Scientists have made a "very worrying" discovery of four new ozone-destroying gases.

The research from scientists at the University of East Anglia was published Sunday in the journal Nature Geoscience.

By comparing current air samples with air samples from "polar firn" snow in Greenland, perennial snowpack which offers archival information, the researchers discovered three chlorofluorocarbons (CFCs) and one new hydrochlorofluorocarbon (HCFC).

The Montreal Protocol, signed in 1987, banned CFCs and set phase-out deadlines for HCFCs. "This has resulted in successfully reducing the production of many of these compounds on a global scale," stated lead author Dr. Johannes Laube from UEA’s School of Environmental Sciences. "However, legislation loopholes still allow some usage for exempted purposes."

"The identification of these four new gases is very worrying as they will contribute to the destruction of the ozone layer," Laube stated.

They also found that two of the four gases are significantly increasing.

"What’s more, the three CFCs are being destroyed very slowly in the atmosphere—so even if emissions were to stop immediately, they will still be around for many decades to come," he added.

The scientists estimate that over 74,000 tonnes of the combined chemicals were released before 2012, though the source is unclear. Because they were not present in the atmosphere until the 1960s, the researchers believe they are human-made.

"We don’t know where the new gases are being emitted from and this should be investigated. Possible sources include feedstock chemicals for insecticide production and solvents for cleaning electronic components."

Piers Forster, a professor from the University of Leeds who was not involved in the study, said the new research shows that "ozone depletion is not yet yesterday's story."

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