BBC: Scientists have identified four new man-made gases that are contributing to the depletion of the ozone layer.
Two of the gases are accumulating at a rate that is causing concern among researchers.
Worries over the growing ozone hole have seen the production of chlorofluorocarbon (CFC) gases restricted since the mid 1980s.
But the precise origin of these new, similar substances remains a mystery, say scientists.
Lying in the atmosphere, between 15 and 30km above the surface of the Earth,...