Volcanoes don't inject significant chlorine into the stratosphere but they do increase small particles, which increase the amount of polar stratospheric clouds with which the human - made chlorine reacts. (sciencedaily.com)
Polar stratospheric clouds (PSCs) play a key role in stratospheric ozone depletion. (science.sciencemag.org)
Those techniques have led to everything from the development of catalysts that remove poisonous carbon monoxide from car exhaust to the understanding of how ice crystals in stratospheric clouds supercharge atmospheric chlorine's ability to destroy the planet's protective ozone layer. (sciencemag.org)