Vehicles are a major source of air pollution in Ontario. Traffic-related air pollution is emitted from vehicle exhausts, fuel evaporation, and non-tailpipe sources such as brakes, tires and road dust. Elevated levels of traffic-related air pollution can be found up to 250 meters from a major road.

Exposure to traffic-related air pollutants has been linked to a wide range of adverse health outcomes, including respiratory and cardiovascular diseases, cancer, adverse birth and developmental outcomes, and premature mortality. Children, seniors, and people with pre-existing health conditions are more vulnerable to the adverse health effects from traffic-related pollution.

In 2015, Ontario, in collaboration with Environment and Climate Change Canada, established a dedicated roadside air monitoring network, the first of its kind in Canada, to better understand traffic-related air pollution in highly urbanized settings.  These three dedicated roadside air monitoring stations monitor common air pollutants as well as the traffic-related pollutants such as NO2, PM2.5, ultrafine particles, black carbon, metals and major components of PM2.5. The ministry has also designated 10 of its AQHI stations located near major roads as roadside air monitoring stations to complement the roadside air monitoring network.

Roadside air monitoring stations

This is a map depicting the three dedicated and ten AQHI roadside air monitoring stations across Ontario that were in operation during 2022.

Note:

  • Roadside air monitoring stations are located typically within approximately 100 m of a major roadway with daily traffic volumes greater than 10,000 vehicles per day.

Nitrogen dioxide

Combustion or burning of carbon-based materials (e.g., wood, gasoline) in air produces nitrogen oxides (NOx), of which NO2 is a component. The transportation sector is the main source of nitrogen dioxide in Ontario.

Highlights

7-year trends

  • NO2 concentrations across the roadside air monitoring network have decreased by 15%.

2022 results

  • No exceedances of Ontario’s 1-hour and 24-hour Ambient Air Quality Criteria (AAQC) of 200 ppb and 100 ppb, respectively.

7-year trends

Trend of NO2 annual means across the roadside air monitoring network, 2016-2022

This is a line graph showing the trend of NO2 annual mean concentrations across the roadside air monitoring network from 2016 to 2022. The NO2 annual mean concentrations decreased by 15% over this 7-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

  • The 7-year trend is based on data from 12 roadside air monitoring stations.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

The 7-year trend for NO2 at individual roadside air monitoring stations in Ontario is presented in the Appendix: 7-year trend for nitrogen dioxide.

2022 results

Summary of NO2 results for 2022 at roadside air monitoring stations
Averaging timeLow rangeHigh rangeNumber of sites with AAQC exceedances
NO2 
1-hour max		40.7 ppb 
at North Bay		75.6 ppb 
at Toronto Downtown		0
NO2 
24-hour max		20.5 ppb 
at North Bay		40.4 ppb 
at Toronto Hwy 401		0
NO2 
annual mean		4.1 ppb 
at North Bay		17.8 ppb 
at Toronto Hwy 401		Not applicable

A summary of the 2022 NO2 annual statistics for individual roadside air monitoring stations is detailed in the Appendix: 2022 nitrogen dioxide (NO2) annual statistics for the roadside air monitoring network.

Fine particulate matter

Fine particulate matter consists of primary and secondary PM2.5. Primary PM2.5 is emitted directly to the atmosphere. Major sources of primary PM2.5 include residential fireplaces and wood stoves, motor vehicles, smelters, power plants, industrial facilities, and agricultural burning and wildfires. Secondary PM2.5 is formed indirectly in the atmosphere through a series of complex chemical reactions of gaseous precursors such as nitrogen dioxide and sulphur dioxide.

Highlights

7-year trends

  • No trend in PM2.5 concentrations across the roadside air monitoring network

2022 results

  • 10 roadside air monitoring stations measured above the 24-hour reference level of 27 µg/m3 on at least one occasion.
  • 2 roadside air monitoring station measured above the annual reference level of 8.8 µg/m3.

7-year trends

Trend of PM2.5 annual means across the roadside air monitoring network, 2016-2022

This is a line graph showing the trend of PM2.5 annual mean concentrations across the roadside air monitoring network from 2016 to 2022. There was no trend over this 7-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

  • The 7-year trend is based on data from 12 roadside air monitoring stations.
  • Ontario uses the annual PM2.5 CAAQS “as is” for comparison to a single annual average of air quality data; this value, 8.8 µg/m3, is considered a Reference Level.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

The 7-year trend for PM2.5 at individual roadside air monitoring stations in Ontario is presented in the Appendix: 7-year trend for fine particulate matter.

2022 results

Summary PM2.5 results for 2022
Averaging timeLow rangeHigh rangeNumber of sites with AAQC exceedances
PM2.5 
1-hour max		30 µg/m3 
at Thunder Bay		90 µg/m3 
at Hamilton Downtown		Not applicable
PM2.5 
24-hour max		15.8 µg/m3 
at North Bay		39.4 µg/m3 
at Toronto Hwy 401		10
PM2.5 
annual mean		5.03 µg/m3 
at Thunder Bay		9.09 µg/m3 
at Toronto Hwy 401		1

A summary of the 2022 PM2.5 annual statistics for individual roadside air monitoring stations is detailed in the Appendix: 2022 fine particulate matter (PM2.5) annual statistics for the roadside air monitoring network.

Ultrafine particles

Ultrafine particles are less than 0.1 µm in aerodynamic diameter and are mostly emitted from road traffic in urban environments. These tiny particles have larger surface areas per unit mass to absorb toxic chemicals and can also penetrate deep into the lungs.

Highlights

7-year trends

  • No trend in ultrafine particles

2022 results

  • There is no AAQC for ultrafine particles.

7-year trends

Trend of ultrafine particles annual means across the roadside air monitoring network, 2016-2022

This is a line graph showing the trend of ultrafine particles annual mean concentrations from 2016 to 2022. There was no trend for the roadside air monitoring network over this 7-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

  • The 7-year trend is based on data from three roadside air monitoring stations.
  • Ontario does not have an annual AAQC for ultrafine particles.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

The 7-year trend for ultrafine particles at individual roadside air monitoring stations in Ontario is presented in the Appendix: 7-year trend for ultrafine particles.

2022 results

Summary of ultrafine particles results for 2022
Averaging timeLow rangeHigh rangeNumber of sites with AAQC exceedances
Ultrafine particles
1-hour max		65,460 particles/cm3 
at Toronto Island		236,400 particles/cm3 
at Toronto Hwy 401		Not applicable
Ultrafine particles
24-hour max		24,705 particles/cm3 
at Toronto North		145,390 particles/cm3 
at Toronto Hwy 401		Not applicable

A summary of the 2022 ultrafine particles annual statistics for individual roadside air monitoring stations is detailed in the Appendix: 2022 ultrafine particles annual statistics.

Black carbon

Black carbon is a sooty black material produced through incomplete combustion processes. It is emitted from anthropogenic (e.g., engines and coal-fired power plants) and natural sources (e.g., wildfires). Black carbon comprises a significant portion of fine particulate matter and is linked to both climate warming and adverse health effects.

Highlights

7-year trends

  • Black carbon concentrations have decreased by 30%

2022 results

  • There is no AAQC for black carbon.

7-year trends

Trend of black carbon annual means across the roadside air monitoring network, 2016-2022

This is a line graph showing the trend of black carbon annual mean concentrations from 2016 to 2022 across the roadside air monitoring network. The black carbon annual mean concentrations within the network have decreased by 30% over this 7-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

  • The 7-year trend is based on data from 8 roadside air monitoring stations.
  • Ontario does not have an annual AAQC for black carbon.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

The 7-year trend for black carbon at individual roadside air monitoring stations in Ontario is presented in the Appendix: 7-year trend for black carbon.

2022 results

Summary of black carbon results for 2021
Averaging timeLow rangeHigh rangeNumber of sites with AAQC exceedances
Black carbon
1-hour max		3.52 µg/m3 
at Hamilton Downtown		6.48 µg/m3 
at Toronto Hwy 401		Not applicable
Black carbon
24-hour max		1.21 µg/m3 
at Toronto Island		3.10 µg/m3 at 
Toronto Hwy 401		Not applicable

A summary of the 2022 black carbon annual statistics for individual roadside air monitoring stations is detailed in the Appendix: 2022 black carbon annual statistics.

Heavy metals in PM2.5

Heavy metals are a loose term used to refer to naturally occurring trace elements, including metals that reside lower in the Periodic Table of Elements. In PM2.5, they are often associated with industrial processes, vehicle emissions, and various human activities. When inhaled, these airborne particles can accumulate in the body over time and have adverse health effects, particularly when exposure levels are high or prolonged. The ministry measures 24 heavy metals in PM2.5 footnote 1 , of which six select metals are presented below since they are often measured above their respective detection limits.

Highlights

7-year trends

  • No trend for iron in ambient air.
  • Ambient copper concentrations have decreased by 22%.
  • Ambient manganese concentrations have decreased by 24%.
  • Ambient lead concentrations have decreased by 14%.
  • Ambient selenium concentrations have increased by 25%.
  • Ambient zinc concentrations decreased by 37%.

2022 results

  • No exceedances of the 24-hour AAQC for manganese in PM2.5.
  • There are no AAQC for iron, copper, lead, selenium and zinc in PM2.5.

7-year trends

Trend of iron in PM2.5 annual means across the roadside air monitoring network, 2016-2022

This is a line graph showing the trend of iron in PM2.5 annual mean concentrations from 2016 to 2022 across the roadside air monitoring network. There was no trend over this 7-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

  • The 7-year trend is based on data from 2 roadside air monitoring stations.
  • Ontario does not have an annual AAQC for iron in PM2.5.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

Trend of copper in PM2.5 annual means across the roadside air monitoring network, 2016-2022

This is a line graph showing the trend of copper in PM2.5 annual mean concentrations from 2016 to 2022 across the roadside air monitoring network. Copper in PM2.5 annual mean concentrations decreased by 22% over this 7-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

  • The 7-year trend is based on data from 2 roadside air monitoring stations.
  • Ontario does not have an annual AAQC for copper in PM2.5.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

Trend of manganese in PM2.5 annual means across the roadside air monitoring network, 2016-2022

This is a line graph showing the trend of manganese in PM2.5 annual mean concentrations from 2016 to 2022 across the roadside air monitoring network. Manganese in PM2.5 annual mean concentrations decreased by 24% over this 7-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

  • The 7-year trend is based on data from 2 roadside air monitoring stations.
  • Ontario does not have an annual AAQC for manganese in PM2.5.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.   

Trend of lead in PM2.5 annual means across the roadside air monitoring network, 2016-2022

This is a line graph showing the trend of lead in PM2.5 annual mean concentrations from 2016 to 2022 across the roadside air monitoring network. Lead in PM2.5 annual mean concentrations decreased by 14% over this 7-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

  • The 7-year trend is based on data from 2 roadside air monitoring stations.
  • Ontario does not have an annual AAQC for lead in PM2.5.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

Trend of selenium in PM2.5 annual means across the roadside air monitoring network, 2016-2022

This is a line graph showing the trend of selenium in PM2.5 annual mean concentrations from 2016 to 2022 across the roadside air monitoring network. Selenium in PM2.5 annual mean concentrations increased by 25% over this 7-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

  • The 7-year trend is based on data from 2 roadside air monitoring stations.
  • Ontario does not have an annual AAQC for selenium in PM2.5.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

Trend of zinc in PM2.5 annual means across the roadside air monitoring network, 2016-2022

This is a line graph showing the trend of zinc in PM2.5 annual mean concentrations from 2016 to 2022 across the roadside air monitoring network. Zinc in PM2.5 annual mean concentrations decreased by 37% over this 7-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

  • The 7-year trend is based on data from 2 roadside research air monitoring stations.
  • Ontario does not have an annual AAQC for zinc in PM2.5.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

The 7-year trend for heavy metals at individual roadside air monitoring stations in Ontario is presented in the Appendix: 7-year trend for iron in PM2.5; 7-year trend for copper in PM2.5; 7-year trend for manganese in PM2.5; 7-year trend for lead in PM2.5; 7-year trend for selenium in PM2.5; 7-year trend for zinc in PM2.5.

2022 results

Summary of heavy metals in PM2.5 results for 2022
Averaging timeLow rangeHigh rangeNumber of sites with AAQC exceedances
Iron in PM2.5 
1-hour max		4,909.5 ng/m3 
at Hamilton Downtown		5,874.0 ng/m3 
at Toronto Hwy 401		Not applicable
Iron in PM2.5 
24-hour max		737.0 ng/m3 
at Hamilton Downtown		1,020.6 ng/m3 
at Toronto Hwy 401		Not applicable
Copper in PM2.5 
1-hour max		216.7 ng/m3 
at Hamilton Downtown		603.7 ng/m3 
at Toronto Hwy 401		Not applicable
Copper in PM2.5 
24-hour max		36.6 ng/m3 
at Hamilton Downtown		45.6 ng/m3 
at Toronto Hwy 401		Not applicable
Manganese in PM2.5 
1-hour max		94.3 ng/m3 
at Toronto Hwy 401		608.0 ng/m3 
at Hamilton Downtown		Not applicable
Manganese in PM2.5 
24-hour max		14.1 ng/m3 
at Toronto Hwy 401		41.2 ng/m3 
at Hamilton Downtown		0
Lead in PM2.5 
1-hour max		151.1 ng/m3 
at Hamilton Downtown		197.7 ng/m3 
at Toronto Hwy 401		Not applicable
Lead in PM2.5 
24-hour max		20.8 ng/m3 
at Hamilton Downtown		22.3 ng/m3 
at Toronto Hwy 401		Not applicable
Selenium in PM2.5 
1-hour max		13.57 ng/m3 
at Hamilton Downtown		61.62 ng/m3 
at Toronto Hwy 401		Not applicable
Selenium in PM2.5 
24-hour max		4.35 ng/m3 
at Hamilton Downtown		10.46 ng/m3 
at Toronto Hwy 401		Not applicable
Zinc in PM2.5 
1-hour max		1,031.0 ng/m3 
at Hamilton Downtown		3,637.9 ng/m3 
at Toronto Hwy 401		Not applicable
Zinc in PM2.5 
24-hour max		173.4 ng/m3 
at Toronto Island		347.5 ng/m3 
at Toronto Hwy 401		Not applicable

A summary of the 2022 heavy metals in PM2.5 annual statistics for individual roadside air monitoring stations is detailed in the Appendix: 2022 iron in PM2.5 annual statistics; 2022 copper in PM2.5 annual statistics; 2022 manganese in PM2.5 annual statistics; 2022 lead in PM2.5 annual statistics; 2022 selenium in PM2.5 annual statistics; and 2022 zinc in PM2.5 annual statistics.

Major components in PM2.5

Major components in PM2.5, with the exception of black carbon and metals, are the parts of tiny particles that can change or evaporate when exposed to heat (also known as non-refractory species in PM2.5).  In the air, these include organic compounds, sulphate, nitrate and ammonium compounds. Vehicle emissions and industry are major sources of these components which can affect human health.

The ministry measures five major components in PM2.5, of which four components are presented since chloride is mostly below its detection limit.

Highlights

7-year trends

  • No trend for organics in PM2.5
  • Sulphate in PM2.5 has decreased 34%
  • Nitrate in PM2.5 has decreased 36%
  • Ammonium in PM2.5 has decreased 27%

2022 results

  • There are no AAQC for major components in PM2.5, such as, organics, sulphate, nitrate and ammonium.

7-year trends

Trend of organics in PM2.5 at Toronto Hwy 401, 2016-2022

This is a line graph showing the trend of organics in PM2.5 annual mean concentrations from 2016 to 2022 at the Toronto Hwy 401 roadside air monitoring station. There was no trend over this 7-year period.

Note:

  • Ontario does not have an annual AAQC for organics in PM2.5.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

Trend of sulphate in PM2.5 at Toronto Hwy 401, 2016-2022

This is a line graph showing the trend of sulphate in PM2.5 annual mean concentrations from 2016 to 2022 at the Toronto Hwy 401 roadside air monitoring station. Sulphate in PM2.5 annual mean concentrations decreased by 34% over this 7-year period.

Note:

  • Ontario does not have an annual AAQC for sulphate in PM2.5.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

Trend of nitrate in PM2.5 at Toronto Hwy 401, 2016-2022

This is a line graph showing the trend of nitrate in PM2.5 annual mean concentrations from 2016 to 2022 at the Toronto Hwy 401 roadside air monitoring station. Nitrate in PM2.5 annual mean concentrations decreased by 36% over this 7-year period.

Note:

  • Ontario does not have an annual AAQC for nitrate in PM2.5.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

Trend of ammonium in PM2.5 at Toronto Hwy 401, 2016-2022

This is a line graph showing the trend of ammonium in PM2.5 annual mean concentrations from 2016 to 2022 at the Toronto Hwy 401 roadside air monitoring station. Ammonium in PM2.5 annual mean concentrations decreased by 27% over this 7-year period.

Note:

  • Ontario does not have an annual AAQC for ammonium in PM2.5.
  • Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes. 

Relative distribution of major components in PM2.5 at Toronto Hwy 401, 2016-2022

This is a stacked column chart showing the relative distribution of major components in PM2.5 based on annual mean concentrations from 2016 to 2022 at the Toronto Hwy 401 roadside air monitoring station. Relative contribution of PM2.5 components varied from year to year with the organic component representing the largest contribution across all years.

The 7-year trends for the four major components in PM2.5 monitored at the Toronto Hwy 401 roadside air monitoring station in Ontario are presented in the Appendix: 7-year trend for organics in PM2.5; 7-year trend for sulphate in PM2.5; 7-year trend for nitrate in PM2.5; 7-year trend for ammonium in PM2.5.

2022 results 

Summary of major components in PM2.5 results for 2022 
at Toronto Hwy 401
Averaging timeConcentrationNumber of sites with AAQC exceedances
Organics in PM2.5 
1-hour max		79.3 µg/m3Not applicable
Organics in PM2.5 
24-hour max		17.31 µg/m3Not applicable
Sulphate in PM2.5 
1-hour max		9.4 µg/m3Not applicable
Sulphate in PM2.5 
24-hour max		3.63 µg/m3Not applicable
Nitrate in PM2.5 
1-hour max		9.5 µg/m3Not applicable
Nitrate in PM2.5 
24-hour max		6.77 µg/m3Not applicable
Ammonium in PM2.5 
1-hour max		32.0 µg/m3Not applicable
Ammonium in PM2.5 
24-hour max		2.67 µg/m3Not applicable

A summary of the 2022 annual statistics for major components in PM2.5 at the Toronto Hwy 401 roadside air monitoring station is detailed in the Appendix: 2022 organics in PM2.5 annual statistics; 2022 sulphate in PM2.5 annual statistics; 2022 nitrate in PM2.5 annual statistics; 2022 ammonium in PM2.5 annual statistics.

Learn more about what Ontario is doing to protect our air.

Footnotes

  • footnote[1] Back to paragraph The number of stations monitoring heavy metals in PM2.5 was reduced from 3 in 2021 to 2 in 2022 due to technical issues at the Etobicoke South air monitoring station.