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An international team of researchers, led by Dr David Oram of the National Centre for Atmospheric Science, have discovered an unexpected danger to the ozone layer from chemicals that are not currently regulated. The study highlights a gap in the Montreal Protocol that may need to be addressed in the future. 

Thirty years ago, the Montreal Protocol was established to reduce the amount of long-lived ozone-depleting substances that were being released into the atmosphere. The agreement has contributed to a significant reduction in these atmospheric substances, and is widely considered to have started the slow process of healing the ozone layer. However, new research by David Oram has suggested that a number of unregulated short-lived ozone-depleting substances are dramatically increasing in abundance and could be entering the stratosphere, therefore slowing the recovery of the ozone layer. 

The substances in question were not considered damaging before because they were thought to be too short-lived to reach the upper atmosphere, where the ozone layer is located. However, the new study raises the alarm over fast-increasing emissions of some of these very short-lived chemicals in East Asia and also provides evidence for how they can potentially be carried up into the stratosphere. 

One of the threats is dichloromethane, a substance with uses varying from paint stripping to agricultural fumigation and the production of pharmaceuticals. The amount of this substance in the atmosphere decreased in the 1990s and early 2000s, but over the past decade dichloromethane became approximately 60% more abundant. The team of found both dichloromethane and dichloroethane in the air samples they collected in South East Asia. Dichloroethane is used in the production of PVC and is not only highly toxic, but also holds a significant value, so this discovery is a major surprise to the scientific community. 

You can find out more about David Oram's paper on the European Geosciences Union website, the full paper has been published in Atmospheric Chemistry and Physics.