Dr Konthoujam Khelchandra
The United Nations International Day for the Preservation of the Ozone Layer is celebrated every year on September 16. The theme for this year’s celebration of World Ozone Day is”32 Years and Healing”. This event commemorates the date of the signing of the Montreal Protocol on substances that deplete the ozone layer in 1987. This protocol has led to phase-out of 99% of ozone depleting substances in refrigerators, air-conditioners and many other products. The latestreports of Scientific Assessment of Ozone Depletion completed in 2018 indicates very favourable results as there is ozone layer recovery rate of 1-3% per decades since 2000. The UN report further highlighted that the ozone layer protection measures has actually help in combating climate change by averting an estimated 135 billion tonnes of carbon dioxide equivalent emissions from 1990 to 2010.
This year’s World Ozone day, the Montreal Protocol is celebrating its 32th anniversary. The protocol accentuates the extraordinary collaborations and environmental benefits achieved by the world governments through the operation of Montreal Protocol for the effective protection of ozone layer. Thisprotocol provides an inspiring example where the global community is truly succeeding in reaching sustainable development objectives. It is expected to return to pre-1980 levels by mid-century, assuming all countries continue to meet their compliance commitments. In 32 years of successful implementation, the protocol has been continuously strengthened to cover the phase out of nearly 100 ozone depleting substances. It is the world’s most widely ratified treaty, with 197 signatories. Its multilateral fund has enabled an unprecedented transfer of ozone friendly technologies to developing countries assisted by a powerful network of well-trained national ozone officers in every country of the world. The protocol is widely hailed as a classic case of science-based policy making and action to protect a global commons. It also certainly reminds us that we have to keep the impetus of ensuring a healthy planet where all inhabitants can harmoniously coexist by interacting and interdepending on each other.
Depletion of stratospheric ozone:Certain industrial processes and consumer products result in the emission of ozone depleting substances (ODSs) to the atmosphere. The main ODS are chlorofluorocarbons (CFCs), hydrochlorofluorcarbons (HCFCs), carbon tetrachloride, methyl chloroform and halons (brominated fluorocarbons). CFCs are the most widely used ODS, accounting for over 80% of total stratospheric ozone depletion; used as coolants in refrigerators, freezers and air conditioners in buildings and cars manufactured before 1995; found in industrial solvents, dry-cleaning agents and hospital sterilants; also used in foam products- such as soft-foam padding (e.g. cushions and mattresses) and rigid foam (e.g. home insulation). Halons are used in some fire extinguishers, in cases where materials and equipment would be destroyed by water or other fire extinguisher chemicals. But, the problem with halons is they can destroy up to 10 times as much ozone as CFCs can. ODSs are manufactured halogen source gases that are controlled worldwide by the Montreal Protocol. These gases bring chlorine and bromine atoms to the stratosphere, where they destroy ozone in chemical reactions. Current ODS abundances in the atmosphere are known directly from air sample measurements.
The initial step in the depletion of stratospheric ozone by human activities is the emission, at earth’s surface, of gases containing chlorine and bromine. Most of these gases accumulate in the lower atmosphere because they are unreactive and do not dissolve readily in rain or snow. Natural air motions transport these accumulated gases to the stratosphere, where they are converted to more reactive gases. Some of these gases then participate in reactions that destroy ozone. Finally, when air returns to the lower atmosphere, these reactive chlorine and bromine gases are removed from earth’s atmosphere by rain and snow.
Impacts of ozone depletion:The ozone present in the stratosphere filters out most of the sun’s potentially harmful shortwave ultraviolet (UV) radiation. If this ozone becomes depleted, then more UV rays will reach the earth. Exposure to higher amounts of UV radiation could have serious impacts on human beings, animals and plants. It can have serious implication to human health causing more skin cancers, sunburns and premature aging of skin, more cataracts, blindness and other eye diseases. It weakens the human immune system. It also has adverse impact on agriculture, forestry and natural ecosystems. Several of the world’s major crop species are particularly vulnerable to increased UV, resulting in reduced growth, photosynthesis and flowering. Only a few commercially important trees have been tested for UV (UV-B) sensitivity, but early results suggest that plant growth, especially in seedlings, is harmed by more intense UV radiation. Damage to marine life- in particular, planktons is threatened by increased UV radiation. Planktons are the first vital step in aquatic food chains; Decreases in plankton could disrupt the fresh and saltwater food chains, and further lead to a species shift; Loss of biodiversity in our oceans, rivers and lakes could reduce fish yields for commercial and fisheries. The Efforts to protect the ozone layer and to combat climate change are mutually supportive. The most recent adjustments to the Montreal Protocol, adopted in 2007, accelerate the phase out of hydrochlorofluorocarbons (HCFCs). The level of climate benefits that can be achieved depends on what chemicals and technologies replace HCFCs.
Their phase out thus offers a unique opportunity to acquire cutting-edge technologies that not only eliminate ozone depleting chemicals, but also saves energy and maximises climate benefits. Although the substantial phase-out of HCFCs has only just begun, it is heartening to see that industry is applying the new alternative technologies. These technologies will not only eliminate damage to the ozone layer, but also reduce adverse effects on climate.
Conclusion: On this World Ozone Day, let us celebrate and reemphasise the greater necessities for protection of ozone layer. Ozone in the stratosphere absorbs a large part of the sun’s biologically harmful ultraviolet radiation;stratospheric ozone is considered good ozone because of this beneficial role. In contrast, ozone formed at earth’s surface in excess of natural amounts is considered bad ozone because it is harmful to humans, plants, and animals. Natural ozone near the surface and in the lower atmosphere plays an important beneficial role in chemically removing pollutants from the atmosphere.So, the phase out of the controlled uses of the ozone depleting substances and related reductions has not only helped protect the ozone layer for this and also for future generations to come. It has also significantly contributed on global efforts to combat climate change and furthermore it has protected human health and ecosystems by limiting the harmful ultraviolet radiation from reaching the earth. Finally, we should continue our untiringefforts for preservation of ozone layer for the betterment of our mother earth.
(The author is currently working as Assistant Professor, Department of Environmental Science, Pachhunga University College, Aizawl. He can be contacted at: [email protected]