Ozone-depleting emissions have more than doubled in China

Emissions from China of the ozone-destroying chemical, dichloromethane, have more than doubled over the last decade, according to researchers.

Since the signing of the Montreal Protocol, there has been a dramatic drop in emissions of the main substances that are responsible for depleting the stratospheric ozone layer. 

However, recent calculations revealed that China’s share of total emissions grew from about one-third to two-thirds over the last decade. 

The global emissions increase since 2011 is the same size as the rise in emissions from China. 

‘We think that emissions of dichloromethane from China have increased because of its use in a solvent in various industrial applications and the expanding chlormethanes industry in China,’ said Minde An, a postgraduate student from Peking University. 

Current controls on the use of dichloromethane in China only relate to its toxicity or its role in causing urban air pollution. This means that levels of dichloromethane are regulated in consumer products but there is no control on the overall amount that can be emitted to the atmosphere. 

Historically, emission rates of dichloromethane have been small enough to not overly worry researchers studying ozone layer recovery. However, the recent rise needs to be carefully watched in future.

Dr Ryan Hossaini from the University of Lancaster, and co-author of the study, said: ‘If current levels of dichloromethane persist, we could expect to see a delay in ozone layer recovery of a few years. However, if they continue to grow at the rate we’ve seen over the last decade, it could lead to a delay of over a decade, though future emissions are highly uncertain.

‘Of significance is the location of the emissions discovered in this study. Short-lived compounds like dichloromethane are partly destroyed in the lower atmosphere before they reach the ozone layer.

‘However, in some parts of Asia, there are regions where the atmosphere can transport these substances to the stratosphere relatively quickly. This means emissions from these regions may pack a bigger punch than those released elsewhere.”

Despite these concerns, there are signs that changes may be coming. In the last month, draft regulation by the Ministry of Ecology and Environment in China listed dichloromethane as a new pollutant whose use in several sectors such as paint stripping or insulating foam production could be banned.