Criteria Air Contaminants

According to Environment Canada, Criteria Air Contaminants (CAC) are emissions of various air pollutants that affect our health and contribute to air pollution problems such as ground level ozone, haze, and acid rain. CAC are tracked by Environment Canada to measure the effectiveness of emission reduction programs and to supporting scientific research.

Criteria Air Contaminants include:

• Sulphur Oxides (SOx); 
• Nitrogen Oxides (NOx); 
• Particulate Matter (PM);
• Volatile Organic Compounds (VOC); 
• Carbon Monoxide (CO); and, 
• Ammonia (NH3)¹
  

In Europe, where propane-powered vehicles are available direct from the manufacturer, thorough testing has been conducted on a number of these criteria air contaminants.
In a report compiled by the Alternative Fuels Group of the Cleaner Vehicles Task Force - a group comprised of industry members that have an interest in road transport issues – the following was found:

• All of the regulated emissions are reduced for LPG operation when compared to conventional fuels. 
• For light-duty vehicles, NOx is reduced by over 30% (as compared to gasoline). 
• For light-duty vehicles, CO is reduced by over 20% (as compared to gasoline). 
• For heavy-duty engines, CO is reduced by over 90% (compared to diesel). 
• For heavy-duty engines, NOx is reduced by about 60% (compared to diesel). 
• Particulate matter (PMs) is virtually eliminated from LPG vehicle emissions.²

Additional information about Criteria Air Contaminants that relates to propane is listed below:

Nitrogen Oxides (NOx)
NOx are a group of gases containing both nitrogen and oxygen that are released into the air through vehicle exhaust. NOx is a possible carcinogen. It can irritate the eyes, nose, throat, and lungs. Inhalation of high levels of nitrogen oxides can cause swelling of tissues in the throat and upper respiratory tract, reduced oxygenation of body tissues, a build-up of fluid in the lungs, and death.³ When NOx along with volatile organic compounds (VOCs) are exposed to sunlight and heat, it leads to the formation of ground-level ozone which is a primary component of smog. Ozone is harmful to human health and can cause respiratory problems, decreased lung function and, with repeated exposure, permanent lung damage.

According to the Alternative Fuel Vehicle Institute, propane powered vehicles emit 50% less NOx than gasoline powered vehicles.⁴

Particulate matter (PM)
PM relating to vehicles are solid and liquid airborne particles emitted from automobile exhaust. PM can contain soot, soil, dust, chemicals and acids. PM contributes to regional haze and has been linked to aggravated cardiac and respiratory diseases such as asthma, bronchitis and emphysema and to various forms of heart disease.⁵

In a study published by the World LP Gas Association, diesel vehicles produced 30 times more PM than propane powered vehicles.⁶

The California government’s Office of Environmental Health Hazard Assessment (OEHHA) reports that long-term exposure to diesel exhaust particles poses the highest cancer risk of any toxic air contaminant.⁷

In a report compiled by the Argonne National Laboratory (ANL),three studies were combined to determine the effects of propane on Light-Duty Vehicle emissions. Converted propane vehicles were found to emit 80% less Particulate Matter (PM) than the reformulated gasoline Light-Duty Vehicles.⁸

Carbon Monoxide (CO)
CO is a colorless, odorless, tasteless and poisonous gas that is a product of incomplete combustion of hydrocarbon-based fuels and is emitted directly from automobile tailpipes. CO enters the bloodstream through the lungs and forms carboxyhemoglobin, a compound that inhibits the blood's capacity to carry oxygen to organs and tissues. Persons with heart disease, respiratory diseases, children and the elderly are especially sensitive to CO poisoning. CO can affect healthy individuals, impairing exercise capacity, visual perception, manual dexterity, learning functions, and ability to perform complex tasks.⁹

In a report compiled by the Argonne National Laboratory (ANL), three studies were combined to determine the effects of propane on Light-Duty Vehicle (LDV) emissions. Converted propane vehicles were found to emit 20-40% less Carbon Monoxide (CO) than the reformulated gasoline Light-Duty Vehicles.¹⁰

Transportation fuels also emit harmful toxic substances, learn more...

¹ Source: Environment Canada, Clean Air Online, Criteria Air Contaminants and Related Pollutants, http://www.ec.gc.ca/cleanair-airpur/Criteria_Air_Contaminants-Ws7C43740B-1_En.htm
² Source: The Report of the Alternative Fuels Group of the Cleaner Vehicles Task Force, An assessment of the Emissions Performance of Alternative and Conventional Fuels, January 2000
³ Source: CDC ATSDR http://www.atsdr.cdc.gov/tfacts175.html
⁴ Source: AFVI http://www.afvi.org/propane.html
⁵ Source: Environment Canada Clean Air Online Criteria Air Contaminants and Related Pollutants http://www.ec.gc.ca/cleanair-airpur/Pollutants/Criteria_Air_Contaminants_and_Related_Pollutants-WS7C43740B-0_En.htm
⁶ Source: World LP Gas Association – LP Gas and Climate Change: Targeting the Switch to Cleaner Fuels, Executive Summary
⁷ Source: Government of California, Cal/EPA's Office of Environmental Health Hazard Assessment and the American Lung Association http://www.oehha.org/public_info/facts/dieselfacts.html
⁸ Source: A Full Fuel-Cycle Analysis of Energy Emissions Impacts of Transportation Fuels Produced from Natural Gas
⁹ Source: Environment Canada Clean Air Online Criteria Air Contaminants and Related Pollutants http://www.ec.gc.ca/cleanair-airpur/Pollutants/Criteria_Air_Contaminants_and_Related_Pollutants-WS7C43740B-0_En.htm
¹⁰ Source: ANL A Full Fuel-Cycle Analysis of Energy Emissions Impacts of Transportation Fuels Produced from Natural Gas

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