Proc. Nadl. Acad. Sci. USA Vol. 89, pp. 807-811, February 1992 Colloquium Paper

This paper was presented at a colloquium entled "Industrial Ecology," organized by C. Kumar N. Patel, held May 20 and 21, 1991, at the National Academy of Sciences, Washington, DC. Investigations of the environmental acceptability of fluorocarbon alternatives to chlorofluorocarbons MACK MCFARLAND E. I. Du Pont de Nemours & Co., Inc., Fluorochemicals, B-13230, Wilmington, DE 19898

ABSTRACT Chlorofluorocarbons (CFCs) are currently ing appropriate boiling points, low vapor-phase thermal con- used in systems for preservation of perishable foods and ductivity, desirable solubility characteristics, and high sta- medical supplies, increasing worker productivity and con- bility, which makes them compatible with many construction sumer comfort, conserving energy and increasing product materials. reliability. As use of CFCs is phased out due to concerns of The environmental concerns over CFCs, their potential to ozone depletion, a variety of new chemicals and technologies contribute to ozone depletion (1), stem from the same prop- will be needed to serve these needs. In choosing alternatives, erties that make them desirable from an applications and industry must balance concerns over safety and environmental worker and consumer safety viewpoint. Their vapor pres- acceptability and still meet the performance characteristics of sures are high enough that they eventually escape to the the current CFC-based products. About 60% ofprojected CFC atmosphere. Because of their stability, they are resistant to demand will either be eliminated by improved conservation decomposition in the lower part ofthe atmosphere-there are practices or will be satisfied by nonfluorocarbon alternatives. no known destruction mechanisms for CFCs in the tropo- With current technology, the only viable alternatives meeting sphere. Thus, they will remain in the troposphere until the safety, performance, and environmental requirements for transported to the stratosphere, where they are decomposed the remaining 40% of demand are fluorocarbons, hydrochlo- by solar UV radiation. The estimated atmospheric lifetimes rofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). of various CFCs range from 50 to 400 years. HCFCs and HFCs possess many of the desirable properties of It is the chlorine (bromine in the case of halons) released the CFCs, but because of the. hydrogen, they react with in the decomposition that is the cause for concern. Through hydroxyl in the lower atmosphere. This results in shorter a series ofcatalytic reactions, the chlorine can destroy ozone. atmospheric lifetimes compared to CFCs and reduces their If too much chlorine is added to the the natural potential to contribute to stratospheric ozone depletion or stratosphere, global warming; HFCs do not contain chlorine and have no balance ofproduction and destruction can be shifted, leading potential to destroy ozone. This paper provides an overview of to a net reduction in the total amount of ozone. Since ozone challenges faced by industry, regulators, and society in general acts as a filter to remove much of the solar UV-b radiation, in continuing to meet societal needs and consumer demands if other factors such as cloudiness remain constant, ozone while reducing risk to the environment without compromising decreases would lead to an increase in UV-b radiation at the consumer or worker ground. Although many uncertainties remain regarding po- safety. tential effects, increase in UV-b could lead to adverse effects on plants and animals. Chlorofluorocarbons (CFCs) have proved to be one of the Information contained in the International Ozone Trends more useful classes ofcompounds ever developed because of Panel Report (2) and supported by more recent information their chemical stability and desirable physical properties. including the ozone trend results from analysis of the Total Originally developed in the 1930s as safe alternative refrig- Ozone Mapping Spectrometer (TOMS) data (3) provides erants, their applications have expanded to include air con- compelling evidence that production and use of CFCs should ditioning, cleaning of electronic and mechanical components be phased out to reduce risk of ozone depletion. In 1990 the to ensure reliability, and expansion of plastics for energy- Montreal Protocol, an international agreement regarding efficient foam insulation. The results ofthese applications are CFC production and use, was strengthened to require a products and services that meet basic societal needs and phaseout of production in developed countries by 2000 and consumer demands. Refrigeration allows the storage and by 2010 in developing countries. distribution of perishable foods and medicines-75% of the CFC emissions also contribute to future global warming. U.S. food supply requires refrigeration somewhere in the Depending on the basis for the calculation, CFCs have production and distribution chain. Air conditioning increases accounted for 12-25% of the total contribution due to human worker productivity and consumer comfort and, in hospitals, activities. Given concerns over the potential effects of global it can save lives. Reliability of communications equipment warming, it is prudent to strive for reductions in contributions and navigation and control instrumentation are critical to from the options chosen to meet future CFC demand. society. Energy efficiency helps conserve valuable natural The challenge to industry, regulators, and society in gen- resources. eral is continuing to meet societal needs and consumer CFCs promote worker and codsumer safety because they demands with goods and services while reducing risk to the are nonflammable, noncorrosive, nonexplosive, and very environment and without compromising consumer or worker low in toxicity. They are used in such a wide variety of safety. Too often there has been a focus on only one aspect applications because of desirable physical properties includ- Abbreviations: CFC, chlorofluorocarbon; HFC, hydrofluorocarbon; The publication costs of this article were defrayed in part by page charge HCFC, hydrochlorofluorocarbon; ODP, ozone-depleting potential; payment. This article must therefore be hereby marked "advertisement" GWP, global-warming potential; AFEAS, Alternative Fluorocar- in accordance with 18 U.S.C. §1734 solely to indicate this fact. bons Environmental Acceptability Study.

807 Downloaded by guest on October 1, 2021 808 Colloquium Paper: McFarland Proc. Natl. Acad. Sci. USA 89 (1992) of the issue with demands for perfection in that area without for the CFCs and their alternatives in the United States under regard for the others. This single issue approach can lead to the amended Clean Air Act of 1990. solutions that prove to be unacceptable with respect to other Nonfluorocarbon substitutes include chemical substitutes issues. The key to success in meeting the challenge is striving outside the fluorocarbon family as well as new technologies for continuous improvement in minimizing safety, health, not requiring a chemical alternative to meet a consumer and environmental risks. demand. About 20o of global CFC production in 1986 was However, since it would be impossible to get agreement on used for aerosol propellants. Most ofthis use will probably be weighting factors to compare, for example, a worker or converted to hydrocarbons or pumps, as was done in the consumer safety risk with a global environmental risk, the United States and some other countries in the 1970s. Some risks must be evaluated individually for each alternative in cleaning agent applications and most of the use as a blowing each application. Decision makers must then choose among agent for noninsulating foams will be converted to alterna- the options based on societal norms to providejudgement for tives outside the fluorocarbon family of compounds. balancing the risks. For the cases of safety and health risks, In the remaining applications, representing =40% of pro- many criteria have already been established by society jected demand, compounds with properties very similar to through mechanisms such as regulation or liability laws. those ofthe CFCs will be needed to allow a CFC phaseout by Society is only now beginning to establish criteria for the 2000. Technology for refrigeration, insulation, and cleaning global environmental issues. applications has developed around the properties of the In addition to the safety, health, and environmental issues, CFCs. The fastest and most economical way to accommodate other constraints limiting the available options must be the phaseout is through use of compounds with similar properties. Other compounds in the fluorocarbon family evaluated. These constraints include the need for global provide the best alternative. The HCFCs and HFCs retain compliance, the rate of development and implementation of many of the properties of CFCs, but, because they contain new technology, and the need to encourage investment in the hydrogen, they decompose in the lower atmosphere. This technologies that will allow a rapid phaseout of CFCs. decomposition shortens their lifetime compared to CFCs and This paper provides an overview of some of the programs reduces their potential to contribute to ozone depletion (the under way to provide decision makers with information to HFCs do not contain chlorine or bromine and have no help ensure that there is a continuous improvement in ben- potential to deplete ozone) and global warming. The HCFCs, efits to society as CFCs are phased out. Most of the discus- like the CFCs, contain both chlorine and fluorine and, hence, sion will focus on the application of alternatives in the their properties are most similar to those of the CFCs. The fluorocarbon family. HFCs contain fluorine and have somewhat similar proper- ties. Two HCFCs, HCFC-22 and HCFC-142b, have been Technical Options commercially available for some time. Other HCFCs and some HFCs are or will soon be produced in commercial Technical options for reducing demand for CFCs are con- quantities. sidered in four categories: conservation, nonfluorocarbon (or For each application, manufacturers of consumer and not-in-kind) substitutes, hydrofluorocarbons (HFCs), and industrial products currently using CFCs are evaluating the hydrochlorofluorocarbons (HCFCs). Du Pont's estimate of available options. To remain competitive, their goal must be the extent to which each ofthese options will be implemented to choose the option that will best satisfy the needs of their is shown in Fig. 1. These estimates show the fraction of the customer. demand that would be captured by each option in the year 2000 based on projections of 1986 CFC use patterns and Health and Safety knowledge of the options and world market. Conservation includes improved design and maintenance Toxicological data on the alternative fluorocarbons are being of refrigeration and air conditioning equipment to prevent developed under cooperative research efforts sponsored by leaks, recovery of refrigerant during servicing of that equip- 15 fluorocarbon producers. The Programs for Alternative ment, and recovery and recycling of material used for clean- Fluorocarbon Toxicity Testing (PAFT) are and will continue ing. These improved practices are being implemented for to provide the data that will be necessary to determine safe CFCs and it is logical that they would be continued for the operating and handling procedures for the fluorocarbons in alternatives as well. In fact, improved practices are required each application. Testing for the seven compounds under evaluation is in various stages of completion. Results to date NON-FLUOROCARBON are promising. In the introduction to an interim report 47X A prepared by the Office of Toxic Substances of the U.S. CONSERVATION Environmental Protection Agency (4), the Assistant Admin- i 12X istrator states: Because many of these chemicals are not yet in com- merce and are still undergoing toxicity testing, the assessment rests on incomplete data and, therefore, should not be interpreted as a final judgement. None- theless, the results of these preliminary analyses indi- cate that HCFCs and HFCs can be used in a manner HFC safe to workers, consumers, and the general population 17% given appropriate technological changes and exposure control practices. FIG. 1. Current estimate of how CFC demand could be satisfied in year 2000. About 60% of future demand can be met through Other health and factors include and increased conservation measures (practices which actually decrease safety flammability overall demand for new production) and use of nonfluorocarbon the potential for formation of toxic compounds as a result of alternatives. The only viable options for meeting the remaining 40% decomposition of the HCFCs and HFCs while in use. A ofdemand for societal needs and consumer demands in the year 2000 significant advantage of the CFCs for many applications is are HCFCs and HFCs. that they are nonflammable. Most of the HCFCs and HFCs Downloaded by guest on October 1, 2021 Colloquium Paper: McFarland Proc. Natl. Acad. Sci. USA 89 (1992) 809 are nonflammable, but a few of them and most of the lead to formation of photochemical oxidants in the region of nonfluorocarbon alternatives are flammable. For some ap- their release. On a global scale, emissions of HCFCs and plications where processes and equipment can be modified to HFCs are small (<0.1%) compared to natural emissions of reduce the risk of fire or explosion or where the risk of fire ozone precursors (hydrocarbons). is already negligible, the flammable alternatives can be used Current information suggests that degradation products of safely. Studies are under way to determine risks and neces- the HCFCs and HFCs should not lead to environmental sary process changes to ensure that safety standards can be concerns. The ultimate products are expected to be carbon maintained in the transition away from CFCs. dioxide, water, and water-soluble acids. Compared to natural The HCFCs and HFCs are more susceptible to decompo- sources of acidity to the atmosphere, the contribution of the sition during use than the CFCs. In some applications, it is fluorocarbon decomposition products is negligible (<0.1%). possible for toxic decomposition compounds to be formed. There is some remaining uncertainty regarding the degrada- This possibility is being investigated by application and, tion mechanisms and the fate of some of the potential where necessary, process modifications are being made to products and projects are under way to resolve these. ensure that concentrations ofdecomposition products remain The HFCs contain no chlorine (or bromine) and, hence, at acceptable levels. have no potential to deplete ozone. The HCFCs do contain In many cases, safety and health standards for workers and chlorine, but, because they can decompose in the lower consumers are set by society through mechanisms such as atmosphere before reaching the stratosphere, their potentials existing regulations and product liability laws. Partly because to deplete ozone are significantly lower than those of the of the high visibility of the CFC/ozone issue, the health and CFCs they are targeted to replace. The ODPs of the HCFCs safety aspects ofthe alternative fluorocarbons are being more under evaluation are only 2-15% of values for the CFCs. carefully scrutinized than any similar products in history. The Furthermore, because of their relatively short atmospheric data required for decisions to ensure that product safety meets lifetimes, they are removed from the atmosphere in -1/10th or exceeds current standards are or soon will be available. the time of the CFCs. Reversal of ozone depletion caused by man-made chlorine Environmental Concerns compounds can be achieved only through reductions in In cooperation with government programs, the industry- concentrations of atmospheric chlorine contributed by these sponsored Alternative Fluorocarbons Environmental Ac- compounds. With global compliance to the CFC phaseout, a ceptability Study (AFEAS) is generating the scientific infor- transition from CFCs to HCFCs at the anticipated use rate mation required as a basis forjudging environmental accept- will lead to decreases in these concentrations and decreases ability of the HCFCs and HFCs. The state of knowledge as in the risk of ozone depletion. A sensitivity study by Prather discussed in a 1989 international scientific assessment (5) was and Watson (7) demonstrated that declines in chlorine con- summarized by scientists serving as advisors at a 1989 United centrations occurred over a wide range of substitution rates Nations Environment Programme (UNEP) meeting (6): of HCFCs for CFCs. Fig. 2 shows results from a Du Pont All information to date suggests that the proposed sub- Original protocol stitutes are significantly much better than the current CFCs relative to protection ofthe ozone layer. The ODPs 6 -,,/ QL / /Continued growth [ozone depleting potentials] and GWPs [global warming CL potentials] are much smaller than those forthe CFCs, and they should not contribute to tropospheric ozone or acid 0 4- deposition. Consequently, industry is scientifically justi- 0 Noncompliance .O 3 / Use of HCFCs as \ \ by nonsignatories fied in proceeding rapidly towards the commercialization o transitional compounds of these chemicals. E1 However, there are gaps in the scientific knowledge, and E There should be an accelerated research program to ensure the environmental acceptability of all of the 2000 2025 2050 2075 2100 proposed HCFCs and HFCs. Year The proposed research program is under way. Recent FIG. 2. Concentrations of atmospheric chlorine in forms that can results do not change the conclusions reached in 1989. reach the ozone layer are projected based on four assumptions of All known potential effects that might result from atmo- future use of man-made compounds. The top curve is based on the emissions of the HCFCs and HFCs are being eval- assumption ofglobal compliance to the original terms ofthe Montreal spheric Protocol-a 50% reduction in use in developed countries. The basis uated. There are five categories: (i) their potential to affect for the bottom curve is assumption of global compliance to a rapid tropospheric ozone; (ii) how the compounds degrade in the phaseout of CFCs (complete in developed countries by 2000 and by atmosphere; (iii) the potential environmental effects of the 2010 in developing countries) and use of HCFCs as transitional degradation products in air, water, and soil; (iv) their poten- compounds (phaseout between 2020 and 2040) to meet growing tial to affect stratospheric ozone; and (v) their potential to demands with the substitution rate shown in Fig. 1. The "Continued contribute to future global warming. growth in HCFC use" curve is based on the assumptions as de- Emissions ofHCFCs and HFCs will not significantly affect scribed for the bottom curve except that use of HCFCs to meet tropospheric ozone. Although the HCFCs and HFCs do growing demands (-3%/year compounded growth) continues in the lower through reaction with through 2100. The "noncompliance" curve is also based on assump- degrade atmosphere tions similar to the bottom curve except HCFCs are phased out by hydroxyl, their reaction rates with hydroxyl are slow enough 2020 by current signatories to the Montreal Protocol and, due to that their atmospheric lifetimes are longer than a year. Thus, uncertainty over availability of HCFCs, current nonsignatories con- emissions of the compounds would disperse before signifi- tinue use of CFCs until 2030 to meet needs that could otherwise be cant reaction that could lead to production of photochemical met by HCFCs. The line at 2 ppb indicates approximate chlorine oxidants (smog). Some of the nonfluorocarbon alternatives, concentrations in the ozone layer when the Antarctic ozone hole however, are sufficiently reactive that their emissions can began to develop. Downloaded by guest on October 1, 2021 810 Colloquium Paper: McFarland Proc. Natl. Acad. Sci. USA 89 (1992) market-based analysis. Continued use of CFCs, even with the global cooperation, the rate of development and implemen- 50% production and use reductions under the original control tation of new technology, and the need to encourage invest- provisions of the Montreal Protocol, would lead to steady ment in the technologies that will allow a rapid, global increases in chlorine amounts. With a global transition from phaseout of CFCs. Regulations formulated without regard to CFCs to options including HCFCs, atmospheric chlorine these limitations can be counterproductive in that they could begins to decrease. If there is continued growth beyond about result in increased risks. the year 2030 in the use rate of HCFCs, however, chlorine CFCs are used in and emitted to the atmosphere from every concentrations could eventually increase. This leads to a country. Since they are rapidly dispersed throughout the continuous improvement goal of using HCFCs as transition lower part of the atmosphere after emission, the potential of compounds to allow rapid global phaseout of CFCs and time a CFC to deplete ozone is independent of the location of its to find and develop other safe alternative technologies with emission. Thus, global compliance to a CFC phaseout is no potential to deplete ozone. essential to reducing the risk of ozone depletion. The CFC phaseout will lead to decreases in direct contri- To date, developing countries accounting for -10% oftotal butions to future global warming. Tropospheric decomposi- 1986 CFC consumption have not signed the Montreal Proto- tion of HCFCs and HFCs limits their accumulation in the col. CFC markets in these countries are in a rapid growth atmosphere and reduces their GWPs as compared to CFCs. stage with recent growth rates exceeding 10% per year. The On average, the GWPs of the HCFCs and HFCs are -1/10th result of continued use of CFCs to meet these growing those of the CFCs they are targeted to replace. With this demands is shown in Fig. 2. Atmospheric chlorine concen- improvement in GWPs and about a 40o substitution rate, the trations and the risk of ozone depletion will continue to transition from CFCs will lead to reductions of >90% in direct increase. contributions to future global warming from fluorocarbons. Decisions made within developed countries as well as Since the nonfluorocarbon substitutes have very low GWPs international agreements must encourage developing coun- (<1% of CFC GWPs), their use as alternatives will not lead to tries to use alternatives to CFCs. These countries do not have significant direct contributions to future global warming. the economic or technology base to allow a rapid series of A less recognized, but equally important, role of the CFCs transitions to expensive alternative technologies. Further- with respect to global warming is their indirect effect due to more, they have immediate concerns such as preservation of energy efficiency. CFCs have been used in many refrigera- food by refrigeration. Instead of transitioning to more costly tion, insulation, and cleaning agent applications because their technologies that may soon become obsolete, they may use results in lower energy consumption compared to other choose to continue use of the 60-year-old CFC technology. options. Since, in most cases, carbon dioxide-the major Since the Montreal Protocol was available for ratification at contributor to future global warming-is a by-product of least six CFC plants have started up or are under construction energy generation, energy efficiency plays an important role in developing countries. Overly restrictive regulations on in reducing contributions to future global warming. Thus, it HCFCs in developed countries would limit alternative op- is important to evaluate both the direct and indirect contri- tions in developing countries and could prolong use of CFCs. butions of alternatives to CFC to global warming. As pointed out earlier, HCFCs should be considered transi- A refrigerator/freezer provides an illustration of the impact tion compounds to allow a rapid phaseout of CFCs. If the of energy efficiency. Use and disposal of a typical United transition time is set too short and developing countries reject States refrigerator/freezer can result in emission of three HCFCs in favor of CFCs to avoid two transitions (CFCs to gases that contribute to future global warming. Carbon di- HCFCs to the as-yet-unidentified next generation of alterna- oxide is emitted in generating the electricity to run the tives), the risk of ozone depletion will continue to increase. appliance. Upon disposal, the refrigerant and the gas used to The rate at which new technologies can be developed and expand the energy-efficient insulating foam (the blowing implemented is the second constraint. Experience shows that agent) can escape to the atmosphere. Currently, the CFC the time required for development, from invention to wide- refrigerant and blowing agent contribute <20% and the spread use, of new product technology is at least 20 years and carbon dioxide contributes >80% to the total. Extrapolating often >30 years. The transition from CFCs to HCFCs and these results to refrigerator/freezers using the HCFC and HFCs provides an example of a transition requiring relatively HFC alternatives and assuming no change in energy effi- minor changes in use technology because of the similarities ciency, the carbon dioxide contribution is >98%. Thus, a 2% of the compounds. Manufacturers began the search for drop in efficiency would result in a greater contribution to alternatives when a potential need was identified in the global warming than the direct contribution of the HCFC and mid-1970s. The transition from CFCs to alternatives, includ- HFC alternatives. Even though the impact of energy effi- ing the HCFCs, is scheduled for completion by 2000. Taking ciency is less dramatic in most other applications, this into account the 5-year lapse in development in the early example does illustrate the need for careful analysis as the 1980s, the transition time will be -20 years, even at the basis for decisions to minimize global warming contributions. current accelerated schedule. The transition from HCFCs to The U.S. Department of Energy and AFEAS are cofunding as-yet-unidentified technologies is likely to be more difficult, evaluations of the net contributions to future global warming requiring more time. If HCFCs are considered unacceptable, of the various options that might be used to replace CFCs in risk of ozone depletion is likely to increase due to prolonged each of the major applications areas. Oak Ridge National use of CFCs. Laboratory is conducting the portions of the study related to Capital investments will be required for facilities to pro- refrigeration/air conditioning/heat pump and insulation, and duce alternatives to CFCs and to make the consumer prod- Arthur D. Little (Cambridge, MA) is conducting the precision ucts using those alternatives. Those investments will be made cleaning evaluation. Scheduled for completion in 1991, the only if investors are reasonably confident of an adequate report should provide the basis for decisions leading to return. Although different for every segment of industry continuous improvement in reductions to contributions to involved in production and use of CFCs, the time required for future global warming. producers of HCFC and HFC alternatives to realize an adequate return is -15 years from the time plant construction Constraints is begun. Fig. 3 shows cash flow over time for a chemical product There are three constraints limiting the rates of improvement such as the HCFCs. Research and development work is in reducing safety health and environmental risk: the need for normally funded from earnings on existing products. Once Downloaded by guest on October 1, 2021 Colloquium Paper: McFarland Proc. Natl. Acad. Sci. USA 89 (1992) 811 ing, product reliability. The goal must be improvement in Risk methods of providing these products and services. Product investment , premium (ii) Work for steady improvement toward long-term goals. "Ideal" solutions are not currently available. Demanding an Low-risk investment ideal solution with respect to one aspect of the overall 0) (bonds, savings, etc.) problem can lead to unacceptable solutions with respect to c - other areas. Priorities should be set for areas where fastest cU improvement is required. The priority issue here is reversing m Investment recovered the trend of increasing atmospheric chlorine concentrations. 0nCD Construction (iii) Safety and health standards must not be compromised. W gz- / Hir Market fails to develop (iV) Keep the constraints in mind. Goals set by regulation must recognize the need for global compliance, the rate of Development Product sold development and implementation of new technology, and the \/=9 > | need to encourage investment in alternative technologies. (v) Cooperation is essential. The optimum solutions will be 5 10 15 205 achieved through cooperation of governments, environmen- Years groups, and industry. tal(vi) Gaseous emissions should be minimized. Current FIG. 3. Typical investment life cycle: Product investment vs. applications of CFCs ultimately result in emissions. Many of low-ris;k investment. Cash flow estimates over time for a chemical the currently available alternative technologies also lead to producA such as the HCFCs. Approximately 15 years is required for emissions of gases. If those gases have short atmospheric adequaate return on investment to justify a decision to build a lifetimes, they have the potential to contribute to local produc:tion facility. environmental concerns such as photochemical smog. If the lifetimes are long, they have the potential to contribute to constIruction begins, there is a negative cash flow of $100 global environmental concerns. The HCFCs and HFCs have millioin or more over 3-4 years to build a world-scale plant. intermediate lifetimes to minimize potential environmental effects. With the potential for increasing global demands for In order to justify the original investment, sale of the product using these compounds, emissions of these gases must Iprovideprovideearningseigexednthexceeding the return tacolproductsthat could have should be kept as low as possible. been aLchieved by investing in low-risk options such as bonds (vii) Continue research to learn about interaction of man or treEasury notes. Actually, a series of investment decisions and the environment. We are just beginning to learn of will be e required worldwide over the next decade in order to potential effects on the global environment. With growing provicle sufficient amounts of alternative products to allow population and improving standards of living, we must have the CIFC phaseout. Each decision will be based on an analysis the knowledge base to ensure sustainable development. of likely return on investment. If it appears that HCFCs would be regulated before the risk premium could be real- 1. Molina, M. J. & Rowland, F. S. (1974) Nature (London) 249, 810-812. ized, it is unlikely that the HCFCs would be produced and, 2. World Meteorological Organization (WMO) (1988) Report of again, use of CFCs could be prolonged. the International Ozone Trends Panel-1988 (WMO, Geneva), Rep. No. 18. Conclusions 3. Stolarski, R. S., Bloomfield, P., McPeters, R. D. & Herman, J. R. (1991) Geophys. Res. Lett. 18, 1015-1018. 4. U.S. Environmental Protection Agency, Office of Toxic Sub- The goal in phasing out CFCs should be continuous improve- stances (1990) Hydrofluorocarbons and Hydrochlorofluorocar- ment in reducing safety, health, and environmental risks bons Interim Report (U.S. Environ. Prot. Agency, Washing- while meeting societal needs and consumer demands. Seven ton). factors must be considered to ensure that this goal is fulfilled. 5. World Meteorological Organization (1989) Scientific Assess- (i) Focus on the products and services being provided. In ment of Stratospheric Ozone (WMO, Geneva), Rep. No. 20. 6. Watson, R., Prather, M. & Albritton, D. (1989) (United Nations refrigeration, the focus should be preservation of perishable Environ. Prog., Nairobi), UNEP/021.Pro.WG.II(1)/CRP.1. items; in air conditioning, increased worker productivity and 7. Prather, M. J. & Watson, R. T. (1990) Nature (London) 344, consumer comfort; in insulation, energy efficiency; in clean- 729-734. Downloaded by guest on October 1, 2021