Paris: Worried scientists said today that they had found four new ozone-destroying gases in the atmosphere, most likely put there by humans in the last 50-odd years despite a ban on these dangerous compounds.
It is the first time since the 1990s that new substances damaging to Earth's stratospheric shield have been found, and others may be out there, they said.
"Our research has shown four gases that were not around in the atmosphere at all until the 1960s, which suggests they are man-made," the team from Europe and Australia wrote in the journal Nature Geoscience.
They analysed unpolluted air samples collected in Tasmania between 1978 and 2012, and from deep, compacted snow in Greenland.
"The identification of these four new gases is very worrying as they will contribute to the destruction of the ozone layer," added a statement from the team. "We don't know where the new gases are being emitted from, and this should be investigated."
Three of the gases are chlorofluorocarbons (CFCs) - a group which includes chemicals traditionally found in air-conditioning, refrigerators and aerosol spray cans but banned under the Montreal Protocol.
The fourth is a hydro chloro fluoro carbon (HCFC), part of a closely-related group of compounds which replaced CFCs but are being phased out.
More than 74,000 tonnes of the four newly-identified gases had accumulated in the atmosphere by 2012, said the team.