The ozone layer in the upper atmosphere absorbs harmful UV rays from the sun.

Chlorofluorocarbons (CFCs), used as refrigerants, can accumulate in the atmosphere and covert ozone (O3) to oxygen gas (O2), depleting the layer.

Since 1975 an ozone "hole" has appeared in August over the South Pole when sunlight triggers these reactions during Antarctic winter.

CFC use began to be phased out by the Montreal Protocol in 1989. Quiz