Where does Pollution Come From?


Where does Pollution Come From?
There are many different sources of air pollution in Ontario. Primary pollutants are emitted directly into the atmosphere by both industrial and residential sources. They include SO2, NOx, VOCs, particles, CO, toxics and metals. Secondary pollutants, such as ozone and sulphates, are generated in the atmosphere from primary pollutants.
The following is a brief description of the major primary pollutants and their sources.
Sulphur Dioxide (SO2)
Most fossil fuels and some ores contain sulphur. When they are burned, SO2 is released into the air. Approximately 15% of the electricity in Ontario is generated by burning coal, releasing large amounts of SO2. Copper and nickel smelters account for nearly a third of all SO2 in Canada.
Nitrogen Oxides (NOx)
NOx is emitted from the combustion of fuel. Transportation contributes over 65% of Ontario’s NOx emissions. The small number of heavy-duty diesel vehicles produce about the same amount of NOx as all of the automobiles on the road. Coal-burning power plants and natural gas processing release 20% of Canada’s NOx.
Volatile Organic Compounds (VOCs)
VOCs are carbon chemicals that evaporate easily. Approximately half of the VOCs found in Canada are from natural sources, such as trees. Gasoline powered vehicles account for over 40% of human-made VOC emissions in Canada, including both combustion emissions and VOC evaporation from gas tanks and filling station spillage. These, along with the use of general solvents such paints and cleaners, are the major emitters of VOCs.
Suspended Particles (TSP, PM10)
Particles are released directly into the air during the combustion of fossil fuel. Of particular health concern are emissions from diesel engines and cement plants because these particles are small enough to be inhaled directly into the lungs (PM10). Other major sources of particles include:
    • Coal-Burning Power Plants
    • Mining Operations
    • Residential Wood Combustion
  • Dust Emissions from Fields and Roads
Carbon Monoxide (CO)
CO results from the incomplete combustion of fossil fuels. Over half of the CO emissions in Canada are from gasoline powered automobiles. All forms of transportation produce over 70% of Canadian emissions.
In the air pollution field, “air toxics” are known or suspected to cause cancer or development abnormalities. Waste incineration produces a wide range of air toxics such as dioxins, furans and benzene. Although where was a ban on new municipal waste incinerators, it has now been lifted and several are in operation in Ontario.
Many industrial processes generate airborne metal particles such as arsenic, chromium and lead. Major emitters are metal smelters and battery manufacturers. Lead levels have fallen by over ninety per cent since the introduction of unleaded gasoline in 1975.
Major Sources are: Power Plants, Transportation, Industry
Primary Pollutants
Primary pollutants are emitted directly into the atmosphere. They include SO2, NOx, VOCs, particles, and toxics. Secondary pollutants are formed when primary pollutants are formed when primary pollutants react with each other and atmospheric elements. The only way to control the levels of secondary pollutants is through limiting the amount of primary pollutants released. For example, NOx and VOCs react in the presence of sunlight to produce ground level ozone. In Ontario, the Smog Management Plan focuses on the reduction of NOx and VOCs to control ozone.
Secondary Pollutants
Secondary pollutants of concern (in addition to ozone) include sulphates and other fine particles (PM10). IN most cases, larger particles are emitted directly into the air and fine particles form as secondary pollutants. Fine sulphate and nitrate particles are formed when SO2 and Nox emissions react with water. Fine particles are more detrimental to our health because they can penetrate deeper into the lungs that larger particles. We need to consider all of the effects of primary pollutants that we emit. Both primary and secondary pollutants pose serious health concerns.