Ensuring protection of ozone layer must be our long-term commitment and responsibility
Published Date – 12 January 2025, 05:36 PM
By Tej Singh Kardam
Over two billion years ago, blue-green algae — early aquatic organisms — began using energy from the sun to convert molecules of water and carbon dioxide and recombine them into organic compounds and molecular oxygen. This resulted in an increase in oxygen and a decrease in carbon dioxide in the atmosphere. Some oxygen molecules absorb energy from the sun’s ultraviolet (UV) rays and split to form single oxygen atoms. These atoms combine with molecular oxygen to form ozone molecules, which are very effective in absorbing ultraviolet rays.
Ozone was discovered in 1785 by Dutch physicist MV Marum but it was only in 1840 that German chemist CF Schenbein could synthesise it.
The ozone layer is not really a layer but has become known as such because most ozone particles are scattered between 19 km and 30 km up in the stratosphere in the form of a thick sheet called ozonosphere. Ozone also occurs in very small amounts in the lowest few kilometres of the stratosphere — the troposphere. The ozone layer can absorb 97-99 per cent of harmful ultraviolet radiations that the sun emits which can produce long-term devastating effects on human beings as well as plants and animals.
Different Layers
There are two layers of ozone in the atmosphere: bad ozone exists in the troposphere from ground level up to 10 km and is harmful to breathe. After the 10 km stratosphere, we have a good ozone layer extending upward up to 30 km and protecting life on Earth from the sun’s harmful UV rays.
The bad ozone layer is created by chemical reactions between oxides of nitrogen and volatile organic compounds in the presence of sunlight. Ground-level ozone is a harmful pollutant. The good ozone layer is produced naturally in the stratosphere by UV rays reacting with oxygen.
The Centre for Science and Environment has revealed a disturbing trend in ground-level ozone pollution rise across India’s major cities like Delhi, Bengaluru, Jaipur and Kolkata
However, this good ozone has gradually been destroyed by human-made chemicals referred to as ozone-depleting substances (ODS), including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), halons, methyl bromide, carbon tetrachloride and methyl chloroform. These substances are being used in coolants, foaming agents, fire extinguishers, solvents, pesticides and aerosol propellants. They are broken down by the sun’s UV rays and release chlorine and bromine molecules, which destroy the good ozone. Scientists estimate that one chlorine atom can destroy 1,00,000 ozone molecules.
Ozone Hole
It is an area in the stratosphere where ozone depletion is so severe that levels fall below 200 Dobson Unit (DU) — the traditional measure of stratospheric ozone. Normal ozone concentration is 300-350 DU. Scientists say ozone-destroying substances (ODS) — mostly chlorine and bromine from CFCs and halon — are responsible for ozone depletion, to the extent of 1 per cent per day. Satellite data from NASA confirmed that the hole covered the entire Antarctic. The formation of ozone holes is irregular over the entire earth. For instance, the stratospheric circulation is much irregular in the Arctic region and the Arctic ozone layer is not as cold as that of the Antarctic, hence deep ozone hole is unlikely over the North Pole.
According to the head of the National Ozone Centre in New Delhi, there is no trend to show total ozone depletion in the stratosphere over India. However, the Centre for Science and Environment, New Delhi, revealed a disturbing trend in ground-level ozone pollution rise across India’s major cities like Delhi, Bengaluru, Jaipur and Kolkata.
Effects of Ozone Depletion
• Human and animal health: Exposure to ultraviolet radiation (UVR) to the skin causes sunburn, and skin cancer — also in animals — and to eyes, causing damage to cornea and cataracts.
• Terrestrial ecosystems: In forests and grasslands, UVR exposure results in mutation thus altering the biodiversity in different ecosystems.
• Aquatic ecosystems: The coastal zones are more sensitive to UVR than those living in offshore that are adapted to higher levels of radiation. UVR can cause damage to the early development stages of fish, shrimp, crabs, amphibians and other animals, the worst effect being decreased reproductive capacity and impaired larval development.
• Effect on materials: Increased levels of UVR have adverse effects on synthetic polymers, naturally occurring bio-polymers and some other materials of commercial interest.
Montreal Protocol
In a bid to contain ozone depletion, a landmark multilateral environmental agreement was formulated that regulates the production and consumption of ODS. ODS when released into the atmosphere change the stratospheric ozone layer — the earth’s protective shield that protects humans and the environment from harmful levels of UVR from the sun.
Adopted on 16 September 1987 and celebrated as International Day for Preservation of Ozone Layer, the Montreal Protocol is a rare treaty to achieve universal ratification. The parties to this reached an agreement on 15 October 2016 in Kigali, Rwanda, to phase down HFCs. The Montreal Protocol is saving about two million people each year by 2030 from skin cancer. The parties to the protocol have phased out 98 per cent of ODS globally compared with 1990 levels. Under the Kigali Amendment, the use of HFCs is expected to prevent emissions of up to 105 billion tonnes of carbon dioxide equivalent to GHGs, helping avoid up to 0.5 degrees Celsius of global temperature by 2100.
Solutions and Recovery
The entire planet is vulnerable to the effects and consequences due to ozone depletion.
Solutions include ODS like CFCs and halons should be avoided; eco-friendly pesticides should be used; nitrous oxide should be prohibited; natural and eco-friendly cleaning products should be used in the household apart from non-toxic products like vinegar and bicarbonate.
As per the guidelines of the Montreal Protocol and subsequent amendments, the consumption of ODS fell by 90-95 per cent till 2005. The size of the Antarctic ozone hole reached 29.9 million square kilometres in 2000. By 2021, the area shrunk to 24.8 million square kilometres. A few years ago, a United Nations report estimated that the Antarctic ozone hole would close slowly and the stratospheric ozone concentrations would return to 1980 values by 2060 and that of Arctic, ozone levels are expected to return to 1980 values by the mid-2030s.
Ensuring the protection of the ozone layer must be our long-term commitment and responsibility. The whole of humanity around the world and each generation must take up the baton to ensure the continued survival of our planet’s protective shield. Teaching the next generation about the Montreal Protocol empowers them with the knowledge that environmental challenges can be overcome if we listen to science and work together.
(The author is a retired IFS officer)
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