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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
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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.
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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
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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
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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
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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.
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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
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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.
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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
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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
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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
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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
.'
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Representative terms from entire chapter:
bap emissions
