The ozone layer is a zone within the upper atmosphere that acts as a UV filter protecting the Earths surface, and us from the damaging effects of ultraviolet radiation. These damaging effects in humans can include increases in the rate of skin cancer, and in living organisms in general can cause genetic mutation.
The ozone, a triple Oxygen molecule (O3 as opposed to O2) is easily combined with carbon molecules, and once depleted reforms only very slowly. It is created by the ionising effect of solar radiation as it hits the upper atmosphere. In the 1970's and '80's reports were made of the appearance of a large hole above the Antarctic icecap. The hole was at first disputed but finally demonstrated to be a real phenomena, extending to an area the size of the Australian continent. A series of scientific surveys were carried out and the official analysis reported that the most likely cause was the release of CFC's (Cloro-floro-carbon molecules) particularly used in refrigerators and in aerosol propellants.
Where this causes some controversy and a suggestion that this may not be the whole story is that there is only limited evidence of transmission of these molecules from ground level where they are produced, to the upper atmosphere where the ozone is found. Certainly it is possible that such transmission is possible, but the mechanism is not well established. However, there is strong evidence that one of the effects of the nuclear tests in the 1950's in the Nevada desert in America was that the rapidly rising mushroom cloud associated with nuclear blasts did indeed penetrate the upper atmosphere and also caused high levels of depletion of the ozone layer. This has led to a suggestion that in addition to further testing by American, French and British scientists in the South Pacific and the Australian outback there were additional experiments in the Antarctic wilderness in direct contravention of the multinational agreement to protect the Antarctic environment.
It is certainly the case that there was a tremendous need for secrecy around nuclear testing in the interest of national security, and the ability of espionage around nuclear testing through seismological studies would lead to an interest in testing in the Antarctic since it is naturally a highly seismically active region with significant volcanic activity. The question remains of whether there is evidence of experiments of this type, and whether these could be a better explanation of the ozone layer depletion. To date, many documents relating to the Manhattan project and the later nuclear testing policies have remained classified, and the only research groups active in the Antarctic are scientists funded by the governments who would have been involved with such testing and are therefore unlikely to be entirely trustworthy sources. The case is still open, but the official story lacks credibility and there are several alternatives, the most likely presented here, that bear closer investigation.