Since 1994, countries around the world have been celebrating World Ozone Day on September 16 to spread awareness on the ozone layer, its depletion and ways to preserve it. Since the 1970s, there has been a rise in chlorine, commonly found in chlorofluorocarbons (CFCs) that are used in refrigerants and plastic products everywhere. When these CFCs get emitted into the atmosphere and reach the ozone layer, they are exposed to UV rays. This causes them to break down and release chlorine, which reacts with and rips apart the ozone molecule. According to the United States Environmental Protection Agency, one atom of chlorine can destroy more than a hundred thousand ozone molecules!
Ozone is a colourless gas found in the Earth’s atmosphere. It is formed from oxygen (O2), but has three atoms in its molecule and hence, its chemical symbol is O3. The ozone layer is located roughly 15 to 35 km above the Earth’s surface and contains a high concentration of ozone molecules. Compared to other gases, ozone is quite rare and the ozone layer only makes up 0.00006% of Earth’s atmosphere. But, it does an important job — it protects the earth from harmful rays.
Discoveries
1913: The Ozone Layer was first discovered by French physicists Charles Fabry and Henri Buisson
1924: Gordon Dobson, a British physicist and meteorologist invented the Dobson spectrophotometer, one of the earliest instruments to measure atmospheric ozone
1984: British scientists, Joseph Farman, Brian Gardiner and Jonathan Shanklin discovered a recurring springtime ‘ozone hole’ – a region of marked thinning of the ozone layer – over the Antarctic
A depleting layer
The amount of ozone in the atmosphere varies through the year. World Ozone Day marks the signing of this Protocol resulting in a gradual reduction in chlorine levels in the atmosphere and a recovery of ozone. CFCs has made the ozone layer thinner, especially above the Antarctic. It is estimated that a large majority of CFCs in the atmosphere today have been emitted by industrialised nations such as the U.S. and Europe. To curb such ozone-depleting substances, countries around the world signed the Montreal Protocol on September 16, 1987.
Why ozone matters
The ozone layer is like the Earth’s sunscreen, as it absorbs some of the sun’s radiation hitting our planet.
It is good at trapping ultraviolet rays (UV rays) that can penetrate living organisms’ cells and damage vital DNA molecules.
There are two types of UV rays – UVA and UVB.
UVA penetrates deep into the skin, causing Melanoma, a deadly skin cancer, and premature ageing.
UVB causes sunburns and other types of skin cancers like basal cell carcinoma and squamous cell carcinoma.
Photochemical smog
Some ozone is also found closer to the Earth’s surface. This is formed by a combination of certain pollutants, such as those containing nitrogen oxides and volatile organic compounds, strong sunlight and hot weather. It is one of the primary components in the photochemical smog that plagues many urban and suburban areas, especially during the summer.
These rays cause reduction in phytoplankton population which lies at the bottom of the food chain. And this will lower the populations of other animals.
Reproductive rates of other animals such as shrimp, crabs, frogs and salamanders exposed to excess UV radiation are also effected.
