Types of Pollutants

Ground Level Ozone

Ozone (O3) is a gas composed of three atoms of Oxygen. In the upper atmosphere, it occurs naturally and forms a protective layer that shields us from harmful ultraviolet rays produced by the sun (the “Ozone Layer”). Ozone does not occur naturally near the ground. At ground level, it is produced when pollutants from car exhaust, power plants, industry, and other sources react with sunlight. This Ground Level Ozone can affect human health in several ways, including reduction in lung function, irritation of lung tissues, and aggravation of chronic lung conditions such as asthma and emphysema.

Sulphur Oxides

Sulphur Dioxide (SO2), is part of a group of gases known as Sulphur Oxides (SOX). It comes from industry emissions, transportation, natural gas plants, and other sources. In the atmosphere, SO2 can interact with other gases and particles and form sulphates (particles), or water vapour to form acids. SO2, sulphates, and acids can negatively affect both human health and the environment. Sulphates also contribute to Particulate Matter2.5 (PM2.5), which has significant health implications.

Nitrogen Oxides

Nitrogen Oxides (NOX) are very similar to Sulphur Oxides. They mostly come from combustion sources such as vehicle emissions, natural gas plants, and fossil-fueled electric power plants. Nitrogen Dioxide (NO2) also forms acids (HNO3) when dissolved in water vapour, and nitrates when it interacts with other gases and particles. HNO3 and nitrates are harmful to human respiratory systems as well as the environment. Nitrates also lead to increases in PM2.5, and contribute to the formation of Ground Level Ozone.

Particulate Matter

Particulate Matter (PM) is airborne particles, solid or liquid, and may be classified as primary or secondary. Primary PM is emitted from a source already in particle form, and secondary PM is formed as a result of chemical reactions from precursor gases (SO2 and NO2). In addition, PM is further classified according to the size of the particles. PM10includes particles less than 10 microns (µm) in diameter (there are 1000 microns in a millimeter). PM2.5 includes particles less than 2.5 µm in diameter. PM sources are extremely varied; smoke from fires (including residential wood-burning), vehicle emissions, industry, construction, unpaved roads (dust), and agriculture all contribute. PM, especially PM2.5, has been linked to aggravation of chronic lung diseases such as bronchitis, asthma, and emphysema, as well as heart disease. As research continues, it appears to have an even greater impact than previously thought. PM is also a major factor in smog formation and visibility issues.

Carbon Monoxide

Carbon Monoxide (CO) is a gas produced when hydrocarbon-based fuels (wood and petroleum products) are burned. It is colorless, odorless, and toxic. It mainly comes from transportation sources (on- and off-road vehicles), the wood industry, and residential wood burning. In people, CO interferes with the blood’s ability to carry oxygen. While people with compromised heart function, infants, and the elderly are particularly sensitive, CO can also affect healthy people. CO poisoning is characterized by an impairment of several functions, including vision, manual dexterity, mental ability, and physical ability.