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). The major sources of NOX 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 deposition and eutrophication. 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 2012 was 9.4 parts per billion (ppb), or 5% lower than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 41% (or an average decrease of 2.9% per year) 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, 1998 to 2012

Nitrogen dioxide concentrations, Canada, 1998 to 2012

Long Description

The line chart shows the average concentration of nitrogen dioxide in the air in Canada from 1998 to 2012. In 2012, the annual average concentration of nitrogen dioxide in the air was 9.4 parts per billion, or 5 percent lower than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 41 percent (or an average decrease of 2.9 percent per year) over that period.

View data for this chart
How this indicator was calculated

Note: The national NO2 indicator is based on the annual average of the daily concentrations recorded at 77 monitoring stations across Canada. A trend line is displayed and a trend is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2014) National Air Pollution Surveillance program (NAPS).

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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 2012 was 9.3 parts per billion (ppb), 10% lower than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 41% (or an average of 2.9% per year) 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, 1998 to 2012

Nitrogen dioxide concentrations, southern Quebec, 1998 to 2012

Long Description

The line chart shows the average concentration of nitrogen dioxide in the air in southern Quebec from 1998 to 2012. In 2012, the annual average concentration for nitrogen dioxide in outdoor air was 9.3 parts per billion, 10 percent lower than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 41 percent (or an average decrease of 2.9 percent per year) over that period.

View data for this chart
How this indicator was calculated

Note: For southern Quebec, the NO2 indicator is based on the annual average of the daily concentrations recorded at 15 monitoring stations. A trend line is displayed and a trend is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2014) National Air Pollution Surveillance program (NAPS).

Southern Ontario

In southern Ontario, the annual average concentration of nitrogen dioxide (NO2) in the air for 2012 was 9.5 parts per billion (ppb), or 10% lower than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 52% (or an average decrease of 3.7% per year) 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, and from emission reduction measures implemented for power plants.

Nitrogen dioxide concentrations, southern Ontario, 1998 to 2012

Nitrogen dioxide concentrations, southern Ontario, 1998 to 2012

Long Description

The line chart shows the average concentration of nitrogen dioxide in the air in southern Ontario from 1998 to 2012. In 2012, the annual average concentration of nitrogen dioxide in the air was 9.5 parts per billion, or 10 percent lower than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 52 percent (or an average decrease of 3.7 percent per year) over that period.

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 17 monitoring stations. A trend line is displayed and a trend is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2014) National Air Pollution Surveillance program (NAPS).

Prairies and northern Ontario

In the Prairies and northern Ontario, the annual average concentration of nitrogen dioxide (NO2) in the air for 2012 was 8.3 parts per billion (ppb), or 6% lower than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 34% (or an average decrease of 2.4% per year) 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, 1998 to 2012

Nitrogen dioxide concentrations, Prairies and northern Ontario, 1998 to 2012

Long Description

The line chart shows the average concentration of nitrogen dioxide in the air in the Prairies and northern Ontario from 1998 to 2012. In 2012, the annual average concentration of nitrogen dioxide in the air was 8.3 parts per billion, or 6 percent lower than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 34 percent (or an average decrease of 2.4 percent per year) over that period.

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 20 monitoring stations. A trend line is displayed and a trend is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2014) National Air Pollution Surveillance program (NAPS).

British Columbia

In British Columbia, the annual average concentration of nitrogen dioxide (NO2) in the air for 2012 was 10.7 parts per billion (ppb), or 6% higher than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 35% (or an average decrease of 2.5% per year) 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, 1998 to 2012

Nitrogen dioxide concentrations, British Columbia, 1998 to 2012

Long Description

The line chart shows the average concentration of nitrogen dioxide in the air in British Columbia from 1998 to 2012. In 2012, the annual average concentration of nitrogen dioxide in the air was 10.7 parts per billion, or 6 percent higher than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 35 percent (or an average decrease of 2.5 percent per year) over that period.

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 22 monitoring stations. A trend line is displayed and a trend is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2014) National Air Pollution Surveillance program (NAPS).

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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.

Return to footnote 1 referrer

Footnote 2

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

Return to footnote 2 referrer