1. Chlorofluorocarbons (CFCs): These were once widely used in refrigerants, aerosols, and foam blowing agents. When CFCs reach the stratosphere, ultraviolet radiation from the sun breaks them down, releasing chlorine atoms. These chlorine atoms act as catalysts, breaking down ozone molecules (O3) into oxygen molecules (O2). One chlorine atom can destroy thousands of ozone molecules before it is removed from the atmosphere.
2. Halons: These are similar to CFCs in their structure and destructive effect on ozone. They were used in fire extinguishers, but their use is now heavily restricted due to their impact on the ozone layer.
3. Methyl bromide: This chemical was used as a fumigant to kill pests in soil and crops. It also contains bromine atoms, which are even more efficient at destroying ozone than chlorine atoms.
It's important to note that while these are the most well-known ozone-depleting substances, others exist, and their impact on the ozone layer is still being researched.
