Ozone-Depleting Substances in the 2015 TRI National Analysis
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In the 1970s, scientists concluded that chlorofluorocarbons (CFCs) were depleting the stratospheric ozone layer. The ozone layer in the stratosphere protects life on Earth from the harmful effects from the sun’s radiation. This concern about the damage to the ozone layer led to a ban on using CFCs as aerosol propellants. However, in the 1980s, consumption of CFCs continued to increase. Through an international agreement on the Protection of the Ozone Layer and the adoption of the Montreal Protocol on Substances that Deplete the Ozone Layer (Montreal Protocol) countries agreed to phase out production and consumption of ozone-depleting substances (ODS). All countries recognized by the United Nations have ratified the Montreal Protocol. Visit EPA’s Ozone Protection website for more information.
Ozone-depletion potential (ODP) represents the ratio of calculated ozone column change for each mass unit of a gas emitted into the atmosphere relative to the calculated depletion for the gas.
Global warming potential (GWP) represents how much a given mass of a chemical contributes to global warming over a certain time period compared to the same mass of carbon dioxide.
ODS have lifetimes in the atmosphere long enough to allow them to be transported by global winds into the stratosphere. There, they release chlorine or bromine when they break down, and these chlorine and bromine atoms damage the protective ozone layer.
Congress added two categories of ODS, designated as class I and class II, to the Clean Air Act Amendments in 1990. Many class I and class II ozone-depleting substances are included on the Toxics Release Inventory (TRI) chemical list and, hence, the quantities released to the environment or otherwise managed as waste are reportable to EPA’s TRI Program. As shown in the tables below, many ODS also have high global warming potential (GWP).
- Class I ODS
Releases of CFCs and other class I ODS, such as methyl chloroform, carbon tetrachloride, and halons come from use as refrigerants, solvents, foam blowing agents, fire suppression agents and in other applications. The production and import of class I ODS have been phased out1, though they may still be recovered from existing appliances, reclaimed to industry standards and reused. Class I substances have a higher ozone depletion potential and have been completely phased out in the U.S.; with a few exceptions, this means no one can produce or import class I substances.
EPA regulations issued under the Clean Air Act phaseout the production and import of ozone-depleting substances (ODS), which meet all the reduction targets agreed to under the Montreal Protocol. The U.S. phaseout has operated by reducing in stages the amount of ODS that may be legally produced and imported into the U.S. The ban on production and import of halons took effect January 1, 1994. The ban on production and import of other class I ODS-excluding methyl bromide-took effect on January 1, 1996. Methyl bromide was phased out on January 1, 2005 with exemptions for critical uses and quarantine and preshipment.
Class I Ozone-depleting Substances TRI Chemical Name CAS RN ODP2 GWP3 CFC-11 Trichlorofluoromethane 75-69-4 1 4,750 CFC-12 Dichlorodifluoromethane 75-71-8 1 10,900 CFC-13 Chlorotrifluoromethane 75-72-9 1 14,420 CFC-113 Freon 113 76-13-1 0.8 6,130 CFC-114 Dichlorotetrafluoroethane 76-14-2 1 10,000 CFC-115 Monochloropentafluoroethane 76-15-3 0.6 7,370 Halon 1211 Bromochlorodifluoromethane 353-59-3 3 1,890 Halon 1301 Bromotrifluoromethane 75-63-8 10 7,140 Halon 2404 Dibromotetrafluoroethane 124-73-2 6 1,640 CCl4 Carbon tetrachloride 56-23-5 1.1 1,400 Methyl chloroform 1,1,1-trichloroethane 71-55-6 0.1 146 Methyl bromide Bromomethane 74-83-9 0.7 5
1 Under the phaseout there is a limited exception for production and import of controlled substances that are transformed or destroyed. Importers can also petition EPA to import used ODS.
2 The numbers in this column represent ODP values from Annex A-E of the Montreal Protocol on Substances that Deplete the Ozone Layer. Some numbers have been updated through amendments to the Protocol.
3 The numbers in this column represent GWP values from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report: Climate Change 2007 (AR4). The values listed are for direct radiative forcing and can be found in Table 2.14 of the “Physical Science Basis” contribution to the report.
- Class II ODS
Hydrochlorofluorocarbons (HCFCs) are class II ODS that are less damaging to the ozone layer than class I substances, and are currently being phased-out consistent with the Clean Air Act and Montreal Protocol. HCFCs were developed as transitional substitutes from class I substances and are subject to a later phaseout schedule than class I substances. Historically, the most widely used HCFCs were HCFC-22, used as a refrigerant, HCFC-141b, used as a solvent and foam-blowing agent, and HCFC-142b, used as a foam-blowing agent and component in refrigerant blends. The table below shows the phaseout schedule for HCFCs.
U.S. Action to Meet the Montreal Protocol Phaseout Schedule for Class II Year to Be Implemented Implementation of HCFC Phaseout through Clean Air Act Regulations Percent Reduction in HCFC Consumption and Production from Baseline 2003 No production or import of HCFC-141b 35.0% (2004) 2010 No production or import of HCFC-142b and HCFC-22, except for use in equipment manufactured before January 1, 2010 75.0% 2015 No production or import of any other HCFCs, except as refrigerants in equipment manufactured before January 1, 2020 90.0% 2020 No production or import of HCFC-142b and HCFC-22 99.5% 2030 No production or import of any HCFCs 100.0% Class II Ozone-depleting Substances TRI Chemical Name CAS RN ODP4 GWP5 HCFC-21 Dichlorofluoromethane 75-43-4 0.04 151 HCFC-22 Chlorodifluoromethane 75-45-6 0.055 1,810 HCFC-121 1,1,2,2-tetrachloro-1-fluoroethane 354-14-3 0.01-0.04 100 HCFC-123 2,2-dichloro-1,1,1-trifluoroethane 306-83-2 0.02 77 HCFC-123a 1,2-dichloro-1,1,2-trifluoroethane 354-23-4 77 HCFC-123b 1,1-dichloro-1,2,2-trifluoroethane 812-04-4 77 HCFC-124 2-chloro-1,1,1,2-tetrafluoroethane 2837-89-0 0.022 609 HCFC-124a 1-chloro-1,1,2,2-tetrafluoroethane 354-25-6 609 HCFC-132b 1,2-dichloro-1,1-difluoroethane 1649-08-7 0.008-0.05 100 HCFC-133a 2-chloro-1,1,1-trifluoroethane 75-88-7 0.02-0.06 100 HCFC-141b 1,1-dichloro-1-fluoroethane 1717-00-6 0.11 725 HCFC-142b 1-chloro-1,1-difluoroethane 75-68-3 0.065 2,310 HCFC-225ca 3-3,dichloro-1,1,1,2,2-pentafluoropropane 422-56-0 0.025 122 HCFC-225cb 1,3-dichloro-1,1,2,2,3-pentafluoropropane 507-55-1 0.033 595 HCFC-253 3-chloro-1,1,1-trifluoropropane 460-35-5 0.003-0.03
4The numbers in this column represent ODP values from Annex A-E of the Montreal Protocol on Substances that Deplete the Ozone Layer. Some numbers have been updated through amendments to the Protocol.
5The numbers in this column represent GWP values from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report: Climate Change 2007 (AR4). The values listed are for direct radiative forcing and can be found in Table 2.14 of the “Physical Science Basis” contribution to the report.
This page was published in January 2017 and uses the 2015 TRI National Analysis dataset made public in TRI Explorer in October 2016.