CFCs and other molecules have mainly eroded ozone in the upper stratosphere, and over the poles. (Photo: Representational/Pixabay)

Paris: Industries in northeastern China have spewed large quantities of an ozone-depleting gas into the atmosphere in violation of an international treaty, scientists said Wednesday.

Since 2013, annual emissions from northeastern China of the banned chemical CFC-11 have increased by about 7,000 tones, they reported in the peer-reviewed journal Nature. "CFCs are the main culprit in depletion of the stratospheric ozone layer, which protects us from the Sun's ultra-violet radiation," said lead author Matt Rigby, an atmospheric chemist at the University of Bristol.

 Chlorofluorocarbon-11 was widely used 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 10-to-40 kilometres (6-25 miles) above Earth's surface, especially over Antarctica and Australia.