Atomic chlorine, a true catalyst for ozone destruction, is released in the process. Chlorine initiates and takes part in a series of ozone destroying chemical reactions and emerges from the process unchanged. The chlorine monoxide then reacts with atomic oxygen to produce molecular oxygen and atomic chlorine. The regenerated chlorine atom is then free to initiate a new cycle. This destructive chain of reactions will continue over and over again, limited only by the amount of chlorine available to fuel the process.
Chlorine occurs naturally in the oceans.
However, the majority of chlorine in the atmosphere has originated with man-made chemicals. Without the breakdown of manufactured chlorofluorocarbons, there would be almost no chlorine in the stratosphere. Between 1975 and 1987, concentrations more than doubled from less than 200 parts per trillion by volume to more than 400 parts per trillion by volume. The amount of chlorine in the stratosphere increased by a factor of 2 to 3. Ongoing studies are essential to provide the necessary understanding of the causes of ozone depletion.