You're confusing the solids with the main engines.
"SRB" is the solid rocket booster, and among their exhaust products are chlorine compounds (don't remember which ones.) I don't know how much they affect the ozone layer. I suspect the low number of launches would have a negligible effect. A NASA statement on this is here.
The Shuttle main engines (SSMEs) do, as you say, exhaust only mostly water vapor. I suspect the heat of the exhaust generates a tiny amount of other compounds from the nitrogen and other things in the air during the early part of launch, but nothing significant.