APES Air Pollution Practice Test

Ozone that contributes to the formation of smog is found in the troposphere, which is the lowest layer of Earth's atmosphere. In this layer, human activities such as vehicle emissions and industrial processes release pollutants that can react with sunlight to form ground-level ozone. This ozone is a key component of smog and can have harmful effects on human health and the environment.

While ozone is also present in the stratosphere, where it forms the ozone layer that protects us from harmful ultraviolet radiation, this stratospheric ozone is not associated with smog. The mesosphere and exosphere are higher atmospheric layers where conditions are not conducive to the formation of smog or ground-level ozone, reinforcing the importance of the troposphere in relation to air quality issues like smog formation.