CFCs (chlorofluorocarbons) contain chlorine atoms, which are released into the atmosphere. When these chlorine atoms come into contact with ozone molecules in the ozone layer, they react and break down the ozone molecules. This reaction is known as ozone depletion. As a result, the ozone layer becomes thinner, allowing harmful ultraviolet (UV) radiation from the sun to reach the Earth's surface. This UV radiation can cause various health issues in humans, such as skin cancer, cataracts, and weakened immune system, and also harm marine life and ecosystems. Therefore, the presence of chlorine atoms in CFCs contributes to the destruction of the ozone layer.