Airborne Pollutant Overview

What is fine particulate matter?
Particulate matter is the general term used for a mixture of solid particles and liquid droplets in the air. It includes aerosols, smoke, fumes, dust, ash and pollen. Fine particulate matter is particulate matter that is 2.5 microns in diameter and less. It is also known as respirable particulate because it penetrates the respiratory system further than larger particles. The composition of particulate matter varies with place, season and weather conditions. PM_2.5 in Ontario is largely made up of sulphate and nitrate particles, elemental and organic carbon and soil. PM_2.5 is a component of smog.

PM_2.5 is primarily formed from chemical reactions in the atmosphere and through fuel combustion (e.g., motor vehicles, power generation, industrial facilities, residential fire places, wood stoves and agricultural burning). Significant amounts of PM_2.5 are carried into Ontario from the U.S.

Exposure to PM_2.5 has been associated with hospital admissions and several serious health effects, including premature death. People with asthma, cardiovascular or lung disease, as well as children and elderly people, are considered to be the most sensitive to the effects of fine particulate matter. Adverse health effects have been associated with exposure to PM_2.5 over both short periods (such as a day) and longer periods (a year or more).

Air quality standards
24-hour¹ Canadian Ambient Air Quality Standards (CAAQS): 28 µg/m³
Annual² Canadian Ambient Air Quality Standards (CAAQS): 10 µg/m<sup>3

1</sup>Based on the 3-year average of the annual 98^th percentile of the daily 24-hour average concentrations
²Based on the 3-year average of the annual average concentrations

Canadian Ambient Air Quality Standards

Links- more information on particulate matter
Air Quality Ontario – Fine Particulate Matter
Environment and Climate Change Canada - Air - Particulate Matter

What is nitrogen dioxide?
NO₂ is a reddish-brown gas with a pungent and irritating odour. NO₂ is a common combustion product. The main sources are motor vehicles, thermal power generation, metal production, and incineration. NO₂ reacts in the atmosphere to form a number of compounds, some of which have health or environmental effects. It is an ozone precursor, a component of smog and one of the causes of acid rain. NO₂ can lead to lung irritation and lower resistance to respiratory infection.

Air quality standards
MECP 1-hour AAQC (Ambient Air Quality Criteria): 200 ppb or 400 µg/m³
MECP 24-hour AAQC (Ambient Air Quality Criteria): 100 ppb or 200 µg/m³

Ontario's Ambient Air Quality Criteria

Links- more information on NO₂
Air Quality Ontario – Nitrogen Dioxide
Environment and Climate Change Canada - Air - Nitrogen Oxides - NOx

What is ozone?

Ozone (O₃) at ground level is a reactive, inorganic gas with a distinctive pungent odour. It is not emitted directly into the atmosphere; rather, it is formed in the presence of sunlight in reactions between nitrogen oxides (NOx) and volatile organic compounds (VOC). The formation and transport of O₃ is strongly dependent on meteorological conditions. Significant amounts of O₃ and O₃ -forming compounds travel from the United States into Ontario. Strong sunlight and warm conditions speed up production, and so concentrations tend to rise during the day, and fall at night. Year-to-year variations in O₃ concentrations are greatly dependant on wind patterns and weather.

O₃ is a component of smog and can have human health impacts, particularly respiratory tract irritation. It may also adversely affect certain plants.

Air quality standards
MECP 1-hour AAQC (Ambient Air Quality Criteria): 80 ppb or 165 µg/m³

Ontario's Ambient Air Quality Criteria

Links- more information on O₃
Air Quality Ontario – Ozone
Environment and Climate Change Canada - Air – Ground level ozone

What is sulphur dioxide?
Sulphur dioxide (SO₂) is a colourless gas, belonging to the family of gases called sulphur oxides (SO_x). SO₂ smells like burnt matches. Natural sources of sulphur dioxide include releases from forest fires and biological decay. The most important man-made sources of sulphur dioxide are fossil fuel combustion, smelting, manufacture of sulphuric acid, conversion of wood pulp to paper, incineration of refuse and production of elemental sulphur. Coal burning is the single largest man-made source of sulphur dioxide.

SO₂ and nitrogen oxides (NO_x) are the main contributors to acid rain. Health effects caused by exposure to high levels of SO₂ include eye and respiratory tract irritation, and worsening cardiovascular disease. SO₂ can travel a considerable distance downwind in certain meteorological conditions. Short-term exposure to SO₂ may cause respiratory distress, especially in sensitive individuals such as asthmatics.

UPDATED Sulphur Dioxide AAQC: The way SO2 data is categorized has changed

The Ontario Ministry of the Environment Conservation and Parks updated the Ambient Air Quality Criteria (AAQC) for Sulphur Dioxide (SO₂ on March 20, 2018 to be more protective of human health. This change reflects a more up-to-date understanding of the health effects of SO₂.

Because of this change, we have updated how the concentration levels are categorized and displayed for CASA website users. Measurements will still be categorized as good, moderate, poor or very poor to show how they compare with the updated ministry criteria.

Please note that data collected prior to March 20, 2018, when pulled from CASA, will still apply the original measurement categories.

This chart shows how the AAQC categories have changed for data collected before and after March 20, 2018:

SO₂ Categorization

Air quality standards
MECP: 10- minute AAQC (Ambient Air Quality Criteria): 67 ppb (parts per billion) or 178 µg/m³
MECP: 1- hour AAQC (Ambient Air Quality Criteria): 40 ppb (parts per billion) or 106 µg/m³
MECP: Annual AAQC (Ambient Air Quality Criteria): 4 ppb (parts per billion) or 11 µg/m³
Ontario's Ambient Air Quality Criteria

Links- more information on SO₂
Air Quality Ontario – Sulphur Dioxide
Environment and Climate Change Canada - Air - Sulphur Oxides - SOx

What are total reduced sulphur compounds?
Total reduced sulphur (TRS) compounds are a group of sulphur-based compounds including hydrogen sulphide (H₂S) and various mercaptans. TRS compounds have a variety of industrial sources, such as petrochemical facilities and sewage treatment plants, and natural sources, such as swamps and marshes.

TRS compounds at very low concentrations are odorous, produce a rotten egg smell, and are not generally considered a health hazard at these concentrations. At higher concentrations short-term H₂S can cause nausea, headaches, convulsions, skin and eye irritation, and effects on the respiratory system.

Air quality standards
MECP: 10-minute AAQC (Ambient Air Quality Criteria): 8.9 ppb or 13 µg/m³
MECP: 24- hour AAQC (Ambient Air Quality Criteria): 4.8 ppb (parts per billion) or 7 µg/m³

Ontario's Ambient Air Quality Criteria

Links - more information on TRS
Air Quality Ontario – Total Reduced Sulphur Compounds

What are VOC?
Volatile organic compounds (VOC) are organic (carbon-containing) chemicals that exist as a gas at normal environmental temperatures and pressures. VOC are emitted into the atmosphere from a variety of both natural and anthropogenic sources, such as vehicles, fossil fuel combustion, steel making, petroleum refining, fuel refilling, industrial and residential solvent use, paint application, manufacturing of synthetic materials (e.g. plastic, carpets) food processing, agricultural activities, wood processing and wood burning. Certain VOC play a role in the formation of ground-level ozone and PM_2.5, which contribute to smog. Other, less reactive, VOC may be transported long distances in the atmosphere.

VOC may often be odorous and some are linked to various health or environmental impacts. Most VOC are not encountered at levels that are immediately toxic, although they may cause effects on long exposure including an increased risk of cardiovascular and respiratory effects.

Several of the CASA stations monitor one or more VOC on a real-time basis (1,3-butadiene, benzene, and ethylene). These three VOC are described in further detail below.

An even wider range of VOC are monitored at several CASA stations on a non-continuous basis (every 6 or 12 days), or continuously over a 2-week period, which involves collecting a sample that is sent for laboratory analysis. The results of these VOC samples are available on the More Monitoring Data page.

1,3-Butadiene is a chemical made from the processing of petroleum. It is a colourless gas with a mild gasoline-like odour. About 75% of the manufactured 1,3-butadiene is used to make synthetic rubber. Synthetic rubber is widely used for tires on cars and trucks. It is also used to make plastics, including acrylics. Small amounts are found in gasoline. Breathing low levels of 1,3-butadiene may cause irritation of the eyes, nose, and throat. 1,3-butadiene is classified as a known human carcinogen by IARC (the International Agency for Research on Cancer).

The ministry’s AAQC (Ambient Air Quality Criteria) for 1,3-butadiene were derived from cancer risk levels based on continuous lifetime exposure. The AAQC can be converted to 1-hour equivalent values for informational purposes, and as an indicator of whether the longer term AAQC may be exceeded. An exceedance of the 1-hour AAQC equivalent does not mean that cancer risks will increase unless the frequency of the exceedance and the magnitude above the AAQC is experienced over a long term.

Air quality standards
MECP:  24- hour AAQC (Ambient Air Quality Criteria): 4.3 ppb (parts per billion) or 10 µg/m³
MECP:  Annual AAQC (Ambient Air Quality Criteria): 0.8 ppb (parts per billion) or 2 µg/m³

Benzene is a volatile organic compound (VOC) that occurs naturally in crude oil. It is colourless, highly flammable, and has a sweet odour. It is primarily used in the production of plastics and other chemical products, and is a component of gasoline.  The primary sources of human exposure to benzene are motor vehicle exhaust, gasoline service station emissions, industrial emissions, tobacco smoke, and industrial emergencies (such as petroleum spills).  Benzene is classified as a known human carcinogen by IARC (the International Agency for Research on Cancer).

The ministry’s AAQC (Ambient Air Quality Criteria) for benzene was derived from cancer risk levels based on continuous lifetime exposure. The AAQCs can be converted to 1-hour equivalent values for informational purposes, and as an indicator of whether the longer term AAQC may be exceeded. An exceedance of the 1-hour AAQC equivalent does not mean that cancer risks will increase unless the frequency of the exceedance and the magnitude above the AAQC is experienced over a long term.

Air quality standards
MECP:  24- hour AAQC (Ambient Air Quality Criteria): 0.68 ppb (parts per billion) or 2.3 µg/m³
MECP:  Annual AAQC (Ambient Air Quality Criteria): 0.13 ppb (parts per billion) or 0.45 µg/m³

Ethylene (also known as ethene) is a colourless gas with a mild sweet and musky odour. It is used in the chemical industry for the manufacturing of plastics and many other chemical products. It is also a naturally occurring plant hormone, and is used in agriculture to ripen fruit.  Ethylene emissions can lead to field crop damage. The ministry’s 24-hour AAQC for ethylene is based on vegetation effects.

An exceedance of the 1-hour AAQC equivalent for ethylene does not mean that effects will occur unless the frequency of exceedance and the magnitude above the AAQC is experienced over several (2-3) days.

Air quality standards
MECP:  24- hour AAQC (Ambient Air Quality Criteria): 33 ppb (parts per billion) or 40 µg/m³

Links- more information on VOCs
Environment and Climate Change Canada - Air - Volatile Organic Compounds (VOCs)
Ontario's Ambient Air Quality Criteria

Metals are common constituents of particulate matter. Certain metals may have health or environmental effects. The total suspended particulate samples collected at several stations in the CASA network are analyzed for a variety of metals:

• Cadmium
• Calcium
• Chromium
• Copper
• Iron
• Lead
• Manganese
• Nickel
• Silicon
• Vanadium
• Zinc

Air Quality standards

The MECP has 24-hour AAQC for most of the metals analyzed, as well as annual AAQC for nickel and cadmium.

Ontario's Ambient Air Quality Criteria

What are PAH?
Polycyclic aromatic hydrocarbons (PAH) are a group of complex hydrocarbons formed by incomplete combustion of organic compounds. They are common products of industrial processes and domestic activities, including burning fuel such as coal or wood, and barbecuing. Some PAH, such as benzo[a]pyrene, are known to be carcinogenic.

PAH are found in very low concentrations in the atmosphere, and so concentrations are given in nanograms per cubic metre, a unit that is one thousand times smaller than the units used for most other measurements on the CASA website (that is, parts per billion or micrograms per cubic metre).

The ministry’s AAQC (Ambient Air Quality Criteria) for benzo[a]pyrene was derived from cancer risk levels based on continuous lifetime exposure. The AAQC can be converted to 1-hour equivalent values for informational purposes, and as an indicator of whether the longer term AAQC may be exceeded. An exceedance of the 1-hour AAQC equivalent does not mean that cancer risks will increase unless the frequency of the exceedance and the magnitude above the AAQC is experienced over a long term.

The ministry has AAQC for benzo[a]pyrene (B[a]P), which are listed below.

Air Quality standards

MECP:  24- hour AAQC (Ambient Air Quality Criteria):  0.05 ng/m³
MECP:  Annual AAQC (Ambient Air Quality Criteria):  0.01 ng/m³

Ontario's Ambient Air Quality Criteria

Links- more information on PAH
Environment and Climate Change Canada - Pollution and Waste - Polycyclic Aromatic Hydrocarbons