Ozone layer continues to thin over Earth's populated areas

The ozone layer that protects us from harmful ultraviolet radiation continues to thin over populated areas of the world, a new study warns.

Scientists say the layer is in better shape, however, over the North and South Poles.

Ozone has been declining globally since the 1980s. While the banning of the chloroflourocarbons that cause the thinning is leading to a recovery at the poles, "the same does not appear to be true for the lower latitudes," study author Joanna Haigh of Imperial College in London said.

Located in the stratosphere, the ozone layer blocks potentially harmful ultraviolet energy from reaching our planet's surface. Without it, humans and animals could experience increased rates of skin cancer and other ailments. 

Scientists first discovered the dramatic thinning in Earth's protective sheet in the 1970s and determined the production of chlorofluorocarbons (CFCs), used in refrigerators and aerosol sprays, caused the anomaly. The infamous ozone hole over Antarctica was discovered in the late 1970s.

In the late 1980s, 196 countries signed the Montreal Protocol, a treaty that limited production of CFCs around the world.

The cause of the ongoing thinning is unclear, although the study authors suggest a couple of possibilities. One is that climate change is altering the pattern of atmospheric circulation, causing more ozone to be carried away from the tropics.

Another cause could be newer man-made gases that are chewing away at the ozone layer. The gases in question are known as "very short-lived substances" such as dichloromethane, which is used in a variety of industrial processes.

The naturally occurring ozone high in the atmosphere is the "good ozone" and is in contrast to the "bad ozone" near the surface, which is pollution and can cause respiratory problems.

"The potential for harm in lower latitudes may actually be worse than at the poles," Haigh said. "The decreases in ozone are less than we saw at the poles before the Montreal Protocol was enacted, but UV radiation is more intense in these regions and more people live there."

The study was published in the European Geosciences Union journal Atmospheric Chemistry and Physics.