OSLO, March 9 (Reuters) - Scientists have detected four new man-made gases that damage the Earth's protective ozone layer, despite bans on almost all production of similar gases under a 1987 treaty, a study showed on Sunday.
The experts were trying to pinpoint industrial sources of tiny traces of the new gases, perhaps used in making pesticides or refrigerants, that were found in Greenland's ice and in air samples in Tasmania, Australia.
The ozone layer shields the planet from damaging ultra-violet rays, which can cause skin cancer and eye cataracts, and has been recovering after a phase-out of damaging chemicals under the U.N.'s 1987 Montreal Protocol.
"The concentrations are not yet a threat to the ozone layer," lead author Johannes Laube of the University of East Anglia in England told Reuters of the three types of CFCs (chlorofluorocarbon) and one HCFC (hydrochlorofluorocarbon).
In total, the scientists estimated more than 74,000 tonnes of the four had been released to the atmosphere. None was present before the 1960s in Greenland's ice cores, according to the study in the journal Nature Geoscience.
That is only a small fraction of the million tonnes of CFCs produced every year at a 1980s peak, according to the team of scientists in Britain, Germany, Australia, France, the Netherlands and Switzerland.