Article content continued

It was confirmed Wednesday by scientists reporting in the peer-reviewed journal Nature that industries in north-eastern China have spewed large quantities of CFC-11 into the atmosphere in violation of an international treaty.

Since 2013, emissions have increased by about 7,000 tons yearly in the area, slowing the rate at which holes in the ozone layer are repairing themselves.

“CFCs are the main culprit in depletion of the stratospheric ozone layer, which protects us from the Sun’s ultraviolet radiation,” said lead author Matt Rigby, an atmospheric chemist at the University of Bristol.

CFC-11 was used across the world in the 1970s and 1980s as a refrigerant and to make foam insulation.

The 1987 Montreal Protocol banned CFCs and other industrial aerosols that chemically dissolve protective ozone six to 25 miles above the Earth’s surface, after holes were detected over Antarctica and Australia.

Following the ban, global concentrations of CFC-11 declined steadily until about 2012. But last year scientists discovered the pace of that slowdown dropped by half from 2013 to 2017.

Because the chemical does not occur in nature, the change could only have been produced by new emissions.

Evidence pointed to east Asia, but could not nail down the exact origin.

However, monitoring stations reported significant “spikes” in pollution when air arrived from industrialised areas in China.

Although China has taken some action to crack down on firms illegally manufacturing CFC-11, closing down the practice will not be easy.

CFC-11 is cheaper and more effective than alternatives and there are many thousands of firms making foams for China booming construction industry.

“The most critical thing the government needs to do now is to track down and shut down all CFC-11 production, said Ms Perry.

“This will involve high-priority large-scale sustained intelligence-led enforcement efforts on the part of China, something we have yet to see evidence of.”