Ozone is created by sunlight high in the stratosphere
Lower down in the stratosphere ozone is destroyed naturally in reactions with other atmospheric gases.
300.000.000 tons of ozone are produced and naturally destroyed by this cycle every day.
Ozone depletion occurs if the processes destroying ozone are augmented by, for example chlorine or bromine so that the balance is disturbed.
Because ozone absorbs solar UV radiation, lower ozone amounts in the layer coincide with an increase in the flux of UV-B into the lower atmosphere. The concern is that, if ozone depletion were to persist, the average UV-B flux could increase.