PVC (polyvinylchloride) has the molecular formula C2H3Cl ...
Later (or better yet now) you will know that Chlorine atoms are resonsible for ruining the ozone layer mainly caused by chlorofluorocarbons (CFCs) but PVC contains Chlorine atoms too so Greenies aren't impressed at PVCs at all despite its strength.
Ultraviolet radiation from the sun breaks down ozone, but the oxygen atoms are capable of rebonding to form ozone again.
O3(g) -->O(g) + O2(g) & O(g) + O2(g) --> O3(g)
But Chlorine atoms come and interfere with the process and will not be used up, one Chlorine atom can interfere with hundreds of oxygen molecules.
Cl(g)+O3(g) -- > ClO(g) + O2(g)
ClO(g) + O(g) --> Cl(g) + O2(g)