Thinning layer is a term used to describe the OZONE layer, which is a layer of gas in the Earth's atmosphere that protects us from the sun's ultraviolet radiation. The OZONE layer is composed of three oxygen atoms and is abbreviated as O3. It is located in the stratosphere, which is the second layer of the atmosphere. The thinning layer of OZONE has been decreasing due to human activities such as the release of chlorofluorocarbons (CFCs) into the atmosphere. This has caused an increase in the amount of UV radiation reaching the Earth's surface, leading to an increase in skin cancer and other health problems.