Potential impact of dichloromethane on the ozone layer recovery

In a study* published in Nature Communications on June 27, 2017, Ryan Hossaini and a team of researchers consider the impact of dichloromethane (CH₂CL₂) on the ozone layer.

Recent studies estimate that a recovery of the ozone layer reaching or exceeding pre-1980 values is expected to occur by the middle to the latter half of the 21st century, thanks to the measures involved by the Montreal Protocol on Substances that Deplete the Ozone Layer. Nevertheless, the Protocol does not take into account dichloromethane because it is a “very short-lived substance”.

In his study, Ryan Hossaini measured that “between 2000 and 2012, surface concentrations of CH₂CL₂ increased at a global mean rate of almost 8% per year” and that “CH₂CL₂ concentrations have doubled between 2004 and 2014”. The researchers used model simulations to consider the impact of this increase in the future. In the worst case, the authors estimate that the return of the Antarctic ozone pre-1980 levels could be delayed by 30 years.

Dichloromethane is used in many industrial applications as a solvent, but also as a feedstock in the production of the HFC refrigerant R32. Nature’s article does not mention the refrigerant namely, but it refers to dichloromethane as a feedstock used “in the production of other applications”. It is the reason why the European Fluorocarbons Technical Committee (EFCTC) published a position paper on July 11, 2017 estimating that the use of dichloromethane “as a feedstock for HFC32 production is insignificant in the context of the scenarios presented in the Hossaini paper, and this use will have essentially no impact on the recovery of the ozone layer”.

*Hossaini R. et al. The increasing threat to stratospheric ozone from dichloromethane. Nature Communications. 2017, article?15962. DOI: 10.1038/ncomms1596

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