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            September 16th every year is marked as the International Day for the Preservation of the Ozone Layer. On this day 32 years ago, 45 countries signed a treaty to phase out the use of the substances that harm or deplete the ozone layer, however all 197 countries of the world ratified the agreement later. The ozone layer is a part of the atmosphere that has high concentrations of ozone, compared to oxygen molecules that exist in nature as a pair of oxygen atoms. It exists 10-40 kms above the surface of the earth in a region called the stratosphere and contains 90% of all the ozone in the atmosphere. Depletion of ozone layer has an adverse effect on our environment, the most visible one being global warming. World Ozone Day is a reminder to people on the important role ozone plays in our atmosphere and why we need to reduce use of substances that are thinning the ozone layer.


World Ozone Day

  • Celebrating international cooperation under Montreal.
  • The theme of World Ozone Day 2019 is ’32 years and Healing’.
  • This year’s theme celebrates three decades of remarkable international cooperation to protect the Ozone Layer and the climate under the Montreal Protocol.
  • Thanks to international cooperation ozone layer now healing.
  • It also reminds the people to keep up the momentum to ensure healthy people and a healthy planet.
  • Ozone depletion refers to two events observed since late 1970s
  • Steady lowering of 4% of total amount of ozone in atmosphere.
  • In 2018, the latest Scientific Assessment of Ozone Depletion was completed.
  • This assessment shows that the parts of the Ozone Layer have recovered at a rate of 1-3% per decade since 2000.
  • Even at the protected rates, Northern hemisphere and mid-latitude ozone will heal completely by the 2030s. The Southern Hemisphere will follow in the 2050s and Polar Regions by 2060.
  • No doubt Ozone Layer protection efforts also contribute in fighting with the climate change
  • Cause: Refrigerants, solvents, propellants, foam-blowing agents


Ozone layer

  • Atmospheric ozone concentrated in a layer in stratosphere.
  • About 9 to 18 miles above Earth’s surface.


What does ozone layer do?

  • Absorbs a range of ultraviolet energy
  • Ozone molecule absorbs even low-energy ultraviolent radiation.
  • Splits into ordinary oxygen molecule and free oxygen atom.
  • Free oxygen atom quickly re-joins with an oxygen molecule to form another ozone molecule
  • Ozone-oxygen cycle converts harmful UV radiation into heat and acts as a shield
  • Weakening ozone layer causes skin cancer, cataracts and impairs immune systems.


Good Ozone

Called stratospheric ozone, good ozone occurs naturally in the upper atmosphere, where it forms a protective layer that shields us from the sun’s harmful ultraviolet rays. This beneficial ozone has been partially destroyed by manmade chemicals, causing what is sometimes called a “hole in the ozone.” 

Bad Ozone

Tropospheric, or ground level ozone, is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC). This happens when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources chemically react in the presence of sunlight. Ozone at ground level is a harmful air pollutant, because of its effects on people and the environment, and it is the main ingredient in “smog.”

Ozone can also be transported long distances by wind, so even rural areas can experience high ozone levels. 


Ground-Level Ozone

Ozone (O3) is a colourless, reactive oxidant gas that is a major constituent of atmospheric smog. Many factors impact ground-level ozone development, including temperature, wind speed and direction, time of day, and driving patterns.

  • Ground level ozone is formed by the reaction of NOx and VOCs under the influence of sunlight hundreds of kilometers from the source of emissions.
  • Ozone concentrations are influenced by the intensity of solar radiation, the absolute concentrations of NOx and VOCs, and the ratio of NOx and VOCs.
  • Peak ground-level ozone concentrations are measured in the afternoon.
  • Both natural and anthropogenic sources contribute to the emission of ground-level ozone precursors, and the composition of emissions sources may show large variations across locations.
  • Anaerobic biological processes, lightning, and volcanic activity are the main natural contributors to atmospheric NOx, occasionally accounting for as much as 90% of all NOx emissions.
  • Motor vehicles are the main anthropogenic sources of ground-level ozone precursors. Other anthropogenic sources of VOCs include emissions from the chemical and petroleum industries and from organic solvents in small stationary sources such as dry cleaners.


Ozone Depleting Substances

  • Chlorofluorocarbons
  • Hydrochlorofluorocarbons
  • Carbon tetrachloride
  • Methyl chloroform
  • Methyl chloroform
  • Halons
  • Methy bromide


Impacts of Ozone

  • The main health concern of exposure to ambient ground-level ozone is its effect on the respiratory system, especially on lung function.
  • Elevated ground-level ozone exposures affect agricultural crops and trees, especially slow growing crops and long-lived trees.
  • Ozone damages the leaves and needles of sensitive plants, causing visible alterations such as defoliation and change of leaf colour.


Montreal protocol

The Montreal Protocol on Substances that Deplete the Ozone Layer was designed to reduce the production and consumption of ozone depleting substances in order to reduce their abundance in the atmosphere, and thereby protect the earth’s fragile ozone Layer. The original Montreal Protocol was agreed on 16 September 1987 and entered into force on 1 January 1989.

  • The Montreal Protocol includes a unique adjustment provision that enables the Parties to the Protocol to respond quickly to new scientific information and agree to accelerate the reductions required on chemicals already covered by the Protocol. These adjustments are then automatically applicable to all countries that ratified the Protocol.
  • Montreal Protocol stipulates that the production and consumption of compounds that deplete ozone in the stratosphere-chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform-are to be phased out by 2000 (2005 for methyl chloroform). These compounds significantly deplete the stratospheric ozone layer that shields the planet from damaging UV-B radiation.


Kigali Agreement

  • Around 197 countries, including India, China and the USA, agreed at Kigali to reduce the use of HFCs by roughly 85% of their baselines by 2045.
  • It amends the 1987 Montreal Protocol.
  • It is proposed to reduce Hydro fluorocarbons (HFCs).
  • The agreement has got three separate pathways for different countries.
    • Richer countries like the European Union, the USA and others will start to limit their use of HFCs within few years and make a cut-off of at least 10% from 2019.
    • Overall, these countries will reduce them to about 15% of 2010-12 baseline levels by 2036.
    • China, Brazil and some other developing countries will freeze Hydro fluorocarbons use by 2024, cutting it to 20% of 2020-22 baseline levels by 2045.
    • India is a part of the third group along with Iran, Pakistan, and Saudi Arabia etc. That will be freezing HFCs only by 2028 and reducing them to about 15% of 2024-26 baseline levels by 2047.
  • Overall, Kigali deal will result in reducing the global temperature rise by 0.50C
  • As it is an amendment to Montreal Protocol, it will bind countries to their HFCs reduction schedules from 2019.
  • There are also penalties for noncompliance  Overall, the deal is expected to result in the reduction of an equivalent 70 bn tonnes of carbon dioxide from the atmosphere.
  • The Agreement upholds the principle of Common but Differentiated Responsibilities and Respective Capabilities.
  • The countries negotiating at Kigali also agreed to provide adequate financing for HFCs reduction— which runs in billions of dollars globally.
  • The agreement at Kigali provides for exemptions for countries with high ambient temperatures to phase down HFCs at a slower pace

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