Where does the largest concentration of ozone exist?

The largest concentration of ozone exists in the stratosphere. This region of the Earth's atmosphere, situated above the troposphere and below the mesosphere, contains the ozone layer, which plays a crucial role in absorbing the majority of the sun's harmful ultraviolet (UV) radiation.

Ozone (O3) in the stratosphere is formed through a chemical reaction between oxygen molecules (O2) and UV light. This natural protective layer is vital for maintaining life on Earth by shielding the surface from excessive UV radiation, which can lead to skin cancer and other health issues, as well as negative effects on ecosystems.

The concentration of ozone significantly decreases below this layer in the troposphere, where ozone is not present in high enough quantities to be considered a significant protective barrier. In the mesosphere, while there is some ozone, it is far less concentrated compared to that found in the stratosphere. The term "atmosphere" refers broadly to all layers but does not specify the area where the concentration is highest, making the stratosphere the most accurate answer.