Dr Mandeep Singh Azad, Dr Manmeet Motan
World Ozone Day, is celebrated on September 16 every year. It shows that collective decisions and action, guided by science, are the only way to solve major global crises. In this year of the coronavirus pandemic that has brought such social and economic hardship, the ozone treaties’ message of working together in harmony and for the collective good is more important than ever. The United Nations General Assembly on 23rd January, 1995 adopted resolution 49/114, which proclaims 16th September as the World Ozone Day, commemorating the date on which Montreal Protocol on Substances that deplete the Ozone Layer was signed in 1987. The World Ozone Day offers an opportunity to focus global attention and action on this vital environmental issue. The theme for the celebration of this year’s World Ozone Day is “Montreal Protocol – Keeping us, our food and vaccines cool”. India is a Party to the Vienna Convention for the Protection of the Ozone Layer and the Montreal Protocol on Substances that deplete the Ozone Layer and all its amendments. India has been successfully implementing the phase-out programme of Ozone Depleting Substances (ODSs) in the country. India is now phasing out the next category of chemicals, Hydrochlorofluorocarbons (HCFs as per the accelerated phase-out schedule of the Montreal Protocol and has already met 2015 and 2020 phase-out targets. The complete phase-out of production and consumption of HCFCs will be by 2030 with a service tail of 2.5% annual average during the period 2030-2040.
Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth’s atmosphere (the ozone layer), and a much larger springtime decrease in stratospheric ozone around Earth’s polar regions. The latter phenomenon is referred to as the ozone hole. There are also springtime polar tropospheric ozone depletion events in addition to these stratospheric events.The main cause of ozone depletion and the ozone hole is manufactured chemicals, especially manufactured halocarbon refrigerants, chlorofluorocarbons (CFCs), HCFCs, halons, referred to as ozone-depleting substances (ODS). These compounds are transported into the stratosphere by turbulent mixing after being emitted from the surface, mixing much faster than the molecules can settle. Once in the stratosphere, they release atoms from the halogen group through photodissociation, which catalyze the breakdown of ozone (O3) into oxygen (O2). Both types of ozone depletion were observed to increase as emissions of halocarbons increased.
Over the past 30 years humans have made progress in stopping damage to the ozone layer by curbing the use of certain chemicals. But more remains to be done to protect and restore the atmospheric shield that sits in the stratosphere about 9 to 18 miles (15 to 30 kilometers) above the Earth’s surface. Atmospheric ozone absorbs ultraviolet (UV) radiation from the sun, particularly harmful UVB-type rays. Exposure to UVB radiation is linked with increased risk of skin cancer and cataracts, as well as damage to plants and marine ecosystems. Atmospheric ozone is sometimes labeled as the “good” ozone, because of its protective role, and shouldn’t be confused with tropospheric, or ground-level, “bad” ozone, a key component of air pollution that is linked with respiratory disease.
Human activities have had a significant effect on the global concentration and distribution of stratospheric ozone since before the 1980s. In addition, scientists have noted that large annual decreases in average ozone concentrations began to occur by at least 1980. Measurements from satellites, aircraft, ground-based sensors, and other instruments indicate that total integrated column levels of ozone (that is, the number of ozone molecules occurring per square metre in sampled columns of air) decreased globally by roughly 5 percent between 1970 and the mid-1990s, with little change afterward. The largest decreases in ozone took place in the high latitudes (toward the poles), and the smallest decreases occurred in the lower latitudes (the tropics). In addition, atmospheric measurements show that the depletion of the ozone layer increased the amount of UV radiation reaching Earth’s surface.
This global decrease in stratospheric ozone is well correlated with rising levels of chlorine and bromine in the stratosphere from the manufacture and release of CFCs and other halocarbons. Halocarbons are produced by industry for a variety of uses, such as refrigerants (in refrigerators, air conditioners, and large chillers), propellants for aerosol cans, blowing agents for making plastic foams, firefighting agents, and solvents for dry cleaning and degreasing. Atmospheric measurements have clearly corroborated theoretical studies showing that chlorine and bromine released from halocarbons in the stratosphere react with and destroy ozone.
Most man-made ozone-depleting substances are also potent greenhouse gases. Some of them have a global warming effect up to 14,000 times stronger than carbon dioxide (CO2), the main greenhouse gas. Therefore, the global phase-out of ozone depleting substances such as hydrochlorofluorocarbons (HCFCs) and chlorofluorocarbons (CFCs) has also made a significant positive contribution to the fight against climate change. On the other hand, the global phase-out has led to a large increase in the use of other types of gases, to replace ozone depleting substances in various applications. These fluorinated gases (‘F-gases’) do not damage the ozone layer, but do have a significant global warming effect. Nitrous oxide, commonly known as laughing gas, is now the dominant ozone-depleting substance emitted by humans – and is likely to remain so throughout the century, a new study suggests.Researchers suggest use of the compound – which is produced by the breakdown of nitrogen in fertilisers and sewage treatment plants – should be reduced to avoid thinning the protective ozone layer that blankets the Earth.
Measure to control ozone depletion
* Avoid the consumption of gases dangerous to the ozone layer, due to their content or manufacturing process.
* Minimize the use of cars. The best transport option is urban, bicycle, or walking. If you use a car to a destination, try to carpool with others to decrease the use of cars in order to pollute less and save.
* Do not use cleaning products that are harmful to the environment and to us. Many cleaning products contain solvents and substances corrosive, but you can replace these dangerous substances with non-toxic products such as vinegar or bicarbonate.
* Buy local products. In this way, you not only get fresh products but you avoid consuming food that has travelled long distances. As the more distance travelled, the more nitrous oxide is produced due to the medium used to transport that product.
* Maintain air conditioners, as their malfunctions cause CFC to escape into the atmosphere.
Trending Now
E-Paper
Follow our WhatsApp channel