- In 1994, the UN General Assembly proclaimed 16 September the International Day for the Preservation of the Ozone Layer, commemorating the date of the signing, in 1987, of the Montreal Protocol on Substances that Deplete the Ozone Layer.
- The Montreal Protocol on Substances that Deplete the Ozone Layer”
- was accepted on 26 August 1987 by the United Nations (UN),
- enforced on 16 September 1989, and
- is popularly considered the most successful international environmental treaty till date.
- Theme for 2020 – Ozone for life: 35 years of ozone layer protection
- The ozone layer is a part of the atmosphere that has high concentrations of ozone (a gas made of three oxygen atoms O3), compared to oxygen molecules that exist in nature as a pair of oxygen atoms.
- It exists 10km to 40km above the surface of the earth in a region called the stratosphere and contains 90 percent of all the ozone in the atmosphere.
- The layer is formed when oxygen molecules are broken apart by the ultra-violet (UV) rays of the sun in the stratosphere.
- This causes some of the reactive oxygen atoms to combine with oxygen molecules to form ozone.
- The Ozone layer forms a natural shield that protects the Earth from the harmful UV rays of the sun, for which it gets the term “good ozone”.
- There is also “bad ozone”, which harms animals, plants and human beings.
- This ozone is the excess released from the ground as pollution from cars, power plants, industrial boilers, refineries, chemical plants, and other sources react chemically in the presence of sunlight.
- Using certain compounds, like Hydrochlorofluorocarbons (HCFC) and Chlorofluorocarbons (CFCs) can mess around with the formation of ozone.
- This can cause gaps or ‘holes’ in the layer, and allow harmful UV radiation from the sun to pass through the atmosphere without reflecting some of it away.
- The ozone hole over Antarctica was first discovered by the British Antarctic Survey in 1985.
- CFCs are a class of compounds of carbon, hydrogen, chlorine, and fluorine, typically gases used in refrigerants and aerosol propellants.
- They are harmful to the ozone layer in the earth’s atmosphere owing to the release of chlorine atoms on exposure to ultraviolet radiation.
- HCFCs are a group of man-made compounds containing hydrogen, chlorine, fluorine and carbon and do not occur naturally anywhere.
- The production of HCFC began to take off after countries agreed to phase out the use of CFCs in the 1980s.
- These compounds are used in refrigeration, aerosol propellants, foam manufacture and air conditioning.
- Unlike CFCs, most HCFCs are broken down in the lowest part of the atmosphere and pose a much smaller risk to the ozone layer.
- They are still very potent greenhouse gases.
