining trend was detected from 1997 to 2011, representing a decrease of 37% over that period. This decrease is mostly attributable to the reduction in nitrogen oxide (NOx) emissions from cars and trucks, as a result of more stringent emissions standards.

Nitrogen dioxide concentrations, British Columbia, 1997 to 2011

Nitrogen dioxide concentrations, British Columbia, 1997 to 2011

View data for this chart
How this indicator was calculated

Note: For British Columbia, the NO2 indicator is based on the annual average of the daily concentrations recorded at 21 monitoring stations. A trend line is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2013) National Air Pollution Surveillance (NAPS) program.

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Ambient levels of nitrogen dioxide at monitoring stations

The National Air Pollution Surveillance (NAPS) program measures air pollutant concentrations at monitoring stations across Canada. The Canadian Environmental Sustainability Indicators (CESI) provide this information through an interactive indicator map. With the CESI interactive map, you can drill down to nitrogen dioxide (NO2) concentrations at specific monitoring stations.

Related indicators

Other information

Footnotes

Footnote 1

NO2 is not directly measured by the monitors. The NO2 indicator is estimated by subtracting the NO measured concentration from the NOx measured concentration.

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Footnote 2

Three stations or more are required to estimate the regional ambient levels indicators. The Atlantic Canada region had only 2 stations and was not included in the indicators.

Return to footnote 2 referrer