Outdoor Air Pollution Profile
OTHERS – KNOWN CARCINOGEN (IARC 1)
Outdoor Air Pollution Profile
- A mixture of pollutants formed during various natural and anthropogenic processes
- Associated cancer: Lung cancer
- Main route of exposure: Inhalation
- Primary sources: Transportation, power generation, industrial activity, heating, cooking, fuel or coal combustion, forest fires, volcanoes, and dust storms
- Environmental exposures: Via combustion sources in outdoor air (and infiltration to indoor environments), such as industrial processes, vehicle exhaust, fireplaces, and forest fires
- Fast fact: Particulate matter in outdoor air pollution is classified according to its size; smaller particles can penetrate deeper in airways than larger particles.
Outdoor air pollution is a mixture of gases and particulate matter (a complex mixture of solid particles and liquid droplets). Outdoor air pollutants are formed during natural and anthropogenic processes. The most common anthropogenic sources are transport, power generation, industrial activity, heating, cooking, and fuel or coal combustion. Natural sources include forest fires, volcanoes, and dust storms.
The composition of outdoor air pollutants may vary considerably over time and space due to variations in the pollutants’ sources, as well as changes in weather and atmospheric transformations. Major gaseous pollutants include sulfur dioxide, nitrogen oxides, and carbon monoxide. Major particulate matter components include organic and elemental carbon compounds, metal oxides, lead, and others. The overall composition of outdoor air pollution in an environment is difficult to characterize due to the numerous pollutants that comprise it. However, particulate matter is typically classified according to its size. Suspended particulates tend to be less than 40 µm in diameter. Particulates may be referred to as PM10 (all particles sized 10 µm or less), PM2.5 (all particles sized 2.5 µm or less), or TPM (total particulate matter). Particulates can also be broken down into four main categories:
- Ultra fine – less than 0.1 µm in diameter
- Fine or respirable fraction – less than 2.5 µm in diameter
- Coarse or inhalable fraction – between 2.5 to 10 µm in diameter
- Total suspended particulates (TSP) – particles less than 40 µm in diameter
Each category of particles originates from different sources and interacts uniquely in the environment. For example, ultrafine particles are formed directly in combustion exhaust, mainly as hot vapours are condensed, and can aggregate and coagulate over time to form fine particulates. In contrast, particles in the fine fraction are produced mainly by combustion processes and by atmospheric reactions between precursor gases such as sulphur dioxide, nitrogen oxides, ammonia, and some volatile organic compounds.[3,4]
In 2013, the International Agency for Research on Cancer (IARC) evaluated the carcinogenic effects of outdoor air pollution and particulate matter associated with outdoor air pollution. The IARC assessment focused on pollutants released as a result of anthropogenic activities, especially combustion and industrial processes. IARC classified outdoor air pollution and particulate matter associated with outdoor air pollution as Group 1, carcinogenic to humans. This classification is based on sufficient evidence of an association between exposure and lung cancer in humans, and limited evidence that exposure causes bladder cancer. There was sufficient evidence supporting the carcinogenicity of various components of outdoor air pollutants (whole diesel engine exhaust, diesel engine exhaust particles, extracts of diesel engine exhaust particles, condensates of gasoline engine exhaust, extracts from coal-derived soot and wood smoke, and emissions from combustion of coal and wood) in animal studies. Finally, there was strong mechanistic evidence that outdoor air pollution (and associated particulate matter) has genotoxic effects.
Outdoor air pollution is associated with other health effects including chronic obstructive pulmonary disease, stroke, ischemic heart disease, and acute lower respiratory infection.
Regulations and Guidelines
Occupational Exposure Limits (OEL)
Outdoor air pollution is not regulated as an occupational exposure.
|CEPA||PM10 and PM2.5:
Schedule 1, paragraph ‘c’
|CEPA||Emissions of particulate matter from copper and zinc smelter operations:
Schedule 1, paragraphs ‘a’ and’c’
CEPA = Canadian Environmental Protection Act
Air quality guidelines
|Canadian Jurisdictions||Level of PM10 (µg/m3)||Notes|
|Canadian Reference Level(a)||25||24 hour average|
|BC Air Quality Objective||50||24 hour average|
|ON Ambient Air Quality Criteria(b)||50||24 hour average|
|Canadian Jurisdictions||Level of PM2.5 (µg/m3)||Notes|
|Canadian Reference Level||15||24 hour average|
|Canada-Wide Standard(c)||27||24 hour average|
|Canada-Wide Standard(e)||8.8||Annual average|
|AB Air Quality Objective||80
|1 hour average
24 hour average
|BC Air Quality Objective(d)||25||24 hour average|
|BC Air Quality Objective||8||Annual average|
|BC Planning Goal||6||Annual average|
|ON Air Quality Criteria||27
|24 hour average
|Other Jurisdictions||Level (µg/m3)||Notes|
|US EPA(f)||150||PM10; 24 hour average|
|US EPA(g)||35||PM2.5; 24 hour average|
|US EPA(h)||12.5||PM2.5; annual average|
|WHO||50||PM10; 24 hour average|
|WHO||20||PM10; annual average|
|WHO||25||PM2.5; 24 hour average|
|WHO||10||PM2.5; annual average|
µg/m3 = micrograms per cubic metre
(a) Reference Level is defined as the level above which effects on human health and the environment can be demonstrated
(b) Interim AAQC provided as a guide for decision making
(c) Attainment based on average of 98th percentile ambient measurement over 3 consecutive years
(d) Achievement based on annual 98th percentile value
(e) The 3-year average of the annual average concentrations
US EPA = United States Environmental Protection Agency
(f) Not to be exceeded more than once per year on average over three years
(g) To attain this standard, the 3-year average of the 98th percentile of 24-hour concentrations at each population-oriented monitor within an area must not exceed 35 µg/m3 (effective December 17, 2006)
(h) To attain this standard, the 3-year average of the weighted annual mean PM2.5 concentrations from single or multiple community-oriented monitors must not exceed 15 µg/m3
WHO = World Health Organization
Environmental Exposures Overview
Canadians are exposed to fine and ultrafine particles by breathing outdoor air containing emissions from any combustion source, including industrial processes, gasoline and diesel engine exhausts, fireplaces, furnaces, prescribed burning for forestry and agricultural purposes, and naturally-caused wildfires.
CAREX Canada estimates of potential lifetime excess cancer risk for outdoor air pollution are unavailable at this time. According to the Canadian Population Attributable Risk of Cancer (ComPARe) study, 6.9%, or 1,700 lung cancer cases were due to exposure to PM2.5 in outdoor air in 2015. The study estimates that over 3,000 lung cancer cases could be prevented between 2016 and 2042 if declining trends in PM2.5 continue.
Particulates in outdoor air are monitored by the National Air Pollution Surveillance (NAPS) network. In 2013, the annual average levels of PM2.5 was 7.3 µg/m3, and the annual peak 24-hour concentration was 20 µg/m3. Both of these values remained below the 2015 Canada Wide Standard. Between 1985 and 2012, daily averages for PM10 remained below 10 µg/m3 in 44 of 49 different sites located across Canada. Higher levels of PM10 were found in large urban areas and near roadways.
A search of Environment Canada’s National Pollutant Release Inventory (NPRI) yielded the following results on current potential for exposure to outdoor air pollution in Canada:
NPRI reported releases
|Substance name: ‘PM – Total Particulate Matter’
‘PM10 – Particulate Matter ≤ 10 microns’
‘PM2.5 – Particulate Matter ≤ 2.5 microns’
All amounts released into environment (on-site release)
|PM Type||# of facilities||Quantity||Industry|
|Total PM||1,188||327,251 t||Resource extraction and processing, manufacturing|
t = tonne
For more information, see the environmental exposures tab for outdoor air pollution.
- Environment and Climate Change Canada. National Air Pollution Surveillance (NAPS) Program (2022)
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