It was first discovered in 1982 by the British Antarctic Survey, an Institute of the Natural Environmental Research Council. By 1985, it was clear that the ozone layer is destroyed over antarctic every year during spring season (September-October), having a hole in the atmosphere. Through this hole, harmful UV-Beta ray can enter into the Earth’s atmosphere.
Studies have shown that during winter, vortex of very cold air blow over the pole. So, neither sunlight nor warmer air from lower latitude enters in this vortex. The concentration of Chrlorine Monoxide (ClO) is usually very high in this vortex of cold air which is responsible for ozone destruction. But, it can not destroy ozone during this time, since ozone breakdown reactions require light, and antarctic winters are dark. With the onset of spring, sunlight returns and chlorine monoxide reacts wit ozone breaking it down to oxygen. Under certain conditions, one molecule of ClO can destroy 10,000 to 1000,000 Ozone molecule.