Stratospheric ozone loss occurs due to the presence of ozone-depleting compounds in the atmosphere catalyzing reactions which deconstruct O3 molecules.
-Chlorine does this, as do H2O, NO and N2O
-Also, solar radiation naturally destroys ozone (O3 + hv => O + O2 => O+ O3 => 3O2)
-OR with catalyst: X(catalyst) + O3 => XO + O2 => O3 + hv => O + O2 => O+XO => X +2O2
-Chlorine destruction: O3 + Cl => ClO + O2 O3 + hv => O+O2 O + ClO => Cl + O2 (Cl is preserved and continues to destroy).