The production of chlorofluorocarbon (CFC) gases came under restriction worldwide in the mid-1980s after the compounds were found to be creating the hole above Antarctica.
A total global ban on production came into force in 2010. But researchers say the four newly discovered chemicals, also powerful greenhouse gases, may be leaking from insecticide production and from solvents used in cleaning electronic components.
Scientists now caution that many others probably exist. “They might well add up to dangerous levels, especially if we keep finding more,” said Johannes Laube at the University of East Anglia.
Since the ozone-killing chemicals take decades to break down in the atmosphere, their impact on climate and the ozone hole is long-lasting.
Writing in the journal Nature Geoscience, researchers say the three new CFCs and one hydrochlorofluorocarbon (HCFC) were detected in air bubbles trapped since the mid-1970s in the Greenland snowpack.
“I was surprised no-one had picked these up before,” said Laube.
Photo: Ozone Hole Watch