Air Quality: What causes Air Pollution?

What causes Air Pollution?

Many of the activities we engage in contribute to air pollution. These activities include the burning of fossil fuels to run our cars, heat our homes, generate electricity, or fuel various industries, including the oil and gas industry itself. Other air pollutants come from the burning of wood to heat our homes or clear land, the incineration of garbage, fumes from paints, solvents and petroleum products, and ammonia from livestock wastes and fertilizers.

A visible and common form of air pollution is smog, which is a noxious mixture of gases and particles that often appears as a haze in the air. Smog occurs throughout the year. Summer smog is primarily composed of ground-level ozone and fine particulate matter (PM2.5). Winter smog occurs when stagnant air causes a buildup of pollutants, mainly fine particulate matter, in the air.

Ground-level ozone is formed when two other pollutants, nitrogen oxides (NOx) and volatile organic compounds (VOC), are exposed to sunlight and heat. The oil and gas industry is the largest emitter of VOC. Other important sources of VOC emissions include the evaporation of paints and solvents; off-road vehicle use; road, rail, air and marine transportation; home firewood burning and other activities. Emissions of NOx are led by transportation (road, air, rail and marine), followed by the oil and gas industry, off-road vehicle use and other activities.

The largest percentage of PM2.5 emitted directly into the atmosphere comes from home firewood burning, followed by emissions from industries and from off-road vehicle use. Other pollutants include VOC, NOx, sulphur oxides (SOx), and ammonia (NH3), which interact in the atmosphere to form PM2.5.

There is not always a direct relationship between the levels of air emissions and the level of smog. This can be due in part to air pollutants moving in from other areas or from chemical interactions between the airborne pollutants. Also, weather conditions such as warm sunny days can increase smog formation. And sometimes a decrease in one pollutant can actually lead to an increase in another. For example, ground-level ozone combines with nitrogen oxides resulting in less ground-level ozone through a process called “ozone scavenging.” In some parts of Canada lower levels of nitrogen oxides have actually resulted in less ozone scavenging and thus higher ambient levels of ground-level ozone.

Courtesy Environment Canada