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 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 Matter 2.5 (PM2.5), which has significant health implications.
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.