OZONE

Ozone (O₃) is a colourless, odourless gas.  O₃ is a very reactive gas that can absorb Ultra Violet (UV) radiation.

Sources

Ozone is present in two different areas of the atmosphere and plays two different roles.
Ozone that is formed naturally in the atmosphere (the "good" ozone) protects life from the sun's damaging ultraviolet rays. At ground level, however, ozone acts as an invisible air pollutant that is harmful to humans, animals, plants and man-made materials.

Ground-level ozone is created when gases such as nitrogen oxides react with volatile organic compounds (VOCs) when they are combined with sunlight and heat. This is why smog is more of a problem on hot summer days. Nitrogen oxides are produced by burning fossil fuels such as coal, oil, gas, and diesel in motor vehicles, industries, power plants and homes. VOCs include carbon-containing gases that are created when gasoline and solvents are burned. Studies show that every major Canadian urban centre has levels of ground-level ozone that are high enough to pose health risks.

Effects on health and the environment

Studies show a wide variety of effects caused from exposure to ozone. In the short term, these include irritation to your eyes, nose and throat, coughing and headaches. Exposure to high levels can result in chest tightness, coughing and wheezing. It also contributes to asthma.

People with respiratory and heart problems, asthma and lung disease are at a higher risk, as are healthy adults exercising for long periods of time outdoors. Exposure to ozone has been linked to increased hospital admissions and premature death.

Ozone is toxic to plants and causes crop loss each year in Ontario, including noticeable leaf damage in many crops, garden plants and trees. Ozone can affect photosynthesis and plant respiration, reduce growth rates and affect reproduction.

It is also a powerful greenhouse gas and contributes to climate change.