Diesel Particulate Study
October 1983
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Sources
Office of Air and Radiation
U.S. Environmental Protection Agency
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Diesel Particulate Study
October 1983
Standards Development and Support Branch
Emission Control Technoloov Division
Office of Mobile Sources
Office of Air and Radiation
U.S. Environmental Protection Agency
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TABLE OF CONTENTS
Paae
PART I
INTRODUCTION 1
EVALUATION OF CONTROL OPTIONS 6
PART II -SUPPORTING TECHNICAL ANALYSES:
Chapter
1. Technology i-i
2. Emissions Impacts 2-1
3. Air Quality Impact and Population Exposure 3-1
4. Visibility Assessment 4_1
5. Cancer Risk Assessment 5-1
6. Non-Cancer Health Effects 6-1
7. Soilina Effects 7-1
8. Economic Impact 9-1
9. Cost Effectiveness 9-1
10. Sensitivity 10-1
Appendix A A-l
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Part I
INTRODUCTION
I. Purpose of the Study
EPA's study of the costs and environmental effects of the
control of diesel particulate emissions and their regulation
has been underway for some time. Emission standards for 1982
and later diesel-powered light-duty vehicles and light-duty
trucks (light-duty diesels) were promulgated in 1980. Similar
standards for diesel-powered heavy-duty diesels were proposed
in 1981.
The pertinent data on both the costs and benefits of
diesel particulate control have been constantly changing over
time. This is particularly true of the last two to three years
since the time of the rulemakings mentioned above. Emission
control technology has been constantly evolving, changing both
baseline emission rates and the ability and costs of further
control. In addition, a number of cancer-related health
studies on diesel particulate have been completed in the last
two years, allowing an assessment of benefits in this area
which was not previously possible. Data and projections in
other key areas have also been changing, resulting in a need
for EPA to reexamine its regulatory position.
Recent regulatory activity by EPA has reflected these
changing circumstances. In the light-duty area, EPA has
promulgated a delay of the more stringent, 1985 standards until
1987, leaving in place the current 1982 .standards through
1986. This action is based on the fact that a new control
technology could not be applied fleet-wide for the 1985 model
year, but will require two additional years of effort. This
new technology is referred to as a trap-oxidizer and produces
substantial reductions (i.e., greater than 50 percent) in
diesel particulate emissions. In the heavy-duty area, EPA has
announced its intention to repropose its particulate standard
along with the NOx standard proposal, because of the
interelationship between NOx and particulate control. This
combined proposal should enable this interaction between the
two pollutants to be better assessed and facilitate a more
orderly standard setting process.
The purpose of this study is to provide a comprehensive
assessment of the costs and environmental effects of the
control of diesel particulate emissions and to recommend a
regulatory strategy for their control. As such, this study
expands, updates and combines the Regulatory Analyses
supporting the light-duty diesel (LDD) particulate final rule
and the heavy-duty diesel (HDD) particulate proposed
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2
rule.[1,2] The study will identify current and future diesel
particulate emissions and exposure levels, assess the health
and welfare impact of diesel particulate, and estimate the
costs of controlling diesel particulate emissions to various
levels. The study will then integrate these aspects of diesel
particulate control and develop, evaluate, and recommend a
regulatory control strategy.
This study does not attempt to economically quantify the
changes in health or welfare that are associated with various
diesel particulate control strategies. Such an economic
quantification of benefits is beyond the scope of this report,
but has been performed for various diesel particulate control
strategies under contract to EPA.[3] The reader should consult
this document and others in the literature for information on
the economic benefits o-f controlling diesel particulate.
Four regulatory scenarios are examined in this report
which cover a wide range of technological stringency. The
least stringent control scenario (the relaxed scenario) would
require no further control from LDDs and only very modest
reductions from HDDs, representing the least stringent degree
of control conceivable. The next most stringent scenario (the
intermediate scenario) would reauire the aoplication of
advanced non-trap technology. By their nature, these
techniques are quite cost effective and this scenario
represents a modest degree of control that should be available
at low cost. The third scenario (the base scenario) consists
of the current trap-based standards (i.e., the 1985 LDD
particulate standards and that proposed for 1986 HDDs). This
scenario provides more control than that achievable through
non-trap technoloav, but will be more costly and less cost
effective than the second scenario due to the use of trap
technoloav. The fourth scenario (the strinaent scenario)
represents the greatest degree of control presently
conceivable. Nearly all vehicles would be equipped with traps
under this scenario. These scenarios are summarized in Table 1.
As an averaging concept has already been promulgated for
compliance with the 1987 LDDV and LDDT trap-based particulate
standards, the flexibility it provides will be presumed here
for the base, intermediate, and stringent scenarios. As it is
likely, but not certain, that a similar program will be
proposed for HDDs, both averaging and non-averaging situations
will be examined for the base scenario. Only averaging
situations will be considered for the HDD intermediate and
stringent scenarios. However, under the HDD stringent
scenario, all vehicles are likely to require traps, so
averaging does not add much flexibility.
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3
Table 1
Emission Control Scenarios*
Particulate Standards
Level*
Implementation
Date**
Relaxed Scenario:
LDDV (a/mi)
LDDT (g/mi)
. HDDV (g/BHP-hr)
Intermediate Scenario:
LDDV (g/mi)
LDDT (g/mi)
'HDDV (g/BHP-hr)
Base Scenario:
LDDV (g/mi)
LDDT (g/mi)
HDDV (g/BHP-hr)
Stringent Scenario:
LDDV (a/mi)
LDDT (a/mi)
HDDV (a/BHP-hr)
Current Levels(NA)
Current Levels(NA)
0.6(NA)
0.30(A)
0.35(A)
0.40(A)
0.20(A)
0.26(A)
0.25(NA & A)
0.08(A)
0.105(A)
0.10(N/A)
1988
1987
1987
1988
1987
1987
1988
1987
1987
1988
Range of
NOx Standards
1.0, 1.5, 2.0
1.2, 1.7, 2.3
1.0, 1.5, 2.0
1.2, I.", 2.3
1.0, 1.5, 2.0
1.2, 1.7, 2.3
1.0, 1.5, 2,0
1.2, 1.7, 2.3
(A) means averaging program available, (NA) means no
averaging Drogram available. Also, all control scenarios
were evaluated for their incremental effects beyond
continuing the relaxed scenario.
The implementation dates for the various HDD standards
analyzed in Part II were arbitrarily chosen at 1988 for
simplicity. In reality, as discussed in Part I most of
these standards would likely be implemented about 1990,
except for the 0.6 g/BHP-hr standard which appears
feasible by 1987.
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4
A factor that must be considered when assessing the
ability to control diesel particulate is the level of the
applicable NOx standard. In general, as NOx emissions are
reduced, engine-out levels of particulate increase. Thus,
under a stringent NOx standard the technically feasible level
of particulate control (without the use of aftertreatment
devices) will be higher than under a lenient NOx standard.
Because there is currently some doubt as to what the NOx
standards will be in the years covered by this study, three
different LDDV standards were evaluated: 1) 1.0, 2) 1.5, and
3) 2.0 g/mi. As the NOx standard for LDDTs is directly
influenced by that for LDDVs, this study will also evaluate the
effect of the three LDDT NOx standards equivalent to those for
LDDVs: 1.2, 1.7, and 2.3 g/mi.
The question of the appropriate NOx standard for HDDs is
dealt with in a more straightforward fashion than LDDs, since
the level of the standard will be set by EPA. While Section
202 (a) (3) (A) (ii) of the CAA requires a NOx standard of 1.7
g/BHP-hr, this level is not feasible for HDDs. Thus, EPA must
set a revised NOx standard under the requirements of Section
202(a)(3)(B), which are very similar to the requirements
specified for the HDD particulate standard in Section
20 2 (a) (3) (A) (i i i) . Thus, under all scenarios, the HDDV NOx
standard is treated as a variable and identified in much the
same way as the particulate standard.
II. Organization of the Study
The study has been segregated into two parts. Part I of
the study contains this introduction and an overall evaluation
of control.options. Part II contains the supporting technical
analyses.
In addition to describing the context, purpose and
organization of the study, this introduction describes the
control scenarios evaluated and the diesel sales projections
used throughout the analysis. The following "Evaluation of
Control Options" summarizes the costs and environmental
benefits of the various diesel particulate control scenarios
and then goes on to compare and evaluate their relative
strengths and weaknesses.
The supporting technical analysis is contained in ten
chapters. The first seven chapters address the benefits of
control, including vehicular emissions (Chapter 1) , nationwide
and urban emissions (Chapter 2), air quality and exposure
(Chapter 3), visibility (Chapter 4), carcinogenic risk. (Chapter
5), non-carcinogenic health risk (Chapter 6) and soiling
(Chapter 7) . Two chapters address the cost (Chapter 8) and
CO S t" c * PC f" * U i» * i» c c f C » n a "» C * * & ~ « * "¦ - - '«¦«<•» «' r^r
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5
last chapter (Chapter 10) addresses the sensitivity of the
technical results to key assumptions made throughout the study
and includes other, more secondary tvpes of analyses.
The primary technical analyses (i.e., those contained in
Chapters 1 throuah 9) will evaluate only the relaxed and base
control scenarios because these two scenarios are considered
the most likely to occur and all technical concepts associated
with the stringent scenario, such as control technology, are
also contained in the base scenario. The NOx standards of the
main analysis will be 1.5 and 2.3 g/mi for LDDVs and LDDTs,
respeqtively, because they are the current standards and
certification test data is available under these levels. As
the methodoloqy used in Chapter 1 to adjust particulate
emissions for different NOx emissions standards is subject to
some error, this will minimize the use of such adjustments in
the main analysis. The primary technical analyses (i.e.,
Chapters 2 throuah 10) also evaluate two diesel sales
projections: the best and worst estimates. The impact of: 1)
other LDDV and LDDT NOx standards on the relaxed and base
particulate control scenarios, 2) the stringent control
scenario under all NOx standards, and 3) the effect of a. no
growth diesel sales projection will be evaluated in Chapter 10,
Sensitivity. As little firm data is available concerning the
technology associated with the intermediate sceanario, it will
also be addressed in ChaDter 10.
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6
EVALUATION OF CONTROL OPTIONS.
I. Introduction
The purpose of this evaluation is to first combine the
results of supporting technical analyses, which addressed in
detail the costs and environmental effects of controlling
diesel particulate emissions, and then conduct a comprehensive
comDarison of the feasible control scenarios in liaht of their
effect. Three stages are necessary to do this.
First, the health and welfare effects of the various
particulate control scenarios will be assessed to identify the
most siqnificant impacts and to determine the need for
control. In addition, this first step will also identify the
kev aspects of the cost and cost effectiveness of diesel
particulate control to form a basis for assessing the dearee of
control which is reasonable. This first step of the analysis
will focus on the most likely set of external factors for
liaht-dutv diesels (LDDs), such as the best estimate diesel
sales projections and the oxides of nitrogen (NOx) standards
currently mandated bv the Clean Air Act (CAA) (1.0 qram per
mile (g/mi) for light-duty diesel vehicles (LDDVs) and an
equivalent standard (1.2 a/mi) for liaht-duty diesel trucks
(LDDTs)). The impact of various conceivable sales projections
for heavv-dutv diesels ("DDs) is not sianificant and will not
be considered in this chapter.
Second, viable strateaies for controllina diesel
Darticulate emissions will be identified. while the base,
relaxed, and strinqent control scenarios are addressed
throughout the supportinq technical analyses as likely control
scenarios (see Table 1 for a description of these scenarios),
the number of such scenarios was kept to a minimum to retain
some measure of control over the scoDe of the technical
analysis. were, the levels of control contained in the three
orimarv scenarios for the various vehicle groups will be
combined in various ways and viable intermediate levels of
control identified. The relative feasibility of these
alternative control strateqies along with their costs, if not'
already addressed in the suDOortinq technical analvses, will
then be discussed.
Third, the siqnificant features of the various control
strateqies identified in the second staqe will be compared and
evaluated. Those strateaies whose disadvantaqes far outweiah
their advantages will be discarded, leavinq only the most
viahle strateaies for final consideration. The effect of the
various external factors on LDD control will also be evaluated
at this staqe.
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Table 1
Description of Control Scenarios
Analyzed in the Supporting Technical Analyses[11
LDDV[2]
LDDT[31
HDDV
Relaxed
Scenar io
Current
Technology
Current
Technology
0.6 g/BHP-hr
Base
Scenar io
0.2 g/mi
0.26 a/mi
0.25 g/BHP-hr
Stringent
Scenar io
0.08 g/mi
0.105 g/mi
0.1 q/BHP-hr
TIT
[2]
[3]
The availability of emissions averaainq
throughout for LDDVs and LDDTs, while both
non-averaqing situations were examined for
supporting technical analyses.
was assumed
averaging and
HDDVs in the
The three control
under three NOx
technical analyses:
The three control
under three NOx
technical analyses:
scenarios for LDDVs are each
control scenarios in the
1.0 g/mi, 1.5 g/mi, and 2.0
scenarios for LDDTs are each
control scenarios in the
1.2 g/mi, 1.7 g/mi, and 2.3
evaluated
supporting
g/mi.
evaluated
supporting
g/mi.
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3
II. Kev Costs and Environmental Effects of Controlling Diesel
Particulate
A. Benefits
Chapters 2 through 7 and 10 of the suDportirig technical
analyses address the environmental impacts associated with
diesel Darticulate emissions. Eour distinct health or welfare
effects were addressed: 1) non-cancer health effects, 2)
carcinoaenic health effects, 3) visibility, and 4) soilina.
These four effects are addressed below.
'1. Mon-Cancer wealth Effects
The assessment in Chapter fi was not able to make a firm
finding with respect to the non-cancer health effects of human
exDosure to susDended diesel particulate. Nevertheless, two
aeneral conclusions were made. First, it is possible that the
oraanic compounds adsorbed onto diesel particulate may be more
hazaradous than general suspended particulate matter less than
10 micrometers in diameter (PMiq), but the available
scientific evidence was inconclusive on this issue. Second,
there was some very limited information suagestinq that diesel
particulate may be less hazardous under certain conditions
(i.e., month breathina) than certain subfractions of PM]_o«
Here again, however, no conclusive judgment could be made on
this point. The overall decision was to treat diesel
particulate like any other type of particulate less than 10
micrometers in diameter with respect to non-cancer health
effects. This decision leads to an ability to use the air
aualitv and exposure estimates in conjunction with Drojected
compliance with the National Ambient Air Duality Standards
(MA AOS) for P^io as an indicator of the impact of diesel
particulate emissions on non-cancer public health.
Table 2 contains the air aualitv and exposure estimates
for the various diesel control scenarios under best estimate
sales (and the 1.0/1.2 g/mi NOx standards for LDDVs and
LDDTs). The estimates for these scenarios were developed bv
applying the ratio of the urban emission estimates of Chapters
2 and 10 to the air aualitv and exposure estimates of Chapter
3. Three indicators of impact are shown: 1) ambient urban
concentrations, 2) microscale concentrations, and 3) annual
averaqe urban exposures. It can reasonably be argued that the
microscale imDacts are the least critical. Thev represent very
short-term exposures (a few minutes to one hour) and exposures
of this lenath and at these levels would not be expected to
cause acute health effects. The remaining two indicators both
have relative advantaaes and disadvantages. The ambient urban
concentrations include a wide range of city sizes and
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9
Table 2
Indicators of Non-Cancer Health Effect Impacts
1995 '
1980 Relaxed Base Strinqent
Lead-Rased Ambient Diesel Particulate Concentrations (ua/m^)*
City Population
Greater than 1,000,000 1.2-2.7 3.1-7.4 1.6-3.9 0.9-2.3
500,000-1,000,000 0.8-1.8 2.2-4.9 1.2-2.5 0.7-1.5
250 ,000-500 ,000 0 . 9-1 . 5 2 .4-4 .1 1. 3-2 . 1 0 . 8-1.2
100,000-250,000 0.6-1.6 1.6-4.3 0.7-2.2 0.4-1.3
Microscale Diesel Particulate Concentrations (uq/m3)
Roadway Tunnel
Tvpical 57 122 63 36
Severe 145 309 160 93
Street Canyon
Typical 2 5 2 1
Severe 14 30 16 9
On Fxpresswav
^VDical 6 13 7 4
Severe 26 55 28 16
3eside "xpresswav 5 11 6 4
Annual Average Exposure to U.S. Urban Dwellers (uq/m^)
Total 2.2 6.0 3.1 1.8
Ranqes are average values plus and minus' one standard
deviat ion.
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10
meteorological conditions, hut only represent the ambient
concentration at one or two particular monitor sites in each
city. The annual average urban exposures include a wide range
of individual activity pattern effects, but overall are only
based on exDosures in four U.S. cities. Because the two
modeling approaches were shown to be generally consistent in
Chapter 3 and the exposure estimates are more simple to
describe, they will receive the primary emphasis here.
As can be seen from Table 2, then, the estimate of annual
average urban exposure ranges from 1.8 to 6.0 ug/m^ depending
on the scenario chosen. These are significant levels compared
to the levels of the revised NAAOS for PM^q that the Agencv
is currently considering (aporoximately 55 ua/m3). Even
after post-1983 expenditures of nearly $2 billion (1982 Net
Present Value), roughly 100-150 areas would still not be in
attainment of such an NAAOS. A rough estimate would be that an
additional 4 ug/m3 in ambient Darticulate burden would cost
an additional $44-81 million per year (1982 dollars) in other
than mobile source attainment costs and result in an additional
13-33 non-attainment areas. Thus, the exposure impacts shown
in Table 2 are measurable and argue for further control of
diesel particulate emissions.
It is also useful to examine the source of these impacts.
Table 3 shows the distribution of urban emissions in 1995
between four cateaories of diesels: LDDVs, LDDTs, Tied ium-dutv
vehicles/light heavy-duty vehicles (MDV/LKDVs) (i.e., Classes
IIB-^I) and heaw heavy-duty vehicles (HHDVs) (i.e., Classes
VII-VIII). As can be seen, the two light-duty categories
contribute rouahly half the emissions under all the scenarios,
as do the two heavy-duty categories. Thus, control is needed
from both general categories if the ambient levels and
exDosures described in Table 2 (and the other impacts described
below) are to be reduced to the furthest dearee feasible.
2. Carcinogenic Health Effects
The results of the carcinogenic health effects analysis of
Chapter 5 are shown in Table 4 for the three diesel control
scenarios. As was done in the previous section, the urban
emission estimates of Chapters 2 and 10 were used to determine
the cancer risk estimates for the stringent scenario and the
other scenarios with stringent light-duty NOx standards. Due
to the basic uncertainties inherent in attempting to predict
cancer risk, values in Table 4 should be regarded only as best
estimates of risk relative to other proven carcinoaens.
Because of limited studies on the human carcinogenic potential
of diesel Darticulate, estimates are based primarily on results
of clinical tests performed on animals and lower organisms.
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Table 3
LDDV
LDDT
MDV/LHDV
HHDV
TOTAL
1995 Urban Diesel
^articulate Fniissions (metric tons)
Scenar io
Relaxed
36,800 (27%)*
21,800 (16%)
9,400 (7%)
67,*00 (50%)
135,600
Base
19,700 (27%)
11,700 (16%)
4,700 (7%)
36,100 (50%)
72,200
Str inaent
10,700 (26%)
5,900 (14%)
2,700 (6%)
22,600 (54.%)
41,900
Figures in parentheses indicate percent of total.
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Table 4
Comparison of Risks from Various Sources
Estimated Annual Risk • Exposed
Sources of Risk (risk/person-year) Pooulation
Commonplace Risks of Death
Motor Vehicle Accident
222 .0
X
10"6
Entire
U.S.
Drowning
26.0
X
io-6
Entire
U.S.
Burns.
21.0
X
10"6
Entire
U.S.
Tornados, Floods, Light-
2.0
X
10"6
Entire
U.S.
ning, Tropical Cvclones
and Hurricanes
Risks of Cancer Incidence
Diesel Particulate (1995):
Relaxed Scenario
3ase Scenario
Stringent Scenario
Natural 3ackaround Radi-
ation (sea level)
Average Diaanost ic Med ical
X-Ravs in the United
States
Freauent Airline Passenger
(4 hours per week
flv ing)
Four Tablespoons Peanut
Butter Per Day (due to
presence of aflatoxin)
Fthvlene Dibromide
One 12-Ounce Diet
Drink Per Day
Arsenic
Miami or New Orleans
Drinkina Water (due
to presence of
chloroform)
Luna Cancers:
For Smokers Due to
Smok ina
For General Population
Due to Causes Other
Than Smoking
1.6
0.8 x
0.5 .x
x 10~6
10-6
10~6
8.4 x 10-5
5.1 x 10~6
3.0 x 10~6
Urban U.S.
20.0 x 10-*
20.0 x 10"5
10.n x 10~*
8.0 x 10-5
419.0 x 10-*
73.9 x 10"5
Entire U.S
widespread
Limited
Fa i rlv
WidesDread
4.2
X
IO"*
widespread
2.6
X
io-*
Widespread
1.7
X
10-5
1% of U.S.
1.0
X
10-5
Southern
U.S., Urban
Entire U.S.
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13
As can be seen, the risk of contracting lung cancer from
exposure to diesel particulate appears small compared to many
of the other risks shown in Table 4. Yet the upper limits of
the diesel risk estimates under all control scenarios would
still represent 4--11 percent of all non-smokina related lung
cancer in the U.S. Even the lower limit of risk under the
relaxed scenario is above one out of a million, which has been
used by reaulatory agencies in the past as a yardstick for
determinina the need to reaulate. Thus, while the estimated
cancer risk is not tremendous, it is nonetheless measurable and
suggests the need for some dearee of control.
3. Visibility Impacts
¦"he visibility imDacts of the various diesel control
scenarios are presented in Table 5. The figures were generated
from the results of Chapters 2, 4, and in in the same manner as
the air quality and exDosure estimates of Table ?. The
assumption that visibility impact is proportional to emissions
does not apDlv as readily as it does for air Quality impact and
exposure, but the resultant inaccuracy is insignificant for the
pumoses of this report.
As can be seen, the most strinaent control scenario
provides a 2-16 percent improvement in visibility over the
least strinaent scenario, while the upper limit of this impact
is probably perceptible, it is more difficult to tell about the
lower limit. Differences between intermediate control
strategies would be much less than these absolute effects.
Thus, while the overall impact of diesel particulate on
visibility could be characterized as perceptible and deserving
of control, the chanae in visibility between the individual
control strateaies is difficult to characterize based only on
an analvsis of physical effects.
Mo attempt is made in this study to quantify the
visibility impacts into a dollar value. This is not meant to
imply that even a small dearadation in visibility due to diesel
particulate is not economically important. Such a benefits
analysis simDlv is not within the scope of this reDort.
4 . Soiling Impacts
As was evident from the soilinc analysis in Chapter 7,
little can be said about the Dhvsical effects of diesel
particulate on soilina based on a review of the scientific
literature. It is possible, however, that diesel particulate,
aram- for-aram, mav have a disproportionate effect on soiling
when compared to other types of particulate. Otherwise, little
information on soiling is available in the scientific
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14
Table 5
Average Peduction in Visibility Due to
Diesel Particulate in 1995 (Dercent)
Citv Size (population) Relaxed Base Str inaent
More than 1,000,000 24 15 9
500,000-1,000,000 10 6 4
250,000-500,000 7 4 2
100,000-250,000 5 2 1
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15
literature. Thus, no conclusion can be made concerning the
need to control diesel particulate based only on the physical
effects of soiling. A decision on this issue may .be possible
based on a review of the economic literature, but such a
benefits analysis is beyond the scope of this report.
5. Overall Evaluation
A number of conclusions can be drawn from the scientific
analysis of the four health and welfare effects of diesel
Darticulate emissions. One, the effect of diesel particulate
emissions on visibility and both carcinogenic and non-cancer
health effects are noteworthy, while the soiling effect is for
the most part unknown. Two, while these impacts are measurable
and argue for control, this analysis could not readily discern
the level of control at which these effects disappear and where
control is clearly sufficient. This is particularly true of
the cancer risk impact. Thus, while this analysis shows the
need for more control, it cannot alone be used to demonstrate
when sufficient control has been applied. In the absence of a
precise cost benefit analysis, such a decision can be made,
albeit less precisely, by considering the cost and cost
effectiveness of control. The groundwork for this is laid in
the next two sections.
B. Costs
The economic analysis performed in Chapter 8 identified
three measures of economic impact: 1) trap-oxidizer cost per
vehicle (coupled with a percentage of vehicles requiring
traps), 2) diesel sales reductions, and 3) nationwide annual
costs (or 5-vear costs) . These three measures are shown in
Tables 6-8 for the two more stringent control scenarios
relative to the relaxed scenario.
Table 6 shows both the cost to the consumer of equipping a
vehicle with a trap-oxidizer and the percentage of vehicles
reauiring traps. Both the first costs (traD-oxidizer system)
and the lifetime costs aoDear substantial on an absolute basis,
while on a relative basis they represent a modest 0.5-2 percent
increase. Under the base scenario, 48-70 percent of each
vehicle type will experience these costs, while nearly all
vehicles will be eauipped with traps under the stringent
scenario.
While consumers purchasing diesels will experience a
0.5-2.0 percent increase in transportation costs, these costs
will likely reduce the demand for diesel-powered vehicles.
Table 7 shows estimates of the sales reductions projected under
the various scenarios. For LDDVs and LDDTs, the impacts are
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16
Table 6
T'otal Cost to Consumers of Owning and Operatinq
a Liqht-lXity Diesel Equipped With a Trap-Oxidizer
and the Percentage of Vehicles Requiring Traps (1983 dollars)*
LDDVs
LDCTTs
MDVs
LHWs
HHDVs
Trap-Oxidizer System:
$185-213
$187-211
$363
$556
$652
Maintenance Costs
$22
$22
$22
$44
$44
Maintenance Savings
($21-36)
($22-36)
($39)
($61)
($97)
Cost of Fuel Economy Penalty
$33-52
$41-55
$126
$386
$917
Total Cost to Consumer:
$219-266
$229-252
$472
$925
$1,516
Total Cost of Owning and
Operatinq Vehicle
$19,418
—
—
—
$274,911
Cost Increase IXie to
Trap-Oxidizer
1.4-1.5%
—
—
—
0.6%
Vehicles Requiring Traps (%)**
Base Scenario
Stringent Scenario
47.6
95.1
56.2
94.7
70
98
70
98
70
98
All costs are discounted to year of vehicle purchase using a 10 percent
discount rate.
Presumes the availability of averaging for all vehicle classes and stringent
1.0/1.2 g/mi NOx standards for LDIT/s and LDDTs, respectively. Also that the
current fleet composition is retained in the future.
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17
Table 7
Diesel Sales Reductions*
Base Scenario
Stringent Scenario
1987 1990 1995
LDDV 7.4% 5.4% 4.8%
LDDT 10.1% 7.9% 6.7%
MDV** 3.4% 3.4% 3.4%
LHDV 1.5% 1.5% 1.5%
HHDV 0.7% 0.7% 0.7%
LDDV 11.1% 7.2% 7.9%
LDDT 14.7% 11.6% 9.7%
MDV 4.8% 4.8% 4.8%
LHDV 2.2% 2.2% 2.2%
HHDV 1.0% 1.0% 1.0%
Presumes the availability of averaqinq for all vehicle
classes and stringent NOx standards for LDDVs and LDDTs.
Estimates for MDVs, LHDVs, and HHDVs are based on
estimated elasticities which are not time dependent.
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18
substantial: 5-15 percent. However, nearly all these lost
diesel sales should be made up by increased sales of
gasoline-fueled vehicles. Since all LDDV and LDDT
manufacturers also produce gasoline-fueled vehicles, none
should necessarily suffer a significant loss of sales.
The question arises as to whether these sales reductions
would force any particular manufacturer out of the LDD market
entirely. This cannot be answered definitively, given the
recent volatility of the LDD market. If the diesel penetrates
the market as projected under the best sales estimate used in
this report (10 oercent for LDDVs, 30 percent for LDDTs), it is
doubtful that any manufacturer would be forced out by a 5-15
percent drop in diesel sales. On the other hand, if diesel
sales, particularly LDDV sales, did not reach these levels,
then such reductions could cause some to leave or never enter
the market.
The Drojected sales reductions for heavy-duty diesels are
considerably smaller than those for LDDs, though they are
probably more crone to error. The aporoximate loss of one
Dercent for HHDVs is very small. The losses in the other two
subclasses (MDVs and LFDVs) are larger, ranaing from about 2-12
percent. However, in these lighter two subclasses, a sizeable
portion of the lost diesel sales would aaain be made uo bv
sales of gasoline-fueled vehicles and the diesel fraction of
sales within these two subclasses should still increase
markedly. Thus, in general the HDD sales impacts are probably
insianificant.
One caution should be made concerning these costs and
sales imoacts. They presume that the only control technology
available to reduce particulate emissions is the
traD-oxidizer. As will be seen in Section III, other
techniques are available which are less costly, but which
cannot provide the same degree of reduction as trap-oxidizers.
Thus, the cost of standards less stringent than those of the
base scenario may be substantially less than those shown in
Tables 6 through 7 and may not have associated with them the
concerns indicated above. Also, the use of these less costly
techniaues will also reduce the costs and .economic impacts
associated with the base and stringent scenarios as well,
particularly the former. This will be considered in greater
detail in both Sections III and IV.
C. Cost Effectiveness
The cost-effectiveness analysis of Chapter 9 identified
two methods for comparing the cost effectiveness of various
controls. Amona mobile sources, an urban based cost
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19
effectiveness appeared adeauate. When both stationary and
mobile sources are involved, an air ouality discounted cost
effectiveness aopeared to be. more appropriate, though still not
entirely adequate.
The results of the mobile source comparison are shown in
Table 8. As can be seen, except for MDVs, the cost
effectiveness of all the vehicle classes is very similar under
both the base and stringent scenarios. Thus, any preference
for control based on cost-effectiveness considerations would be
very small, and, practically speaking, need not be considered.
One caution should be mentioned. The cost effectiveness
of both scenarios for LDDVs and LDDTs is very dependent on the
level of their NOx standards. If higher NOx standards were
considered (e.g., 1.5 and 1.7 a/mi, respectively), the dollar
per ton figures would nearly double due to the lowering of
engine-out particulate levels. This aspect will be considered
later in Section IV of this chapter as the possibility of
higher NOx standards are considered.
The results of the cost-effectiveness comparison between
stationary sources and mobile sources contained in ChaDter 9
showed diesel particulate control to be cost effective relative
to stationary source control when air quality impact was
considered. However, other imoortant parameters, such as the
ability to focus control in those areas needing it, could not
be included and these could significantly affect the outcome of
the analysis. At this point, then, all that should be said is
that there is no evidence that diesel particulate control
should be avoided due to the better cost effectiveness of
stationary source control.
III. tdentification and Assessment of Viable Control Potions
The purpose of this section is to review all available
techniques for controlling diesel particulate emissions,-
formulate specific control options, and assess their relative
technological feasibilities and costs (if not already addressed
above). This will be done in two parts.
The first part will review conventional techniques
available for diesel Darticulate control (i.e.,
hardware-oriented techniques applied to vehicles nationwide) ,
first for light duty and second for heavy duty. Discrete
levels of control will be identified and their relative
feasibility and costs discussed. The second part will present
a number of more innovative possibilities for HDD particulate
control, including fuel-related techniques and controls
oriented toward urban fleets.
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Table 8
Urban Based Cost-Effectiveness Relative to the
Relaxed Scenario (1983 dollars per metric ton).fl]
Base Scenario Stringent Scenario
LDDV 15,400 18,900
LDDT 16,100 17,300
MDV 20,000 20,000
LHDV 11,000 11,000
HHDV 11,000 11,000
Presumes
str inaent
averaainq for
NOx standards
all classes were applicable
for LDDVs and LDDTs.
and
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21
The available control techniques for LDDVs and LDDTs are
discussed together because of the great similarity of their
engine/vehicle designs and their usage patterns. • Ml of the
evidence generated over the past 10 years, for both
gasoline-fueled and diesel-powered vehicles alike, has
demonstrated that LDDVs and LDDTs can meet essentially the same
emission standards; the LDDT standards only requiring a small
upward adjustment based on their heavier maximum weight.
The same approach is taken toward HDDs, where trucks and
buses of vastly different sizes are grouped together for the
purpose of discussion. ^ere again, with the oossible exception
of trap-oxidizers, the available control technology is
applicable across the board to all HDD engines/vehicles. With
respect to trap-oxidizers, it may be an easier technological
task to apply these devices to the smaller, lighter HDDs than
the huge tractor-trailers. However, as indicated in Table 3,
even including all HDDs up through Class VI in this "lighter"
grouping affects less than 10 percent of total urban diesel
emissions. If the control technoloaies applicable to these two
subclasses were more clearly different and the lighter subclass
had a more substantial emission reduction ootential, then it
may be desirable to regulate them separately. However, since
this is not the case under the conventional control options,
they are treated toaether below. in the section discussinq
innovative control options, their potential for separate
regulation in examined.
A. Conventional Options
1. Light Duty
The options available for the control of LDD oarticulate
based on hardware-oriented techniques are fairly
straightforward, because the available control techniques are
few in number. Movina from least stringent to most stringent,
there are four possibilities.
One, no control beyond that already aoplied can be
required (i.e., the relaxed scenario). This approach would
result in various particulate standards deoendina on: 1) the
level of the NOx standard, and 2) whether averaaina is made
available with such a relaxed standard. Table 9 presents the
corporate averaqe particulate levels for LDDVs and LDDTs under
strinqent MOx standards (1.0 g/mi and 1.2 q/mi, respectively)
and averaging. While fleet average emissions would be 0.42 and
0.52 g/mi, resoectively, the particulate standards would have
to be higher to accommodate higher than average manufacturers
(0.60 a/mi for LDDVs and 0.56 a/mi for LDDTs). without
averaaina, the standards would have to be higher still, as
shown in Table 9.
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Table 9
Individual and Overall Current Corporate
Average Particulate Standard Levels for
LDDVs and LDDTs Under Option 1 (grams per mile)*
Manufacturer LDDV
General Motors .50
Volkswagen .21
Nissan .29
Mercedes-Benz .60
Isuzu .22
Aud i .26
Peuaeot .36
Volvo .41
Sales-Weiahted .42
Industry Wide
Average
Resultant Averaging 0.60
S tandard
Resultant Non- 0.63
Averagina Standard
Manu facturer LDDT
Ford .30
General Motors .56
Isuzu .33
Nissan .37
Mitsubishi .43
Toyota .20
Volkswagen .32
Toyo Kogyo .30
Sales-Weighted .52
Industry-wide
Average
Resultant Averaging 0.56
Standard
Resultant Non- 0.64
Averagina Standard
~
Presumes stringent NOx standards of 1.0/1.2 g/mi for LDDVs
and LDDTs, respectively, and the current fleet composition.
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23
Two, a moderate degree of additional control could be
obtained via non-trap technology (i.e., between the relaxed and
base scenarios). For example, electronic fuel injection and
sophisticated electronic exhaust gas recirculation (EGR)
systems (to reduce .negative impact of stringent NOx. standards)
appear to be available and able to provide some control. There
is also the possibility that certain high-emitting engine lines
may be dropped in this timeframe due to fuel economy and other
pressures. Overall, these techniques could significantly
reduce particulate emissions from the levels shown in Table 9,
depending on the manufacturer and the desired stringency. As
determined in Chapter 10, particulate standards under this
option would be approximately 0.30 g/mi and 0.35 g/mi for LDDVs
and LDDTs, respectively.
•Three, the current trap-based standards of 0.20 g/mi and
0.26 g/mi for LDDVs and LDDTs, respectively, are potential
candidates (i.e., the base scenario). As indicated above,
these levels may be achievable without traps by some or even
most manufacturers with extensive use of non-trap technoloav,
even with stringent NOx standards. However, some use of traps
would be likelv, esoeciallv if the higher emittina General
Motors Corporation (GM) and Mercedes-Benz models remained in
production.
Four, full trap-based standards of 0.08 a/mi and 0.105
g/mi, respectively, comprise the most stringent option (i.e.,
the strinqent scenario). These standards would require traps
on essentially all vehicles unless some unforeseen breakthrouah
occurred in enqine-related technoloav. Mon-trap technology
would not be as desirable under this option, from the
,:.manu.f a.c t'U-C-e-r-Vs. ^po.i.nt. of,, .^iew.,., ..since^^in. _. any.. ..case ^,;t;he.. • qreat,^..
'majority-of vehicles-' wou-ld still require traps~.'-» -
The first option would of course be technoloqicallv
feasible since no new technology would be required. (The
NOx/particulate trade-offs used to convert particulate levels
under the current NOx standards to those under the strinqent
NOx standards assume only the use of current EGR systems and-
their associated particulate penalties.)
The second option would also- be relatively easy to
demonstrate as beinq feasible. As discussed in Chapter 10,
sophisticated EGR systems are available and are already beina
applied on a few 1984 vehicles in California to comply with
their 1.0 q/mi NOx standard. These svstems should be able to
reduce the particulate penalty associated with the strinqent
NOx standard bv one-half. while the effect of electronic
injection is uncertain, it should provide a benefit for the
hiqhest emittinq enqines; at least again improving the
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24
NOx/particulate trade-off. Finally, it appears almost certain
GM will drop their 5.7-liter engine by 1987 of their own
accord. (GM has already dropped this engine from its 1984
California model line and has indicated its intent to
discontinue this engine Federally beginning in 1986.) This
single change would have a drastic effect on their corporate
average emission level and .wo:uld.:.-significantly reduce the
number of traps required under this scenario.
- -The -third option is -basically—an extension of the second,
technologically. However, a-s-- these—standards- would probably
be lower than that achievable via non-trap technology, the
likelihood of traps being necessary would be a distinct
possibility, and would need to be addressed. The record for
trap-oxidizer feasibility on LDDs, though, is already well
established. Thus, this option is feasible.
The fourth option, too, only requires that traps be
feasible. However, because highly efficient traps would be
required on nearly all vehicles, some additional leadtime
beyond 1987 would appear to be necessary. (California is not
reauiring this level of control until 1989.) However, the
basic feasibility of these levels does not appear to be in
question.
Concerning the costs of these options, the only cost not
identified in Section II was that of the non-trap technology.
The cost of electronic fuel injection can be substantial (i.e.,
$100). However, there are other benefits involved besides
e'mrssiion r" contro 1; ; sueh"x • as 'improved-- • fuel ', -economy'" and
performance. " As some" manufacturers" are "already planning to
applv this technologv on their enaines, it is evident that
these non-emissions related concerns justify most if not all of
this cost. Thus, this technology should not be costly from the
point of view of emission control. In addition, the primary
cost of a sophisticated EGR system would be the electronic
control unit already included in the cost given above for
electronic fuel injection. Thus, this technique should also
have a modest net cost. Overall, the portion of hardware costs
associated with emission control should be about $25 per diesel
vehicle. As such, the urban cost effectiveness for this
scenario aDpears to be very good at about $2,500-$3,500 per
metric ton.
2. "eavv Dutv
The conventional control options available for HDDs are
more complex than those for LDDs. This is due to the fact that
the CAA contains strong mandates for the control of both HDD
particulate and NOx emissions While the ultimate level of the
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25
HDD NOx standard is specified in the CAA, the technology is not
available to achieve that level. Thus, the CAA provides that
EPA set stringent interim NOx standards based on criteria
similar to those specified for the particulate standards. This
is unlike the light-duty situation, where the NOx standard is
specified in the CAA.
Despite this difference, generally speaking there are the
same four options available for HDD particulate control as were
identified for LDDs with the. added complexity resulting from- a
variable NOx standard. These four options are examined below.
The first option is again no, or little, further control
(i.e. the relaxed-scenario). While current HDD particulate and
NOx levels are around 0.7 and 7 grams per brake horsepower-hour
(g/BHP-hr), respectively, testimony at a public hearing on this
issue identified 0.6 and 6.0 a/BHP-hr as reasonable, very,
short-term standards that would require a minimal amount of
very basic, engine-related control (e.q., injection timing and
injector design). Thus, it does not appear necessary to
consider higher levels. The 0.6/6.0 q/BHP-hr levels could be
shifted somewhat toward lower particulate or lower NOx levels
if a strong priority existed for one or the other. However,
the 6.0 g/BHP-hr level probably represents the reasonable limit
for short-term (i.e., 1987-88) NOx control without severely
impacting particulate levels and, likewise, the particulate
reduction achievable from raising the NOx standard would not
justify the increase in NOx emissions. Thus, these levels
represent the practical levels for short-term particulate and
NOx standards using readily available technology.
The levels associated with more advanced non-trap HDD
con.tr©l.» techno 1.ogy-•;(i-er.r1he;.~second •; 'opt-iqn, .• befcween ~the -ba'-se**
arid' ' relaxed scVnar id's'i'•"-'are "more difficult" to pinpoint" tti'a'rf
those for light duty because less data are available.
Electronically controlled fuel injection, adiabatic enqine
techniques, and advanced EGR appear to have the most promise.
(Oxidation catalysts are probably not feasible here due to the
low exhaust temperatures of HDDs.) An estimate of the maximum
effectiveness of these concepts is that they could reduce
emissions down to particulate and NOx standard levels of 0.4
and 4.0 g/BHP-hr, respectively, giving equal weighting to both
particulate and NOx control. It is doubtful if more NOx
control could be obtained even allowing some increase in
particulate levels, due to engine durability and fuel economy
concerns. However, if achieved, such additional NOx control
would almost certainly bring with it large increases in
particulate emissions, well above 0.6 g/BHP-hr. If the greater
weight were given to particulate control, levels around 0.3
g/BHP-hr would probably be achievable. However, NOx levels
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26
would almost certainly increase to 5.0-6.0 a/BHP-hr. This
would mean that NOx emissions would increase 10-20 metric tons
for every metric ton of particulate reduced. Given -the present
acid rain and ozone problems, this does not appear to be a
desirable trade-off. Thus, the simultaneous reduction of both
particulate and -NOx emissions appears more reasonable than a
•trade-off- of the control of one pollutant for the other, -and
0.4 and 4.0 g/BHP-hr, respectively, will be considered the most
stringent standard levels associated with the second option.
- - -Analogous ¦--to ¦ the - third - -LDD-- option (i.e., the base
scenario) is the 0.25 g/BHP-hr standard currently proposed for
HDDs in 1986. As implied in the discussion of non-trao
technology above, this level, even more than the 1987 LDD
standards, is dependent on the use of traps. it does not
appear feasible for non-trap controls to even approach this
level. However, with the application of traps, the level of
the NOx standard becomes more flexible. Traps, in general, are
sufficiently efficient to provide compliance with the 0.25
g/BHP-hr standard with engine-out particulate levels of even
1.0 g/BHP-hr. Assuming the availability of averaging, the only
effect of additional NOx control would be an increased number
of traps which had to be applied. However, fuel economy and
durability penalties associated with NOx standards below 4.0
g/BHP-hr would still prevent lower NOx standards from being
practical. Thus, 4.0 g/BHP-hr will represent the NOx standard
associated with the trap-based standards as well as the Option
2 non-trap standard.
i- lira"!l"y:, f u 11;,;« s£r ap* b-a.sed1 -level"1-- ( ive;.y-rthe
stVingent ~ scenario). Assuming" a "sta'rting" "point of 0.6"
a/BHP-hr, a particulate standard of 0.1 a/BHP-hr should be
attainable with high-efficiency traps on essentially all
engines. The NOx standard associated with this option would
again be 4.0 g/BHP-hr, not because of the need for particulate
control, but because of fuel economy and durability
considerations.
The feasibility of the first option, 0.6 and 6.0 g/BHP-hr
for particulate and NOx, respectively, is relatively
straightforward and achievable by 1987. This would represent a
2-year" delay with respect to the CAA mandate that a 1.7
g/BHP-hr NOx standard (or an alternate standard representing
the technologically feasible limit) be implemented by 1985 and
a 6-year delay of the CAA mandate that a particulate standard
be implemented by 1981. In addition, the 0.6 and 6.0 g/BHP-hr
standards would not represent true technology-foreing
standards, as indicated by the Act. However, they do represent
the feasible limit given the leadtime available. Since the
promulgation of such standards cannot take place prior to early
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27
1985, the minimum leadtime of 4-years also mandated by the CAA
would not be available. However, this 4-year leadtime was
intended by Congress to be associated with a technology-forcing
standard, which as indicated above, is not the case here. As
outlined in the Agency's position when it implemented the 1984
HC and CO standards for heavy-duty engines, when the model year
mandate for implementina a such standard has been missed,
implementing the standard at the earliest reasonable date takes
precedence over the 4-year leadtime. requirement, provided that
sufficient leadtime is available, which is the case here. In
fact, manufacturers have had notice of even more stringent
standards since January of 1981 when the 0.25 g/BHP-hr
particulate standard was proposed for the 1986 model year and
advance notice was given of a 4.0 g/BHP-hr NOx standard" for the
same model year.
The demonstration of the feasibility of the second option,
0.4 and 4.0 g/BHP-hr without traps, however, is more difficult
and would require leadtime in line with the 4-year requirement
of the CAA. None of the three control techniques associated
with this option, electronic fuel injection, electronically
controlled EGR, or adiabatic combustion techniques, have yet to
be commercialized on HDD engines, though the first technique
will appear on portions of manufacturers' fleets as early as
1986 and on a majority of HDD engines by 1988. However,
implementation of the other two control techniques is further
away. Because of durability concerns in the HDD industry, it
is sometimes difficult to require basic engine modifications
without grantina leadtime for necessary durability evaluation.
Thus, it would not appear feasible to reauire the application
of such techniques until 1990, which would be the year for a
••revised; 'NOx: standard;;,.if j,the ' f ir.st"s.tAn^aVd,'^
1987 "Even' with' this lead time," 'it would not" b"e easy to firmly
demonstrate at this time the feasibility of a 33 percent
reduction in both NOx and particulate emissions. However, at
the same time, it should be difficult for the industry to argue
their infeasibility given the mandates in the Act, the years of
leadtime available, and the fact that these concepts have been
tested on prototype engines and have shown substantial emission
reduction potential.
Both the third and fourth ODtions depend on the
feasibility of trap-oxidizers. While the basic feasibility of
trap-oxidizers for HDDs is not in question, the development of
HDD trap technology appears to be significantly behind that for
LDDs. There appear to be a number of technical reasons for
this. One, the exhaust characteristics of HDDs make it much
more difficult to initiate and control regeneration compared to
LDDs. HDD exhaust is generally cooler, of much greater volume,
and both temperature and volume are subject to wide
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28
fluctuations due to the more extreme operating conditions seen
by larqe trucks relative to those of cars. Two, the extremely
lonq life of HDDs also requires a more durable trap system.
Three, the importance of fuel economy to commercial operators
mav be a significant impetus to tamoer, since traps, will cause
some fuel economy penalty (possibly 1-3 percent) due to
increased backpressure. This last difficulty is Dotentially
the most important, since it is unlikely that the fuel economy
penalty can -be removed-.throuqh further development.
There appears to be a regulatory reason, as well, why HDD
--t-raD - development—i.s--behind that for- LDDs-. Trap-based LDD •
—particulate standards were proposed - in- 1979--and- promulgated - in
1980. These actions communicated a serious regulatory intent
to the LDD industry and a commitment to the degree of emission
reduction achievable via trap technoloay. Even the requlatory
relief program of 1981 focused on delay and not relaxation. A
commitment to reevaluate the need for the standards was made
(this study is the fulfillment of that commitment) , but it was
never communicated that the study had a prejudged outcome
(i.e., relaxation). Rather, it was emphasized that the study
would be highly technical and objective. The result has been
continuous progress in LDD trap development, even thouqh it has
been difficult to obtain a clear picture of the manufacturers'
progress since they have a strong incentive to withhold such
information.
In contrast, EPA did not proDose a trap-based HDD
particulate standard until 1981, and then almost immediately
susDended regulatory activitv in. this area for a year and a
half. After holding a hearing on the proposal in mid-1982, EPA
;'a nn dunked :i~t would -xepropos.e th;e~t,pa:rt icura"t e'::L£ta:ndard"; the,
proposal "of r the "HDb^NOx " standard"*, wh ich is " how scheduled ""'for'
Summer of 1984. Thus, the Agency has not conveyed a strong
requlatory intent, but rather one of accommodation.
As a result, the trao-development orograms of the HDD
manufacturers with one exception, are years behind those of the
LDD manufacturers. For example, two of the five major domestic
HDD manufacturers have done little trap testing to date, while
two others are still focused on bench testinq. Little actual
engine or vehicle testing has been done and the focus of the
effort is as much to raise problems as to solve them. Only one
HDD manufacturer is known to have proceeded actively in trap
development, taking full advantage of available LDD experience.
Nonetheless, even though EPA proposed a trap-based
partculate standard in 1981 and Congress mandated strong
controls for the 1981 model year, it is clear technologically
that more time is needed beyond 1987 or even 1988 to implement
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29
traps on HDDs. Sufficient leadtime is probably available for
1988 or 1989, at least until a later date when further progress
can be assessed. Thus, the standards of either the third or
fourth options could probably be implemented as early as the
1989 model year or more certainly for the 1990 model year. The
statutory framework for the setting of the NOx standard
requires a revision of the standard every three vears (until
the 1.7 a/BHP-hr level is reached). Thus, if the first option
were implemented in 1987, 1990 would be the first possible year
for a revised NOx standard and would also allow a reasonable
amount of leadtime for trap introduction.
Concerning costs, again as with LDDs, the only cost not
yet identified is that associated with the non-trap technology
of the second option. Here the costs of this technology are
more difficult to identify than they were in the LDD situation,
because adiabatic techniques, electronic fuel injection, and
EGR could involve fundamental chanqes to the engine or fuel
system and their cost is difficult to identify. Fortunately,
an answer may lie in the fact that manufacturers are moving
toward implementing these techniques in the late 1980's or
early 1990's even without impetus from emission standards.
Thus, their cost attributable to emission control should be
small, aiven sufficient leadtime, and they should be cost
effective.
B. Innovative Control Options
The search for innovative strategies for the control of
HDD particulate emissions was a result of three factors. One,
HDD particulate emissions constitute the major portion of total
urban dieseJL particulate emissions. Two, traps. do npt agp.ear...
•• yberfX6.„.for' • • HDDs ... pr-Lp:'r<- * to,• l&8v9..-.-and ie.v'en :th;a't-
in-use tampering may be a problem. Three, less than 30 percent
of all HDD Darticulate is emitted in urban areas, although this
minority of HDD particulate emissions still represents more
than half of all urban diesel particulate emissions. The
logical conclusion is that: 1) major reductions in a sizable
portion of the urban diesel particulate emission inventory will
not be achievable in the near term, and 2) even in the long
term, the traditional strategy of controlling all vehicles sold
nationwide will, in a sense, be somewhat inefficient. This led
to a search for strategies for controlling HDD particulate
emissions specifically in urban areas only.
Two strategies appear to have merit. One would
selectively reguiate those types of HDDVs which are heavily
urban-oriented (an urban vehicle option), apDlying lesser
control to those which are rural-oriented. The other would
selectively regulate urban fleets (an urban fleet option) ; it
being easier to monitor maintenance with fleets and fuel
modification becoming a possibility due to their captive
fueling capability.
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30
The selective regulation of urban-oriented HDDVs would
require the differentiation of vehicle types based on objective
criteria that would not be easily modifiable (i.e., weight,
number of axles, length, general description of load carrying
portion, etc.) . Two or three vehicle types come to mind as
heavily urban oriented: transit buses, garbage trucks, and
_cement mixers. An analysis of their use nationwide shows that,
if one assumed their use was entirely urban, then their vehicle
miles travelled (VMT) would represent rouqhlv 20 oercent of all
¦ HDD urban VMT, with transit buses- ..representing slightly more
..than half of this figure. At the same time, the great majority
of the remaining HDD VMT nationwide is associated with very
general types of vehicles, such as panel trucks and flatbeds,
which would definitely be used in both urban and rural areas..
To affect these vehicles, weight classes could be used. One
option would be to include all HDDs in Class VI or below. Such
vehicles would be expected to expend rouqhly half of their VMT
in urban areas, so their control would be as cost effective
from an urban/rural point of view as that of LDDs. Their
inclusion would increase the percentage of affected HDD urban
VMT bv 20-30 percent, to a total of 40-50 percent.
In addition, there are certain cities where bus usage
alone represents a sizeable majority of HDD VMT. For example,
bus VMT represented roughly 60 percent of all 1980 HDD VMT in
Mew York City and Chicago. (In contrast, the same figure for
Los Anaeles was 4 percent.) However, the dieselization of the
smaller HDV classes will reduce these fractiqns in future
years. Again for example, bus VMT is projected to represent 33
-~ • p"eree;n'tv-of 2000;; HDD.~;_VMT —ir^ .¦New_ York City ^and Chicagqy
r ~ rVspictfv'eiy,'"'H3'Iffedrias^ ' o'£'~'6he-tfiTrd'"" to "bn:e-h'al"f r'Vm'^curren't •
levels, but still sianificant fractions. An additional reason
to focus additional control on transit buses is the fact that
they are publicly operated and are heavily subsidized by the
Federal government. It would appear to be particularly
appropriate for these buses, which serve the public interest,
to demonstrate the ability of technology to control the very
apparent particulate emissions of diesel engines. Thus, there
is some potential for a large degree of additional control in
particular cities, and for a significant degree of control in
other cities via an urban vehicle option, as well as a certain
approDriateness to focus control on transit buses.
The second strategy, instead of identifying vehicles by
functional design, focuses on user type and location (i.e.,
urban commerical and public fleets) . This strategy has . the
advantage of affecting nearly all urban-oriented diesels. The
difficulty arises in defining an urban fleet and enforcing the
requirement. A fleet may be located in an urban area but
involve almost entire.ly over-the-road operation (e.g., most
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31
tractor-trailer fleets are located in suburbs). Thus, weight
limitations or other means of distinguishing certain trucks may
need to be added to address this problem. Also, there is a
reliance on the HDD purchaser buying the proper vehicle from
the dealer. Since most dealers sell to both urban and
non-urban users, deception or conscious manipulation would be a
definite possibility. Finallv, this strategy could create
enough incentive to cause a firm to relocate.
Despite these problems, this strategy should have the
ability to address the large majority of urban HDD emissions.
While figures are not readily available on the relative mileage
of fleets versus total vehicle usage, the three vehicle types
mentioned above for the first strategy would definitely be
included plus even larger utility, city, and delivery fleets.
Thus, a sizeable majority of urban HDDs should be affected.
Both of these urban strategies would also have a second
advantaoe over the conventional nationwide control apDroach.
while selective regulation could be oriented toward requiring
more stringent emission controls to be Dart of the engine or
vehicle, it could also be oriented toward requiring a cleaner
fuel to be used, since urban fleets usually have their own
fueling facilities. Gasoline, for example, would certainly be
cleaner with respect to particulate emissions. However, a
large fuel economy penalty would be involved and emissions of
lead would increase, at least until these vehicles are equipped
with catalysts. A better alternative would appear to be
methanol. Methanol engines have little or no particulate
emissions,...-.1 ow ..NOx.^...emissions^and, p.§.n .have fuel ..efficiencies,
aopr.o.achihq those :of' -the : diesei.. .._And, while methanol . Si-Sr.-
currently not available at service stations, it is readily
available in bulk quantities and could easily be bought and
used by fleets with their own facilities.
Enqine manufacturers could certainly produce a methanol
engine if there was a market for them. A German manufacturer,
M.A.N., already has a production-ready methano1-fueled diesei
engine and Detroit Diesel has recently developed a
methanol-fueled diesei bus enqine under contract to the
California Energy Commission for fleet testing in San
Francisco. Given the current and projected future qlut in the
methanol market (100,000 to 200,000 barrels per day), fuel
supply should also not be a problem. Roughly 67,000 barrels a
day of methanol would be required to fuel every transit bus in
the U.S. Since conversion to methanol would only occur through
the purchase of new buses, it would take a number of years for
even half of the bus fleet to convert and the present methanol
supply should be more than sufficient.
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32
The question is simply one of cost, primarily of the
fuel. A methanol engine should cost approximately the same as
a diesel, and its fuel efficiency should also be roughly the
same. However, methanol is likely to be more expensive on an
energy and mileage basis. Overall, then, a switch to methanol
would likely increase operating costs, at least as compared to
current petroleum prices.
To~ "estimate th-is* cost-,- estimates of the prices of both
diesel fuel and methanol are needed. No. 1 diesel fuel
currently costs roughly $0.90 per gallon delivered to a transit
~ authority, _ without tax'. Methanol is currently _available for
$0 745-0.50 per "gallon" on the gulf coast. Both of these prices
are depressed because of the depressed worldwide economy, but
methanol the more so, its price being 30-35 percent below that
of two years ago. Even though a methanol production surplus is
projected through the rest of this decade, it should not be as
severe as the current situation and the price will likely
increase in terms of 1983 dollares. Due to the uncertainty in
the degree of this increase, a range of $0.50-0.70 per gallon,
including bulk distribution, will be used.
Transit buses obtain a fuel economy of about 5 miles per
qallon on No. 1 diesel fuel. Since methanol contains only 44.5
percent of the energy per gallon of No. 1 diesel fuel, the fuel
economy of a methanol-fueled bus would only be 2.2 miles per
gallon. Assuming the relative fuel prices remain steady in the
future, the fuel costs of a diesel bus would be rouahly $0.18
per mile and that of a methanol bus would be $0.22-$0.31 per
mile, or 25-75 percent higher. At 30,000 miles per year, this
translates . into-.an-.-¦-annual-cost.,of, _,,using methanol • . of
... L;Jv2do-!-$3v9'Q veoc-r~a net** present' valu'e * lifetime"-'"cost
(15 years) of $9,100-529,700 in the year of vehicle purchase.
With fuel costs being 8 percent of overall costs, a switch to
methanol would increase the overall cost of operating a bus by
2-6 percent.
However, it is important to consider that a
methanol-fueled bus engine would meet any particulate and NOx
standards conceivable for diesel engines without any additional
hardware or adjustments. Thus, the cost of bringing a diesel
enaine to these levels must be considered. For particulate
control, a trap would certainly be necessary at a cost of
$600-700 initially, and a 2-percent fuel economy penalty. For
NOx control, severe timing retard or an exhaust gas
recirculation svstem would be needed, costinq $0-200 initially
and a 5-10 percent fuel economy penalty, and yet still not
achieve the level of the methanol engine. Overall, these
control costs would increase the overall costs of owning and
operating a diesel bus by $460-770 per year, or $3,500-5,800
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33
over the "life of the bus (net present value in year of vehicle
purchase) . Thus, it would appear that the methanol option
would still be more costly, though it should be more easily
achievable technically and provide greater NOx control.
One final point bears heavily on the relative economics of
using methanol versus diesel fuel. If the price of diesel fuel
rises more rapidly in the future than that of methanol, which
is possible, at some point methanol will be less costly to
use. However, predictinq future petroleum prices is beyond the
scope of this study.
One method to at least partially avoid the issue of cost
would be to implement a particulate standard for urban vehicles
which could be met with either trap-oxidizer technoloqy or
methanol. Methanol engines could easily be feasible by or even
before the feasibilitv of traps. Thus, enqine/vehicle
manufacturers would have a choice as to how to meet the
standards, via traps or methanol, and the overall approach
would involve less risk than if either one were the only
potential option. Even if traps are eventually used, this
strategy would be 3 to 4 times as cost effective as a
nationwide trap-based strategy.
Of the two options, the urban-vehicle (buses, garbage
trucks, cement mixers) strategy appears to be preferable,
primarily because it avoids the implementation and enforcement
problems of the urban-fleet strategy. The cost issue still
needs to be addressed in further depth. However, the potential
for significant, cost-effective emission reductions is
present. For example, either trap technology or methanol could
provrd;e~ compliance- with a -Q-.25 - g/BHP-hr. •standard"...-;T/Nat'i'Onwid:e'p
assuming such " "engines justcomply with "'tnl 0.25 q/BHP-'tiif'
standard, this strategy could reduce 1995 HDD urban emissions
from 55,000 metric tons per year to 41,000 metric tons per
year, or by about 20 percent, compared to a 0.40 g/BHP-hr
standard for all HDDs. Even oreater reductions would be
achieved if methanol engines were chosen as the compliance
strategy, since these engines should emit well below 0.25
a/BHP-hr particulate. Thus, this approach merits further
consideration.
IV. Discussion of Control Potions
The previous section laid out the available control
options for both LDDs and HDDs, including two innovative
control strategies for HDDs. In this section, these options
will be compared and evaluated and, where possible, conclusions
drawn. As in the previous section, LDD control options will be
discussed first, followed by those for HDDs, as the analyses in
each area are for the most part independent.
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A. Light Duty
The summary of environmental impacts in Section II
demonstrated a need for further control beyond the relaxed
scenario. It also showed that LDDs were roughly half the
problem (i.e., contributed half of the emissions). a need to
control LDD emissi ns beyond current levels was evident.
The analysis _n Section II identified three further levels
of control beyond current emission levels; speaking in terms of
LDDV standards, 0.25-0.3 g/mi", 0.2 g/mi, and 0.08 g/mi. All
three standards are demonstrably feasible, thouah the 0.08 g/mi
level would probably require some time beyond 1987 before
implementation, even with the availability of averaging.
At the same time, the summary of costs in Section II
showed potentially significant economic impacts for the
traD-hased standards if the trap-oxidizer were the only control
technique employed. While both the initial and lifetime cost
impacts are only about 2 percent of vehicle purchase cost and
total lifetime cost, this small impact can have a sizeable
effect on sales of a consumer alternative like LDDs, since
their desirability is very sensitive to small relative economic
changes. As was seen, equipping all vehicles with traps could
reduce LDD sales by 7-15 percent. This is a sizeable reduction
even considering the fact that most of these lost sales would
be made up by sales of gasoline-fueled engines.
Table 10 summarizes the. urban, emisslions, -various. cost,
lijiformation, Vu,rBancq|'t'i*ef>£ectJ.Cv^e-s"s--for -.-the four -frD©'
control options. The values presented in this table differ
somewhat from those shown in Section II primarilv because the
voluntary elimination of GM's 5.7-liter diesel engine is
assumed here. Urban emissions are shown in Table 10 as an
indicator of environmental effects since all of the health and
welfare impacts discussed in Section II are essentially
proportional to urban emissions.
As can be seen, there is a fairly steady and consistent
change in emissions from option-to-option. The cost and sales
impacts trends are also reasonably steady. The second option
should have a fairly low cost due to the other benefits
associated with the use of electronics (e.g., improved fuel
economy, electronic capability for peripherals, etc.). For
ODtion 3 and 4, the use of traps is more costlv and hence, more
liable to affect sales (Options 3 and 4). These affects are
more pronounced under the fourth ODtion. Manufacturers would
definitely use traps on nearly all vehicles because the
sizeable reductions required could not even be approached with
non-trap technology.
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35
Table 10
Summarv of Sianificant Information for the LDP Control Ootions*
LDOV/LDCTT
Standard
Options
(o/mi)
1. 0.6/0.56
2. 0.3/0.35
3. 0.2/0.26***
4. 0.08/0.105
1995
Urban
Emissions
(m. tons)
58,600
(0%) f**l
43,400
(30%)
31,400
(46%)
16,600
(72%)
Average
LDDVs/LDDTs Lifetime Cost Sales
Requiring Per Vehicle
(1983 $)
Traps (%)
0
3-7
43
100
0
15-30
55-85
$220-270
Incremental
Urban Cost
Impact Effectiveness
($/m. ton)
(%)
0
0-1
1-5
7-15
2,500-3,500
8,600-
$11,000
$15,000-
17,000
* Values assume elimination of GM 5.7-liter diesel LDEV.
** Incremental percent reduction from total 1995 urban emissions for LDDs under the
relaxed scenario.
*** For comparison, Option 3 with 1.5/1.7 LDO NOx standards would be 1995 urban emissions
of: 1) 30,600 metric tons; 2) a 9 percent of LDDs requiring traps; 3) averaoe
lifetime costs of $20-$45 per vehicle; 4) a 1-3 percent impact on sales; and 5) an
urban cost effectiveness of $2,500-53,000 per metric ton.
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36
Given that further control is needed from LDDs and that
control down to the levels associated with the. second or
possibly third option appear to be quite feasible and
relatively inexpensive, control to this level appears
reasonable. However, given the low level of urban emissions
under the Option 3 standards and the sizeable costs (direct and
indirect) " associated with Option 4, it does not appear
reasonable to consider the full trap-based standards at * this
time for LDDs. However, in the lonq term, the Option 4
standards may be a reasonable control strategy, particularly if
LDD sales increase well beyond current projections. Also, the
issue of requiring traps on nearly all LDD models will be much
clearer in a few years, technologically and economically. The
question, then, is whether to implement the Option 2 or the
ODtion 3 LDD standards.
At issue technically is only the number of traps which
would be required, since at least one manufacturer is likely to
require traps under either option. Standards of 0.3/0.35 g/mi
for LDDVs and LDDTs, respectively, would probably eliminate the
need for traps for all but one manufacturer. Standards of
0.2/0.26 g/mi would likely require several manufacturers to
apply traps on at least some of their vehicles, unless major
engine modifications were employed. However, the majority of
the incremental urban emission reduction of Option 3, 12,000
metric tons per year in 1995, would not come from the use of
trap-oxidizers, but from non-trap techniques and, thus, should
be more cost effective than the sole use of traps. This
incremental- emission-, reduction is - near-ly 10 -percent of .19.95.
urban emissions under the relaxed scenario- and* is larger than
total 1995 urban emissions from MDVs and LHDVs combined. At
the same time, Option 3 would require the development of trap
technology by most manufacturers for application on only a
minority of their fleet. Thus, based on costs and emission
reductions, there are pros and cons to either ODtion 2 or
Option 3 and either option could be justified and implemented'
via rulemaking (though retention of the Ootion 3 standards
would of course not require any action on the part of the
Aqency) . However, there are a couple of additional factors
which should be considered.
There are two external factors that could affect the LDD
situation: the level of the LDD NOx standards and the level of
LDD sales. Considering the effect of NOx standards first, the
alternatives to the 1.0/1.2 g/mi standards discussed above are
.all numerically higher: 1.5/1.7 g/mi and 2.0/2.3 g/mi.
ChaDter 10 showed that the effect on particulate emissions of
movina from 1.0/1.2 g/mi to 1.5/1.7 g/mi was much larqer than
the second step to 2.0/2.3 g/mi. Thus, the discussion here
will emphasize the 1.5/1.7 g/mi option.
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Table 11 deDicts manufacturers' corporate emission
averages under the more relaxed 1.5/1.7 g/mi standards. As can
be seen, the great majority of both LDDV and LDDT manufacturers
are already well within the range of the Option 2 standards,
even without considerinq the application of additional non-trap
technology. This reduction in engine-out particulate emissions
across the board has the effect of reducino the number of traps
required at. any standard level. For Option 2, trap usage was
shown in Chapter in to drop from three to seven percent to
about one to three percent, thereby reducinq the cost and
improving the cost effectiveness of attaining the essentiallv
non-trap standards. At the _same ..time, the reduction in
enqin'e-out particulate emissions reduces the emission reduction
associated with olacinq a trap on any individual vehicle. This
causes the cost effectiveness of applvinq trao-oxidizers to
worsen bv rouahly a factor of two under Option 3 compared to
that under strinaent NOx standards. Thus, the desirability of
requiring traps significantly lessens. In general, stringent
non-trap standards should be implemented under the 1.5/1.7 g/mi
NOx option. This would mean particulate standards in the range
of 0.2 g/mi for LDDVs and n.3 a/mi for LDDTs.
Under 2.0/2.3 g/mi NOx standards, the same arguments are
simply carried a step further. Particulate levels are reduced
even further than those indicated in Table 11, making even
stringent ODtion 2 standards achievable by nearly every
manufacturer without any additional control, trap or non-trap.
Option 3 standards should be achievable bv nearly all
manufacturers with non-trap technoloay. At the same time, the
cost effectieveness of applying traos worsens even further.
Here aqain, the choice should be to imolement stringent
... .non - trap . s.taa&a-r.ds.Jn ' thisc,ase.,_£h_is., .wou-ld^mean- particulate.
" s t a nd a r-'ds'- 's'l iq'fft ly ;be low"' 0 2" g'/m-i'" and"'"'0T3 * g/m iV'*"r e spec t i ve ly". ** ¦-
Concerning the LDD sales effect, either of two
oossibilities could occur: 1) sales could be substantially
lower than projected by the best estimate, or 2) sales could be
substantially higher than projected by the best estimate. If
sales did not increase beyond their current levels, the overall
need for LDD control would lessen, but not be eliminated since
future LDD particulate emission inventories would continue to
grow beyond today's levels as shown in Chapter 10.
Furthermore, the available technoloav, cost oer. vehicle, and
cost .effectiveness of control would all remain roughly the
same, since they are unaffected by sales. Thus, overall, the
need for the additional control provided by Option 3 would
lessen.
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Table 11
Current Individual and Overall Corporate Average
Particulate Standard Levels for LDDVs and LDDTs Under Option 1
Presuming NOx Standards of 1.5 g/mi and 1.7 g/mi, Respectively
(orams per mile)
Manufacturer " LD'DV Manufacturer LDDT
General Motors .16*
Volk'swaaen ~ " .20
Nissan .26
Mercedes-Benz .42
Tsuzu .20
Audi .20
Peuaeot . .26
Volvo .29
Sales-Weighted .20
Industry wide
Average
Resultant Averaginq 0.42
Standard
Resultant Non- 0.43
Averaginq Standard
.29
General Motors " " .34
Isuzu * .25
Nissan .35
Mitsubishi .39
Toyota .19
Volkswagen .31
Toyo Kogvo .29
Sales-Weighted .33
Industrv-wide
Average
Resultant Averaginq 0.39
Standard
Resultant Non- 0.39
Averaqing Standard
Assumes .the,voluntary elimination, of...the. GM 5 ..7-liter LDDV.
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39
If sales are hiqher than projected, there is no doubt that
the Option 3 standards would be appropriate. As noted in
Chapter 2, under worst case sales, 1995 LDD emissions under the
Option 3 standards (base scenario) are still at least 40
percent above those shown in Table 11 for the Option 2
standards under best estimate sales indicating the need for the
additional control provided bv Option 3.
It is conceivable that the level of the LDD standards
could be directly tied to the level of LDD sales, if it were
decided to relax the existing Option 3 standards to those of
Option 2 at this time. Ideally, the sales or sales fraction-
limit would be .on a fleet-wide basis, since it is the
fleet-wide diesel penetration that affects emissions. However,
in this case, most manufacturers could find the level of the
standard changing due to the actions of one or two other
manufacturers who decided to invest heavily in diesels. While
the more stringent standard itself would be equitable, since it
would be the same for all manufacturers, the latter
manufacturer (s) would have more advance notice of the switch
since it is fully aware of its own future product plans.
There would also be little incentive to keep LDD sales low
since the level of the standard would only be indirectly
connected.
To mitigate this problem, sufficient leadtime would have
to be given between the time diesel sales exceeded the limit
and the time the revised standard was imposed. while the
effort and time needed to reimplement the Option 3 standards
would be avoided, this does not appear sufficient to offset the
: pr£b 1,'em ,tha jg'i"ven jtian uf ac&uze,i£,;wb'uI'd,' not rha.v*e direct.c on.tr;.q,
over" 'whether " or not it" had to meet the more stringent
particulate standard. Direct control would be critical to any
sales-based approach since it provides the incentive to keep
diesel sales low, as currently predicted by the manufacturers.
The other alternative would be to apply a diesel sales
limit to each manufacturer. This would eliminate the need for
leadtime since a manufacturer has control over its own sales.
A problem arises, however, in how to equitably set the sales
limit.
Limits based on absolute diesel sales are probably
unacceptable. The wide range of total sales volumes among
manufacturers would make this type of limit very inequitable.
A single diesel sales fraction limit is also not likely to
be acceptable, since LDD manufacturers currently sell between 1
and 70 percent diesels. A limit near the upper end of this
range would allow an enormous increase in fleet-wide diesel
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40
sales before most manufacturers would exceed their limit. A
limit near the lower end of this range would immediately impose
the more strinaent standards on a number of manufacturers and
issues of equity would quickly be raised. This very issue was
raised in 1979 when GM proposed an emissions averaging approach
that_ included both gasoline and diesel vehicles. This approach
resulted in increasinaly more stringent diesel particulate
standards as a manufacturer's diesel sales fraction increased
-and was immediatelv-challenged by Volkswagen and Mercedes-Benz,
manufacturers-with- high diesel sales fractions. -
A diesel sales fraction limit that varied between
manufacturers would appear to avoid this problem. However, the
question of how to set each manufacturer's limit arises. One
approach that appears to minimize inequities between
manufacturers would be to set each manufacturer's limit at its
maximum diesel sales fraction in recent years plus some margin
for moderate growth. Specifically, the model years 1978-82
should include all manufacturers peak diesel fractions and an
absolute cushion of 5 percent* should provide for both adeauate
diesel growth based on manufacturers* current statements and
adequate protection for the environment since LDD sales would
•be held to less than 10 percent of total light-duty sales. Any
manufacturer desiring to produce more diesels would have to
comply with the existing Option 3 standards, which would be
reasonable since manufacturers are currently requesting the
relaxation of these standards due to their low projected d.ie_sel
sales.
In summary, the pros and cons of retaining the current
Ootion 3 standards versus relaxing them to the Option 2
standards are roughlv balanced. tf Ootion 3 were chosen, then
no action would have to be taken by the Agency. If Option 2
were chosen, it may be appropriate to tie the relaxation to LDD
sales levels since manufacturers are currently basing their
arguments for relaxation on verv low LDD sales. In this case,
the best approach appears to be relax the LDD particulate
standards to those of Option 2 on a manufacturer-specific basis
(all should initially experience the relaxation) as long as
that manufacturer maintains its LDD sales fraction at or below
its historic (1978-82) peak plus 5.0 percent. Otherwise, it
appears appropriate to retain the current Option 3 standards,
as it appears inappropriate to grant a permanent relaxation on
such volatile grounds as projected LDD penetration.
For example, if manufacturers A and B have peak. LDD sales
fractions of 5 and 50 percent, respectively, their limits
would be 10 and 55 percent, respectively.
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41
. B. Heavy Duty
The environmental impacts summarized in Section II also
demonstrated the need to control HDD emissions beyond the 0.6
g/BHP-hr level. However, unlike the options for further
control for LDDs, all three levels of additional control for
HDDs could not be implemented in 1987. This occurs because:
1) engine modifications need to be extensively tested for
durability due to market demands, and 2) the application of
traps on HDDs is more difficult than that on LDDs. Thus, the
technology-forcing mandate of Section 202 (a) (3) (A) (iii) of the
Act notwithstanding, the only option truly viable for HDDs
prior to 1990 is the first option.
This first option, 0.6/6.0 g/BHP-hr for particulate and
NOx, respectively, is achievable as early as 1987. This level
is supported by at least one manufacturer's comments to the
proposed 1986 HDD particulate standard as well as by an
analysis of current HDD emission levels and projections of
minor control techniques applicable in this timeframe.
Given the 3-year standard revision cycle provided by the
CAA, the earliest year for a revised set of standards would be
1990. Here, Options 2, 3, or 4 are potentially available.
Given the demonstrated need to control HDD emissions and the
apparent cost effectiveness of the second option, control to at
least this level appears reasonable. The only questions
associated with Option 2 are the actual feasible levels of the
standards. Standards of 0.4 and 4.0 g/BHP-hr for particulate
and NOx, respectively, probably represent the maximum degree of
control achievable. bv . 1990... withoat traps..... T.h.us., promulgation.
of.., . these- standards-.:.- would •. represent -a "• commitment ; -:tO'
technology-forcinq by the Agency, with a potential need for a
delay at a later date. The alternative would be less stringent
non-trap standards, such as 0.5 and 5.0 g/BHP-hr, respectively,
which would provide little additional control over the 1987
standards.
A disadvangage of Option 2 is its effect on future HDD
trap development. As alluded to earlier, there is strong
evidence that significant development of a new control
technology only occurs in response to the promulgation of a
standard requiring its use. Thus, if a trap-based standard is
not proposed and promulgated for 1990, HDD trap development
will not progress and will appear no more implementable in 1990
than it does now.
On the other hand, the near-term promulgation of a
trap-based HDD standard for 1990 would also represent a firm
commitment by EPA to technology forcing. The problems facing
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42
HDD trap implementation are sufficiently significant at the
present time, as were those facing LDD trap implementation in
1979, that there is a fair Drobability that the standard may
not be feasible by 1990 and may reauire some delay at a later
date, and a continued ' commitment to its eventual
implementation.- Thus, compliance with this option may be no
more difficult than compliance with the second option, though
the technical issues involved would be very different (engine
related vs. trap related). However, the trap-based option
would, or course, provide more control than the non-trap
approach, so it has this advantage over Option 2.
With respect to the level of the trap-based standard, 0.25
g/BHP-hr would appear most appropriate. The requirement that
essentially all HDDs be equipped with high-efficiency
trap-oxidizers via a 0.1 a/BHP-hr standard would be difficult
to justify for 1990. The NOx standard would still be 4.0
g/BHP-hr as this level appears to represent the limit of
technology reaardless of whether traps are applied , for
particulate control.
The option of implementing an urban vehicle strateqv is
also available in the 1990 timeframe. There are still some
questions surrounding its cost, particularly for buses since
the economic viability of transit authorities could be
seriously weakened by any additional costs. However, these
costs could be mitigated by a Government subsidy for methanol
use by transit authorities which would ecruate* the cost of
me thanol.. and d iesel" fuel' on an, energy basis. "This would.be:
consistent with existinq aovernment support of the basic
availability of urban transit, only adding support for emission
control as well. Private fleets should be much better able to
absorb such costs, particularly since many such fleets will be
switching to diesels from gasoline engines. They will have the
option to stay with the gasoline engine, in addition to- the
options of paying for the additional cost of a trap-oxidizer
methanol engine; the methanol option only being viable for
those ooerators with central fuel depots.
Technical feasibility would not be an issue for those
vehicles for which methanol is a viable option, since methanol
engines should be easily producable. However, for those other
vehicles, traps would be required. Given that only Class VI
and lighter vehicles would be involved, trap feasibiliy should
be more easily demonstr a table than with respect to all HDDs,
since LDDT trap experience should be more applicable.
Overall, then, there appears to be only one option for
1987, a 0.6 g/BHP-hr particulate standard and a 6.0 g/BHP-hr
NOx standard. Three options appear viable for 1990. One,
-------
43
particulate and NOx standards of 0.4 and 4.0 g/BHP-hr,
respectively, for all HDDs. Two, standards of 0.25 and 4.0
g/BHP-hr, respectively, for all HDDs. Three, standards of 0.25
and 4.0 g/BHP-hr, respectively, for Class VI and lighter HDDs
and transit buses- (and possibly garbage trucks and cement
mixers) and standards of 0.4 and 4.0 g/BHP-hr, respectively,
for all other HDDs. with the third option, the emissions of
methanol engines would be included in the averaging process.
-------
44
References
1. "Regulatory Analysis of the Light-Duty Diesel
Particulate Regulations for 1982 and Later Model Year
Light-Duty Diesel Vehicles," U.S. EPA, Office of Mobile
Sources, Februarv 20, 1980.
2. "Draft Reaulatorv Analysis: Heavy-duty Diesel
Particulate Regulations," U.S. EPA, Office of Mobile Sources,
December 23, 1980.
3. "Health, Soiling, and Visibility Benefits of
Alternative Mobile Source Diesel Particulate Standards," Final
Report, EPA Contract No. 68-01-6596, Mathtech, Inc., Princeton,
NJ, December 1983.
-------
Part II
Supporting Technical
Analyses
-------
CHAPTER 1
TECHNOLOGY
T. Introduction
The major reductions in diesel particulate emissions
available from engine modifications have already been achieved,
with the possible exception of electronic control of the fuel
injection system. Further major reductions will need to be
accomplished through the use of trap-oxidizer systems.
Under the current light-duty diesel vehicle (LDDV) and
liqht-duty diesel truck (LDDT) particulate standards of 0.6
gram per mile (g/mi), no traps are necessary. Since heavy-duty
diesels (HDDs) are not currently subject to. a particulate
standard, traps are not found on current HDDs, either. . However,,
the more stringent particulate standards of the base scenario
will require traps on many diesels. This chapter investigates
each manufacturer's need for trap-oxidizer systems under the
LDDV, LDDT, and HDD particulate standards of the base scenario,
as well as determining the non-trap particulate emission levels
which would occur under less stringent particulate standards of
the relaxed (non-trap) scenario.
This chapter is divided into three sections, each in turn
addressing LDDVs, LDDTs and HDDs. The section addressing LDDVs
is the most detailed, as the methodology for all three sections
is therein described. The latter sections only reference this
methodology.
The LDDV section itself consists of five parts. The first
simplv describes the source of the engine-out LDDV particulate
levels used in the analysis. The second addresses the
NOx/particulate trade-off issue and establishes NOx/particulate
relationshios to ...-be.---us.ed- - iru. ..adjustinc.. -; par t-iculate......emission
levels " to vary ing • NOx • levels. ',:'-Wh"il"e these relationships • wi-i.l..
have onlv a limited use here in addressing the base
scenario--most LDDVs are at NOx levels near those appropriate
to comply with the base scenario's 1.5 q/mi NOx standard--they
will be of siqnificant use in addressing the sensitivity of the
results of this chapter to varying LDDV and LDDT NOx standards
(see Chapter 11). The third part of the LDDV section estimates
the equivalent "standard" levels that each LDDV engine
configuration could meet without traps and. the fourth part
converts these engine configuration levels into corporate
average non-trap standards achievable by each manufacturer (the
relaxed scenario). The fifth and final part will then
determine the percentage of LDDVs which will require traps
under the base scenario (0.2 g/mi particulate and 1.5 g/mi NOx
standards with corporate averaging).
-------
1-2
II. Light-Duty Diesel Vehicles
A. Current Levels of NOx and Particulate Emissions
The most convenient and accurate source of current LDDV
engine-out particulate levels is the new-vehicle certification
program. The first model year in which LDDV manufacturers had
to certify to the current 0.6 gram per mile (g/mi) particulate
standard was 1982. However, some manufacturers chose to test
for particulates in the 1981 model yea" and then carryover the
results for the 1982 model year ther-- spreading out the new
emissions testing program over two y- ;. Thus, certification
test results for LDDV particulate are primarily available for
the last two years (ie., the 1982 and 1983 model years), with
some data being available from the 1981 model year as well.
All of the 1983 model year LDDV engine families were
subdivided into configurations on the basis of transmission
type and inertia weight class. The available 1981-83 1 NOx and
particulate test data were then obtained for each of these
configurations. These data included emission tests plus fuel
economy tests during which emissions were also measured. Both
manufacturer tests and EPA tests were included.
A review of the test results of configurations for which
testing had been done for both the 1982 and 1983 model years
did not show a clear pattern of change from one year to the
next, although there was a modest trend for both NOx and
particulate to improve with the more recent data. Therefore,
it was concluded that only the most recent (1983) test results
should be used here when available. However, in the cases
where 1983 engine configurations were ..car r ied^. over from 1982
and "no " 19-83 - data were" ' available", the 1982 "model year
certification test results were used.
These most recent test results for each configuration were
then examined and outliers excluded before determinina the mean
for each configuration. In general, outliers were test results
greater than 140 percent or less than 60 percent of the mean of-
the rest of the test results for that configuration. This
range may have been somewhat greater or smaller depending on
the observed SDread and total number of tests. The remaining
test results for each configuration were averaged and the
resultant means used as the current level of NOx and
particulate emissions for each configuration. These
engine-configuration means are shown in Table 1-1.
B. The NOx/Particulate Tradeoff
Having established the current NOx and particulate
emission levels, an estimate of how the particulate emission
level would change if the NOx emission level were increased or
decreased was made. Such an analysis was primarily necessary
-------
Table 1-1
Actual, Certification LDDV
Particulate arid NOx Emission Levels
Manufacturer
General Motors
Volkswaaen
Engine
Inertia Weight
Displacement
Particulate
Family
Trans.
Class (lb)
(liters)
LMT (a/mi)
290
MS
2,500
1.8
.17
290
L3 '
2,500
1.8
-.13
ZK7
L3
3,000
4.3
.22
2K7
L3
3,500
4.3
.25
ZT8
L3
3,500
4.3
.21
2T7
L3
4,000
5.7
.32
ZT7
L3
4,500
5.7
.37
ZT7
L4
4,000
5.7
.37
ZT7
L4
4,500
5.7
.40
MO
M4
2,250
1.6
.16
AAO
MS
2,250
1.6
.19
AAO
A3
2,250
1.6
.18
JAO
MS
2,500
1.6
.19
JAO
A3
2,500
1.6
.17
AZ8
M5
2,250
1.6
.22
AZ8
M5
2,500
1.6
.20
AZ8
A3
2,500
1.6
.29
RA5
S4
2,250
1.6
.18
BZX
A3
2,750
1.6
.18
BZX
MS
2,750
1.6
.22
NOx
LMT (o/mi)
1.11
1.01
1.04
1.10
1.23
1.21
1.14
1.11
1.18
.90
1.02
1.01
1.02
1.10
1.12
1.10
1.14
1.02
1.22
1.19
-------
Table 1-1 (cont'd)
Actual, Certification LDOV
Particulate and ?Ox Emission Levels
Engine
Inertia Weight .
Displacement
Particulate
NOx
Manufacturer
Familv
Trans.
Class (lb)
(liters)
LMT (a/mi)
LMT (a/mi)
Nissan
AF8
M4
2,250
1.7
;17
.82
AF8
MS
2,250
1.7
.20
.94
AF8
MS
2,500
1.7
.23
1.00
AF8
A3
2,250 .
1.7
.24
.89
AF8
A3
2,500
1.7
.23
.92
APO
MS
3,500
2.8
.22
1.16
AFO
L4
3,500
2.8
.24
1.32
Mercedes-Benz
501
M4
3,500
2.4
.42
1.11
501
A4
3,500
2.4
.38
1.15
508
A4
4,000
3.0
.43
1.26
Isuzu
CD7
M.4
2,500
1.8
.19
1.09
CD7
ms
2,500
1.8
.17
1.21
CD7
MS
2,750
1.8
.18
1.17
CD7
A3
2,750
1.8
.16
1.29
Audi
BZ7
MS
2,750
1.6
.22
1.19
3Z7
A3
2,750
1.6
.17
1.21
CZ3
A3
3,000
2.0
.19
1.23
BAX
MS
2,500
1. <5
.21
1.08
Peugeot
AAl
MS
3,500
2.3
.28
1.04
AAl
A3
3,500
2.3
.30
1.01
BA3 '
M4
3,500
2.3
.32
.87
BA3
A3
3,500
2.3
.40
.98
Volvo
AY2
M4
3,500
2.4
.29
1.37
AY2
A3
3,500
2.4
.27
1.31
TBO
MS
3,500
2.4
.29
1.17
TBO
A3
' 3,500
2.4
.23
' 1.19
-------
1-5
so that the particulate emission level of each configuration
under the various NOx standards being considered in the
sensitivity analysis could be estimated. However, it is also
useful here, since many engine configurations are emitting NOx
well below the levels required by a 1.5 g/mi standard and some
adjustment of their particulate levels would appear appropriate.
Assumina that only injection timing retard or EGR is used,
the general shape of a NOx/particulate tradeoff curve is known
to be (NOx emissions in the x dimension and particulate
emissions in the y dimension): 1) negative in slope at all
points, 2) steeply sloped at low NOx levels, and 3) gently
sloped to flat at high NOx levels. Furthermore, it is
Generally known that the curve"shifts outward (ie., upwards and
to the right) with increasing engine displacement. Fiaure 1-1
shows qeneralized NOx/particulate tradeoff curves and
illustrates this shifting effect of engine displacement.
Ideally, the specific tradeoff curve would be known for each
engine family/confiauration. However, such curves are not
available. Therefore, an approximate method was developed for
predicting particulate emission levels from known NOx levels.
First, in order to account for the shifting of the curve
that occurs with changes in enaine displacement, the 1983 model
year engine families were divided into the following three
groups: small engines (1.6 to 1.8 liters), medium engines (2.0
to 2.8 liters) and large engines (3.0 to 5.7 liters)." The NOx
and particulate emission levels were then plotted for each
configuration within each engine size group.
The NOx emission levels for the small engine group ranged
(£ rom 0 . 80c.;toT 1...29.. jg/m i ..-.-.The. ..d i,s..tr:.ibu,t ion..: o.f ,po in.ts,,appear.ed„ „t.o..
,!have . a sl ightly ^..ne-ga.tilve-.-,slope-•¦w-tvioh- vr-egress ion of the data-- •
confirmed. The emission levels of one configuration (VW,
engine family AZ8, A3 transmission, 2500 lbs.) were excluded
from the regression because the NOx/particulate combination was
well outside the range of all of the other values includina
other values for that same engine family. The slope of the
regression line was -0.033. This slope is quite small, as will-
be seen later when compared to those for the larger engines,
and is qenerally in line with what would be expected for small
enaines.m Therefore, it was used to predict changes in
particulate emission levels resulting from changes in NOx
emission levels below an absolute NOx level of 1.35 a/mi. It
was assumed that no further reduction in particulate would
occur for NOx emission levels greater than 1.35 g/mi (i.e., the
slope was considered to be zero).[l]
A NOx emission level of 1.35 g/mi was chosen as the
reference point to change slopes for the small engine group
(and the other two groups) for two reasons. First, the great
majority of current LDDVs have NOx emissions less than 1.35
g/mi. Since the slopes obtained by the regression of the data
-------
1-6
Figure 1-1
Generalized Shape of NOx/?articuIata•Tradeoff
Curves Illustrating the Shifting Effect; of Engine Distlacnen*
'A
y
¦¦3
y
arce
r.gmes
NCx
-------
1-7
are most appropriate within the distribution of data, it was
decided to limit the applicability of the regressions to this
level. Second, 1.35 g/mi is approximately the engineering
objective (or low mileage target (LMT)) for the NOx standard of
the base scenario (1.5 g/mi) . (The NOx standard of 1.5 g/mi
minus a 10 percent safety margin and divided by a deterioration
factor (DF) of 1.000 (which is typical for diesel NOx
emissions) yields a LMT of 1.35 g/mi.)
The plot of the emission levels for the medium engine
group, whose NOx values ranged from 0.87 to 1.37 g/mi, appeared
to have a-greater negative slope than the small engine aroup.
Regression of the data confirmed this, showing .a. slope of
-0.201. As this slope appeared reasonable for engines of this
size, based on the limited information available on current
NOx/particulate tradeoff curves[1] and the fact it was larger
than the slope for the small enqines, this slope was used to
predict the change in particulate emission levels for chanqes
in NOx emission levels below 1.35 g/mi NOx. Again, two
configurations' emission levels (M-B, 2.4L, both transmissions)
were not used in the regression because they definitely
appeared to be outliers. The slope of the tradeoff curve for
NOx emission levels greater than 1.35 g/mi was somewhat
arbitrarily reduced by one-half to -0.100, since it is known
that the curve becomes flatter at higher. MOx levels, but by an
unknown magnitude.
For the large engines, the slope of the tradeoff curve for
NOx values below 1.35 g/mi was not based on a regression of the
data, but was simply estimated to be -0 . 400 based on known
tradeoff curves for large, albeit older, engines.[1] This was
..necessary because there were only 9 data points for the large
.engines " and ihp?' 'cbrrelation " existed-. -- The- - slope-. forr.N.Ox. .values,
greater than 1.35 g/mi" was also ""estimated -u'sing engineering-
judgment and was set at -0.100. At first a slope of -0.200 was
estimated, based on the judgment that this slope should be
steeper than that for the medium-size engines. However, this
produced some unrealistically low particulate values at the
higher NOx values being examined in the NOx sensitivity
analysis, so -0.100 was chosen instead.
C. Engine Configuration's Low-Mileaae Targets and
Standard Levels
Usina the slopes of the tradeoff curves determined above
and the data in Table 1-1, the particulate low-mileage target
(LMT) at 1.35 a/mi NOx was calculated for each configuration.
The particulate standard level for each configuration was then
calculated for these particulate LMT s. This was done by
multiplying the particulate LMT by the appropriate 50,0.00 mile
deterioration factor (DF) and the appropriate safety margin.
Both factors are explained below.
-------
1-8
The particulate DF used for each configuration was the
certification DF for the 1983 model year except in three
instances. The three exceptions were enaine families* with DFs
much greater than the other 18 engine families. Fifteen of the
21 total engine families had particulate DFs less then 1.10.
Another three engine families had particulate DFs between 1.10
and 1.15. The last three engine families had particulate DFs
greater than 1.24. It was concluded that the manufacturers of
these last three engine families could lower the DFs to at
least the 1.15 level if a more stringent particulate standard
required them to do so. Therefore, for the purposes of this
study, a DF -of 1.15 was assumed for -each of those three engine
families.
The safety marains necessary for calculating the
particulate standard levels from each particulate LMT were
determined using the methodology developed for past FPA
rulemakings.[2] That methodology requires a coefficient of
variation (COV) for production-line vehicles and the number of
prototype vehicles tested before a manufacturer fixes its
design. Results from EPA's Selective Enforcement Audit (SEA)
testing program[3] indicate that the LDDV particulate COV is
slightly less than 0.13. Also, the number of prototype
vehicles to be built and tested was presumed to equal the
maximum considered in the methodology (seven), since the engine
technology exists today and manufacturers will have more than
sufficient data upon which to base their LMTs. Thus, the
safety margin as interpolated from the table[2] would be seven
percent. However, since available SEA test data on LDDVs is
limited and the particulate COV may increase somewhat with more
strinaent MOx and/or particulate standards, a somewhat larger
safety" mVrqTn^b'f ''.lO'perceht. was "use'd.-for "this .study ij ~ ***•' ' ~ ;
The particulate standards achievable by each configuration
are shown in Table 1-2. An industry-wide, non-averaging,
non-trap, non-technoloay forcing particulate standard can be
determined by simply identifying the configuration with the
highest particulate standard listed in Table 1-2. Thus,, for
the NOx standard of 1.5 g/mi, such a particulate standard would
be 0.43 g/mi (M-B, 3.0L engine).
It should be noted that this highest emitting
configuration, as well as the next three highest emitting
configurations, seem to be technology outliers. Three out of
four of these configurations are Mercedes-Benz (M-B) vehicles.
When the emissions of these M-B vehicles are compared to those
of other similarly sized vehicles, one finds that the M-B
Engine families, rather than configurations, are
considered here because DFs are only determined on an
engine family basis and are applied to all configurations
within that engine family.
-------
1-9
Table 1-2
Achievable Non-Trap, LDDV Particulate
Standards Under the 1.5 q/mi NOx Standard
Part. Std.
Assuming a
Engine Inertia Weight Displacement. 1.5 g/mi
Manufacturer Family Transmission Class (lb) (liters) NOx Std. (g/mi)
General Motors Z90 M5 2,500 1.8" .20
Z90 L3 2,500 1.8 .15
ZK7 - * L3 - 3,000 4.3 .12
ZK7 L3 3,500 4.3 .17
ZT8 L3 3,500 4.3 .19
ZT7" ' L3 - 4,000 ' 5.7 .33
ZT7 L3 4,500 5.7 .36
ZT7 L4 4,000 5.7 .35
ZT7 LA 4,500 5.7 .42
Volkswagen AAO M4 2,250 1.6 .17
AAO M5 2,250 1.6 .21
AAO A3 2,250 1.6 .20
JAO M5 2,500 1.6 .21
JAO A3 2,500 1.6 .19
AZ8 M5 2,250 1.6 .27
AZ8 .M5 2,500 1.6 .24
AZ8 A3 2,500 1.6 .26
RA5 S4 2,250 1.6 .20
BZX A3 2,750 1.6 .20
BZX M5 2,750 1.6 .24
-------
1-10
Table 1-2 (cont'd)
Achievable Non-Trap, LDE*/ Particulate
Standards Under the 1.5 g/mi NOx Standard
Part. Std.
Assuming a
Engine Inertia weight Displacement 1.5 g/mi
Manufacturer
Family
Transmission
Class (lb)
(liters)
NOx Std. (g/mi)
Nissan
AF8
M4
2,250
1.7
.20
• AF8
M5 -
2,250
1.7
.24
AF8
M5
2,500
1.7
.28
AF8
A3
2,250
1.7
.29
AF8
A3
2,500
1.7
.27
AFO
M5
3,500
2.8
.22
AFD
L4
3,500
2.8
.28
Mercedes-Benz
501
M4
3,500
2.4
.41
501
A4
3,500
2.4
.37
508
A4
4,000
3.0
.43
Isuzu
CD7
M4
2,500
1.8
.22
CD7
M5
2,500
1.8
.20
CD7
M5
2,750
1.8
.21
CD7
A3
2,750
1.8
.19
Audi
BZ7
M5
2,750
1.6
.24
BZ7
A3
2,750
1.6
.19
CZ3
A3
3,000
2.0
.19
BAX
M5
2,500
1.6
.25
Peugeot
AA1
MS
3,500
2.3
.24
AAl
A3
3,500
2.3
.26
SA3
M4
3,500
2.3
.25
BA3
A3
3,500
2.3
.36
Volvo
AY2
M4
3,500
2.4
.36
AY2
A3
3,500
2.4
.32
330
r - -M5~'-^"' ••
2.4
~ • - .32.
" ' TBO
" A3 '
" ' 3,500
• .25 " *
-------
1-11
vehicles emit significantly more particulate. Thus, it appears
that M-B- has not yet implemented the kinds of combustion
chamber and injection modifications that have been made by
others (e.g., General Motors). Presumedly, M-B could do this
if it became necessary. The fourth configuration is a General
Motors vehicle powered by their 5.7 L engine (L4 transmission,
4500 lbs.). It has been rumored that this engine will be
eliminated- sometime in the next few years, primarily due to
market considerations, as well as to the fact that this is
their highest emitting engine for both NOx and . .particulate. If
these four configurations were excluded from consideration
here, the non-averaging, non-technology forcing particulate
standard could ..be. 0.36 a/mi, 15 percent., .lower than the 0.43
a/mi level mentioned above.
D. Non-Trap "Averaging" Standards
The previous discussion presented the methodology used to
estimate particulate LMTs and standard levels for each
configuration under a NOx standard of 1,5 g/mi. From those
results an industry-wide, non-averaging, non-trap,
non-technoloay forcing particulate standard could be selected.
That standard was based on the assumption that every LDDV would
need to be at or below the standard (i.e., non-averagina) . In
this situation, most vehicles could increase their particulate
emissions up to the level of the worst-case vehicle and still
be in compliance. While we would not expect such a situation
to occur to this extreme, it is possible that NOx control and
fuel economy incentives could lead to increased particulate
emissions if the particulate standard allowed it.
One way to significantly increase the probability that
-in d us tr-.v - w i d e>- a-r-t-i c-u-1 a t e- ••emi-ss-i- on s—wo u~l d n o ti- ncr ea &e«- -beyon d-.™*,. .
"present" -'TeVeis:u' artd;': v:e't;- ''•still'" --sSt- non-'technology -¦ "f o'r'Ci-n
standard would be to implement a corporate average standard
(see the introduction to the study for an explanation of
emissions averagina) . Under this approach the non-trap,
non-technology forcing standard would be numerically lower than
that determined in the previous discussion since each
manufacturer could "average" its high emitters with its low
emitters. Because of this, it becomes more difficult for a
manufacturer to increase the emissions of its low emitters
since these emissions are factored into its corporate average
emission level and are no longer irrelevent.- Thus, while
averaging has been considered in the past only for trap-based
particulate standards, it also has a benefit for non-trap
standards.
Table 1-3 shows the currently achievable non-trap,
non-technoloay forcing particulate standard for each
manufacturer under averaging. These standards were calculated
by sales weighting the achievable particulate standards for
each manufacturer's LDDV configurations listed in Table 1-2.
Sales for each configuration were obtained from the
-------
1-12
Table 1-3
Achievable Non-Trap Particulate
Standards (under "averaging")
Assuming
a 1.5 g/mi
NOx Standard
Manufacturer (g/mi)
General Motors .29*
Volkswagen .20
Nissan .26
Mercedes-Benz .42
Isuzu .20
Audi .20
Peugeot .26
Volvo .29
This level becomes 0.16 g/mi if GM's 5.7-liter engine is
d iscontinnued and its sales are replaced by their
4.3-liter engine.
-------
1-13
manufacturers' 1983 estimated Federal sales required by the
fuel economy program known as Corporate Average Fuel Economy
(CAFE).* If the worst-case manufacturer's (i.e.,
Mercedes-Benz) particulate averaging standard level became the
averaging standard for the industry, then as Table 1-3 shows,
the particulate averaging standard would be 0.42 a/mi. This
level is not significantly lower than the 0.43 g/mi
non-averaging standard of the previous . section due to what
appears to be excessively high emission levels of the
worst-case... manufacturer's engines. If this worst-case
manufacturer is treated as a technology outlier, then the
corporate average for General Motors and Volvo would set the
indus.try.-wid_e.r__. particulate, averaging standard at 0.29 g/mi.
This .level is 33 percent lower than the non-averaging standarcf'
of the orevious section (0.43 g/mi). A non-trap,"
non-technology forcing, particulate averaging standard of 0.29
g/mi would moderate the risk that manufacturers of small LDDVs,
which are low particulate emitters, might substantially
increase particulate emissions from these vehicles.
It is interesting to note what would happen to GM's
corporate average particulate level if it discontinued
production of its 5.7-liter engine. This could happen if the
long-range trend towards increased fuel economy eliminated the
"big" cars of today whereupon the need for the 5.7-liter engine
would also be eliminated. Assuming that the vehicles which
would have had the 5.7-liter engine received instead GM's
4.3-liter engine, GM's average particulate standard level would
drop from 0.29 g/mi as shown in Table 1-3 to 0.16 g/mi.
Furthermore, since GM's estimated sales comprise about 60
percent of the total LDDV estimated sales, lowering GM's
averaoe particulate standard level by this 45 percent would
.¦lowec«total vLDQV paxti,Gu!la,te^emiss,ip,n.s... substantially. „.. However..,
•the' "non- trap, non- tec-h-no-logy- ¦'• - forcing-, ....av.er-ag fng " particulate
standard based on the second highest emitter would remain at
0.29 g/mi (Volvo).
E. Determination of the Percent of Trap-Equipped
Veh ides' ~
Thus far, this analysis has been concerned with only those
particulate standards achievable without the use of
trap-oxidizer systems. It will now consider the use of traps
as a particulate control strategy. Here the focus of the
analysis will differ' from that of the previous section.
Instead of determining achievable particulate standards under
These projections are confidential and are not presented
here. The presentation of the resultant corporate
emission average does not divulge the pertinent
information contained in the projections (i.e., absolute
sales) .
-------
1-14
various scenarios which assume some percent usage of traps (in
the previous case, zero), this discussion will assume a
particulate standard of 0.20 g/mi (the base scenario) and then
determine the percentage of the LDDV fleet requiring traps in
order to achieve this standard. Emissions averaging will be
assumed to apply as the Agency expects to soon finalize a
particulate averaging program in conjunction with the 0.2 g/mi
standard (proposed in 46 FR 62608).
Two types of traps were considered for compliance with the
0.20 g/mi particulate standard. One is the wire mesh type and
the other is the ceramic type. EPA's report[4] on the
feasibility of trap oxidizers indicated that both types appear
to have good durability characteristics. The ceramic type of
trap was tested by Southwest Research Institute for EPA[5] and
the wire mesh type was tested at this same facility for
Johnson-Matthey, Inc. [6] These testing programs indicated that
the deterioration for both types of traps was negligible and,
therefore, a DF of 1.00 was used here. The EPA[41 report
discusses each of the two traps in detail and concludes that
the efficiency of the ceramic trap is about 70-90 percent while
the efficiency of the wire mesh trap is about 50-80 percent.
As the durability test of the ceramic trap referred to above
showed an 85 percent efficiency, that figure will be used
here. For the wire mesh trap, 65 percent will be used as a
reasonable mean efficiency for a typical trap. This analysis
will use these percent efficiencies to determine the tail pipe
emission levels from engine-out emission levels. (For
simplicity, mixing use of both trap types was avoided.)
The methodology used to calculate the percentage of
.tr,ap«equ.-ippejdt--.rv_e-h.-ieles ,-,-fo.r. ..each_,,typ.e., ,q£ t r.ap-, an,d... manu,f,ac,.turer„;
is straightforward. ;~Fi-rst, ^-"each~"'-con-f-igurati-on-'-s - estimated
sales was multiplied by that configuration's non-trap standard
level taken from Table 1-2. These results were then summed to
obtain the total number of vehicle-grams per mile (veh-g/mi)
from which each manufacturer would begin its control efforts.
Next, each manufacturer's total estimated sales were multiplied
by 0.20 g/mi to give the total veh-g/mi that the manufacturer
would be allowed under each particulate averaging standard.
The difference between the two figures is the amount of control
each manufacturer needs to achieve. It was assumed that a
manufacturer would put traps on its highest emitters first
because the g/mi reduction achieved is highest for those
veh icles.
To determine the number of veh-g/mi saved by putting a
trap on a given configuration, that configuration's particulate
LMT was first multiplied by one minus the trap efficiency and
then multiplied by that configuration's particulate DF. This
result was then transformed into a new particulate standard
level by adding a safety margin of 10 percent or 0.02 g/mi,
whichever was greatest, because 0.02 g/mi was considered the
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1-15
minimum acceptable safety margin. The new particulate standard
level was then multiplied by the estimated sales for that
configuration to give the new total veh-g/mi emitted. The
difference between the total veh^g/mi without traps and the
total veh-g/mi with traps was counted as controlled veh-g/mi.
Calculations were made for each configuration ' until the
controlled veh-g/mi equalled or exceeded the amount of veh-a/mi
that the manufacturer needed to control in order to meet the
0.2 a/mi particulate standard. For the most part, only enouah
traps -were assumed. .installed to just meet . the standard.
However, in a few instances where the percentage of traps on a
given configuration approached 80 percent it was assumed that
the whole configuration would-be equipped with traps.
The results of these calculations are shown in Table 1-4.
Assumina ceramic traps, 22 percent of all LDDVs would require
traps to comply with the 0.20 g/mi standard. Assuming wire
mesh traps, this figure increases to 30 percent.
Ill. Light-Duty Diesel Trucks
The methodology used to estimate the non-trap,
non-technology forcing, particulate standards for each LDDT
configuration was the same as that used for LDDVs. The current
particulate emission test levels for small LDDTs (i.e., engine
displacements from 1.6 to 2.3 liters), which were obtained from
certification test results, were used to calculate the
oarticulate standard levels shown in ^able 1-5. The NOx
emission levels of the majority of these configurations were
between 1.35 and 1.7 g/mi. Since the NOx/particulate tradeoff
curve for small LDDV engines was flat in this region, no
adjustment was made to the small LDDT certification values in
rder iving •• th-e "-pa-r t iculate LMTs;.'For •••¦the. / f ull-size-^ -LDDT-S • ("iv-e-i-y
enai'ne displacements of' 6.2 liters) the current particulate
emission test levels were adjusted to their equivalent at 2.05
a/mi NOx using the same NOx/particulate tradeoff curve (slope
of -0.100) as that used for large LDDVs. (A LDDT NOx level of
2.05 g/mi under a 2.3 g/mi NOx standard is equivalent to the
1.35 q/mi NOx level for LDDVs. Also, the -0.1 slope curve was
the only one needed since the certification NOx emission levels
of the full-size LDDTs were all above 1.5 g/mi.) As shown in
Table 1-5, the industry-wide, non-trap, non-technology forcing
particulate standard without averaging would be 0.40 g/mi.
Table 1-6 presents each LDDT manufacturer's non-trap,
non-technology forcina, particulate standard under the
averaqinq concept. These levels were calculated using the same
methodology as was previously described for LDDVs. The highest
average particulate level is for Mitsubishi at 0.39 g/mi. Note
that this level is well above that for GM (0.28 g/mi), which
only produces full-size LDDTs. Thus, if Mitsubishi were
considered controlling, there is very little difference between
the non-averaging and the averaging non-trap standard for LDDTs.
-------
1-16
Table 1-4
Per.antage of LDDV Sales Requirinq Traps Under Various
Particulate Standards (assumes "averaging")
1.5 a/mi NOx Standard
0.20 g/mi 0.20 g/mi
Particulate Particulate-
Standard with Standard with
Manufacturer Ceramic Trap wire Mesh Trap
General Motors
26.8
36.2
Volkswagen
0
0
Nissan-
2 5.6
3 3.4
Mercedes-Benz
5 5.5-
79.6
Isuzu •
0
0
Audi
2.2
2.9
Peugeot
30.3
39.5
Volvo
34.4
44.2
Industry-wide
22.3
30.2
Sales-Weighted
Percentage
-------
1-17
Table 1-5
Achievable Non-Trap, LDDT Particulate
Standards Under the 2.3 g/mi NOx Standard
Part. Std.
Assuming a
Engine Inertia Weight Displacement 2.3 g/mi
Manufacturer Family Transmission Class (lbs.) (liters) • NOx Std. (g/mi)
Small LDCTTs:
Ford
AG5
M4
3,000
2.2
.29
Isuzu
CD3
M4
2,750
2.2
.28
,,
¦ M4
3,000
2.2
.26
M5
3,000 ¦
2.2 -
.25
Nissan
AF9
MS
3,000
2.2
.35
Mitsubishi
FDO
MS
3,000
2.3
.39
MS
3,500
2.3
.38
Toyota
EB8
MS
3,000
2.2
.17
FF9
M5
3,000
2.2
.25
Volkswagen
PA2
M4
2,250
1.6
.26
M5
2,250
1.6
.38
VA9
M5
3,500
1.6
.27
MS
4,000
1.6
.33
Toyo Kogyo
KK9
MS
3,000
2.2
.29
Jll-Size LDITTs:
•General Motors
•Z-40 -
M4
-4,500
. . .. ..,..32.
^ -1*.
- LA ¦
-4,500
•' 6.2 •
.35'
m
5,000
6.2
.26
LA .
5,000
6.2
.28
M4
5,500
6.2
.40
L4
5,500
6.2
.26
L4
6,000
6.2
.36
-------
1-18
Table 1-6
Achievable Non-Trap Particulate
Standards Under "Averaging"
Assuming a 2.3
Manufacturer g/mi NOx Standard
Small LDDTs:
Ford .29
Isuzu .25
Nissan .35
Mitsubishi .39
Toyota .19
Volkswagen .31
Toyo Kogyo .29
Full-size LDDTs:
General Motors .28
-------
1-19
As in the LDDV case, the percentage of LDDTs requiring
trap-oxidizer systems under the base scenario (0.26 g/mi
particulate standard) was determined. The methodology used to
determine this percentage was the same as for LDDVs except that
small and full-size LDDTs were considered separately. This was
done because the ratio of sales of small to fuli-size LDDT
sales is expected to change significantly by the mid-to-late
1980s. A study[7] by Jack Faucett Associates (JFA) projects
that in 1987, 86. 5 percent of all new LDDT sales will be
full-size while only 13.5 percent will be small.
Manufacturers' LDDT sales estimates for the 1983 model year
indicate that currently full-size LDDTs represent about 55
percent of all LDDT sales. Thus, a substantial change is
expected to occur over the next several years. Therefore, the
percent of traps required by each LDDT-size group was weighted
according to the findings by JFA and then combined into a
sinale LDDT percentaqe.
Table 1-7 presents the percentage of sales" for each
manufacturer that would require ceramic traps under the 0.26
a/mi particulate standard. For simplicity these calculations
were not done for the wire mesh trap, as the effect of using
wire mesh traps instead of ceramic traps was estimated in
Section II.E. for LDDVs and, given present data, the ceramic
trap appears to have advantaaes over the the wire mesh trap in
terms of cost and trapping efficiency. If the percentages of
wire mesh traps required per manufacturer were desired, they
could be easily approximated by applying the ratio of the
percent of LDDVs which would require wire mesh traps to the
percent of LDDVs which would require ceramic traps (see Section
11. E .)
From Table 1-7, the indus try-widie oercentage of "sales that
would require ceramic traps under the base scenario is
estimated to be 7.6 percent.
IV. Heavy-Duty Diesels
A. Current Emission Level and Non-Trap Standards
Currently there is no particulate standard for heavv-dutv
diesel engines (HDDEs). Therefore, there are no certification
test data from which to determine the current levels of HDD
particulate emissions. However, there has been a substantial
amount of HDD particulate testing over EPA's new transient
cycle by both EPA and the industry. Table 1-8 contains
particulate and NOx emission data from manufacturers'
production and development tests,[81 the EMA/EPA HDD
"round-robin" testing program,[91 and EPA's original diesel
transient baseline(lO) (for those engines for which more recent
data are not available) . Althouqh data are not available for
every HDD engine family, a large majority of sales is
represented. Sales weighting the data in Table 1-8 indicated
-------
1-20
Table 1-7
Percentage of LDDT Sales Requiring Traps Under Various
• Particulate Standards (assumes "averaging")
0.2 6 g/mi
Part. Std. with
Ceramic Trap .
Small LDDTs:
Ford 12.3
Isuzu 0.0
Nissan 31.9
Mitsubishi 40.1
Toyota 0.0
Volkswagen 15.4
Tovo Kogvo 11.5
Full-size LDTs:
General Motors 6.9
Industry-wide 7.6
Sales-Weighted
Percentage •
-------
1-21
Table 1-8
Low-Mileage, Transient Emissions
From Current Heavv-Dutv Diesel Encrines
Manufacturer/
Engine
Caterpillar
3208 DINA
3208 DIT
3406 DITA
3 40 6 PCTA
3306 DITA
3 3 06 PCTA
Cummins
NTC 290
NTC 3 50
NTC 350 (3ig Cam)
NTCC 240
NTCC 400
NH 250
VTB-903
Da imler-Benz
OM 344A
OM 362A
Detroit Diesel
8V-71N
8V-71TA
6V-92TA
.-9V-92TA ¦
- '-8.2-T
Part iculate
(g/BHP-hr)
0.65
0.59
0.52-0.71 /
°-37 -sib
0.73 V
0. 50
NOx
.(q/BHP-hr )
0
0,
0
0,
0
0,
59
58-0.70
40
77
85
52-0
83
0.67
0.81
0.45
0.79
0.35-0.43
0.55-0.67
' 0:'. 4 6' "V.
0.4 3 ' • •
*
.X,. .«?.
"b ^
i
10
7
5
9
4
8
0
9-8
4
0
8
8.3
7.2-9
6.8
4.8
5.3
6.8-6,
5.2
5.1
6.7
5 . 7
6.7-7.6
5.8
7.8
5;0- 5'. 9"
International Harvester
DT-466B
DTI-466B
0.53
0.67
0.31-0.36
5.7
4.2
5.6-5.7
Mack
ETA2-676
ETSX-67 6
ETS2-676
0. 58
0.63-0.69
0.59
.3
5.2
5.2
6.9
G)(0
b
-0
A
-------
1-22
an average particulate emission level of around 0.60-0.65
g/BHP-hr. After allowing for some deterioration (these engines
were almost entirely new), it is estimated that today's HDDs
emit at an average of 0.7 g/BHP-hr in-use.
While the 0 . 7g/Bwp-hr level is aporopriate for today's
enoines, future HDDs should be able to reach, somewhat lower
particulate levels with relatively minor engine modifications
and recalibrations. The impetus to control HDD particulate
(other than the particles constituting "smoke" at certain
extreme engine operation modes) has not yet occurred since
there has been no particulate standard. With a standard,
however, some reduction in particulate emissions should occur.
For example, in its comments to the HDD particulate N?P.M,[11]
Caterpillar recommended a future non-trap standard of 0.6
g/BHP-hr, includinq DF and safety margin. For the purposes of
this analysis, this level will be used as the non-trap,
non-technology forcing, HDDE particulate standard to be
implemented sometime in the 1987-88 timeframe. Also, for the
purposes of this analysis, we have assumed that this standard
would be implemented in 1988. Thus, without the use of
trap-oxidizers, HDDEs will be projected to emit at 0.7 g/3HP-hr
through 1987 and at 0.6 q/BHP-hr thereafter.
B. Standard Level With Traps
The trap-based HDDE particulate standard of the base
scenario is 0.25 g/BHP-hr. This level was proposed by the
Agency in its HDDE particulate NPRM (46 FR 1910). The
percentage of HDDEs that would require traps under this
¦standard„„,is. 100 . .percent ..because , J.,t„ _ wa„s.. orp.pose.d. . .as.,,
hon-aver-aaing - -standard and • - all ' HDDEs ^currently. emi-t,
substantially above 0.25 g/BHP-hr. (The effect of averaging
will be considered later in this section.)
The 0.25 q/BHP-hr standard requires a 60 percent reduction
in particulate emissions from the 0.6 g/BHP-hr non-trap level
mentioned above. Both the ceramic trap and the wire mesh trap
have efficiencies greater than 60 percent. Under the base
scenario without averaqinq, it has been assumed that
manufacturers would only apply traps of the required efficiency
regardless of the type of trap used. This is to say that even
if ceramic traps were applied, there would be sufficient
impetus to reduce efficiency below that achievable (e.g., to
increase regeneration intervals and reduce backpressure and
fuel economy penalties) if the standard were more stringent,
that only the efficiency actually necessary, with a reasonable
safety margin, would be applied. This efficiency has been
assumed to be 65 percent. Applying this 65 percent efficiency
to the engine-out emission standard level of 0.6 g/BHP-hr,
results in tailpipe emissions of 0.21 g/BHP-hr under the base
scenario. This is somewhat lower than the required 0.25
-------
References
1. "Light-Duty Diesel NOx-HC-Particulate Trade-Off
Studies," In: Diesel Combustion and Emissions: Proceedings
of SAE Congress and Exposition, p. 86, Wade, w. r., SAE Paper
No. 300335, February 1980.
2. "Regulatory Analysis and Environmental Impact of
Final Emission Regulations for 1984 and Later Model Year
Heavy-Duty Engines," U.S. EPA, OANR, OMS, ECTD, SDSB, pp.
184-86, December 1979. - •
3. This Data is Publicly Available From the U.S. EPA
• Selective Enforcement Section, Manufacturer's Operations
Division, Office of Mobile Sources.
4. "Trap-Ox idizer Feasibility Study," U.S. EPA, OANR,
OMS, ECTD, SDSB, March 1982.
5. "Light-Duty Diesel Organic Material Control
Technology Investigation Program," EPA Contract No. 68-03-2873,
Monthly Progress Report No. 34, August 10, 1982.
6. Letter from B. E. Enga, Johnson-Matthev, Inc., to
Anne M. Gorsuch, Administrator, U.S. EPA, Regarding the 1985
Light-Duty Diesel Particulate Standards, January 25, 1982 (EPA
Docket A-91-20, II-D-75).
7. "The Impact of Light-Duty Diesel Particulate
Standards on the Level of Diesel Penetration in the Light-Duty
Vehicle and Light-Duty Truck Markets," Jack Faucett Associates,
For U.S.' EPA, Contract No. 68-01-6375.
8. This Data was Submitted by Heavy-Duty Diesel Engine
'"Manufacturers As Comments- to EPA's ' •HeaVy-Dtfttf"'1'Sel**
Particulate m'prm (46 FR 1910) and Can Be Found In" EPA "Public
Docket Mo. A-30-18.
9. "EMA/EPA Heavy-Duty Diesel Enaine Cooperative Test
Program," EPA Public Docket No. A-80-13, November 1982.
10. "Emissions From Heavy-Duty Enaines Using The 1984
Transient Test Procedure, Volume 2 - Diesel," U.S. EPA, OANR,
OMS, EPA-460/3-31-031, July 1981.
11. This Data is Contained In Caterpillar Tractor
Comoany's Comments to the Heavy-Duty Diesel Particulate NPRM
(46 FR 1910). Caterpillar's Comments Can Be Found In EPA
Public Docket No. A-80-18.
-------
1-23
manufactuTers will desire a somewhat larger safety margin due
to the variety of HDD application and the absence of averaging.
If averaging were implemented along with the 0.25 g/BHP-hr
standard for HDDEs, the percentage of vehicles requiring traps
would drop from 100 'to about 70' percent. In this case, we have
assumed that manufacturers would utilize the full 85 percent
efficiency of the ceramic trap in order to take full advantage
of averaging.
-------
CHAPTER 2
EMISSIONS IMPACTS
I. • Introduction
This chaDter assesses the impact of the base and relaxed
scenarios on total nationwide and urban diesel particulate
emissions in 199^ as comoared to those in 1980 and' 1986 . The
base scenario assumes particulate standards of 0.20 g/mi, 0.26
q/mi, and 0.25 g/BFP-hr for liaht-duty diesel vehicles (LDDVs),
liaht-dutv diesel trucks (LDDTs) and heavy-duty diesel engines
(HDDEs), resDectivelv. The relaxed scenario assumes
non-technoloqy forcinq, non-trap particulate standards for all
three vehicle classes (i.e., LDDVs and LDDTs will continue to
emit' at current Darticulate levels, which are well below the
current standard of 0.60 a/mi, while HDDEs will emit at a level
of 0.60 a/BHP-hr beqinnina in 1988). Under both scenarios, the
current NOx standards for LDDVs and LDDTs (i.e., 1.5 and 2.3
q/mi, respectively) are assumed to remain in effect. The HDDE
NOx standard is not. identified per se, but must be of such
strinaency as to allow a non-trap particulate standard of 0.60
q/BH^-hr to be met.
The first section of this chapter estimates 1980, 1986 and
1995 particulate emission factors by vehicle type and model
vear under the two control scenarios. The second section
calculates nationwide and urban emissions for both control
scenarios by combinina these emission factors with vehicle
miles traveled (VMT), breakdowns by model year, diesel sales
fractions, and nationwide and urban VMT projections. The third
section compares some of these results with those of previous
EPA analvses.
II. Emission Factors
The initial step in determinina nationwide and urban
diesel particulate emissions is to estimate emission factors
for the vehicles of each model vear which comprise the 1980 ,
1986 and 1995 fleets. Generally soeakina, emission factors are
the averaae emission rates (in g/mi) that vehicles of a certain
type and aqe are expected to emit durinq in-use operation,
^mission factors usually must be determined through in-use
testinq because owner problems such as tampering, improper
maintenance, and abuse can substantially chanae actual emission
levels from certification test levels. However, studies[l,21
have, shown that in-use particulate emissions from diesel
enaines remain at certification test levels (with appropriate
allowance made for normal deterioration) throuqhout the life of
the vehicle (i.e., the owner-related problems mentioned above
do not aopear to sianificantlv influence diesel particulate
emissions). Therefore, the diesel particulate emission factors
-------
2-2
estimated for this study are derived from current certification
data in the case of LDDVs and LDDTs and from manufacturer and
Aaencv test data in the case of PDDs. These data sources are
fully described in Chapter 1.
A. Relaxed Scenario
1. Liaht-Putv. Diesel Vehicles and Light-Duty' Diesel
Trucks :
The projected post-1980 LDDV and LDDT emission factors
under the relaxed scenario are easily determined, since it is
assumed that these vehicles will continue to emit at their
current levels. These current levels have already been
determined in Chapter 1 and are simply the achievable half-life
particulate standard levels shown in Table 1-2 of that
chaDter. As discussed in Chapter 1, the achievable particulate
standard level is the current certification test level
multiplied by the 50,000-mile deterioration factor (DF) and a
10 percent safety margin (to account for production
variability) . Since the lifetime of a typical LDDV or LDDT
islabout 100,000 miles, the half-life standard level can be
viewed as the average emission rate over the life of the
vehicle. That is, for the first 50,000 miles of its life, the
vehicle will emit below the standard level and for the second
50,000 miles the vehicle will emit above the standard level.
Weightinq these emission levels by the Drojected 1983
sales of each configuration yields fleet average emission
factors of 0.27 g/mi for LDDVs and 0.28 g/mi for LDDTs. These
e_miss_ion factors will be applied to each and every model year
x ep^ese'n'te'd',. i'rr 7 * f K e T9 9 5; ~. cMie n 3 a r ve a r„ ; fleet". Strictly
speaking, this "would "'not" be"~~tfie" *ca~se~" since" older """vehicles
generally have hiqher emissions due to more deterioration and
vice versa. However, the 50,000 mile deterioration factors for
LDDVs and LDDTs are less than 1.1 on the average (i.e., a 10
Dercent increase in 50,000 miles). Thus, while the emission
factor for newer vehicles is slightly overestimated
(deterioration at this point is less than average), the
emission factor for older vehicles is slightly underestimated,
and the net result is virtually the same as if each model
year's vehicles were assigned slightly different emission
factors based on the deterioration occurring between individual
model years.
-------
2-3
Pre-1980 model year vehicles qenerally emitted hiaher
levels of particulate than those of later years. Emission
factors for these years were estimated from the historical
emission levels and sales of these vehicles[31 and are shown
below:
Model Year LDDV LDDT
1980 0.5 0.5
1Q79 0.8 0.9
1978 0.7 0.9
1975-77 0.5 0.5
1971-74 0.5
2. Heavv-Duty Diesels
Estimatina emission factors for HDDEs is much more
complicated than estimating emission factors for LDDVs and
LDDTs, because HDDE emissions are measured in terms of grams
per brake horsepower-hour (a/BHP-hr) and not g/mi, as only the
enaine is tested and not the entire vehicle. Because vehicle
emissions (in g/mi) can vary widely at a constant g/BHP-hr
engine emission level, due to widely varying vehicle weights
and sizes, the conversion of g/BHP-hr emission rates to g/mi
equivalents in order to obtain HDD emission factors is not a
simple process.
The general equation relating engine emission rate and
vehicle emission rate is as follows:
Vehicle emission factor = emission rate x fuel density (1)
; _ _ _ /. •• ¦¦ BSFC -x- fuel-economv
= ^/BHP~hr x lb/gal
Ib/BHP-hr x mile/gallon ,
= g/mile,
where BSFC is the enoine brake-SDecific fuel consumption and
the fuel density for diesel fuel is 7.1 lb/aal.
It was determined in Chapter 1 that the engine emission
rate under the relaxed scenario would be 0.70 g/BHP-hr for 1987
and earlier HDDs and 0.60 a/BHP-hr for 1988 and later HDDEs.
This leaves two factors still to be determined: vehicle fuel
economy and enaine brake-specific fuel consumption (BSFC).
-------
2-4
a. • Heavy-Duty Diesel Fuel Economy Estimates
The fuel economy of heavy-duty diesel vehicles (HDDVs),
like that of other vehicle types, is expected to increase in
the future. This necessitates the use of projections and
prevents the sole use of current HDDV fuel economy data.
Present and future HHDV fuel economies were estimated for
four vehicle subgroups based on an analysis of data from
various sources. (This analysis is contained in Reference 4.)
The HDDV subgroups are defined by gross vehicle weight ratina
(Wffl) as follows*:
Class IT3 = 8,500 ud to 10,000 lbs.
Classes III-V = 10,001 to 19,500 lbs.
Class VI = 19,501 to 26,000 lbs.
Classes VII and VIII = 26,001 lbs. and ud.
Current fuel economies for Classes IIB, III-V, and VI were
derived from fuel consumption modeling results published by the
Energy and Environmental Analysis, Inc. (EEA) for the U.S.
Department of Enerqv. The EEA estimates were not used directly
because the fuel consumption values are based on total VMT and,
hence, are more indicative of hiahway fuel consumption rather
than urban fuel consumption. This latter oarameter is the most
important here since the objective of this study is primarily
to evaluate the environmental impact of particulte emissions in
urban areas. Therefore, the EEA estimates for Classes IIB,
III-V, and VI were reduced by 20 percent to represent urban
fuel economies.
The- current fuel economy for Classes VII-VIII was taken
?r onr:" test resul't's '"""collected -by-"Sou thwes t"--"" Re sea rch-—-T-rvs t-itute
(SwRi) under contract to EPA. These data were obtained using
urban test cycles and, hence, are already representative of
urban fuel consumption. For comparison, the EEA value for
Classes VII-VIII is aenerally about 25 percent higher than the
SwRi estimate.
Future fuel economy improvements for the four HDDV
categories were derived from the above-mentioned EEA modelinq
results. As before, the values for Classes 113, III-V, and VI
were reduced by 20 percent to reflect urban fuel consumption.
For Classes VII-VIII, the EEA estimates still aopeared to
remain more representative of highway fuel usage rather than
urban fuel usage even if they were reduced by 20 percent. This
is explained in that many of the expected fuel economy
improvement technologies for these laraer vehicles should be
more beneficial during highway cruising than during the
stop-and-go driving which is characteristic of urban areas. To
account for this difference, the largest overall increase of
-------
2-5
the other, three cateqories (i.e., 15 percent improvement from
1980 to 1991) was also used to represent the fuel economy
improvement for category VII-VIII.
The HDDV fuel economy estimates are shown in Table 2-1.
b. ^eavv-Dutv Diesel Brake-Specific Fuel Consumption
The second factor of the Vehicle-emission eauation which
needs to be estimated is HDOE brake-specific fuel consumption
(BSFC). ^s with HDDV fuel economies, estimates of BSFC for the
four weight categories were based on an analysis of data from
various sources. (This analysis is contained in Reference 4.)
The important factors which are used to identify future fuel
consumption improvements are the: 1) enqine fuel-saving
technologies, 2) urban fuel economy gains for each technology,
and 3) market penetration of each technology.
Table 2-2 presents HDDE BSFC by model year.
c. Heavv-Duty Diesel Fmission Factors
Having estimated fuel economies and brake-specific fuel
consumptions for each of the four HDD groups, the vehicle
emission factors (g/mi) for each group by model year were
calculated using equation 1 and are shown in Table 2-3.
These HDD emission factors, like those for LDD^s and
LDDTs, all include half-life (or average) deterioration and the
fact that newer vehicles have slightly lower emissions, and
older vehicles slightly higher emissions, is ignored. This is
... again,, .very acceptable, since deterioration of HDD particulate
: -.emission-s'. :shouid be very .low (about ,15--percent over the--life-
the vehicle) .
B. Base Scenario
The base scenario differs from the relaxed scenario only
in the fact that some vehicles in the base scenario are
equipped with trap-oxidizers. Thus, except for any unique
features of trap-oxidizers which affect in-use emissions, the
methodoloav used here is the same as that described above for
the relaxed scenario. That is, certification data with average
deterioration and an appropriate safety marain are assumed to
adequately represent in-use emissions. (Emission factors for
calendar years 1980 through 1986 do not need to be readdressed
since the base-scenario standard does not take effect until
1987 for LDDVs and LDDTs and 1988 for HDDVs.)
-------
2-6
Table 2-1
HDDV Fuel Economies (mpq)
Model Year Class IIB Classes III-V Class VI Classes VII-VIII
7.6
1995
1994
1993
1992
1991
1990
1989
1988
1987
1986
1985
1984
1983
19%7::
1981
1980 +
13.1
13.1
13.0
13 .0
13.0
13.0
12.8
12.7
12.5
12.3
12.2
12.0
11.8
liYr
11.6
11.4
10.6
10 .4
10.2
10.1
9.9
9.8
9.7
9.7
9.6
9.6
9.5
9.4
9 .4
• • — *
- 9>4-
9.3
9.2
7.6
7.6
7.6
7.6
7.6
7.5
7.5
7.4
7.4
7.4
7.3
7.2
i ;t
7.0
7.0
5.12
5.10
5.09
5.07
5.06
5.04
4 .98
4.92
4 .85
4.79
4.73
4.67
4.62
4^ 56
4 . 50
4.45
-------
2-7
Table 2-2
HDDE Fuel
ConsumDt ions
(lbm fuel/BHP
-hr)
!odel Year
Class IIB
Classes III
-V Class VI
Classes vil-vin
. 1995
0.41
0.39
0.41
0.39
1994
0.41
0.39
0.41
0.39
1993
0.41
0.40
0.41
0.39
1992
0.41
0 ."4 0
0.41
0.39
1991
0.41
0.41
0.41
0.39
1990
D .41
0.41
0.41
0.39
1989
0.42
0.42
0.41
0.40
1988
0.42
0.42
0.41
0 .40
1987
0.42
0.42
0.42
. 0.40
1986
.0.42
0.42
0.42
0.41
1985
0.42
0.42
0.42
0.41
1934
0.42
0.42
0.42
0.42
..1983 ¦ -
• . 0.42,
; - 0.4.2
, ,0.43.
0.42
1932
0.42
0.42
0.43
0.42
1981
0.42
0.43
0 .43
0.43
1980 +
0.43
0.4 3
0.43
0.43
-------
• 2-8
Table 2-3
Relaxed Scenario HDDV Emission Factors (a/mi)
Model Year Class IIB Classes III-V Class VI Classes VII-VIII
1995
0.80
1.04
1.38
2.13
1994
0.80
1.04
1.38
2.14
1993
0.80
1.05
1.38
2.14
1992 ¦
0.80- -
1.05 -
1.38
2.14
1991
0.80
1.05
1.38
2.15
1990
0.80
1.06
1.38
2.15
1989
0.80
1.06
1.38
2.16
1988
0.81
1.06
1.38
2.16
1987
0.95
1.24
1.61
2. 53
1986
0.97
1.24
1.61
2.53
198 5
0.97
1.24
¦1.61
2. 55
1984
0.98
1.25
1.61
2 . 56
1983
0.99
1.25
1.62
2.56
1982
- ¦'" TAs-'--€—
t-v 6 —
1981
1.00
1.25
1.65
2.59
1980 +
1.01
1.26
1.65
2.60
-------
2-9
The . one feature of trap-oxidizers which may affect this
relationship between certification and in-use emissions is the
possibility of traD failure. Trap-oxidizer systems are not
currently being used on any vehicles, and therefore, there are
no data on their reliability in-use. Limited data on
trap-oxidizer system durability has been generated by
experimental testing programs. [5] These programs have
demonstrated that traps can physically undergo repeated
regeneration cycles over 50,000 miles of vehicle operation and
still maintain their initial trapping efficiencies. However,
these test oroarams involved only a few vehicles and somewhat
controlled operating conditions. It is possible that when put
into' general use, some failures of trap-oxidizer systems will
occur.
The reasons for failure of a trap-oxidizer system can be
divided into two general categories: 1) failure of the
electronic control system used to reaenerate the trap, and 2)
physical failure of the trap due to unforeseen operating
conditions. Electronic control systems consisting of
microprocessors and central processing units (CPUs) have come
into widespread use on light-duty vehicles since 1980. These
control systems, used in conjunction with three-way catalysts,
are necessary to attain the 1981 emission standards for many
vehicles. Recent testing of in-use vehicles by EPA's Emission
Factor Testing Program[6] has generated data on the failure
rate of these electronic control systems. That data indicates
that 1.5 to 2.0 percent of 1-vear old liaht-duty vehicles of
1981-82 vintage are gross emitters of HC and CO. Since it is
reasonable to assume that the reason for the gross emissions is
failure of the electronic control system, it can be concluded
..that the . failure . rate . for .electronic, .control systems., for these
model year vehicles was about 1.5" to 2.0 percent per year. "¦•It-
should be noted, that these results are based on a limited
number of vehicle tests and could be subject to change in the
future.
This failure rate should be adjusted to account for the
fact that this electronic control technology is relatively new
and that, for the purposes of this study, trap-oxidizer systems
will not be required before 1987. The industry has five more
years to reduce the failure rate of electronic control
systems. Therefore, the failure rate for 1987 and later
electronic control svstems used on trap-oxidizers is estimated
to be 1.0 percent per year.
The other general cateaorv of trap-oxidizer system
failure, as mentioned above, is the occurance of unforeseen
operating conditions. Manufacturers will design trap-oxidizer
svstems to withstand almost every in-use condition they can
foresee. However, it is still possible that certain ooeratina
conditions will occur which prevent proper regeneration of the
-------
2-10
trap, thus, leading to eventual trap failure. Therefore, a
failure rate of 0.5 percent per year will be used in this
analysis for this second type of trap-oxidizer system failure.
Adding the electronic control system failure rate to the
unforeseen operatina conditions failure rate yields' an overall
failure rate of 1.5 percent per year for LDDVs with traps.
This overall failure rate will also be used for LDDTs and
MDV/LHDVs because their annual mileaqes and lifetimes are
similar to those for LDDVs. HDDVs, however, while having
approximately the same lifetime as these other vehicles, are
driven, on the averaqe, substantially more miles per year.
Therefore, the 1.5 percent per year failure rate was adjusted
for HHDVs to reflect the qreater (factor of four) annual number
of miles by these vehicles. In doing this, the 1.0 percent per
year electronic failure rate was held constant since these
types of failures were assumed to be primarily due to factors
such as time and transients in engine compartment temperature,
which here depend more on time than annual vehicle mileage.
The 0.5 percent Der year failure rate due to the occurence of
unforeseen operating conditions, on the other hand, was assumed
to be partially dependent on annual mileage and was doubled.
Thus, the trap failure rate used for HDDVs was 2.0 percent per
year.
Having determined the trap-oxidizer system failure rates
- - for--the different vehicle types, these failure rates can be
combined with the basic methodology used to estimate the
emission factors under the relaxed scenario to estimate
emission factors under the base scenario. The results of this
combination are shown in Table 2-4.
¦ a i-am..i£:a.®tog/Sy.y fo,C;;,-JL.bi)V"s'= *and.^£•
-year-s 19-78 through 1986 and for HDDs from 1978 through 19 8 7"* a re"
the same as those under the relaxed scenario. This occurs
because the more stringent particulate standards of the base
scenario do not become effective until 1987 in the case of
LDDVs and LDDTs and 1988 in the case of HDDs.
When the new standards do become effective, it is aqain
assumed that vehicles will emit, on the average, at their
applicable standard levels, except for the effect of trap
failure. These applicable standard levels are 0.20 g/mi for
LDDVs, 0.26 g/mi for LDD^s, and a 60 percent reduction from the
relaxed-scenario levels identified in the previous section for
HDDs. To these levels must be added the effect of trap
failure. This is done according to the following equation:
Model Year Emission Factor = Standard Level + (Vehicle
Age) x (Trap Failure Rate) x (Fraction of Vehicles with
Traps) x (Difference between Non-trap Emissions and
Standard Level)
-------
2-11
Table 2-4
Base
Scenar io
Emission
Factors (q/mi)
Veh icle
Model Year
LDDV
LDDT
HDV
Class
IIB
HDV
Classes
irr-v
LHDV
FHDV
1995
.20
.26
0.34
0.44
0.58
0.90
1994
.20
.26
0.34
0.45
0. 59
0.93
1993
.20
.26
0.35
0.46
0.60
0.95
1992
.20
.26
0.36
0.47
0.62
0 .98
1991
.20
.26
0.36
0.48
0.63
1.01
1990
.20
.26
0.37
0.49
0.64
1.03
1989
.20
.26
0.38
0.50
0.65
1.06
1988 *
.20
.26
0.39
0.51
0.67
1.09
1987**
.20
.26
0.95
1.24
1.61
2.53
1986
.27
.28
0.97
1.24
1.61
2.53
1985
.27
.28
0.97
1.24
1.61
2.55
1984
.27
.28
0.98
1.25
1.62
2.56
1983 -
.27
: .. . 28
0.99.
1.25 ¦:
; 1. 62" ¦
2.56
1982
.27
.28
1.00
1.25
1.63
2 . 58
1981
.27
.28
1.00
1.25
1.65
2.59
1980
.50
. 50
1.01
1.26
1.65
2.60
1979
.80
.90
1.01
1.26
1.65
2.60
1978 +
.70
.90
1.01
1.26
1.65
2.60
~
~ *
3ase scenario becomes effective for HDDs.
Base scenario becomes effective for LDDVs and LDDTs.
-------
2-12
Some . of the terms in the above equation deserve some
elaboration. Vehicle age is assumed to 0.5 years for 1995' model
vear vehicles and one year greater for each preceding model
year. Trap failure rate is 1.5 percent for LDDVs, LDDTs and
MDV/LHDVs and 2.0 percent for HHDVs. The fraction of vehicles
with traps is included in the above equation because the trap
failure rate should only be applied to vehicles with traps.
This figure is .0 . 223 for LDDVs, 0 . 076 for LDDTs and 1.00 for
all HDDVs.
The difference between non-trap emissions and standard
level is included to account for the fact that the vehicle
emissions should simply revert back to their non-trap levels if
the trap should fail. The standard "level is subtracted because
emissions up to this level have alreadv been taken into account
by the first term on the riaht hand side of the equation
(standard level). In the case of HDDVs, the non-trap emissions
are simply those occurring under the relaxed scenario, because
all HDDVs were assumed in Chapter 1 to emit at the same level
(i.e., the non-trap level of trap-equipped vehicles is the same
as the emission level of vehicles without traos). However, a
distribution of vehicle emissions was determined in Chapter 1
for LDDVs and LDDTs and traps were placed on the highest
emitting vehicles first. Thus, the non-trap levels for
tr ap-equ ipped LDDVs an.d LDDTs (0.39 c/mi and 0.33 a/mi,
respectively) are higher- than the non-trap levels of the
relaxed scenar ios (0 . 27- .g/mi. and . 0 . 28 q/mi, respectively).
IIT. Nationwide and Urban Emissions
The next step in determining nationwide and urban
emiss.ions._;-=is- to combine ..-the "model, ye.ar," .emission,, factors
z-z--.5the-i-p.r:e'vi"o:as:rs«c.t±on:r.fAr.."ieach"^vehicl.e tvp.e -into^-arlClZ'r.
single, weighted calendar-year emission factor for each vehicle
tvoe. This is done by multiDlying each model year's emission
factor by that model year's fraction of calendar-year VMT and
the diesel sales fraction for that model year, and then
summming across all model years. The result is an emission
factor that is appropriately weighted by both the number of
diesels on the road, relative to total vehicles, and by their
age. In other words, the 1995 weiahted emission factor is now
on a total (i.e., qasoline and diesel combined) VMT basis for
that vehicle type.
The 1995 distributions of VMT by model year [71 are shown
in Table 2-5 for LDVs, LDTs, and HDVs. It should be noted that
the VMT breakdown shown for HDV Classes 113, TII-V, and VI is
that given in the reference for aasol ine-fueled HDVs and the
VMT breakdown shown for HDV Classes VII-VIII is that for
diesel-powered HDVs. This is appropriate because at the time
the referenced study was performed, the great majority of
gasoline-fueled HDVs were in Classes IIB-VI and nearly all HDDs
-------
2-13
Table 2-5
1995 Calendar Year Fleet-Wide Average
VMT Fraction Distribution hv Model Year
Classes HDV
IIB, III-V* Classes
Model Year
LDV
LDT
Class VI
VII-VIII
1995
.091
.159
.201
.247
1994
.124
.137
.161
.188
1993
.108
.108
. 124
.102
1992
.080
.072
.084
.058
1991
. 100
. 096
.090
.093
1990
.107
.098
.083
.080
1989
.088
.068
.059
.056
1988
.067
.050
.041
.038
1987
.059
.035
.029
.029
1986
.050
.035
.028
.028
1985
.038
.032
.024
.020
1984 _
.026
.021
.017
.015
1983
.021
. 02 2 '
.015
.015
1982
.015
.019
.012
.011
1981
.009
.014 '
.009
.007
1980
.006
.011
.007
.005
1979
.003
.007
.005
.003
1978
.001
.005
.003
.001
These VMT fractions are used for each HDV subgroup
separately.
-------
2-14
were in Classes VII and VIII. However, the use of the
historical Class II3-VI breakdown here does assume that the
dieselization of this class will not alter this breakdown.
The diesel sales fractions for each model year are shown
in Table 2-6 for LDVs and LDTs, and in Table 2-7 for HDVs. Two
sets of projections are used in this study. The first is a
"best estimate" projection and is based on a continuation of
present conditions, including the absence of a major oil
crisis. This results in moderate growth of diesel sales. The
second set is a "worst case" projection, which could be
realized if another oil crisis were to occur. Here, the rate
of diesel sales is substantially" hiaher than under the best
estimate projections. The term "worst case" refers to the
degree of environmental impact which would occur due to diesel
particulate emissions.
Regarding the best estimate diesel sales fractions,
historical diesel and total sales data were used for model
years 1961-82. The LD sales fractions for model years 1990
through 1995 are those determined in a study[8] for EPA by Jack
Faucett Associates which investigated the impact on diesel
penetration in the LDV and LDT markets of diesel particulate
standards. The LDV and LDT diesel sales fractions for model
years 1983-89 were obtained by linearly interpolating between
the fiaures for 1982 and 1990 . The 1985 , 1990 , and 1995 HDV
sales fractions were derived from projections made by Data
Resources Inc.,[9] with the in-between years again being
obtained by linear interpolation.
Regard ing ....t.h.e. . worpt .e.a,se,: - sales fr..ac.ti,o.ns, in-hojuse
•-*e.stima:fees were .used., to -T-epresent-swhat i-s, considered ..to. be -the.:-;
maximum diesel penetration in this timeframe. For model years
1961-83, the diesel sales fractions are, or course, identical
to the best estimate diesel sales fractions because they are
based on historical data.
For LDVs, a maximum diesel penetration rate for the 1995
model year was projected to be 30 percent. It was also thought
that most of the increase in diesel penetration between 1984
and 1995 would occur in the first half of this time span.
Thus, the LDV penetration rate rises by three percentage points
per year from 1984 through 1990 and after which rises by only
one percentage point per year through 1995.
For LDTs, a maximum diesel penetration rate of 60 percent
was projected for 1995. Unlike LDVs, however, the increase in
. LDT dieselization is likely to be more consistent with time,
due to the fact that significant dieselization is already
occurring under the best estimate projections. Therefore, a
constant increase of four percentage points per year was
projected from 1985 through 1995.
-------
2-15
Diesel
Table 2-6
Fraction of Total Liqht-Dutv
Veh icle
Sales
Best
Estimate
Worst
Estimate
Model Year
LDDV
LDDT
LDDV
LDDT
1995
.115
.339
.300
.600
1994
.115
.330
.290
. 560
1993
.114
.321
.280
. 520
1992
.114
.312
.270
.480
1991
.113
.303
.260
.440
1990
.113
.294
.250
.400
1989 -
.100-
.27 - -
.220
.360
1988
.090
.240
.190
.320
1987
.080
.210
.160
.280
1986
.073
. 180
.130
.240
1985
.066
.160
.100
.200
1984
.060
.130
.070
. 150
_ 1983
.053
.100
.053
.100
1982
.046
.080
.046
.080
1981
.061
.060
.061
.060
1980
.034
.034
.034
.034
1979
.028
.028
.028
.028
1978
.009
.009
.009
.009
1977
.004
.005
.004
.005
1976
.003
.003
.003
.003
1975
.003
v00 2
.003
.002
1974
.003
.000
.003
.000
1973
.003
.000
.003
.000
1972
.003
.000
.003
.000
1971
.003
. 000
.003
.000
; v.; .'i.9i7'0+ "" "•
.'000
. 000' • - - '
.000
.000
-------
Model
Year
1995
1994
1993
1992
1991
1990
1989
1988
1987
1986
1985
1984
1983
1982
1981
1980
1979
1978
1977
1976
1975
1974
1973 "
1*9 7 2
1971
1970
1969 +
2-16
Table 2-7
Diesel Fraction of Total Heavy-Duty Vehicle Sales
3est
Est imate
Worst
Est imate
Class
Classes
Class
Classes
Class
C lasses
Class
Classes
113
III-V
VI
VII-VIIT
113
III-V
VI
VII-VI11
.371
.476
.669
.983
.895
1.000
1.000
1.000
.357
.4 63
. 645
.980
.841
1.000
1.000
1.000
.343
.449
.621
.978
.789
1.000
1.000
1.000
.329
.436
. 598
.975
.741
.949
1.000
1.000
.315
.422
.574
.973
. 694
.910
1.000
1.000
.301
.409
. 550
.970
.648
.864
1.000
1.000
.287
.396
.526
.967
.546
.764
1.000
1.000
.273
.382
. 502
.965
.546
.764
1.000
1.000
.259
.369
.479
.962
.503
. 716
.929
1.000
.245
.355
.455
.960
.422
-.612
. 784 •
1.000
.231
. 342
.431
.957
. 3 44,
. 510
.642
.949
.179
.264
.369
.947
.256
.377
.513
.958
.126
.186
.286
.937
.126
.186
.286
.937
.074
.108
.214
.928
.074
.108
.214
.928
.037
.054
. 164
.918
.037
.054
. 164
.918
.000
.000
. 114
.91
.000
.000
. 114
.91
.000
.000
. 114
.89
.000
.000
.114
.89
.000
.000
. 078
.88
.000
. 000
.078
.88
.000
.000
.070
.85
.000
. 000
.070
.85
.000
.000
. 042
.83
.000
.000
.042
.83
.000
.004
.032
.73
.000
.004
.032
.73
.000
.001
.016
.77
.000
.001
.016
. 77
" 000- '
-.00-3
.016
.78
.000- -
.00 3
- -. 016 .¦
.73
. 000 -
-.020
¦ • .016
.76
. 00 0
' .-0-20
.76-
.000
.020
.015
.75
.000
.020
.016
.75
. 000
.020
.016
.75
.000
.020
.016
.75
.000
.000
.000
.75
.000
.000
.000
.75
-------
2-17
For the four classes of HDVs, the worst case dieselization
rates were derived by estimating the year that total
dieselization would occur and then by linear interpolation to
historic levels. These years were 1997 for Class lib, 1993 for
Classes III-V, 1988 for Class VI, and 1986 for Classes VII-VIII.
The weighted emission factors (g/mi) for each calendar
year, vehicle type, control scenario, and diesel sales scenario
are shown in Table 2-8, along with estimates of total VMT
(aasoline plus diesel) and the urban percent of VMT for each
vehicle type.
'Estimates qf total nationwide VMT for the years 1980,
19'86,~and 1996 were obtained from an EEA Quarterly Repor t. [ 101-¦
The urban/rural splits were obtained from U.S. Federal Highway
Administration data.[11] It should be noted that this
urban/rural split data for HDVs was not broken according to
vehicle size but by generic type (i.e., bus, single-unit truck,
tractor-trailer combination). It was assumed that buses and
single-unit trucks were Classes IIB-VI vehicles and that
tractor-trailers were Class VII and vin vehicles.
Nationwide emission estimates are obtained by simply
multiplying the weighted emission factors by VMT. rjrban
emissions are obtained by multiplying the nationwide emissions
estimates by the urban VMT fraction. These figures are shown
in Tables 2-9 and 2-10. It should be noted that the" emission
estimates in these tables for HDDV Classes IIB, III-V, and VI
have been combined into a single category labelled medium-dutv
vehicle/1ight heavv-duty vehicle (MDV/LHDV) to ease the
presentation of the results. The subsequent discussion will
focus on the urban emission results of Table 2-10 as these are
the" most pert'inen't"" with respect '"''to" human' exposure" t'o "diesel
particulate 'emissions'.""
Table 2-10 has been, arranged to depict a number of
effects. One, projections for calendar years 1980, 1986, and
1995 have been placed side-by-side to allow easy comparison.
Two, the effects of both the relaxed and base scenarios are
shown in 1995 to depict the effect of control. Because the
control of LDDVs and LDDTs provides so little control relative
to wddv control, a modified base scenario has been added where
only HDDV emissions are controlled. Three, an attempt has been
made to depict the causes of the increases in total urban
emissions between 1980 and future years. Beside each emission
estimate for 1986 and 1995 is a percentage which indicates that
vehicle class' contribution to the overall increase in urban
emissions between 1980 and that year. "or example, LDDV
emissions are 24 , 600 metric tons per year in 1995 under the
best estimate, relaxed scenario. This is an increase of 20,700
metric tons per year from the 1980 level. The 30 percent
-------
2-18
Table 2-8
Weighted Emission Factors and Projected VMT
HDV
Class Classes Class Classes
LDV LOT IIB III-V \r[ VII-VTII
lighted Emission Factor (g/Tni)
Calendar Year 1980:
All Scenarios 0.0059 0.0075 0.000 0.0027 0.11 2.19
Calendar Year 1986;
Best Estimate Diesel Sales 0.014 0.027 0.13 0.24 0.46 2.37
Worst Case Diesel Sales 0.016 0.032 0.19 0.36 0.66 2.41
Calendar Year 1995:
Best Estimate Diesel Sales
Relaxed Scenario 0.027 0.076 0.25 0.44 0.80 2.13
Base Scenario 0.021 0.071 0.12 0.22 0.40 1.14
Worst Case Diesel Sales
Relaxed Scenario 0.061 0.12 0.56 0.91 1.30 2.18
3ase Scenario .0.046 0.11 0.27 0.44 0.65 1.17
Projected V^TT MO^.^iles) : [10] • _ . rV.~-V-*"
1980 1,118 209 13.8 6.63 18.4 73.8
1986 1,220 241 24.4 4.56 12.3 85.7
1995 1,540 330 40.5 4.69 9.97 117.9
Urban Percent
og VMT (all years)[111
59 49
49
49 49 27
-------
2-19
Table 2-9
Nationwide Diesel Particulate Emissions
(metric tons per year)
Best E
stimate Diesel
Sales
1995
1980
1986
Relaxed
Scenar io
Base
Scenar io
LDDV
6,500
16,400
41,500
32 ,200
LDDT
1,900
7,200
2 5,000
23,600
MDV/LHDV
2 ,000
6, 500
19,300
9,600
HHDV
149,000
200,000
251,000
134 ,000
Total
159,400
230,100
336,800
199,400
Wo r s t
Case Diesel Sales
1995
1980
1986
?e laxed'
Scenar io
Base
Scenar io
LDDV
6,500
19,900
93,100
71,400
LDDT
1,900
8,400
38,500
36,000
MDV/LHDV_
.2 ,000
1.5.,. 5.0,0 ..
„.3.8,, 300 .
18,600
HHDV
149,000
202,000
257,000
139,000
Total
159,400
245,800
426,900
265 ,000
-------
2-20
Table 2-10
Urban Diesel Particulate Emissions
(metric tons per year)
Best Estimate Diesel Sales
1995
1995
1980
1986
Relaxed
Scenario
3ase
Scenario
3ase Scenario
Onlv HDD Control
LDCV
3,900
9,700
(24%)*
24,600
(30%)
19,100
(60%)
24,600
(64%)
ldctt
900
3,500
(11%)
12,200
(17%)
11,500
(41%)
12,200
(36%)
MDV/LHDV
1,000
3,200
(9%)
9,400
(12%)
4,700
(14%)
4,700
(12%)
HHD7
40,000
53,700
(56%)
67,600
(41%)
36,100
(-15%)
36,100
(-12%)
Total
45,800
70,100
113,800
71,400
77,600
Worst Case Diesel Sales
LDCV
= LDcrr. .
•VDV/LHDV
HFDV
Total
1980
3,9C0
900
1,000
40,000
45,800
1986
11,800 (24%)
.. 4,.100 (109s)
7,600 (21%)
54,500 , (45%)
78,000
1995
Relaxed
Scenario
Base
Scenario
1995
55,300 (44%) 42,400 (64%)
18,300.. .(16%) .17,.600 (28%) .
18,700 (15%) 9,100 (13%)
69,200 (25%) 37,000 (-5%)
162,000 106,100
Base Scenario
Only HDD Control
55,300 (69%)
...... 18.,.80.0...(.23%) .
9,100 (11%)
37,000 (-4%)
120,400
*
Figures in parentheses depict each vehicle class contribution to the overall
emissions increase over 1980 emissions (in percent). The sum of the
percentages for the four classes is 100 percent.
-------
2-21
fiaure beside the 24,600 metric ton per year estimate indicates
that the "20,700 metric ton per year increase is 30 percent of
the total increase in urban emissions between 1980 and 1995,
69,300 metric tons per year.
Concerning the actual figures in Table 2-10, it can be
seen that urban emissions increase between 1980 and 1995
reaardless of the scenario chosen. The increase is smallest
for the best estimate, base scenario (57 percent) and largest
for the worst case, relaxed scenario (257 percent). As can be
seen from the figures in parentheses, the largest contributor
to these increases are LDDVs. HHDVs contribute to the
increases under the relaxed scenarios, but actually serve to
mitigate such increases., under the relaxed scenarios. . Also,
while LDDVs, and LDDTs in some cases, produce the largest
emission increases, their control under the base scenario has
the least effect. LDDV emissions are only reduced 22 percent
and LDDT emissions only 6 percent, as opposed to MDV/LHDV and
HHDV emission reductions of about 50 percent. Finally, the
effect of only controlling HDD emissions and avoiding further
control of LDDV and LDDT emissions is small. Overall urban
emissions only increase about 10-15 percent.
A final pertinent aspect of the urban emission estimates
of Table 2-10 is the relative contribution of each vehicle type
to overall urban emissions. Table 2-11 shows the fraction of
total urban emissions in each year being emitted by each
vehicle class. As can be seen, the relative contributions vary
dependinq on which situation is examined. One aeneral
observation is that, despite its low urban VMT fraction, HHDVs
are still major contributors to urban emissions regardless of
diesel sales scenario (e.g., 31 to 45 percent under the relaxed
scenario).' • .-.r.
I". Comparison of Results with Previous Studies
It is also Dertinent to comDare the results of Table 2-10
to the projections of urban diesel particulate emissions of
previous studies. This was done for two cases: best estimate
and worst case diesel sales.
The Regulatory Analysis which accompanied the 1982
light-duty diesel particulate regulation[3] estimated
nationwide light-duty diesel particulates in the year 1990.
Two scenarios were analyzed: 1) an uncontrolled scenario where
light-duty diesel vehicles and trucks were projected to emit
1.0 g/mi particulate, and 2) a controlled scenario with a 0.60
g/mi standard for 1982-84 and a 0.2 g/mi standard for 1985 and
beyond (0.26 g/mi for light trucks). (This controlled scenario
-------
2-22
Table 2-11
Relative Contribution of
Urban Emissions (percent)
Best
Estimate Diesel
Sales
1995
1995
-
'Relaxed
Base
Base
Scenar io
1980
1986
Scenario Scenario
Only
HDD Control
LDDV
9%
14%
22%
26%
32%
LDDT
2%
5%
111
16%
161
MDV/LHDV
2%
5%
8%
7%
6%
HHDV
87%
76%
59%
51%
46%
Total
100%
100%
100%
100%
1001
Worst Case Diesel Sales
1995
Relaxed Base Base Scenario
1980
1986
Scenar io
Scenar io
Only HDD Control
LDDV
9%
15%
34%
40%
46%
LDDT
2%
5%
12%
17%
16%
MDVyLHDt*"
'£'io¥ *¦
8%
*° ' 7 % *"
HHDV
87%
70%
43%
35%
31%
Total
100%
100%
100%
100%
100%
-------
2-23
is the same as the base scenario of this study, except here the
1985 standards have been delayed to 1987.) a range of
potential diesel penetrations was examined by applying a +25
percent bracket around a "best estimate" diesel saTes
scenario. The LDDV NOx standard was presumed to be 1.0 g/mi
(part of the reason for the high uncontrolled ' particulate
emission factor).
This 1979 analvsis estimated that 1990 urban emissions for
LDDVs and LDDTs would be 84,000-141,00 0 metric tons per year
under the uncontrolled scenario and 22,000-37,000 metric tons
per year under the controlled scenario. Extrapolating that
same methodology to 1995 (i.e., continued diesel penetration
into the in-use fleet and slightly increased total VMT) , urban
emissions would have been projected to be 112,000-190,000
metric tons per year (uncontrolled) and 30,000-50,000 metric
tons per year (controlled).
As shown in Table 2-10, best estimate, urban emissions for
LDDVs and LDDTs for both the relaxed and base scenarios fall
within the previous estimates for the controlled scenario; both
scenarios resulting in emissions well below that for the
previous uncontrolled scenario.* Worst case, urban emissions
under the relaxed scenario are greater than the upper limit for
the previous controlled scenario, but still well below that for
the uncontrolled scenario. Worst case emissions under the base
scenario are essentially equal to the upper limit of the
previous controlled scenario.
Movinq to HDDVs, the Draft P.eaulatorv Analysis
accompanying the heavy-duty diesel particulate NPRM estimated
* • • The great -majority of the difference ' between the estimates
for the relaxed scenario o f this study and the
uncontrolled scenario of the previous study is due to the
difference in projected emission factors. The previous
study projected a uncontrolled particulate emission factor
of 1.0 g/mi while this study has estimated the current
non-trap emission factor to be about 0.27 g/mi. One
reason for this difference in particulate emission factors
is, as already mentioned, that the previous study assumed
a NOx standard of 1.0 g/mi for LDDVs (and its equivalent
for LDDTs) while this study has assumed a 1.5 g/mi NOx
standard for LDDVs and 2.3 g/mi NOx for LDDTs. The
remainder of the difference (approximately 10 percent) is
due to small differences in overall diesel sales
projections and total light-duty VMT in 1995. It should
be noted that the previous study projected nearly twice
the level of LDDV penetration as this study (20 percent
versus 11.5 percent), but only 60 percent of the LDDT
penetration (20 oercent versus the current 33.9 percent).
Thus, the net effect of the two differences is very small.
-------
2-24
1995 urban emissions to be 79,000-97,000 metric tons per vear
(uncontrolled) and 28,200-34,600 metric tons per year
(controlled, 0.25 g/BHP-hr standard in 1986).[12] These 1980
estimates are closer to those in Table 2-10 than the previous
light-duty diesel estimates. For best estimate sales, the
current relaxed-scenario estimate is about equal to the lower
limit of the previous uncontrolled scenario estimate and is
only about 20 percent less than the upper limit of the previous
uncontrolled scenario estimate. The current base-scenario
estimate is only about 5-20 percent higher than the previous
controlled scenario estimate. The results for the worst case
sales scenarios are similar.*
The information presented above is summarized in Table
2-12 (best estimate sales) and Table 2-13 (worst case sales).
The mid-points of the emission ranqes contained in the previous
studies are shown in Table 2-12 (and the upper limits shown
inTable 2-13), because the mid-points represented what was then
EPA's best estimate of diesel penetration and the upper limits
represented what was then EPA's worst case estimate of diesel
penetration.
Both tables are oraanized in a hierarchical fashion, with
those scenarios yielding the highest urban emission estimates
located near the top and those yielding the lowest estimates
near the bottom. Also shown (in parentheses) are the degrees
of emission reduction from the oriainal uncontrolled emission
estimate compared to that provided by the original controlled
emission estimate.
As can. b.e seen from Table. .2.-12, the base. scenario provides
about' Tne"same control as - that- estimatedsvfor essentially -the
same controls 3-4 years ago. On the other hand, while
emissions under the relaxed scenario are 60 percent greater
than those under the base scenario, the relaxed scenario still
provides 74 percent of the original reduction projected for the
trap-based particulate standards.
The difference between the current . relaxed-scenario
estimate and the previous uncontrolled estimate is
primarily due to: 1) the current analysis presumes a
decrease in engine-out HDDE emissions from 0.70 g/BHP-hr
to 0.60 g/BHP-hr in 1988, and 2) vehicular emissions in
the current study are projected to decrease with future
increases in HDDV fuel economy. The difference between
the current base-scenario estimate and the previous
controlled estimate is due to the more detailed fuel
economy and fuel consumption estimates that are used in
this study.
-------
2-25
Table 2-12
Comparison of Current Urban Emission Estimates
to Those of Previous Studies - Best Estimate Sales
Reduction from Original
Uncontrolled Emission
Total 1995 Estimate Relative to
Urban Emissions That Provided By Original
Scenar io (metric tons per year) Controlled Estimate
Original 1979-80 239,000
Analyses (Uncon-
trolled ) - "
Relaxed Scenario 114,000 74%
Intermediate Con- 92,000 88%
trol Scenario*
Base Scenario (HDD 78,000 96%
Control Only)
Base Scenario 71,000 100%
Original 1979-80 71,000 100% (base)
Analyses (Controlled)
Relaxed scenario Cor LDDVs and LDDTs, 0.4
HDDVs.
g/BHP-hr standard for
-------
2-26
Table 2-13
Comparison of Current Urban Emission Estimates
to Those of Previous Studies - Worst-Case Sales
Scenar10
Original 1979-80
Analyses (Uncon-
trolled )
Relaxed Scenario
Intermediate Con-
trol Scenario*
Base Scenario (HDD
Control Only)
Base Scenario
Original 1979-80
Analyses (Con-
trolled )
Total 1995
Urban Emissions
(metric tons per year)
287,000..
15 2 ,000
137,000
120 ,000
106,000
85,000
Reduction from Original
Uncontrolled Emission
Estimate Relative to
That Provided By Original
Controlled Estimate
62%
74%
83%
90%
100% (base)
Relaxed _ sc.enar.io ,/or LDDV.sapd_._.LDD.T.s^, „ 0.. 4. g/.BHP-hr ...standard. ..for
-------
2-27
Two alternate scenarios are also shown in Table 2-12. One
is the base scenario with further controls placed only on HDDVs
(i.e., relaxed scenario for LDDV and LDDTs) . This scenario
still provides nearly the same control (only 4 percent less)
than that originally Drojected for the base-scenario
standards. The other is labelled "Intermediate Control
Scenario," and consists of the relaxed scenario for LDDVs and
LDDTs and an intermediate 0.40 a/BHP-hr standard for HDDVs.
(Intermediate standards were not considered between the
relaxed- and base-scenario standards for LDDVs and LDDTs
because the difference between the two sets of standards is
already very small.) This scenario provides 88 percent of the
reduction originally projected for the trap-based standards.
Thus, based on the information contained in Table 2-12, it is
possible to obtain most, if not all, of the control originally
projected with standards less stringent than the trap-based 0.2
g/mi, 0.26 a/mi and 0.2S g/BHP-hr for LDDVs, LDDTs and HDDVs,
respectively.*
As can be seen from Table 2-13 (worst case diesel sales) ,
the order of the various scenarios does not change
significantly. However, none of the current control scenarios
provides as great a reduction in emissions from the original
controlled scenario for worst case sales when compared to those
which occur for the best case sales (Table 2-12). The base
scenario onlv Drovides R9 percent of the oricinallv projected
control and the relaxed scenario provides only 61 percent of
that control. The two alternate scenarios fall in between.
This difference from the results of Table 2-12 is due primarily
to the increased severity of the worst case diesel penetrations
of this study as compared to those of the previous studies.
It should be remembered that the Dresent analysis assumes
MOx standards of 1.5 and 2.3 g/mi for LDDVs and LDDTs,
respectively. The effect of 1.0 and 1.2 g/mi NOx standard
for LDDVs and LDDTs, respectively, which were assumed in
previous analysis, is addressed in Chapter 10.
-------
2-28
References
1. "Characterization of Particulate Emissions from
In-Use Diesel Vehicles," Gibbs, R., et al., SAE. PaDer No.
801372, October 1980.
2. "A Study of- Exhaust Emissions from Twenty High
Mileaqe Oldsmobile Diesel Passenger Cars," U.S. EPA, OANR, OMS,
ECTD, TE3, March 1980.
'3. "Reaulatorv Analysis of the Light-Duty Diesel
Particulate" Regulations ~'fbr 1982" and Later' Model ' Year
Liqht-Dutv Diesel Vehicles," U.S. EPA, OANR, OMS, ECTD, SDSB,
February 1980.
4. Letter and Supplement from C. L. Hrav, U.S. "PA,
ECTD, to T. Young, Engine Manufacturers' Association, July 19,
1983 .
5. "Trap-Oxidizer Feasibility Study," U.S. EPA, OANR,
OMS, ECTD, SDS3*, March 1982 .
6. (Internal Memo from T. Darlinaton to P. Lorang.
This reference to be constructed at later date.)
7. "Compilation of Air Pollutant Emission Factors:
Highway Mobile Sources," U.S. EPA, OANR, OMS, ECTD, TEB,
EPA-460/3-81-005, March 1981.
8.^ ,"?he Impact of Light-Duty Diesel Particulate
¦Sta'nd-a-.rds-. ."the -Level -of-"-Df£ s e"-l-^ P-ene£fat ionL.i.n. ...th.e:_,Liq:h:t-..D.ut.y
Vehicle and Liaht-Dutv Truck Markets," jack raucett Associates
for U.S. EPA, EPA Contract No. 68-01-6375, January 17, 1983.
9. "U.S. Lona Term Review," Data Resources, Inc.,
Summer 1982.
10. "The Highway Fuel Consumption Model:" Eiqhth
Quarterly Report: Energy and Environmental Analysis, Inc.,
for U.S.* DOE," DOE Contract No. DE-AC01-79PE-70032 , July 1982 .
.11. U.S. Federal Highway Administration data as
contained in "MVMA Motor Vehicle Facts and Figures '82," Motor
Vehicle Manufacturers Association of the U.S., Inc., Public
Affairs Division, 1982.
12. "Draft Regulatory Analysis - Heavy-Dutv Diesel
Particulate Regulations," U.S. EPA, OANR, OMS, ECTD, SDSB,
December 1980.
-------
CHAPTER 3
AIR QUALITY IMPACT AND POPULATION EXPOSURE
I. Introduction
In an attempt to place the impact of the urban emission
estimates of the previous chapter in a better perspective for
assessing both health and welfare impacts, this chapter
estimates the air quality impact of and population exposure to
diesel particulate, emissions in 1995 under the various diesel
sales and control scenarios outlined in Chapter 1. This is
accomplished in four sections.
The first section outlines and uses a methodoloav for
deriving nationwide average diesel particulate emission factors
for urban areas in 1995. These scenario-specific nationwide
average diesel particulate emission factors become the primary
input to the following three sections.
The second section of this chapter uses atmospheric lead
monitoring data as a. surrogate to estimate atmospheric levels
of diesel particulate in 1995 under the various scenarios.
This analysis will provide estimates of ambient diesel
particulate concentrations at one or two particular monitor
locations in a large number of U.S. cities, with basic input to
the model consisting of national fleet-wide averages. These
1995 particulate concentrations are then compared both to each
other and to 1980 levels.
The third section is concerned with a similar analysis of
four types of localized areas which are particularly sensitive
to motor vehicle emissions. These microscale areas include
urban expressways, street canyons and enclosed spaces such as
parking garages and roadway tunnels.'
wh^i^eyrelding ¦¦¦ estima'tes' •' " ''.31;ese 1= particulate
concentrations in particular locations, neither the urban nor
localized air quality analyses address overall population
exposure as oeople move from location to location within an
urban area. This is done in the fourth section of this chapter
by estimating the actual exposure of individuals to these
concentrations; these results can then be used to assess the
cancer risk associated with diesel particulate. The exposure
analysis uses a CO exposure model which was developed by EPA's
Office of Air Quality Planning and Standards (OAQPS) for use in
evaluating alternative CO National Ambient. Air Quality
Standards (NAAQS). Since studies show that the great majority
of CO concentrations in the atmosphere are mobile source
related, it is felt that CO is reasonably representative of
-------
3-2
vehicle pollutant trends and, therefore, can serve as an
acceptable surrogate for diesel oarticulate matter in exposure
modelina. It should be noted that those sources of CO which
are not motor vehicle related, such as indoor sources, are
removed from the model for this analvsis.
A final section is included in support of the theories
behind the air cualitv analysis to be performed in this
chapter. By examining trends in historical emissions versus
ambient concentrations over a period of time, a direct
correlation is demonstrated for both lead and CO; this supports
the rollback theory that emissions can be used to predict
ambient concentrations. Also included in the final section is
a comparison of this chapter's air quality projections to those
contained in a recent EPA study. Ambient diesel particulate
concentrations for 1980 are calculated using the models
contained in both reoorts; upon comparison of results, their
similarity demonstrates support for the lead surroaate model
used here.
It should be remembered that the methodologies described
in Section II through IV utilize the ambient measurement of
other pollutants (lead and CO) to estimate the future year
(1995) concentrations of diesel particulate. None of the
models are based on actual measurements of urban levels of
diesel particulate. As with any indirect analysis method, the
absolute accuracy of this methodology is not well known because
direct measurements of the pollutant of interest in urban areas
cannot be made. (It is difficult to distinguish diesel
oarticulate from other airborne carbonaceous oarticulate.) For
this very reason, these surroaate techniaues are probably the
most suitable approaches currently available for projecting
diesel' oa'r.tTcula'te" conce'htrat ions r'in^ numerous ar eas around the"."
n.s." """ '
It is also imDortant to point out that national-average
input data are used throuqhout this analysis. Such parameters
as the lead content of gasoline, veh icle mix, diesel market
penetration, VMT growth, pollutant dispersion characteristics.,
temperature variations, etc., can vary both regionally and
locally; changes in these parameters would, in turn, have an
effect on the projected diesel particulate concentrations.
Therefore, care should be taken not to overemphasize the
individual diesel particulate concentrations projected for
specific cities (listed later in the chapter). More accurate
estimates for particular cities could be made if the specific
traffic characteristics for that city were used; however, an
ind iv idual c ity-by-c i ty analysis was beyond the scope of this
reDort. Instead, the primary purpose of the modeling efforts
in this chapter is to estimate the effect various levels of
emission control will have on future urban concentrations of
diesel particulate across the nation as a whole.
-------
II. Nationwide Diesel Particulate Emission Factors
The first step in estimating either annual average ambient
particulate levels in U.S. cities or the nationwide average
urban population exposures is to derive fleet-wide urban diesel
particulate emission factors for urban areas for each of the
four scenarios. To do this, the Drocedures outlined in Chapter
2 are repeated to determine the average diesel particulate
emission factor for each vehicle class and scenario as shown in
Table 3-1. (reproduced from Table 2-8. of Chapter 2). The
emission factors for each vehicle cateaory in a particular
scenario are then combined according to the weighting of their
1995 urban VMT, which can be derived from the projected VMT
data in Table 3-1.
'T'able 3-2 aqain shows the particulate emission factors for
each vehicle category/scenario, the derived urban VMT breakdown
for 1980 and 1995, and the fleet-wide, urban particulate
emission factors for each scenario. Also shown is a breakdown
of each vehicle class' contribution to urban emissions under
each scenario.
III. Urban Air Quality Analysis
Since diesel particulate is not easily distinauishable
from other carbonaceous particulate, air quality monitoring
data are not presently available for diesel particulate,
especially under the conditions expected to exist in 1995.
Thus, any method for estimating diesel oarticulate air quality
impacts must use some measurable surrogate in the ambient air
that is directly relatable to automobile emissions. Various
studies in the past have used such substances as lead or CO to
provide a link between vehicle emissions and air quality. Once
this link., is established, , th.en vehicle emissions of the
surroo;ate. substance are -related. to diesel part icula'-t-e
emissions, resulting in an estimate of diesel particulate air
quality impacts.
The fairly strong correlation between ambient
concentrations of lead and carbon monoxide documented in
various Dublished reports [1-4] supports the theorv that both
are representative of mobile source contributions to air
aualitv. Observed concentrations of Pb and CO in Los Anaeles
in 1980 [2] show the two pollutants to exhibit very similar
monthly and seasonal variations; a linear rearession of matched
concentration pairs of the two pollutants yields an r^ value
of 0.7980. Althouah the actual ratio of CO/Pb varies from
study to study because of yearly chanaes in gasoline lead
contents, the coefficient of variation from the mean ratio is
fairly consistent, ranaing from 20 to 26 percent [1,2,4]. It
-------
3-4
Table 3-1
-Weiahted Emission Factors and Proiected vmt
Weighted Emission Factor
(o/mi )
Calendar Year 1980:
All Scenarios
Calendar vear 1995:
Best Estimate Diesel
Sales
Relaxed Scenario 0.0272 0.0760 0.4130 1.6589
Base Scenario 0.0205 0.0711 0.2020 0.8499
Worst-Case Diesel Sales
Relaxed Scenario 0.0606 0.1170 0.8088 1.7025
Base Scenario 0.0460 0.1092 0.3864 0.8753
Projected Nationwide
q
vyn* (jn- miles) : flfli
--l-Q&n-- •—--1,118 208. a 8 -7-V.-8
198 6 " " ' ' " ' - - " ly220"—~-' 2Vf.'0 -4-1.2 "8>.!7 ¦
¦1QQ5 1,537 329.^ 55.2 117.9
Urban Fraction of vM'r: ?Q.4 48. 8 48 . 8 26.9
(all vears)
Urban VMT (10^ miles):
1980 664.1 101.9 IP.9 19.9
1986 724.7 117.6 20.1 23.1
1995 913.0 160.8 26.9 31.7
LDV LD^ VDV/LFDV H^DV
0.0059 0.0074 0.0676 1.913
-------
3-5
Table 3-2
Derivation of National Averaae
Diesel Particulate Emission Factors (a/mi)
Emission Factor (o/mi) •
Urban vmt Best Estimate Worst Case
Breakdown (%) Sales Sales
1980 19 95 1Q 80 Relaxed Pase Relaxed Base
LDV
82.5
80.6
n.0059
0.0272
0.0205
0.0606
0.2460
LDT
12.7
14 .2
' 0 .0074
0.0760
0.0711
0 .1170
0.1092
MDV/LFDV
2.3
2.4
0.0676
0.4132
0.2022
0.8088
0.3864
HHDV
2.5
2.8
1.9130
1.6589
0.8499
1.7025
0.8753
Fleet-Average
Urban-vmt
We iahted
Emission Factor
0.0552
0.0891
0.0554
0.1324
0.0863
Vehicle Class Contribution to Urban Emissions %:
LDV
LD^
MDV/LFDV
UHDV
8.8*
1.7%
2.8%
86.7%
24.6%
12.1%
11.0%
^2.3%
29.9%
19.2%
8.7*
43.2%
36.9%
12.5%
14 . 5%
36 .0%
43.0%
18.0%
10.7%
28.4%
-------
3-6
should be noted that the L.A. study [21 showed a sliqhtly
areater correlation between elemental carbon (EC) and both Pb
and CO; r^ values for EC/Pb and EC/CO were 0.8907 and 0. 8881,
respectively. The above correlations, along with the knowledge
that approximately 90 percent of all fine elemental carbon
(less than 10 um diameter) in the atmosphere is estimated to be
due to mobile sou-rces [5], leads to the conclusion that
elemental carbon could also possibly serve as a surrogate for
diesel particulate in oroj.ecting future ambient air quality.
To date, however, the most commonly used surrogates are lead
and carbon monoxide.
One methodology, which has been used in the past by GM and
EPA, uses lead as a surrogate for diesel particulate.[6,71
This type of analysis uses historical data from urban sites in
the national urban lead monitoring network as an index of
mobile source pollutant levels. An estimate is made of the
fleet's automotive lead emission factor which caused the
observed ambient lead levels, and is compared to the expected
diesel particulate emission factor. Very generally speaking,
if diesel particulate emissions in 1995 are expected to be
twice automobile lead emissions in 1975, for example, then
ambient diesel particulate concentrations in' 1995 can be
exDected to be twice the 1975 ambient lead concentrations. In
this case, 1975 monitorinq data was chosen over more recent
data to avoid, for the most part, the errors associated with
estimatina the leaded/unleaded vehicle mix.
mhe basic mathematical expression of this methodology is:
E(D)1995 s(D) VMT1995
p / n ^ = X7 7 3 y a * u ' y 7 0 y f fDh)
C, .... c (D) i.9,9.5t,. - • -S-(3b.). 1.9.7.5.,i.S.(Pb) x.yMJ1.975..'... .1.19.75 .... •
j'JrJh © IT 0' I * 1-- . ¦ _ . ¦**".. - -¦ _ - , • T- ; '»¦ _ ¦ . «• cxA. . " - I'-*" - "-C-- V- -
C (D)iQg5 = Projected ambient concentration of diesel particulate
(ug/m^")
^ fD)1995 = Fleet-average diesel particulate emission factor
in 1995 (g/mi)
E(?b)]_975 = Fleet-average emission factor for lead in 1975
(a/mi)
S(D) = Dispersion factor for diesel particulate emissions
S(Pb) = Dispersion factor for lead emissions
VMTX = Total urban vehicle miles travelled in year x
C (Pb)1975
= Urban ambient lead concentrations in 1975 (ug/m^)
-------
3-7
A fleet-wide lead emission factor foe 1975 was calculated
using formulas and tables developed in a recent EPA report.f8]
Vehicles from 1956 to 1975 were considered, along with
associated travel fractions and fuel economies. The
calculations accounted for lead emissions from leaded,
unleaded, and misfueled vehicles; for 1975, the national
average lead contents for "leaded" and "unleaded" aasolines
were 1.82 and 0.014 grams/gallon, respectively. Amount of
consumed lead that is emitted with the exhaust was assumed to
be 75 percent for leaded-fueled vehicles and 30 percent for
vehicles designed to use unleaded fuel. Separate emission
factors were calculated for each of five vehicle classes (LDV,
LDTl, LDT2, HDTl, and HDT2), and then were weighted according
to their relative urban VMT's to arrive at a fleet-wide average
lead emission factor for 1975 . ^he final calculated value was
0-1265 grams of elemental lead per vehicle mile travelled.
Dispersion factors for diesel and lead particulate matter
were determined throuah a review of available data and'
literature. It was qenerally concluded in all examined studies
that diesel particles are relatively small in diameter,
compared to particulate matter produced from leaded
gasoline.[8-11]
The majority of the diesel particles are found to fall
within the "accumulation mode" (0.023 to 1.0 um) [10], with the
median diameter between 0.10 and 0.25 um. [9,101 Due to its
small size, diesel particulate disperses similar to a gas;
therefore, S(D) equals 1.0.
Arrivinq at a lead dispersion factor for the model
involved a review of findings from studies using various
methods of analvsis.[ 1-5,12-17] One method of estimating, lead
"disber s'i'on'.i"s„b as£d1uoon~ ,th.e^ i'par.ticle. - -s izeV d istr i_buti-ons of-
lead in both vehicle exhaust and ambient air samples. Before
comparing the two distributions, a "cut-off" diameter of one um
was chosen; Cantwell, et. a1., T14] states that "particles of
less than one micron in diameter...(will) become airborne and
remain suspended for a sianificant length of time."
Huntzicker [4] estimates that approximately 25 percent of al-1
exhausted lead particles are less than one micron in diameter,
while about 64 percent of all airborne particles fall into this
range. Assuming that all particles with diameters less than
one micron will become airborne, a lead dispersion factor of
0.39 was calculated (0.25/0.64). In other words, an estimated
39 percent of all exhausted lead particles will become
airborne, based on a particle size "cut-off" of one micron.
-------
3-8
Another method of estimating S(?b) in the model is to
relate emission and ambient levels of lead and other
vehicle-related pollutants, such as CO and EC (elemental
carbon). Based on calculated 1980 emission factors and ambient
concentrations for Pb and CO, dispersion of lead is estimated
at values between 33 and 44 percent.[1,4] Assuming EC
disperses much like a aas, Cass'[51 ratios of EC/Pb for
"highway signature" versus ambient conditions can be used to
calculate a 57 percent lead dispersion factor.
Other methods of estimating lead dispersion include soil
analyses and actual measurements in enclosed areas. Ward[17]
found that approximately 42 percent of exhausted lead remained
airborne; he accounted for deposited lead in analyses of soil
and vegetation within 250 m of a low-traffic state highway.
Cantwell, et. al.,[l41 reports the results of a study where
vehicles were driven back and forth inside a sealed tunnel;
when exhaust emissions were compared to ambient concentrations
inside the tunnel, it was found that 46 percent of the
exhausted lead particles remained airborne.
Averaging the results of these various studies, one finds
that approximately 43 percent of all exhausted lead particles
become airborne; therefore, a value of 0.43 is used for S(Pb)
in the model eauation.
It should be noted that only lead monitors in areas of no
known large stationary sources of lead were chosen for this
analysis; the majority of the non-automotive sources of lead
emissions reside in a few identifiable areas which have been
excluded from this analysis. For these reasons, it can be
assumed that 100 percent of ambient lead can be attributed to
mobile .sources -(an the -con-text--o-f ¦¦thi-Sf—s-t-udy-)->—de&p-i:te--t-h'e-¦ fact-
that ,¦ nationwide, mobile sources only account for aoproximately
88 percent of .all lead emissions. [ 12]
The nationwide VMT and urban estimates presented in Table
3-1 show urban VMT growth to be 40 Dercent between 1980-95.
Since the Energy and Environmental Analysis projections[18] do
not ao back to 1975 , a second DOE-sponsored study was used to
derive the urban VMT growth between 1975-80, This Oak Ridge
National Laboratory study estimated VMT growth to be 14 percent
between 1975-80. [19] Combining these two figures yields an
overall VMT growth between 1975-95 of 60 percent.
The use of the factors mentioned above results in the
following qeneral equat ion, wh ich can be used to convert the
monitored ambient lead concentrations into estimates of urban
diesel particulate concentrations;
-------
3-9
C(D)'l995 * 0.126°'q"ms 1«TT x 5tTT X U60 * C(pb)1975
mile
or
C(D)i995 = 29.4 E(D)]_995 X C(Pb)]_975
Since each of the four scenarios in this analysis has a
specific average diesel particulate emission factor (E(D))
associated with it, four discrete conversion factors are
produced relating, urban ambient concentrations of lead to
diesel Darticulate levels. As an example, using the fleet-wide
urban diesel particulate emission factor for best estimate
sales and the relaxed scenario from Table 3-2 results in a
factor of 2.62. This means that 1995 urban diesel particulate
concentrations are projected to be 2.52 times larger than 1975
urban lead levels.
Table 3-3 presents the lead-based estimates of diesel
particulate concentrations for each scenario for 28 cities
included in the National Air Surveillance Network (NASN) for
lead in 1975. These monitor stations were selected from a
larger lead data base as they were known to be in areas having
no large stationary sources of lead emissions, and to be above
12 meters in height in order to best represent large scale
average urban lead concentrations. Table 3-4 presents the
range of concentrations of diesel particulate for each scenario
as a function of city size.
T or the best estimate sales and relaxed particulate
standards scenario, the ambient air diesel particulate
:conceh.tfai:t,riph's', "range ""'from' a. low. ,'o'f 12 "ua,/fii3 "'far.the'., c.it.y ' -o'f
Kansas City, Kansas to a high of 7.1 ug/m^ in Los Angeles.
The other scenarios show similar ranees with the highest
projected concentration occurring in the worst case sales,
relaxed standards scenario, as expected (10.5 ug/m^). In
comparing the best estimate sales scenarios it can be seen that
the base scenario will result in an estimated 38 percent
reduction in the 1995 ambient diesel particulate concentrations
compared to the relaxed scenario. This could constitute as
much as a 2.6 ua/m^ reduction (Los Angeles) or as little as a
0.5 ug/m^ reduction (Kansas City, Kansas) in diesel
particulate levels.
This same methodology can also be applied to 1980 diesel
particulate emissions to show the change in estimated ambient
diesel particulates between 1980-95. Using the 1980 diesel
particulate emission factors from Table 3-2 and a VMT growth
-------
3-10
Table 3-3
Ambient Diesel Particulate
Concentrations Based on Lead Surrogate vodel (ua/m V
1995
Best Estimate Sales
Citv
1980
Relaxed
PoDulation Greater Than 1,000,000
Base
Worst Case Sales
Relaxed
Base
Houston
2.5
5.5
3.4
8.1
5.4
Los Anaeles
3 .n
7.1
4.4
10.5
6.8
Mew York
1.2
2.8
1.7
4.1
2.7
Rh iladelph ia
1.5
3 . 5
2.1
5.2
3.4
1.4 " -
3.2
2.0
4.8
3.1
PoDulation Between 500,000
and
1,000,000
Boston
1.1
2.5
1.5
3.6
2.4
Denver
1.1
2 . 5
1.5
3.7
2.5
Kansas Citv
n.9
2.1
1.3
3.1
2.0
Mew Orleans
1.3
2.8
1.7
4.2
2.7
Phoenix
2.5
5.5
3.4
8.1
5.4
Pittsburgh
0.9
2.2
1.4
3.3
2.1
San Dieao
1.3
3.0
1.8
4.4
2.9
St. Louis
1.4
3 .1
1 . 9
4 .6
3.0
Population Between 250 , ono
and
500,000
itlanta
1.2
2.8
1.7
4.1
2.7
3irminaham
1.4
3.2
2. n
4.7
3.1
C inc innat i
0.9
2.1
1.3
3.2
2.0
Jersev Citv
1.2
2.7
1.7
4 . 1
2.6
CoIi7i",s.v.i 1 I.e.-
. -1. 2,.
? .-6,
^ r M - - - w
1.. f,. ..."
-=¦, -3 . 7 ...
..2.5
Oklahoma Citv
1.9
4.4
2.7
6.4
4.2
1.2
2.7
1.7
4.0
2.6
Por tland
0.9
2.1
1.3
.2
2.0
Tucson
0.8
1.9
1.2
2.9
1.9
Yonker s
1.4
3.0
1.9
4.5
3.0
Population Between 100,000
and
250,000
Kansas City, KA
0.7
1.6
1.0
2.4
1.5
0.5
1.2
0 . 8
1.7.
1.1
Mobile
1.2
2 . 6
1.6
'3.7
2.S
New Haven
1.3
3.0
1.9
4 . 5
2.0
Salt Lake City
1.2
2.6
1.6
3.9
2.5
Spokane
0 . 7
1.5
1.0
2.2
1.5
Trenton
1.1
2.4
1.4
3.4
2.2
Waterburv
2.2
4.9
3 .1
7.3
4.8
-------
3-11
Table 3-4
Averaqe Ambient Diesel Particulate
Concentrations by ritv Population fuq/m 3)
1995
City Size Grouping Pest Fstirnate Sales Worst Case Sales
(Pppulat ion) 1980 Relaxed Pase Relaxed Base
Greater than 1. 2-2 .7 2.6-6.2 1. 6-3 .9 3 . 9-9 .2 2 .6-6.0
l ,000 ,ooo
500,000-1,00n,000 0.8-1.8 1.8-4.1 1.2-2.5 2.8-6.0 1.8-3.9
250,000-500,000 0.9-1.5 2.0-3.4 1.3-2.1 3.1-5.1 2.0-3.3
100,000-250,000 0.6-1.6 1.3-3.6 0.7-2.2 1.8-5.4 1.2-3.5
Ranaes are averaqe values dIus and minus one standard deviation.
-------
3-12
rate of 14 percent (as indicated previously for 1975-80), a
conversion factor o.f 1.16 is calculated; this factor,
multiplied by the individual ambient lead concentrations,
yields the 1980 estimates of urban diesel particulate
concentrations found in Tables 3 and 4. As can be seen,
ambient diesel particulate levels in 1995 will increase over
1980 levels under all scenarios. For example, between 1980-95,
diesel particulate concentrations in Los Angeles would increase
by 4.1 ug/m^ under best estimate sales' and the relaxed
scenario, versus 1.4 ug/m3 under best estimate sales and the
base scenario.
Another characteristic difference between the present -5ar
(1980) urban ambient diesel particulate projection and the 1*95
projections are that the proportion of LDDs versus HDDs and
hence their impact on air quality are substantially different.
LDDs produce only 12 percent of total diesel particulate
emissions in 1980 , but between 36 and 61 percent in 1995,
depending on which scenario is chosen. ^or a city such as Los
Angeles, this translates to an increase in urban ambient LDD
particulate concentrations of 2.1 ug/m3 and 2.2 ug/m^ for
base and relaxed standards with best estimate sales,
respectively. Of course, by analogy the imoact of heavy diesel
vehicle cateaories (MDV/LHDV and HHDV) on urban air quality
(1995 versus 1980) is proportionately less than the overall
fleet, though in absolute terms still increasing.
Prior analyses have been performed by EPA on the impact of
diesel oarticulate on urban air quality. The most pertinent
studies are those done for the regulatory analyses for the
light-duty diesel particulate standards and the HDD particulate
standards.[20,211 In both of these regulatory analyses an
identical lead-based air quality projection was made for diesel
oartic-ulate . .-The- only -d infer ences.' between.., .these.. projections,
and the present study would be the diesel particulate and lead
emission factors, lead dispersion factor, and the year for
which the projections were made. The more recent heavy-duty
analysis will be used as the primary comparison to the present
study.
The analysis of the urban air quality impact resulting
from diesel particulates, as calculated in this report, is
aoproximately 45 Dercent lower than the previous analysis based
on a comparison between the midpoint of the previous range of
ambient concentrations and the best estimate relaxed scenario
in this analysis. For example, the urban ambient level of
diesel particulate in this study was estimated to be 7.1
ug/m^ in Los Angeles under the best estimate relaxed scenario
while the corresponding value in the previous analysis for the
uncontrolled fleet was approximately 12.9 ug/m^. The primary
-------
3-13
reason for this difference is the fact that non-traD emission
levels for LDDs are well below those projected three years ago
and that the relaxed-scenario standard for HDDs includes a
slight degree (15 percent) of control.
IV. Microscale Air Quality Analysis
Certain very specific localized areas are known to be
affected by motor vehicle emissions to a greater extent than
urban areas as a whole (and the locations of ' the lead
monitors). Among these localized areas (hereafter called
microscale areas) are urban expressways, street canyons,
roadway tunnels, parking garages and residential oarages. In a
previous effort by EPA designed to evaluate potential hazards
due to unregulated pollutants emitted from motor vehicles, a
set of ambient air dispersion models and model parameters were
developed and validated. [22]
These models, while mathematical in nature, were validated
based on known concentrations of CO in these microscale areas.
As such, these models can be considered reasonably accurate for
the specific geographical and meteorological situations being
examined. However, as the relationship between diesel
particulate and CO emission factors may differ under specific
conditions, these models can only be considered to be aood
estimates when applied to diesel particulate modeling.
However, this approach is perhaps the best assessment available
for localized estimates of diesel particulate concentrations.
"The aforementioned work identified a set of typical and
severe situations for each of the microscale areas, differinq
by vehicle traffic volume, vindspeed, and other factors
.^influencing: amb-ie-n.t -concentrations The .results . of., .the~ear.li-er-
> work.-aHow* caicuia't-ion' o£-: the"-'a;mbient'--a4r'^co,nc-&Wtr a-t'ibn for- -ailV-
of. these microscale areas (in either the typical or severe
situations) based only on the pollutant emission factor. If a
pollutant is assumed to be evenly distributed within the
microscale and is of low short-term reactivity, then the
pollutant emission factor is multiplied by the conversion
factor (one for each microscale area situation) to obtain an
estimate of the ambient concentration at the specific
microscale location.
Table 3-5 presents the various selected microscale areas
and their corresponding conversion factors. These factors
represent the ambient concentrations of any applicable
pollutant (based on above criteria) estimated to occur in each
of these microscale areas for a vehicle emission factor of 1
g/mi. These conversion factors can not be directly applied to
lead emissions due to uneven distribution of lead throughout
the microscale (deposition/dispersion charateristics).
However, CO, which is 100 percent dispersed, would be an
applicable pollutant in this case.
-------
3-14
Table 3-5
Summary of Microscale Situation Concentrations
Microscale
Conversion Factor
S ituat ion (uq/m^ per a/mi)
1. Roadway Tunnel
Typical - Lowry Hill, Minnesota 1,123.
Severe - Baltimore Harbor Tunnel 2,856
2. Street Canvon (sidewalk receDtor)
Typical - 4 lane canvon, 800 vehicles/hr.,
8 mph windspeed
Severe - 6 lane canyon, ?400 vehicles/hr.,
2 mph windspeed
3. On "xpresswav (Wind: 315 dea. relative,
2.2 mph)
Typical - San Antonio 1-410,
Severe - Los Anqeles 1-10,
4. Beside Expressway
100 meters awav-downwind 105
42
282
124
506
-------
3-15
The particular values listed in Table 3-5 for the tvoical
situations were selected to be reasonably representative of the
desired types of areas. The concentrations represented by the
severe situation for each scenario would be expected to occur
only a small percentage (1 percent) of the time on a nationwide
basis. However, in a given specific area, the severe case
could occur much more frequentlv. For example,' the severe
expressway situation used a segment of the Santa Monica freeway
in Los Angeles, which is a 10-lane freeway with a 200,000
vehicle/day traffic count. The windspeed and direction were
typical of this location. while this kind of traffic flow is
severe for most urban expressways in the nation (impossible for
most), it is a definite regular occurrence for this expressway
and other busy large expressways in large metropolitan areas.
Thus, while the severe situation would not be expected to occur
frequently on urban expressways in general, there is a real
possibility of frequent occurrence in the few very busy freeway
segments in large cities.
Table 3-6 presents the results of the microscale area
calculations for the four scenarios. The range of localized
diesel particulate concentrations in Table 3-6 constitute an
estimate of the levels which might be expected in these areas
in 1980 and 1995 . These levels are not to be construed as
anything like average urban levels or average personal
exposures. In fact, the overall oooulation exposure
contributed by these very high, short-term levels is probably
relatively small. However, to the extent that the population
is exposed as they pass through these microscale areas in their
day to day activities, these localized area diesel particulate
concentrations could constitute an impact on their health or
welfare.
Fo-r • -example-,•-•-hiqh • local-i»zed --concentrations of- diesel
'pafr-t: fc;u-I"a~t?eFVi&rrL'an-r-expressway " (r30-7tr""'"ff g/m^' i'li 19*9 5")" may "be'
reflected in reduced short-term visibility or increased
short-term odor which may impact on the health and welfare of
the commuting public. However, current levels of diesel
particulate in an identical situation could already be
approximately 25 ug/m^.
An examination of Table 3-6 shows the wide variety in
ootential localized area concentrations of diesel particulate.
These projected levels range from as low as 2 ug/mJ for a
typical street canyon under the best estimate sales and base
standards scenario to as high as 378 ug/m^ for a severe
roadway tunnel under the worst case sales and relaxed standards
scenario. The lowest levels of this range roughly correspond
to the overall urban area concentrations presented in Table
3-3. This finding is consistent with the fact that some of the
-------
3-16
Table 3-6
Microscale Diesel Particulate Concentrations (uq/m~S
1980
T. Roadway
Tunnel
Tvpical 57
Severe 145
II. Street
Canyon
typical 2
Severe 14
TIT. On ExDresswav
Tvpical fi
Severe 26
iv. Beside
Pxprssswav 5
1995
Best Estimate Sales worst Case Sales
Relaxed Base Relaxed Rase
inn 62 149 97
254 158 378 246
4 2 fi 4
25 16 37 24
11 7 16 11
45 28 67 44
q a 14 9
-------
3-17
fixed site monitors used in the lead ambient monitor network
are sited, in locations such as street canyons (on top of tall
buildings) or near expressways and concentrations in these
localized areas, under typical conditions, may approach the
overall urban area averaqes.
An analysis of the overall differences between the relaxed
and base scenarios yields the same percentage differences as
those found for urban emissions in general in Chapter 2. These
differences can be translated to an increase in ' localized
diesel particulate concentrations of from as low as 2 ug/m3
for a typical street canyon situation to as high as 96 ug/m3
for a severe roadway tunnel situation. Comparing the increases
in 'these projected 1995 localized diesel particulate
concentrations to the concentrations which may be occurrinq now
(1980) results in the observation that, for the severe roadway
tunnel situation, oresent levels of diesel particulate may be
expected to be on the order of 145 ug/m^, which can be
compared to the projection for the best estimate sales relaxed
control scenario in 1995 of 254 ug/m^, or the projection for
the best estimate sales base control scenario of 158 ug/m^.
V. Population Exposure Analysis
A. Tntroduct ion
The population exposure estimates used in this report are
based on a general air pollutant exposure model, called the
NAAOS Exposure Model (MEM), developed by OAOPS for the
evaluation of relative population exposures under alternative
NAAOS [23]. The NEM is an activity pattern model that
simulates a set of population groups called cohorts as they go
..... about,. the irday- to-dav activi ties;. Each......o;f,-,--t.h.e.se„ cohor-ts -.ar e -
a-s.signed-. to- a.r specif tc-'rloca-ti-on^ .type '-dur-ing 'e-ach-.hou;r of' t-ffeP--* •
day. "ach of several specific location types in the urban area
are assigned a particular air quality value based on fixed site
monitor data. The model computes the hourly exposures for each
cohort and then sums these values.over the desired averaging
time to arrive at average population exposures and exposure
distributions. Thus, the model simulates pollutant
concentrations in urban areas by relating these concentrations
to fixed-site monitor levels; in turn, the model simulates the
activities of peoole bv relating the population to a fixed set
of cohorts with defined activity patterns.
For example, a certain fraction of the total urban
oopulation might be assigned to an office worker cohort with a
home-work-home activity Pattern. This cohort would experience
a consistent set of microenvironments, such as home,
transportation, and office, in a normal day's activity. . Each
-------
3-18
of these microenvironments would have an associated pollutant
concentration related to the fixed-site monitor level for the
specific time of day and date. The fixed-site monitor levels
are adjusted to correct for the differences that typically
exist between the monitored locations and the microenvironment
location. These adjustments are general enough to .account for
multiolicative and additive types of correlations between the
monitors and locations.
A unique feature of the model is that it 'separates
concentrations, people, places, and time (all of the important
ingredients of exDOSure) into discrete elements. The
concentrations are broken up into values determined by the
precision of the fixed site monitors (e.g., for CO into whole
integers of ppm) . The people or urban population of an area
are separated into cohorts that are assumed to have specific
activity patterns and related exposures. The places are
separated into a discrete number of areas which are assumed to
have identical pollutant concentrations over a given period of
time. Thus, the definition of places may be influenced by the
type of pollutant studied and its emission sources. Time is
separated into the smallest unit of measure which is desired.
Since this methodoloay was designed to be used with the NAAQS,
which are based, at a minimum, on a 1-hour time period, one
hour is the shortest time period considered by the general
model. Longer averagina times, such as 24 hours or a vear, can
be obtained by calculating the appropriate averages from the
1-hour exposures.
The ceneral NEM approach has been used by OAOPS to develop
specific models for a number of criteria pollutants, such as
CO, SO2, NOt and particulate.[24) These, pollutants have
been studied by applying the specific oollutant .data base .from
--the "appropriate- EPA monitoring - prog-rain and bv - design ing—"t"he
place designations to those most appropriate to the oollutant.
Place or location designations in the NEM are determined as
exposure districts or exposure neighborhoods, depending on
whether the pollutant of interest is a point or dispersed
source of emissions, respectively. The exposure district
approach is more geographical in nature and relies on the fact
that pollutants which are primarily emitted by large point
sources can be adequately characterized by exposure districts
of fairly large areas. In contrast, pollutants with emission
sources which are dispersed throughout an urban area (including
mobile, sources) are best characterized by considering exposure
neighborhoods with common exposure patterns. These
neighborhoods may be spread out in a random fashion throughout
the urban area.
-------
3-1°
^he oeneral MEM modelina aDDroach usina monitorina data in
four cities (Chicago, Los Anaeles, PhiladelDhia, and St. Louis)
was applied to the criteria pollutants- mentioned above
resulting in four averaae exDosures and exposure
distributions. A limited set of 24 total monitors in four
cities was used because of the extensive comDuter time recruired
to run the wm. a rouah nationwide exposure extraoolat ion has
Seen developed hv oaops, which involves relatina each of the
larae urban areas in the countrv to the most similar of the
four modeled cities. T241
Direct measurements of diesel particulate levels in
overall urban areas have not been made because of the
difficulty in .. d ist inau ish ina diesel particulate from other
carbonaceous particulate. The use of a surrogate aDDroach to
relate Diesel Darticulate to some other oollutant which can be
readilv measured in urban areas appears to afford the best
chance of obtainina reasonable estimates of diesel particulate
concentrations, as was the case for urban air Quality estimates
.in the orevious section of this reDort. Of the criteria
Dollutants which have been assessed by daOPS using the MEM
methodoloav, CO apoears to have the most desirable
characteristics as a surrooate for diesel Darticulate.
^tmosDheric rn concentrations are oeneraliv recoanized as beina
essentiallv totally attributable to mobile sources, whereas
other automotive pollutants are also emitted hv stationary
sources. The disDersion characteristics of CO are also verv
similar to those of diesel particulate matter, since diesel
particles are found to be relatively fine and are, therefore,
assumed to disperse essentially like a aas.
The <"0 NEV is desianed to provide an overall estimate of
-.DO,Du-1.3-.t-i-.on.,.j;,e.x.Do.s^ire- v.r-ela-ted- -t-o.»•• -d4.£,fcer-.ent -v a-Vu.es -o-f -the-- fO
MAcAOS:. i Le- the- select ion- of- CO -and- 't-h-e -ME-V• • me-thodol-oav - ''i;s
perhaps the best basis for a mobile source assessment of
copulation exposure, a number of modifications to the NEV CO
•assessment are necessary and/or desirable in order to Drovide
-.he best estimate of diesel particulate exposure.
One modification to the standard M^V methodoloav involves
the removal of all indoor sources of CO, such as cas stoves,
from the air aualitv inventories. mhis chance allows for a
more Drecise estimate of automotive sources, particularly
indoors, where the contribution of outdoor emissions is still
oresent without the con^oundina presence of indoor sources.
This is the most important modificaton to the model in order to
allow a reasonable estimate of automotive exposure to <"0 an^ ,
via an approDriate conversion, to diesel Darticulate.
-------
3-20
Other desirable modifications to the • nfm, which are
planned for the.near future, include an effort to correct the
model for a suspected underestimation of mobile source
microscale area contributions, and an effort to desian a
national extrapolation procedure exDresslv for mobile sources.
A modified version of the NEM methodoloav is expected to
produce sliabtlv hiaher exposure levels than the oriainal
version; however, it is felt that t*e current version is
adeauate for the ourooses o^ this document.
The M^vt-hased exDosure estimation methodoloav used in this
reDort orovides both an averaoe ro exposure and CO exposure
distribution for the four cities in the data base. The averaae
CO exposure results are used to develop the nationwide exposure
estimates for diesel particulate in 19 9 S. ^he exposure
distribution form of the methodoloav is not essential for the
uses of this report and will not be presented here. "owever,
for the sake of completeness and because the distributions do
present information on exposure ranaes of diesel particulate
which mav be interestina in olacina the exposures in
oersDective, the exposure distributions for diesel particulate
will he presented later in this chapter.
w. Past Fxposure Pfforts
Before discussina the details of the diesel particulate
exposure estimate derived in this report, it mav be useful, at
this point- to compare the VTFM methodoloav to the aeneral
methodoloaies used in previous EPA assessments of mobile source
pollutant exposures. Two different assessments have been used
in the oast: 1) one based on a methodoloav by °edco for a
previous F.°A diesel particulate risk assessment and, 2) one
based on., a., methodoloav bv" -'SRI* for. an E'0A . benzene risk
assessment.
The °edco exposure assessment used an *ir Pualitv Display
Modelina (AODM) approach wherein the urban area to be modelled
was broken up into a set of aeoaraohical arids where the arid
population and qrid pollutant concentrations were combined intn
an exposure for each arid.T2?1 ^he Pedco approach used T<:p to
derive the oriainal predicted concentrations of particulate and
adjusted these predictions based on t<;d monitor ^levels,
vowever, since the emission pattern and ambient distribution of
TSP mav be verv different from diesel particulate due to the
larae contribution of non-mobile sources to TSP emissions, this
is and was thouaht to be a source of possible error in the
Pedco assessment. Also, no effort was made to simulate
different activitv patterns as was done bv the mem model.
Dedco approach was applied to onlv one citv, Kansas Citv, and
this sinale result was extrapolated nationwide. ^he Pedco
-------
3-21
approach was verv valuable at the time of its development as a
coarse, but usable, first estimate of the Dooulation exoosure
to diesel particulate; however, the Dresent MEM model is felt
to be a more detailed, Drecise aDproach and probablv,
therefore, vields a more accurate result. It is not Dossible
to directly compare the results of these two approaches (NEM
and Pedco) because' of the different emission factors used,
wowever, -it - is estimated that the current NEM assessment
results in exposures which are rouahly a factor of. 10 hiaher
than those in the Pedco report. At the time of the preparation
of the °edco report, and its subsequent use in the fpa ' s
preliminary risk assessment for diesels, it was thouaht that
the -Pedco assessment miaht be low, primarily because Kansas
City was not thouaht to be the most typical urban area with
resoect to automobile emissions. Thus, while this factor is
sianificant, it is not unexpected or unusual in our view, but
rather indicates that the current NEM aDproach represents a
more correct and Drecise exposure assessment for mobile sources.
^he SRI modeling aooroach used for the ^PA benzene risk
assessment estimated the mobile source contribution using an
area wide disoersion model called the ^anna-Gilford disDersion
model.f?61 This aDDroach is very simplistic, reauirina onlv an
estimate of an urban area's vehicle reaistrations, vmt, area
size, averaqe annual wind soeed, and vehicle emissions. A
relativelv limited examination of population activitv Datterns
was used bv SRI to estimate the influence of the manv different
sources of benzene, but onlv the area-wide dispersion-based
averaaes were used for the automobile contributions.
Comparison of the exposures calculated bv the SRI benzene
assessment to the NEM exoosures results in the findina that the
NEM based exposures are rouahlv a factor of five hiaher than
• the--. SRI- -estimates--for' a ¦¦ comparable; e^dss i-on- factor .'•••The" SRI— •••
:: Veoor t*" sfates' "th-at 'the ' auto'mobil"ev con'tr ihuVion* to' the " benzene'
assessment are nrobablv underestimated because of the fact that
the area-wide model used mav not adeduatelv reflect the hiah
localized concentrations believed to occur around
automobile-use areas. (261 The relatively close aareement
between the SRI and NEM exoosure assessments and the intuitive
loaic discussed earlier on whv the NEM should be hiaher leads
to the conclusion the NEM model used in this reoort is probably
the most valid apDroach currentIv available.
C. Averace Nationwide Diesel Particulate Exoosures
^able 3-7 presents the NEM hased averaae CO concentrations
for the four cities used in NEM oroaram. The averaae CO
exoosure concentrations for each citv in '"able 3-7 are combined
in order to Drovide the desired nationwide averaae exposure. A
simple method to use, and the one used bv both the CO NEM and
-------
3-22
Table 3-7
Averaae ^otal CO Fxoosure in Four Cities
C i tv
Ch icaqo
Los Anqeles
Philadelphia
St. Louis
Overall
CO Dom
Population
of Citv As
(Annual ava.) Used in CO NF.M
1.8 ppm
3.0
1.3
2.0
2.12
2,363,014
7,716,895
2,933,790
1,221,461
Associated Total
Urban PoDulation
In Cities 200,000
1970
3 8,894,365
2^,339,249
10,553,523
17,350,712
93,137,849
-------
3-23
this report, qroups each of the larae urban areas in the
countrv (populations areater than 200,000) with one of the four
modeled cities ' accordina to overall urban characteristics,
includina poDulations, vehicle-use Datterns, etc.[24] Under
this nationwide extrapolation, a larae Dortion of the
ooDulation (43 percent) is grouped under Chicaao. ¦ while this
nationwide extraoolation seems reasonable and valid as an
estimate, it is most likely the least precise part of this
assessment. Thus, it is one of the areas that ECTD is
continuina to investiaate as Dart of the onaoina mobile source
exposure estimate oroiect. c'C^D intends to use a larae bank of
CO monitor data, perhaos from the E^A SAPOAD data base,
selected with a view toward mobile source contributions, to
orovide an extraoolation to the nationwide situation.
^he national DODulation (Column 4) in Table 3-7, as
mentioned previously, counts only persons in urban areas with
DODulations areater than ?no,nno. while it is desirable to
extend this analysis to the pooulation in all urhan areas,
includina those with pooulations less than 200,000, the.
likelihood that the exoosures in smaller urban areas would be
lower than anv of the four vf.m cities Drevents this from beina
oreciselv done. Therefore, we have limited our analysis to the
DODulations in the larae urban areas without considerina the
exoosures of rural or small urban areas.
The aforementioned nationwide extraoolation to the N^M-CO
averaae output results in the calculation of an overall averaae
nationwide concentration (hased on CO) of aDDroximatelv 2.1
Dom. This total adjusted national averaae (2.1 oDm) can then
be manioulated into a diesel Darticulate national averaae by
ratioina CO and diesel particulate emission factors, and then
m-u-Lt i oi-v..i-n®. •• the • *.-r e su-lt -r-b-y - r2..- -12 - doit. * •<•.••• T-he national - averaae GO--'
:eT.i'ss i"6n~ "'facto'ir- for" 19 7 8 "-'(the'-s'ame^veac "a"s" ' fh-'e "C.O ' 'd'a't'a'
base) is estimated to be *7.1 a/mi.f2"71 *Jowever, since future
vear umt is expected to increase by about 45 percent, the
diesel Darticulate emission factor should be adjusted uoward bv
a factor of 1.45 for 199s!. [181 The 199S Hiesel Darticulate
emission factors are the same as those used in the air aualitv
analyses (see Table 3-2).
^able 3-8 oresen.ts national averaae diesel Darticulate
concentrations for each of the four main scenarios. These
values will be used in ChaDter 5 to estimate the diesel
particulate cancer risk.
The total DODulation exDosure (from "able 3-8) for the
best estimate sales and relaxed standards scenario is estimated
to be fil cercent hiaher than the exoosures calculated for the
cor respondina base case standards. However, seDaratinq the
-------
3-24
Table 3-8
Total National Diesel Particulate Exposure in 1^95
Annual Averaoe Diesel Particulate
Exposure (ua/m^)
Best Estimate
Sales
Worst Case
Sales
Relaxed
Rase
Relaxed
Base
LDV
1.23
0 .92
2.73
2.07
LDT
0.60
0 .64
0.92
0.R7
MDV/LHDV
0. 54
0.27
1.07
0. S2
HHDV
2.61
1. 34
2.66
1.37
Total
4.98
3 .09
7.40
4 .82
-------
3-25
liaht- and heavy-duty components of these exposures, individual
contributions to this increase in exDosure with relaxed
standards are 14 percent for LDVs (LDVs and LDTs) and 86
Dercent for HDVs (FDV/LHDV and HHDV). These data can be
interDreted as meaninq that the bulk of the increase in
exDosure with best estimate sales and relaxed standards can he
attributed to HDVs with a comDarativelv small contribution from
LDVs.
If the worst case sales Droiections are used to derive
relationshiDS hetween the relaxed and base scenarios above,
then the overall poDulation exDosure is increased 54 Dercent
with ,LDD's contributing 28 percent of the increase, and HDVs 27
Dercent.
n. Pxsosurg Distribution for Diesel Particulate
In addition to the national averaae exposure derived in
the orevioas section, this mobile source model can be used to
identifv a distribution of exDosures amonq discrete
concentration ranaes. A maniDulation of this information in a
manner analaaous to the Drevious discussed averaae exoosure can
be used to Drovide a national averaae diesel particulate
exDosure distribution. For convenience this distribution is
Dresented in Table 3-9 as a ranoe of percentaaes for the two
cities with the lowest and hiahest exDosures versus the diesel
oarticulate concentration ranae (deDendent on the scenario).
T'he exposure distributions included in ^able 3-9 can be
used as a relative illustration of how the total exposure is
broken down into concentration ranaes. while this data is not
used further in this analvsis, in the event that a non-linear
¦r i-sk -model is used i-n the . ¦ future- to west ima-te diese-l ¦¦ -cancer
r isk-, data- such as: those in ^able 3-9 wi-11 • be " necessary for
estimatina the cancer risk to individuals.
A brief inspection of the data in ^able 3-9 show that
while there are distinct differences between each citv's
exDosure distribution, there is the common feature wherein most
of the diesel particulate exposures (9F-99 Dercent) are in the
lowest ranae. The corresDondina ranaes of diesel Darticulate
exposure are from 0-10 to 0-21 ua/m-3 deDendinq on scenario.
Tf future interest is aenerated on this kind of exposure index,
a wav to further break out the exDosures within this lowest
ranae-will be necessarv and this effort is underway as part of
the onaoina ECTD Droiect on develoDina a mobile source exposure
assessment methodoloav.
-------
3-26
Table 3-9
Diesel Particulate Sxoosure Distribution
Diesel Particulate (ua/m~$)
Best Estimate Sales worst Case Sales
Ranae of
Pooulation ExDOsed %
Relaxed
117-
106-117
94-T06
82-94
70-82
59-70
47-59
35-47
28-35
21-28
16-21
0-16
Base
73-
66-73
58-66
51-58
44-51
36-44
29-36
22-29
17-22
13-17
10-13
0-10
Relaxed
174-
122-139
105-122
87-105
70-87
52-70
42-52
31-42
21-31
0-21
114-
174-174 102-114
139-157 91-102
79-91
68-79
57-68
45-57
34-45
27-34
20-27
16-20
0-16
Hiah
Low
Base Los Anaeles Philadelphia
0.000654
0.000345
0.000941
0,006804
0.008965
n,n 36916
0.066520
0.185011
0.552363
1.292952
2.825991
95.022026
0.000250
0.000000
0.000263
0.001121
0.000555
0.007867
0.009422
0.020867
0.084505
0.194798
0.414451
99.265896
-------
3-27
VI. Support for Air Quality Analysis Used in This Chapter
For purposes of validation, the followino sections will
lend support to the basic theories behind the air duality
analvsis performed .in this chapter. The first section contains
a review of available historical data on mobile source
emissions and ambient concentrations of both lead and carbon
monoxide; the demonstrated similarity between trends in
emissions and ambient concentrations offers support for the use
of the "rollback" theory in orojectinq future ambient levels of
both lead and CO. The second section contains a comparison of
the air quality model described earlier in this chapter to
other lead surroaate work contained in a recent "PA studv. Tn
this section, both models are used to calculate 1980 ambient ¦¦
diesel particulate concentrations for four U.S. cities; the
similarity in results obtained with the different models lend
support to their validity.
A. Validations of Rollback ^heorv as Applied to Lead and
Carbon Monoxide
The theory behind the air aualitv models previously
described is based primarily on the simple "rollback" modelina
technique. The rollback model assumes t^at a proportional
relationship exists between emissions and ambient
concentrations, and uses this proportionality to project values
for future years. Because lead and CO were used as surrooates
for diesel particulate matter in this chapter, it is of
interest to investiaate the ability of rollback models to
predict future concentrations of lead and CO based on emission
factors.
- . In..a- rece-nt-c"OA reoort- f 121 , • data-on--the- lead ¦ consumed -in
aasoline"and on"'ambient urban lead" concentrations for the -year's" *
1975 throuah 1979 were examined. A verv strona correlation was
reported, with an r^ value of 0.99. A graph of consumed lead
versus ambient concentrations is presented in Figure VI.
Because the relationship between lead consumed in gasoline is
linearly proportional to lead emitted with exhaust, it is
concluded that the correlation depicted in Fiaure 3-1 can be
translated into a direct relationship between lead emissions
and ambient urban lead concentrations. Evidence of this
relationship supports the use of the rollback theory in
predictina future ambient lead concentrations from historical
data on lead.
Tn a second EPA reoort [281, co emission factors for the
years 1970-80 (estimated usinq FPA's MOBi" LE - 2 computer model)
were examined aaainst actual ambient air aualitv measurements
taken durinq the same period. Fiaure 3-2 is a logarithmic plot
-------
I-
I
i
1
o
(ft
<
a
200
iao
160
140
120
Q
m
2
I 100
z
o
u
o
w 80
60
40
20
3-28
Figure 3-1
200
ISO
180
140
120
100
80.
10
40
20
T
AMtllNT UAD CONCIKTtUTlON
UAO OOMSUMCD IN SAiOUNI
1.20
1" g
s
I
Sfi
1.00 £
e.to
0.80
s
e
S
o
c
0.70 £
D
0.80
0.50
0.40
0.30
!
_L
1375 1376 1377 1378 1979 1980 1331* 1332*
CALENDAR YEAR
Lead consumed in gasoline (Du Pont, 19C2) and ambient lead con-
centrations, 1975-1902. INunt and Ncligan, 1982).
-------
12
1 0
08
06
04
0 2
0
02
04
05
08
1 0
t 2
I U
; s
, 1 9
, 20
. 22
. 24
. 2 5
3-29
Figure 3-2
s
70.71 72.73 7 '4 _ 7 3 7 S _ 7 7 • 78.79
7 1.72 "J 3 . 7 V| 7 S . 7 5 7 7 . 7 3 * = .20
'isri
S • e o « d Ki.gh 8"
how r o v » r o g • CO,
oL L «onUor i ,
• OlV ¦ d
F • d • r o I.
crscudurt
' f I • • I nl Ml oni
-------
1-30
of the chanaes from vear-to-year in both CO emission factors
and ambient CO measurements. The plot depicts a oeneral
correlation between the reductions in both Darameters;
therefore, it is aaain concluded that the rollback modelina
techniaue is aDDlicahle to the projection of future CO
concentrations based on historical relationships between
emissions and ambient air aualitv.
These findinas are strona indications that both lead and
CO emissions are reDresentative of trends in ambient
concentration levels. This observation, couoled with earler
documentation of the correlation between lead and CO
concentrations (Section III), leads to the conclusion that
either of the two are fair candidates for the surroaate
pollutant used in this chapter's rollback model for estimating
ambient diesel particulate concentrations.
C. Comparison of Lead Surrogate Models
This section compares the air aualitv model described in
Section III of this chapter to other rollback modelinq
contained in a recent FPA study. The basic differences between
the models are discussed, and calculations are made for four
n.S. cities usina both models. A comparison of the results
supports the validity of the nationwide model developed in this
chapter.
In a recent studv performed bv EPA1s Office of Research
and Development (ORD) in response to Section 214 of the Clean
Air act, lead was used as a surroaate in predictina ambient
automotive particulate concentrations for several cities, r11
Like the lea^ surroaate model developed earlier in this
*ch apte.r, 'ORD's.' rno dels ..make ..us'e "of. the . r o 11 b a c k t he or;/'; ho we v e r ,.'
the models differ in that the ORD studv examined automotive
particulate concentrations as a whole, as opposed to just
diesel Particulate. Also, the CRD studv used a baseline vear
of 1977 in its projections, while the model developed earlier
in this chapter is based on 1975 ambient lead data.
Models developed in the ORD study [11 use a ratio of
automotive particulate mass to lead mass in determinina a lead
emission factor for the baseline vear (1977); this national
averaae ratio for 1977 ranaes between 5:1 and 8:1, and is based
on emission data taken from ambient air mon'itorina sites.
Usina a 1977 fleet-averaae automotive particulate emission
factor of 0.24 a/mi, the resulting lead emission factors for
1^77 range between 0.030 and 0.048 a/mi. Because these
emission factors are based on ambient data, as opposed to
vehicle exhaust emissions, a lead dispersion factor is not
necessary. (The model developed earlier in this chapter uses
-------
3-n
an exhausted lead emission factor of 0.12*5 a/mi and a lead
dispersion factor of n.43; this translates into actual
dispersed lead emissions of 0.054 a/mi for baseline vear 1975.)
Ambient diesel oarticulate concentrations for four
cities--St. Louis,' Los Anaeles, Mew York, and Kansas flitv
(MO)--were calculated for 1980 usina a modified version of the
model developed in the ORD studv. The model has the following
basic form:
E(D)sn VM,f?o
C(D)Rn = — x Li x c f Phi _
8n ?(°M77 vmt77 77
The 1977 lead emission factors are the same as those used
in the ORD report (0.030 and 0.0*8 a/mi); the 1977 ambient lead
concentrations used are also those reDorted in the ORD
study. [1] The remainina oararaeters are those derived earlier
in this chaDter. A 1QR0 fleet-averaae diesel particulate
emission factor of 0.O5S2 a/mi was used in the model eauation
(from Table 3-2). The vmt arowth rate between 1977 and 1980
was estimated at 3.4 percentfl91; therefore, a factor of 1.034
was used as the V^t ratio in the equation. Bv substitutina the
above constants into the model equation, the 1980 ambient
diesel particulate concentration can be estimated by a ranoe of
values; the lower and upper boundaries of the range are
reDresented by multiolvina the 1977 ambient lead concentration
for each city by factors of 1.19 and 1.90, respectivelv.
The' above calculations were performed for the four
oreviouslv mentioned cities; Table 3-10 comoares these values
to those .listed in Table 3-3 for each the cities. For three
of the four cities, the values Dreviouslv calculated usina the
.model <3eve-looed- in - this chaDter—-fall- well wi-thin , the taaoes-
"calculated" w"i"t'h the modified' ORD" mo^el. "The co'ncentrat ion for1
the fourth citv (Kansas f*itv, MO) falls just sliahtlv below the
newlv calculated ranae; this could be due to different base
monitors beina used in the two studies.
Overall, the comparison of results demonstrates that,
althouah the basic inout to the models may differ in form, the
final concentrations arrived at are fairly consistent. This
similarity in results, alona with other documented support for
the theories behind the surrogate approach, lends validity to
the air aualitv model developed earlier in this chapter.
-------
3-32
Table 3-10
City
Comparison of Ambient Concentrations
Calculated With Two Different Models
St. Louis
Los Angeles
Mew York Citv
Kansas Citv, MO
1977 Ambient
Lead Concentration
(uq/m3)
0.89
1.8-4.2
0 . 67
0.9-1.4
Calculated 1980 Ambient
Diesel Particulate
Concentrations (uq/m3)
Modified Values from
ORD Model Table 3-3
1.1-1.7
2.1-8.0
n.8-1.3
1.1-2.7
1.4
3.0
1.2
0.9
-------
References - cont'd
13. ' "Characterization of Particulate Matter in Vehicle
Exhaust," Habibi, K. , Environmental Science and Technoloav,
7:223-234, 1973.
14. "Control of Particulate Lead Emissions from
Automobiles," Cantwell, E., et. al., SAE Paper 720672, May 1972.
15. "Composition, . Size, and Control of Automotive
Exhaust Particulates," Ter Haar, G., et. al., JAPCA, 22:3946,
1972 .
'16. "Nature of Lead in Automohile Exhaust Gas,"
Hirschler, D., and Gilbert, L., Architecture and Environmental
Health, 9 : 297-313 , l^M.
17. "Lead in Soil and Veaetation Alona a New Zealand
State Highway with Low Traffic Volume," ward, N., et. al.,
Environmental Pollution, 9:243-251, 1975.
18. "The Highway Euel Consumption Model: Fiahth
Ouarterlv Peoort," Fnerav and Environmental Analysis, Inc. for
U.S. DOE, DOE Contract No. DE-ACOl-79PE-70 0 3 2 , July 1982 .
19. "Transoortat ion Enerav Conservation Data Book", Kulo
g. et.al., ORNL Publication 5765-Edition *, 1982.
20. "Peaulatorv Analysis of the Liaht-Duty Diesel
Particulate "eaulations for 1982 and Later Model Year
Liaht-Dutv Diesel vehicles," U.S. EPA, OANR, OMSAPC, ECTD,
SDSB, February 1980.
' "21. "*"Dra„'ft' Peaulatorv "A'rialvsis " Uea'vv-Dutv ""Diesel"
Particulate Reaulat ions," U.S. FPA",' OANR, OMSAPC, ECTD, SDSB,
December l^SO.
?2. "Estimatina Mobile Source Pollutants in Microscale
Exoosure Situations," Tnqalls, M. , EPA-60/3 -80-0 21 , July 1981.
23. "A General Model for Estimatina PxDosure Associated
with Alternative NAAQS," Biller, W., et al., June 1981.
24. "The NAAOS Exoosure Model (NEM) Aoolied to Carbon
Monoxide," Johnson, T., et al., Draft FPA-OAOPS Report,
December 1982.
2?. "Air Oualitv Assessment of Particulate Emissions
from Diesel-Powered Vehicles," Pedco Environmental, Inc., March
1978 .
26. "Assessment of Human FxDosure to . Atmosoheric
Benzene," Mara, S., and S. Lee, EPA Reoort No. 450/3-78031.
-------
Refe rences
1. "Study of particulate Emissions . From Motor
Vehicles,? draft, U.S. EPA, ESRL, ORD, Vol. 2, ADpendix C,
March 1983.
2. "The Relationship between Concentration of
Traffic-Related Pollutants and Meterology at a Los Angeles
Site," witz, S., et. al., JAPCA, 32:643-M5, June 1982.
3. "Motor Vehicle Fmissions and Atmospheric Lead
Concentrations in the Los Anaeles Area," woqaan, v.; et. al.,
JAPCA, 28 : 1200-1205, December 1978.
4. "Material Balance for Automobile-Emitted Lead in Los
Anael'es Basin," Huntzicker, J., et. al., Environmental Science
and Technoloav, 9:448-457, Mav 1975.
5. "Emissions and Air Oualitv Relationships for
^tmosDheric Carbon Particles in Los &noeles," Cass, G. , et.
al. , Proceedings of an International Symposium on Particulate
Carbon: &tmosDheric Life Cvcle, Plenum Press (N.Y.c.), 1982,
dd. 207-225.
*. "An Tnvestination of Future Ambient Diesel
Particulate Levels Occurina in Larqe ~cale Urban Areas,"
"eiser, D., EPA-AA-SDSB-79-30, November 197Q.
7. "Estimates of Diesel Particulate Concentration in
Four Urban Areas Under Different vox rmission Scenarios,"
chock, David °., et. al., General Motors Research Laboratories,
SAE °3Der Mo. 840415, February 27, 1984.
P. "Size-Specific ^otal Particulate Emission Factors
fpr_.yobj.le _Sources.,."v. Bruetsch, R. ,. LL. S..v„ E.PA OA.NR;_, v -0 MS ECT.D.,
JTS'S",; Jana.ar v .19.84.. (d r a ft) . • „. ;; - i*..
9. "Particle Size Variation in Diesel Car Exhaust,"
Groblicki, P., et. al., SAE Paoer 790421, March 1979.
10. "The Effect of Operating Conditions on the Effluent
of a Wall-Flow Monolith Particulate Trap," vacDonald, J.S., SAE
Paoer 831711, November 1983.
11. "Diesel Particulate Emissions," Bradow, R., U.S.
E°A, ESRL, Bulletin of Mew York Academy of Medicine, Vol.
5^:797-811, November-December 1980.
12. "Lead Criteria Document," Carev, °., Chapter 5:
Sources and ^missions, Februarv 1983, p. 5-13.
-------
References - cont'd
27. "MOBILE2.5 Emission Factor Prooram" Unpublished
numbers, U.S. EPA, OAMR, OMS, ECTD.
28. "Ambient Versus Predicted Carbon Monoxide Levels,"
Wolcott, M., u.5. pPA, OMS, ECTD, TER, ReDort NI0.
EPA-AA-TEP-FF-^2-4, SeDtember 1982.
-------
4-2
Visibility is defined as the areatest distance it is
possible to see a prominent dark object against the sky at the
horizon. T2] Middleton's Lawf21 relates contrast and light
intensitv; both are reduced eaually at horizontal views of
objects against the horizon. Koschmieder's Lawf21 aoes a step
further and relates visual ranae to the extinction
coefficient. The typical observer can detect an object with 2
Dercent contrast acainst the backaround.T21 The mathematical
formula describina Koschmieder's Law is:
L = ^91
v . b
ext
where Lv is the visual ranae, 3.91 is ln(.02) and boxt is
the total extinction coefficient.
Koschmieder1s Law can be derived from the Beer-Lambert
Law, which describes the more fundamental effect of the
extinction coefficient (bext) on liaht intensitv. The
Beer-Lambert Law is:
I = IQe -bextL
where:
IQ = light intensitv at the object being observed, and
I = light intensitv at a distance L from the object.
Described very simplisticallv, Koschmieder ' s Law simplv
states that objects become invisible when the ratio of I to
I0 becomes 0.02. Substitutina 0.02 for I/I0 into the
Reer-L'amber t * Law and-solving for -L yields Koschmieder's Law. ¦¦•••¦»
¦ -r. .. .. . .
a.s can be seen, the most important parameter in all of
these laws is the extinction coefficient (^ext^ • This
coefficient is the sum of four components:
1. scatterina bv oas molecules, bRq;
2. absorption by gas molecules, baa;
3. scattering by particles, bSD;
4. absorption bv oarticles, baD.
Diesel particulate impacts directly on the latter two
processes. In order to aain insiaht into the relative role of
diesel particulate in liaht attenuation, each of t^e four
components of the extinction coefficient should be examined.[31
-------
CHAPTER 4
VISIBILITY ASSESSMENT
I. Introduction
The most obvious effect of diesel particulate, esDecially
in urban areas, is reduced visibility. In order to study this
effect, there must be a means of measuring the relationship
between diesel particulate and visibility levels. a method is
needed to determine the visibility impact from a specific level
of diesel particulate.
This chapter develops and applies a method for measuring
the change in visibility caused by an increase in diesel
particulate concentration. This is done on a city-by-citv
basis, yielding visibility levels for four regulatory scenarios*.
No attempt is made in this study to estimate the dollar
value of the projected changes in visibility. Such an analysis
is beyond the scope of this report. ^or an economic analysis
of the benefits of visibility improvements, the reader is
referred to a recent study performed under contract to EPA[1]
and other studies in the literature.
II. Modeling Visibility
There is no absolutely preferred method for modeling
visibility; different measuring techniques are appropriate for
various times and locations. The three types of
visibility-related indices are: 1) direct measures of human
perception, 2) measures of liaht intensities, and 3) measures
of visual properties of air. Using observers to measure
airport visual ranges is an example of direct human perceDtion
-me-asu-rement i --T-h is is a, sub ject ive- method wh ich -fcs -d-i-f f-fccui't - to
•'•convert- to • ob jective '"physical- parameters". fftere"'" exists *"no
correlation between the methods of measuring direct human
perception and diesel particulate. In measurina light
intensities, the relationship between perceived contrast and
measured physical contrast is also a subjective and complex
one. (Contrast, combined color and brightness scales, and
blue-red luminous ratios are examples of measures of
intensities.) Because both of the above methods appear to be
inadequate for relating the effect of particulate on
visibility, the third method is, by necessity, the method of
choice. The measuring of visual properties of air and airborne
particles can directly relate the particulate matter from
diesels to a reduction in visibility.
-------
4-4
Figure 4-1 UJ
loooa
0
b-icco
ICQ in
=¦10
0.1
Calculated scattering efficiency for. a log nonnal
aerosol" size disrribution, geometric standard
deviation equal to 2, as a function of geometric
rrass mean radius. M is the fine particle mass
concentration, bSp is the scattering coefficient,
. and rg^ is the geometric ~ass mean radius. For
reference, the right hand axis is the mass concen-
tration required to give a visual range of 40 Sen.
-------
A.
C-as Scatter
The extinction coefficient due to scatterina bv aas
molecules in the free atmosDhere at sea level, known as
Ravleiah scatterina, is rouahlv 1.5 x in~5 meters"^-;
values of the extinction coefficient within a few percent of
this have actually been measured.f21 If.liqht dearadation were
due solelv to aas molecule scatterina, then the visibility
would be aporoximatelv 260 kilometers bv the ^oschmieder
formula. Thus, scatterina bv qas molecules does not plav a
major role in observed visibility deqradation.
B. ^as Absorption
Mitroaen dioxide (^02) is the only absorbina aaseous
soecie oresent in hiah enouoh concentrations to have a
sianificant effect on liaht absomtion. In optics, NO2 seems
to be important onlv in olumes, not in the case of a well-mixed
laver..f21 Therefore, absorotion bv aas molecules can be
discounted in calculatina the total extinction coefficient.
c« ^article Scatter
Particles with diameters in the range of 0,1 to l.o
micrometer scatter liaht with the areatest effectiveness.
Diesel oarticulate falls into this ranae. riaure 4-1 shows the
ratio of mass to scatter coefficient as a function of particle
radius. The duration of this scatterina effect is prolonaed
for this size ranae, since such aerosols aenerallv do not
settle out bv aravitv and are not removed efficiently from the
atmosDhere except bv incorooration into clouds and subseauent
rra ino._ut._ . 5_t.udJ._es...show that..they :jr,av„.j?ejr s ist^. lq_ ,.tJ^e_.atjnosofeer.e,
^f0^'y'Cr.a 1...daiys. fX\, . : . ; .-
D. ^article Absorotion
The most imDortant contributor to particle absomtion is
araDhite carbon; any sub-micron particles with a hiah carbon
content will have a sianificant effect on visibility. Diesel
oarticulate, with its 65-30 Dercent carbon content, falls into
this cateaorv.f51
ITT. visibility Fauations
Once all the factors involved are known, the comoutation
of visibility levels due to a chanae in diesel particulate
level is straiahtforward. Accordina to the Koschmieder
formula, the visual ranae is inversely DroDortional to the
total extinction coefficient. The total extinction coefficient
(bext) *-s sum t*ie extinction coefficient for the base
line visibility (bQ) and the extinction coefficients due to
absorption and scatterina of diesel particulate.
-------
4-6
Table 4-1
Extinction Efficiency (A)
for Diesel Particulate
Study A (m^/a)
Trijonis* (1982) 8.4
Klimisch (1982) 8.0
Roesslor and 6.8
Faxoq (1978)
Vuk, et al (1976) 8.2
Pier son (1978) 8 .0
The fiaure for Triionis is calculated from his extinction
efficiency for fine elemental carbon, 12 +3 m^/q, usina
a 70 percent carbon content in the diesel particulate.
-------
4-5
Thus:
bext = bo + + hsp)
The absorption and scatterinq coefficients are
oroDortional to the mass concentration of / the diesel
particulate, b = AMC. The proportionalitv constant is called
the extinction efficiency, referred to as A. There are several
values, all _.in_ a close ranae, for the extinction efficiencv for
diesel particulate; these are listed in Table 4-1. The averaqe
value, a. = 8.0 m^/a, is used for the concentration of diesel
oarticulate. (Takinq into account the carbon content of diesel
Darticulate (approximately 70 Dercent) , the extinction
efficiency for fine elemental carbon is 11.5 m^/q.)
therefore, the oortion of the extinction coefficient due to
diesels is the Droduct of the increase in particulate
concentration and the extinction efficiency of diesel
particulate, and the equation for bext becomes:
bext = bo + 8.n[rn2/qlMc (1)
In order to compute oercentaoe chanqes in visibility, the
baseline visibility extinction, bQ, must be known. baseline
visibilities were obtained from several Trijonis
reports.[£,7,8,Trijonis determined the existinq
visibilities from cumulative frequencv distributions of
aualitv-checked* aimort observations. "iqures 4-2 and 4-3
show the distribution of median visibilities for various parts
of the countrv. Visibility in the Northeast tends to be rather
low, with the relative humiditv act inq as the dominatinq
factor. Median visibilities ranqe from 8-12 miles with very
¦ -.-SJtuaJLl ..differences .ta^.me.t-ro.-oo.kitan .areas-, -,-u.r-baiv/suburban• • are-a»s-»» -• -
a^h:dr"nonurban"x;af''ea's ." For the? Southwest, the median' vis ib il i7ty*"-
is 30-55 miles in larce urban centers and 65-80 miles • at
suburban/non-urban locations. One Trijonis reoort fSl lists
median visibility levels at 94 urban/suburban locations
throuqhout the U.S; another report T91 lists median, tenth
percentile and ninetieth percentile visibility at 12
northeastern locations. Mo data exists for the annual median
visibility levels of all the major U.S. cities, so estimates
were made from the median visibilities listed above.
The baseline visibilities (LVo) are related to
extinction accordinq to the formula:
b =
o
3.0
vo
TeleDhone surveys were conducted at the airports to ensure
that each location had an adeauate set of visibility
markers for estimatinq visual ranqe, reliable reportinq
practices, observation personnel and observation locations.
-------
4-8
Figure 4-3
"oo
i rr
3
\ ^
vi
l2 tr
\ f
\U[
« 23
Figure 3 Median annual 1 PM visibilities (in miles) and
visibility isopleths for California, 1974-1976. [§ ]
-------
i
&
i, Figure 4-2
•i
ft 0*icJ on phologr*pl»lc^——~l_i
photometry
-------
4-in
IV. Revised Visibility Equations
As described earlier, the Beer-Lambert Law describes the
reduction in liaht intensity as a function of distance and the
extinction coefficient of the media. For an object outside of
the affected area being viewed from within the affected area:
~ba La
I = Iae
Where ba is the extinction coefficient existinq within the
affected area, La is the distance from the observer to the
limit- of the affected area and Ia is the light • intensity of
the object at the limit of the affected area. I3" is
described by the equation:
-b (L - L )
_ _ o a
I, = I e
d O
where L is the total distance between the object and the
observer.
Combinina the two eauations vields:
<"ba La * VL " La"
1 " V
ADplvina ^rijonis' aDDlication of Xoschmieder's Law, ln(I/I0)
is -3.0, and solvina for L (now Lv) results in:
...... .3-° - (b.a.: b0..'.La. .-
.Jtv.r.. b ' . ... -
o
where L and b are in inverse units, or
L _ 18.6 X in"4 [miles/ml - fha - bQ) La
_ .
where Lv and La are in miles and bQ and bm are in
inverse meters.
The term ba can be derived using Equation (1).
Substituting this into Eauation (4) yields:
r 18.6 X 10~4fmiles/ml - fi.nrm^/al M L .c.
L = ; ; c a (5)
h
o
-------
4-9
The -DroDortionalitv constant of 3.0 in this eouation is
aDDlicable when using airport visibility data, as opposed to
usinq the 3.91 figure from the Koschmieder formula.C61 AirDort
data does not adhere to the conditions for applying the
Koschmieder formula because natural objects at a great distance
are usually small (small objects need a contrast areater than 2
Dercent to be seen), and natural objects are never black. The
D'roDor tional itv constant of 3.0 is aopropriate accordiria to
Tr ijonis, et al.T71
to simdifv this formula's units, it may also be expressed
as:
u _ 18.6 x 10~4 rmiles/ml
bo = L fmilesl f2)
vo
where the units of extinction are inverse meters and the units
of visibility are miles.
The new visual range caused bv the addition or subtraction
of diesel Darticulate can now be calculated from the following
expression:
1«.6 x 10"4fmiles/m] _ 18.fi x ln~4 [miles/ml (3)
Li = ———————— =
V b b + 8 .0 Tm /al M
ext o c
where:
hext determined usina Fauations (1) and (2).
th'^ boyv''eatiiati'o"rr~-T'.asfales' atT '::"1sf "
' 1 *constan€ th rouahout" the entire visual ranae. This is a
satisfactory assumption for the baseline situation (i.e., to
estimate b0) . However, it may not be satisfactory to assume
that the effect of diesel particulate will be constant
throughout the visual ranae. The ambient concentration of
diesel particulate will be relatively high in the central city
and near suburban traffic corridors and will be relatively low
outside of the city or metropolitan limits. Since visibility
may extend to areas bevond the city or metropolitan limits,
this effect must be taken into account.. For those cases where
visibility extends bevond the affected area, this effect may be
taken' into account by returning to the Beer-Lambert Law and
rederiving Koschmieder1s Law assumina one value of bext for a
fixed distance (i.e., ud to some limit) and another value of
hext bevond.
-------
4-12
not circular, a reasonable aDproximation to the averaoe
distances between the center and the edge can be derived from a
calculation of a nominal radius from the actual area of the
metropolitan area, assuming it is circular "in shape.
v. Visibility Levels
A. Methodoloov
Measuring the change in visibility levels due to a chanae
in diesel narticulate is deDendent on four factors:
1. the mass concentration of the diesel particulate,
2. the extent of this concentration,
3. the extinction efficiency of diesel ©articulate, and
4. baseline visibilities.
For those cases where the visual ranoe does not extend
Dast the limits of the affected area, the visual range can be
calculated from the followina expressions:
-4
lP.fi x 10 [miles/ml (fi)
v b .
ext
b „ = frciles/ml ^ 8-0ra|2/q1* M
ext vo c
'•There Lv is the visual ranae in miles, Lvo is the baseline
visual ranae in miles, and M.c is the •¦mass — concentration kof
the diesel particulates" in grams per cubic meter.
For those cases where the visual ranae does extend beyond
the affected area, the visual range can be calculated from the
followina expressions:
L _ 18.6 x 10"4fmiles/m] - 8.0[m2/ql* McLa (?)
v
b
o
If the Dresence of diesel Darticulate is determined in
terms of the elemental carbon concentration, then 11.5
m^/a should be used instead of 8.0 m^/a.
-------
4-11
The terms b0 and Mc can be derived from Equation (2)
and air qualitv .models, respectively. Only La remains to be
described.
La is the tyoical distance between the viewer and the
limit of the affected area. Before determinina this distance,
the limits of the affected area must be defined. in the actual
situation," the concentration of diesel particulate araduallv
falls off until it reaches zero; in the model beina used, a
constant level of diesel Darticulate inside the affected area
and no affect outside is assumed. The limit of the affected
area, La, must be between the point where the actual ambient
concentration of diesel particulate beains to fall off and the
ooint where it finally reaches zero. Therefore, the affected
area's limit, La, is where the actual diesel particulate
level is aporoximatelv half of its central city level. Two
convenient limits which could suffice are: 1) the city limit,
and 2) the metroDolitan area limit. Tt has been assumed that
the metroDolitan areas and cities were circular to calculate a
nominal radius.
The metroDolitan area limits for larae cities, such as Los
Anaeles (36 miles) and New York Citv (21 miles), appear very
reasonable as diesel Darticulate penetration limits (i.e., for
Los Anaeles, La = 36 miles and for New York City, La = 21
miles). However, for smaller cities, such as Ann Arbor,
Michiaan (15 miles) and wadison, Wisconsin (20 miles), the
metropolitan area limit appears much too larae. The city
limits aopear much more reasonable for these smaller cities
(i.e., 2.6 miles for Ann(Arbor and 4 miles for Madison). Thus,
metropolitan area limits will be used for the laraest U.S.
cities and citv limits will be used for the smaller cities.
- ^h-is--w-i-i 1- "mor e~ -c lose ly^-moder; -"thes frre-*1 of"' t'he!,~a'-f f e'cte"d " ar $aST
"vieldina a^better model "for the extent of the actual diesel
oarticulate concentration level. ^0 be conservative, the
demarcation between the two will be made at a relativelv large
citv oopulation, 1,000,000, resultina in the use of
metropolitan area limits in only six cases: fhicaao, Detroit,
Houston, Los Anqeles, Mew York, and Dhiladelphia.
Now that the limits of the affected area are established,
the tvDical distance between the viewer and the limit of the
affected area must be determined. This depends on both where
the viewer is located and on which direction he is viewina.
While it is conceivable that a model could be formulated to
determine the mean viewina distance based on relative
Dopulation density and shape of the affected area, etc., the
radius of the metropolitan area or city should be a sufficient
estimate of the typical distance between a viewer and the limit
of the metropolitan area. While most metropolitan areas are
-------
4-14
Table 4-2
Average Diesel Particulate Concentrations, ug/m 3
City Size
Best Estimate
Sales
Worst¦Case
Sales
(PoDulat ion)
Relaxed
Base
Relaxed
Base
More than 1,00 0,000
.4.4
ro
•
00
5.6 ¦
4.3
S00, 000-1,000,000
3.0
1.9
4.4
2.9
250,000-500,000
2.7
1.7
4.1
2 . 7
100,000-250,000
2 . 5
1.5
3.6
2.4
-------
4-13
where Mc is the mass concentration of diesel particulate in
the affected area, La is the nominal radius of the affected
area, and
-4
18.6 x ID [miles/ml
b =
¦ o L
vo
where Lv0 is the baseline visual ranae without the effect of
diesel oarticulate.
*. Results
As described in the Drevious section, three pieces of
information are needed for each citv in order to project the
effect of diesel Darticulate emissions on its visibility: 1)
citv radius, 2) baseline visibilitv, and 3) the ambient
concentration of diesel particulate. . The baseline visibility
and the nominal radius were estimated for each citv and
metropolitan area with 100,000 inhabitants or more.
The ambient diesel particulate concentrations in 1995 for
various cities were estimated in Chapter 3 (see Table 3-4 of
that chapter). There are four concentration values relatina to
the four reaulatorv scenarios: 1) best estimate sales, relaxed
controls, 2) best estimate sales, base controls, 3) worst case
sales, relaxed controls, and 4) worst case sales, base
controls. "owever, these ambient diesel particulate
concentrations are not available for every citv with 100,000
oeoole or more. "^hus, the available concentrations were
-averaaed- -accordina to._.;city*_;;s;i,"z'e; . and" us'ed '.;'fp.r.l Lthose ,"cities" "for
which projections were' not available. The four citv-size
cateaories and their corresponding averaae particulate
concentrations are listed in Table 4-2.
Aoplvina the baseline visibilities, nominal radii, and
1995 ambient diesel oarticulate concentrations to the
appropriate city situation (represented bv Equation 6 or 7)
vields absolute visibility levels in 1995 for each of the four
scenarios. From these citv-soecific visibilitv projections,
the effect of 1995 diesel particulate concentrations on
baseline visibilitv can be estimated. ^he averaae visibility
reduction for each citv-size cateaorv and diesel control
scenario is shown in ^able 4-3.
-------
4-16
As can be seen, the visibility impact of all scenarios is
strongly dependent on city size, with the larger cities
experiencing the larger effect. This is primarily due to the
greater diesel particulate concentrations projected for larger
cities (see Table 4-2). However, the especially large
visibility effects. experienced by the cities having a
population of more than one million is also due to their larger
estimated radii. As was described earlier, the entire
metropolitan area was assumed to be affected by diesel
particulate emissions in these instances, where in the cases of
the three smaller qroupings, only the city proper was assumed
to be affected.
with respect to the various scenarios, under best estimate
sales the relaxed scenario reduces visibility by 4-20 percent.
These visibility reductions are reduced to 2-15 percent under
the base scenario. Under worst case sales the visibility
reductions under both the relaxed and base scenarios are much
greater, 5-27 percent and 3-19 percent, respectively. In both
cases, the base scenario removes approximately one-third of the
visibility reduction of the relaxed scenario.
VI. Uncertainties in the Model
The uncertainty present in the methodology used above can
bias the results in one direction or the other. Although the
degree of these biases cannot be measured, it may be possible
to indicate if the biases are upward or downward. This section
will examine the uncertainties involved in this methodoloav for
measuring the change in visibility caused by an increase in
diesel particulate, noting the biases.
An average value of 8.0 mVg for the extinction
efficiency of diesel particulate was drawn from several
reports. This value may be a conservative estimate according
to a National Research Council report.r101 As a larger
extinction efficiency would yield a greater visibility impact
due to diesel particulate, the currently projected impacts may
be somewhat low.
The proportionality constant of 3.0 was used in place of
Koschmieder's value of 3.91 to account for the real conditions
present when measuring baseline visibilities as opposed to the
theoretical conditions of the Koschmieder formula. Certainly
this figure is an approximation and varies depending upon
geographical and climatic conditions, but any resulting bias is
unknown.
Diesel particulate concentrations and visibility levels
were modeled as single values for each city as a simplification
of the actual situation. These values assumed that all
individuals in an area experienced identical levels of diesel
Pl ^ f" * 1 ^ 3 ^ O '¦ 1 7 <*(*•<*%<' 1 ' — < ' f «* « JU i. « - «, m •• « - ' ' - 1
-------
4-15
Table 4-3
Average Reduction in visibility
Due to Diesel Particulate, Percent
City Size Best Estimate Sales Worst Case Sales
(Populat ion) Re laxecf Base Relaxed^ Base
More than 1,000,000 20 15 27 19
500,000-1,000,000 8 6 12 8
250,000-500,000 6 4 10 *
100,000-250,000 4 2 5 3
-------
4-17
This can lead to an overestimate of exposure for some
individuals (e.g., those living inside the city area border)
and an underestimate for others (e.g., those living outside the
city border where the particulate level is assumed to drop off
to zero). Also, visibility is strongly weather dependent and
the baseline visibility levels took no account' of this.
However, the resulting bias is again unknown.
VII. Conclusions
A method exists to determine the visibility impact of a
specific level of diesel particulate. The necessary input data
include the ambient mass concentration of the diesel
particulate, the extent of this concentration (assumed to be
the city limit), the extinction efficiency of diesel
particulate (a value of 8.0 m3/g is used) and baseline
visibilities for each city.
Visibility levels in 1995 for all U.S. cities with more
that 100,000 inhabitants were projected under four regulatory
scenarios. The larger cities showed a greater reduction in
their visibility levels for each scenario. Under the best
estimate diesel sales scenario, the relaxed control scenario
resulted in a visibility loss of 4-20 percent, while the
visibility reduction under the base scenario was 2-15 percent.
Under the worst case diesel sales scenario, visibility
decreased 5-27 percent under the relaxed scenario and 3-19
percent under the base standards. In both cases, the base
scenario removed about one-third of the loss in visibility due
to diesel particulate emissions under the relaxed scenario.
-------
4-18
References
1. "Health, Soiling and Visibility Benefits of
Alternative Mobile Source Diesel Particulate Standards,"
Mathtech, Inc. for U.S. EPA, Office of Policy Analysis. EPA
Contract Number 68-01-6596, December 1983.
2. "Visibility Protection for Class I Areas, The
Technical Basis," University of Washington, Seattle, Prepared
for Council on Environmental Quality, Washington, D.C.,
Pb-288842 ,. August 1978.
3. "Heavy-Duty Diesel Particulate Regulations, Draft
Regulatory Analysis," U.S. EPA, Office of Mobile Sources,
Chapter V, December 1980.
4. "A Study of Particulate Emissions from Motor
Vehicles, A Report to Congress," U.S. EPA, Office of Research
and Development, Bradow, et al., 214 Draft, Section 7.2.
5. "Characterization of Gaseous and Particulate
Emissions from Light-Duty Diesels Operated on Various Fuels,"
Southwest Research Institute, EPA-460/3-79-008, 1979.
6. "Existing Visibility Levels in the U.S.," Trijonis
and Shepland, Technology Service Corporation for U.S. EPA,
Grant No. 802815, EPA-450/5-79-010, 1979.
7. "Impact of Light-Duty Diesels on Visibility in
California," Trijonis, Final Report for California Air
Resources Board , Contract No. Al-117-32, 1982.
sr. . v-fw
' 8'." £"";" Visibility' "in "the Southwest ' "- and" Exploration of
the Historical Data Base," Trijonis, Atmosoheric Environment,
Vol. 13, od. 833-843, 1978.
9. "Visibility in the Northeast," Trijonis and Yuan,
Technology Service Corporation for U.S. EPA, Grant No. 803896,
EPA-600/3-78-075, 1978.
10. "Diesel Cars - Benefits, Risks, and Public Policy,"
Final Report of the Diesel Impacts Study Committee, Assembly of
Engineering National Research Council.
-------
CHAPTER 5
CANCER RISK ASSESSMENT
I. Introduction
Of the potential health effects associated .with diesel
particulate emissions, perhaps the greatest concern has been
associated with its potential carcinogenic effects. This
chapter will examine the state of knowledge concerning the
carcinogenic potency of diesel particulate and estimate the
effect of various diesel particulate control scenarios on an
individual's lung cancer risk. The non-cancer health effects
associated with diesel particulate ...ar.e. examined -in Chapter 6.
The first section of this chapter reviews the major
studies which have investigated the carcinoaenic potency of
diesel particulate. The second section compares the results of
these studies and selects a likely range of carcinoaenic
potency for diesel particulate. The third section examines
trap-oxidizer removal efficiencies of suspected carcinogens
with respect to total diesel particulate matter and makes
adjustments to the base scenario exposure estimates (Chapter
3). The final section combines the carcinogenic potency with
the adjusted exposure values to estimate the annual lung cancer
risk for an individual under each control scenario.
II. Review of Major Studies
The potential carcinogenicity of diesel particulate has
been examined through both human epidemiological studies and
clinical studies on animals and other lower oraanisms. Because
the epidemiological data base is limited, much weight has had
to be placed on the. cHnica.,1.,~s,t.ud.ies.^These- 5fHni.q^-i.,^sti44iCers!
est-i-ma;£e'-"J.the^barqtnddle'nic 'potency • o'f'! d'iesel"""particulate by
^eSmoarTng"4' their clinical results to the clinical results of
other cancer-causing substances for which human epidemiological
data are available. In this section, past and current
epidemiological studies will first be reviewed, followed by a
review of the comparative potency analyses.
A. Epidemiological Studies
The best means to determine the risk of developing lung
cancer from a given exposure of diesel particulate is to
conduct a long-term epidemiological study. Such a study would
trace the health of several well-defined groups of people who
were exposed to orecisely known concentrations of diesel
particulate for known periods of time. Comparable groups that
were not exposed would also be monitored in order to detect any
-------
differences in cancer rates. The influence of such factors as"
diet, family history and smoking would be known in order to
strenathen the validity of the study's findinas and reduce the
margin for error.
No matter how close the correct methodology is followed,
an epidemioloaical study cannot "prove" the absence of a cancer
hazard. Rather, a negative epidemioloaical study yields a
statistical upper bound on the potential potency of a
carcinoqen under various assumptions of how the carcinogen
affects cancer rates. A sound epidemiological study will only
indicate that a model with an upper bound risk estimate is
reasonable "in the absence of contrary information".[11 With
these limitations of an epidemioloqical study noted, two
studies of diesel particulates will be reviewed: 1) the London
Transit Authority Study, which was completed a number of vears
ago, and 2) the U.S. Railroad Workers Study, which is still
underway.
1. London Transit Authority
Of the epidemiological studies completed to date which
specifically examine diesel emissions, the London Transit
Authority (LTA) Study is generally considered to be the most
thorough, althouqh it too has significant deficiencies.[2] This
studv initially examined the luna cancer incidence amona
different qroups of LTA employees between 1950 and 1954,[3] and
was later updated to include the years through 1974.[4] Among
the groups followed were diesel bus garage workers (generally
hiah level of exposure) and design enai'neers (aenerallv low
level of exposure) .- - Lung - cancer- incidences were identif ied
from information on .the death certifijcates.„J:hj5S,e._Wwhp .„were_
retirement records, and the records of transfers to other LTA
job categories. The study did not continue to monitor the
health of individuals once they were no lonqer employed by the
LTA. This is an area of potential bias since cancer typically
develops several years after initial exposure to carcinogens or
even after exposure terminates. j
Other weaknesses of the study include the fact that the
extent of individual exposure to diesel exhaust was not
measured. Instead, oarticulate concentrations were simply
measured inside and outside of selected garages on a few
separate days durinq the 1950-74 observation period. Also, no
SDecific cohort of employees was identified and followed
throughout the study. Thus, the potential influence of such
factors as smoking habits, medical history and related
socioeconomic characteristics is not known.
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5-1
The study found that the cancer incidence of the highly
exposed group was actually less than that expected based upon
Greater London lung cancer death rates in the 1950-74
timeframe. Thus, the study concluded that in regard to this
study population, no evidence existed associating lung cancer
to diesel engine exhaust.
However, this study has been analyzed independently by Dr.
Todd Thorslund of EPA's Carcinogen Assessment Group "and Dr.
Jeffrey Harris, a member of the Analytical Panel of the
National Academy of Sciences (NAS) Diesel Impacts Study
Committee. 3oth found that the potential errors involved in
the LTA study could have resulted in a sizeable underestimation
of the carcinoqenic potency of diesel particulate.fl,21
Based on the analyses by Thorslund and Harris, it is
possible that sianificant excess cancer deaths could result in
the general population even though the LTA study showed no
excess cancer deaths in the diesel particulate exposed group.
Thus, the LTA study's conclusions for its population cannot be
translated to the general population. Due to the potential
errors involved and the lack of an upperbound estimate, this
work has been disqualified from further consideration in this
study.
2. U.S. Railroad Workers
Another epidemiological study is currently being conducted
by Harvard University to evaluate the possible carcinogenic
effect of diesel exhaust in U.S. railroad workers. Data for
the study come from the U.S. Railroad Board. Components of the
study include: 1) a retrospective. _ cohort.,, analysis of
' approximately'-.*5-7-,-000 "'¦male-railroad: :worker's," "2) a "'case-cbntro-i'-^.'
study of 300 incident lung cancer cases and matched controls of
railroad workers, and 3) actual environmental monitoring of
worker exposure to diesel exhaust. These approaches will allow
for quantitative assessment of both level and duration of
diesel exhaust exposure, and consideration of the major
confounding factor (cigarette smoking), thus removing the major-
design weaknesses of the LTA study.
The retrospective cohort consists of approximately 57,000
male railroad workers, aged 40-64 in 1959, with 10-20 vears of
railroad service at that time. These workers were selected
from job categories having hiqh diesel exposure and an
appropriate sample of control exposure categories. The massive
amount of data being generated in the retrosoective and
case-control studies is currently being analyzed. Air
pollutants being monitored in five round-house locations
include nitrogen dioxide, sulfur dioxide, carbon monoxide,
-------
5-4
respirable and non-respirable particulate and its constituents,
such as sulfates, polycyclic aromatic compounds and other
organic compounds. In addition, fractions of the Darticulate
sample extracts will be analyzed by mutagen bioassays, such as
the Ames test. A Qualitative comparison of automobile diesel
exhaust with the railroad diesel exhaust will be performed by
correlating the aas chromatoaraphy/mass spectra of the
polycyclic aromatic compounds of each.
A pilot study was undertaken to evaluate the feasibility
of this larger study. The cohort of the pilot study consisted
J?f. approximately 2,500 male railroad workers who were between
_the ages of 45 and 64, working in 1967 and who had at least 10
years of railroad service. Of these workers, 69.8 percent were
in occupations exposed to high concentrations of diesel
exhaust. The risk ratio for luna cancer in diesel-exposed
workers relative to unexposed workers was 1.42, or a 42 percent
increase. However, this increased risk was not statistically
significant due primarily to the small size of the cohort. [51
The larger retrospective cohort study and the case-control
study are currently in progress and are scheduled for
completion in the near future; at the time of this writing, no
formal results have been published.
B, Comparative Potency Analyses
Due to the limited epidemiological data available,
estimations of the human lung cancer risk from diesel
particulate have been made usinq a comparative potency method
developed by EPA.[6] In this comparative potency method, the
results of non-human laboratory bioassays are used to compare
..the ...carcinogenic- ¦and...mutagen.ic.._.po.t.en,cies.. of .-d.i_esel_ particulate
'{"Sp"e'ci-'f i'cal-ly", the"•pwrt-i'd'e-bound -o'rganics) • with -those* of—other--
combustion and pyrolysis products that have been shown by
epidemioloaical data to cause lung cancer in humans. Estimates
of the human lung cancer risks from exposure to these
established carcinogens, based on epidemioloaical studies, can
then be adjusted by the corresponding estimates of their
potencies relative to diesel particulate to yield estimates of
the lung cancer risk from diesel particulate. The equation
used is given below.
Estimated _ Human Risk Bioassav Potency (diesel)
Human Risk ~ (carcinogen) Bioassay Potency (carcinogen)
(diesel)
The ratio of potencies obtained from the same bioassay is
referred to as the relative potency. The unit risk exposure,
referred to in terms of constant exposure per year, always
assumes a lifetime exposure. The unit risk is calculated for
each emissions source in order to have a basis for comparinq
carcinogenic potency.
-------
5-5
This methodoloqy is based on the assumption that the ratio
of the carcinogenic potency of diesel emissions to the
potencies of proven carcinogenic products is preserved across
human and non-human biological systems. Although this
assumption has not been proven and is a novel approach to risk
assessment, EPA has determined that the comparative potency
approach is the most promising method available until a
reliable epidemioloaical study focusing on exposure to diesel
exhaust is performed.
The human carcinogens (comparative sources) selected by
EPA were coke ov.en emissions, roofing tar emissions and
cigarette smoke condensate."" The" mobile source samples selected
included those from a HDDE (Caterpillar 3304), three LDDVs
(Datsun Nissan 220C, Oldsmobile 350, and Volkswaaen
turbocharqed Rabbit), and a gasoline-fueled, catalyst-equipped
vehicle (Ford Mustang II) . Data from other LDDVs were also
reviewed and will be summarized later in this section. The
organics extracted from the particulate emitted from the
above-mentioned sources were used to determine the relative
potencies.
The comparative sources and the mobile source samples were
both tested in mutagenesis and carcinogenesis bioassays. The
mutagenesis bioassays selected included reverse mutation in
Salmonella typhimur ium (Ames test) , forward mutation in L5178Y
mouse lymphoma cells, forward mutation in Balb/c 3T3 mouse
embryo fibroblasts, forward mutation in Chinese hamster ovary
cells, mitotic recombination in Saccharomvces cerevisiae, DNA
breakage in Syrian hamster embryo cells, and sister chromatid
exchange in Chinese hamster ovary cells. The carcinogenesis
bioassays included oncogenic transformation in Balb/c 3T3
©elIs•; ra 1 ^enh-awement " of transfermatibri.";'in" " Syr ian" "hamster
embryo cells, and skin iriitiation""and skin carcinogenicity in
SENCAR mice. Further details of the study design can be found
elsewhere.[7]
The potencies obtained in these bioassays, together with
epidemiological data on the comparative sources, were combined
to estimate the human lung cancer risk from diesel particulate
in three independent analyses performed by Dr. Jeffrey Harris,
Lovelace Biomedical and Environmental Research, and EPA. Each
will be discussed below. The analyses differ with respect to
the choice of bioassays selected for determination of the
relative potencies and the choice of comparative source
epidemiological data.
It should be noted that EPA did not conduct new
epidemiological studies as part of this approach, but rather
relied upon existing data. For coke ovens, the work of
-------
5-6
Mazumdar[3] and Land [9] was used, for roofing tar emissions
Hammond1 s[ 10] data were applied, and that of Dell and Petofll]
were used in the case of cigarette smoke. The Harris and
Lovelace analyses relied upon the same coke oven and roofing
tar data. For ciaarette smoke, Lovelace used the data of
USHEW,[12] Hammondfl3] and Kahn,fl4] which resulted in a risk
estimate similar to that obtained by EPA. Harris did not
include cigarette smoke as a comparative source in his analysis.
,1. Harr is
In addition to his analysis of the London Transit
Authority Study,- Harris ~ conducted a comparative potency
analysis for the National Academy of Sciences.[1] The
comparative source emissions selected by Harris were coke oven
emissions and roofing tar emissions. Using a linear relative
model, Harris analyzed the epidemiological data for coke oven
and 'roofing tar emissions to obtain estimates of the
proportional increase in lung cancer incidence per unit of
cumulative lifetime exDosure to coke oven emissions (0.044) and
roofing tar emissions (0.015).
Harris used data from three short-term bioassavs to
estimate the relative potencies of the diesel (light-duty only)
and comparative source samples. The bioassays used were tumor
initiation in SENCAR mice by skin painting, enhancement of
viral transformation in Syrian hamster embryo cells, and
mutagenesis in L5178Y mouse lymphoma cells. The results from
these bioassays can be found in Tables A-l and A-2 of the
Appendix. Harris then applied these relative potencies to his
estimates of the proportional increase in lung cancer incidence
from "exposure to coke oven and roofing.tar._emissions to-obtain
estimates: ^b_.f\.feh,e proportional increase in -d'un"g™tfaTTcer incidence '
"froirt exposure to diesel emissions.
Harris' overall estimate was a 0.0035 percent proportional
increase in lung cancer incidence per unit exposure (i.e., one
microoram per cubic meter of diesel particulate for one year
assuming lifetime exposure). This is roughly equivalent to 1.4
x 10"^ incidences of lung cancer per person per year due to a
continuous lifetime exposure of one microgram . per cubic meter
of diesel particulate.*
The proportional increases in luna cancer incidence
obtained by Harris were translated into absolute measures
of lung cancer incidence independently by Thorslund.[6]
-------
5-7
2. Lovelace Biomedical and Environmental Research
Lovelace used two methodologies to estimate the cancer
risk from exposure to LDD particulate.[15]
The first method assumed that diesel particulate was not
more mutagenic or carcinogenic than the most potent of coke
oven, roofing tar or cigarette particulate. First, the annual"
lung cancer risk per person for each of the three carcinogens
was estimated from the -epidemiological studies of coke oven
workers, roofers, smokers and nonsmokers using a linear,
nonthreshold model. Then, the average concentration of each
type of particulate inhaled over a year was estimated and used
to estimate the annual unit lung cancer risk per individual for
these comparative sources. All of these figures are presented
in Table 5-1. Lovelace then assigned a figure of 1.5 x 10"®
lung cancers per person due to a lifetime exposure of one
microgram per cubic meter of diesel particulate as an upper
estimate of the potency of diesel particulate. This fiaure was
based primarily on the estimated annual unit risks for coke
oven and roofina tar particulate, which are both between 1.0 x
10"6 and 1.5 x 10"6.
The second method used the bioassay data developed by EPA
fco estimate the relative potencies of the LDD and comparative
ource samples. Like Harris, these relative potencies were
then applied to the unit risks derived from the epidemiological
studies of the known carcinogens.
The comparative sources selected from the EPA work were
coke oven emissions, roofing tar emissions and cigarette smoke
condensate. Urban soot was also selected independently by
Lovelace as-- an" add'i'tidna-1 -compa-rat;ive. source . ; •The mutageneses'
"bioas'says" use'd "we're" the' Ames assay, forward mutation in' Chinese
hamster ovary cells (HGPRT qene locus assay), forward mutation
in L5178Y mouse lymphoma cells, and forward mutation in Balb/c
3T3 mouse embryo fibroblasts. The carcinogenesis bioassavs
used were oncogenic transformation in Balb/c 3T3 cells, viral
enhancement of transformation in Syrian hamster embryo cells,
and skin initiation and skin carcinogenicity in SENCAR mice.
These bioassay data are presented in Table A-3 of the Appendix,
The overall relative potencies resulting from a comparison
of the data in Table A-3 are shown in Table 5-2, along with the
annual unit risks already presented in Table 5-1 and the
estimated annual unit risks for diesel particulate resulting
from each comparison. When only the comparative sources used
by EPA are considered (coke oven, roofing tar and ciaarette
smoke condensate), the annual unit risk estimates for diesel
particulate range from 0.07 x 10"^ to 0.6 x 10"® lung
-------
5-8
Table 5-1
Summary of Inhalation Exposures and Annual
Lung Cancer Risks for Surrogate Populations - Lovelace*
Study
Population
Average Air fa 1
Concentration
of Particles
(mq/m3)
Annual Lung Cancer
Risk x 10® (per
person, oer year)
Annual Risk
x 106
(per person,
per ug/m,
per vear)
Coke Oven
Workers
Roofers
Smoker s:
(cigarettes/
day)
1-9
10-19
20-39
40 +
Urban
Nonsmokers
Rural
Nonsmokers
3
1
2-16
18-35
36-71
73 +
0.06
0.03
4000--
1100
260
470
800
1070
70
1.-3
1.1
0
0
0
0,
03
02
02
01
30
1.2
1.0
[a]
Information' in "this table was excerpted from Reference 15.
The average air concentration of particles was estimated
as the total mass of particles inhaled per year divided bv
all of the air breathed per year (assumed to be 20 m3
per day X 365 days per year).
-------
5-9
Table 5-2
Lung Cancer Risk
From Exposure to Diesel Exhaust Based Upon
Relative Potencies of Surrogate Substances - Lovelace*
. . Median
Relative Annual Cancer Estimated Risk of
Surrogate (sE??S§S^e/ (P^f^pi^ion Si8®e}pe?r£4?i8fie
Exposure diesel ratio) per ug/m3) per ug/m3)
Coke Oven.- - 5 - - -1.3- 0.3
Emiss ions
Roofing Tar 2 1.1 0.6
Vapor
Ciaarette 0.3 0.02 0.07
Smoke
Condensate
Urban Soot 0.4 1.2 3.0
Selected 1.0
Diesel Lung
Cancer Risk
Information on this table was excerpted from Reference 15.
-------
5-10
cancers per person per year due to a constant lifetime exposure
of one microgram per cubic meter of diesel particulate (unit
exposure). when urban soot is also considered as a comparative
source/ the range increases to 0.07 x 10"^ to 3.0 x 10~*>.
Based on the results of both methods, Lovelace chose 1.0 x
10~6 as being the most representative estimate for- the annual
unit lung cancer risk due to diesel particulate.
3. Environmental Protection Aaencv (EPA)
Members of EPA's Office of Research and Development also
recently estimated, the annual unit cancer risk of diesel
particulate using a comparative potency method very similar to
that used by both Harris and Lovelace.[16] The comparative
sources used in this analysis were coke oven, roofing tar and
cigarette smoke. Epidemiological data for coke oven workers,
roofing tar workers and cigarette smokers were examined using a
linear, nonthreshold model to determine the annual unit lung
cancer risk for each carcinogen. A summary of these risk
estimates can be found in Table A-4 of the Appendix.
The relative potencies of the coke oven, roofing tar,
cigarette smoke condensate and mobile source samples were
evaluated by a large number of bioassavs which have already
been described. The bioassays used in the final determination
of the relative potencies were the tumorigenicity bioassays
involving skin initiation and skin carcinogenicity in SENCAR
mice, the Ames bioassay, the L5178Y mouse lymphoma cell
mutagenesis bioassay, and the sister chromatid exchange. (SCE)
bioassay in Chinese hamster ovary cells. The results from
these tests are given in Tables A-5 and A-6 of the Appendix.
It should be noted that the mobile ^source _and compar.ajtive
-s;outce- samples were" also; evaluated - in a ^number-^ of - additional'
bioassays. The bioassays used in this analysis (and those
selected in the Harris and Lovelace studies) were selected for
their ability to produce dose-related effects and the strenath
and relevance of the end point being measured. The relative
potencies are shown in Tables A-7 and A-8.
Two steps were subsequently followed to determine the lung
cancer risks for the diesels and the gasoline vehicle. First,
the relative potencies in the mouse skin tumor initiation assay
(Table A-7) were used to obtain the annual unit risk estimate
for the Nissan particulate from the annual unit risks for the
coke oven, roofing tar and cigarette smoke condensates (Table
A-4). Second, the annual unit risks for the other diesel
particulates were obtained by multiplying the annual unit risk
of the Nissan particulate by the net relative diesel potencies
of Table A-8, which were based on the Ames, lymphoma and SCE
bioassays.
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5-11
The annual unit lung cancer risk estimates resulting from
these calculations are shown in Table 5-3. Since the organics
extracted from the particulate were used in the bioassays, the
risk estimates were calculated in terms of organics and then
converted in terms of particulate. For the three LDDVs, the
annual risk estimates per person range from 0.26. x 10"^ to
0.46 x 10~6 due to lifetime exposure to one microgram per
cubic meter of particulate. The LDDV with the highest risk
estimate, the Nissan, was initially selected as representative
of abnormally high particulate organic mutagenic activity for
an uDper ranoe value. Although engines of this type are
reported to have faulty injector systems that result "in the
high activity emissions, other studies show a number of LDDVs
with Ames mutagenicity activities above that reported for the
Nissan. [15] Hence the Nissan risk estimate is not unreasonably
high for a diesel vehicle.
It is interesting to note that emissions from the
Caterpillar HDDE had about one-tenth the potency of the LDDVs,
This may be due to two reasons: 1) the particulate from the
Caterpillar had been stored for more than a year before use,
and 2) except for the Caterpillar, all the vehicles were
operated on a chassis dynamometer using the highway fuel
economy test cycle (HWFE7). The Caterpillar engine was tested
on an engine dynamometer and operated at low load conditions
(Mode II using a steady-state operation of 2200 rpm and an
85-pound load) , possibly resulting in low activity. Due to
these non-representative conditions, the risk estimate for the
Caterpillar particulate will not be used further.
Ames test results on diesel particulate samples other than
those cited in the above analysis were also reviewed. Major
emD'hasis was- 'on"'i:ig'h-t--duty" diesel veh icles , oar ticular ly In-use '
a'utomo'bireV," to'""""ensuri ' "the" "rVprersentat'iveness' "o'f; ' ttier
above-described results. Due to availability of data, and
because the TA-98 strain was used in the earlier analysis, data
for this particular strain were of primary interest.
Results of four separate studies on the specific mutagenic
activity of diesel particulate are summarized in Table A-9 of
the Appendix[17-201 ; numbers of revertants per ug of SOF
(soluble organic fraction) are aiven for samples both with and
without metabolic activation. Means for the specific
activities range from 0.97 to 13.7 for the non-activated
samples, and between 2.08 and 8.66 rever tants/ug SOF for the
metabolicallv-activated tests.
A comparison of these supolementary data with the values
used to determine cancer risk estimates earlier in this section
shows fairly strong agreement. The specific activities listed
-------
5-12
Table 5-3
Unit Lung Cancer Risk Estimates
for Diesel Particulate - EPA*
Unit Risk Estimates-
(annual risk/uq/m^)
Diesel Source
Nissan[a]
Volkswagen Rabbit[b]
Oldsmobile[b]
Caterpillar[b]
Orqanics
0.58 x 10"5
0.17 x 10-5
0.16 x 10"5
0.87 x 10"7
Particulate
0.46 x 10"6
0.30 x 10-6
0.26 x 10'6
0.024 x 10"6
* This table was excerpted from
lifetime risks were presented,
converted to annual risks by
lifespan (76.2 years).
[a] Based on average relative mouse
activity (Table A-7).
[b] Based on average relative activity in the mouse lymphoma,
SCE, and Ames Bioassays (+MA) (Table A-8).
Reference 16 in which
These risks have been
dividing by the median
skin tumor initiation
-------
5-13
for diesels in the comparative risk study (Table A-5) average
5.7 and . 5.8 revertants/ug SOF for the non-activated and
activated strains, respectively, excluding the Caterpillar
data; this compares to overall means of 5.3 and 6.1 in Table
A-9. A comparison of maximum specific activities shows 11 and
13 revertants/ug for non-activated and activated samples,
respectively, in Table A-5, versus 21 and 13 in' Table A-9
(again excluding the Caterpillar). These maximums support the
judgment that the Nissan estimates from Table A-5 are not
unusually high and are reasonable estimates of maximum
potencies for diesel vehicles. The close agreement between the
overall means in both tables add further support for the
representativeness of the data used in calculating the cancer
risk"'estimates for diesel particulate and for . exclusion of the
Caterpillar data.
III. Choosing a Value or Range of Values
A summary of the risk estimates obtained from the three
comparative risk studies is shown in Table 5-4. It should be
obvious from the preceding discussion and a comparison of the
figures in Table 5-4 that there is no concensus among the
scientific community as to the carcinogenic potency of diesel
particulate. The three potency studies differ at nearly all
possible points: 1) the estimated annual unit cancer risks of
the known carcinogens, even though, for the most part, the same
epidemiological data are used, 2) the non-human bioassays
selected for actual derivation of the relative potencies, and
3) the relative weightinqs given to those bioassays selected.
In addition, all of these studies rely on the assumption
that the relative carcinogenic potencies of diesel emissions
and the related environmental -emissions..-.._ar:e:;..rp-reserved across ••
..• huroa.n-1C.4.«aai-^no.n.r h«maa--¦ • biologi-ca-1-- ¦»'-'sV'St'ems". Although
assumption has not been proven correct, it is the best one that
can be .made until a reliable epidemiological study focusing on
exposure to diesel exhaust is performed.
It should also be noted that all of the comparative
potency analyses discussed used a linear, nonthreshold
dose-response model to extrapolate cancer incidence to lower
doses. While this has been the most widely used model in the
past, others are gaining mere use presently. Figure 5-1
depicts two typical examples of other models: an infralinear
model and a linear, threshold model.[21] Since all the
exposures simulated in the non-human laboratory tests are very
high to demonstrate effects with small number of specimens, the
results must be extrapolated downward to lower, more realistic
doses. Examining Fiqure 5-1, the point common to all three
models can be taken to be the result of the high-dose
-------
5-14
Table 5-4
Summary of Lung Cancer Risk Estimates
Annual Risk x 10^
Comparative Potency (per person per ug/m^
Analysis particulate)
Harris 1.4 ¦
Lovelace 1.0[a]
EPA 0:26-0.46 [b] "
[a]when the EPA comparative sources were used, the risk
estimates obtained by Lovelace range from 0.07 x 10~6 to
0.6 x 10"®. when urban soot was also considered by
Lovelace as a comparative source, the risk estimates range
from 0.07 x 10"° to 3.0 x 10"6. Lovelace chose 1.0 x
10~6 as being most representative.
[b] Since the heavy-duty Caterpillar sample is not considered
representative, the range of risk estimates is restricted
to the range of risk estimates obtained for the light-duty
vehicles.
-------
5-15
bioassay. Then, as can be seen, both the infralinear and
linear, threshold model result in lower, low-dose risks than
the linear, nonthreshold model. Because of this, depending on
which model is correct, the use of the linear, nonthreshold
model could overestimate the cancer risk at lower doses. To
date, however, the linear, nonthreshold model has been the only
one applied to diesel particulate emissions.*
Because of the lack of consensus among the various
studies, this study will use the ranqe of risk estimates
obtained from the comparative potency analyses of Harris,
Lovelace and EPA. Referring to Table 5-4, the ranqe of risk
estimates selected for this analysis is 0.26 x 10~6 to 1.4 x
10"® lung cancers per person per year due to a constant
lifetime exposure of one microgram per cubic meter of diesel
particulate.
IV. Reduction in Cancer Risk Via Total Particulate Control
In Chapter 3, individual annual exposures to diesel
particulate matter were estimated for the relaxed and base
scenarios (Table 3-8) . The reduction in exposure between the
relaxed and base scenarios reflects projected trap-oxidizer
efficiencies in removing total diesel particulate (namely those
of non-catalyzed traps). In the interest of projecting cancer
risk from exposure to diesel particulate emissions, the actual
removal of suspected carcinogens should be compared to the
overall reduction in total particulate mass.
This section will concentrate on the effects a particulate
trap has on the soluble organic fraction (SOF) of diesel
particulate. It is this SOF, particularly the .heavier,
$ydroca'rbb'ns that... is. .usually... ...associated -with, the buik-:6"f-
bio-activity; this bio-activity, in turn, is generally
considered an indication of carcinogenic tendencies. Part A of
this section will evaluate the trap's ability to control SOF
with respect to total particulate. Part B considers possible
changes in mutagenic or carcinogenic tendencies of the organics
with the use of a trap. Part C will evaluate data from
previous sections in order to determine a ratio of removal
efficiencies (SOF to total particulate matter); in turn, this
ratio will be used to adjust the exposure figures from Chapter
3 .
There is one additional model, the suDralinear model,
which actually results in a higher, low-dose risk than the
linear, nonthreshold model;[21] however, its application
to diesel particulate would be the furthest from being
established of all of the other models.
-------
5-16
The data examined in this section were limited to studies
performed with non-catalyzed, ceramic particulate traps. This
distinction was made in an effort to examine perhaps the
"worst" case with respect to carcinogen removal. Non-catalyzed
traps primarily filter solid particulate matter; heavy
hydrocarbons can still be in the gaseous phase at the trap and
can escape and later either adsorb onto the remaining
particulate or remain in the gas phase. Catalyzed traps reduce
gaseous" hydrocarbons" preferentially to particulate matter.
Therefore, the use of catalysts in particulate traps would be
expected to reduce"" cancer risk""to' an "even oreater extent than
they reduce total particulate matter. As the costs of
non-catalyzed traps are used in Chapter 8, non-catalyzed traps
were chosen"" he re "to"" "represent the reduction in cancer risk due
to base scenario'control measures.
At this time, it is important to note that data examining
various carcinogenic parameters both with and without trap use
were very limited in their availability. This study bases its
preliminary conclusions on existing data" only; no new tests
were initiated. Some areas of the study (such as soluble
organics removal) had more pertinent data available than did
others; therefore, in drawing conclusions, more weighting was
given to these areas. New information may become available in
the future that could modify these results.
A. 5QF Removal Efficiencies
For all the available data examined, it was found that
actual emission rates for soluble organics were reduced
substantially with the particulate trap in place; however, the
SOF -removal efficiency was, in most cases, somewhat lower than
that for Jtotal parjii.c.ula.te. redyction^ Due to^this lower_ SOF
-ef fic'iency.7. £he- "Vftie-r*- trap" S'OF "as. V percent" -of—total . ma sir.--was*
generally found to be higher than the "before-trap" SOF
percentage. For HDDVs, average reduction efficiencies for
"total particulate and SOF were 76 and 68 percent, respectively;
for LDDVs, the total efficiency of 80 percent was somewhat
higher than the SOF removal of 69 percent. For both classes,
the efficiency "gap" was approximately the same (8 to 1-1
percent) . (See Tables A-10 and A-ll in the Appendix for test
data on SOF emission rates.[22-26])
when the actual fraction of soluble organics (expressed as
a percent of total mass) is examined before and after the trap,
the "with-trap" SOF tends to be higher than the baseline
percentage. The increase in percent SOF for the LDDVs is
substantially higher than that shown with the HDDVs; the SOF as
a percent of total particulate increased (on the average) by
23.4 percent and 11.4 percent for light and heavy vehicles,
respectively (see Tables A-12 and A-13).[22-261
-------
5-17
There is one concern related to simply focusing on the
SOF. The SOF is made up primarily of unburned organics that
condense or adsorb onto the solid particulate matter; organics
that do not attach to solids remain in the gaseous phase.
Since the trap removes the great majority of the particulate to
which unburned HCs can attach, one concern is. that more
organics will remain in the gaseous_pha.se. This concern was
addressed by examining available data on gaseous HC emissions
with and without a trap. In six LD and three HD studies, 90
percent of the data showed either a decrease in HC emissions or
no change at all with the use of a trap; in all instances
except one, any increases were less than three percent higher
than 'baseline data (see Tables A-14 and A-15). Overall,
gaseous HC emissions ~were reduced by 12.4 percent and 22.2
percent (LD and HD averages, respectively). Furthermore, a
durability test on a LD vehicle [23] showed that HC removal
efficiencies did not deteriorate with increased VMT; HC
reductions ranged from 12 to 54 percent, with an average of
33«5 percent (see Table A-16). The overall indication here is
that particulate traps do not force organics back into the
gaseous phase; this, coupled with the data showing substantial
decreases in SOF emissions, leads to a preliminary conclusion
that the number of cancer-causing organics being released to
the atmosphere will most likely be significantly reduced with
the use of a trap.
In summary, SOF removal efficiencies were substantial in
all cases, although generally lower than overall particulate
removal efficiencies. Related to this, data indicates that
soluble organic material as a percentage of total particulate
was slightly higher after the trap than before. Further
examination.. of the . SOFwill.,,,c,oj}s..i.de.r . changes in. bior activity,.
• -> r s .and related 1 y, cancer-risk. . v.?.
B. Mutagenic Activity
There are various methods of assessing the cancer risks
associated with the SOF of diesel particulate matter. One of
the most widely-used methods is the Ames test, which measures
bio-activity in terms of revertants per mass of SOF tested;
when these values are converted to units of revertants per mile
or per kilowatt-hour, they are generally considered meaningful
estimates of the carcinogenic properties of the SOF. A second
method of estimating cancer risk is to examine the temperature
distribution of the SOF; the focus, with respect to
carcinogenicity, is placed on the heavier hydrocarbons (three
or more benzene rings), which require higher temperatures to
vaporize. A final indication of cancer-risk is the measure of
benzo-a-pvrene (BaP) emissions; this poly-nuclear aromatic
hydrocarbon is a known human carcinogen. However, it is well
-------
5-18
known that BaP represents only a minor fraction of the
potential, carcinogenicity of diesel particulate; therefore, a
change . in the concentration of this one compound may not
indicate a similar change in overall carcinogenic potency.
Ames mutagenicity test data both with and . without a
non-catalyzed trap -were available for one light-duty diesel
vehicle and one heavy-duty diesel engine.[27,25] in general,
the number of revertants per mile or per kilowatt-hour (LDDV
and HDDE, respectively) was lower with the trap in -place; the
average reduction for LDDVs was 7.5 percent, while the value
for HDDEs was 39.1 percent. The reductions in total
particulate mass were _72._and. 89 percent, respectively. Thus,
the trap removed revertants. 10 and 44 percent as efficiently as
it removed total particulate mass.
The actual number of revertants per mass of SOF was found
to increase with the use of a trap; light-duty bio-activity
increased by an average of 113 percent, while the heavier
engine had an increase of 170 percent. (See Tables A-17 and
A-18 for the Ames test data on LDDV and HDDE,
respectively.) [27,25]
Boiling-point temperature distributions were also
available for a light-duty automobile and a heavy-duty engine.
In both cases, data supported the finding that the particulate
trap was most able to capture the heavier HCs, presumably
including the mutagenic, multi-ring hydrocarbons as well. In
other words, the "after-trap" SOF seemed to contain fewer heavy
HCs than the "before-trap" SOF samples.
Actual temperature distribution "data were not available
, toe .. the--above-mentioned . LDDV.;~; however*., cur ves for¦. -"•wi-th";- and
• "without"-trap were provided which plotted volatile particulate
mass (SOF) versus TGA temperature. [24] The "with-trap" curve
levels off at approximately 300°C, while the "without-trap"
curve continues to rise until a temperature of 500°C is
reached. Therefore, the "without-trap" sample contained more
materials with high boiling points than did the "with-trap" SOF.
Temperature data was available for a heavy-duty diesel
coach engine and is given in Table A-19.[26] This boiling
point distribution of the two SOF samples shows that the
"with-trap"* SOF has approximately the same fraction of
lower-boiling compounds as the "without-trap" sample
(discounting the initial value), but a lesser amount of
high-boiling compounds. Again, the data indicate that the trap
was able to remove some of the carcinogenic, heavy HCs being
emitted as part of the SOF.
-------
5-19
One final indicator of carcinogenic tendencies, the amount
of benzo-a-pyrene (BaP), will fc^e examined for a heavy-duty
diesel engine and an in-service coach. Data showing the change
in BaP level due to trap use are found in Table A-20.[26] As
shown, engine tests showed emissions of BaP to increase by
0-250 percent, while vehicle tests showed BaP emissions to
increase 10-175 percent with the trap. (It should be noted
that BaP is difficult to measure, and the measurements were
only quoted to one or two significant figures.)
C. Exposure to Potential Carcinogens
Diesel particulate exposure levels for the base scenario
estimated in Table 3-8 take into account only reductions (from
the relaxed levels) of total particulate mass. in order to
project cancer risk for the base scenario, the exposure figures
must be adjusted to take into account the reduction in
suspected carcinogens relative to overall particulate removal.
Table A-21 summarizes trap removal-efficiencies for the
available indicators of carcinogenic potential: SOF, mutagens,
and BaP.
The data show a wide variation between the reduction in
the three indicators of carcinogenic potential and that of
total particulate. For several reasons, the data on soluble
organic emissions were considered the most pertinent. Seven
independent studies were available and the results were very
consistent. Overall, the average ratios of SOF removal
relative to total particulate removal ranged between 0.7 and
1.0. The temperature distribution data indicate that the trap
removes the heaviest oroanics preferentially. Since the bulk
of bio-activity is believed to be associated with these heavier
organics, the reduction in SOF _rnay actually, underestimate, the.
reduction, in- bio-activity-. * - :
The little Ames test data that compared emissions with and
without trap use showed inconsistent results. The most data
was provided by a HD study on a Caterpillar engine [25] ; Table
A-18 summarizes the results. The figures calculated for the
last four modes are consistent with earlier SOF reductions;
excluding the first two modes, the ratio of reduction in
mutagenic activity with respect to overall particulate removal
ranges from 0.79-1.0. Ames test data on LD vehicles was very
limited and not very consistent (Table A-17); the average
reduction of 7.5 percent was not representative of previous
findings, and, therefore, this data was not weighted very
heavily in calculating the adjusted exposure levels.
-------
5-20
There appear to be a number of reasons not to place much
weight on the BaP data. The only BaP emissions data available
were from one HD study of a coach engine and coach vehicle.
The engine in both cases was a DDA 6V-71N, which has unique
emissions characteristics and has already been replaced by the
6V-92TA or 8V-92TA in transit buses. Also BaP only accounts
for a. very small fraction of the overall bio-activitv. Given
these factors plus the inconsistency between the BaP results
and all the other data, very little weighting should be given
~to this'data in determining new exposure levels.
In ^ summary, the reductions in SOF emissions were
~conside~red^ the most representative, and, therefore'7~'the" highest
weighting "was "given to" results" from these tests. "" in view of
added support from the Ames test results on heavy-duty vehicles
and the temperature distribution data, it appears that the
reductions in SOF emissions should be indicative of a reduced
cancer-risk. However, since removal efficiencies for the SOF
are 70-100 percent of that for total particulate, a factor of
0.7 to 1.0 will be used to adjust the base scenario exposure
levels from Table 3-8. The adjusted exposure levels are shown
in Table 5-5.
V. Estimated Risk 3ased on Projected Diesel Exposure
• ' The range of potency estimates for diesel particulate
derived in Section III can be combined with the adjusted
scenario-specific particulate exposures from Section IV to
yield estimates of the individual lung cancer risk due to
diesel particulate in 1995. After this has been done, these
individual lung cancer risk estimates will be compared to
-.cancer..and accidental risks from, other sources.
A. Scenario-Specific Individual Lung Cancer Risks
The population exposures to diesel particulate from both
light- and heavy-duty vehicles in 1995 were derived in Chapter
3 for four scenarios: 1) best estimate diesel sales with the
relaxed control scenario, 2) best estimate diesel sales with
the base control scenario, 3) worst case diesel sales with the
relaxed control scenario, and 4) worst case diesel sales with
the base control scenario. Subsequently, in this chapter, the
exposures for the base" scenarios were adjusted to reflect
reductions in carcinogens with respect to total particulate
removal.
The potency estimates of Table 5-4, based on the linear
nonthreshold extrapolation model, only require the annual
average individual exposure to obtain estimates of annual
average cancer risk per individual. The projected nationwide
-------
5-21
Table 5-5
Individual Diesel Cancer Risk Projections in 1995
Scenar io
Best Estimate Sales
Relaxed " Base
Worst Case Sales
Relaxed Base
Projected Individual
Diesel Particulate
Exposure in 1995
(ug/m3)
Light-Duty
Heavy-Duty
1.8
3.2
1.5
1.6
3.7
3.7
2.9
1.9
TOTAL
5.0
3.1
7.4
4.8
Adjusted Exposures
Based on Ratio of
Carcinogen vs. Total
Particulate Removals
with Particulate Trap
(base scenario)
Light-Dutv 1.8 1.5-1.6 3.7 2.9-3.1
Heavy-Duty 3^2 1.6-2.1 7.4 1.9-2.4
TOTAL 5.0 3.1-3.7 7.4 4.8-5.5
Estimated Individual
/• • Risk - 3ased' on Ad-.- ... .' 77 ;;i4'.-..."-r. ..
justed Diesel Par- 9
ticulate "xoosures
in 1995 X 106
(lung cancer risk/
person-year)*
Light-Duty 0.5-2.5 0.4-2c2 1.0-5.2 0.8-4.3
Heavy-Duty 0.3-4.5 0.4-2.9 1.0-5.2 0.5-3.4
TOTAL 1.3-7.0 0.8-5.1 1.9-10.4 1.3-7.7
Individual lung cancer risks in 1995 were obtained by
multiplying the adjusted individual diesel particulate
exposure in 1995 for each scenario by the range of potency
estimates for diesel particulate (0.26 x 10"® - 1.4 x
10"® risk/person-year-ug/m3).
-------
5-22
annual average exposure levels for individuals living in urban
areas in 1995 for each scenario, expressed in terms of
micrograms per cubic meter, are found in Table 5-5. These
exposure estimates are then simply multiplied by the range of
individual potencies, expressed as lung cancer risk per
micrograms per cubic meter per year, to obtain the range of
estimated individual lung cancer risk in 1995 due to diesel
particulate exposure under each scenario.
The resultant individual lung cancer risks in 1995 for
each scenario are also shown in Table 5-5. Individual lung
cancer -risks.. in- 199'5 due -to—exposure to particulate from both
-lights- and heav-y--duty. diesels range- from 0.8 x 10-6 to 7.7 x
10~6 under the base control scenarios and 1.3 x 10"6 to
10.4 x 10"® under the relaxed control scenarios.
As can also be seen from Table 5-5, the relative
contribution of LDD emissions is much greater assuming worst
case diesel sales than best estimate sales. Also, the
individual lung cancer risk is reduced by roughly 27-38 percent
under the base scenario relative to the relaxed scenario. The
effect of the base scenario is greatest with respect to the HDD
contribution.
B. Comparison of Diesel Cancer Risk with Other Risks
To olace these estimated cancer risks in perspective, they
can be compared to current (generally 1981) individual risks
from other sources. The other individual risks provided for
comparison include commonplace (accidental) risks of
death[28-30], most of which would be considered involuntary
(unavoidable) , -and - cancer - risks --from- exposure to " various
sources."[ 30-321 Also included" is the risk of death from lung
cancer for smokers whose deaths are attributable to smoking,
along with the risk from lung cancer for the General population
whose deaths are attributable to causes other than
smoking.[33] These risks, expressed as individual cancer risk
or probability of death per year, are given in Table 5-6.
Accidental risks are generally applicable to the entire
U.S. population. As can be seen in Table 5-6, the aggregate
risk for tornadoes, floods, lightning, tropical cyclones and
hurricanes is within the same order of magnitude as that given
for diesel particulate. In contrast, the risks of not wearing
seat belts, burns, drowning and motor vehicle accidents all
exceed the risk projected for exposure to diesel particulate.
The risk of a motor vehicle accident is more than an order of
magnitude greater than the maximum risk estimated for diesel
particulate.
-------
5-23
Table 5-6
Comparison of Risks from Various Sources*
Sources of Risk
Diesel Particulate:
Best Estimate Sales:
Relaxed Scenario
Base Scenario
Worst Case Sales:
Relaxed Scenario
Base Scenario
Commonplace Risks
Motor Vehicle Accident[28]
Not Wearina Seat Belts[29]
Drowning[28]
Burns[2 8]
Tornados, Floods, Light-
ning, Tropical Cyclones
and Hurricanes[30]
Estimated Risk
(r isk/oerson-vear)
1.3 x 10-6 - 7.0 x 10-6
0.8 x 10-6 - 5.1 x iq-6
1.9 x 10-6 -io.4 x 10-6
1.3 x 10-6 - 7.7 x 10-6
222.0
112.0
26.0
21.0
2.0
x 10-6
x 10-6
x 10-6
x 10-6
x 10-6
Exposed
Populat ion
Urban U.S
Entire U.S.
Entire U.S.
General U.S
Entire U.S.
General U.S
Cancer Risks
Natural Background Radi-
ation (sea level) [30]
Average Diaqnostic Medical
X-Ravs in the United
States [30]
Frequent Airline Passenger
(4 hours per week
flying) [30] - -
Fo.ur . Ta b.l e s,po.o n s, P e anu t. ..
"'¦""¦"'Butter' -Per Day (due to -
presence of aflatoxin)[30]
Ethylene Dibromide[31]
One 12-Ounce Diet
Drink Per Day[30]
Arsenic[32]
Miami or New Orleans
Drinking Water (due
to presence of
chloroform)[30]
Lung Cancers:
For Smokers Due to
Smoking[33]
For General Population
Due to Causes Other
Than Smoking[33]
20.0 x 10"^ Entire U.S.
20.0 x 10"6 Widespread
10.0 x 10"6 Limited
.,. 8.0 x.,10-6. . Fairly ..
Widespread"
4.2 x 10"6 Widespread
2.6 x 10"6 Widespread
1.7 x 10-6 i% 0f rj.s.
1.0 x 10"6 Southern •
U.S., Urban
Entire U.S.
419.0 x 10-6
73.9 x 10-6
In some cases, an average lifetime of 76.2 years was
~J ¦% 1 t f^ima rielf an Annual risk.
-------
5-24
In addition to the accidental risks discussed above,
cancer risks which result from dietary and occupational
exposures are included for comparison. These cancer risks are
roughly within the same order of magnitude as that for diesel
particulate. (The risk from lung cancer will be discussed
separately.) ExDosures to many of the cancer risks given in
Table 5-6, including the risk from diesel particulate, can be
applied across the general U.S. urban population or a vast
majority of it. Exposures to the other cancer risks such as
arsenic, or frequent airline travel, can only be applied to a
selected segment of the population. For example, only 2.82
mill.io.n people, or roughly 1 percent of. the .population are
exposed by virtue of their occupation to atmospheric-
arsenic. [32] Thus, the number of people exposed to arsenic is
far less than those exposed to diesel particulate and the other
cancer risks whose exposures can be applied across the general
U.S. population. The number of people exposed to each source
should be taken into consideration when making direct
comparisons of risk.
In some cases, risks resulting from certain occupational
exposures far exceed those risks presented in Table 5-6. For
example, exposures- to arsenic results in an individual annual
risk of respiratory cancer as high as 180 x 10~6 for those
few workers exposed near cotton gins.[32] For ethylene
dibromide, cancers can result from both dietary and
occupational exposures. The risk from dietary exposures to
ethylene dibromide is given in Table 5-6. The occupational
risks of cancer resulting from inhalation of ethylene dibromide
vapor can be as high as 5.2 x 10"^ for citrus warehouse
laborers.[31]
The' "risk' of "lung cancer for" smokers whose deaths are
attributable to smoking, along with the risk from lung cancer
for the general population whose deaths are attributable to
causes other than smoking, are also included in Table 5-6 for
comparison. The maximum lung cancer risk given for diesel
particulate is roughly 2.5 percent of the lung cancer risk for
smokers whose deaths are attributable to smoking, and 14
percent of the lung cancer risk for the general population
whose deaths are attributable to causes other than smoking.
The analogous figures for the minimum diesel exposure are 0.2
percent and 1.1 percent, respectively. As can be seen, smoking
is the primary contributor to lung cancer deaths in the U.S.
(85 percent) .
-------
5-25
_ References
1. Answer to the Posed Question: Are the Results
Obtained in the London Transit Worker Study Sufficient to
Dismiss Any Concern Regarding the Potential Cancer Hazard for
the U. Population in the Future, Due to Diesel Engine
Exhaust?, EPA Memo From Todd Thorslund, Carcinogen Assessment
Group to Michael Walsh, Mobile Source Air Pollution Control,
January 29, 1981.
2. "Potential Risk of Lung Cancer from Diesel Engine
Emissions," Harris, J., National Academy Press, Washington,
D.C., 1981.
3. "The Health of the Worker," British Journal of
Industrial Medicine, Raffle, P., Vol. 14, pp. 73-80, 1957.
4. "Trends- in Lung Cancer in London in Relation to
Exposure to "Diesel "Fumes,'" In: Health~~Ef f ects of Diesel Engine
Emissions: Proceedings of an International" Symposium, Waller,
R., Vol. 2, EPA-600/9-80-057b, 1980.
5. "Lung Cancer and Occupational Exposures to Diesel
Exhaust: A Pilot Study of Railroad Workers," Schenker, M. B.,
T. Smith, A. Munoz, S. Woskie, and F. Speizer, Draft Submitted
for Publication, 1982.
6. "A Suggested Approach for the Calculation of the
Respiratory Cancer Risk Due to Diesel Engine Exhaust',"
Presented at the EPA Workshop on the Evaluation of Research in
Support of the Carcinogenic Risk Assessment for Diesel Engine
Exhaust, Thorslund, T. W., February 24-25, 1981.
7. "Mutagenic and Carcinogenic Potency of Extracts of
Diesel and Related Environmental Emissions: Study, Design,
Sample Generation, Collection and Preparation," Environ.
International, Lewtas, J., R. L. Bradow, R. H. Jungers, B. D.
.Harris R .^,B.-. .. Zweidinger r . .K M . Cush-ing, ,B E. ,-Gill and . R.». E
-Albert ;-:Vol: < 5, pp • -383"-387, ~ 1981
8. "An Epidemiological Study of Exposure to Coal Tar
Pitch Volatiles Among Coke Oven Workers," Journal of Air
Pollutant Control Association, Mazumdar, S., C. K. Redmond, W.
Sollecito, and N. Sussman, Vol. 25, pp. 382-389, 1975.
9. Presentation at OSHA Hearings on Coke Oven
Standards, Land, C. E., 1976.
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5-26
1(L_ "Inhalation of Benzo-a-pyrene and Cancer in Man,"
Ann. NY Acad. Sci. , Hammond, E. D., I. J. Selikoff, P. L.
Lawther, and H. Seidman, Vol. 271, pp. 161-124, 1976.
11. "Cigarette Smoking and Brochial Carcinoma: Dose and
Time Relationships Among Regular Smokers and Lifelong
Non-Smokers," vJ^ Epidemiol. Community Health, Doll, R. and R.
Peto, Vol". 32, pp. 303-313, 1978.
12. "Smoking and Health: A Report of the Surgeon
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Publication No. (PHS) 79-50066.
13. "Quantitative Relationship Between Cigarette Smoking
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Vol. 28, pp. 3, 1968.
14. "The Dorn Study of Smoking and Mortality Among U.S.
Veterans: Report on Eight and One-Half Years of Observation,"
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Inst¦ Monogr, Vol. 19, pp. 1, 1966.
15. "Potential Health and Environmental Effects of
Light-Duty Diesel Vehicles II," Cuddihy, R. G. , W. C. Griffith,
C. R. Clark, and R. O. McClellan, Lovelace Biomedical and
Environmental Research Institute, Inhalation Toxicology
Research Institute Report LMF-89, 1981.
16. "A Comparative Potency Method for Cancer Risk
Assessment: Application to Diesel Particulate Emissions,"
Albert, R. E. , J. Lewtas, S. Nesnow, T. W. Thorslund and E.
Anderson, Submitted to Risk Analysis, 1982.
17. "Final Report on the Study of Diesel Particulate
Traps at Low Mileage," Landman, L.C., and Wagner, R.D., U.S.
EPA, OMS, ECTD, August 1983.
- 'i'8 r—"^'T-he "Ef £ec-£---b f "Alumina-Goat ed " Met a 1 " Mesh Filter on
the Mutagenic Activity of Diesel Particulate Emissions,"
McMahon, M.A., et. al., Texaco, Inc., SAE Paper No., 840363,
March 1982.
19. "Analysis of Particulate and Gaseous Emissions Data
from In-Use Diesel Passenger Cars," Hyde, James D., et. al..
New York State Department of Environmental Conservation, SAE
Paper No. 820772, June 1982.
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5-27
20T "Characterization of Automotive Emissions by
Bacterial Mutagenesis Bioassay: A Review," Claxton, Larry D.,
U.S. EPA, GTD, EPA-600/J-83-096, 1983.
21. "Assessment of Technologies for Determining Cancer
Risks from the Environment," Office of Technology Assessment,
June 1981.
22. "Diesel Exhaust Treatment Devices: Effects on
Gaseous and Particulate Emissions and on Mutagenic Activity,"
Gorse, Florek, Young, Brown, and Salmeen, Ford Motor Company.
23. "Diesel Car Particulate Control Methods," Urban, C.
(Southwest Research Institute), Wagner, R. and Landman, L.
(U.S. EPA)., SAE Paper No. 830034.
24. "Effect of Operating Conditions on the Effluent of a
Wall-Flow Monolith Particulate Trap," MacDonald, J., GM, SAE
Paper No. .831711, November 1983.
25. "Study of Aftertreatment and Fuel Injection
Variables for Particulate Control in Heavy-Duty Diesel
Engines," Michigan Technical University, U.S. EPA,
November 1982.
26. "Emission Characterization of a 2-Stroke Heavy-Duty
Diesel Coach Engine and Vehicle With and Without a Particulated
Trap," Southwest Research Institute, U.S. EPA, May 1983.
27. "Study of the 1985 Light-Duty Diesel Particulate
Standard," submitted to U.S. EPA by Ford Motor Company on
October 2, 1981 (EPA Docket A-81-20, II-3-24).
28. The World Almanac and Book of Facts 1983, New York,
New York, 1983.
29. "Rediscover the Safety Belt", U.S. Department of
-Transportation; Nat-ional" Highway* Tra-ff-ic Safety Administration,--
30. Risk/Benefit Analysis, Wilson, R. , and E. Crouch,
Cambridge, Massachusetts, 1982.
31. "Ethylene Dibromide: Position Document 2/3",
Special Pesticide Review Division, Environmental Protection
Agency, EPA/SPRD-81/74, 1980.
32. "Final Risk Assessment on Arsenic," Carcinogen
Assessment Group, Environmental Protection Agency,
EPA-600/6-81-002, May 1981.
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5-28
33^ Estimates for total lung cancer deaths in 1981
obtained from the National Center for Health Statistics,
Department of Health and Human Services. Percentages of lung
cancer deaths attributable to smoking and other causes obtained
from Clearinghouse on Smoking and Health, 1982 Report on
Smoking and.Health.
-------
CHAPTER 6
NON-CANCER HEALTH EFFECTS OF
DIESEL PARTICULATE
I. Introduction
One of the primary concerns regarding diesel particulate
is its potential for adversely affecting human health. The
potential adverse health effects of this material can be
divided into two broad categories: 1) carcinoaenic and 2)
non-carcinoqenic, or non-cancer. This chapter deals
specifically with non-cancer health effects. The potential
carcinoaenic effects of diesel particulate were already
discussed in Chapter 5.
Althouah a large amount of information documenting the
adverse health effects of inhaling particulate matter is
available in the literature, comparatively little deals
specifically with diesel particulate. However, concern over
the potentially adverse health effects of exposure to diesel
exhaust has recently increased, and has resulted in a
sianificant amount of new research concerning diesel
particulate and its effects on health.[1,2] Unfortunately,
because much of the diesel particulate health effects
information which is available is comparatively recent and has
not been peer reviewed by other scientists, very few conclusive
statements can be made regarding the health effects of diesel
particulate exposure.r 31 Therefore, at this time, the best
aporoach for evaluating the non-cancer health effects of diesel
oarticulate is to evaluate the health effects of particles for
which established literature is available. However, before
outlining how this comparative analysis will be ( per formed, it
is important to describe three things this analysis will not do.
First,'the fact ""that particles in ~ the'- ambient air can
cause adverse non-cancer- health effects will not be established
here. It has long been recognized that exposure to various
forms of particulate matter can cause a wide variety of adverse
non-cancer health effects. These effects have been well
documented in the literature and total suspended particulate
matter was among the first airborne pollutants to have a NAAOS
established by EPA in 1971.
Second, in evaluating the documented non-cancer health
effects of particulate matter, the focus will not be on any
speci.fic tvoes of particulate, but rather on typical ambient
mixtures of particles. Obviously, some types of particulate
affect health differently than others. For example, soluble
particles may affect health through different mechanisms than
insoluble particles. Some specific Darticles also are
inherently more dangerous than others (e.g., radioactive
material). However, because it is generally imoossible
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6-2
epidemiolo.qicallv to ascribe the adverse health effects of
ambient- exposures to any specific component of the particulate
mixture, the effects of specific particles are less important
than the effects of typical mixtures of particles found in the
atmosphere.
Third, ..this . ..comparative analysis will not be conducted
quantitatively, but qualitatively. While a few quantitative
health effects studies based on measurements of total suspended
particulate or British smoke shade are available, the
extrapolation of these results to diesel particulate could only
be,..based on.. Qualitative .relationships, and., the. quantitative,
"results would imply a degree of precision beyond that which was
defendable.
Proceeding to the description of what will be done, the
comparative analysis will be performed on two levels:
particulate inhalation characteristics and laboratorv health
effects testing. The available information on each of these
levels will be presented first for ambient inhalable
particulate and second for diesel particulate, with a
comparison of the two sets of results following on each level.
An overall asessment will then be made as to whether or not
diesel Darticulate should be expected to affect health
(non-carcinoqenicallv) disproportionate to its impact on
ambient mass particulate levels.
II. Mon-Cancer health Effects of Typical Particulate Matter
A. Inhalation of Particulate Matter
.r-"iu-0.ne^o£> th.e~.most ea.s.ily. -unde.r-.sfeo.od^.de'tetrmi-nants.. "O-f- .ard verse*—
health e f fects-• from Mnha-li-nq-"par trcu'late ~;:matter ; i's~ the '"body'"
dose." For the purposes of this chapter, the important aspects
of body dose are: 1) where particles are deposited in the
respiratory tract, and 2) how these particles are cleared from
the system by natural defense mechanisms. Therefore, some
qeneral knowledge reaarding the structure of the respiratory
tract, in addition to deposition and clearance within the
system is a prerequisite for specifically discussinq the
non-cancer health effects of particulate exposure.
^he Principal features of the respiratory system are
depicted in Fiaure 6-1. The upper respiratory tract begins
with the nares (or mouth during oral breathina) and ends at the
entrance to the trachea. The lower respiratory tract is
subdivided into the conducting airways (or tracheobronch ial
region) and the aas-exchanae region (or alveolar reqion). The
tracheobronchial region consists of the trachea down to the
minute terminal bronchioles. The alveolar region includes the
partially alveolated bronchioles and finally terminates with
the alveoli themselves. (A more complete description of the
respiratory tract as it relates to particle deposition can be
-------
6r3
Figure 6-1/
Diagrarnratic Pepresentati.cn of the
Human Upper and Lc^er Pespiratory Tract U)
UdMr rndtrto/v met
Anttf*or n*r«
-»r
-------
6-4
1. Deposition in the Respiratory Tract
^s stated above, the health effects associated with
particulate matter in the respiratory tract are dependent, to a
"large degree, upon 'where in the tract deposition takes place.
Spatial deposition within the respiratory system is primarily
determined by particle size, with the mode of breathing (nose
versus mouth) also havino a substantial effect on the
disposition of large particles.-
Moving through the respiratory tract, deposition in the
upper- respiratory tract -during nose breathing is nearly 100
percent complete for particles with diameters larger than about
10 micrometers and declines to about 10 percent for particles
with diameters less than 1 micrometer.[5] Durino mouth
breathina, deposition in the upper respiratory tract is less
efficient, althouch the vast majority of large particles are
still removed in this region.
Most particles smaller than about 10-15 micrometers enter
the lower respiratory tract and are deposited, to varying
degrees, in the tracheobronchial and alveolar reaions as shown
in Figure 6-2. In the tracheobronchial region, deposition
during mouth breathing is especially hiah for particles with
diameters of 5-10 micrometers (up to 80 percent removal) and
tapers ' off. "to" a deposition of about 5 percent for particles
with diameter's" ~ "of 0.1-1 micrometers. Deposition of 5-10
micrometer particles in this reaion during nose breathing is
considerably less due to their previous deposition in the upper
respiratory tract.
i-"depbsi;t"i'on i's\- a'lmo's't • nonexiste~h~t
"for pa'rticles"with diameter's "qreater than™ about 16 micrdmeteYsV
since nearly all such large particles already would have been
deposited in the upper respiratory tract and the
tracheobronchial reaion. Deposition in the alveolar region
during mouth breathing peaks at about 65 percent for particles
with diameters of 3-4 micrometers and declines to around 15
percent for particles with diameters between 0.1-0.2
micrometers. This peak is still present durina nose breathing,
but it's level is much less (25 percent). Generally, this
information shows that particles with diameters less than about
10-15 micrometers generally penetrate deeper into the
resDiratory system than laraer particles.
2. Clearance of Particulate Matter From the Respiratory
Tract
Clearance is the process whereby particles are removed
from the respiratory tract. This process is described in this
section in a simplified manner. It must be noted, however,
that the mechanisms for removing particles are often complex
and the efficiencies of these mechanisms often vary
-------
Fi'gura 6-2(6,7]
Deposition- in ths Trachecfarondhial
and Alveolar Bagicra
3y Indicated. ?articla r>< ^.r
I 1 i - • i
Rang® of alveolar deposition
couth breaching
Estiaate of alveolar deposition
nose breathing
Rang® of tracheobronchial deposition
mouth breathing. fj>] *
Extrapolation of above to point
predicted by Reference 4
Extrapolation to point
denor.straced by Reference
- XXXXX.X
ftooocxxxxjoaooot
0.1 0.2 o.n 0.4 o.s
PHYSICAL OlAMSTSfl, j;n»
1.0 :,0 1Q 4.0 5.0
AenoovNXMic cumst»s,
Wal Deposition is expressed a3 fraction of particles of a given diameter
entering the south (or nose).
lb] Tr*che®bioachial deposition during nose breathing likely would be less
than that depicted for mouth breathing.
-------
6-6
smoking, pathological abnormalities, and response to inhaled
pollutants. A more complete description of respiratory
clearance is available in Referenced.
Particulates may be removed from the respiratory tract in
two principal ways. First, particles which are soluble in body
fluids (or the soluble coating on insoluble particles) mav
dissolve in any reaion of the respiratory system where
deposition occurs. After dissolution, the constituents of the
particle may interact locallv with cells or tissues, or they
may be absorbed into the blood and transported to other areas
of the body. ; . _ . . .. -
Second, relatively inert and insoluble particles may be
removed from the respiratory tract by more mechanical means.
The process is somewhat specific to the various regions of the
system; therefore, each region is discussed separately.
Clearance of insoluble particles from the anterior portion
of the upper respiratory tract takes place mainly by blowing
the nose or sneezing. In the posterior portion of this region,
the conducting airways are lined with both ciliated cells that
have hairlike projections and mucus-secreting cells. Particles
that are deposited in these conducting airways are trapped in
the mucus and are mechanically transported by cilia action to
the throat, where they are either swallowed, entering the
qastrointestinal tract, or expectorated. This clearance
mechanism is called the "mucociliary conveyor." Clearance in
the upper respiratory tract is normally rapid (i.e.,
minutes) . [61
.. The -pr-ima.ry----. clearance- --mechan.tsm- vin---.the - tracheobroncial
region i's also' the mucociliary conveyor. As described above,5,
entrained particles are transported "to the throat where they
mav be swallowed, thereby entering the gastrointestinal tract,
or expectorated. Smaller Darticles, which may deposit in the
smaller airways deeper in the luna,- take longer to clear than
larger particles, which tend to deposit in the larqer airways.
Generally, however, clearance from the tracheobronchial region
of the respiratory system normallv takes hours to days.[6]
The principal clearance route in the alveolar region is
via alveolar macrophages. These specialized cells phaaocytize
(i.e., engulf) deposited particulate matter. Some macrophages
containina particulate travel to the mucociliary conveyor of
the tracheobronchial reaion where they are cleared through the
aastrointestinal tract. Others travel to lymph nodes and are
cleared from the body throuah the lymphatic system. Clearance
of insoluble particles from the alveolar region generally takes
months or years.[6]
-------
6-7
3. Related wealth Concerns
There are two principal concerns associated with the
deposition of inhalable particulate in the lower respiratory
tract. First, particles deposited in this area, even if not
directly toxic themselves (e.g., inert particles), may have
hazardous materials adsorbed onto their surfaces.
Conseouently, these adsorbed, hazardous materials may be
transported deep into the most sensitive areas of the lung
where they may cause localized effects or be absorbed and
circulated to other parts of the body, causing problems
elsewhere. Second, all particles deposited in this area have
relatively long residence times. As discussed previously,
clearance of particles in the tracheobronchial region may take
days, while in the alveolar region it may take years to clear
insoluble particles. These long residence times provide a
greater ODportunitv to generate health problems even if toxic
materials are not present. Both of these concerns have led
FPA's Office of Air Quality Planninq and Standards to recommend
that a NAAOS be established for particulate matter with
diameters of 10 micrometers or less.[6] Therefore, the
particles in the ambient air which are associated with the
effects of concern have two aeneral characteristics: 1)
chemical constituents that are soluble in body fluids, and 2)
diameters of 10 micrometers or less.
"'hese general characteristics of typical particulate
matter that cause adverse non-cancer health effects are
imDortant later in this analysis, since the greater the
similarity between this particulate matter and diesel
Darticulate, the strongej: the inference that diesel particles
.can-.'^a 1 so.£ay'se adye.r.ie ;health;.^4;f,fKc^ts:.The .key,,..points,.. ,,tp..
remember are:
1. Deposition in the respiratory system is
particle-size dependent,
2. Smaller particles with diameters less than about.
10-15 micrometers are transported into the deepest portions of
the respiratory system (tracheobronchial or alveolar reqions)
where they reside for lona periods of time (hours to years), and
3. within this subset of inhalable particles, some
particles are deposited in greater amounts dependinq on their
diameter and the heiahts and breadths of these peaks are
dependent on the mode of breathing (mouth versus nose).
B. Effects of Particulate Deposition in the Lower
Respiratory Tract
As stated in the previous section, the deposition of
inhalable particulate in the tracheobronchial and alveolar
reqions of the respiratory tract pose the greatest threat to
-------
6-8
1. Reduced lung function,
2. Aqaravation of • existina respiratory disease
(especially for bronchitics and asthmatics),
3. Increased infectious disease, and
4. Predisposition to the development of bronchitis. [61
In the alveolar region the effects of concern include:
-- — 1. " Reduced lung function, ' ~ "
2. Damage to lung tissues,
3. Increased susceptibility to infection, and
4. Aggravation or predisposition to cardiopulmonary
d iseases.f 6]
These effects have been observed to varying degrees- in
laboratory and epidemiological studies. Because of individual
variation and limitations in analytical methodologies, it is
difficult to tell at what particulate concentrations these
effects begin or become significant. Presently, many of these
effects do not appear to have clear thresholds.[6]
The exact causes of many of the above non-cancer health
effects are not well known, but the following mechanisms or
responses are generally involved either singly or- in
combination : _[_5 , 6J_. . .
1-. Macroohage damaae due to physical overloading- with
particles or because of a toxic response to chemicals adsorbed
on Darticles;
2. Excess mucus secretion causing a reduction in the
flow rate of the mucociliary conveyor;
3. Structural changes in the lung tissue due to
physically or chemically induced damage; .
4. Deposition of particles in excess of the lung's
clearance ability with an attendant build-up of particles; and
5. Bronchioconstriction of airwavs due to the
stimulation of nerves in the tracheobronchial region.
while the health effects listed above are a step closer to
overall human health than the lung functions (mechanisms) just
described, it is the list of mechanisms which will be most
useful below in assessing the relative potency of diesel
n?r)-irii1 St.p T'Viprp «i 1'Tinl V r>ot" i"" Pi I' (71"1 n** f- p pf fprf O *
-------
6-9
diesel particulates on the tyDes of health effects listed
above. while the amount of available data on the effect of
diesel particulate on lung function is also less than
desireable, it is areater than that on health effects and will
provide the basis for comparison below.
IIT. Non-Cancer Health Effects of Diesel Particulate Matter
A. Inhalation of Diesel Particulate
Concerns regarding the health effects of ambient exposures
to diesel particulate were first based on its physical and
chemi'cal characteristics.1 The particulate" matter from diesel
engines is composed of basic units which are 0.1 micrometer or
less in diameter.[81 These units form agglomerates with
diameters ranaing up to a maximum of about 1 micrometer. Most
of the agglomerates, however, are significantly smaller than 1
micrometer in diameter (90 percent by mass) , with about 50
percent by mass being 0.3 micrometer or less.[8,9,10] The
small size, of diesel particulate means that it is deposited in
the lower respiratory tract, where clearance may take years.
Also important is the fact that the basic particulate unit
is composed of a carbonaceous core with a wide variety of
organic compounds adsorbed onto its surface. while at least
one study specifically identified 70 organic compounds
associated with diesel particulate, [8] the great majority of
the individual compounds remains unknown. Such chemical
constituents could react locally with the cells or tissues of
the lung, or be transported to other areas of the body.
These are the same general . character isties .. that . . wepe
-TdePrtlfied--- above for "typical inhalable particles. Therefor-e-^
based solely on the inhalation characteristics of diesel
particulate, it is loqical to expect that exposure to diesel
particulate could cause the same adverse non-cancer health
effects as other inhalable particulate.
B. Effect of Diesel Particulate Deposition in the Lower
Respiratory Tract
This inhalation-based connection between inhalable
particulate and diesel particulate has fostered research
specifically aimed at understanding the non-cancer health
effects of exposure to diesel particles. The results of this
research can be used to resolve two issues which are of
paramount concern. First, does diesel particulate actually
elicit the same adverse effects or responses that were
described above for inhalable particulate in general, as would
be expected based on the similarities between the particles?
Second, is exposure to diesel particulate disproportionately
more hazardous than would be suggested by its contribution to
the concentration of inhalable particulate suspended in the
-------
6-10
ambient atmosphere because of its deep lunq deposition and
adsorbed chemicals? More specifically, is the potency of
diesel particulate and the mixture of inhalable particulate in
the ambient air significantly different, so that any increase
in diesel particulate beyond current levels would be especially
hazardous? These two questions are discussed separately
because one issue can be resolved more conclusively than the
other at this time; the first question in this section and the
second in the next.
Two types of studies which specifically deal with diesel
-emissro"ns"~~aTe most ~ useful ~ ~ in ~ answer ina e'lther" of" these
questions: epidemiological-" and laboratory. Before the
findinas of these studies are presented, it should be noted
that most of this research has already been compiled or
reviewed in References 3, 11, and 12. Because of this, only a
brief overview of the literature will be presented here.
The epidemiological research into the non-cancer health
effects of diesel particulate exposure is extremely limited.
There are no studies which . specifically evaluate- diesel
particulate. Only a very few studies evaluate diesel exhaust,
and diesel particulate by association. The primary reason for
this is the lack of suitable populations available for study.[1]
Some of the studies that have been completed suggest that
occupational exposure to diesel exhaust (e.g., railroad,
transit, mining workers) results in a higher prevalence of
chronic respiratory symptoms, bronchitis, and loss of lunq
function. [3] Other studies have shown no significant adverse
_effects between "groups_ ^ of _ expo_sed .a.nd _ . unexposed,.
'lo'dfvTdu'a 1 s-^.['3]''"J" TKeiref"ore', aTthough J *'1*. the...; .. J:ayai'llablet
epidemiological studies suggest that chronic exposure to diesel
exhaust, including diesel particulate, may adversely affect
health, the results are inconclusive. Because of this, no firm
conclusion regarding the health effects of diesel particulate
can be made based on this type of information. Thus, the
results of laboratory studies must be examined to better
determine the effects of diesel particulate exoosure.
Most laboratory investigations of diesel particulate
exposure have been conducted at hiaher particulate
concentrations than normally would be encountered in the
natural environment. This is common practice in such studies
and is done to reduce the cost of such research. Because of
the hiah exposures used in these studies, they are very useful
in identifying the mechanisms or responses that would account
for the effects of concern that are observed in the "real
world" (e.g., bronchitis and infectious disease). However,
they are less useful for identifying health effects that will
occur at realistic exposure levels.
-------
6-11
Most of the laboratory studies involvinq diesel
particulate have shown, to varying degrees, the same basic
effects on lung function that were oreviously described for
inhalable particulate matter, including alveolar macrophage
damage, excess secretion of mucus, lung tissue damage, possible
adverse effects on the immune system, and particle buiid-up in
the luna.f3,11,12] This similarity of response provides strong'
evidence that exposure to diesel particulate has the potential
to elicit many of the - same adverse health effects which were
also previously described for inhalable particulate in
general. Therefore, the original concerns regarding diesel
particulate that were based simply on its inhalation
characteristics are supported by more recent direct evidence.
C. The Hazard of Diesel Particulate Relative to General
Inhalable Particulate
The issue of diesel particulate's relative hazard is a
more difficult issue to resolve. As discussed above, the few
quantitative epidemiological studies are not useful to
characterize the non-cancer health effects of diesel
particulates because their results are inconclusive. Mso, the
use of verv high particulate concentrations in the laboratory
studies generallv precludes using this research to evaluate the
health risk of ambient exposures to diesel particles in
comparison to that associated with the ambient mixture of
particles. Nevertheless, some studies have investigated the
systemic toxicology of diesel exhaust. Such studies are
particularly useful in evaluating the concern that the organic
chemicals adsorbed on. the surface of diesel particulate may
make it disproportionately more hazardous than other
particulate- in 'the ambient mixture.' •• . i.
Generally, the results of these studies have not
demonstrated any sianificant gross toxicoloaica1 effects from
exposure to diesel particulate. [8] A possible explanation for
this lack of effect is that other research has suggested that
although the organic layer of diesel particulate is soluble in.
body fluids, it may be released very slowly and that enzyme
systems in the lungs may metabolize these chemical
consitituents into more innocuous substances.fi] Therefore,
this information suggests that the organic layer of diesel
particulate may not cause significant non-carcinogenic
toxicological effects. Until more information is generated,
however, the possibility that diesel particulate may be
disproportionately more hazardous cannot be dismissed.
Information concerninq the efficiency with which particles
of various sizes are deposited in the lower respiratory tract
may also provide some insiaht into the relative hazard of
diesel particulate. It was previously stated that almost all
diesel particulate is smaller than 1 micrometer in diameter.
-------
6-12
Figure 6-2 shows, for example, that the deposition for these
sized particles in the alveolar region during mouth breathing
is substantially less than for particles with diameters of 1-6
micrometers. (The effect is present, though less dramatic, for
nose breathing.) Therefore, particles in the ambient air which
are somewhat larger than diesel particulate may pose a slightly
greater health hazard on the basis of mass deposited in the
lower respiratory tract. This suggests that, on a mass
concentration basis alone, diesel particulate may not be more
hazardous than would be accounted for by its contribution to
the total ambient mixture of inhalable particulates, and that
it could be slightly less hazardous, than certain larger, though
still inhalable, particulate. Here again, however, the
information is simply too limited to make any conclusive
judgments.
IV. Summary and Conclusions
Based on the available health effects and deposition
studies, there is no direct evidence that diesel particulate is
disproportionately more potent in causing non-cancer health
effects than an equivalent mass of the current ambient mixture
of particles. However, this information is so limited that it
does not provide a sufficient basis for conclusively
eliminating the concern that diesel particulate may be more
hazardous because of its chemical composition and deep lung
deposition. Therefore, the issue of diesel particulate's
relative hazard cannot be fully resolved at this time. Ongoing
research may shed more light on this issue in the future.
The following overall conclusions regarding the non-cancer
'health -e-ff-ects of • diesel-part-iculate- are possible,- based' on th.e
information summarized above. - - - • "~
1. Laboratory studies have shown diesel particulate
matter has the potential to cause or contribute to adverse
health effects such as reduced lung function, damage to lung
tissues, increased suceptibility to infection, aggravation of
existing respiratory disease, predisposition to bronchitis, and
aggravation of or predisposition to cardiopulmonary disease.
2. There is insufficient evidence to conclusively judge
whether diesel particulate is or is not more hazardous than the
mixture of various particles suspended in the ambient air with
diameters of 10 micrometers or less (i.e., inhalable
particulate). The very limited information from health effects
and deposition studies suggests that diesel particulate may not
be more hazardous under certain conditions (i.e., mouth
breathing). However, until more data becomes available, diesel
particulate should be considered as harmful in causing
non-cancer health effects as the ambient mixture of inhalable
particles.
-------
6-13
References
1. "Inhalation Toxicology of Diesel Exhaust Particles,"
In: Diesel Emissions Svmposium Proceedings, McClellan, R., A.
Brooks, R. Cuddihv, R. Jones, J. Mauderlv, and R. Wolff U.S.
EPA, ORD, 1981.
2. "A Subchronic Study of the Effects of Exposure of
Three Species of Rodents to Diesel- Exhaust," in:' Diesel
Emissions Symposium Proceedings, Kaplan, H. L. , W. E.
Mackenzie,. J. Springer, R. M. Schreck, and J. j. vostal,
U.S. -EPA, ORD, 1981'.
3. "Impacts of Diesel-Powered Light-Duty Vehicles:
Health Effects of Exposure to Diesel Exhaust," National
Research Council, 1981.
4. "Size Considerations for Establishing a Standard for
Inhalable Particles," Journal of the Air Pollution Control
Association, Miller, ?., E. Gradner, J. Graham, R. Lee, Jr., w.
Wilson, and J... Bachman, 1979, vol. 46, pp. 610-615.
5. "Air Quality Criteria for Particulate Matter and
Sulfur Oxides (Draft)," U.S. EPA, OAQPS, December 1981.
6. "Review of the National Ambient Air Ouality
Standards for Particulate Matter: Assessment of Scientific and
Technical Information," U.S. EPA, OAOPS, January 1982.
7." American Industrial Hygiene Association," In:
Diesel Emissions Symposium Proceedinas, Chan, T. and M.
. Ltpbmah, v:ol;"4:l /ppV 3"9'9-'4'0'9;, '19807 -
8. "EPA Studies on the Toxicological Effects of Inhaled
Diesel Engine Emissions," In: Diesel Emissions Symposium
Proceedings, Pepelko, W., U.S. EPA, ORD, 1981.
9. "Characterization of Particulate and Gaseous
Emissions from Two Diesel Automobiles as Functions of Fuel and
Driving Cycle," Hare, C. and T. Baines, SAE Paoer No. 790424.
10. "Characteristics and Oxidation of Diesel
Particulate," In: Diesel Emissions Symposium' Proceedings,
Travser, D.A., L. J. Hillenbrand, U.S. EPA, ORD, 1981.
11. Diesel Emissions Symposium Proceedings, U.S. EPA,
ORD, 1981.
12. "Health Effects of Diesel Engine Emissions:
Proceedings of an Interational Symposium," Vol. 1 and 2,
Edited bv PeDelko, W., R. Danner, and N. Clark, U.S. E^A, ORD,
December 1979.
-------
CHAPTER 7
SOILING EFFECTS
I. Introduct ion
with the increased use of diesel-Dowered vehicles, the
impact of diesel Darticulate emissions on materials has become
a subject for investigation. The major material effect
associated with chemically non-reactive atmospheric particles,
such as diesel particulate, is that of material soilina.[4]
This chapter will examine the effects of diesel particulate on
so ilinq.
In t-he past, ..the vast majority of soiling studies have-
dealt with general atmospheric particulate, while little work
has been done SDecificallv on the soilino impact of diesel
particulate. However, by considering the relative
characteristics of diesel particulate, it is possible to adapt
the findings of studies addressing atmospheric particulate
soilina to diesel particulate soiling,
The soiling effect caused by increased ambient levels of
diesel particulate can be addressed in a number of waysc One
approach would be to derive three relationships: 1) a
relationship between ambient particulate levels and the
physical phenomena of soiling (i.e., particle deposition), 2) a
relationship between soiling and cleaning frequency, and 3) a
relationship between cleanina frequency and cleaning costs. By
combinina the three, a relationship between ambient particulate
levels and the cost associated with removing the soiling can be
obtained. However, with this approach intermediate
relationships are also determinable (i.e., the relationship
between particulate levels and cleanina freauencv). A second
approach- would be to- derive a single relationship between^
ambient particulate levels and the cost of soiling. ' This
latter methodology usually utilizes survevs of individuals'
intentions or actions to determine a "willinaness-to-Dav"
associated with a decrease in soiling. Deriving a relationship
between ambient particulate levels and the behavior of the
people affected by soiling is still another approach; this
approach may utilize prooertv values in its methodoloay to
determine the cost associated with a reaction to soiling.
This analvsis will not address any economic costs
associated with soiling due to the controversy connected with
the existing economic soilina analyses. Instead, this analysis
will only address the practical aspects of soiling (i.e.,
soilina as a function of particulate concentration and cleaning
(or other soiling remedy) frequency as a function of soiling).
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7-2
This restriction in scope has the unfortunate side effect
of placinq the great majority of the research addressing
atmospheric particulate soiling outside the scope of this
studv. The remaining research orimarily addresses the effect
of total suspended Darticulate (TSP) on soiling, with little
havinq been done on the effect of soiling on cleaninq frequencv
or on the soilina effects of various subclasses of TSP. No
experimental research has been conducted on soilinq by diesel
particulate.
Given this, this study will take a three-step approach to
address the issue of diesel particulate soiling. First, the
- physical process of soilina will be defined and described.
Second, studies addressing soiling by TSP will be reviewed to
assess the current state of knowledge in the area. Third,
soilinq by diesel Darticulate will be compared to that by TS?
by comDarina the ohvsical and chemical properties of both types
of particulate and oostulating their effect on soilinq. The
goal of the entire process will be to arrive at some relative
value for the soiling effect of ambient diesel particulate to
that of TSP.
II. Description of the Soiling Process
Soilinq is defined as the build-uD of a layer of deposited
atmospheric particulates on an exposed surface.[11 A soiled
surface aDpears dirty to the eye and, as the layer of deposited
particulates increases, it will become detectable by touch.
Characteristics associated with soilinq are: 1) a loss of
reflectance of visual liqht by an opaque material surface, or
2) a reduction in liqht transmission throuah a transparent
mater ial.
The time" "interval reauired to transform horizontal and
vertical surfaces from a clean to a perceptibly dirty state is
aenerallv determined bv oarticle composition and the rate of
deDosition. This Drocess is also influenced by the location
and soatial aliqnment of the material, the texture and color of
the surface relative to the particle, and meteoroloqical
variables like moisture, temperature and wind soeed.[21
The degree of soilinq is determined by measuring
reflectance from an oDaoue surface and by measurinq. haze
through a transparent surface (window qlass is the most common
transparent surface). The qreater the oriqinal reflectance of
the surface, the more observable the soilinq will be.[3] This
can easily be seen by imagininq the effects of soilinq on a
white-painted surface, which has a reflectance of more than 90
percent, as compared to the effects of soilinq on a
black-painted surface, with a much lower reflectance. Of
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7-3
course the soiling effects on a dark surface by a white or
1iaht-colbred particle is equally observable, but because
diesel particulate is dark, this is not a concern.
TIT. AtmosDheric Particulate Soilina
A small number of studies have been performed relating TSP
levels to the physical rate of soiling. This section will
briefly review four such studies. The first two studies were
experimental in nature and simply attempted to determine the
relationship between particulate concentration, time, and
soiling. The third studv used surveys and attempted to go one
steo' further bv relating pa'ffi'cie concentration to the
frequency of soiled removal (in this' case, paintina) . The
fourth studv, a literature review, identified those cleanina
tasks that would be affected by increased soiling resulting
from increased ambient particulate levels.
In the first study, Parker attempted to determine the
relationship between chanqes in the reflectance of a surface
and the accumulation of particles.fi] Reflectance changes of
white painted surfaces showed a first order dependence upon
total pollutant dosage as defined by the expression:
R = Rp + (R0 " Rp) exp (-KCt)
Where:
R = reflectance of the surface,
R0 = initial reflectance of the surface,
Rd = reflectance of particles,
K" = deposition rate constant,
0 =, particle 90nce.ntrat.ipn,...,
t = exposure time.
It is interesting to note that, if soiling is defined as
the chanae in surface reflectance (R0 - R) rather than simply
the surface reflectance (R), the above equation becomes:
Rq - R 3 (Rq - Rp)(1 - exp (-KCt))
This is the equation for exponential decay, which, among
other processes, describes the decay of radioactive materials.
The chanae in reflectance is rapid at first and slows as time
qoes on. The final reflectance of the surface approaches the
reflectance of the particulate assvmptoticallv (i.e., very
qradually). A doublinq of the particle concentration would not
affect the final reflectance of the surface, but would double
the rate of soilina. This is shown in Figure 7-1.
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7-4
In a -second, similar study, Beloin and Havnie exposed six
materials to particulate soiling. [4] A linear reqression
analysis resulted in the followina relationshins for two of the
mater ials:
1. for acrylic paint:
R0 - R = 92.5 - R = 1.36C-345t.612
2. For white asphalt shingles:
. _ • Ra - R .= 41.8 - R = .OOTacV-OO^t-59-? ..
where the units of C and t are micrograms per cubic meter and
months, respectively.
Here, soiling (R - R0) is dependent on certain powers of
both particle concentration and time. While these
relationships appear quite different from that put forth by
Harker, they are not entirely inconsistent. First, Beloin and
Havnie were actually addressing a situation quite different
from that addressed by Harker. Beloin and Haynie's experiments
and their correlations included a variety of particulate types,
all havinq different properties. warden's relation only
applies to a single type of particulate. Second, the powers
associated with particle concentration and time in the Beloin
- and "avnie eauations are all essentially between zero and one,
which is what would be expected if the process described bv
Harker was examined for a specific period of time. The fact
that the powers for concentration and time are not equal is
more of a question, as Parker's model implies they should be
-u-rJ-feh-e™s,'aTn*e-v-¦ ¦^"•oweverv- >th-e-- f a-c-t--that«- --Be^o^n;';'"a'n_df; -ay ryi'e i'nc-]?ud-ed!
¦ -—2 different"' tvpes -""-of " partrcurate 1 in"^ theiru'stui^y;" could "be ; the
explanation.
To illustrate this possibility, a portion of the data from
the Beloin and Havnie study and their equation for acrylic
paint have been reproduced in Figure 2. A specific instance of
Harker's equation was then fit to the data. As can be seen,
the two relations aaree verv well and both describe the data
adequately. Thus, while the exact form of the relationship
between soiling and particle concentration is not known, it is
clear that atmospheric particulate does result in soiling and
that an increase in particle concentration will increase the
degree of soiling, and very likely to the same degree (i.e., a
doubling of particulate will double the soiling) .
A relationship between the frequency of house repainting
and atmospheric particulate concentration was shown in the
third study by Michelson and Tourin.[51 A mailed survey of
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7-5
households in the upper Ohio River Valley established a linear
relationship between repainting frequency and ambient levels of
particulate matter. However, additional data are required to
establish a more definite correlation. Maintenance data for
additional cities should be added to the study to increase the
study size; other factors to be considered include the effects
of other pollutants that may... be present and also the
socioeconomic effects of the households in the survey.
In the fourth and final study, Watson and Jakschf61
examined the soiling literature to determine which common
household maintenance and cleaning tasks would be affected by
atmospheric particulate soiling. The Watson and Jaksch study
selected eight tasks as those most likely to be noticeably
soiled by particulates; those tasks for which there was little
or no evidence of being significantly affected by soiling were
eliminated from consideration. The eight cleaning and
maintenance tasks that would be affected by atmospheric
particulate soiling are:
Indoor Outdoor
Painting walls and ceilings Painting walls
Wallpapering Paintina trim
Washing walls Washing windows
Washing windows
Cleaning Venetian blinds
Mo attempt was made, however, to determine the dearee of the
effect that soiling had on the frequency of the performance of
these tasks; only that the effect would be significant.
Again, as was the case with the first two studies, the
usefulness of the latter two studies is limited. vo
quantitative relationship between atmosDheric particle
concentration and cleaning frequency can be drawn. However,
the evidence indicates that not only does susoended particulate
cause soiling, but soiling affects the performance of cleaning
and maintenance tasks. Thus, increased ambient particulate
levels will lead to increased soiling, which will have a cost
associated with its removal.
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7-6
IV. Diesel Particulate Soiling
The previous descriptions of atmospheric particulate
soiling refer to TSP (i.e., less than approximately 30
micrometers in diameter). Diesel particulate fa-lls into a
subclass of TSP (fine particulate, that are less than
aporoximatelv 2.5 micrometers in diameter) and both its
physical and chemical characteristics could quite likely cause
it to have soiling—properties different than those of TSP.
Unfortunately, there exist very little direct experimental data
demonstratina the relative soilina effect of fine particles or
diese-l- particulate to those of TSP. Because of this, it is-
necessary to compare the characteristics of diesel particulate
and TSP and postulate the effect of the differences on their
overall soiling impact.
The physical and chemical properties of particulate which
most affect the degree of soiling damage appear to be
reflectance, stickiness, and size. Wallin has measured the
optical reflectance of diesel particulate and found it to be
generally about 3.5 times blacker than average urban
particulate.[7] Thus, the change in reflectance due to
deposition of diesel particulate will be areater than that of
TSP because the difference between the reflectances of the
surface (R0) and the particulate (RD) will be greater.
This is caused by the high carbon' content of diesel
particulate," which has a reflectance of almost zero. Diesel
particulate also appears to stick to surfaces more than the
averaae particulate due to its oily nature (i.e., heavy
hydrocarbons bound to the surface).[8]
jY". repo-rt'-'r'prepared~'" f or''a1 i-forni;a .Air y'Resources'
lfdac
-------
7-7
As an example of how this soiling index would be used, one
can assume an area with 75 ug/m^ of TSP present. This
concentration would have what could be called a soilinq
potential of 75 ua/m^, since TSP is the base particulate
(i.e., a one-to-on-e correspondence between mass concentration
and soilino potential). if 5 ug/m^ of diesel particulate
were added to this atmosphere, the concentration of TSP would
become 30 ug/m^, an increase of 6.7 percent. However, usina
a soiling index of .5 for diesel particulate, the soiling
potential with the addition of diesel particulate would be 100
uq/m3 (75 + 5*5), an increase of 33 percent. Thus, one can
see how adding a..given concentration of diesel particulate to
the atmosphere can have a much greater effect on soilina than
would be indicated by its effect on particulate mass
concentration.
V. Summary
Very little data are available on the effect of ambient
particulate on the absolute degree of soilinq and the frequency
of cleaninq. However, it is clear that ambient Darticulate,
includinq diesel particulate, does result in soiling and has a
cost associated with its removal. In addition, it aDDears that
the deqree of soiling associated with diesel particulate is
qreater than that of TSP on a mass concentration basis;
possibly between 2.5 and 7.5 times as great. Thus, when
relating the soilinq effects of SDecific ambient concentrations
of diesel particulate to those of TSP, the concentrations of
diesel Darticulate should be increased by a factor
substantially greater than 1 to place them in the proper
oersoective with the TSP concentrations.
-------
7-8
References
1. "Particulate Matter Soiling of Materials," Harker,
Final Report Draft for U.S. EPA, EPA Contract No. 68-02-3422.
2. "Review . of the National Ambient Air Quality
Standards for Particulate Matter: Assessment of Scientific and
Technical Information," U.S. EPA, .OAOP.S.,-January. 1982 .
3. "Effects of Small Particles on Materials," Haynie,
U.S. EPA, Environmental .Sciences Research - Laboratory.
4. "Soiling of Building Materials," Journal of the Air
Pollution Control Association, Beloin and Haynie, 19757"
5. "Report on Study of Validity of Extension of
Economic Effects of Air Pollution Damage from Upper Ohio River
Valley to Washinaton, O.C.," Michelson and Tourin, Area
Environmental Health and Safety Research Association, August
1^67.
6. "Air Pollution: Household Soiling and Consumer
Welfare Losses," Journal of Environmental Economics and
Management, Watson and Jaksch, 19 8T~I
7. "Calibration of the D.S.T.R. Standard Smoke Filter
for Diesel Smoke," International Journal of Air and Water
Pollution, Wallin, Vol. 9, 1965.
•
8. "Assessment of the Irrroact . of Light-Duty Diesel
Ve-hic-les- .on Soi 1 ing-.-.-i n-G-a-l:t-fo¦r-ni-a-,-" -S-awyer- and ^Pit-zv" Prepared-
• *t;he^r'aFOFi-f6f-n-i:'a' Wirr-^esbtilf%'es-fdSf6fT'sJa'n"ira'fy ~T98 3'."""" ~
-------
CHAPTER fl
economic impact
t . Introduct ion
a• Organisation of chapter
This chapter addresses the economic imoact of the base
scenario relative to the relaxed scenario. (Full descriptions
of each scenario are oiven in the Tptroduction) The two basic
traD-oxidizer desians and the associated reaeneration svstems
ace described in the remainder of this introduction.
• The next two sections of- this chapter examine the economic
imoact of particulate cntrol on liaht-dutv diesel vehicles
(LPOV s) and trucks (LDDTs), and on heavv-duty diesel enaines
(uDDF.s) . The subsections in each section deal, in order, with
estimatina the cost of the hardware reauirements for
particulate control, evaminina the economic imoact on affected
vehicle and enaine manufacturers, estimatina the overall cost
to the consumer of particulate control, and estimatina the
annual costs (for the vears 1987 throuah 1995) and the 5-vear
aaareaate costs (3.9P7 throuqh 1^91 inclusive) of these controls.
B. Description of Trap Designs
The orimarv component of anv svstem for the reduction of
diesel particulate emissions is the trap-ox idizer. In addition
to the trao itself, other hardware components are required,
with the specific reauirements dependina on the basic
trao-oxidizer desian used. T^ap-oxidizers (traos) can be
broadlv divided into cateaories on the basis of two factors:
location or placement; and filter material.
An under floor-mounted trao occupies approximatelv the same
oositio", relative to the diese1 enaine, as is occupied bv a
catalytic converter on a aasoline-fueled vehicle. A
close-couoled trap is located nearer to the enaine, and is
usuallv incorporated in the exhaust manifold desian. Traos are
also catalvzed or non-catalvzed, accordina to the presence or
absence of catalvtic material.s to aid in the oxidation of
accumulated particulate.
Detailed descriptions of the desian and operation of each
tvoe of trao can be found in the ?DA Trap-Oxidizer Feasibility
Studv.m For this economic analysis, the costs and economic
impact are based only on the under floor-mounted ^esian, since
it appears to be the preferred desian of manv trao-oxidizer and
diesel vehicle/enaine manufacturers. The possibility of
-------
close-couoled traos beina used is addressed in Chapter 10. Mo
clear preference for one of the two major filter materials has
vet eneroed; a br ief descriDtion of each follows.
althouah manv filter materials have been investiaated for
use in traos, the current focus of develoomert and testir.a is
on ceramics and alumina-coated wire mesh. Ceramic traos
utilize a non-cataIvtic, Dorous cordierite material r2fMaO) +
2.(h.12-0-3-)_ +. S(SiO?)1 for the substrate. This substrate _is.
similar in construction to the suDDort structure used for
catalvtic converters in aasoline-fueled applications, tvpicallv
co.nsistina of a honevcomb desian with parallel, sauare_ channels
runnina the lenath of the unit. This trap desian is beinq
manufactured bv Nomina, **r;K, and other firms.
Johnson-Matthey is the primarv manufacturer of traps usina
alumina-coated wire mesh as the filter material. The form of
the wire mesh trap is a lona cylinder with a hollow central
core. The exhaust flows radiallv throuah the mesh filter from
the outside toward the hollow core. Catalytic coatina of the
wire mesh, lowerina the temperature necessary for traD
reaeneration (oxidation of the accumulated particulate
col]ected bv the filter), is inherent in the Johnson-Matthey
des ian.
Both tvDes of traD are enclosed bv a stainless steel
shell, basicallv the same as that used for the exterior shell
of a catalytic converter.
C. description of Peceneration Systems
T-n . add ition , • each--~tv.pe_--of .jtr-.ap. recu ir-e,S^r . a_.. method^ .of-.
r-eaenexationi " «• ?in"c'&' '-excess =-a'cru^ul-a-ted"-~Darticul-a-te -increases.
exhaust backpressure (thereby decreasina fuel economy and
vehicle oerformance), it must be oxidized or burned off
periodicallv. The temperature of the diesel exhaust stream is
tvpicallv inadeouate to initiate or sustain this oxidation.
Therefore, a reaeneration system is also reauired for effective
particulate control.
"'he hardware components reauired for an effective
reaeneration svstem depend, in part, on whether the trap is
catalvzed or non-catalvzed. The presence o* catalvtic material
in the trap filter reduces the temperature increase needed for
particulate oxidation, al.lowina the use oc a less complex
reaeneration system than is required for non-catalvzed traps.
Each, of these is briefly described below; detailed explanations
of the structure and functionina of trap reaeneration svstems
are available elsewhere.f1,21
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8-3
A tvpical reaeneration svstem for a non-catalvzed trap is
based on ~a diesel fuel burner, which injects diesel fuel into
the exhaust stream just before this stream enters the traD.
Rurnina the added fuel increases the exhaust temperature enouah
to ianite the accumulated oarticulate. The enaine exhaust flow
is temporarily routed around the traD, while the burner and
trao are supolied with a controlled air flow' to ensure
continued oxidation of the trapDed particulate without-
excessive heatinn.
This tvoical reaeneration svstem has seven orimarv
hardware components: a burner head, a fuel delivery svstem, an
icnition svstem, ah auxiliarv combustion air svstem, an exhaust
diversion svstem, svstem control sensors, and an electronic
control unit (^CU).
The burner head provides a location for mountina the fuel
sorav nozzle, ignition Dlua, and auxiliary air nozzle. It is
also assumed to include a aas distribution baffle for evenlv
distributing the combustion products over the cross-section of
the trap.
The fuel delivery svstem Drovides the diesel fuel
necessarv for initiating the trap regeneration Process. This
svstem includes a fuel sprav nozzle, a fuel feed line, and a
fuel solenoid valve.
The fuel ianition svstem mav be one of two basic tvpes.
One svstem consists of a lona-life spark Dlua, a step-up
voltaae transformer, and sianal conditionina electronics for
aeneratina a hiah-voltage discharae. An alternative to this
svstem is" a alow plug, like those used to cold-start diesel
enoi-nes'. -
The auxiliary air combustion svstem, which Drovides a
controlled air supdIv to the burner and trap to sustain the
oxidation of the accumulated particulate, consists of an air
pump, a check-valve, a diverter valve, and an air deliverv
line. The check-valve prevents exhaust backflow into the air
pump, while the diverter valve provides an alternate path in
the event that combustion air must be diverted from the
filter. The air deliverv line connects the air pump to the
burner head.
The exhaust diversion svstem temoorarilv reroutes the
enaine exhaust stream around the trap durina the reaeneration
process. It consists of a vacuum motor driven by the FPU and
an enaine-driven vacuum pump, which aenerates the vacuum
reouired for operation of various control elements. An
alternative to this svstem, not requiring a vacuum pump,, is a
solenoid valve ODerator.
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8-4
Svstem control sensor • requirements include two temperature
sensors, and a control sensor for determinina the need for traD
reaeneration. Temperature sensors are reauired for detectina
overheatina in the trap filter durina the reaenerat ion, and for
ensurina that the enaine has attained normal ooeratina
temperature before the reaeneration is initiated. The sensor
determinina the need for traD reaeneration could be either an
enaine revolution or vehicle mileaae timer, or an exhaust
backpressure sensor.
The most important reaeneration svstem component, in terms
of svstem control, is the ECU. The FCU interprets sianals
received from the various sensors in order to maintain control
of the reaeneration process.
As was noted earlier, the reaeneration system for a
catalvzed trap can be less complex, since the increase in the
exhaust stream temperature reauired is much smaller. Of the
seven primarv hardware components reauired for the
non-catalvzed trap reaeneration svstem described ahove, only
the svstem.control sensors and the ECU are needed in basically
the same form for the catalvzed trap reaeneration svstem.
Some tvpe of auxiliarv air combustion system is still
reauired;m however, since the exhaust flow throuah the
catalvzed trap is maintained durina the receneration process, a
reed valve svstem mav be adeauate. The burner head, exhaust
diversion svstem, fuel deliverv svstem, and iqnition svstem
described a^ove are not reauired.
However, an alternate svstem for orovidina a moderate rise
in the temperature of the exhaust stream is still reauired.
One such ^etjh.od, _ wh ich _ has been^ ^successfully^ tested^ on a ^
catalvzed wire-mesh trap,, is known, .as. .delayed in-cvlinder fuel
injection. A small amount of fuel is injected into the
cvlinder durinq the exhaust stroke, when the cvlinder is too
cool to ianite the fuel. The injected fuel is carried in the
exhaust stream to the catalvzed trap, where it is ignited.
Since the existina fuel svstem is used to inject the fuel, the
only hardware necessarv is a mechanism for transferrina a
portion of the fuel beinq metered from a "normal" injector to
the "delav" injector.
Thouah actuallv not part of the trap or of the
reaeneration svstem, one other vehicle modification affectina
the exhaust svstem should be discussed here. The exhaust pioe,
leadina from the enaine to the trap-oxid izer, will have to be
fabricated of stainless steel. Tf fabrication of this pipe
usina normal steel were continued, periodic replacement would
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8-5
he required, greatly increasina the chances of the
trap-oxidizer beina removed from the vehicle. This
modification is reauired for all of the traD desians and
regeneration systems discussed.
II. Licht-Dutv Diesels
A. Introduction
This section examines the impact of particulate control
for LDDVs and LDDTs. Since the methodoloav and inanv of the
hasic assumptions used in this analvsis are the same for both
lioht dutv and heavy duty, this section contains considerably
more detail than does the next section"on heavv-dutv diesels.
^he next subsection estimates the costs, in terms of the
retail price equivalent (RPF.) , of each of the basic traD
desiqns and reaeneration systems described in the
introduction. These costs are laraelv a function of the size
(volume) of the trap-oxidizer. This discussion is followed bv
subsections treatino the economic impact on diesel
manufacturers, the overall cost to the consumer, and the annual
and 5-vear aaareaate costs of these controls.
After the costs of the hardware (trap-ox idizer and
reaeneration system) are estimated, the subsequent analysis
examines the economic impact under two requlatory scenarios
(base and relaxed) , and under two sets of future diesel sales
projections ("best estimate" and "worst case"). The requlatory
scenarios are described in detail Dreviouslv. The best
estimate sales projectionsf31 are exactlv what the desianation
implies, while the worst case sales projections are based on
the maximum .increases in diesel sales,, that appear to. be
reasonable . " . (The . t.erm, "wor st" c.a-s.e V/pefe.rs- • t.o - the impact. o-f-
increased diesel sales on total particulate emissions, and the
resu]t.ina environmental effects.)
The cost of the two basic trap-oxidizers, catalvzed and
non-catalvzed, were previouslv estimated in the Requlatorv
Analysis that accompanied the oriainal liqht-dutv particulate
control reaulations. r41 The model used to estimate the
manufacturinq costs of each trao desian, which was developed bv
Lindaren,[5l is aaain used in this analvsis, with cost
estimates provided by the trap manufacturers incorporated into
the model where available. The Lindaren model for estimatina
the RPE of manufacturino costs[5] is based on the application
of adjustment factors to the estimated sum of direct material
and labor, and fixed overhead costs. These factors are
expressed as l.n plus the sum o^ the adjustment terms, as shown
below:
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8-fi
RPE = HDM+DL+O") (l+CA+S®)+'pF+LBEl (1+CA+^p+DP)+RD+'T,F (1)
where:
DM = Direct material cost.
DL = Direct labor cost.
ow = Fixed and variable overhead.
CA = Comorate allocation term of adjustment factor.
= Supplier profit term of adjustment factor.
tf = Tooling expense.
LBE = Land and buildina expense.
CP = Corporate profit term of adjustment factor.
DP = Dealer overhead and profit term of adjustment factor.
RD = Research and development cost.
Some of the values used in equation 1 were taken directlv
from Lindaren's work,[51 while others have been adjusted based
on more recent analvses.f^l Additional adjustment factors for
inflation and production volume (i.e., economv of scale) are
also incorporated in this analysis. These are described in
more detail below.
Reoenerat ion system costs have also reen estimated in the
past.f41 Tn this analysis, these earlier estimates are
essentially supolanted bv more recent work performed hv Mueller
Associatesf21 under an EPA contract.
R. Trap-Ox idizer Svstem Costs
1. Introduction and Assumptions
, .... ...The., adjustment factors, .for... in fl-at.ion - .and - production- •- volume —*
• ^arennisndeDend.ent -s of''-'"the 'trao - deS'i'a'hi;*r'br "r-fec'e'ne:r"at'ib'rT - svstem"
used. Therefore, these are discussed first, before estimatina
the specific manufacturing costs for each case.
Some of the manufactur ina cost data that went into the
development of Lindaren's model and into the previous E^A
analyses dates from as earlv as 1978. Therefore, an adiustment'
factor for inflation must be determined. For application to
Darticulate control hardware, the increase in LDV (new car)
orices from 1978 throuah 1982 aooears to be a more appropriate
estimate of inflation than the rise in the Consumer Price Tndex
over the same time span. New car prices were 33 percent hiaher
in 1982 than in 197fl, with annual increases of fi.2, 7.4, 7.5,
and 1.6 Percent in 1978, 1979, 1980 , 1981, and 1982 ,
respectivelv.\61 ^hese inflation rates are used in this
analvsis.
-------
fl-7
Production volumes of different traps bv various traD
manufacturers are uncertain. The assumption in this analysis
is that two manufacturers will supply traD-oxidizers, and that
each of them will supply apDroximately half of total production.
It is also necessary to distinauish between different
sizes of LDDVs and LDDTs, since the size (volume) of the trao
is deoendent on the enaine size (disDlacement). In this
analysis, LDD^s are divided into small, medium, or large on the
basis of enaine disolacement. Small LDDVs are those' equipDed
with 1.6- to 1.8-liter (L) enaines, medium LDDVs are eauipDed
with 2.0L to 2.8T, enaines, and larae LDOVs are those with 3.0^
~ and larger enaines. It is assumed that "the Projected LDDV
sales will be divided aoproximatelv eauallv amonq these three
size classes. The LDDTs are considered to be either small
(enaines under 4. ^L) or full-size (4 . "'L and laraer enaines).
pull-size LDDTs are assumed to sell at a 4:1 ratio to small
LPD^s.
Rased on the best estimate LDDV sales projectionsf31 and
the Droiected rates of traD usaae (see Chapter 1), a standard
averaae---production level of 200 ,n00 tracs annuallv for vears
1987-91, for each of the three LDDy size classes, is a
reasonable estimate. This estimate would TncreaTe If based in
worst case sales projections.
Projected averaae annual sales oe small r.DD^s are
aoproximatelv half those projected for each LDDV size class
(see ChaDter I). Thus the standard averaae trap oroduction
level for small LDDTs is estimated at 100,000 annuallv, or half
of the standard Droduction level for each LDDV size class.
Full-size LDDT sales ajre projected to be rouahlv twice those.
'. 'for" £ac'h. '".LDDV size ia"ssT"" *€Kerelfore,. th,e'_! standard'""' avera'b'e"
oroduction level of traps for full-size LDDTs is estimated, to
he 400,000.
In order to develop adjustment factors based on the
standard averaae production levels' of traps for each of the
five size classes of liaht-dutv diesels, the "learnina curve"
must be known. For trap-ox idizer production, the learnina
curve is assumed to be 12 nercent.[41 The learnina curve
conceot is apDlied to the Droduction levels by first assumina
that some standard averaae oroduction level serves as a
baseline, for which the Droduction level adjustment factor is
eaual' to one (i.e., no adjustment). fTnder a 12 oercent
learnina curve, doublina the baseline Droduction level leads to
a 12 percent decrease in per-unit manufacturina costs, or an
adjustment factor of n.88. Converselv, halvina the baseline
production level leads to a 13.fi percent increase in per-unit
manufacturing costs, expressed as an adjustment factor of 1-13 6
(l.n/o.88).
-------
8-8
Application of the learnina curve to the production of
trap-oxidizers is done bv assuming that the baseline standard
averaae production level is 200,000 traDS annually, the level
estimated for each of the three LDDV size classes. Therefore,
no adjustment factor for the level o^ production is applied to
the 200,000-trap annual production level assumed for each LDDV
size class. "'he adjustment factor for full-size LDDTs is 0.88,
representina a 12 percent decrease in Der-unit manufacturina
costs resultina from a doublina of LDDV traD production. ror
small LDDTs the production level adjustment factor is 1.136,
reflecting the production level of small LDDT traps beina half
that of each LDDV size class.
The production volumes of traos for each size-based class
of light-duty diesels are all based on the best estimate sales
projections. Hnder the worst case projections, LDDV production
would double and LDDT production would increase 50 percent over
the best estimate projections. ^he effect would be to lower
per-unit trap manufacturina costs by 12 percent for LDDVs and
by 6.2 Percent for LDDTs.
With the information aiven above, the discussion can now
he focused on estimating the manufacturing costs of each trap
desian and of the reaeneration svstems.
2. Non-Catalvzed (Corning) Trao
A formula for determining the manufacturina costs of
non-catalvzed traps has been developed and used in previous EPA
analvses.f1,71 This formula was derived by relatina the
various trap components to similar or identical components of a
•rno nol ;i.t h,ir:,.,..:ca t a-,l.v.s:tr..- for-.-•gaso line ^-fuelede,ng.ines , r. for wh;i-.ch-
-¦cortf-irmed —-•¦•man.uf actu-r inar-rv-costs --a-r-e-- ^alr eadv^. known-."-*-- -..a-f-.fer=
apDlving the adjustment -factors, includina those for inflation
and production volume (hased on the best estimate sales
projections) determined in the precedina section, the formulae
are:
For LDDVs:
RPE = $23 + 0.318 PM
(2A)
For small LDDTs:
RPE = $26 + n. (V)
(2R)
For full-size LDDTs:
RPF = $20 + 0.280(V)
(2 C)
-------
8-9
where:
V = the volume of the trap, in cubic inches.
As an example- of apDlvina these eauations, consider the
case of a non-catalvzed traD that was recently tested
successfully; by Southwest Research Institute, on a
Vercedes-Renz 300D. This trap had a volume of 302 cubic inches
(5.66 inch diameter x 12 inch lenath); substitutinq 302 for V
in equation 2A (for LDDVs) leads to an estimated manufacturina
cost of about $119.
As mentioned earlier, traps of various sizes (volumes)
will be fitted to different sizes of engines. Trap size can
loaically be exoected to be a function- of volumetric exhaust
flow of the enaine. [11 while data on the typical volumetric
exhaust flows of various enaines are not readilv available,
fuel consumotion (the inverse of fuel economy) is an adequate
surrogate measure, fll The ratios of the fuel consumDtions*, or
the inverse ratios of the fuel economies, over the FTP (EPA
urban) drivina cvcle can he used to extrapolate trap volume
requirements for other engine sizes, given a known reference
Doint: The Mercedes-Benz 300D mentioned above has an EPA citv
fuel-economy rating of 26 miles per gallon (mog).
Projected fuel economies for each of the five size classes
under consideration, in 1990, are aiven in the table below:
Size Class
Ena ine
Projected FE
Small LDDVs
Med i'UTTV LDDVs
Laroe LDDVs
Small LDDTs
Full-size LDDTs
1.6 to 1.8L
2 .0 to ."? ; «L'
3 . 0L and u'd"
under 4.3L
4.3L and up
51.2 mpg
.43.9 mpg
'37.8 moo
4 4.9 moa
3 3.6 mpg
These estimates were derived from fuel economv estimates for
qasoline enaines in 1990, F3] with a 25 percent improvement
assumed in diesel enaine fuel economv over the corresoondina
qasoline engines.
Usina the Mercedes 300D (26 mpa fuel economv, 302 cubic
inches trap volume) as the reference point, and apolving the
fuel consumption ratios as discussed above, the resultina traD
volume reauirements are:
-------
8-10
Size Class
Trap Volume
Pull-size LDDTs
Small LDDVs
Medium LDDVs
Larce LDDVs
Small LPDTs
1?3 cubic inches
179 cubic inches
208 cubic inches
175 cubic inches
234 cubic inches
These volumes can be substituted for V in the equations
2A-2C, vielding estimated manufacturing costs of $72, $80, and
$89 for small, medium, and larae LDDVs, and $88 .and $87 for
small and full-size LDDTs, respectively.
As shown in the table of trap volumes above, the small
LDDT traD is projected to reauire a volume only 4 cubic inches
less than that of the medium LDD^ trao. The medium LDDV trao
is also estimated to cost less to manufacture than the small
LDDT traD, $80 versus $88. Thus it is more economical to
produce one trap, of the size required for medium LDDVs, for
both medium LDDV and small LDDT aDplications. Combining the
standard average production levels of 200,000 annually for
medium LDDVs and 100,000 annuallv for small LDDTs into a new
standard averaae production level of 300,000 traps, the assumed
12 percent learning curve lowers the per-unit cost to $74.
The manufacturing costs oresented above are summarized in
^able 8-1. Confidential estimates of manufacturing costs
supplied by Corning, while not firm, indicate that the
estimates shown in Table 8-1 are reasonably accurate.
cr v. wo-r-s.t ^c:a-se;. .sales - project ions the„-co sjt.: _est imates,
aiven ab-ove^ are - reduced--^bv 1-2- Dec-cent- for *LDDVs--and • -bv--7 >2
percent for LPOTs. These estimates are also shown in Table P-l.
3. Catalyzed (Johnson-Matthev) mrao
Tn the Reaulatorv Analysis for the 198S liaht-dutv diesel
oarticulate reaulations, (41 the cost of a catalyzed trap was'
also estimated bv relatina the comoonents of the trap to
similar or identical components of a monolithic, ceramic
catalvtic converter, with washcoat and noble metals included.
A formula was then developed for estimating the manufacturino
cost based on the trap volume.
Johnson-Matthev has since publiclv stated that the
manufacturing cost of their catalytic trao substrate, ready for
cannina, was $100 (in 1992 dollars) for a trao intended for use
with a 2.0L enqine. If the volume of this trap is assumed to
be eaual to that of a trao recentlv tested successfully on a
Volkswagen Rabbit with a 1.6L enqine (345 cubic inches), then
-------
8-11
Table 8-1
Light-Duty Trap Costs (1983 dollars)
Best Estimate Sales Projections
Non-Catalyzed Catalyzed
Vehicle Class Trap Trap
Small LDDVs $72 $188
Medium LDDVs $74 $199
Large LDDVs $89" $246
Small LDDTs
$74
$199
Full-Size LDDTs
$87
$236
wo r s t
Case Sales Projections
Vehicle Class
Non-Catalyzed
Trap
Catalyzed
Trap
Small LDDVs
$63
$165
Medium LDDVs
$66
$178
Large LDDVs
$78
$216
Small LDJDTs_
_ $66 r_ . .
. . ..:v$.17.8. .
Full-Size LDDTs
' ' $81
$219"
-------
8-12
the RPE of the manufacturina cost can be determined using the
Johnson-Mat they cost information. The $10fl-estimated
manufacturing cost must first be inflated to 1^83 dollars and
then substituted for the non-catalvzed substrate manufacturina
cost in eauations 2A-2C. The effects on the total cost of
cannina, corporate overhead and profit, and dealer mark-up are
assumed to he unchanaed from the non-catalyzed trap.
It is assumed that the fixed costs (i.e., toolinq and
machinerv, fixed overhead) are the same for both trap types,
meanino that all variable costs can be expressed as a function
of traD volume. ^inallv, bv combinina the production of traps
for medium LDDVs and small LDDTs as was discussed in the
precedino section, the followinq eauations result:
For small and large LDDVs:
RPE = $23 + n.582(V) (3A)
For medium- LDDVs and small LDD^s:
RPE = $22 + n.536(V) (3B)
For full-size LDDTs:
RPF. = $20 + O.sni(V) (3 C)
Where:
v = the volume of the trap, in cubic inches.
_ - ¦. ---The- -345 - cubic- inch catalyzed trap - mentioned- above is
estimated to cost about $22"4, based ~orv-"eduartff6'rf"3A. • 'Use' of tfie
methodoloay developed in the oriainal Feaulatorv Analysis,[41
with adjustments made for inflation, oroduction volume, and
more recent precious metal costs, vields an estimated cost of
$212 for a 34? cubic inch catalyzed traD. ^hus incorporatina
the Johnson-Matthey estimate into the eauations 2A-2C changes
the estimated overall traD cost by less than 6 percent.
As in the non-catalyzed case, it must be assumed that
traps of different sizes (volumes) will be Droduced for use
with different enaines. The 1990 estimated fuel economies for
liaht-duty diesels qiven above are used here, with the
reference point changed to the Volkswagen Rabbit (42 mpa fuel
economv, 345 cubic inch traD volume). Applvina the ratios of
fuel consumption as a surrogate measure of volumetric exhaust
flow, as was done in the non-catalyzed case, vields . the
following trap volume requirements:
-------
8-13
Size Class
Trap Volume
Small LDDVs
Medium LDPVs and
283 cubic inches
330 cubic inches
small LDDTs
Larae LDD^s
Full-size LDDTs
383 cubic inches
431 cubic inches
Substituting these volume requirements for V in eauations
3A-3C gives the RPE of the manufacturina cost. The estimated
costs based on the equations are: $188 for small LDDV traps,
$199 for medium LDDV and small LDDT traps, $246 for large LDDV
traps, and $236 for full-size LDDT traps. These cost estimates
for catalyzed traps "are also summarized in Table 8-1.
¦Equations 3A-3C and the cost estimates above are based on
the best estimate sales projections. ^he impact of the
"worst-case" sales projections on these estimates is the same
as on the non-catalyzed cost estimates, with the LDDV costs
reduced by 12 percent and the LDDT costs reduced bv 6.2 percent
from the figures above. These estimates are also shown in
Table" 8-1.
4 . Regeneration Svstem Costs
The main components of trap regeneration svstems, for both
catalyzed and non-catalyzed trap-oxidizers, were described in
the introduction. The positive regeneration svstem for
non-catalvzed traos, which actively initiates the burn-off of
the accumulated particulate by injectina iqnited diesel fuel
into the exhaust streafo, is dealt with first. The costs
^.stim.a.ted. ^fAC ^bot.h.., r.eg.ene,r.at.ion systems are . largely based; ,.on„
"the*..anaivjO.;sr.p.exfjorroed'Lby Mueller. A.s.s.o.ciat-es ^or , EPA.i2}-.
The components of both tvpes of regeneration system are
listed, with the estimated RPE of the manufacturing costs, in
Table 8-2. These estimates are based on the production levels
corresponding to the best estimate sales projections. Since
almost all of the regeneration system components listed in-
Table 8-2 are also manufactured for purposes other than
particulate control, the production levels are hioher than
those of trap components. On this increased base production
level, the impact of the "worst-case" sales projections is much
smaller. Thus, any changes in these estimates due to increases
in trap-eauipoed diesel. sales are also much smaller, and are
not shown in Table 8-2.
The hardware
system are listed
same order as thev
comoonents for each tvoe of regeneration
in Table 8-2, and discussed below, in the
were described in the introduction.
-------
8-14
Table 8-2
Light-Duty Regeneration
System Costs (1983 dollars)
Retail Price
Hardware Item Equivalent
Non-Catalyzed Trap:
Burner Head $7
Fuel Delivery System $9
Fuel Ignition System* $5-26
Auxiliary Combustion Air System $30
Exhaust Diversion System* $11-14
System Control:
Sensors $12
ECU** $10
Subtotal $84-108
Stainless Steel Exhaust Pipe
Small and Med. LDDVs, small LDDTs $16
Large LDDVs, full-size LDDTs $27
Total System Cost $100-135
Catalyzed Trap:
Delaved In-Cylinder Fuel Injection Mechanism $15
Auxiliary Combustion Air System (Reed Valve) $6
Svstem Control-: ? -•••
^'--'nncr*•'
ECU** $10
Subtotal $43
Stainless Steel Exhaust Pipe
Small and Med. LDDVs, small LDDTs $16
Large LDDVs, full-size LDDTs $27
Total System Cost $59-70
Explanation of cost ranaes appear in the text.
Derivation of the ECU cost appears in the text.
-------
8-15
The burner head is assumed to be fabricated of stamDed and
welded Type 409 stainless steel, and has an estimated cost of
$7. [21 The fuel deliverv system, for supplying the fuel to be
ianited to initiate the reaeneration process, has an estimated
cost of $9.f21
Two basic fuel iqnition svstems were described in the
introduction. The more costly svstem (lona-life spark plua,
steo-up voltaae transformer, and sianal conditionina
electronics) is estimated to cost $26.[21 While the use of a
qlow oluq is less exoensive, with an estimated cost of 55, [21
it is also less reliable for ianition when the temperature of
the exhaust stream is -relatively low. Both of these options
are included in Table 8-2.
The regeneration process requires a controlled supplv of
air to the burner and trap to sustain particulate oxidation.
The total cost of the auxiliary air combustion svstem (pump,
delivery line, and valves) is estimated to be $30.(21
Exhaust must temporarily be rerouted around the
non-catalyzed trap during reqeneration. - The exhaust diversion
system for accomplishino this is estimated to cost between $11
and $14. [21 The lower cost is for a system utilizing a vacuum
motor (an enqine-driven vacuum pumo is assumed to already be
present on the vehicle), while a system using a solenoid valve
operator is represented by the hiqher cost (no vacuum oumo need
be present on the vehicle).
Svstem control requires the use of several sensors. The
estimated costs are $9, for a sensor to detect over temperature
in the filter durino the . regeneration, and $1, for a sensor to
ensure",~ tha t^thje eng; ine~~ R"a's^ rthe_pf oner..opexat ind,-
temperature '"before reqeneration is initiated. [21 The sensor
for determininq the need for trap reqeneration could be either
an enqine revolution or vehicle mileaqe timer, or, an exhaust
backpressure sensor. The cost of the former is negligible,[21
while the latter is estimated to cost no more than $2. [81
Since the backpressure sensor is more desirable, however, the
latter estimate is included in Table 8-2.
The critical system control component is the electronic
control unit (FCU). Tor qasoline-fueled enqines, the current
total cost of an FCU is approximately $75.[21 Several factors
make this cost inappropriate for direct use in Table 8-2.
First, the current ECU is typically much more sophisticated
than is needed for reqeneration system control. Second, it is
highly probable that FCUs on diesels after 1987 will serve
several purposes in addition to their emission control
functions. (For example, Tsuzu's 1983 diesel vehicles contain
-------
8-16
an ECU which functions to improve fuel economy and vehicle
performance, as well as to control dashboard lighting and other
miscellaneous devices or "aadgets.") Third, and most
importantly, continuing advances in microprocessor technology
can be exDected to further reduce the cost of ECUS in
constant-dollar terms, while simultaneously widening the scope
of potential automotive applications.
No data are available on manufacturers' plans for the
installation of ECUs to serve functions other than emission
control. A conservative estimate is- that half of aTl LDDVs and
LDDTs will be equipped with ECUs, for reasons other than
emission control, during the period 1987-95. The remainina
half of LDDV/LDDT production would incorporate ECUs in order to
comply with emission control requirements; however, once
incorporated into the vehicle desian they would certainlv serve
additional valuable functions.
The ECU in the LDDV or LDDT of the future will have four
primarv functions: improvino- fueleconomy, improvina vehicle
oerformance, device and "qadaet" control, and emission
control. Allocating one-quarter of the total $75 cost to the
emission control aspects of the FCT7 aives an estimated cost of
approximately $19 due to particulate control.
Assuming that half of the ECUs installed for emission
control will be required solely for particulate control reduces
the fleetwide averaae per-vehicle cost to $10. If ECUs are
installed in mqre diesel vehicles than projected for purposes
of NOx control, this estimate may be reduced even further.
This " regeneration" svstem has a total estimated RPE of
between $85 and $109, dependinq mostly on the fuel iqnition
svstem chosen. As discussed in the introduction, a stainless
steel exhaust pipe will also be required for trap-equipped
vehicles. When a credit for the deleted standard steel exhaust
oipe is included, the additional cost of this modification is.
estimated as $16 (for small and medium LDDVs and small LDDTs)
to $27 (for large LDDVs and full-size LDDTs). These costs are
also shown in Table 8-2.
T'he regeneration svstem for a catalyzed trap should be
less complex than the system required for non-catalvzed traps,
as was explained in the introduction. while detailed cost
estimates such as those given above are not available for this
simpler svstem, the savinas over the "burner system" can be
estimated using the information in Table 8-2.
-------
8-17
No burner head assembly is required. The fuel delivery
system is replaced by a mechanism for transferrinq a small
amount of fuel from the normally-functioning injector to the
"delay" injector. This mechanism is expected to cost about
$15. [21 The auxiliary air combustion system described above
can be replaced by a reed valve (estimated cost $6),[21 since
the continued exhaust flow throuah the catalyzed trap durina
regeneration will provide the required suction.
The sensors and the ECU, reauired for reaeneration svstem
control, are basically identical for either system. The
stainless steel .exhaust . pipe is also required for... both-
"svsteiiis.* The cost estimates for these components of the
catalyzed trap regeneration system are the same as for the
non-catalyzed case. All of this information is also shown in
Table 8-2.
5. ^otal Trap-Oxidizer System Costs
The total cost of the trao-oxi^izer system is the sum of
the costs estimated for the trap and for the reaeneration.
"""system."' "Summaries of these costs under both the best estimate
and the worst case diesel sales projections are shown in Table
8-3. Since the widths of the ranqes in cost are quite small,
relative to the absolute costs, only the midpoints of the cost
ranoes -are shown in Table 8-3. These "midpoint" estimates are
used throughout the rest of the analysis.
It is clear from Table 8-3 that, despite the savings
associated with the reaeneration system, the total cost of the
catalvzed trap-oxidizer svstem' is still estimated to be
_ -sukScXantJicil,l.y; ...jnorei„ than„_ that ._ of the ~ nonr-catalyzed —systems
-'¦ *S"ince"-'fi"tr,"rsA''c:'^sci'deraBlV-r-less'" 'exbe"hs'ive, "and - appears" to "be the '
oreferred desian of most diesel manufacturers, only the cost of
the non-catalyzed trap-oxidizer svstem is used in the remainder
of this analysis.
C. Economic Impact on Diesel Manufacturers
In this section, the impact of the base scenario on
manufacturers' light-duty diesel sales, capital investments
and cash flow will be analyzed. Only the costs of the
trap-oxidizer system and the associated fuel economy penaltv
are considered here. There are no test facility costs
associated with the base scenario. Certification costs were
shown to be negligible in the Reaulatorv Analysis to the 1985
particulate standards.[41
-------
8-18
Table 8-3
Total Light-Duty Trap-Oxidizer
Svstem Costs (1983 Dollars)
Rest Estimate Sales Projections
Vehicle Class
Small LDDVs
Medium LDDVs
Larae LDDVs
Small LDDTs
Full-Size LDDTs
Non-Catalvzed
Trap
$185
$187
$213
$187
$211
Catalyzed
Trap
$246
$258
$316
$258
$306
Worst Case Sales Projections
Vehicle Class
Small LDDVs
Medium LDDVs
Larqe LDDVs
Small LDDTs
Full-Size LDDTs
Non-Catalvzed
Trap
$176
$179
$202
$179"
$205
Catalyzed
Trap
$224
$237
$286
' $237 ":V
$289
-------
8-19
1. Impact on Manufacturer's Sales
The "imoact of the base scenario on light-dutv diesel sales
depends primarily on three factors. First is the vehicle price
increase resulting- from the additional cost of installinq a
trap-oxidizer. Second is the fraction of vehicles requiring
trap-oxidizers, which was determined in Chapter 1. Third is
the 1-3 percent fuel economy penalty associated with the use of
trap-oxidizer technoloav.f91
The next step is applyino these factors to determine a net
impact on future diesel sales. This has already been done for
a number of potential combinations of trap costs and trap usaoe
rates, in a study performed by Jack Faucett Associates (JFA)
for FPA[31 usino consumer information on diesel vehicle
purchases from Chase Econometrics.[10] JFA estimated the
imoact on LDDV and LDDT sales assuming trap-oxidizer costs of
$300, $500, and $800, and trap usage rates of 0 percent, 35
percent, *55 percent, and 90 percent. An average fuel-economy
penalty of 2 oercent for vehicles equipped with traps was also
incorporated. It was assumed that the largest diesel vehicles
would be eauipped with traps first, the medium-size diesels
next, and the smallest diesels last, until the overall trap
usage rate was met.
To simplify the aDDlication of JFA's results, an average
trap-oxidizer cost will be used for each vehicle class (LDDV
and LDDT). The trap-oxidizer costs for each vehicle size will
be weighted bv the relative sales of each vehicle size, as
estimated bv JFA. [31 This averaoe cost is $713 for LDDVs, and
$219 for LDDTs.
Usino the averaoe trap system costs and the trap
_p.ednfctr ation rat e ; VhlsTf :'f e: ^^al&r^o'f es'.el \~
'vehicles "and trucks carT be projeVted by interpolation of the
JFA estimates. Table 8-4 shows the projected sales for the
"relaxed scenario," where no traps are required on liaht-duty
diesels, under both best estimate and "worst-case" diesel sales
projections. These figures repreisent the maximum number of
vehicles projected to be sold, as these vehicles do not bear
the cost of a trap-oxidizer.
Also shown are the effects of the base scenario on
light-duty diesel sales under both the best estimate and
"worst-case" sales projections. ^s can be seen, the impact of
the base scenario is qreatest in the early years (e.g., 1987)
and diminishes with time. In addition, LDDV sales are affected
more than LDDT sales. The largest impact occurs in 1987, when
30,000 LDDV sales are lost (3.4 percent of total LDDV sales
under the best estimate sales projections). By 1995, this loss
-------
8-20
Table 8-4
Light-Duty Diesel Sales Projections*
(in thousands)
Sales and Percent Reduction
1987 1990 1995
Best Estimate Sales Projections
Relaxed Scenario
LDDV Sales
LDDT Sales
Total: LDDVs and LDDTs
Base Case Scenario
LDDV Sales
LDDT Sales
Total: LDDVs and LDDTs
Worst Case Sales Projections
Relaxed Scenario
LDDV Sales
LDDT Sales
Total: LDDVs and LDDTs
.Base.., Case ..Scenario;., . ..
LDDV Sales
LDDT Sales
Total: LDDVs and LDDTs
11 California sales included.
* * Da rcsn ra^iirf inn in c a 1 «a a
912
1, 300
1,380
714
1,029
1,322
1,626
2,329
2 ,702
881
(3.4%)** 1,260
(3.2%)
1,355
(1.8%)
704
(1.4%) 1,018
(1.0%)
1,310
(0.9%)
1,585
(2.5%) 2,278
(2.2%)
2,665
.(1.3%)
1,824
2 ,875
3,600
952
1,400
2,340
2,776
4,275
5,940
1,793
(1.71)** 2,835
(1.4%)
3,575
(0.7%)
942
(1.0%) 1,389
(0.8%)
2,328
(0.5%)
2,735
(1.5%) 4,224
(1.2%)
5,903
(0.6%)
from :
relaxed scenario
•
-------
8-21
diminishes to 2^,000 on a much laroer sales base (1.8 percent
of total "best estimate" LDDV sales). Losses of LDDT sales are
rouahlv one-third to one-half as qreat, in the ranae of 10,000
to 12,000 units annually.
An underlyino assumption of this analysis is that the
manufacturers will pass the total cost of the t'rap-oxid izer
svstem on to the consumer. Manufactuers have been selling
diesel vehicles at a premium to consumers willing to pay extra
for ownership of a relatively new and advantaaeous product.T31
-Thus- diese-l -manufacturers have been generating higher than
normal profits on diesel sales, relative to profits on
comparable gasoline-fueled . vehicles. If this .situation
- ; continues ,-r/-then-manufacturers m-iaht - be able - to ahsorb some of - -
the costs of a trap-oxidizer system bv reducing their
above-normal profit margin. However, it is expected that the
premium in the price being paid for diesels will decrease as
increased competition from other diesel manufacturers brinas
profit margins down to normal levels. Manufacturers then would
not be able to ahsorb the trap-oxidizer cost, and would pass it
throuqh to the consumer.
. . .. ...Even if. diesel sales decrease as a result of manufacturers
addinq trao-oxidizer costs to their vehicle sales prices, it is
unlikely that the automobile industrv as a whole would lose a
sale. JFA concluded that any consumer deciding not to buy a
diesel would purchase a gasoline-fueled vehicle instead. This
finding is not surprising when it is considered that . the
functions of the two tvpes of vehicles are nearly identical,
and that only the economics of ownership differ. Thus the
automobile industrv as a whole should suffer no lost sales due
to the base scenario particulate control standards.
"/.^IgV6.5tm;e.nt/iCast;S ,3tnjfrr/Tw; E f f.ects "/ * •;:
two other effects that emission regulations can have on
diesel manufacturers are increasing required capital investment
(i.e., toolina, machinery, research and development (R&D),
etc.) and reducing cashflow. These effects are examined below.
The bulk of the capital investment associated with the
reouired use of trap-oxidizers is not expected to be borne by
diesel vehicle/enqine manufacturers, but rather by the
manufacturers of emission control equipment, such as Cornina,
NGK, and Johnson-Matthey. The catalvst manufacturers alreadv
have developed the necessary substrate technoloqv, and the
diesel manufacturers have shown little interest in this area.
Even thouqh the manufacturers of emission control equipment
will have to finance the necessarv investments, thev all have
indicated their willinqness and abilitv to enter this market.
Thus pre-production investment costs should not be a problem
for any affected entities.
-------
8-22
with respect to other investment costs, liaht-dutv
manufacturers are presently incurring some R&D costs associated
with- applying trap-oxidizer technoloay to their vehicles.
However, much of this work has already been completed, and
future R&D should be no less fundable. Thus, R&D and capital
investment requirements should not have a significant adverse
impact on any manufacturers' investment plans.
Given the above, the only impact on cash flow will result
from the inventorv of traps, individually and on partially
manufactured vehicles.. The . time.....each trao is held should be
much shorter than 'that for an entire vehicle, which averages
about 90 days.[41 This turnover period should be short enough
to not siqnificantlv affect a manufacturer's cash flow. For
example, assuming an average turnover time of six weeks and
industry-wide sales of 1.5 million LDDVs and LDDTs, the value
of the trap-oxidizers on hand at any given time would only be
$37.5 million. This is less than $4 per vehicle spread across
total light-duty sales.
D. Total Cost to the Consumer
The hulk of the total consumer cost of particulate control
is the increased "sticker price" of an LDDV or LDDT. Assuming
that the full RPE of manufacturing cost is Dassed through to
the retail purchaser, the entries of Table 8-3 represent both
total trap-oxidizer system costs and the increase in new
LDDV/LDDT purchase prices due to particulate control. The
remainder of the total cost to the consumer results from the
fuel-economy penalty, and from anv increases in the maintenance
costs, for - -1 iqht-dutv diesels resulting-;, from'1.—tire addition -of
trap-oxidizer systems.
Installation of trap-oxidizer systems is expected to
result in an average fuel economy penalty of 2 percent.[9]
Estimatina the cost of this penalty over the life of an
LDDV/LDDT reouires that the following information be
specified: cost of diesel fuel, discount rate, average vehicle
miles travelled (VMT) for LDDVs and LDDTs, average LDDV and
LDDT fuel economy, and average LDDV and LDDT lifetime. In this
analysis, the assumptions used are: $1.20/gallon for the
average cost of diesel fuel; a 10 percent discount rate?
average annual VMT of 10,000 for LDDVs and 10,800 for LDDTs:
the estimated 1990 fuel economies for each size class that were
used in determining trap volume requirements; and average
lifetimes of 10 years for LDDVs and 11 years for LDDTs.[11,121
To calculate the cost of the fuel economy penalty, the
estimated 1990 fuel-economv values (II.B.2.) are reduced by 2
percent. Knowledge of the fuel economy and annual VMT allows
-------
8-23
the annual fuel consumption to be determined, which then is
multiplied by $1.20/gallon to yield annual fuel costs. The 10
percent discount rate and the lifetime periods are used to
determine the present value of lifetime fuel expenditures in
the year of vehicle purchase.
The process is reDeated without includinq the 2 percent
fuel-economy penalty, and subtraction of the lower total from
the higher total aives the cost of the fuel-economy penalty to
the consumer. Carrying through these calculations,- the net
present value of the fuel-economv penalty in the year of
vehicle purchase is $33 for small LDDVs, $46 for medium LDDVs,
$52. for. larqe .LDDVs, $41 for small LODTs, and $5.5 .for full-size..
'"iEfedTs.
Increased maintenance costs will result only from
maintenance of the trap regeneration system, since the trap
itself is expected to be maintenance-free and use of the
trap-oxidizer system will have no adverse impacts on other
vehicular maintenance requirements. Regeneration system
maintenance is likely to be limited to replacement of the one
or both of the temperature sensors used for system control.
This "maintenance is estimated to require about one hour labor
and $10 in new parts, and should only be required once durinq
the lifetime of the vehicle. Assuming a labor charge of $25
per hour, the total cost of this maintenance is $35. This
maintenance should occur approximately halfway through the
lifetime of the vehicle, or about five years after the initial
purchase. Discounted to the year of the vehicle purchase, the
regeneration system maintenance cost is estimated to be $22.
•
Use of trap-oxid izer systems will reduce the cost to the
-.;Cpns,umer ¦» .f.o.r -exhaust.,system maintenance.... ;B.y. .usj.agi ;a> . Sifea ini.e-ss
-^t^ei^-exhaust1"-pipe -(to discourage in-tfs*e"~ "trap-"removal*)',' '"th'e""
need for periodic replacement of the standard steel exhaust
Dipe is eliminated. A conservative estimate of one exhaust
pipe replacement, at roughly the midpoint of the vehicle
lifetime (5 years), being eliminated results in consumer
savings of $21 (for small LDDVs and LDD^s, and medium LDDVs) to
$36 (for large LDDVs and full-size LDDTs).[41 As in the
estimated cost of regeneration system maintenance, a 10 percent
discount rate is assumed.
The sum of the increased L^V/LOO'7' initial purchase price,
the cost of the fuel-economy penalty, and the cost of
reaeneration system maintenance, less the savings on exhaust
system maintenance, represents the total cost to the consumer
of particulate control. These costs are summarized in Table
8-5 for each of the five size classes of light-duty diesels,
and range from $210 to $266 per vehicle. Aaainst the net
-------
8-24
Table 8-5
Total Cost to Consumers of Oning and Ooerating a
Liaht-Duty Diesel Equipped With a Trap-Oxidizer (1983 dollars)*
Small
LDDVS
Medium
LDDVs
Larqe
LDDVs
Small
LDDTS
Full-Size
LDcrrs
Trap-Oxidizer System:
Best Estimate Sales Projections
$185
$187
$213
$187
$211
"Worst-Case" Sales Projections
$176
$179
$202
$179
$205
Maintenance Costs -
$22
- $22
$22
$22
"' $22
Maintenance Savings
($21)
($21)
($36)
($21)
($36)
Cost of Fuel Economy Penalty
$33
$46
$52
$41
$55
Total Cost to Consumer:
Best Estimate Sales Projections
$219
$234
$266
$229
$252
"Worst-Case" Sales Projections
$210
$226
$255
$221
$246
Total Cost of Oming and
Operating Vehicle[13]
$14,168
$16,377
$19,418
- ...
- ..
Cost Increase Due to
Trap-Oxidizer
1.5%
1.5%
1.4%
-
-
All' costs 'Ife^-Siscourit^^o" "vear "of!' vSiicl^'.Tpufffh^situsing.'*.,a,."!lb/ percent*
discount rate.
-------
8-25
present value of the cost of owning and operating an T
-------
8-26
Table 8-6
Annual Costs to the Nation of the Base Scenario
for LDDVs and LDDTs (millions of 1983 dollars)
Best Estimate "Worst-Case"
Sales Projections Sales Projections
LDDVS LDDTS LDDVs' LDDTs
Annual Cost:
1987
52
16
95
21
1-988 -
- 60
;18 '
115
23
1989
66
20
131
26
1990
74
22
148
28
1991
76
23
156
31
1992
77
25
164
35
1993
78
26
172
39
1994
79
27
180
42
1995
80
29
187
46
-------
8-27
The estimates of the RPE of manufacturina costs for
liaht-dut-y diesels were based on the application of adjustment
factors to the estimated manufacturinq costs. Additional
adjustment factors were included in the model developed by
Lindgren[51 to comDensate for inflation and production volume.
With the exception of the adjustments for production volume,
these factors are unchanged for the heavy-duty case.
In order to estimate standard averaqe trap production
levels for_ .HDDVs, the number of different trap sizes required -
must be determined. In the Regulatory Analysis for the
proposed heavv-dutv diesel particulate control requlations,[141
the. .assumption was" that four sizes of traps would be required.
to span the entire rancre of HDDVs. The qrouping of HDDVs into
size classes at that time, based on qross vehicle weight (GVW)
classes, is shown below:
GVW classes
IIB*, III, IV
V, VI
VTI
vin
In this analvsis, HDDVs are divided into only three
groups, on the basis of both GVW classes and relative sales.
Classes VII and vm HDDVs are consolidated in one group, and
Class V is placed in the same group as Classes IIB-IV. These ¦
qroups are referred to in the rest of this section as
medium-duty diesels (MDVs), light heavy-duty diesels (LHDVs),
and heavy heavy-duty diesels (^HDVs), in order of increasing
GVW. This is summarized below:
• ,;:-cro:up;r-f;TL ¦ GVW.-.classes. -..
:7'^i esti. i:3:~- •,•»"- ¦«. . * f «
. MDVs IIB-V 8 , 501-19 ,500
LHDVs VI 19,501-26,000
HHDVs VII-VIII 26,001 and over
These groups have the advantage that each contains one of
the three GVW classes that dominate HDDV sales (IIB, VI, VIII),
while GVW classes havincr relatively low sales are grouped with
them through similarity of application. This division is also
consistent with the diesel manufacturers' typical grouping of
HDDVs.[15,161
The standard average production level, for traps for each
of the three LDDV size classes, was estimated in the precedinq
* Class IIB in this analysis refers to all vehicles in the
traditional GVW class II (6,001-10,000 lbs.) that EPA
classifies as heavy-duty (GVW over 8,500 lbs., or frontal
area over 45 square feet, or curb weight over 6,000 lbs.)
Group
2
3
4
GW. M-b:S.)
-------
8-28
section to be 200,000 annuallv. This fiaure was based on the
best estimate diesel sales projectionsf31 and the projected
rates of trap usaqe (Chapter 1) . These projections also
indicate that approximately half as many FDDVs will be sold,
compared to sales of each LDDV size class, in each of the three
groups defined above. The standard average production level
for each HDDV grouo is then 100,000 annuallv.
However, due to the large trap volume requirements for
LHDVs and HHDVs, this analysis assumes that two traps (each
with half the total volume required) , will be fitted to those
vehicles. The standard average trap production levels are then
100,000 for MDVs, and 200,000 each for LHDVs and RHDVs.
Assuming the 12.percent learning curve used in the liqht-dutv
analysis, the adjustment factors for production volume are
1.136 for MDVs, and 1.0 (no adjustment) for LHDVs and HHDVs.
The trap volume requirements are calculated in the
following two sections in the same way that the liqht-duty trap
volume requirements were determined. Trap size is related to
volumetric exhaust flow, which in turn is proportional to fuel-
consumption (inverse of fuel economy). This calculation
requires estimates for the averaqe new-vehicle fuel economy of
each class (MDV, LHDV, HHDV) in the late 1980's and early
1990's. Actual projections of 1990 fuel economy for heavy-duty
gasoline-powered vehicles (HDOVs) [15] were raised by 30 percent
to account for the increased efficiency of diesel engines,
giving the projections of 15.5 mDq (MDVs), 8.4 mpg (LHDVs), and
7.n mpg (HHDVs) used in this analysis. These figures represent
1990 project averaqe fuel economies for new heavy-duty
vehicles. Thus, they are slightlv higher than the fuel economy
Dro jectionsr; used' 'in Chapter ~2, "which represent" th.e entire"
heavy-duty diesei in-use fleet in 1990.
2. Mon-Catalvzed (Corning) Trap
The traD volume requirements of non-catalvzed traps for
heavy-duty applications are based, as in the light-duty case,-
on the successful testing of a 302 cubic inch Corning traD on a
Mercedes-Benz 300D with fuel economy of 26 mpq. The trap
volume requirements that result are 506 cubic inches for MDVs,
934 cubic inches for LHDVs, and 1,122 cubic inches for "HDVs.
As noted above, the maanitude of the trap volume
requirements for LHDVs and HHDVs was high enouqh to assume that
two traps will be fitted, oer vehicle, with the total volume
equal to the required size. The individual trap volumes are
then 467 cubic inches for LHDVs and 5fil cubic inches for HHDVs.
-------
8-29
In section II.A.2., formulae were given that yielded the
RPE of manufacturing cost as a function of trap volume. The
eauations 2A-2C, when adjusted for production level as
discussed in the introduction to this section, become:
For MDVs:
RPE = $26 + 0.358(V) (4A)
For LHDVs and FHDVs: . _ ....
RPE - $23 + 0.318(V) (4B)
Where:
V ¦ volume of trap, in cubic inches.
Substitution of the trap volume requirements for V in
eauations 4A and 4B gives the RPEs of the heavy-duty traps.
The 506 cubic inch traps for MDVs have an RPE of about $207.
For LHDVs, each of the 467 cubic inch traps needed has an
estimated RPE of about $172; the total. RPE for two such .traps
(per-vehicle RPE) is $343 . The 561 cubic inch traps for HHDVs
have an estimated RPE of about $201 each, with a per-vehicle
RPE for two such traps of $403. All of these estimates, which
are based on best estimate sales projections, are shown in
Table 8-7. " —
3 . Catalyzed (Johnson-Matthey) Trap
As in the light-dutv case, calculation of catalyzed trap
volume reauirements is based on the successful testing of a 345
^cubic-' *i-nch_ trap- on-f- a- .-Volkswagen- Rabbit • -(:fuel;----economy of- ;-4 2^
mpgT) . ~ The* projected fuel economy "Of 'var ious- HD'DVs" waV related"
to this fuel economy to obtain catalyzed trap sizes. The
results are: 935 cubic inches for MDVs, 1,724 cubic inches for
LHDVs, and 2,070 cubic inches for HHDVs. The assumption that
the volume requirements for LHDVs and HHDVs would be met by
fittinq two traps of equal volume is also used here. The
single-trap volumes are then 862 cubic inches for LHDVs and
1,035 cubic inches for HHDVs.
Equations 3A-3C were used in section II.A.3. to calculate
the RPE of the manufacturing costs for lioht-duty catalyzed
traps. when the adjustment factors for heavy-duty production
levels are applied, the new equations are:
-------
8-30
Table 8-7
Heavy-Duty Trap Costs (1983 dollars)
Best Estimate Sales Projections
Non-Catalyzed Catalyzed
Vehicle Class Trap Trap
MD^s $207 $636
LHDVs $343 $1,051
FHDVs $403 $1,252
Worst Case Sales Projections
Non-Catalvzed Catalyzed
Vehicle Class Tap Trap
MDVs $183 $560
LWOVs $274 $1,007 '
HHDVs $40 3 $1,252
-------
8-31
For MDVs:
RPE = $26 + 0.652(V) (5A)
For LHDVs and HHDVs:
RPE = $23 + 0.583(V) (5B)
Where:
V = volume of trap, in cubic inches.
Therefore the .MDV trap, with a volume of 935 cubic inches,
has an estimated RPE of $636. Each of the 862 cubic inch traps
for LHDVs has an estimated RPE of about $526, for a per-vehicie
RPE of $1,051. The RPE of each 1,035 cubic inch RHDV trap is
estimated to be about $626, or $1,253 for the two traps
required. These estimates are all shown in Table 8-7.
All of the estimates for heavy-duty traps discussed above
are based on the best estimate sales projections. Under the
"worst-case" sales projections, sales of MDVs and LHDVs would
double, with trap production for these vehicles also doubling.
As was discussed in section IT.B.l., the 12 percent learninq
curve assumed indicates that trap costs would be decreased 12
percent by a doubling of production. Since HHDV sales already
represent nearly all sales in GVW Classes VII and VIII, they
remain relatively constant under both sales projections. Thus,
the "worst-case" sales projections have an insignificant effect
on estimated HHDV trap costs. All of this information is
summarized in Table 8-7.
Ji. Regeneration ?,ys_t.e.m.jz.os tj>.. . . , . -...F
Section T.C. described the components of both catalyzed
and non-catalyzed trap regeneration systems. These basic
systems will also be used for HDDV applications, with two
changes that will have an impact on the cost estimates
presented in Table 8-2. The use of two traps on LHDVs and
HHDVs means that the quantities required of some regeneration
system components will be doubled. In addition, the difference
in the sizes of LDDV and HDDV engines will have an effect on
the costs of the required stainless steel exhaust pipe, as
discussed later.
Table 8-8 summarizes the estimated RPE of manufacturing
cost for both catalyzed and non-catalyzed trap regeneration
systems, for each of the three groups of HDDVs. The estimates
shown include the doubled quantity of some of the components
required for LHDV and HHDV applications.
-------
8-32
Table 8-8
Heavy-Duty Regeneration
Svstem Costs (19A3 dollars)
Retail Price Eouivalent
Hardware Item
MDDV
LHDV
HHDV
Non-Catalyzed Trap:
Burner Head
$7
$14
$14
Fuel Delivery Svstem
$9
$18
$18
Iqnition System*
$5-26
$10-31
$10-31"
Auxiliary Combustion Air System
$30
$30
$30
Exhaust Diversion System*
$11-14
$15-18
$15-18
System Control:
TemDerture Sensors
$1?
$24
$24
ECU
$37
$37
$37
Subtotal*
$111-135
$148-172
$148-172
Stainless Steel Exhaust PiDe**
$33
$'53
$89
!
Total*
$14 3-168
$201-225
$237-261
Catalyzed Trap:
Delayed In-Cylinder Fuel
$30
$30
$30
Injection Mechanism
Auxiliary Comhustion Air
$6
$12
$12
System (Reed Valve)
-
System Control.:. ... r , .
....... . ,i,,....
¦ - ----- Sensors
$12
$24'
- - $24
ECU
$37
$37
$37
Subtotal
$85
$103
$103
Stainless Steel Exhaust Pipe**
$33
$53
$89
Total System Cost
$118
$156
$192
Explanations of ranoes in costs are in section IT.B.4.
For exhaust pipes only, the assumed averaqe production
volume is 100,000 units.
-------
8-33
In section II.B.4. it is shown that, of the current $75
cost of an electronic control unit (FCU),[21 about $10 is
attributable to particulate control on a per-vehicle basis.
Since ECUs are not projected to be in general use on heavy-dutv
vehicles before 1988, but will be required under the base
scenario, a greater share of the total cost . should be
attributed to particulate control. This analysis assumes that
the ECU will be applied solely for emission control purposes,
and that it will be used for both particulate and NOx control.
Thus, it's cost is divided equally between particulate and NOx
control functions, yielding the ECU cost estimate for
particulate control of $37 shown in Table 8-8.
~ The'"additional costs of a stainless steel exhaust pipe for
light-duty diesels were estimated (II.B.4.) as about $16 for 4-
and 6-cylinder engines, and about $27 for 8-cvlinder enqines.
These costs presume a single exhaust manifold with both 4- and
6-cylinder enqines, and a crossover system with the 8-cylinder
enaine. In the case of HDDVs, the majority of engine exhaust
systems are the sinqle, non-branching type. Fewer systems are
of the dual exhaust type, where two entirely separate exhaust
systems are used.[141 This analysis assumes that all HDDVs in
GVW 'Classes IIB-V are manufactured 'with single exhaust systems,
while for Class VI . and laraer HDDVs, 75 percent are
manufactured with sinqle exhaust systems and 25 percent with
dual exhaust systems.[141
In the Draft Reaulatory Analysis to the Heavy-Duty Diesel
Particulate NPRM,ri4] it was stated that the basic design of
the LDDV 6-cylinder engine exhaust pipe should be the best
analogue of the exhaust pipe design of HDDVs with sinqle
exhaust systems. This is also assumed in these estimates. For
HDDVs -.with..-dual exhaust systems, the. result-inq ^rjso.s West-imates-,
ar e- -doubled-- -(-i.e., - -two-sta inles;s steel- -exhaust: • pipes 1 are-
assumed to be used).
The estimated cost of converting from a standard steel to
a stainless steel exhaust pipe for an LDDV with a 6-cylinder
enqine was qiven (II.B.4.) as $16, which included credit for
the deleted standard steel pipe. The corresponding costs for
HDDVs are calculated by assumina a direct relationship of
material cost to engine displacement. The typical LDDV
6-cylinder engine is assumed to have displacement of 3.7L. The
typical engine displacements for heavy-duty diesels are assumed
to be 6.2L (MDVs) , 8.2L (LHDVs) , and 13.9L (HHDVs) . For GVW
Classes VI, VII, and VIII vehicles (LHDVs and HHDVs), the
average per-vehicle cost is calculated bv assumina that 75
percent of these vehicles will require one pipe and 25 percent
of them will require two, as discussed above.
-------
8-34
The . result of
per-vehicle average
steel exhaust pipes:
HHDVs.
these calculations
RPE of manufacturing
$33 for MDVs, $53 for
is the estimated
cost for stainless
LHDVs, and $89 for
These costs are also shown in Table 8-8. Except for the
exhaust pipes and the doubled quantities of some components,
the cost estimates in Table 8-2 for light-duty trap
regeneration systems remain unchanged in ^able 8-8.
5. Total Trap-Oxidizer System Costs
The sum of the estimated costs" of the trap and
correspondina regeneration system is the estimated total
trap-oxidizer svstem cost. These sums are shown, for both trap
types and under both sets of sales projections, in Table 8-9.
As was the case in the light-duty analysis, the cost
ranges are small relative to the absolute costs. Thus, only
the midpoints of- these ranges are used in Table 8-9 and in the
remaining analysis. The non-catalyzed trap, which is much less
expensive and appears to be the preferred design of heavy-duty
diesel manufacturers, is the basis of the rest of the analysis.
C. Economic Imnact on Manufacturers
In this section, the impact of the base particulate
control scenario on manufacturers' heavy-duty diesel sales,
capital investments, and cash flow are estimated. As for
light-duty, only the costs of the trap-oxidizer system are
considered. Certification costs have already been shown to " be
negligible.;,f..l41;. .. .. ...
1. Impact on Manufacturers' Sales
Estimatina the impact of the base scenario on HDD sales is
considerably more difficult than was the case for light duty.
There are two main reasons *or this. First, little research
has been conducted into the economic elasticities at work in
the heavy-duty diesel market, and relevant data are scarce. In
addition, there are complicating factors such as the division
of heavv-duty diesels into three aroups (MDV, LHDV, «HDV), and
the relatively insignificant sales of vehicles in some GVW
Classes (III, IV, and V). Thus the analysis and estimates
presented in this subsection must be considered to be, at best,
rouqh approximations.
The discussion and the estimated impact of the base
scenario on sales in each HDD group presented in this section
are based primarily on a report recently prepared for EPA by
-------
8-35
Table 8-9
Total Heavy-Duty Trap-Oxidizer
Svstem Costs (1983 Dollars)
Best Estimate Sales Projections
Non-Catalyzed
Vehicle Class Trap
MDVs _ -..-$36-3
LHDVs $556
HHDVs V. $6 52
Worst Case Sales Projections
Non-Catalyzed
Vehicle Class Trap
MDVs $339
LHDVs $487
HHDVs $652
Catalyzed
Trap
$754
$1,207
$1,444
Catalyzed
Trap
$678
$1,163
$1,444
-------
8-36
Jack Faucett Associates (JFA).[17] JFA conducted a thorouah
literature search and surveyed a number of knowledgeable
individuals, includina members of the heavv-dutv vehicle and
enaine industries, in order to develop the economic elasticity
estimates used here.
Two kinds of price elasticity, own-price and cross-price,
must be considered. Own-price elasticity refers to the chanqe
in the demand for vehicles of a aiven cateqory resulting from a
chanae in the purchase price of vehicles in that same
cateaorv. Cross-price elasticity takes into account the shifts
that may occur, from diesel to gasoline-fueled enaines or
conversely, as a result of chanaes in the Durchase price of
vehicles of one or both engine types within a given category.
In the heavy-dutv market, distinct own-price elasticities
exist for each engine type (diesel or gasoline fueled) , within
each Gvw class (TIB through VTII). JFA supplied estimates of
own-price elasticity for HDDs in Classes IIB, VI, VII, and
VIII; no estimates were given for Classes III, IV, and V due to
low sales.[17] These estimates are applied to the three groups
under consideration here by assuming that own-price elasticity
for MDVs is approximately equal to that of Class IIB alone, due
to the very low sales of vehicles in the other GVW classes.
HHDV own-price elasticity is approximated by the sales-weighted
average of the elasticities of Classes vn and VIII. The
estimates for Class VI are also the estimates for LHDVs, by
definition of LHDV.
. - The best estimate and "worst-case"' sales Drojections, for
each of the three. HDD groups.., for 1990-and.--1995 -are . shown--in
Table"' • .8-in - Onlv-- the"* sales projections under the- relaxed
regulatory scenario are aiven. Since there is considerable
uncertainty associated with the elasticity estimates used, the
impact on sales of the base regulatory scenario are given in
Table 8-10 as percent reductions from relaxed scenario sales.
Cross-price elasticity is a directional concept, dependina
on whether "from diesel to gasoline fueled" or "from gasoline
fueled to diesel" is beina considered. In this analysis only
the former is of interest: Given an increase in the purchase
price of HDDs in a given category, the own-price elasticity
estimates how many sales are lost in that category, and the
cross-price elasticity estimates how many of those "lost" sales
are compensated for by increased sales of gasoline-fueled
engines in the same category.
The uncertainties in the cross-Drice elasticity estimates
used are fairly substantial. Although not shown in Table 8-10,
the results of using the estimated cross-price elasticities are
discussed below.
-------
8-37
Table 8-10
Heavy-Duty Diesel Sales Projections
(in thousands)
Best Estimate Sales Projections
Reduction Due.
Vehicle Class 1990 199 5** to Base Scenario***
MDVs
LHDV.s
HHDVs
124
94
159
170
126
186
4.8%
2.2%
1.0%
Worst Case Sales Projections
Vehicle Class 1990 1995**
MDVs 248 340
LHDVs 188 2 52
HHDVS 159 186
Reduction Due
to Base Scenario***
475%
2.2%
1.0%
* California sales included.
** fhese sales fiqures are extrapolated from EPA sales
projections for 1985 and 1990.
*** Percent reduction in relaxed scenario sales, applicable to
both 199* and 1995 projections.
-------
8-38
Of the 4.8 percent reduction in MDV sales projected to
occur under the base control scenario, over a third are
estimated to be made up by increased sales of gasoline-fueled
enaines in Classes IIB-V. Thus, the net reduction in sales of
all enaines in Classes IIB-V is estimated to be approximately 3
percent. Similarly., the net reduction in LHDV sales is
estimated to be approximately 2 percent. For HHDVs, a drop in
sales of about 1 percent is projected to occur under the base
scenario, and only about one in 50 of those "lost" sales is
projected to be offset by new gasoline-fueled engine sales in
Classes VII and VIII.
It should also be noted that the own-price and cross-price
elasticities estimated by JFA were based only on changes in the
initial purchase price. The effects of increases in operatino
and maintenance (O&M) costs are more difficult to incorporate
into the model. In this analysis, the increase in O&M costs
(net present value in year of vehicle purchase, 10 percent
discount rate) .was considered to be part of the initial
purchase price increase. Although this is not appropriate,
strictly speakina, it is an adequate approximation when the
uncertainties inherent in the elasticity estimates are taken
into account.
-2* Capital Investment and Cash Flow Effects
Implementing a trap-based particulate standard for
heavy-duty diesels should have only minor effects on the
capital expenditures of HDDV manufacturers. The reasons are
basically -the same as discussed for light-dutv in section
I.I. B. , and a r e , b r. i e f ly.. r.eca ppe d ..be lpw... .
It is quite unlikely that any heavv-dutv manufacturer will
choose to make the necessary investments for the production of
trap-oxidizers, as the sophisticated technology required has
already been developed bv other, firms. In addition, the
production volumes of most individual manufacturers will be far
too small to justify establishment of in-house trap-production
capability. Thus for heavy-duty as well as light-duty, the
bulk of the investments required for trap-oxidizer production
will be financed by emission control equipment manufacturers.
Future R&D investments by the manufacturers are difficult to
estimate, but should not be so high as to adversely affect
other investment plans.
The cash flow impact of these regulations is limited to
the inventory of traps, individually and on partially
manufactured HDDVs. This investment is recovered upon sale of
the trap-equipped HDDV, and the sales turnover period of HDDVs
is short (generally less than four months) . The short
-------
8-39
inventory period, and the relatively small amount of cash
represented, should not sianificantly affect the cash flow of
any manufacturer.
D. Total Cost to the Consumer
The total cost to the consumer is the sum of the costs of
the trap-oxidizer system, shown in Table 8-9, and the costs of
the 2 percent fuel-economy penalty[41 and increased maintenance
costs, less any maintenance savings. As in the light-duty
analysis, it is assumed that manufacturers pass all of their
costs increases throuah to the retail purchaser.
The costs of the 2 percent fuel-economy penalty are
estimated by the same methods used for light-duty diesels in
section II.D. The information used in this calculation is:
$1.20 per gallon average diesel fuel cost; 10 percent discount
rate; new-vehicle fuel-economy estimates of 15.5 mpg (MDVs),
8.4 mpg (LHDVs) , and 7.0 mpg (HHDVs) ; annual average VMT of
12,000 (MDVs), 20,000 (LHDVs), and 47,500 (HHDVs); and lifetime
average VMT of 120,000 (MDVs), 200,000 (LHDVs), and 475,000
(vwdvs). when this information is used as described earlier,
the net present value of the lifetime fuel-economy penalty, in
the year of vehicle purchase, is $126 (MDVs), $386 (LHDVs), and
$917 (HHDVs). This is summarized in Table 8-11.
The trap should be maintenance-free, but the regeneration
system will require maintenance once during the lifetime of the
HDDV, after approximately five years of operation. For
light-duty diesels, the discounted cost of regeneration system
maintenance is estimated at $22 (Table 8-5) . This cost should
be applicable without adjustment to MDVs, which will be
:eguipoed w.ith a sinale trap. -. For LHDVs and - HHDVswith- two-
traps per -vehicle, this estimate is simply doubled to $44"."-
Table 8-11 also shows these estimates.
A maintenance savings will result from the use of
stainless steel exhaust pipes, which eliminate the need for
periodic replacement of standard steel exhaust pipes. On
average, the total per-vehicle savinas would range from $39
(MDVs) to $97 (HHDVs) over the vehicle lifetime, using a 10
percent discount rate and an appropriate schedule for HDDV
standard steel exhaust pipe replacement.f14]
The components of total consumer cost discussed, as well
as the totals, are shown in Table 8-11. The total consumer
costs are given for both best estimate and "worst-case" sales
projections. Also in Table 8-11 is the estimated overall cost
of owning and operatina an HHDV over its lifetime, in terms of
net present value in year of purchase (1983 dollars).[181 As
can be seen, the impact of particulate control on this overall
cost is small, about 0.6 percent.
-------
8-40
Table 8-11
Total Cost to Consumers of Owninq
and Operating a Heavv-Duty Diesel Equioped
with a Trap-Oxidizer (1983 dollars)*
MDDV LHDV- HHDV
Trap-Oxidizer System:
Best Estimate Sales Projections $363
"Worst-Case" Sales Projections 339
Fuel Economy Penaltv $126
Maintenance Costs $22
Maintenance Savinqs ($39)
Total:
3est Estimate Sales Projections $472
"Worst-rase" Sales Projections $448
Total Cost of Ownino and
Operating a HHDV[161
Cost Increase Due to - 0.6%
Trap-Oxidizer
All costs are discounted to the year of vehicle purchase
usinq a in percent rate.
$556 $652
$487 $652
$386 $917
$44 $44
($61) ($97)
$925 $1,516
$856 $1,516
$274,911
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8-41
E. Annual Costs
The annual costs of the base regulatory scenario are
shown, for the vears 1988 to 1995, in Table 8-12. These costs
were calculated by multiplyinq the net present value of the
total cost to the consumer, per vehicle, by annual sales.
The. costs summarized in Table 8-12 are shown for two
possible situations: trap-oxidizers are applied to all PDDVs,
and to only 70 percent of HDDVs. As .was discussed in Chapter
1, the lower trap usage rate would be adequate if emissions
averaaina is made available to HDDV manufacturers and 85
percent efficiency ceramic traps are used on all trap-equipped
vehicles.
-------
8-42
Table 8-12
Annual Costs
to the Nation of the Base Scenario for
Peavv-Dutv Diesels (millions of 1983 dollars}
Best Estimate Sales "Worst-Case" Sales
Projections Projections
Trap Usage Trap usaae
70% 100% 70% 100%
Annual Tost:
1988 239 341 325 464
1989 251 358 344 491
1990 262 375 362 517
1991 295 422 402 574
1992 ... 328 469 443 633
1993 361 516 480 686
1994 395 564 521 744
1995 430 614 564 805
-------
OMSAPC
References
1. "Trap-Oxidizer Feasibility Study," U.S. EPA, OANR
C, ECTD, SDSB, March 1982.
9
2. "Estimated Costs of Diesel Engine Vehicle Exhaust
Particulate Filter Regeneration Hardware," Mueller Associates,
December 7, 1982.
3. "The Impact of Light-Duty Diesel Particulate
Standards on the Level of Diesel Penetration in the Light-Duty
Vehicle and Light-Duty"Truck Markets," Jack Faucett Associates,
EPA Contract No. 68-01-6375, November 30, 1982.
-4. "Regulatory ""Analysis of the Liqht-Duty Diesel
Particulate Regulations for 1982 and Later Model Year
Light-Duty Diesel Vehicles," U.S. EPA, OANR, OMSAPC, ECTD,
SDSB, October 1979.
5. "Cost Estimations for Emission Control Related
ComDonents Systems and Cost Methodoloqy Description," L.
Lindaren, EPA-46.0/3-78-006, March 1978.
6. Oral Communication with the Bureau of Labor
Statistics.
7. "Summary and Analysis of Comments on the Notice of
Proposed Rulemaking for the Control of Light-Duty Diesel
Particulate Emissions from 1981 and Later Model Year Vehicles,"
U.S. EPA, OANR, OMSAPC, ECTD, SDSB, October 1979.
8. "Cost Estimations for Emission Control Related
Components/Systems and Cost Methodology Descriotion--Heavy-Duty
Truck," L. Lindgren, EPA-460/3-80-001, February 1980.. ... .
9. The Effect of Trap Oxidizers on Fuel Consumption,
EPA memorandum from J. Alson and R. Kanner to Richard A.
Rvkowski, Standards Development and Support Branch April 1984.
10. "The Future of the Diesel Engine: Opportunity and
Risk for the 1980's," Chase Econometrics, June 1982 (not
available to the public until March 1983).
11. Determination of Useful-Life Values for Light-Duty
Trucks and Heavv-Duty Enaines, EPA memo From R. Johnson,
Standards Development and Support Branch To Public Docket No.
A-81-11, Index No. TV-B-3, December 13, 1982.
12. "Averaqe Lifetime Periods for Liqht-Duty Trucks and
Heavy-Duty Vehicles," U.S. EPA, OANR, OMSAPC, ECTD, SDSB,
November 19 79.
-------
References (cont'd)
13. "National Transportation Statistics," Research and
Special Programs Administration, Department of Transportation,
August 1979.
14. "Draft 'Reaulatory Analysis, Heavy-nutv Diesel
Particulate Regulations," U.S. EPA, OANR, OHSAPC, ECTD, SDSB,
December 23, 1980.
15. "The Highway Fuel Consumotion Model, Eighth
Ouarterly Report," prepared by Energy and Environmental
Analysis, Inc., U.S. Department of Energy Contract No.
DE-AC01-79PA-70032, Task No. 13, July 1, 1982.
16. "Data Resources U.S. Long-Term Review," TRENDLONG
0682, Data Resources Incorporated, Summer 1982.
17. "Estimation of Economic Elasticities in the
Heavy-Duty Vehicle Market," Jack Faucett Associates, EPA
Contract No. 68-01-6375, February 23, 1983.
18. "Operating Costs: Up 20 Percent," Heavy-Duty
Trucking, July 1981.
-------
CHAPTER 9
COST EFFECTIVENESS
I. Introduction
Cost effectiveness is a relative measure of the economic
efficiency of taking an action to achieve a specified goal. It
is primarily useful in comparing alternative means of achieving
that goal. In the context of this study, the goal is to reduce
particulate emissions, or perhaps more importantly, to reduce
ambient levels of particulate where people are exposed. In
this, case, cost effectiveness is expressed in terms of- the
dollar cost per ton of particulate emission controlled.
The primary, purpose of this chapter is to - determine the
cost effectiveness of the base scenario for each diesel vehicle
subgroup so that comparisons among these subgroups can be made,
and so that these mobile source strategies can be compared on a
relative basis to non-mobile source strategies. The baseline
or starting point for evaluating the cost effectiveness of the
base scenario is the relaxed scenario, which itself provides
some level of control. The relaxed scenario was chosen as the
baseline instead of a totally uncontrolled case for two
principal reasons.
First, the 0.60 g/mi standards for light-duty diesel
vehicles and trucks (LDDs) have already been implemented. For
heavy-duty diesel vehicles (HDDVs), compliance with the 0.60
g/BHP-hr standard should not be "'difficult and would likely
preceed a trap-based standard. Because of this, it is most
appropriate to evaluate the base scenario against the baseline
which exists at the time these new requirements become
effective, i.e.,_the relaxed scenario.
Second,- the- relaxed "scenario ' i:tself~ represents a very,,
-small degree of control. Almost all LDDs are already emitting"
at or below the standards. Fleetwide, most HDDs are emitting
very near the standard. Therefore, there is little practical
difference between the relaxed scenario and a totally
uncontrolled case, although use of the relaxed scenario will
make the cost effectiveness of the base scenario slightly wors.e
than if the uncontrolled case were used. Hence, for both of
these reasons, it is appropriate to evaluate the base scenario
as being incremental to the relaxed scenario. (The base and
relaxed scenarios are described fully in the Introduction.)
-------
9-2
To determine cost effectiveness, two pieces of information
are necessary: the costs and emission reductions of the
strategies to be examined. The measure of cost will be the
annualized net present value of all purchase, operatinq, and
maintenance costs. ' Emission reductions will be determined on
an annual basis in terms of either total, inhalable or fine
particulate.* The three classes of suspended particulate as
examined in order to focus the analysis on the most important
particulate matter with respect to public health and welfare.
As determined in Chapter 6, fine and inhalable particulate have
the primary effect on human health. As determined in Chapter
4, only fine particulate affects visibility. As outlined in
Chapter 7, all particulate can participate in soiling.
The remainder of this analysis is divided into three major
sections. The first section estimates the cost-effectiveness
({/metric ton) for the base control scenario (relative to the
relaxed scenario) and concludes with a comparison of these
figures for the various diesel subgroups on a nationwide and
urban basis. The second section of the analysis will estimate
cost-effectiveness values for several stationary sources. The
third' section will conclude the analysis by: 1) applying a
discount factor to the cost-effectiveness values for both
mobile and stationary sources to account for their relative air
quality impacts, and 2) comparing the cost-effectiveness of
diesel particulate control to those of stationary sources. -----
It should be noted that while cost-effectiveness analysis
is valuable in discernino relative economic efficiencies of
various actions to achieve a specific goal, it cannot provide
definitive information on the point at which the costs of
controlling any particular source exceed the economic bene-f i-t-s-
(i.e., dollar value) associated with control. This latter type
of evaluation can be made only by using cost-benefit analysis,
which is beyond the scope of this report. A cost-benefit study
of mobile source diesel particulate standards has been recently
completed for EPA under contract [1], and the reader is referred
to that study and others in the literature for more information
on the benefits of controlling diesel particulate.
Total particulate is all suspended particulate matter
regardless of diameter, inhalable particulate is
considered to be all particulate matter less than 10
micrometers in diameter, and fine particulate is
considered to be all particulate matter less than 2.5
micrometers in diameter.
-------
9-3
II. Cost Effectiveness of Controlling Particulate Emissions
from Diesel Vehicles
A. Methodology
In this section, the cost effectiveness of proceeding from
the relaxed to the base scenario for five diesel vehicle
subgroups will be estimated and compared. These subgroups
-include light-duty diesel vehicles (LDDVs), light-duty - diesel
trucks (LDDTs) , and three subqroups of HDDVs: medium-duty
vehicles (MDVs), light heavy-duty vehicles (LHDVs), and heavy
„heayy-duty. vehicles ;{HHDVS)_-s_ . .. . . . -\ —• —
Most previous EPA cost-effectiveness analyses for mobile
source emissions have determined cost effectiveness using total
lifetime costs discounted to the year of vehicle purchase and
undiscounted lifetime benefits. However, this approach is
somewhat simplistic, since it disregards the fact that the
emission reductions cannot be obtained at the time of vehicle
purchase, when the cost of control is determined. Because of
this, the cost-effectiveness value calculated is entirely
dependent on the point in time costs are determined, which is
somewhat arbitrary.
It would be more appropriate if costs could be allocated
to each period of time in which benefits were produced arid in
proportion to the size of these benefits. The result would be
a cost effectiveness which is applicable at any point in that
life as well as over the entire life of the vehicle.
" This can be done here for mobile sources through the use
;;of two -^simplifying assumptions which will--- not "affect 1 thTe
accuracy of *the" "cost-effectiveness comparison's".*"'Fir£t;" it wiir
be assumed that the number of miles a diesel is driven annually
is constant throughout its useful life. This simplifies the
determination of the miles producing emission reductions each
year. Second, the per-mile emission reduction occurring at the
vehicle's half life will be assumed to apply throughout its
life. This assumption allows direct use of the emission
results of Chapters 1 and 2, since the analysis there also
assumed that emissions were constant with mileage except for
the effect of trap failure. This only results in a slight
underestimation of emission reductions early in life, with a
compensating overestimation late in life. The overall effect
on cost effectiveness is negligible.
With the use of these two assumptions, the annual emission
reduction throughout a vehicle's life becomes constant and the
cost of control can simply be allocated equally (using discount
theory) to each year of the vehicle's life. This latter
I
-------
9-4
annualized cost is simply an annuity equivalent to the total
cost of control discounted to the year of vehicle purchase,
which was determined in Chapter 7. Costs will be addressed
first and then emission reductions, followed by calculation of
the cost-effectiveness values.
3. Costs of Control
Essentially all of the cost information necessary for the
cost-effectiveness calculations has been developed in Chapter
8. Tables 9-5 and 9-11 of that chapter contain detailed cost
information on the purchase and operating cost impacts for
LDDVs, LDDTs, and HDDVs. These costs are given in 1983
dollars, discounted at 10 percent to the year of vehicle
purchase.
This cost-effectiveness analysis does not require the
level of disaggregation given in Table 9-5 for LDDVs and LDDTs
(e.g., small, medium, and large LDDVs as opposed to simply
LDDVs). therefore, the costs presented will be combined to
obtain total lifetime consumer costs for LDDVs and LDDTs. As
outlined in Chapters 1 and 8, the largest vehicles are likely
to be equipped with trap-oxid izers first, since they are the
highest emitters. Since the trap usage rates under the base
scenario (22 percent for LDDVs and 9 percent for LDDTs) are
below the projected sales fractions of larae LDDVs (26 percent)
and full-size LDDTs (66 percent ) , [21 only the largest size
vehicles in each class are likely to have traps. Thus, the
lifetime costs for these larqest vehicles will be used here.
Table ...9-1 shows ,.thj», disco „ lifetime., consumer..,-....
'.;Vr.e.©stsJ^ac--. -eac'h--"of-.-the five- di-esel vehicle groups . ¦ (HHDV --costs
can be take directly from Chapter 8.) Only those costs for the
best estimate sales scenarios are shown. Costs for worst case
sales would be 0-4 percent lower, because of economies of
scale. (Each vehicle class has a different factor since the
relationship between best estimate and worst case sales is
different for each vehicle class.)
These discounted total costs can be annualized (at
mid-year) over the appropriate average lifetime for each of the
diesel vehicle classes using present value theory. The
expected vehicle lifetimes and the resultant annualized costs
are shown in Table 9-1.
For LDDVs and LDDTs, trap-oxidizers will be used only on
the portion of each manufacturer's sales necessary to bring the
manufacturer's sales-weighted particulate levels down to the
required standard. Since the particulate reduction benefits
will be measured on a fleetwide basis, but costs shown in Table
-------
9-5
Table 9-1
Base Scenario Costs (1983 dollars)*
LDDV LDDT MDV LHDV HHDV
Lifetime Costs for $266 $252 $472 $925 $1,516
Base Scenario
Vehicle 10 yrs 11 yrs 8 yrs 11.5 yrs 10.5 yrs
Lifetime
Annualized $41 $37 $84 $132 $228
Cost For A
Trap-Equipped
Veh icle
Percent of 22.3 7.6 100 100 100
Vehicles with
Trap-Oxidizers
Fleet Average $9.20 . $2.80 $84 $132 $228
Annualized
Cost Per
Vehicle
+ Discounted at 10 percent to year of vehicle purchase, best
estimate sales.
-------
9-6
9-1 only apply to a portion of the fleet, these costs must be
spread over the entire fleet. This can be accomplished by
multiplying the annualized costs of Table 9-1 by the percent of
vehicles requiring traps (taken from Tables 1-4 and 1-7 of
Chapter 1). Since the base scenario does not assume the
availability of an averaging concept for HDDVs, this affects
only LDDVs and LDDTs. (without averaging, all HDDVs will use
trap-oxidizers and no adjustment needs to be made.) These
fleet-average annualized costs for LDDVs and LDDTs are also
shown in Table 9-1. With averaging, about 70 percent of all
HDDVs would require traps and the fleetwide costs shown in
Table 9-1 would be reduced by approximately 30 percent.
C. Diesel Particulate Emission Reductions
Calculation of the annual diesel particulate emisson
reduction accompanying the base scenario requires information
on annual vehicle miles travelled (VMT) and the emission rates
under the two control scenarios. Table 9-2 shows the average
annual mileage for each of the five diesel vehicle subgroups,
which were derived from each subgroup's average lifetime
mileage and average life (also shown).
Vehicle particulate emission rates (g/mi) tend to increase
qraduallv with mileage, in a manner in which can be
characterized as linear over the life of the vehicle. Thus,
for either the relaxed or base scenario, one can conceptualize
a stream of annual particulate emissions, increasing by a
constant amount each year. If the emissions in each year for
the base scenario were subtracted from the emissions in each
year for the relaxed scenario, a stream of emission reductions
would be created. Costs could then be allocated to this stream
of benefits to provide a constant and applicable cost,
effectiveness throughout the vehicle's life.
As already mentioned in the previous section, a close
approximation to this can be obtained by ignoring the small
change in emissions with time and determining the emission
reduction at the vehicle's half life. The half life for LDDVs
and HDDVs is approximately the fifth year; for LDDTs it is the
sixth year.
Half-life emission rates for the five diesel vehicle
subgroups were taken from Chapter 2, and are shown in Table
9-2. Unlike LDDs, the half-life emission rates for HDDVs
differ somewhat for each model year under both scenarios
because the fuel efficiencies and, hence, emission
characteristics of these vehicles are expected to improve in
future years. To simplify the cost-effectiveness computations,
half-life emission rates for 1990 model year HDDVs are used.
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9-7
Table 9-2
LDEtf
LDDT
MDDV
LHCO/
HHDEV
Average Lifetime
Mileage
100,000
120,000
U0,000
268,000
529,000
Lifetime (years)
10
11
8
11.5
10.5
Average Annual
Mileage
10,000
10,900
13,800
23,300
50,100
Vehicle Brass ion Rates at Half Life
(g/mile)
Relaxed Scenario
.27.0
.280
.818
1.381
2.151
Base Scenario
.204
.261
.381
.642
1.034
Difference
.066
.019
.437
.734
1.117
Annual Emission
Reduction (grans)
660
210
6,030
17,100
55,960
(metric tons)
6.6 X 10"4 2
.1 X 10-4
6.03 x 10+3
0.0171
0.0560
-------
9-8
Also, to further simplify the analysis, a sinale emission rate
is used to represent Classes lib and III-V as MDDVs. This was
determined by sales-weighting the emission rates for the two
classes using projections for the 1990 model year from
Reference 3. These, simplifications have no significant effect
on the results of this analysis. It is also worth noting that,
for the base scenario, where trap-oxidizers are used on all
vehicle subgroups to gain the emission reductions, the emission
rates include the effect of trap-oxidizer failures.
The annual emission reductions for each diesel vehicle
subgroup can -ow be calculated by simply finding the difference
in the emiss.jn rates from the relaxed and base scenarios and
multiplying by the average annual mileage. These are shown in
Table 9-2 in both grams and metric tons of diesel particulate
controlled.
Diesel particulate matter is very small in size, with mass
mean diameters varying from 0.05 to 0.2 micrometers. As such,
essentially all diesel particulate falls into the fine
particulate category.[4,5,6] Therefore, the emission
reductions for total particulate given in Table 9-2 also
represent the emission reductions for inhalable and fine
particulate.
D. Cost-Effectiveness Values for Diesel Vehicles
The cost effectiveness of the base scenario is computed by
dividing the fleet average annualized costs from Table 9-1 by
the annual emission reductions from Table 9-2. The resulting
cost-effectiveness values for the five diesel classes are given
in Table 9-3 in the form of 1983 dollars per metric ton. The
cost effectiveness of diesel particulate control is essentially
equivalent for LDDVs and LDDTs {at $13,000-14,000 per metric
ton) , but appears to be better for MDVs and especially LHDVs
and HHDVs.
These cost-effectiveness values presume the availability
of averaging for LDDVs and LDDTs, but not for MDVs, LHDVs, or
HHDVs. In Chapter 8, it was determined that HDDV compliance
costs would drop approximately 30 percent if an averaging
approach was used. Revised values incorporating, averaging for
HDDVs .are also shown in Table 9-3. As can be seen, this change
makes the control of HDDVs even more attractive relative to
that of LDDVs or LDDTs.
It is important to note that these cost-effectiveness
values consider all emission reductions, regardless of whether
the reduction occurs in an urban or rural area. Since the
great majority of Americans exposed to violations of the NAAQS
-------
9-9
Table 9-3
Cost-Effectiveness Values
Total, Inhalable, and Fine Diesel Particulate*
lpov loot mr urn hhdv
Average $9.20 $2.80 $84 $132 $228
Annualized
Cost ($)
Annual Emission 6.6 x 10~4 2.1 x 10~4 6.03 x 10"3 0,0171
0.0560
Reduction
(metric tons)
Cost Effectiveness 13,900 13,300 13,930 7,740 4,070
($/metric ton)
Cost Effectiveness 13,900 13,300 9,750 5,420 2,850
with Averaging
for HDOVs
($/metric ton)
Urban Cost 23,400 27,200 20,000 11,100 10,600
Effectiveness
with Averaging
for HDDVs
($/metric ton)
* Cost-effectiveness values are the same for total, inhalable and fine particulate,
-------
9-10
for particulate matter live i n urban areas and since diesel
particulate concentrations are greatest in these locations, the
control of diesel particulate in urban areas should receive the
greatest emphasis. This is not to suggest that the benefits
associated with controlling diesel particulate in rural areas
are unimportant, however. In fact, diesel particulates emitted
in rural areas, or transmitted through the atmosphere into
isolated regions, may adversely affect agriculture, visibility,
etc. Nonetheless, because urban areas account for the greatest
population exposed to NAAQS violations, control of these
emissions is most important from a public health perspective.
Hence, evaluating diesel particulate control strategies on an
urban basis is desirable.
As estimated in Chapter 2, the five diesel vehicle
subgroups accumulate different fractions of their annual VMT in
urban areas: LDDVs, 59.4 percent; LDDTs, MDVs, and LHDVs, 48.8
percent; and HHDVs, 26.9 percent. Urban cost-effectiveness
values taking these fractions into account are also shown in
Table 9-3 with averaging for all classes. A comparison of
these values shows all five figures to be much more similar
than before; however, the control of HDDVs still appears to be
more cost effective than that of LDDVs and LDDTs.
These urban cost-effectiveness values have been developed
only for comparison among the five diesel subgroups. The
nationwide cost-effectiveness values of Table 9-3 will be used
in comparisons with stationary source controls for two
reasons. First, urban cost-effectiveness values are not
available for stationary sources. Second, the use of urban
values for only mobile sources would artifically make the cost
effectiveness of diesel particulate controls appear worse
relative to that of stationary sources controls.
Ill. Cost Effectiveness of Controlling Particulate Emissions
from Selected Stationary Sources
A. Introduction
One means of qauging the appropriateness of controlling
diesel particulate emissions is to compare the cost
effectiveness of diesel particulate control against the cost
effectiveness of controlling particulate emissions from
stationary sources. This section of the analysis will be
devoted to developing cost-effectiveness values for stationary
sources. The following section will then develop a methodology
for converting the cost-effectiveness values derived both here
and in the previous section into values which are comparable on
an air qualtiy basis. These latter values will be used in the
comparison of mobile and stationary source controls.
-------
9-11
A total of eight stationary sources have been selected for
study, based on the availability of control cost information
and emission reductions on a total, inhalable, and fine
particulate basis. These eight sources are listed below:
Source
Borax Fusing Furnace
Wet Cement Kiln
Medium-Sized Industrial Boiler
Electric Utility Coal-Fired
Generator
Kraft Recovery Furnace
Kraft Smelt Tank
Rotary Lime Kiln
Electric Arc Furnace (steel)
Particulate Control System
Venturi Scrubber
Electrostatic Precipitator
Baghouse
Electrostatic Precipitator
Electrostatic Precipitator
Venturi Scrubber
Electrostatic Precipitator
and Baghouse
Baghouse
Two sets of data and, therefore, two different approaches
will be used in this analysis. Costs and emission reductions
for the first two sources listed above will be developed here
from data contained in a recently published EPA report on
control techniques for stationary source particulate emissions
(herein after referred to as the Control Techniques
document).[7] Cost-effectiveness values for the last six
sources listed above have already been developed in a previous
EPA analysis.[8] These will be used directly here, with some
adjustments to the costs due to inflation, and, where data
permits, some adjustment to the amount of the inhalable
particulate benefits due to a change in the assumed maximum
diameter for inhalable particulate from 15 to 10 micrometers.
The particle size distributions, source and emission
control systems characteristics, and costs used in this
analysis are based on the best available data and are
representative, of the sources being considered. However, it is
important to note that all of the values used would likely vary
from source to source within each source category, so this data
and the analysis which follows cannot be routinely applied to
every individual source. Stationary source emission control
systems are not standardized, but are designed to meet the
needs of each.user. However, even with these qualifiers, the
cost-effectiveness values developed here will serve as a valid
basis of comparison with the cost-effectiveness of diesel
particulate control.
-------
9-12
B.. Cost Effectiveness of Controlling a Borax Fusing
Furnace and a Wet Cement Kiln
1. Costs of Control
Given the necessary information on source and emission
control system characteristics, Volume 1 of the Control
Techniques document mentioned above contains a number of
correlations which can be used to estimate the annualized costs
of particulate emission control systems. These annualized
costs include both capital, direct and indirect operating
costs', and have been developed from data presented in a more
detailed EPA report.[9]
The annualized costs given in the Control Techniques
document cover 8,700 hours per year of operation, or
essentially continuous use. This is probably unrealistic since
a normal downtime for scheduled and unscheduled maintenance of
approximately 10 percent would- be expected. Using 8,700 hours
per year without downtime will tend to improve cost
effectiveness, since fixed costs remain during downtime but the
emission reduction is completely lost. However, since no
accurate estimates of downtime experienced by the various
stationary sources are available, no adjustment will be made
here. (Assuming continuous operation happens to also be
consistent with the manner in which the cost-effectiveness
values were calculated in the draft HDD particulate requlatorv
analysis, which are addressed in Section C.)
The Control Techniques document presents costs in January
1980 dollars. Updating them to 1983 dollars using the producer
price index for all industrial commodities[10] leads to an
annualized cost increase of about 32 percent.
Table 9-4 presents the annualized costs for the borax
fusing furnace, the wet cement kiln, and the values of the
particulate control system parameters used to estimate these
costs from the previously mentioned figures. In some cases,
the values for these parameters were taken from the Control
Techniques document. In other cases, the values were based on
emissions data in EPA's Office of Air Ouality Planning and
Standards.[11]
2. Emission Reductions
As was done for diesels, emission reductions for
stationary sources will be developed on a total, inhalable, and
fine particulate basis. Table 9-5 presents size-specific
emissions data for the uncontrolled and controlled cases for
each source. The first column shows particulate concentration
-------
9-13
Table 9-4
Parameter Values and Annualized Control Costs
-for Selected Stationary Source Particulate Controls
(1983 dollars)
Control Control System Exhaust Gas Annualized
Source System Parameters Rate (Am^/sec) Cost
Borax Furnace Scrubber Delta = 11 kPa 38 $1,170,000
Wet Cement Kiln ESP SCA =120 m2/(m3/sec) 130 $1,320,000
-------
Table 9-5
Qnissions Data for Borax Fusing
Furnace and Wet Cement Kiln
Particulate Size Basis
¦flotal
Inhalable
Fine
Mass
Concentration
(mg/ONCM)
Annual
Emissions
(metric tons)
Mass
Concentration
(mq/DNCM)
Annual
Emissions
(metric tons)
Mass
Concentration
(mq/DNCM)
Annual
Emissions
(metric tons)
Borax Fusing Furnace
Uncontrolled 784 786
Controlled 24.3 24
Reduction — 762
Wet Cement Kiln
Uncontrolled 2.02 x 10? 3.29 x 10?
Controlled 67.4 110
Reduction — 3.29 x 10?
596 598 531 532
20.6 20 19 20
578 — 512
14,800 24,000 6,000 9,770
109 109 63.1 103
23,991 — 9,667
-------
9-15
in terms of milligrams per dry nominal cubic meter (mq/DNCM) of
exhaust gas. The annual emission levels were determined by
multiplying the mass concentrations by the exhaust gas flow
rates expressed in dry nominal cubic meters. These exhaust gas
flow rates were estimated to be 32 DNCM/sec for the borax
fusing furnace and 52 DNCM/sec for the wet cement' kiln using
the actual exhaust gas flow rates from Table 9-4 and the
appropriate adjustment factors for temperature, pressure, and
moisture content.
Mow, given the exhaust gas flow rate in DNCM/sec, size
specific mass concentration in mg/DNCM before and after
control, and an annual operation period of 8,700 hours per
year, the annual metric tons of particulate emissions and
reductions by particle size can be calculated. Table 9-5 shows
these annual emission rates on a particle size basis before and
after control for both the borax fusing furnace and wet cement
kiln, assuming a constant reduction efficiency with time.
Subtracting emission rates before and after control gives the
emission reduction.
Given the annualized cost values in Table 9-4 and the
annual emission reduction in Table 9-5, cost-effectiveness
values on a total, inhalable, and fine particulate basis can be
determined. These are shown in Table 9-6.
C. Update of Previously Developed Cost-Effectiveness
Values
In previous analyses, EPA developed cost-effectiveness
values for a number of different stationary sources and
particle sizes. [8] . These values ..require two adjustments before
being used in this analysis. First, costs must be updated from
1980 to 1983 dollars. This can be accomplished using the 32
percent change in the producer price index for all industrial
commodities which was also used above.
Second, the inhalable particulate emission reductions-
estimated previously also require some adjustment due to a
change in the assumed cutoff diameter from 15 micrometers in
the 1980 analysis to 10 micrometers in the present analysis.
This reduction in emission benefits will in turn lead to an
increase in the relative cost effectiveness on an inhalable
particulate basis.
After reviewing the sources for the original estimates and
other data developed since that time, entirely new estimates
for the mass percent of inhalable particulates have been
developed for the electric utility and the electric arc
furnace. The inhalable fraction of electric utility
-------
9-16
Table 9-6
Cost Effectiveness for Stationary Sources[l,2]
(1983 Dollars per metric ton)
Particulate Size Basis
Source
Total
Inhalable
F ine
Wet Cement Kiln
[8]
55
136
Kraft Smelt Tank
250
299
455
Electric Arc Furnace[3]
924
1,440
1,452
Electric Utility[4].
1,254
1,805
4,092
Industrial Boiler[51
1,320
1,848
5,544
Rotary Lime Kiln (ESP)[6]
1,584
1,980
3 ,168
Borax Fusing Furance
1,532
2,021
2,281
Rotary Lime Kiln (Baghouse)[6]
1,716
2,112
3,300
Kraft Recovery Furnace[7]
1,678
2,145
3 ,055
[1] Ranked according to Inhalable Particulate Cost
Effectiveness.
[2] For simplification, the midpoint of the ranges were used
where applicable.
[3] Direct evacuation with 90 percent efficient canopy hood
versus direct evacuation with open roof.
[4] High efficiency ESP (0.03 lb/10® BTU) versus lower
efficiency ESP (0.1 lb/10*> BTU) .
[5] Baghouse (0.03 lb/10® BTU) versus cyclone (0.3 lb/106
BTU) .
[6] High efficiency ESP (0.6 lb/ton limestone) versus lower
efficiency ESP (0.6 lb/ton limestone) for 500 TPD plant;
baghouse (0.3 lb/ton) versus lower efficiency ESP for 125
TPD plant.
[7] High efficiency ESP (99.5 percent) versus lower efficiency
ESP (99.0 percent).
[8] Less than $1 per metric ton.
-------
9-17
particulate was decreased from the 90-100 percent range to 66
percent based on discussions with OAQPS staff.f11] Electric
arc furnace inhalable particulate fraction data was adjusted
from 90 to 66 percent based on data in the Control Techniques
document. In the other cases, no data were available to make
any adjustments, so it was assumed that all of the particulate
controlled at 15 micrometers or less were also all iess than 10
micrometers. This may overestimate the amount of inhalable
particulate controlled and, thus, improve inhalable particulate
cost-effectiveness. However, given the absence of data to the
contrary, this is the best estimate that can be made at this
time.
After adjustments for inflation and the change in
inhalable particle diameter, Table 9-6 gives the final
estimates of the cost effectiveness on a total, inhalable, and
fine particulate basis for the six stationary sources
previously analyzed and the two sources addressed in Section
B. They are listed in order of their inhalable particulate
cost effectiveness, from best to worst. Also shown is some
information on the control strategy on which the costs and
emission reduction benefits are based for the previously
analyzed sources.
IV. Discounted Cost Effectiveness for Mobile and Stationary
Particulate Sources
A. Introduction
As discussed previously, it is desirable to compare
emission sources based on their relative air quality impacts.
Ideally, such an evaluation would account for the complex array
of spatial and temporal characteristics associated with each
emission source. Such an elaborate study is beyond the scope
of this report, however. Instead, an attempt is made in this
analysis to account for the relative ground level impacts of
the various sources of particulate by evaluating dispersion
characteristics. Emphasis is placed on ground level
concentrations because the majority of the adverse effects from
air pollution in populated areas violating the NAAQS for
particulate matter occur due to ground level exposures (e.g.,
adverse effects on public health). Also, this is an important
determinant of air pollution since compliance with the NAAQS is
found by measuring ambient concentrations near . ground level.
Furthermore, this type of comparative evaluation has
historically been used by EPA to model the relative
contribution of various sources to ground level ambient
concentrations of particular pollutants. (More will be said
about these last two points later.)
-------
9-18
Although such an evaluation of relative air quality
provides a reasonable framework for comparing sources, it is
nevertheless limited in its scope. For example, performing the
analysis in this way ignores the location of these ground level
concentrations associated with each source, particularly with
respect to the number of people exposed and the local need for
control (i.e., is the area in or out of compliance with the
NAAQS). Unfortunately, this is a significant limitation since,
for example, stationary sources can often be controlled on an
individual basis (i.e., where the air quality problems are),
while mobile sources cannot. This effect results in a relative
inefficiency of the mobile source approach which cannot be
factored in at this time. Thus, the conclusion of this
cost-effectiveness comparison cannot be conclusive.
The comparison of cost effectiveness on an air qualtiy
basis will be conducted in three steps. First, it will be
necessary to determine an expression which relates the effect
of various source characteristics on ground level particulate
concentrations resulting from a given emission rate. Second,
the pertinent source characteristics for the various sources
under consideration here and the resultant air quality discount
factors will also have to be determined. Third, once these
factors have been determined, it will be oossible to calculate
discounted cost-effectiveness values for all sources which can
then be compared with those for diesels.
A. Methodology for Evaluating the Ground Level Impact
o"? Stationary Source Particulate Emissions
There are many characteristics unique to each source which
can affect its relative contribution to ground level
particulate concentrations. The meteoroloqical conditions of
the area, particle size and density, release height, and others
can all affect dispersion. Given that 1) local meteorological
conditions cannot be taken into account in a study of this
breadth, and 2) this studv is primarily concerned with
particulate less than 10 microns in diameter (i.e., similar
particle-related dispersion), the primary remaining factor
affecting dispersion is release height.
In a recently released EPA document, an expression has
been developed which provides a reasonable approximation of the
dependence of the maximum ground level particulate
concentration on effective release height.[12] This
relationship is provided below:
W = 10/H for H greater than 10 meters;
w =» 1 for H less than or equal to 10 meters.
-------
9-19
Where:
W = discount factor, maximum ground level particulate
concentration relative to a ground level source,
H =» effective release height, in meters (m) .
This relationship is being used by OAQPS in their
reconsideration of the NAAQS for particulate matter to relate
the impact of various emission source controls on ambient
particulate levels, which are measured near ground level, and
compliance with the NAAQS. The general concept is also
analogous to the use of source discount factors in rollback air
quality modelling.
As would be expected, this equation showns an inverse
relationship between maximum ground level contribution and
effective release height; i.e., as release height increases,
the maximum contribution -from this source decreases.
B. Effective Release Heights and Discount Factors for
Both Mobile and Stationary Sources
The effective release height for any emission source is
equal to the sum of the physical stack height and the vertical
height which the plume rises before significant horizontal
dispersion occurs. While stack height is easily measured and
fixed over time, plume rise varies according to source
characteristics and meteorological conditions (e.g., stack gas
temperature, exhaust gas flow rate, atmospheric stability, air
temperature, wind velocity).
It is intuitively clear that the effective release height
for diesel vehicles is less than 10 meters, and when evaluated
in the equation above, yields the conclusion that diesel
vehicles can be considered a ground level source (discount
factor equal to 1.0). However, for stationary sources this may
not be the case, and effective release height calculations are
necessary.
A number of different models to calculate plume rise under
various atmospheric stability conditions have been developed
over the past 35 years. One approach which has gained
widespread acceptance was developed by Briggs and will be used
here to estimate the plume rise for the eiaht stationary
sources under consideration.[121 As a further simplification,
the Briggs formulae for a stable/near neutral atmosphere will
be used in preference to those for an unstable atmosphere. It
should be noted that this will tend to improve cost
effectiveness (low cost-effectiveness values) of stationary
-------
9-20
source particulate controls, since particulate dispersion is
siqnificantly increased during increased atmospheric
instability relative to that for neutral to stable atmospheres
and the resulting ground-level impacts would be lowered.
The Briggs formulae (shown in Figure 9-1) require
information on both source and atmospheric characteristics.
Source characteristic values needed include the exhaust gas
exit temperature and exhaust gas volumetric flow rate. These
are shown in Table- 9-7 along with their sources. Atmospheric
conditions needed include the ambient air temperature, wind
velocity, and atmospheric vertical temperature gradient at the
stack exit. The choice to use an atmosphere with stable to
near neutral characteristics will dictate values for these
conditions. The values used here are -2°C/305 m for the
ambient air temperature lapse rate, 288°K for the ambient air
temperature at the stack exit, and 5 m/sec for the wind speed
at the stack exit. These are fairly typical values for a
midwestern U.S. city under stable to near neutral conditions,
based on the ICAO U.S. standard atmosphere. The resultant
plume rise heights are also shown in Table 9-7.
The effective release height is the sum of the stack
height and the plume rise. Typical stack heights for the
sources/control systems under consideration are given in Table
9-7. When these terms are added for the sources under
consideration here, the effective release heights shown in
Table 9-7 result. Using these effective release heights and
the relationship given in the equation above, Table 9-7 qives
the values of the weighting factor for the sources/control
systems under construction here. Mote that for diesel vehicles
the weighting factor is 1.0 since the effective release height
is less than 10 meters.
C. Air Quality Discounted Cost-Effectiveness Values
All that remains to be done to estimate cost effeciveness
on an air quality basis is to divide the cost effectiveness
values of Table 9-6 by the discount factors of Table 9-7.
These discounted cost effectiveness values are shown in Table
9-8.
The figures in Table 9-8 show that after consideration of
relative air quality effects, the base scenario is quite cost
effective relative to stationary source controls regardless of
the size of particulate examined. while the control of wet
cement kilns is more cost effective than diesel particulate
control across the board, only one other source is
significantly more cost effective on a TSP basis (industrial
boilers) . No other sources are more cost effective on a fine
-------
1. h = 2.3
9-21
Figure 1
Plume Rise Calculation Equations
* 1/3
Us
2. „ q 0 (Ts - Ta)
Ta
3. c; - _2_ dT 3C°
Ta
-------
Table 9-7
Source Characteristic Parameters, Plume Rise,
Effective Helease Height, and Weighting Factor
Source/Reference
Control
System
Flow
Rate
Q(Am3/s)
Stack
Temp(°K)
Plume
Rise (m)
Stack
Height(m)
Effective
Release
Heiqht(m)
Discoi
Factor
Borax Furnace[5,9]
Scrubber
38
353
83
12
95
.105
Cement Kiln[5,9]
ESP
30
433
101
46
147
.068
Electric Utility(5J
ESP
533
400
242
175
417
.024
Industrial Boiler[5]
Baghouse
163
470
191
55
246
.041
Electric Arc Rirnace(14]
Baghouse
62
346
95
19
114
.088
Rotary Lime Kiln[15]
ESP
3,000
474
509
30
539
.019
Baghouse
800
405
281
25
306
.033
Kraft Furnace[16]
ESP
76
430
136
75
211
.047
Kraft Staelt Tank[16]
Scrubber
7,000
351
470
53
523
.019
<£>
I
ro
N)
-------
9-23
Table 9-8
Summary
Air Quality Discounted Cost Effectiveness
Diesel Vehicles and Stationary Sources
($ per metric ton)*
Particulate Size Basis
Source
Total
inhalable
Fine
Wet Cement Kiln
1
310
2,000
HHDV**
2/850
2,850
2,850
LHDV**
5,420
5,420
5,420
MDV**
9,810
9,810
9,810
LDDT**
13,400
13,400
13,400
LDDV**
13,900
13,900
13,900
Kraft Smelt Tank
13,200
15,700
23,900
Electric Arc Furnace
10,500
16,400
16,500
Borax Fusinq Furance
14,600
19,250
21,700
Industrial Boiler
32,200
45,100
135,000
Kraft Recovery Furnace
35,700
45,600
65,000
Lime Kiln (Baghouse)
52,000
64,000
100,000
Electric Utility
52,250
75,200
170,500
Lime Kiln (ESP)
83,400
104,000
167,000
* 1983 dollars.
Ranked according to
inhalable particulate cost
effectiveness.
Cost Effectiveness
(Table 9-6) divided
by Discount
Factor
(Table 9-7) .
** Assumes presence of
emissions averaging
«
-------
9-24
or inhalable particulate basis. (As mentioned earlier, the
control of both fine and inhalable particulate are most
important with respect to protecting the public health, the
control of fine particulate is most important with respect to
visibility, and the control of total particulate is most
important with respect to soiling.) However, because of the
limitations in the method used to determine the relative air
quality impact of the various sources, these judgments cannot
be made conclusively. At best, it can only be said that there
is no evidence that diesel particulate control is not cost
effective with respect to stationary source control.
To further place these figures in perspective, Table 9-9
shows estimates of annual emissions nationwide for most of the
source categories listed in Table 9-8. However, the two tables
do not match up exactly one-to-one. The emission estimates
apply to entire industrial categories, while in a few cases
(e.g., lime kilns and electric arc furnaces) the sources listed
in Table 9-1 represent only . a fraction of the industrial
cateqory emissions. Nonetheless, these emission estimates will
be sufficient for our purposes here.
The nationwide emission estimates of Table 9-9 can be used
to compare the potential for emission reduction from the
stationary sources to that available for diesels. As can be
seen, the base scenario will reduce nationwide emissions by
roughly 120,000 metric tons per year in 1995. Only three of
the stationary sources being considered here could potentially
provide the same emission reduction: electric utilities, the
cement industry, and industrial boilers. Given that the cement
industry is predominantly located in rural areas,[171 only the
remaining two sources can produce the same emission reduction
where it is most needed. In addition, the impact of these
sources on around-level ambient concentrations relative to that
of diesels must also be kept in mind.
VI. Summary
The cost effectiveness of the base scenario relative to
the relaxed scenario has been estimated for five classes of
diesels. For the purposes of comparing control between the
diesel vehicle classes, cost-effectiveness values were
determined on both a nationwide and urban basis, as well as for
the control of total, inhalable and fine particulate. The cost
effectiveness of controlling stationary source particulate
emissions was also estimated. In order to compare these varied
sources against the goal of improving air quality, emission
control effectiveness was discounted according to the effective
release height of the emission and its effect of dispersion.
While this methodology accounts for source-specific dispersion
-------
9-25
Table 9-9
Annual Nationwide Emission Rates by Source Category
Stationary Source (1981)[181
Electric Utilities
Cement Industry
Industrial Boilers
Concrete, Lime, Gypsum Industry
Pulp Mills
Iron and Steel Foundries
Borax Furnaces
- On-Highway Diesels
(best estimate sales)
Metric Tons Per Year
1,000,000
460,000
400,000
140,000
110,000
50,000
Unavailable
Metric Tons Per Year
1980
1995
Relaxed Scenario
Base Scenario
140,000
285,000
166,000
-------
9-26
effects, it does not account for important factors such as the
location of the air quality improvement. This is a significant
drawback, and prevents a fully appropriate comparison from
being made.
The results of the analysis indicate that on an air
quality basis the control of diesel particulate is cost
effective relative to stationary source controls reqardless of
whether fine, inhalable, or total particulate are considered.
However, due to the limitations of the methodology, the best
that can be said at this time is only that there is no evidence
that diesel particulate control is not cost effective with
respect to available stationary source control and that the
control of diesel particulate should not be avoided due to
cost-effectiveness concerns. Between the subgroups of diesel
vehicles, on an urban basis (the most appropriate) and assuming
the presence of averaging, HHDVs are the most cost effective to
control, followed by LHDVs, MDVs, LDDVs, and LDDTs.
-------
9-27
References
1. "Health, Soiling, and Visibility Benefits of
Alternative Mobile Source Diesel Particulate Standards," Final
Report, EPA Contract No. 68-01-6596, Mathtech, Inc.,. Princeton
NJ, December 1983.
2. "The Impact of Light-Duty Diesel Particulate
Standards on the Level of Diesel Penetration in the Light-Duty
Vehicle and Light-Duty Truck Markets," Jack Faucett Associates
EPA Contract No. 68-01-6375, November 30, 1982.
3. "The Highway Fuel Consumption Model: Eighth
Ouarterly Report," Energy and Environmental Analysis, Inc. for
U.S. DOE, Contract No. DE-AC01-79PE-70032, July 1982.
4. "Particulate Size Variation in Diesel Car Exhaust,"
Groblicki, P., and C. Begeman, SAE 790421.
5. "Characterization of Diesel Exhaust Particulate
Under Different Engine Load Conditions," Presented at 71st
Annual Meeting of APCA, Schreck, R., et.al., June 25-30, 1978.
6. "Characterization of Particulate and Gaseous
Emissions from Two Diesel Automobiles as Functions of Fuel and
Driving Cycle," Hare, C. and T. Baines, SAE Paper No. 790424.
7. "Control Techniques for Particulate Emissions from
Stationary Sources," Vols. 1 and 2, U.S. EPA, OANR, OAOPS,
EPA-450/3-81-005a and b, September 1982.
8. "Draft Regulatory Analysis, Heavy-Duty Diesel
Particulate Regulations," U.S. EPA, OANR, OMS, ECTD, SDSB,
December 23, 1980.
9. "Capital and Operating Costs of Selected Air
Pollution Control Systems," U.S. EPA, OANR, OAOPS,
EPA-450/5-80-002, December 1978.
10. Figures gathered by the Bureau of Labor Statistics
and compiled in the February 1983 "Economic Report of the
President."
11. Extracted from selected Fine Particulate Emissions
Inventory System data.
12. "Draft of Regulatory Impact Analysis for Proposed
Revision of National Ambient Air Quality Standard for
Particulate Matter,"
-------
9-28
References (cont'd)
13. Air Pollution, McGraw Hill Book Company, Perkins,
H., 1974.
14. "Background Information for Standards of
Performance: Electric Arc Furnaces in the Steel Industry, Vol.
1: Proposed Standards," U.S. EPA, OAWM, OAOPS,
EPA-450/2-74-017a, October 1974.
15. "Standards Support and Environmenal Impact
Statement, Vol. 1: Proposed Standards of Performance for Lime
Manufacturing Plants," U.S. EPA, OAWM, OAOPS,
EPA-450/2-77-007a, April 1977.
16. "Standards Support and Environmental Impact
Statement: Vol. 1: Proposed Standards of Performance for
Kraft Pulp Mills," U.S. EPA, OAWM, OAQPS, September 1976.
17. Information Concerning Particulate Emissions from
Non-Mobile Sources, Memo from R. Neligan to C. Grav, U.'S. EPA,
July 11, 1979.
18. "National Air Pollutant Emission Estimates,
1970-1981," U.S. EPA, OANR, OAQPS, EPA-450/4-82-012, September
1982.
-------
CHAPTER 10
¦SENSITIVITY
I. Introduction
This chapter contains a variety of analyses intended to
address the sensitivity of the previous technical analyses to
key assumptions that were made. The first analysis addresses
the assumed levels of the LDV and LDT NOx standards. While the
current NOx standard were presumed to continue indefinitely for
ease of analysis, this is actually not likely to be the case.
As additional NOx control tends to increase enqine-out
particulate levels, more stringent NOx standards would increase
emissions under the relaxed scenario and increase the number of
traps required under the base scenario. The cost effectiveness
of trao application would also be affected.
The second analysis has a two-fold purpose. One, it
addresses the assumption that the analysis of the base
scenario, which only requires a minority of LDDVs and LDDTs to
be equipped with traps, adequately addresses the economic
viability (cost and cost effectiveness) of trap-oxidizer usage
in general. Two, it expands the previous benefits analyses by
estimating emissions (and, thus, other environmental effects)
under the stringent particulate control scenario.
An intermediate control scenario for LDDVs and LDDTs is
examined in the third analysis. This scenario, requiring the
application of advanced non-trap technology, falls between the
relaxed and the base scenarios in terms of stringency.
The fourth analysis addresses the possibility of using HDD
emissions under the relaxed scenario as an estimate of
uncontrolled emissions, which is usually desirable to present
in a regulatory analysis.
The fifth analysis assesses the effect on diesel
particulate emissions resulting from having no growth in future
diesel sales. This provides a lower bound on the emission
estimates which have been analyzed in the previous chapters.
The first two analvses will be presented together, as they
overlap technically to a significant degree. The third,
fourth, and fifth analyses will follow. It should be noted
that these analyses wili only address certain basic features of
each scenario, such as fleet emissions, trap usage and cost
effectiveness. More advanced aspects, such as exposure, cancer
risk, and economic impact, are not presented. This was done
because all of the benefits described in this study are
-------
10-2
proportional to fleet-wide emissions in a given calendar year,
except for visibility effects, which are nearly proportional in
the ranqe being examined. Thus, the sensitivity of urban
emissions in the sensitivity analyses indicates the same
sensitivity in any other benefit category. A quantitative
estimate of any or all benefits under one of the new scenarios
being analyzed here can be determined simply by applying the
ratio of fleetwide urban emissions to the estimate of benefits
under one of the scenarios analyzed in the previous chapters.
The same is true for economic impact, which is essentially
proportional to the fraction of vehicles with traps.
II. Light-Duty NOx Standards and the Stringent Control Scenario
The previous chapters assumed that the NOx standard for
LDVs and LDTs would remain at 1.5 and 2.3 g/mi, respectively,
throughout the time period covered by this study. In this
section, three additional sets of LDV/LDT NOx standards are
investigated: 1) 1.0/1.2 g/mi, 2) 1.5/1.7 g/mi, and 3)
2.0/2.3 g/mi.
In addition, the previous chapters only addressed two
control scenarios, the relaxed and the base scenarios. Here, a
third scenario, the stringent scenario, will be examined. It
consists of full, trap-based standards of 0.08 g/mi for LDDVs,
0.10 g/mi for LDDTs, and 0.10 g/BHP-hr for HDDs. The LDDV
standard of 0.08 g/mi is that promulgated by California for the
1989 model year. The LDDT and HDD standards follow from this
level in that they require the same percentage reduction from
the base scenario.
Four key aspects of these scenarios will be addressed.
The first aspect addressed will be manufacturers' corporate
average particulate standard levels associated with the relaxed
scenario under the three sets of NOx standards. The second and
third aspects are directly related, the fraction of vehicles
requiring traps under the base and strinaent scenario, and
urban particulate emissions in 1995 under the relaxed, base,
and stringent scenarios under the various NOx standards. The"
fourth aspect will be the cost effectiveness of the base and
stringent scenarios under the various NOx standards.
A. Manufacturers' Corporate Average Standard Level
The methodoloqv used to estimate each manufacturer's
current (relaxed scenario) corporate average standard level
under NOx standards of 1.5 and 2.3 g/mi for LDVs and LDTs,
respectively, was presented in Chapter 1. There, each engine
configuration's low mileaae particulate emission level was
first adjusted for the NOx emission level under consideration.
-------
10-3
This was accomplished through the use of estimated
NOx/particulate tradeoff curves. The slope of the curve for
small LDDV engines (1.6-1.8 liters displacement) was -0.033 for
NOx values less than or equal to 1.35 g/mi and zero for NOx
values qreater than 1.35 g/mi. For medium LDDV engines (2.0 to
2.8 liters displacement), the slope of the curve was -0.20 for
NOx values less than or equal to 1.35 q/mi and -0". 10 for NOx
values greater than 1.35 g/mi. For larqe LDDV engines, the
slopes were -0.40 and -0.10 for NOx values less than and
greater than 1.35 g/mi, respectively. The slopes of the
NOx/particulate tradeoff curves were the same for LDDTs.
However, small LDDTs have displacements from 1.6 to 2.3 liters
and full-size LDDTs have displacements of 6.2 liters. There
were no "medium" LDDTs.
Once each engine configuration's low-mileage particulate
emission level was estimated, its particulate standard level
was determined bv multiplying the particulate emission level by
its deterioration factor and the safety factor. Each
manufacturer's engine configurations were then sales-weighted
to give that manufacturer's corporate average standard level.
This methodology was repeated here for more stringent NOx
standards (1.0/1.2 a/mi for LDVs and LDTs, respectively) and
also for more relaxed NOx standards (2.0/2.3 g/mi LDVs/LDTs).
Tables 10-1 and 10-2 show each manufacturer's corporate average
particulate standard levels associate with the relaxed scenario
for LDDVs and LDDTs under the various NOx standards. For
LDDVs, going to a 1.0 g/mi NOx standard from a 1.5 g/mi NOx
standard increases particulate emissions more than twice as
much as going from a 2.0 g/mi NOx standard to a 1.5 g/mi NOx
standard. The effect of moving to a 1.2 g/mi from a 1.7 g/mi
NOx standard for LDDTs is small for small LDDTs but is dramatic
for full-size LDDTs. The impact of moving from a 2.3 g/mi to a
1.7 g/mi NOx standard is negligible for small LDDTs but is
measurable (18 percent increase) for full-size LDDTS. These
impacts will reappear below when the effects of various NOx
standards on urban emissions under the relaxed scenario are
considered later in this section.
In applying this methodology to the stringent NOx
standards (1.0 g/mi for LDVs and 1.2 g/mi for LDTs), the
estimated NOx/particulate tradeoff curves were based on 1983
certification data, most of which were at higher NOx levels,
and extrapolated to obtain these low NOx levels. There are
currently California 1984 certification level data available
for some but not all of the nationally certified engine
families and an evaluation of the accuracv of the estimated
values may be made on an engine family basis.[1] The
estimation overestimated the particulate standard levels at low
-------
10-4
Table 10-1
Relaxed Scenario
Corporate Average Particulate
Standard Levels for LDDVs
(grams per mile)
1.0 g/mi 1.5 g.mi ¦ 2.0 g/mi
Manufacturer NOx Standard NOx Standard NOx Standard
General Motors .50 .29 -.25 -
Volkswagon .21 .20 .20
Nissan .29 .26 .25
Mercedes-Benz .60 .42 .34
isuzu .22 .20 .20
Audi .26 .20 .18
Peugeot .36 1 .26 .21
Volvo .41 .29 .24
Sales-Weighted .42 .27 .24
Industry Wide
Average
-------
10-5
Table 10-2
Relaxed Scenario
Corporate Average Particulate
Standard Levels for LDDTs
(grams per mile)
1.2 g/mi 1.7 g/mi 2.3 g/mi
Manufacturer NOx Standard Nox Standard 'Nox Standard
Small LDDTS:
Ford .30 .29 .29
Isuzu .33 .25 .25
Nissan .37 .35 .35
Mitsubishi .43 .39 .39
Toyota .20 .19 .19
Volkswaqon .32 .31 .31
Toyo Kogyo .30 .29 .29
Full-Size LDDTs:
General Motors ,56 .34 .28
Sales-Weighted, .52 .33 .28
Industry-wide
Average
-------
10-6
NOx standards for both LDDVs and LDDTs for the majority of the
engine families that were certified under California's 1984 1.0
g/mi/1.2 g/mi NOx standards, by an average of approximately 15
percent. Thus, the corporate average particulate standard
levels for the low NOx standards should be considered as uDper
limits, as can the resulting number of vehicles projected to
require traps under this scenario, as discussed in the
following section.
B. Percent of Trap-Squioped vehicles ... -
The methodology for calculating the percentage of each
model year's LDDVs and LDDTs to be equipped with trap-oxidizing
systems was also presented in Chapter 1. Basically, the number
of vehicle grams per mile (veh-g/mi) of diesel particulate
allocated to each manufacturer under the base scenario (i.e.,
particulate "averaging" standards of 0.20 and 0.26 g/mi for
LDDVs and LDDTs respectively) was determined from
manufacturer's projected 1985 sales. Then, the number of
veh-g/mi of diesel particulate that would actually be emitted
by each engine configuration under NOx standards of 1.5 and 2.3
g/mi for LDVs and LDTs, respectively, without traps were
calculated. Finally, traps were applied to reduce each
manufacturer's diesel particulate veh-g/mi to the allowable
level which gave the percentage of each manufacturer's
production that would need to be equipped with traps.
Tables 10-3 and 10-4 show the percentage of each
manufacturer's LDDV and LDDT production (and that of the
overall fleet) that would need to be equipped with traps under
the base and stringent scenarios for the three sets of NOx
standards. Under a 1.0 g/mi LDV NOx standard, the percentage
of the LDDV fleet'which would require traps under the base
scenario would more than double from that required under a 1.5
g/mi NOx standard. Conversely, a 2.0 g/mi NOx standard would
reduce the requirement for traps by almost half. The stringent
scenario would require the LDDV fleet to be trap-equipped as
follows: 1) nearly all under a 1.0 g/mi NOx standard (95
percent); 2) 82 percent under a 1.5 g/mi NOx standard; and 3).
72 percent under a 2.0 g/mi NOx standard. The trap fractions
for LDDTs follow verv closely those for LDDVs.
As explained in Chapter 1, 100 percent of HDDs are
equipped with traps under the base scenario without averaging.
With averaging the percentage of traps would drop to about 70
percent. Under the stringent scenario, essentially all HDDs
are equipped with traps, with or without averaging.
-------
10-7
Table 10-3
Percentage of LDDVs Requiring Traps Under
Various NOx and Particulate Standards, (q/mi)
Str ingent
Part., 0.08
Base
Part.,
0.20
Manufacturer
• 1.0
NOx
1.5
NOx
2.0
NOx
1.0
NOx
1.5
• NOx
2.0
NOx
General Motors
100
81
73
61
27
15
Volkswagen
83
78
67
6
0
0
Nissan
89
88
75
33
26
23
Mercedes-Benz
100
96
79
80
55
45
Isuzu
82
77
67
9
0
0
Audi
84
77
62
28
2
0
Peugeot
96
87
64
55
30
5
Volvo
100
93
71
58
34
16
Sales-Weighted
Industry-wide
Percentage
95
82
72
48
22
14
-------
10-8
Table 10-4
' Percentage of LDDTs Requiring Traps Under
Various NOx and Particulate Standards, (q/mi)
Stringent
Part., 0
.10
Base
Part.,
0 .26
Manufacturer
1.2
NOx
1.7
NOx
2.3
NOx
1.2
NOx
1.7
NOx
2.3
NOx
General Motors
98
85
77
63
26
7
Volkswagen
79
78
78
14
15
15
Nissan
89
87
87
37
32
32
Isuzu
85
74
74
26
0
0
Ford
82
80
80
16
12
12
Mitsubish i
92
89
89
47
40
40
Toyota
55
55
55
0
0
0
Toyo Koqyo
si
80
80
15
11
11
Sales-Weighted
Industry-wide
95
"83
77
56
24
8
Percentage
-------
10-9
C. 1995 Urban Diesel Particulate Emissions rjnder
Various NOx Standard's
Having calculated industry-wide particulate standard
levels and percentages of traps required under each scenario,
the 1995 particulate emission factors for LDDVs and LDDTs can
be calculated. As explained in Chapter 2, the 1995 particulate
emission factors for LDDVs or LDDTs of a specific model year
are calculated using the age distribution of the in-use fleet,
the percentage of that model year's fleet equipped with traps,
the average non-trap emission level of those vehicles which are
equipped with traps, the particulate standard, and the annual
trap-failure rate (i.e., 1.5 percent per year).
The particulate emission factors for 1961-86 model year
LDDVs and LDDTs remain the same as those in Chapter 2, due to
the fact that all regulatory changes are assumed to occur in
1987. For the relaxed scenario, the emission factors for model
year 1987-95 are the sales-weighted industry-wide averages
shown in Tables 10-1 and 10-2. For the base and stringent
scenarios, the 1987-95 emission factors are essentialy the same
for all NOx standards since the presence of a standard
requiring control sets the emission level regardless of the
starting point. However, these particulate emission factors
are slightly different for each NOx standard, because both the
fleet-wide trap fraction and the average non-trap particulate
emission levels of those vehicles with traps change as the
applicable NOx standard changes. When a trap-oxidizer system
fails, the particulate emission level that the vehicle reverts
to is different under each NOx standard because of ' the
previously described NOx/particulate tradeoff. For vehicles
with properly operating traps, the emission factors are the
same.
These 1995 particulate emission factors were combined with
the vehicle miles traveled (VMT) breakdown by model year and
the diesel sales fractions (for both best estimate and worst
case sales) to yield weighted fleet-wide particulate emission
factors for each set of NOx standards. Again, this methodology
is fully described in Chapter 2. To obtain 1995 urban diesel
particulate emissions, the weighted particulate emission
factors were multiplied by the total 1995 VMT for each vehicle
class and by the urban fraction of VMT for each vehicle class
(i.e., 0.594 and 0.488 for LDVs and LDTs, respectively).
Table 10-5 presents the 1995 urban diesel particulate
emissions for best estimate and worst case diesel sales under
the relaxed and base control scenarios and combinations of the
various NOx standards. Table 10-6 shows the relative
contribution of each vehicle type to the totals of Table 10-5.
-------
10-10
Table 10-5
Vehicle
Type
Lncv
LDDT
Total*
LDDV
ldctt
Total*
1995 Urban Diesel Particulate Emissions
Under Various NOx Standards (metric tons)
LEV NOx = 1.0 g/mi
LPT NOx = 1.2 q/mi
Relaxed Base
Scenario Scenario
36,800
21,800
135,600
84,000
33,900
19,700
11,700
72,200'
43,800
18,000
205,900 108,000
LEV NOx =1.5 g/mi LEV NOx =
LPT NOx =1.7 q/mi LOT NOx =
Relaxed Base Relaxed
Scenar io Scenario Scenario
Best Estimate Diesel Sales
1.5 g/mi
2.3 q/mi
24,600
14,100
115,700
19,100
11,500
71,400
24,600
12,200
113,800
Wbrst Case Diesel Sales
55,300 42,400 55,300
21,800 17,600 18,800
165,100 106,200 162,000
Base
Scenario
19,100
11,500
71,400
42,400
17,600
106,100
I
LEV NOx = 2.0 g/m
LOT NOx a 2.3 g/mi
Relaxed Base ¦
Scenario ScenariJ
22,200
12,200
111,400
49,600
18,800
19,000
11,500
71,300
42,200
17,600
156,400 105,900
Totals include MEV/LHEV and HHDEV emissions of 9,400 and 67,600 (relaxed), and 4,70
and 36,100 (Base) for best estimate sales and 18,700 and 69,200 (relaxed) and 9
and 37,000 (Base) for worst case sales. These are r16t shown since they are the s,
regardless of LIT/ and LOT NOx standards.
,70fc
,io|
samP
-------
10-11
Table 10-6
Relative Contribution of 1995 Urban Diesel
Particulate Emissions Under Various NOx Standards (percent)
LEV NOx =
LOT NOx =
1.0 q/mi
1.2 q/mi
LEV NOx =
LOT NOx »
1.5 g/mi
1.7 q/mi
UJJ NOx =
LOT NOx =
1.5 g/mi
2.3 a/mi
UJJ NOX =
LOT NOx =»
2.0 q/mi
2.3 a/mi
Vehicle
Type
Relaxed
Scenar io
Base
Scenario
Relaxed
Scenario
Base
Scenario
Relaxed
Scenar io
Base
Scenario
Relaxed
Scenario
Base
Scenario
Best Estimate Diesel Sales
LDDV
27
27
21
27
21
27
20
26
ldctt
16
16
12
16
11
16
11
16
MEV/LHEV
7
7
8
6
8
6
8
7
HHDV
50
50
59
51
60
51
61
51
Total*
100 • .
100
100
100
100
100
100
100
Worst Case Diesel Sales
UXJJ
40
40
33
40
34
40
31
40
LDDT
16
17
13
16
12
16
12
16
MCV/LHEW
10
9
12
9
11
9
. .12 - -
9
HMDV
34
34
42
35
43
35
45
35
Total*
100
100
100
100
100
100
100
100
-------
10-12
The results shown in Table 10-5 indicate that 1995 urban
diesel particulate emissions under the relaxed scenario do not
change substantially from those evaluated in Chapter 2 (i.e.,
1.5/2.3 g/mi NOx standards) except for the most stringent
1.0/1.2 g/mi NOx standards. For the 1.0 g/mi NOx standard,
LDDV emissions increase by 50 percent as compared to a 1.5 g/mi
NOx standard. For the 1.2 g/mi NOx standard, LDDT " emissions
increase by 79 percent as compared to a 2.3 g/mi NOx standard.
Total 1995 urban diesel particulate emissions increase by 19
oercent under the 1.0/1.2 g/mi set of NOx standards as compared
:o the 1.5/2.3 g/mi set.
Under the base scenario, the changes with NOx standards
are less significant. The 1995 LDDV urban diesel particulate
emissions increase only 3 percent under a 1.0 g/mi NOx standard
as compared to a 1.5 g/mi NOx standard. For the other changes
in the LDDV and LDDT NOx standards, the situation is similar,
with very little change in emissions occurring.
The results of Table 10-6 are similar to Table 10-5 in
that the only NOx standards causing strong difference from the
main analysis are the 1.0/1.2 g/mi NOx standards under the
relaxed scenario. The contribution of LDDVs and LDDTs under
best sales estimate to total 1995 urban diesel particulate
emissions increases from 21 to 27 percent, and from 11 to 16
percent, resDectively, under the more stringent set of NOx
standards. The other vehicle types (i.e., MDV/LHDV and HHDV)
decrease their relative contribution with HHDV's share
decreasing the most (from 60 to 50 percent) . The results are
-similar for the-worst case diesel sales situation.
Under „ the Ustringent scenario, there- is little difference
among NOx standards (see Table 10-7). Overall, the breakdown
under the stringent scenario is between that under the relaxed
and base scenarios.
The decrease in urban emissions obtained under the
stringent scenario versus the relaxed scenario is between 56
and 72 percent for all vehicle types with the total decrease
being 65 percent. Compared to the base scenario, the stringent
scenario reduces total emissions by 43-46 percent, with the
change in each vehicle class being 37-54 percent.
Table 10-8 compares urban emissions under the three
control scenarios coupled with NOx standards of 1.0/1.2 g/mi to
previous diesel particulate studies. As can be seen,
projections for the base scenario are virtually the same as
that projected in 1979-80 for the same standards (controlled
scenario). However, even under the stringent NOx standards,
emissions under the current relaxed scenario are well below the
uncontrolled levels projected in previous analyses.
-------
10-13
Table 10-7
1995 Urban Diesel Particulate Emissions Under
the Stringent Scenario (metric tons)
1.0/1.2 1.5/1.7 2.0/2.3 Relative Con- Reduction From
Vehicle Type g/mi NQx g/mi NQx g/rni NOx tribution (%) Base (%)
Best Estimate Diesel Sales
LDDVs
10,700
10,000
9,500
24
48
LOOTS
5,900
5,600
5,400
13
53
MDCV/LHDCX/S
2,700
2,700
2,700
7
44
HHDDVS
22,600
22,600
22,600
56
38
Total
41,900
40,900
40,200 - -
100
43
Worst Case
Diesel Sales
LDCVs
22,500
20,900
19,700
36
51
LDDTs
8,900
8,500
8,100
14
54
MDCV/mDDVS
5,000
5,000
5,000
9
46
HHDCVS
23,100
23,100
23,100
41
37
Total.
59,500
57,500
55,900
100
46
-------
10-14
Table 10-8
Comparison of Current Urban Emission Estimates
Under Various NOx Standards* to Urban Emission
Estimates of Previous Studies __
1995 Urban Emissions Under LDV
and LDT NOx Standards of 1.0
Scenario and 1.2 a/mi (metric tons)
Best Estimate Diesel Sales
1979-80 Uncontrolled" - " - 239,000
Relaxed 137,000
Base 72,900
1979-80 Controlled 71,000
Stringent 42,300
Worst Case Diesel Sales
1979-80 Uncontrolled 287,000
Relaxed 207,300
Base 108,600
1979-80 Controlled 85,000
Stringent 59,900
The NOx standard scenarios of LDV = 1.5/LDT = 1.7, and LDV
= 2.0/LDT = 2.3 g/mi are not shown because all "relative
- -reductions" are less- than -4—percentage points different-
.than.Jthe. 1.5/2.3 g/mi case.. .. . v
-------
10-15
D. Cost Effectiveness
The cost effectiveness for LDDs and HDDs under the base
scenario was already determined in Chapter 9. Tables 9-1, 9-2,
and 9-3 of that chapter show the development of those
cost-effectiveness values.
In this study, cost effectiveness is the annualized cost
per vehicle divided by the annual emission reduction per
vehicle, both relative to the relaxed scenario and on a
fleet-average basis. The fleet-average annualized cost is a
straight-forward annualization of the fleet-average lifetime
costs using a 10 percent discount rate. The fleet-average,
lifetime costs are a function of the lifetime costs of
trap-equipped vehicles of various sizes, the trap-equipped
fraction of each vehicle size category, and the relative sales
of each vehicle size category. The lifetime trap-oxidizer
system costs for different size vehicles and the relative sales
of these vehicle sizes were described in Chapter 8. The
trap-equipped fractions of the LDDV and LDDT fleets under
various NOx standards were estimated in Section IIB of this
chapter.*
The determination of annual emission reductions was
explained in • Chapter 2. Basically, the annual emission
reduction per vehicle is approximately the reduction in the
vehicle's emission rate at half-life (compared to the relaxed
scenario) multiplied bv the lifetime-average annual VMT. The
effect of trap failures is included in the vehicular emission
rate.
Table 10-9 compares the"cost effectiveness of the various
-.m-LDD ,pa,r„t,ip.u,l,at.e . ...control . scenar ios.. - under---'--different • NOx- - »•
=-standards. Table" 10-1-0'-compares the cost effectiveness ~of th^-^31*^
various HDD particulate control scenarios. These tables
include the fleet-average annualized cost per vehicle, the
annual emission reductions per vehicle, and the urban cost
effectiveness (as described in Chapter 9). Table 10-9 also
shows the trap-equipped fraction for LDDs (assumed to be 100
percent for HDDs, except where averaging is applicable the
fraction is reduced to 70 percent).
It is assumed in this analysis that for LDDVs, large
vehicles are first equipped with traps, followed by medium
vehicles, and then small vehicles until the trap-equipped
fraction is met. Similarly, for LDDTs, full-sized LDDTs
are first equipped with traps, and then small LDDTs, until
the trap-equipped fraction is met.
-------
Table 10-9
LDtJJ and LDDT Cost-Effectiveness Values Uhder Various
Particulate Control Scenarios and NOx Standards ($/metric ton)
NQx=1.0/
1.2 g/mi
Base Scenario
NQx=1.5/
1.7 g/mi
N0x=2.0/
2.3 g/mi
Stringent Scenarioi;
N0x=1.0/ NOx=1.5/ ,NQx=2.0/
1.2 q/mi 1.7 q/mi 2.3 q/mi
cent Vehicles Equipped with Traps
DCVs
¦DOTS
48%
56%
22%
24%
14%
6%
95%
95%
82%
83%
72%
77%
¦et Average Annualized Cost Per Vehicle*
DWs
DOTS
$18.85
$20.77
$9.19
$8.83
$5.73
$2.81
$35.27
$34.56
$30.79
$31.24
$27.85
$28.34
ual Emission Reduction Per Vehicle (metric'tons)
**
DWS
DOTS
2.07 x 10~3 6.60 x 10-4 * 3.90 x 10-4
2.65 x 10~3 7.00 x 10~4 '2.10 x 10"4
3.15 x 10"3
4.10 x 10~3
1.77 x 10"3
2.20 x 10"3
1.54 x 10"3
1.77 x 10"3
t Effectiveness ($/metric ton)
DDVs
DCTs
$9,100
$7,800
$13,900
$12,600
$14,700
$13,400
$11,200
$8,400
$17,400
$14,200
$18,100
$16,000
an Cost Effectiveness ($/metric ton)
DCVs
DDTs
$15,400
$16,100
$23,400
$25,800
$24,700
$27,400
$18,900
$17,300
$29,300
$29,100
$30,800
$32,800
Based on estimated sales fractions of?29, 37, and 32 percent for large, medium, and,
small LDDVs, respectively; trap-oxidizer systems fitted to these vehicles! have an
average lifetime cost of $219, $234, and'$266, respectively. Small and full-sized LDDTs
are estimated at 34 and 66 percent o£ "sales respectively, with trap-oxidizers system
lifetime costs of $229 and $252, respectively.
Based on estimated annualized travel of 10,000 miles and 10,900 miles for LDCVs and
LDDTs, respectively; reductions are compared to relaxed scenario.
-------
10-17
Table 10-10
HDD Cost-Effectiveness Values
Under Various Control Scenarios ($/metric ton)
Base Scenario Stringent Scenario
Fleet-Average Annualized Cost Per Vehicle*
MDVs $ 84 •$ 84
LHDVs $132 $132
HHDVs $228 $228
Annual Emission Reduction Per Vehicle (metric tons)**
MDVs 0.00,60 - 0.0086
LHDVs 0.0171 0.0246
HHDVs 0.0560 0.0799
Cost Effectiveness ($/metric ton)
MDVs $14 ,000 $9,800
LHDVs $ 7,700 $5,400
HHDVs $ 4,100 $2,800
Cost Effectiveness, With Averaging ($/metric ton)***
MDVs $9,800
LHDVs $5,400
- .HHDVs $2,800 --
Urban Cost Effectiveness, With Averaging ($/metric ton)
MDVs $20,000 $20,000
LHDVs $11,000 $11,000
. C.K ./.-iiDVSr -i.-~ -.i --r.f » :_^iu$.l 1^,-00 0, • -• - .• $ll-,0 0 0 -
- -i. i -c- ¦' V >2" ¦»> « • • -*- • •• ? ?'jl r'v..vj'5-ir i.' •. «- ^ • I
* Assumes all HDDVs are equipped with traps, unless
averaging is used. Trap-oxidizer systems for MDVs, LHDVs,
and HHDVs have an average lifetime cost of $472, $425, and
$1,516, respectively.
** Based on estimated annualized travel of 13,750, 23,300,
and 50,100 miles for MDVs, LHDVs, and HHDVs, respectively;
reductions are compared to relaxed scenario.
*** Averaging affects the base scenario only; average
fleetwide costs are estimated to decrease by 30 percent
(i.e., 70 percent of HDDs equipped with traps).
-------
10-18
Table 10-9 shows that under a given set of standards,
cost-effectiveness of LDDT control ranges between $1000-3000
per metric ton less than that for LDDVs, meaning that LDDT
control is slightly more cost effective. More importantly, the
table also shows that a given particulate scenario becomes less
cost effective with higher NOx standards. For example, control
is noticeably less cost effective when the NOx "standards change
from 1.0/1.2 g/mi to 1.5/1.7 g/mi. This is due to the fact
-that stringent NOx controls raise engine-out particulate levels
and increase the degree of control provided by adding a trap.
- - •• Under- a - g-iven-- NOx- standard,~~the stringent scenario" is
moderately less cost effective than the base scenario. The
difference, which ranges between 7 and 27 percent, is to be
expected, since the additional traps being applied under the
stringent scenario are being applied to vehicles with lower
engine-out particulate levels, thus providing less control.
Trap costs, on the other hand, are relatively constant.
For heavy-duty diesels (Table 10-10), cost effectiveness
improves from the lighter to the heavier vehicles. While the
emission reductions for the various HDD classes are the same on
a percentage basis, they are greater for the heavier vehicles
on an absolute basis (due to greater absolute emission rates
and qreater annual VMT). These effects more than compensate
for the increase in trap cost with vehicle size and the lower
- urban-V-MT- f r-action of-Class VII-VIII HDDs.
Without averaging, the base scenario for HDDs is less cost
effective than the stringent scenario. Without averaging, the
base scenario, like the stringent scenario, requires all^ HDDS
To" be" Equipped, with" trapse "Tt 'was'"assumed™'t'K'at* "traps' under 'tr-fie
base scenario would only be as efficient as needed, but would
cost the same as traps under the stringent scenario. Thus, the
costs of both scenarios are the same, but the emission
reduction under the base scenario is less. Thus, the higher
cost-effectiveness value of the base scenario.
With averaging, the cost effectiveness of the base and
stringent scenarios becomes the same. This is to be expected.
Trap costs and efficiency under the two scenarios are assumed
to be the same. The only difference between the two scenarios
is that only 70 percent of all HDDs are equipped with traps
under the base scenario, while all HDDs are trap-equipped under
the strinqent scenario. However, this difference affects both
costs and emission reductions. Thus, cost effectiveness
remains constant.
In general, particulate control for HDDs is more cost
effective than that for LDDs when compared under the same
scenario.
-------
10-19
III. The Intermediate Control Option
Between the relaxed scenario (no control aside from that
already applied) and the base scenario (some traps required as
a control method) there is a third scenario: the intermediate
control option. In this option a modest degree of control may
be obtained via predominantly non-trap technology. For
example, electronic fuel injection and sophisticated electronic
exhaust gas recirculation (EGR) systems (to reduce the negative
impact of stringent NOx standards) appear to be available and
able to provide some control. There is also the possibility
that certain high-emitting engine lines may be dropped in this
timeframe due to fuel economy and other pressures. Finally,
there is some indication that . oxidation catalyst technology
coupled with "sohisticated throttle control can be applied to
some diesels to substantially reduce particle-bound organics.
The effect these non-trap control techniques could have in
reducing the current corporate average particulate standard
levels, at both the 1.0/1.2 g/mi and 1.5/1.7 g/mi NOx standard
levels, will be discussed in this section.
It appears almost certain that GM will drop their
5.7-liter engine by 1987 of their own accord. (GM has already
dropped this engine from its 1984 California model line and has
indicated the engine will be eliminated from the Federal market
in 1986.) Assuming that the presently equipped 5.7-liter
engine vehicle will receive GM's 4.3-liter engine, GM's average
particulate standard would drop from 0.29 g/mi to 0.16 g/mi at
the 1.5 g/mi NOx standard and from 0.50 g/mi to 0.34 g/mi at
the 1.0 g/mi NOx standard. These large reductions in GM's
corporate average emission levels under both NOx levels would
result in substantial reductions to the total LDDV particulate
emissions, due to GM's large share (60 percent) of the total
LDDV...estimated sales. The sales-weighted-industry-wide average
-particulate "* standard"- -levels',- as--'listed in *'TarbTe 10-1', ' wbtrl^cl5
change from 0.27 g/mi to 0.20 g/mi at the 1.5 g/mi NOx standard
and from 0.42 g/mi to 0.32 g/mi at the more stringent 1.0 g/mi
NOx standard, a 25 and 24 percent reduction, respectively.
Engine-out control techniques include EGR systems and
electronic fuel injection. Sophisticated EGR systems are
available and already being applied on a few 1984 vehicles in
California to comply with its 1.0 g/mi NOx. standard. These
systems should be able to reduce the particulate penalty
associated with the stringent NOx standard by one-half. While
the effect of electronic injection is uncertain, it should
provide a benefit for the highest emitting engines; at least
improving the NOx/particulate trade-off.
-------
10-20
Some data on catalyst technology coupled with intake-air
throttling shows that it can remove most of the organics
associated with the particulate, which represent 10-20 percent
of total particulate mass. Since particulate is not
permanently stored by these catalysts, no regeneration is
needed and the * practical problems associated with
trap-oxidizers are avoided. However, one remaining question
with this technology is sulfate production. Also, it is not
certain whether catalysts would be effective on all LDD
models. At least one manufacturer (Volkswagen), which only
requires a small emission reduction to meet the current 1985
standards and should be interested in catalysts, appears to-be
concentrating all of its efforts on traps. Thus, this- analysis
will not presume the availability of catalysts under this
option.
The identification of standards actually achievable with
these techniques requires a manufacturer by manufacturer
analysis, due to their different starting points and the fact
that some of these reductions are only applicable to certain
manufacturers. Also, the two NOx standards (1.0 and 1.5 g/mi
for LDDVs and 1.2 and 1.7 g/mi for LDDTs) must be discussed
separately due to the differences in the control techniques*
effects on particulate emissions at these different NOx levels.
Beginning with LDDVs at the more stringent NOx standard
and GM, the application of sophisticated EGR systems and the
discontinuation of their 5.7-liter enaine line would reduce
their average emission level to roughly 0.23 g/mi. Use of
electronic fuel injection could reduce this level further.
" ¥ Mercedes-Benz, on the other hand, appears to be in a. very
different position. Since it has not projected the
discontinuation of any of its engine lines, nor has there been
any indication that simple changes in basic engine design are
forthcoming, emissions of its 3.0-liter engine will not be in
line with those of the other manufacturers, though its new
2.2-liter engine has relatively low emissions. Mercedes-Benz
has actually indicated to California that, in 1985, they plan
to equip their 3.0-liter engines with traps to meet the 0.4
g/mi California particulate standard coupled with the 1.0 g/mi
NOx standard. Improved EGR systems should be able to reduce
their corporate average from 0.60 g/mi to at best 0.40 g/mi.
Electronic injection could further reduce this figure, but
probably not below 0.35 a/mi. At the same time, Mercedes-Benz'
trap development program appears to be more advanced than those
of the other manufacturers and they appear ready to implement
traps in 1985. Also, one cannot rule out the use of major
engine modifications to bring its 3.0-liter engine emissions in
line with those of other manufacturers. Overall, it appears
most likely that Mercedes-Benz would probably require traps at
or below 0.40 g/mi, but will also be in good position to do
-------
in-21
Concerninq the other LDDV manufacturers, improved EG"
svstems alone should reduce their averaqe emission level to
0.30 a/mi or below, except possibly for Peugeot, due to a
sinale hiah-emitting vehicle configuration. Electronic fuel
injection and other enaine modifications mav he able to reduce
these levels to 0.25 a/mi.
Overall, these techniaues could reduce oarticulate
emissions rouahlv 30-40 oercent from the relaxed scenario's
0.42 a/mi sales-weiahted industrv-wide averaae value at a 1.0
a/mi NOx standard. Thus, an L.DDV standard ranae of 0.25 to
0.30 a/mi should he achievable without manv traDs, exceDt for
Mercedes-Benz. In the case of Mercedes-Benz, it does not
aDoear reasonable to limit the achievable emission standard to
0.40 a/mi or even hiaher based on a sinale manufacturer or
vehicles no laraer or smaller than other manufacturers. Thev
and possiblv others would simply have to apoly traps to a
limited number of vehicles in order to obtain the final dearee
of control.
At the hiaher NOx standard level of 1.5 a/mi for LDDVs,
the enaine improvements just discussed will not have as larae
an effect on particulate emissions as just seen at the more
strinaent NOx standard. The particulate/NOx tradeoff, as
discussed in the technoloav chaDter, levels out as the ^Ox
level increases from the 1.5 a/mi NOx standard level. The
oarticulate emission reduction due to enaine improvements
combined with the discontinuation of the CM 5.7-liter enaine
would result in an overall I.DDV standard of approximately
0.18-0.20 a/mi. At this level some traps will be necessary for
the hiaher-emittina enaines of Mercedes Benz and Peuaeot
althouah not to the extent needed at the 1.0 a/mi NOx standard.
^he application of these non-trao control techniaues to
LDDTs also reduces their averaae oarticulate emission levels
from those shown in '''able 10-2, althouah to a far less extent
than the LDDV emission reduction. Unlike LDDVs, there are no
discontinuations projected for anv of the hiaher-emittina
enaine lines. These techniques could reduce the sales-weiqhted
industrv-wide averaae values from 0.5? a/mi to approximately
0.35 a/mi and from 0.33 a/mi to aDDroximately 0.30 a/mi, for
NOx standards of 1.2 and 1.7 a/mi, respectivelv.
The sales-weiahted industry-wide oarticulate levels under
the intermediate control option are shown in ^ahle 10-11. ^his
table includes both LDDVs and LDDTs corporate averaae
particulate standard levels at the two NOx standards. For the
LDDVs, the hiaher value of the standard ranae was included, as
a conservative projection. The percentaae of vehicles
requirina traps is also shown in Table 10-11. Applving the
-------
10-22
Table 10-11
The Effects of Advanced Control
Technoloav Improvements on the Sales-Weiqhted
Industry-wide Average Particulate Standard Levels
LDDV LDDT
TTO 175 172 TT7
Scenar io NOx Std NOx Std NOx Std NOx Std
Intermediate
Standard Level, .
' - - - g/mi. " " 0.30 0. 18-0.20 0.35 0. 30
Percentage of
Vehicles
Requirina Traos 1-2 1-2 9-16 0
Rase
Standard Level,
g/mi 0.20 0.20 0.26 0.26
Percentage of
Vehicles
Reouirinq Traps 10-20 1-2 41 16
-------
10-23
advanced control technologies described above and also
includinq- the effects of dropping the GM 5.7-l enaine will
reauire approximatelv one to two percent of LDDV enqines to he
equipped with traps under the intermediate scenario for both a
1.0 and 1.S a/mi NOx standard. (The more strinaent NOx
standard will reauire aoDroximately an eaual amount of traps as
the less strinaent 1.^ NOx standard due to its hiaher corporate
averaqe particulate standard level under the intermediate
scenario.) fcpplvina the advanced control technoloaies to LDD'r
results in 9-16 percent of the LDD^s at the 1.2 a/mi NOx
standard reauirinq traps; at the 1.7 a/mi NOx standard, no
traps are necessarv.
Tn addition to usina onlv traps as a control method under
the base scenario, it is of interest to project the percentaae
of vehicles reauirina traps if the advanced control
technoloaies of the intermediate scenario are also applied
under this 0.20/0.26 a/mi LPDV/LDD'r particulate standard
scenario. Ten to 20 percent of the LDDVs will be equipped with
traps under the 1.0 a/mi NOx standard, while one to two percent
will reouire traps under the 1.5 q/mi NOx standard. it has
also been assumed that the 5.7-L enaine will be drooped from
the GM enqine line. with the advanced control technoloqy
improvements applied to LDDTs, 45 percent of the full-size
LDDTs and 31 percent of the small LDDTs will require traos at
the 1.2 a/mi NOx standard. (Fortv-one percent of all LDDTs
will require traps.) At the 1.7 a/mi NOx standard, 18 percent
of the small LDDTs and ].l percent of the small LDDTs will be
trap-equipped. (Sixteen percent of all LDDTs will be
trap-eauipped.) These percentaaes of vehicles reauirina traps
under the base scenario are shown in ^able 10-11.
TV, Comparison of. .Uncontrolled and- ^ontro1-l.e.d. ^pn Fmis.sions
Urban diesel particulate emission? from ^DDs were
estimated for the relaxed control scenario in Chapter 2.
"owever, the corresoondina values for a completelv uncontrolled
"DD fleet were never derived in that chapter because such a
strateqv is not considered to be a viable option.
Nevertheless, it is of interest to know what future urban HDD^
emissions would be if the fleet were totallv uncontrolled so
that the benefits of the relaxed control scenario in particular
can be placed in perspective.
As indicated in Chapter 1, uncontrolled "DD^s are
estimated to emit particulate at a rate of 0.7 g/BF^-hr
throuahout their lifetime. Usina the methodoloav of Chapter 3,
the resulting vehicular emission factors are shown in Table
10-12. Table 3.^-1"* presents the 3995 urban particulate
emissions for the various HDDV scenarios using best estimate
-------
10-24
Table 10-12
Uncontrolled HDDV Emission Factors By Model Year (g/mi)
MDV LHDV HHDV
Model Year Class ilB Classes III-V Class VI Classes VII-VIII
1995
0.930
1.212
1.611
2.489
1994
0.930
1.216
1.611
2.492
1993
0.930
1.221
1.611
2.497
1992
0.930
1.221
1.611
2.501
1991
0.930
1.221
1.611
2.506
1990
0.930
1.234
1.611 .. .
2.509
1SI89
0.936 ~
1.2 35
1.612
2.514
1988
0.943
1.235
1.612
2.519
1987
0.951
1.239
1.614
2.530
1986
0.967
1.239
1.614
2.531
1985
0.968
1.243
1.614
2.550
1984
0.977
1.247
1.617
2.558
1983
0.993
1.247
1.620
2.561
1982
1.00 2
1.247
1.628
2.577
1981
1.003
1.252
1.651
2.587
61-80
1.014
1.256
1.651
2.597
-------
10-25
Table 10-13
HDDV Urban Emissions in 1995
Best Sales Estimates (metric tons per year)
Uncontrolled Relaxed Base Stringent
88,000 77,000 40,800 25,300
-------
10-26
sales projections. Relative to the uncontrolled scenario, the
relaxed scenario would reduce particulate emissions about 12
percent, the base scenario about ?4 percent, and the strinaent
scenario about 71 percent.
V. Effect og Changes in Diesel Sales Projections on Urhan
Particulate Levels ' " ~~~
T'hrouahout this report, Diesel particulate emissions were
evaluated usino pPA's best and worst diesel sales projections.
The "-best case" projection is based on a reversal of verv
recent conditions (where LPDV sales have been decreasing) and
shows moderate growth in sale?. The "worst case" projection
represents a sianificant (or maximum) arowth in diesel sales
that could result from another oil crisis. Therefore, the
worst case is an upper bound on future diesel sales. Of
course, it is also possible that the demand for diesel-fueled
vehicles will not continue to. increase if Petroleum supplies
remain abundant and the fuel price does not escalate. In order
to indicate the effect on diesel particulate of this latter
sales projection, a "no arowth case" will be evaluated.
In constructing the no arowth diesel projection, LDDV and
LHDT historical diesel and total sales fractions were used for
model years 19K9-R3. future model year diesel sales fractions
were then found bv simolv continuina the lo*5! model vear values
throuah the 19^5 model year. For hddvs, historical data were
similarly used for model vears 1Q6Q-82. ^he 1983 model vear
sales fraction was determined from projections made bv Eneray
and Environmental Analysis, Inc. [21 and were extrapolated
throuah1 ""'the "'199*5 * model" v'ear.' TKe" "r esult in a'.' ..'no', a-row.th. ^ ,sal£s"
'projection is shown in Table 10-14.
Diesel particulate emissions under the no growth case for
anv calendar vear can now be calculated bv combinina the
respective diesel sales fractions with the other inputs as
described in chapter 2. To illustrate the effect of usina this
alternative arowth projection, Table 10-15 contains a
comparison of urban diesel particulate emissions for the base
scenario under this sales estimate to those associated with the
best estimate projection. As shown, in the 1995 calendar vear,
the overall effects of no arowth in diesel sales is a 3*
percent reduction in projected emission levels associated with
the best estimate. Tndividuallv, the laraest chanae is shown
for LnD^s (i.e., a 71 percent reduction), while the smallest
chanae is shown for FHDVs (i.e., a 13 percent reduction). The
percent chanae within each vehicle cateaorv shown here for the
base scenario also will be similar for the other control
scenarios if the no arowth sales projection was used in place
of the best sales estimate.
-------
10-27
Table 10-14
Diesel Fraction of Total Sales
foe LDDs and HDDVs—No Growth Estimate
Model
Class -
Classes
Classes
Year
LDDV
. LDDT
IIB
iri-v
Class VI
VII-VIII
1995
.030
.060
.162
.162
.377
.810
1994
.030 •
.060
.162
.162
.377
.810
1993
.030
.060
.162
.162
.377
.810
1992
.030
.060
.162
.162
.377
.810
1991
.030
.060
.162
.162
.377
.810
1990
.030
.060
.162
.162
.377
.810
1989
.030
.060
.162
.162
.377
.810
1988
.030
.060
.162
.162
.377
.810
1987
.030
.060
.162
.162
.377
.810
1986
.030
.060
.162
.162
.377
• 810
1985
.030
.060
.162
.162
.377
.810
1984
.030
.060
.162
.162
.377
.810
1983
.030
.060
.162
.162
.377
.180
1982 ,
.040
.070
.074
.108
.214
.928
1981
.061
.060
.037
.054
.164
.918
1980
.034
.034
.000
.000
.114
.910
1979
.028
.028
.000
.000
.114
.890
1978
.009
.009
.000
.000
.078
.880
1977
.004
.005
.000
.000
.070
.850
1976
.003
.003
.000
.000
.042
.830
1975
.003
.002
.000
.004
.032
.730
1974
.003
.000
.000
.001
.016
.770
1973
.003
.000
.000
.003
.016
.780
1972
.003
.000
.000
.020
.016
.760
1971
.003
.000
.000
-.020
.016
.750
1970
.000
.000
.000
.020
.016
.750
- 19 69--
".000" '
^ >000 '
• ...000~
. " .000 '
i .000""
. 7 5 03
""and latfer
-------
10-28
Table 10-15
1995 Urban Diesel Particulate Emissions
Under the Base Scenario (metric tonsl*
% Reduction
Best Estimate No Growth from
Diesel Sales Diesel Sales Best Estimate •
LDDV 19,700 10,100 49
LDDT 11,700 3,400 71
MDDV/LHDDV 4,800 2,700 44
HHDDV 36,100 30,300 L3
TOTAL 72,200 46,500 36
Assumes' an LDDV NOx standard of 1.0 g/mi "and an LDDT NOx
standard of 1.2 g/mi.
-------
APPENDIX
-------
Table A-l
Estimates of the Potency of Organic Extracts of Diesel
Exhaust and Related Environmental Emissions - Harris*
Emissions Extract
Coke Oven
Roofing Tar
Caterpillar 3304
Diesel Engine
Nissan Datsun 220-C
Diesel Engine
Oldsmobile 350
Diesel Engine
Volkswagen Turbocharged
Rabbit Diesel Engine
Benzo(a)pyrene
Positive Control
Tumor Initiation
in SENCAR Mice
(papillomas/mouse
per mg extract
at 27 weeks)
2.101
(0.090)
0.535
(0.024)
0.011
(0.009)
0.528
(0.023)
0.156
(0.034)
85.28
(2.71)
Enhancement of SA7 Viral
Transformation in Syrian
Hamster Embryo Cells
(tr an for mat ions/2x10
cells per ug extract/ml)
0.859
(0.089)
2.066
(0.363)
0.039
(0.023)
0.645
(0.095)
0.067
(0.023)
0.128
(0.023)
540.
(21.9)
Table excerpted from Reference 1. Maximum likelihood estimates of
..slope of ^linear. dose response model, based upon- Poisson distr ibution-
of positive responses. Asymptotic-standard errors in parentheses-.0'5 5
-------
Table A-2
Estimates of Potency of Organic Extracts of
Diesel Exhaust and Related Environmental Emissions
in L5178Y Mouse Lymphoma Mutagenesis Assay - Harris*
Emissions Extract
Average Mutant
Survivors Per
- Metabolic
Activation
Colonies/10^
ug Extract/ml
+ Metabolic
Activation
Coke Oven
0.726
9.963
(0.152)
(0.734)
Roofing Tar
0.311
9.556
(0.121)
(1.547)
Caterpillar 3304
0.156
0.049
Diesel Engine
(0.038)
(0.021)
Nissan Datsun 220-C
1.662
1.869
Diesel Engine
(0.509)
(0.485)
Oldsmobile 350
0.270
0.764
Diesel Engine
(0.117)
(0.109)
Volkswagen Turbocharged
2.545
1.012
Rabbit Diesel Engine
(0.402)
(1.200)
Table excerpted from Reference 1. Maximum likelihood
estimates of slope of linear dose response model based
upon• ¦-Poisson ; "dis'tr ibution of positive - responses.
Asymptotic standard errors in"parentheses'.
-------
Tahle A-3
SuMury of RtsulU Pron MiUqeimls and Carcinogenesis Assays Vblng
Diesel Enhauat Particle Extracts and Other Surrogate Subetanoea - towlaot*
Surrogate
Baxiaure
MCS
assay
uspmt cae
LOCUS ASSAY
HOUGE LYMPIKMA
CELL ASSAY
BAm/JT} CELL
ASSAY
HutantVIO6 Hutants/106 Citation Transformation IIM0RR MBRYO
Revertants Par Survivors Per Survivors Per Frequency Frequency CHX. ASSAY
X 10s
100 ug attract ug/al attract ug^al Bttract
With n/5
S-9 S-9
With
8-9
With N/0
S-9 S-9
X 105
Transformations
6BCAR MOUSE SKIN
ASSAY
Papillomas Carcinoma
With N/0 With N/0 Per 2 X 10s Chi la per House per House
8-9 S-9 S-9 S-9 Par wM Extract at 1 m at 1 m
Diesel
Vehicle
Exhaust
Ooka Oven
Balsa Ions
Rooting
Iter Vapors
Cigarette
Stoke
Condensate
300 500
250
100
100
10
0
0
0.2
6
6
0.06
1.9 1.7 0.5 0.51 -0.5 0.3
10 0.7 n.a. 8.3 2.5 2.1
10 0.3 1.7 3.1 1.1 0.6
0.5 0.6 n.a. n.a. n.a. n.a.
0.6
0.86
2.1
0.6
0.25
2
0.4
0.2
0.05
0.1
0.1
0.1
Urban Soot 100 n.a.
n.a.
ifieA* n»A« n*A« n*A« n«A«
n.a.
n.a.
* This tattle was emerpted (rat Reference 15.;
-------
Table A-4
- Summary of Results for Human Lung Cancer
Annual Unit Risks - EPA* (risk/uq organics/m ^
Emission Source Lower Limit Best Estimate Upper Limit
Coke Oven[a] . 6.6 X 10"^ 1.2 X 10~5 2.0 X 10~5
Roofing Tarfa] 1.3 X 10~6 4.7 X 10~6 9.4 X 10"6
Cigarette Smokefb] 1.7 X 10-8 2.9 X 10~®[c] 4.9 X 10""®
* This table was excerpted from Reference 16 in which
lifetime risks were presented. These risks have been
converted to annual risks by dividing by the median
lifespan (76.2 years).
[a] 95 percent confidence intervals for linear model,
[bj Bounds from linear and quadratic model.
[c] Geometric mean of the limits-.
-------
Table A-5
Summary of Dose-Response Slopes for
Emission Extracts Short Term In-Vitro Bioassays - EPA*
SamDle
Mutation in
L5178Y Mouse
Lymphoma Cells[b]
(-MA)[a]
(+MA)
SCE in
CHO Cellsfcl
(-MA) (4-MA)
Ames Salmonella
Typhimuriium TA98fd1
(-MA) (+MA)
Human
Carcinogens:
Coke Oven
. 0.71
12.
0.41
0.03
0.7
-1.1
Roofing Tar
0.39
17.
0.12
0.02
Neg[e]
0.86
CSC
0.39
0.79
0.12
0.08
Neg
0.57
Diesels:
Nissan
4.2
2.9
0.30
0.071
11.
13.
Volkswagen
0.98
0.72
0.075
0.030
3.8
3.0
Rabbit
Oldsmobile
1.2
1.3
Neg
0.017
2.2
1.5
Caterpillar
0.25
0.063
0.011
Neg
0.38
0.31
*This table was excerpted from Reference 16.
[a] MA » Metabolic Activation.
fbj Mutation frequency (TK mutants/10® surviving
cells)/ua/ml.
[c] SCE/cell/ug/ml, (-MA) was a 21.5-h exposure and (+MA) was
~ a 2-h exposure.
[d] Revertants/ug (from simple linear regression analysis).
[e] Neg = Negative, i.e., no response.
-------
Table A-6
Sample
Human
Carcinogens:
Coke Oven
Tops ide
Roofing Tar
CSC
Diesels:
Nissan
Volkswagen
Rabbit
Oldsmobile
Caterpillar
Gasoline
Catalyst
SENCAR Mouse Skin Tumor Initiation and
Complete Carcinogenesis by Emission Extracts*
Multiplicity
Data (papillomas/
mouse at 1 mg)
Skin Tumor Initiation
Incidence Data (dose
2.1 [d] (1.0)
0-41[d] (0.20)
0.0024 [a ,e)
(0.0011)
in mg yielding 25%
mice with papillomas)
0.16[b] (1.0)
0.71[b] (0.22)
92. (0.0017)
Skin Cancer
Incidence
Data (dose
25%
mice with carcinoma
in mg yielding 25% £
4.0[c]
0.59[d] (0.28) [f 1
0.24[a]
0.31[a]
Neg[h]
0.61[b] (0.26)
[q]
^ This table was excerpted from Reference 16.
[a] Values based directly on papilloma multiplicity data at 1 mg.
[bj Values based on statistical analyses of the papilloma incidencje,1W
log-Probit model with background correction.
[c] Values based on carcinoma incidence data.
[d] Values based on statistical analyses of the papilloma multiplicity data
by a Poisson model with background correction.
[el Nesnow, Triplett, and Slaga, unpublished observations.
[fj Values in parentheses are normalized to the coke oven topside sample.
[g] Nissan produced carcinomas in 4 percent of the mice at the 4-mg/week
dose level,
rh) Neg = negative levels.
-------
Table A-7
Comparison of Relative Potencies of
Emission Extracts in Several Bioassay Systems - EPA*
Emission Source
Coke Oven[bl
Roofing Tar
Ciqarette
Smoke
Nissan
Diesel
Mouse
Skin Tumor
Initiation
1.00
0.20
0.0011
0.29
Mouse
Sk in
Cancer
1.00
0.20
NT(c]
0.10
Mutation
in Mouse
Lymphoma
Cells(+MA)r a 1
1.00
1.40
0 .066
0 .24
Mutation
in Ames TA98
(+MA) ral
1.00
0.78
0.52
12.00
Human
Lung
Cancer
1.00
0.39
0.0024
ND fdl
* . This table was excerpted from Reference 16.
[al (+MA) = with Metabolic Activation.
[bj Absolute value of annual unit risk is 1.2 x 10"5.
[cl NT'= Not Tested.
[dl ND = No Data.
-------
Table A-8
Comparison of Relative Potencies of
Emission Extracts in Several Bioassay Systems - EPA*
Mutation in SCE in Mutation in Net
Diesel Mouse Lymphoma CHO Cells Ames TA98 Relative
Source Cells (+MA) fa1 (+ma) [al (+MA) fa1 Potency
Nissan[b]
1.00
1.00
1.00
1.00
Volkswaaen
0.25
0.42
0.23
0.30
Oldsmobile
0.45
0.24
0.11
0.27
Caterpillar
0.022
NEG[c]
0.023
0.015
* This table was excerpted from Reference 16, except for the
last column, which was derived from the final risk
estimates of Table 3.
[a] (+MA) = with metabolic activation.
[b] Absolute value of annual unit risk is 0.58 x 10~5.
fc1 NEG = negative (i.e., no response).
-------
Table A-9
Ames Test Results on Diesel
Vehicles (using TA-98 strain)
Studv/Reference
Landman/Wagner[17]
McMahon, et.al. [18]
Hyde, et.al.[19]*
Claxton[20]
Veh icles
In-use Oldsmobiles
( 40k miles)
Peugeot
Prototypes
(Mercedes-Benz,
Peugeot)
VW Rabbit
GMC
VW Rabbit
Mercedes-Benz
Others
Diesel Engine
Diesel Vehicles
Mean
Specific Activity
frevertants/uq SOF)
(-MA)
13.7+7.4
6.4 6+4 .49
11.1+3 .9
5.84+6.6
1.24+0.52
1.10+0.77
0.97+0.27
0.97+0.24
4.35+0.64
6.96 + 4 .06
(+MA)
8.22+2.75
2.0 8+0.4 6
8.66+4.59
5.26+1.57
Overall Mean ==..
5 ,27
6.06 .
All vehicles in this study were in-use diesels.
-------
Table A-1Q
Total Particulate and SOF Emission
Rates for LDDVs with and Without Ceramic Traps
Manufacturer
Without TraD
With
Trap
+ %
Chancre
Veh icle
Trap
TPM
SOF
TPM
SOF
. TPM
SOF
[22] Ford
-- (1)
436
309
192
173
-56
-44
303
138
63.6
56.6
-79
-59
436
309
91.6
83.4
-79
-73
303
138
75.8
63.5
-75
-54
f23]Mercedes
Corning
0.25
0.018
0.050
0.004
-80
-78
(2)
• •
— —
—
-90
-75
(231 Datsun
NGK (2)
0.17
0.045
0.040
0.012
-76
-73
[241 GM
Corning
—
—
- -
-89
-77
-97
-92
Average =
-80
-69
1 ] Reference
(1) ma/mi
(2) g/km
-------
Table A-ll
Total Particulate and SOF Emission Rates
for WDDV and HDDEs With and Without Ceramic Traps
Manufacturer without Trap with Trap + % chanae
Vehicle Trap TPM SOF TPM SOF TPM SOF
I25]Caterpillar
Engine Corning 1.047 0.932
(1) 0.482 0.377
0.241 0.038
0.795 0.026
0.792 0.133
^ .. 1.864 0.969
[26] DDAD
Coach Engine
Corning
0.70
0.20
0.15
0*11
-78.6
-45.0
(1)
0.86
0.49
0.28
0.24
-67.5
-51.0
0.70
0.39
0.30
0.25
-57.1
-35.9
0.75
0.40
0.29
0.25
-61.3
-37.5
0.78
0.54
0.25
0.20
-68.0
-63.0
[26] GMC
Corning
5.48
0.46
0.589
0.073
- -89.3
-84.1
Coach
(2)
4.24
0.28
0.313
0.035
-92.5
-87.5
Vehicle
4.4
0.31
0.350
0.040
-92.1
-87.1
6.2
0.41
0.430
0.049
-93.1
-88.1
Average = -76.3 -68.0
1.039
0.173
0.015
0.022
_0.022
0.139
0.972
0.137
0.002
0.0005
0.006
0.067
-0.76
-64.1
-93.8
-97.2
-97.2
+4.3(a)
-63.7
-94.7
-98.1
-95.5
I I Reference
(1) a/kw-hr
(2) g/km
(.a.)~--=E-PA .T-est- Mode -3
-------
Table A-12
SOF as Percent of Total Particulate
for LDDVs With and Without Ceramic Traps
Manufacturer
Vehicle
Trap
Without
Trap
With
Trap
Percent" Change
r 22]
Ford
70.9
90.1
+19.2
45.5
89.0
+43.5
70.9
91.0
+20.1
45.5
83.8
+38.3
[23]
Mercedes
Corning
7.2
8.0
+0.8
[23]
Datsun
NGK
26.5
30.0
+3.5
[241
GM
Corning
25.5
55.1
+29.6
25.0
57.0
+ 32.0
Average *
+23.4
[ ] Reference
-------
Table A-13
SOF as Percent of Total Particulate
for HDDV and HDDEs With and Without Ceramic Traps
Manufacturer
Vehicle
Trap
[25]Caterpillar
Engine(a)
Corning
[26] DDAD
Coach Enaine
Corning
[26] GMC
Coach Vehicle
Corning
Without
Trap
89.0
78.2
15.8
3.3
16.8
52.0
28.9
56.8
56.1
56.2
64.6
8.4
6.6
7.1
6.6
With
Trap
75
84
82
82
81
12.4
11.2
11.4
11.4
Pe-rcent Chance
93.6 +4.6
79.2 +i.o
13.3 -2.5
2.3 -1.0
27.3 +10.5
48.2 -3.8
0 +46.1
4 +27.6
1 +26.6
9 +26.7
8 +17.2
+ 4.0
+4.6
+4.3
+ 4.8
Average » +11.4
(a) Caterpillar test modes: EPA 3, 4, • 5, 9., 1011.
-------
Table A-14
Gaseous HC Emissions for LDDVs
with and without Ceramic Traps
Manufacturer Gaseous HC Emissions
Vehicle
Tr aD
Without
Trap
With
Trap + Percent Chanae
[22]
Ford (1)
0.99
0.90
-9.1
0.61
0.60
-1.6
0.99
0.63
-36.4
0.61
0.47
-22.9
[17]
Toyota (1)
NGK
0.405
0.313
-22.7
0.223
0.161
-27.8
[17]
Mercedes
Corning
0.266
0.230
-13.5
(1)
0.092
0.091
-1.1
[23]
Mercedes
Corning
0.0970
0.0645
-33.5
(2)
[23]
Datsun (2)
NGK
0.20
0.18
-10.0
[24]
GMC (3)
Corning
38
38
0
26
26
0
26
25
-3.9
27
26
-3.7
28
28
0
Average *
» -12.4%
TT~T Indicates reference
(1) g/mi
(2) a/km
(3) ppm-C3
-------
Table A-15
Gaseous HC Emissions for HDDV and
HDDEs With and Without Ceramic Traps
Manufacturer
Veh icle
TraD
[25] Caterpillar
Engine Corning(l)
[26] DDAD
Coach Enaine
Corn ing(1)
[26] GMC Coach
Vehicle
Corning(2)
Gaseous HC
Without
Trao
1.917
0.771
0.253
0.265
1.305
2.926
1.64
1.85
1.91
1.90
1.93
1.78
1.52
1.56
2.25
Emiss ions
wTtfi
Trap Percent Change
2.152
0.591
0.178
0.111
0.510
2.077
1.68
1.88
1.89
1.89
1.83
1.10
1.01
1.02
1.47
+ 12,
-23 *
-29
-58,
-60,
-29
3
4
6
1
9
0
(a)
+ 2.44
+1.62
-1.05
-0.53
-5.18
¦38.2
•33.6
•34.6
•34.7
(b)
[ 1 Reference
(1) g/kh-hr
(2) g/km
(a) EPA Mode 3 (test condition)
(b) 13-Mode composite
Average » -22.17%
-------
Table A-16
Gaseous HC Emissions During Durability Test
of Corning Trap on Mercedes 300SD [reference 231
.HC Emissions (a/km)
(inOOs km)
Without
Trap
With
TraD
+ Percent Chanae
0
0.11
0 .080
-27
8
0.11
0.070
-36
- 16
0.12
0.080
-3 3
24
0.09
0.060
-33
32
0.08
0.070
-12
40
0.09
0.055
-39
48
0.09
0.070
-22
56
0.10
0.053
-47
64
0.09
0.060
-33
72
0.09
0.041
-54
80
0.10
0.068
-32
Average = -33.5%
-------
Table A-17
Ames Test Bio-Activity Data on SOP for LDDV
With and without Ceramic Trap [reference 271
Test Condition
Trap; Enqine
Without
(a)per
mass
Trap
oer(d)
VMT
With
per
mass
Trap
per
VMT
+ 1
per
mass-
Chanqe
per
VMT
Clean Trap, A
1.9
5.9
3.7
6.4
+94 .7
+8.5
Clean Trap, B
2.0
2.8
5.1
3.0
+155
+7.1
Loaded Trap, A
1.9
5.9
3.6
3.0
+89.5
-49.2
Loaded Trap, B
2.0
2.8
4.3
2.9
115
+3.6
Average ¦
+113.6
-7.5
("al Bio-activity per mass, units of revertants/ug SOF.
(b) Bio-activity per vmt, units of revertants/mile x 10~5
-------
Table A-18
Ames Test Bio-Activity Data on SOP for
HDDE With and Without Ceramic Trap [reference 251
Test Mode
without
(a)per
mass
Trap
per(b)
work
With
per
mass
Trap
per
work
+ %
per
mass'
Chanqe
per
work
3
0.408
363
0.392
365
-3.92
• +0.55
4
0.251
92
1.404
193
+ 459
+ 110
5
1.319
54
1.524
3.3
+15.5
-94.0
9
0.851
22
2.482
2.6
+ 192
CM
•
CO
CO
1
10
0.762
101
1.620
10.7
+ 113
-89.4
11
0.357
325
1.250
87
+ 250
-73.4
Average =
+170.9
-39.1
(a)
(b)
3io-activity per mass, units of revertants/ug SOF
Bio-activity per work, units of revertants/kw-hr
-------
Table A-19
Temperature Range Distribution of SOP for
HOPE With and Without Ceramic Trap [reference 261
Percent Boiling-Point Temperature,°C
Mass Released without Trap With Trap + % Change
IBP 307 340 +10.8
10 391 396 +1.28
20 412 418 +1.46
30 432 435 +0.69
40 452 450 -0.44
50 474 465 -1.90
60 503 480 -4.57
70 542 499 -7.93
80 607 530 -12.7
-------
Table A-20
BaP Emission Rates for HDD Engine and Vehicle
with and without Corning Ceramic Trap [reference 26)
Test Conditions
BaP Emission Rate
Without
TraD
with
Trap
' + % Change
Coach (1)
Engine:
7-mode 0.04
Transient 0.08
Bus Cvcle 0.11
0.12
0.28
0.11
+ 200
+ 250
0.0
Average
150%
In-Service
Coach (2):
Transient
Bus Cycle
0.050
0.008
0.055
0.022
+9.6
+ 175
Average =
92%
(Tj BaPT~ug7T
-------
Table A-21
Trap Removal-Efficiencies of
Carcinogens with Respect to Total Particulate
Average %
Change
Ratio of
Percent Changes
Carcinogen
Studv
Carcinogen
TPM
Average
Range
SOF
Ford
Mercedes
Datsun
GM
-56.5
-76.5
-73.3
-84.5
-77.0
-85.0
-76.5
-93.0
.74
.91
.96
.91
.72-.75
.83-.98
.96
.87-.95
-
Caterpillar
DDAD Engine
GMC Coach
-89.0
-46.5
-86.7
-89.0
-66.5
-91.8
1.0
.70
.94
.98-1.01
.57-.93
.94-.95
Mutagens
Ford
-7.5
-72.3
.10
.10
Caterpillar
-86.3
-89.0
.91
.79-1.0
BaP
DDAD Engine
GMC Coach
+ 150 "
+92
-66.5
-91.8
-2.53
-.99
(-4.1)-0
(-.104-(-1.
-------
Reference
1. "An Evaluation of Particulate Levels Occurring Under
1.0/1.2 g/mi NOx Standards for LDDVs and LDDTs," R. Kanner,
Technical Report, SDSB, U.S. EPA.
2. "Historical and Projected Emissions, Conversion
Factor, and Fuel Economy for Heavy-Duty Trucks: 1962-2002,"
prepared by Energy and Environmental Analysis, Inc., for the
Motor Vehicle Manufacturers Association, December 1983 ^
------- |