Title VI of the Clean Air Act (CAA) Amendments of 1990 reflects Congressional concern that chlorofluorocarbons (CFC), hydrochlorofluorocarbons (HCFC), brominated hydrocarbons (halons), carbon tetrachloride, methyl chloroform, and other chemicals are destroying the stratospheric ozone layer. Even though these chemicals are released in the lower atmosphere (troposphere), their life span is such that they can be transported to the stratosphere through tropospheric mixing. Once in the stratosphere, these compounds are broken down by ultraviolet radiation, producing highly reactive chlorine and bromine radicals which participate in the catalytic destruction of O3. Title VI (Sections 602-618 of the Clean Air Act, codified at 42 United States Code 7671a-q) requires the phase-out of production and consumption of ozone-depleting substances (ODS), regulates the use and disposal of ODSs, bans nonessential products containing ODSs, requires labeling of products manufactured with and containing ODSs, and regulates their replacement with substitutes so that the stratospheric concentration of chlorine and bromine can be reduced.
The CAA required the USEPA to regulate ODSs in two classes. Class I substances include CFCs, halons, carbon tetrachloride, and methyl chloroform. Class II substances are specifically listed HCFCs. USEPA is required to add substances to the Class I category if they have an ozone depleting potential (ODP) of 0.2 or greater. The ODP is a factor established by USEPA to reflect the ozone-depleting potential of a substance as compared to chlorofluorocarbon-11 (CFC-11). For Class II substances, USEPA is required to add any other substance that is known or may reasonably be anticipated to cause or contribute to harmful effects on the O3 layer. The actions detailed in Title VI carry out the United States obligations under the "Montreal Protocol on Substances that Deplete the Ozone Layer."
The Montreal Protocol is a treaty, ratified by the U.S. Senate in December 1988, limiting global production and consumption of ODSs. The Montreal Protocol, as embodied in the CAA Amendments of 1990, originally required the production of CFCs to be phased out by January 1, 2000, with the exception of methyl chloroform which had a deadline of January 2, 2002. Also, effective January 1, 2015, it would be unlawful to sell or consume Class II substances without certain restrictions, and their production would be phased out by January 30, 2030.
During 1992, the parties to the Montreal Protocol amended the treaty to reflect recent scientific information on the harmful effects caused by the destruction of stratospheric O3. The Montreal Protocol now calls for an accelerated phase-out of CFCs, methyl chloroform and carbon tetrachloride by January 1, 1996, with the exception of critical CFC uses. It called for the phase-out of halons by the end of 1993. Finally the protocol calls for the addition of methyl bromide (a broad spectrum pesticide) and hydrobromofluorocarbons (HBFC) as Class I substances with the phase-out of methyl bromide by January 1, 2001, and HBFCs by January 1, 1996. Figure 18 shows the estimated change in chlorine content in the stratosphere (a) without restrictions on releases of ozone depleting chemicals, (b) with limitations under the original Montreal Protocol of 1987, and (c) with the release limitations now internationally agreed.
The USEPA has elected to accelerate the phase-out of the three Class II HCFCs with the highest ODP: HCFC-141B, HCFC-22, and HCFC-142B. The USEPA will ban the production and consumption of HCFC-141B as of January 1, 2003, and the production and consumption of HCFC-142B and HCFC-22 by January 1, 2020. The USEPA will ban the production and consumption of all other HCFCs by January 1, 2030. The USEPA has incorporated the accelerated phase-out and additions called for by the amendments in its final rule on the protection of stratospheric O3, published in 58 Federal Register (FR) 65018-65082 (Dec. 10, 1993) and codified at 40 CFR Part 82. Ultimately, the goal is to reverse the observed reduction in global O3 and limit resulting damage to the Earth from increased UV radiation.
Figure 18: Change in Chlorine Content in Stratosphere
|(a) Without restrictions on releases of ODSs
(b) Limitations of original Montreal Protocol of 1987
(c) Release limitations now internationally agreed
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