Context:
Ozone-depleting HCFCs show drop in levels 5 years ahead of target year
Key highlights of study:
- Impact of Hydrochlorofluorocarbons (HCFCs) on Earth’s energy balance and globally averaged chlorine content of ODS in troposphere has decreased since 2021, five years earlier (2026) than expected.
- HCFC-22 – most abundant HCFC, has declined significantly.
- Minor decline was observed in HCFC-141b, 2nd most abundant HCFC.
- HCFC-141b is used as a blowing agent in production of rigid polyurethane foams.
India has achieved complete phase-out of HCFC-141b under ODS (Regulation and Control) Amendment Rules, 2014. This is in line with India’s commitment under Montreal Protocol for Substances that Deplete Ozone Layer.
Hydrochlorofluorocarbons (HCFCs):
- Compounds containing carbon, hydrogen, chlorine and fluorine.
- HCFC-22 – Global Warming Potential (GWP) is 1000 times more than carbon dioxide (CO2).
- HCFC-22 – used as a refrigerant in air conditioners, cold storage, retail food refrigeration, etc.
Montreal Protocol:
- Signed in 1987.
- A global treaty to eliminate production and use of ODS.
- Implemented under Vienna Convention (adopted in 1985).
- Kigali Amendment to Montreal Protocol was adopted in 2016 (and entered into force in 2019) to phase-down production and consumption of Hydrofluorocarbons (HFCs).
HFCs are non-ODS alternative to CFCs and HCFCs. HFC’s GWP is thousands of times more than CO2.
Ozone and Ozone-Depleting Substances (ODS):
- ODS are human-made chemicals containing chlorine and bromine (like Chlorofluorocarbons (CFCs), HCFC).
- They can reach stratosphere where they undergo catalytic reactions, further leading to destruction of ozone.
- Stratospheric ozone (good Ozone) is found at 10-40 KM above Earth’s surface, and protects Earth from UV radiation of Sun.
- Ozone formed in Troposphere is harmful and is called ‘bad ozone’.
Source: Down to Earth
Previous Year Question
In the context of WHO Air Quality Guidelines, consider the following statements:
1. The 24-hour mean of PM2.5 should not exceed 15 µg/m³ and annual mean of PM2.5 should not exceed 5 µg/m3.
2. In a year, the highest levels of ozone pollution occur during the periods of inclement weather.
3. PM10 can penetrate the lung barrier and enter the bloodstream.
4. Excessive ozone in the air can trigger asthma.
Which of the statements given above are correct?
[UPSC Civil Services Exam – 2022 Prelims]
(a) 1, 3 and 4
(b) 1 and 4 only
(c) 2, 3 and 4
(d) 1 and 2 only
Answer: (b)
