The production of chlorofluorocarbons, which damage the ozone layer, has been banned as far as possible. However, other substances can also tear holes in the ozone layer in combination with ice particles, such as those found in clouds. Researchers at Ruhr-Universität Bochum, the University of Duisburg-Essen and Friedrich-Alexander-Universität Erlangen-Nürnberg have discovered a possible mechanism for this. They describe it in the journal Physical Review Letters on 13 November 2018.