Ozone is a molecule that is made up of three oxygen atoms. But chlorine atoms from CFC's attack the ozone by taking one oxygen atom away forming chlorine monoxide. The chlorine monoxide then combines with another oxygen atom to form a new oxygen molecule and a chlorine atom. the newly formed oxygen molecules do not block the ultraviolet light of the sun, allowing it to penetrate to the surface of the Earth.
When the sun's ultraviolet rays penetrate in the Earth's surface, it cause many changes to the environment. It can cause crop and forest damage,climate change,accumulation of tropespheric ozone and acid neroises causing worsening air pollution and acid rain, rise in incidence in skin cancer, respiratory illnesses and heart problems, and many other things. That's why drastic measures should be taken to protect that special ozone layer which is located in the stratosphere.