NASA images show new threat to the ozone layer from chlorocarbons

Increasing emissions of harmful chemicals are threatening the recovery of the ozone layer, undoing decades of progress.

The new threat comes from chemicals that are predominantly being emitted by China, as the country's industry and economy continues to grow.

The substances are used for everything from paint stripping and agriculture, to the production of pharmaceuticals and PVC.

Researchers say their continued use could delay the closing of the ozone hole by up to 30 years.