The ozone layer is a region of Earth's stratosphere that absorbs 97 to 99% of the Sun's medium-frequency ultraviolet (UV) radiation. It contains higher concentrations of ozone (O3) relative to other layers of the atmosphere, and resides approximately 20 to 30 km (12 to 19 mi) above the Earth's surface. Protecting the ozone layer is key to reducing human exposure to Medium-frequency ultraviolet radiation (i.e. UVB rays), a leading cause of skin cancer and cataracts. UVB radiation also affects other animals and plants.
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