What is ozone, ozone layer and ozone hole?

• Ozone is a gas made of three oxygen atoms, and just like any other gas it circulates in the atmosphere.
• Ozone is present throughout the atmosphere although there are concentration peaks at two levels, the stratosphere (a layer of the atmosphere between 10 and 40 km above us) and troposphere (the atmospheric layer from the surface up to about 10 km).
• Stratospheric ozone forms a protective layer that shields us from the sun’s harmful ultraviolet rays. However, this beneficial ozone has been partially destroyed by chemicals used for refrigeration purposes, such as chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs), causing what is sometimes called a “hole in the ozone.” 
• Areas with ozone concentrations less than 220 Dobson Units are called “holes” in the layer.
• Ozone at ground level (troposphere) is a harmful air pollutant, because of its effects on people and the environment, and it is the main ingredient in “smog.” Tropospheric ozone is a harmful pollutant that causes damage to lung tissue and plants.
• Tropospheric ozone is not emitted directly from anthropogenic sources. It is a “secondary” pollutant formed 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.

What are the health effects of ozone?

• Ozone in the air we breathe can harm our health. People most at risk from breathing air containing ozone include people with asthma, children, older adults, and people who are active outdoors, especially outdoor workers. 
• In addition, people with certain genetic characteristics, and people with reduced intake of certain nutrients, such as vitamins C and E, are at greater risk from ozone exposure.
• Breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and airway inflammation. It also can reduce lung function and harm lung tissue. Ozone can worsen bronchitis, emphysema, and asthma, leading to increased medical care.

What are the environmental effects of ozone?

• Ozone affects sensitive vegetation and ecosystems, including forests, parks, wildlife refuges and wilderness areas.  In particular, ozone harms sensitive vegetation during the growing season. 

Measures related to ozone depletion

• The Montreal Protocol, a landmark international environmental treaty that took effect in 1988, has reduced CFC emissions worldwide. It is termed as one of the most successful international agreements.
• In 2016, Parties to the Montreal Protocol adopted the Kigali amendment to phase down production and consumption of HFCs worldwide. 

Montreal Protocol

• The Montreal Protocol on Substances that Deplete the Ozone Layer is an international environmental treaty that regulates the production and consumption of nearly 100 man-made chemicals referred to as ozone depleting substances (ODS) including chlorofluorocarbons (CFCs), halons and hydrochlorofluorocarbons (HCFCs).
• The stratospheric ozone layer protects humans and the environment from harmful levels of ultraviolet radiation from the sun. The widespread use of ODS had caused a hole in the Ozone layer of the atmosphere, which allowed some harmful radiation to reach the earth. These radiations were considered potential health hazards. 
• Adopted in 1987, the Montreal Protocol is the only UN treaty that has been ratified by every country.
• Under this treaty, all parties have specific responsibilities related to the phase out of the different groups of ODS, control of ODS trade, annual reporting of data, national licensing systems to control ODS imports and exports, and other matters. 
• Developing and developed countries have equal but differentiated responsibilities along with binding, time-targeted and measurable commitments.
• The Montreal Protocol has been a far more effective and successful agreement than the climate change instruments. It has already resulted in the phase-out of 98.6% of ozone-depleting substances. The remaining 1.4% are the HCFCs that are in the process of being transitioned.

About Hydrofluorocarbons

• Hydrofluorocarbons (HFCs) are a group of industrial chemicals primarily used for cooling and refrigeration. 
• HFCs are powerful greenhouse gases and a substantial number are short-lived climate pollutants with a lifetime of between 15 and 29 years in the atmosphere.
• HFCs are widespread in air conditioners, refrigerators, aerosols, foams and other products.
• HFCs were introduced as non-ozone depleting alternatives to support the timely phase out of CFCs and HCFCs under Montreal Protocol. 
• While these chemicals do not deplete the stratospheric ozone layer, HFCs were found to be extremely potent in causing global warming. Some of them have high Global Warming Potentials (GWPs) ranging from 12 to 14,000. 
• So, the HFCs solved one problem, but were contributing in a major way to another. But these could not be eliminated under the original provisions of Montreal Protocol which was meant to phase-out ozone-destroying chemicals only. The Kigali Amendment enabled the Montreal Protocol to mandate the elimination of HFCs as well.

Kigali Agreement

• The Parties to the Montreal Protocol reached agreement at their 28th Meeting of the Parties on 15 October 2016 in Kigali, Rwanda. The Agreement particularly aims at phasing out the production and consumption of Hydrofluorocarbons which were first introduced as a substitute to ODSs namely CFCs and Hydrochlorofluorocarbons HCFCs. 
• Before the middle of this century, current HFC use has to be curtailed by at least 85 per cent. Countries have different timelines to do this. India has to achieve this target by 2047 while the developed countries have to do it by 2036. China and some other countries have a target of 2045.
• While the reductions for the rich countries have to begin immediately, India, and some other countries, have to begin cutting their HFC use only from 2031.
• The agreement came into force on 1st January 2019 and has been ratified by 119 countries so far.
• The phasing down of HFCs is expected to prevent the emission to the tune of 105 million tonnes of greenhouse gases, which would potentially help avoid a rise in global temperature up to 0.5 degrees Celsius by the year 2100.
• Kigali Agreement legally binds the signatory countries with non-compliance measures. 
• India’s Union Cabinet recently gave its approval for ratification of the Kigali Amendment for phasing down of ozone layer-depleting hydrofluorocarbons by India under the Montreal Protocol.

Why in News?

• The 27th Global Ozone Day was observed in New Delhi.
• World Ozone Day is celebrated on 16th September each year to commemorate the signing of the Montreal Protocol, an international environmental treaty for phasing out of production and consumption of Ozone Depleting Substances, that came into force on this day in 1987. 

Reference:

1. https://pib.gov.in/PressReleasePage.aspx?PRID=1755402