Most of the stratospheric ozone is produced at tropical latitudes, but high altitude winds spread it over the whole planet. It is continually forming and breaking down, and its distribution over the planet is not uniform or constant. Instead, there are seasonal and longer term variations in the quantity of stratospheric ozone in different parts of the world. However, over the long run the natural processes of formation and breakdown are balanced, it is only in recent decades that human activities have led to ozone being destroyed much faster than it can be formed, thereby creating the ozone hole that exists today. Ozone can also be formed at ground level to produce photochemical smog and, as ozone is a toxic gas, there is a health hazard when ozone reaches high levels. This problem occurs primarily in the summer in cities with a high amount of traffic when sunlight interacts with car exhaust fumes containing nitrogen oxides.
Technically, the term ozone hole should be applied to regions where stratospheric ozone depletion is so severe that levels fall below 200 Dobson Units (D.U.) the traditional measure of stratospheric ozone. Normal ozone concentration is about 300 to 350 D.U. Such ozone loss occurs during springtime above Antarctica, and to a lesser extent the Arctic, where special meteorological conditions and very low air temperatures accelerate and enhance the destruction of ozone loss by man-made ozone depleting…show more content… The primary chemicals involved are chlorofluorocarbons (CFCs for short), halons, and carbon tetrachloride. CFCs in particular have been used for a wide range of applications, including refrigeration, air conditioning, foam packaging and for making aerosol spray cans. Because these chemicals are so passive, they are able to stay in the atmosphere long enough to be carried upwards to the stratosphere where they can damage the ozone