Chlorofluorocarbons
Also called: CFCs, Halons · Topic: Environment and Sustainable Development · NCERT: Class 11, Ch 7 "Environment and Sustainable Development"
Meaning
Chlorofluorocarbons (CFCs) are chemicals once used as coolants in refrigerators and ACs and as propellants in aerosol sprays. Halons are related chemicals (bromofluorocarbons) used in fire extinguishers. In the stratosphere, the upper atmosphere where the ozone layer sits, they release chlorine and bromine that destroy ozone. More ultraviolet radiation (UV-B) then reaches the earth. It causes skin cancer, lowers phytoplankton output (which hurts aquatic food chains) and affects plant growth. The Montreal Protocol (1987) phases out these ozone-depleting substances.
Example
NCERT records about a 5% fall in the ozone layer between 1979 and 1990. After the Montreal Protocol, CFC use was phased out worldwide. The UNEP/WMO 2023 assessment projects that Antarctic ozone will recover to 1980 levels around 2066.
Don't confuse with
- HFCs (hydrofluorocarbons): they replaced CFCs and do not harm ozone. However, they are powerful greenhouse gases. They are phased down under the Kigali Amendment (2016), not the original Montreal Protocol. India's HFC use freezes in 2028, followed by an 85% cut by 2047.