Ultraviolet radiation causes many health problems, including cancer. A layer of ozone in the atmosphere protects living things from ultraviolet radiation.
A break, or hole, in the ozone layer exists over the southern polar region of Earth. This hole allows ultraviolet light from the Sun to reach Earth undiluted by ozone.
Some scientists and environmentalists claim that this hole is growing as a result of pollution.
It has only been recently studied, however, so others believe its expansion is probably a natural event.
The hole in the ozone is over a barren region of Earth, but imagine if it were to grow so large as to cover populated areas.