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individual firm can exchange emission permits for its emission sources within the firm at the same location; this is a half-way step to a full marketable-permit system, which would allow firms to trade permits among different firms. Similarly, for motor vehicles, a fleet-averaging policy that would allow a manufacturer to satisfy emission standards if the sales-weighted average of its vehicles were at or below the standard, rather than every vehicle's being required to meet the standard, would allow the manufacturer to trade off low-cost ways (e.g., smaller vehicles) of meeting the standard against high-cost ways (e.g., larger vehicles) (White, Chapter 7~. Allowing vehicle manufacturers to trade (or even to "bank" for future use) any margin between allowed and actual emissions would convert a fleet-averaging scheme to a form of marketable-permit scheme. It should be noted, however, that fleet averaging, even with trading, is not identical with the standard marketable-perTnit scheme. The latter sets a limit on the overall amount of emissions, whereas the former sets a limit on the average per vehicle, but does not set a limit on the number of vehicles that can be sold. There are some circumstances in which a tightening of the standards in a fleet-avera~in~ scheme could lead, perversely, to an increase In total emission. ~ Overall, if regulatory schemes to control PAHs are put into effect, it appears desirable that the implementation tools chosen emphasize economic incentives and efficiency, regardless of the control levels that are selec ted as targets . OBTAINING A BENCHMARK A convenient way to start is to try to determine a soc fetal value to place on a reduction by 1 ton/yr in PAN emissions from at least one important category of sources. If this benchmark figure can be estab- lished, the assessment of the likely costs and benefits of controlling PAHs from other categories of sources will be easier. The data from the analyses of Chapters 1, 2, and 3 and Appendix C, plus the risk valuation discussed earlier in this appendix, provide the basis for such a benchmark calculation. Again, we use BaP as a representative of PAHs. Thus, although emissions and concentrations are expressed in terms of BaP, they really represent a far larger "soup" of PAHs for which BaP is, in essence, the "tracer," or surrogate. Differences in particle size or other factors that might affect respirability or bioavailability are largely ignored. Linearity is assumed in most models. The information in Chapter 1 shows that in 1979 the amount of BaP emitted into the atmosphere from urban road motor vehicles was suf f ic lent to cause an urban commuter to inhale a calculated dose of up to 20.1 ng of BaP in the course of 24 h. By the year 2000, it is estimated that the same commuter would inhale only 9.1 ng/d. These estimates are based on inhalation rates of 15 m /d. Thus, for 1979$ the average concentration of BaP from motor-vehicle emission in the air breathed by the "worst-case" person was 1.34 ng/m3--i.e., (20.1 ng/d)/~15 m3/d)--and for 2000 it D-11 . -

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would be 0.61 ng/m3. In the first year, 13.46 metric tons of BaP was estimated to be emitted by motor vehicles, and in 2000, 10.14 metric tons. If we adopt a rough linear model relating the gross BaP emissions per year to average concentration, we estimate that 1 ton = 0.1 ng/m3 for the first year and 1 ton = 0.06 ng/m for the second year. In later calculations, the first figure is used as a conservative estimate. Thus, it is assumed that a reduction of 1 ton of BaP emissions per year from motor vehicles is likely to reduce average urban BaP ambient concentra- tions by 0.1 ng/m3 for that same year. Next, this change in BaP concentration should be converted to an equivalent mortality risk. In Appendix C, it is estimated that exposure to BaP at an average of 1 ng/m3 for an entire lifetime leads to a cumulative excess risk of lung cancer by the age of 70 of 0.02-0.067. Again, the latter figure is used as a conservative estimate. Thus, if it is also assumed that a ton of BaP (representing a larger quantity of PAHs) from motor vehicles has the same health consequences as a ton of BaP (also representing a larger quantity of PAHs ) from another atmospheric source then breathing BaP from motor vehicles at an average Of 0.1 ng/m3 would have a cumulative excess risk of 0.006%, or 0.6 x 10 . This would be the same risk generated by 1 ton of BaP emission per year for 70 yr. But it is necessary to determine the risk generated by 1 ton of BaP in 1 yr. As an approximation, this extra risk can be "smeared" equally over all 70 yr. Thus, the extra risk of premature death per year is 0. 00009t, or a 0.9 x 10-6 probability of a premature death in each year. (Although the original 0.006% is a cumulative risk to age 70, with the risk of premature death in each year rising exponentially, the absolute numbers are small enough so that "smearing" equally makes little difference in the results.) Finally, a value can be put on this probability. The range of the annual value of avoiding a 0.001 annual probability of a premature death, reported above, was $170-1,000 (in 1978 dollars). To be conservative, the upper limit will be used and translated into a 1982 dollar figure of about $1,500 per 0.001 risk. This figure, then, indicates that the reduction in annual risk of 0.9 x 10 6 would be worth about $1.35/person.- It should be recalled that the atmospheric-concentration data apply to urban areas. Approximately 75% of the U.S. population of 225 million live in urban areas, or about 170 million. Accordingly, these calculations indicate that the reduction in BaP emissions by 1 ton in 1 yr which would lower urban ambient concentrations of BaP by about 0.1 ng/~3 and thus lower the annual risk of death per person exposed by 0.9 x 10 6 ~ would be worth about $225 million in the aggregate, or $225,000/kg, $225/g, or $0.22/mg of BaP e It should be noted again that BaP is being used here as a tracer to represent a larger collection of PAHs and that the $0.22/mg of BaP really represents the value of controlling this larger "soup" of PAHs that has a potency that can be measured and represented by 1 mg of BaP. Also, the risk valuation applies only to the lung-cancer consequences of exposure to PAHs; other possible mortality and morbidity consequences of exposure have been ignored. D-12

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Furthermore, it should be emphasized that each of the key components of the value estimate is an estimate that has a substantial range of uncertainty. The risk of death associated with breathing BaP at a given concentration has an uncertainty range of approximately a factor of 3; the societal value of avoiding a premature death has a range of approximately a factor of 6; and the likely atmospheric concentration from a ton of BaP has a range of 1. 5. Because these estimates are used multiplicatively, the overall range of uncertainty on the final value estimate is approximately a factor of 25. For the present analysis, in each case the most conservative estimate of each component--the figure that would indicate the greatest societal benefit from controlling PAHs--was used. Alternative methods would have been to use the most likely value for each component and to carry the range throughout. But information for choosing the most likely values is not available ; and, as noted , carrying the range throughout leads to an uncertainty range of a factor of 25 downward from the estimate of a - societal value of $225 million per ton of BaP removed. Thus, at the other end of the range, those who prefer to be less conservative could use a value as low as $9 million per ton of BaP removed. In matters of public decision-making concerning the societal value of actions that involve avoiding premature deaths--a highly controversial subject--a conservative approach seems warranted. Accordingly, the figure of $225 per ton is used for the remainder of this analysis. CONTROL OF PAH EMISSIONS FROM VARIOUS SOURCES . Although PAHs are the product of virtually every burning process, it makes sense to folds on the quantitatively important sources. Chapters 1-4 and other studies indicate that the following sources are important (not necessarily in order of quantitative importance): Road motor vehicles. Other mobile sources (e.g., trains, planes, and ships). Fireplaces. Wood-burning stoves. Residential coal-fired heating. Industrial coal-fired boilers. Coke produc t ion . Indus trial-commercial incinerators . Agricul tural open burning . Land-clearing waste burning. Prescribed burning of underbrush in forests. Forest and prairie fires. Structural fires. Coal-refuse f ires . Volcanoes . The control of PAH emissions from some of these sources can be ruled out, because they cannot be control led ~ such as volcanoes ~ . In principle, reductions in PAH emissions could probably be achieved by applying more D-13

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resources to controlling forest fires, structural fires, and coal-refuse fires (largely in abandoned coal mines). But the other societal costs from these sources probably bulk so large in comparison with their PAH-related costs that greatly increased efforts to combat these fires could not be justified solely on the basis of their PAH emissions. Other sources may offer some promise of worthwhile control. The discussion here begins with road motor vehicles, because the data on them are best, and then examines stationary sources. In each case, only the reductions in PAH emissions are valued and compared with the costs of the reductions. In many instances, the effort to reduce PAH emissions will reduce other harmful pollutants as well (e.g., particulates in general). The reductions in these other pollutants may have additional societal value; but that value is not calculated or considered here e Also, in some instances, efforts to reduce PAH emissions may increase the emissions of other pollutants. These additional effects are ignored. Thus, the discussion here focuses on whether reductions in PAH emissions, valued alone, justify (or come reasonably close to justifying) control efforts. ROAD MOTOR VEHICLE S As noted earlier, gasoline-powered vehicles without exhaust catalytic converters (i.e., all pre-1975 cars and light-duty trucks and all heavy-duty trucks and buses of any vintage) and diesel cars, trucks, and buses constitute the major sources of PAH emission from road motor vehicles. An additional category of "problem" vehicles would include cars and light-duty trucks of the 1975 and later model years that have emission control systems that are no longer functioning properly. The categories of gasoline and diesel vehicles are addressed separately. Unless otherwise indicated, urban-rural driving distinctions are ignored, and emission reductions in rural areas are valued at the same rate as urban reductions. Gasoline Vehicles . . _ At the beginning, it is useful to establish a relationship between total hydrocarbon (HC) emission per mile and BaP emissions per mile for gasoline-powered vehicles. The data in Chapters 1-3 and in Williams and Swarin45 indicate an approximate relationship--HC at 1 g/mi = BaP at 2 g/mi--that is used in the discussion that follows. Once motor vehicles are manufactured and on the road, there are three major ways to reduce emissions (including that of PAHs) from them: retrofitting them with further controls, inducing better maintenance and slower deterioration of their control systems, and inducing owners to junk them in favor of newer vehicles. Retrofitting does not seem to be a practical method; it would probably achieve only modest emission reductions, and it is quite unpopular. Only D-14

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one state (California) has a program for requiring retrofitting of older cars, and that program appl ies only when cars change owners. Gruenspechtl8 has analyzed the prospect of providing subsidies to owners of older cars to junk them in favor of newer ones and finds it a worthwhile strategy, compared with the costs of the tighter standards imposed for the 1981 and later model cars. The societal benefits from PAR reductions, not included by Gruenspecht, would add to his results. An older car that emitted HC at 4 g/mi (and hence BaP at 8 ~g/mi) more than a new car and that was expected to las t for another 40,000 mi of operas ion would emit: 320 mg of "extra" BaP during this period. The risk-valuation calculations of this chapter have shown that a reduction of this amount of BaP would be worth $70 to society. Thus, the bonus or subsidy paid to owners of old cars to induce them to junk the vehicles could be increased by this amount, to induce yet more turnover of the f feet . Better maintenance of emission control systems can be induced by inspection and maintenance (I&M) programs by states and locales. White44 examined these programs and concluded that they could be worthwhile under some circumstances, especially if linked to safety-inspection programs. The societal value of the reduction in emissions of all pollutants achieved by such programs was estimated to be $23/vehicle, with $5 of this coming from the 5 kg of HC reduction per year per vehicle that would be achieved. The values were based on the comparative costs of achieving the equivalent reductions in emissions from other sources. To the extent that vehicle HC emissions contained appreciably more BaP than the HC emissions from other sources, this might raise the societal value of the reduction. The limit of this increase would be $2/vehicle [~10 mg)~$0.22) ~ $2~. This figure is well within the margin of error of the original calculations and hence does not appear to make I&M programs appreciably more attractive than they otherwise would be. One other source of improved maintenance can be examined. The U.S. Environmental Protection Agency (EPA) reported that 5-107 of 1975 and later cars have used leaded fuel, which, after five or six tankfuls, permanently poisons and renders useless the catalytic converters on these cars. If only unleaded gasoline were sold, this poisoning would not occur. The societal value, from the perspective of PAR emissions, of this change to the production and sale of only unleaded gasoline can be calculated. The effect on HC (and hence PAH) emissions of the loss of effectiveness of the converter depends on the way the manufacturer has tuned the remainder of the control system. If we use a change in HC of 2 g/mi as a likely estimate, this implies additional emissions of BaP at 4 ~g/mi. Suppose that 10t of the catalytic-converter fleet (cars and light-duty trucks) has poisoned catalysts and that this fleet accounts for 70% of the 140 x 101 mi driven annually by gasoline vehicles. Then the extra BaP emissions from the poisoned-catalyst Vehicles come to 392 kg of BaP per year (4 ,u g/mi x 0.1 x 0.7 x 140 x 101 mi/yr) . The risk-valuation procedure indicates that the elimination of these emissions would be worth D-15

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about $86 million. (This counts reductions in both urban and rural BaP emissions as worth $0.22/mg; if only urban-emission reductions are considered valuable, because rural emissions are more dispersed and are relatively less harmful, the value would be only 60% as great, or $52 million.) To achieve this gain, the 40 x 109 gal of leaded gasoline would have to be replaced by unleaded. A conservative estimate of the cost of this conversion would be $0.05/gal--a low estimate of the difference in retail price between leaded and unleaded gasoline. (There appear to be no good reasons why the difference in retail price should not fully reflect the. difference in the complete cost of production, distribution, and sale of the two types of gasoline.) Thus, conservatively, the conversion would cost at least $2 billion/yr. Because unleaded gasoline tends to have a higher aromatic-compound content than leaded and a higher aromatic- compound content tends to yield greater PAH emissions, the conversion would tend to- yield greater PAH emissions from older vehicles and from all heavy-duty trucks--but lead emissions would decrease. In sum, the benefits from PAH reductions alone appear to be far smaller than the costs of converting the U.S. gasoline supply entirely to unleaded. The HC emission standards for heavy-duty gasoline trucks currently limit HC emissions to the equivalent of about 5 g/mi, or about 0.5 ton over the life of a truck. The heavy-duty truck regulations likely to be promulgated for 1984 and after will decrease this to about 0.23 ton of HC over the life of the vehicle. 2 Further tightening of standards (as originally promulgated for 1984) could decrease lifetime HC emissions by an additional 0.08 ton; this would yield a decrease of roughly 0.16 g of BaP. The risk-valuation method indicates that this decrease would be worth $35. EPA has estimated that the hardware (largely, a catalytic converter) for this further tightening of a standard would cost about $300; some manufacturers have indicated higher values. In any event, the value of the reduction in the amount of BaP is unlikely to make an appreciable difference in assessing the value of the change in HC over the life of the vehicle. In sum, for gasoline vehicles, the likely benefits from reductions in PAH emissions appear to fall far short of the costs of the measures that would be necessary to achieve them. Diesel Vehicles As noted in Chapter 1, diesel vehicles are important sources of PAHs' with most of these compounds adsorbed on the surface of carbon particles. Also given in Chapter 1 are estimates of BaP emissions of 13 Mimi and 54 ~ g/mi for light-duty and heavy-duty diesel vehicles, respectively, and they are used initially here. D-16

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Reductions in particulate emissions from light-duty diesels have thus far been achieved through engine modif ications; because no regulations have been promulgated for particulate emissions from heavy-duty diesels, it is unlikely that any reductions in emissions from these vehicles have occurred. Further reductions in emissions from light-duty diesels appear to be possible from two sources: trap-oxidizers in the exhaust and fuel modifications. Assume that a trap-oxidizer, in reducing Articulates, reduces PAH emissions by a comparable percentage. EPA regulations currently mandate a standard of a particulate maximum of 0.6 g/mi for 1982-1984 light-duty diesels. For 1985 and after, current EPA regulations require standards of 0.2 g/mi for diesel cars and 0.26 g/mi for diesel light-duty trucks. It appears unlikely that the required trap-oxidizer technology will be available, and these regulations are likely to be modified. Nevertheless, because the trap-oxidizer technology has been pursued in the context of the 0.2-g/mi standard, it is useful to analyze emissions in the same context. The 0.2-g/mi standard would imply a roughly two-thirds reduction in particulate emissions. If BaP emissions fall by the same proportional amount, this implies a reduction of 8 ~g/mi. Over the typical life of the vehicle (100,000 ml), there would be 0.8 g less BaP emitted from the vehicle. The risk-valuation procedures indicate that this reduction would be worth $176. (In principle, a discount rate should be used for benefits after the first year. Because of the pattern of use of these vehicles, a real discount rate of 3Z would reduce the net present value of the benefits by only 10~.) General Motors currently estimates that a trap-oxidizer, if it is made practicable, will cost around $500;1 EPA has estimated the cost as appreciably lower. There may also be fuel-economy penalties and driver-satisfaction costs. The societal value of the reduction in PAH emission alone would offset only a modest fraction of the cost of control. As to heavy-duty diesel trucks, in late 1980 EPA proposed a set of regulations that would have reduced particulate emissions from heavy-duty diesels built in 1986 and later to one-third the emissions from unregulated vehicles.39 EPA has taken no further action to make these rules final, and, because they too required trap-oxidizers, it appears likely that they will be modified. But they are useful as a benchmark.- A two-thirds reduction in Hap emissions would mean a reduction of 36 ~g/mi. Over the typical life of a heavy-duty diesel vehicle (475,000 ml), this implies a reduction in BaP emissions of 17.1 g. The valuation method indicates that this reduction, if it all occurred in urban areas, would be worth $3,760. (These estimates do not incorporate a discount rate.) Here, however, the rural-urban distinction cannot be ignored. The data in Chapter 1 indicate that only 20Z of heavy-duty diesel mileage is likely to occur in urban areas. Thus, these estimates are upper limits of their likely societal value. If BaP emissions in rural areas were assumed to have little or no serious human-health consequence (i.e., it is transformed or otherwise removed in an ultimately harmless fashion before an appreciable number of D-17

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people are exposed), then the societal value (based only on urban exposure) would be only $752. This last value is still relatively large. The reduction in PAH emissions from heavy-duty vehicles seems to be societally important (in essence, because of the relatively heavy emissions from and the high mileage accumulated by these vehicles). Even if the large reductions attempted by the regulations proposed in late 1980 cannot be achieved, it appears that smaller reductions (which might be achieved through relatively low-cost engine modifications, analogous to those already achieved in light-duty diesels), although also promising smaller benefits, would be societally worthwhile on the basis of PAH emissions alone. In this respect, this appendix can echo the recommendation of the recent NRC study of light-duty diesels: "Regulate particulate exhaust from such large sources of emissions in road transport as heavy diesel trucks and buses ; this may be more cost-effective than tightening the emission levels of diesel cars and light trucks."29 The substitution of No. 1 diesel fuel for the currently used No. 2 diesel fuel can reduce particulate emissions and PAH emissions . 5, 6, 20 The results of Hare and Baines20 indicate that BaP emissions from light-duty vehicles may be reduced by about 25%. An experiment on Washington, D.C., buses suggests that the reduction might be even greater for heavy-duty vehicles.24 The estimate of 25% is used here. The BaP emissions from both light- and heavy-duty diesels is 320 g/gal. A 25% reduction would mean a reduction of 80 ~g/gal. The risk- valuation procedures place a value of $0.018 on this reduction. The current retail-price difference between the two fuels is around $0.08 per gallon. It does not appear that the benefit from the PAH reduction alone would exceed the costs of the substitution of No. 1 for No. 2 diesel fuel. In sum, efforts to achieve engine modifications in heavy-duty vehicles appear to be the most cost-effective way to achieve net societal gains. A few caveats should be mentioned with respect to the discussion of diesel vehicles. First, the diesel analyses assume that the PAH emissions from diesel vehicles, as represented by BaP, have the same health consequences per ton as the PAH emissions from other sources. But a recent NRC study failed to find any definite association between diesel- exhaust emissions and carcinogenesis in humans, despite the presence in the exhaust of PAHs that are known to be carcinogenic in other animals. The study's authors suggested that there may be something special about the bioavailability of these compounds to humans when they are present in diesel exhaust. At the other extreme , however, the data in Appendix ~ indicate that the extrac ts from some diesel exhaus t may be as much as 89 times more potent mutagenically when measured on a BaP-equivalent basis. The discussion in this section steers a middle course and assumes that BaP in vehicle exhaust represents the same carcinogenic potential for humans as does the BaP from the sources covered in the review of epidemiologic studies in Appendix C. D-18

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Second4 the results of Springer,33 Hare and Baines,20 and Williams and Swarin 5 provide estimates for light-duty diesel BaP emissions of around 3 ~g/mi, with some vehicles achieving emissions below 1 ~g/mi; these estimates should be compared with the figure of 13 Mimi used in Chapter 1 and in this chapter. Thus, BaP emissions from light-duty diesel vehicles may be an order of magnitude lower than the figure used here, and the same qualification may apply to heavy-duty diesels. OTHER TRANSPORTATION VEHICLES Chapter 1 indicated that airplanes and ships are the major sources of BaP emissions in this category. Little other information appears to be available on emissions or possible avenues of control. Because most of these emiss ions occur outs ide urban areas, it is probably safe to neglect them in th i s ana lys i s . WOOD-BURNING STOVE S As the prices of other fuels have risen, burning wood for res idential heating has become more popular. Wood stoves have 2 or 3 times the thermal efficiency of fireplaces and have become increasingly popular. It is estimated that a million wood-burning stoves were sold in 1979, 9 and sales have been increas ing. Much of this wood-burning occurs in rural areas, but a substantives amount occurs in or affects urban areas. For example, Cooper et al . found that approximately 50t of the res pirable particles in the ambient air of Portland, Oregon, in January 1978 came from residential wood combustion. Cooper also estimated that residential woody combustion emitted 1.4 tons of BaP in Portland's ambient air during 1978. It appears that wood-burning stoves emit BaP at about 2.5 mg/kg of wood burned.9 Chapter 2 cited data that indicate that households burning wood as the primary source of heat each used an average of 5.6 metric tons of wood. It is likely that such a household used a wood stove. Thus, it would emit 14 g of BaP per year. (Thus, in teaks of BaP emissions, one wood stove is the equivalent of over 100 diesel cars each emitting 13 ~g/mi. ~ If we assume that emissions from a wood stove in an urban area have about the same effects on ambient BaP concentration as do vehicle emi ssions, -we can use the valuation method to indicate that the complete elimination of these emissions would have a societal value of $3 ,080 per year . Thus, it appears that the benefits from the control of PAR emissions from wood-burning stoves, especially in urban areas, are quite large. Unfortunately, research on emissions from wood-burning stoves is still at a relatively early stage. It appears that thy design and structure of stoves can make some difference in PAR emissions. 1 Even more importantly, :acalyclc comDuscors Mar to the catalytic converters on cars) in- stalled in the chimneys of wood Cloves may be capable of reducing organic~ compound emissions by up to 95%. These control devices, if they become D-19

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practicable, are expected to cost, installed in a new stove, around $125-150. It is unclear how durable they are, but even if they lasted only a year, it appears that their likely benefits greatly outweigh their likely costs . It appears unrealistic to expect any feasible program for requiring retrofitting of existing wood stoves in residential use. But many current owners of wood stoves may be "environment-conscious" and might be prepared to retrofit their wood stoves voluntarily if retrofit devices were available and there were sufficient publicity. And a program to require (or induce) manufacturers of new wood stoves to incorporate changes in design or technology that would reduce PAR emissions appears to have great societal benefits and relatively small societal costs. RE S IDENTIAL FIREPLACE S - Residential fireplaces are a large source of PAHs; they emit about one-third as much BaP as wood-burning stoves per kilogram of wood.9 It is unlikely that any emission-control program aimed at fireplaces would be feasible. It is unclear whether any technology is currently available for controlling emissions from fireplaces; even the catalytic combustors, which appear promising for wood stoves, are unlikely to be practicable for fireplaces, because the combustors require a higher temperature than most fireplace chimneys are likely to provide. Further- more, any retrofitting program would be highly unlikely to be put into effect, and installation of any technologic device in new residences would deal with only a tiny fraction of the problem. Nevertheless, because the aggregate amount of PAR emissions from fireplaces is large, and likely to grow, this appears to be a fruitful direction for research. RESIDENTIAL COAL-FIRED HEATING . There appears to be little available information on this subject. Some residential heating units are capable of burning both wood and coal. Because the emissions from these units are potentially large, more information should he collected and research encouraged. INDUSTRIAL COAL-FIRED BOILERS ~ _ Comparatively little appears to be known about the properties of these boilers. EPA still appears to be in the data-collecting stage with respect to these devices.l,7 Because these boilers are still being manufactured and are in the hands of relatively larger and more sophisticated users (compared with households), control efforts would probably be feasible if D-20

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the cost-benefit ratios were favorable. Retrofitting, inducement to use gas and oil, and improved design and technology (e.g., possibly catalytic combustors or precipitators) appear to be possible. Clearly, more research LS necessary. INDUSTRIAL-COMMERCIAL INCINERATORS Municipal incinerators do not appear to be a serious source of PAR emission, but industrial-commercial incinerators are.15 One possible reason is that municipal incinerators operate at higher, more efficient tempera ture s . Unfortunately, little other information is available about these sources. Two control strategies seem to be possible. One would be to focus on the technology of industrial incineration itself--i.e., focus on retrofitting, improving the design of new devices, exploring the possibility of combustors or precipitators, etc. Again, one would want to make sure that the cost-benefit ratios were favorable before embarking on such an e f fort . A second control strategy would be to require that industrial- commercial trash be hauled to municipal incinerators for burning. A rough estimate of the costs and benefits of such a strategy can be provided. If industrial-commercial incinerators have BaP emission rates of 120-570 g/kg of refuse burned, burning a ton of refuse would yield 120-570 mg of BaP. If this occurred in urban areas and the emissions had a dispersion pattern similar to that of motor-vehicle emissions, the risk-valuation method would indicate that the complete el imination of these emissions would be worth $26-125. It appears that municipal incinerators have BaP emissions rates 2-3 orders of magnitude lower than industrial-commercial incineration rates.l5 Thus, the use of municipal incineration would mean the virtual elimination of the BaP emission. In 1975, the cost of refuse collection was about $25/ton.34 This figure should probably be doubled to bring it to 1982 dollars, for an estimate of $50/ton. This cost estimate is within the range of the likely benefits from the reduction in industrial-coT~rrr~ercial incineration. Accordingly, efforts to reduce industrial-commercial incineration or the emissions from industrial-commercial incineration may be worthwhile and bear further investigation. COKE-OVEN EMISSIONS Coke ovens are well-known sources of PAR and BaP. Coke manufacturers are currently in the process of implementing emission reductions under EPA- supervised state implementation plans, consent decrees, and Occupational Safety and Health Administration plans. EPA has recently proposed further standards that would control emissions to a greater degree. 7 EPA D-21

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44. White, L. J. The Regulation of Air Pollutant Emissions from Motor Vehicles. Washington, D.C.: American Enterprise Institute for Public Policy Research, 1982. 110 pp. 45. Williams, R. L., and S. J. Swarin. Benzo~a~pyrene Emissions from Gasoline and Diesel Automobiles. SAE Technical Paper 790419. Warrendale, Pa.: Society of Automotive Engineers, Inc., 1979. 8 pp .' D-26

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15. Energy and Environmental Analysis, Inc. Preliminary Assessment of the Sources, Control and Population Exposure to Airborne Polycyclic Organic Matter (POM) as Indicated by Benzo(a)pyrene (BaP). Final Report. Arlington, Va.: Energy and Environmental Analysis, Inc., 1978. 16. Freeman, A. M., III. The Benefits of Air and Water Pollution Control. New York: John Wiley & Sons, 1982. 17. General Motors Corporation. Statement of General Motors Corporation to the Subcommittee on Investigations and Oversight of the Committee on Science and Technology, U.S. House of Representatives on Diesel Engine Technology. Washington, D.C.: General Motors Corporation, 1982. 19 pp. 18. Gruenspecht, H. K. Differentiated regulation: The case of auto emissions standards. Am. Econ. Rev. 72(2):328-331, 1982. l9. Harberger, A. C. Three basic postulates for applied welfare economics: An interpretive essay. J. Econ. Lit. 9:785-797, 1971. 20. Hare, C. T., and T. M. Baines. Characterization of Particulate and Gaseous Emiss ions from Two Diesel Automobiles as Functions of Fuel and Driving Cycle. SAE Technical Paper 790424. Warrendale, Pa.: Society of Automotive Engineers, Inc., 1979. 44 pp. 21. Krier, J. E., and E. Ursin. Pollution and Policy: A Case Essay on California and Federal Experience with Motor Vehicle Air Pollution 1940-1975. Berkeley: University of California Press, 1977. 401 pp . 22. Kwoka, J. E. The Behavior of Auto Firms under the Fuel Economy Constraint. Washington, D.C.: George Washington University, 1981. 25 pp. (mimeo) Levin, M. H. Getting there: Implementing the bubble policy, pp. 59-92. In E. Bardeck and R. A. Kagan, Eds. Social Regulation: Strategies for Reform. San Francisco: Institute for Contemporary Studies, 1982. 24. Little, Arthur D., Inc. Incremental Impact of a Fleetwide Fuel Change on Air Quality and Maintenance Costs. Final Report. Prepared for Washington Metropolitan Area Transit Authority, Washington, D.C., 1980. 136 pp . 25. Maloney, M. T., and B. Yandle. Bubbles and efficiency: Clean air at lower cost. Regulation 4:49-52, 1980. 26. Mikesell, R. F. The Rate of Discount for Evaluating Public Projects. Washington, D.C.: American Enterprise Institute for Public Policy Research, 1977. 64 pp. 27. Mills, E. S., and L. J. White. Government policies toward automotive emissions control, pp. 348-409. In A. F. Friedlaender, Ed. Approaches to Controlling Air Pollution. Cambridge, Mass.: Press, 1978. 28. National Research Council, Commission on Natural Resources. Chloroform, Carbon Tetrachloride and Other Halomethanes: An Environ- mental Assessment. Washington, D.C.: National Academy of Sciences, 1978. 29. National Research Council, Diesel Impacts Study Committee. Diesel Cars: Benefits, Risks, and Public Policy. Washington, D.C.: National Academy Press, 1982. 142 pp. MIT D-24

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