The ozone is an atmospheric layer between 20 and 50 km from Earth, which absorbs UV rays form the Sun, which in high quantity could be highly dangerous for men and life on Earth in general. 

CFCs (chlorofluorocarbons) released by men in the atmosphere had caused chemical reactions between chlorine and ozone (a molecule made of three atoms of oxygen), which destroyed the ozone layer. In1987, following the Montreal Protocol, such substances became forbidden.

Over the last few years, in the scientific community it has been believed that such action is allowing the reconstruction of the ozone layer, so that forecasts claim it should set back to its levels before 1970s in a few decades.

However, a recent study shows how gases causing the greenhouse effect on our planet are considerably interfering with the reconstruction of the ozone layer and what will happen in the years to come is still unclear.