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Fluorocarbon Blowing Agents Effect on Ozone Depletion

In the early 1970s, researchers began to investigate the effects of various chemicals on the ozone layer, particularly CFCs, which contain chlorine. They also examined the potential impacts of other chlorine sources. Chlorine from swimming pools, industrial plants, sea salt, and volcanoes does not reach the stratosphere. Chlorine compounds from these sources readily combine with water and repeated measurements show that they rain out of the troposphere very quickly. In contrast, CFCs are very stable and do not dissolve in rain. Thus, there are no natural processes that remove the CFCs from the lower atmosphere. Over time, winds drive the CFCs into the stratosphere. The CFCs are so stable that only exposure to strong UV radiation breaks them down. When that happens, the CFC molecule releases atomic chlorine. One chlorine atom can destroy over 100,000 ozone molecules. The net effect is to destroy ozone faster than it is naturally created. To return to the analogy comparing ozone levels to a stream's depth, CFCs act as a siphon, removing water faster than normal and reducing the depth of the stream. 

U.S. EPA Ozone Depletion

International Scientific Assessments of Ozone Depletion. An international agreement known as the "Montreal Protocol on Substances That Deplete the Ozone Layer" was reached in 1987. Through that agreement, and subsequent amendments and adjustments in 1990 and 1992 and adjustments in 1995 and 1998, many nations of the world have carried out policies to reduce and then phase out their use of ozone-depleting chemicals. The Montreal Protocol also called for the international scientific community to periodically update governments on the latest scientific findings related to the ozone layer. Conducted under the auspices of the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) and co-sponsored by NASA, NOAA, and other organizations, these periodic "state-of-the-science" assessments have guided policymakers as they strengthened the original provisions of the Montreal Protocol. Together with colleagues at NASA, other NOAA laboratories, and other scientific institutions across the U.S. and around the world, CSD (formerly the Aeronomy Laboratory) has played a leading role in preparing these assessments (1985, 1988, 1991, 1994, 1998, and 2002). The Executive Summary of the most recent assessments (1994, 1998, and 2002) are available here.

CSD International Ozone-Layer Assessments