As a Party to the Montreal Protocol on Substances that Deplete the Ozone Layer, the United States joined with other nations to phase out the production and use of ozone-depleting substances (ODSODSA compound that contributes to stratospheric ozone depletion. ODS include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), halons, methyl bromide, carbon tetrachloride, hydrobromofluorocarbons, chlorobromomethane, and methyl chloroform. ODS are generally very stable in the troposphere and only degrade under intense ultraviolet light in the stratosphere. When they break down, they release chlorine or bromine atoms, which then deplete ozone. A detailed list (http://www.epa.gov/ozone/science/ods/index.html) of class I and class II substances with their ODPs, GWPs, and CAS numbers are available.) that harm the ozone layerozone layerThe region of the stratosphere containing the bulk of atmospheric ozone. The ozone layer lies approximately 15-40 kilometers (10-25 miles) above the Earth's surface, in the stratosphere. Depletion of this layer by ozone depleting substances (ODS) will lead to higher UVB levels, which in turn will cause increased skin cancers and cataracts and potential damage to some marine organisms, plants, and plastics. The science page (http://www.epa.gov/ozone/science/index.html) offers much more detail on the science of ozone depletion.. EPA continues to work with stakeholders to coordinate global and national efforts to protect the ozone layer:

• EPA participates in international forums to help refine the Montreal Protocol and related treaties based on ongoing scientific assessments of ozone depletion. These assessments are coordinated by the United Nations Environment Programme Exit and the World Meteorological Organization Exit, with cooperation from EPA and other international agencies.
• EPA works with other U.S. government agencies, including the Department of Energy, Department of State, Department of Justice, Department of Homeland Security (including Customs and Border Protection and Immigration and Customs Enforcement), Department of Defense, and others, to coordinate efforts to address ozone layer depletion in the United States. This includes coordination on federal agency procurement of alternatives to high-global warming potential hydrofluorocarbons.