Earth's atmosphere

Ozone (O3) or ‘trioxygen’ is a naturally occurring, colorless, unstable and toxic trace gas containing three bonded oxygen atoms per molecule. It is formed from dioxygen (O2) by means of electrical discharges of ultraviolet light. Ozone's name is derived from the Greek word for smelling, which references its pungent odor. In Earth's stratosphere, ozone helps protect life below. But ground-level ozone is a poisonous gas and the main component of smog.

Ozone is most commonly found in the stratosphere, which acts as a protective layer against harmful ultraviolet light from the sun. In recent decades the deterioration of this ozone layer due to pollution has become a pertinent and alarming issue. Ozone is broken down by chlorine atoms formed from particles called chlorofluorocarbons, which are found in aerosols.  

This depletion has led to 'holes' in the ozone layer, which let an abundance of ultraviolet rays into Earth's atmosphere. UV rays induce a higher risk of skin cancer in humans and expedite the process of climate change. (Photo: Shutterstock)

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