The main contributors to ozone depletion from rocket emissions are gaseous chlorine and soot particles. Chlorine catalytically destroys ozone molecules, while soot particles warm the middle atmosphere, accelerating ozone-depleting chemical reactions.
While most rocket propellants emit soot, chlorine emissions primarily come from solid rocket motors. Currently, the only propulsion systems that have a negligible effect on the ozone layer are those which use cryogenic fuels such as liquid oxygen and hydrogen. However, due to the technological complexity of handling cryogenic fuels, only about 6% of rocket launches currently use this technology.
I wonder how methalox engines perform when it comes to soot emissions, given that most modern rocket designs seem to be heading that way?