&EPA
United States
Environmental Protection
Agency
Mobile Source Research
Committee
Washington DC 20460
Technology Transfer
The Diesel Emissions
Research Program
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-------
Technology Transfer EPA-625/9-79-004
The Diesel Emissions
Research Program
Program Report—Mobile Source
Research Committee
Office of Research and Development
Office of Health Research
Washington, DC 20460
Environmental Monitoring Systems Laboratory
Research Triangle Park, NC 27711
Environmental Sciences Research Laboratory
Research Triangle Park, NC 27711
Health Effects Research Laboratory
Cincinnati, OH 45268
Health Effects Research Laboratory
Research Triangle Park, NC 27711
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
Office of Air, Noise and Radiation
Office of Mobile Source Air Pollution Control
Washington, DC 20460
December 1979
Center for Environmental Research Information
Cincinnati, OH 45268
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Page
Table of Contents Introduction 1
About Diesel Exhaust 3
Program Strategy 4
From Risk to Regulation 6
Collection and Characterization of Particulate Matter 7
Identification of The Potential Health Threats 9
Epidemiologica! Studies 9
Animal Studies 10
Cancer and Related Effects 10
Noncarcinogenic Effects 19
In Vitro Studies 22
Air Monitoring Studies 26
Exposure 28
Risk Assessment 30
Control Technologies 32
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Introduction
^l^^^^mm
Mobile Sources Res^p9^ eff orUhe
evaluate the public hMi*u P™9ra™, to
-OMSAPC
'"wo cancer and
mutation studies
Epidemiology
Cincinnati,
'AnnArbor, Michigan
Washington, D.C.
-OHEA
assessment
Research rr/ang,ePark
Worth Carolina^
HERL-RTP
• In vitro cancer and
mutation studies
• In vivo cancer and
mutation studies
ESRL-RTP
* Exposure
EMSL-RTP
collection
• Exposure
-------
Parti culate
collection and
characterization
(20%)
Of control
technologies
(7%)
Epidemiological
studies
(1*1
Air
monitoring
(13%)
Development of
control
technologies
(6%)
pidemiologica'
studies
(3%)
in vivo
studies
(32%)
Air
monitoring
(12%)
)n vivo
studies
(31%)
In vitro
studies
(22%)
TOTAL FUNDING
1978 $4,7 million
1979 $7-2 million
Funding allocates for
includes:
. Human P°Pu!ati™
plains how me m
with i
engine
use
microorganism
. Chemical characterization of
diesel particles
• « r,f dipsel poHutant
. Monitoring of diesen
levels in ambient air
popula
tion ex
emissions-
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About Diesel Exhaust
Diesel exhaust is a mixture of
particulate (sooty) matter and
various gases. The principal
gases present in diesel exhaust,
such as hydrocarbons, nitrogen
oxides, sulfur oxides, carbon
dioxide, and carbon monoxide,
are similar to those already
emitted into the atmosphere by
gasoline engines and other
combustion emission sources.
They are not expected to pose a
new regulatory problem to the
EPA because regulatory
mechanisms already exist for
controlling levels of these
pollutants.
The particles in diesel emissions,
however, differ significantly in
both quantity and composition
from the gasoline particles they
will replace. Even a well-tuned
diesel engine emits 30 to 100
times more particulate material
than a comparable gasoline
engine equipped with a catalytic
converter.* While gasoline
particles are principally sulfur
compounds, diesel particles
consist of a carbonaceous
(carbon-containing) material
with primarily high molecular
weight organic chemicals
adsorbed (attached) to the
particle surface. These
chemicals, initially present in
diesel emissions as trace
gaseous components, condense
onto the particles as the exhaust
coois. They may constitute 10 to
50 percent by weight of a diesel
particle, with the actual
•Comparable figures are not available for
controlled diesel engines, since diesel
particulate control devices are still being
developed. However, it is likely that a
controlled diesel engine will still emit
substantially greater quantities of
particles than catalyst-controlled
gasoline engines.
percentage and composition
depending on such factors as
engine type, fuel type, driving
pattern, and engine efficiency.
Also of concern from a public
health standpoint is the fact that
many diesel particles are
respirable. That is, they are small
enough to penetrate deep into
the lung where either the
particles themselves or the
attached organics may cause
adverse health effects.
Preliminary biological and
chemical tests have shown that
diesel particles may be
carcinogenic. What scientists do
not yet know is whether exposure
to environmental levels of diesel
emissions will increase the
incidence of cancer in exposed
populations. Studies to help
answer this question are an
important part of ORD's diesel
emissions research.
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Program Strategy
The primary purpose of the
Diesel Emissions Research
Program is to assess the human
health risk associated with
conversion of passenger vehicles
from gasoline to diesel fuel. The
basic program strategy for
accomplishing this goal is
illustrated in Figure 1.
To determine the range and
magnitude of potential health
effects, ORD is examining whole
diesel emissions, as well as
gaseous (particle-free)
emissions, diesel particles, and
chemical extracts of diesel
particles in a variety of
experiments involving animals,
plants, insects, mammalian cells,
and microorganisms (Figure 2).
These laboratory experiments
are being supplemented by
studies of disease patterns in
human population groups who
received occupational exposure
to diesel exhaust. Additional
studies are being conducted to
compare diesel exhaust to
substances, such as cigarette
smoke and coke oven emissions,
whose carcinogenic potential is
already known from previous
epidemiological research. This
comparison will provide an idea
of the relative carcinogenic
potency of diesel emissions. By
combining the health effects data
with population exposure
projections, the EPA will assess
the human health risks posed by
diesel emissions for a variety of
diesel engine use and emissions
control scenarios.
AMBIENT AIR
Collection and Measurement of Samples
DIESEL & OTHER PARTICULATE SOURCES
Collection and Measurement of Samples
GASOLINE
Collection and Measurement of Samples
Health Effects
Assessment
Particles
Extracts
Exposure
Assessment
Levels emitted
Human exposure
projections
Levels emitted
Human exposure
projections
Risk Assessment of
Ambient Environment
'
'
Risk Assessment of
Diesel Emissions
'
<
Risk Assessment of
Gasoline Emissions
J I
Assessment of Relative
Contribution of D,esel
Risks to Existing Risks
from Ambient Particles
1
. r
Assessment of Relative
Risks of Diesel and
Gasoline Emissions
Regulatory Decision
Mak ng for Diesel Vehicles
Figure 1.
Diesel emissions research and risk assessment strategy.
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fl)
to
>.
«
"55
0}
Animals
Plants
Insects
Mammalian Cells
Microorganisms
Test Substance
Whole Diesel
Emissions
m
m
m
o
o
Gaseous
Emissions
Only
O
0
0
o
o
Diesel
Particles
e
m
m
Diesel
Parti cu late
Extract
m
m
m
KeY: © Study or studies completed or under way
O Proposed or planned studies
Figure 2.
Diesel Emissions Research Program health effects studies.
At the same time, ORD is
conducting two parallel health
effects and exposure
assessments to generate risk
estimates for gasoline emissions
and the ambient air. By
comparing the risk assessment
for diesel emissions, gasoline
emissions, and ambient air, ORD
hopes to determine whether
diesel emissions will pose a
significantly greater human
health threat than the gasoline
emissions they will replace or the
pollutants already occurring in
ambient air.*
'Ideally, whole diesel and gasoline
emissions would be compared in
long-term animal inhalation experiments.
Unfortunately, experimental and
programmatic restraints preclude this
line of investigation at present. In the
meantime, ORD scientists hope to
compare the carcinogenic and mutagenic
potential of gasoline particles.
However, technical difficulties associated
with collecting gasoline particles for
biological experiments (see Collection
and Characterization of Particutate
Matter) may limit the amount of
comparison that can be done between
gasoline and diesel emissions.
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From Risk to Regulation
The health risk assessment
generated by ORD will be used by
the EPA to determine whether
and to what extent diesel
emissions should be regulated.
As a first step, the health risks
will be balanced against any
positive public health impacts
that may result from conversion
to diesel fuel. For instance, diesel
fuel is less flammable than
gasoline so that increased use of
diesel-powered cars may result in
fewer deaths or injuries from
accidents involving fire and
explosions. Also, since diesel
fuel is less volatile than gasoline,
the diesel fuel cycle (including
transportation and handling) will
probably result in less loading of
the atmosphere with precursors
of hazardous photochemical
oxidants than does the handling
of gasoline.
In deciding how to regulate
diesel emissions, the EPA will
weigh the potential health
impacts, the cost and
technological feasibility of
controlling diesel emissions, and
the general environmental and
economic impacts of any
proposed regulations. While
safeguarding public health will
be the primary concern,
economic and technological
considerations may determine
the optimum of a range of
regulations that are acceptable
from a public health standpoint.
/
1977
Particulate
collection and
characterization
Epidemiology
In vivo studies
In vitro studies
Ambient air
monitoring and
analysis
Exposure
Risk assessment
Control
technologies
development
/ 1978 / 1979 / 1980 / 1981 / 1962 /
1983
Critical review
Possible new study
Carcinogen! city and mutagenicity studies Noncarcinogenicity studies
*
Comparative study
Intratracheal instillation study
Long-term monitoring
„ _, ,. In-vehicle monitoring and mobility
Computer modelmg V, pamrn determination
cimy >
^^
Preliminary risk assessment
Updated risk
' assessment
Key
Research
commencement
date
Final report or
research end date
Diesel Emissions Research Program schedule.
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Collection and
Characterization of
Participate Matter
To determine the carcinogenic
and mutagenic potential of diesel
exhaust, ORD is conducting
extensive chemical and
biological testing of diesel
particles and the organic
chemicals associated with them.
Diesel particles are being
collected by the EPA's
Environmental Sciences
Research Laboratory in Research
Triangle Park (ESRL-RTP) and by
the Office of the Mobile Source
Air Pollution Control (OMSAPC)
in Ann Arbor, Michigan. These
samples are being prepared,
tested, and analyzed at the
Environmental Monitoring
Systems Laboratory in Research
Triangle Park (EMSL-RTP) to
determine which components of
diesel emissions are biologically
active (i.e., carcinogenic or
mutagenic) and to characterize
the fuel type, engine type, and
driving patterns that generate the
active components.
The process involved in
collecting and preparing
particles for use in health effects
experiments is illustrated in
Figure 3. Diesel exhaust is being
generated in the laboratory by
Figure. 3.
Preparation of particles and paniculate extract for experimental
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diesel engines attached to
dynamometers — devices that
"drive" the engines in a repetitive
series of idle, acceleration,
cruise, and deceleration modes
designed to approximate actual
driving patterns. Exhaust from
these engines is passed through
a dilution tunnel to simulate the
mixing with ambient air that
occurs in an actual use situation.
Jpon contact with the air, the
exhaust cools and the gaseous
organic chemicals present in the
exhaust condense and adsorb
onto the particles. After cooling
and mixing have occurred, the
particles are trapped on a filter
and removed. They can then be
used directly in biological (health
effects) tests or extracted with
chemical solvents which remove
certain portions (or fractions) of
the organic chemicals. Extracts
containing specific organic
fractions are used in both
biological testing and chemical
analysis.
ESRL-RTP and OMSAPC are
generating diesel particles and
parti culate extracts from several
different light-duty and
heavy-duty engines using a
variety of fuels and driving
cycles. These extracts are being
analyzed extensively at
EMSL-RTP and ESRL-RTP to
identify the chemical classes
present in diesel particles and to
investigate how the chemical
composition varies with engine
type, fuel type, and driving
patterns. ESRL-RTP is studying
theformation and aging of diesel
exhaust pollutants under
simulated atmospheric
conditions. Samples of aged
particles will be subjected to
chemical analysis and to
biological tests for carcinogenic
and mutagenic potential. Such
work will be useful in
determining whether diesel
exhaust becomes more or less
hazardous as it is changed by
such factors as dilution, sunlight,
and reactions with other
pollutants.
EMSL-RTP is also preparing
samples of cigarette smoke
condensate and extracts of
gasoline exhaust, roofing tar
fumes, and coke oven emissions
for a series of comparative
biological studies. In the case of
gasoline exhaust from
catalyst-equipped cars, the
particles are so dilute that
substantial collection time is
required to obtain sufficient
material for biological tests.
Unfortunately, this may limit the
amount of comparison that can
be done between gasoline and
diesel emissions, since the more
definitive long-term experiments
require large amounts of extract.
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Identification of the
Potential
Health Threats
Epidemiologies! Studies
Scientists have three basic
biological tools to assess the
human health risk posed by a
substance: epidemiological
studies, whole animal
experiments, and in vitro (in
glassware) tests using
microorganisms and individual
cells. As discussed in the
following sections, ORD is
utilizing all three methods in
order to provide a broad range of
information on the potential
health effects associated with
increasing use of the diesel
engine.
Epidemiological studies examine
the health and exposure histories
of specific population groups in
an attempt to correlate disease
patterns with exposure to a
chemical substance or other
disease-causing agent. The
populations studied are often
groups of workers that have been
occupationally exposed to the
substance of interest. !n the case
of diesel exhaust, several groups
have been identified as possible
candidates for epidemiological
study. These include miners in
underground operations where
diesel-powered equipment is
used, mechanics in diesel bus
and truck garages, diesel truck
drivers, and railroad workers
exposed to the diesel fumes of
locomotives.
Critical Literature Review. A
few diesel epidemiological
studies were conducted prior to
the Diesel Emissions Research
Program. These studies were
primarily concerned with how
diesel exhaust affects the
respiratory system. Although
several investigations found
associations between respiratory
disease and diesel exposure, the
majority of the studies did not
note adverse health effects i n the
study populations. However,
problems with the way in which
the studies were designed,
conducted, and reported make it
very difficult to draw firm
conclusions. The EPA's Health
Effects Research Laboratory in
Cincinnati, Ohio (HERL-Ci) is
presently conducting a
comprehensive review of all the
diesel epidemiology literature.
This review will analyze the
strengths and weaknesses of the
published studies and then
synthesize their findings so that a
better judgment can be made of
the human health risks posed by
diesel emissions.
New Studies. HERL-Ci also
plans to initiate its own
epidemiological study to
augment the existing data.
Feasibility studies are currently
under way to identify the most
appropriate populations for
study and to determine the most
useful study design. The two
possible studies that appear to
hold the most promise are a
historical cohort mortality study
and a case-control respiratory
cancer study.
In the historical cohort study, a
large group of individuals, such
as diesel mechanics, who had
received exposure to diesel
emissions at some time in the
past would be identified from
company or union records.
Mortality rates for the exposed
group would be computed and
the causes of death would be
compared with the general
population and other working
groups. Two key pieces of data —
exposure levels and smoking
habits — would have to be
projected from current
information. Exposure levels of
the study population would be
estimated by measuring the
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Animal Studies
10
current occupational exposure of
similar workers. The study
group's smoking habits would be
inferred from present day worker
trends. Information on smoking
histories would be necessary to
ensure that smoking did not
account for the health effects
observed in the study group.
Another epidemiological study
being considered is a
case-control study. In this type of
study, individuals are identified
who have had a specific disease
considered to be a possible
health effect from exposure to
the substance of interest. These
individuals are then matched
with an individual of the same
sex, age, and race who did not
suffer the disease, and the
histories of both individuals are
searched for evidence of
significant exposure to the
substance. The proposed diesel
exhaust case-control study
Health effects experiments in
which an organism is exposed to
a substance, such as diesel
particles, and then examined for
detrimental effects cannot be
performed on humans for
obvious ethical reasons. Animal
studies are therefore the closest
we can come to determining
experimentally how a substance
may affect the human organism.
They are an important
complement to epidemiological
studies which often provide only
limited information because of a
lack of available data.
would examine respiratory
cancer, since the potential of
diesel exhaust to cause this type
of cancer is a major concern.
Two approaches for the diesel
case-control study are being
examined. The first would make
use of the data that have been
collected in large lung cancer
case-control studies, such as
those currently underway in the
United States and Europe. The
fact that diesel engines are more
prevalent in Europe than in the
United States may increase the
probability of identifying
individuals who have had
significant exposure to diesel
exhaust. The second approach
would be to conduct the study
within an industry where a variety
of exposures exists. The study
would attempt to discern
whether groups that received
higher exposures to diesel
exhaust have an increased risk of
lung cancer.
Animal studies are particularly
useful for providing
dose-response data, that is,
information on how a
substance's effect varies with the
level of exposure. Often the
doses administered in animal
experiments are much higher
than environmental exposure
levels to increase the likelihood
of observing an effect, if one
exists. The dose-response data
must then be extrapolated down
to lower environmental levels of
exposure in order to determine
"safe" levels for human
exposure (See Risk Assessment
for a discussion of the extra-
polation policy).
Cancer and Related Effects.
The carcinogenic and mutagenic
potentials of diesel emissions,
particles and particulate extracts
are being examined in at least 18
separate studies using mice, rats,
rabbits and hamsters (Table 1).
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Table 1
Mammalian Studies to Investigate the Carcinogenic, Mutagenic, and Teratogenic Potential of
Diesel Exhaust
11
Type of Study
Carcinogenicity
Carcinogenicity
Effects on
metabolism of
benzo(a) pyrene
[B(a)P], a known
carcinogen present in
diesel exhaust
Carcinogenicity
Carcinogenicity
Carcinogenicity
and mutagenicity
Carcinogenicity
and mutagenicity
Mutagenicity
Mutagenicity
(cytogenetic
study)
Mutagenicity
Mutagenicity
Mutagenicity
(dominant lethal
test in males)
Mutagenicity
(transport to
testes)
Mutagenicity
(dominant lethal
test in females)
Mutagenicity
(total reproductive
capacity in females)
Mutagenicity
(heritable
translocation
test)
Mutagenicity
(specific locus
test)
Teratogenicity
(birth defects)
1
i
Route of Test
Administration Animal
Inhalation Rats
Syrian
hamsters
" Mice
" Sen car
mice
Intratracheal Hamsters
instillation
Inhalation Strain A
mice
" Mice
"
" Syrian
hamsters
" Mice
" Syrian
hamsters
" Mice
" "
" "
"
" "
Rats and
rabbits
Biological
Endpoint
Transformed
liver cells
Cancer,
particularly
of the lungs
Distribution
and quantitation
of B(a)P
metabolites in
lung, liver and
testes
Skin tumor
formation
Respiratory
tract cancer
Lung cancer;
sperm
abnormalities
Chromosomal
abnormalities in
lymph cells
The ability of
urine of exposed
mice to cause
mutations in
bacteria
Chromosomal
damage
Heritable
defects and
egg abnormalities
Aberrations in
lung cells and
chromosomes
Dominant
lethal mutations
as shown by
increased fetal
death
Microscopically
observable
changes in
sperm structure
Dominant lethal
mutations as
shown by
increased
fetal death
Changes in
litter size
Partial and
complete
sterility;
chromosomal
abnormalities
Morphological
mutation (change
in skin color
and ear shape)
Skeletal and
soft tissue
abnormalities in
fetuses
Substances
Tested
Whole diesel
exhaust
"
..
••
Diesel particles,
diesel paniculate
extract
Whole diesel
exhaust
"
"
Diesel particles
Whole diesel
exhaust
Whole diesel
exhaust and
particles
Whole diesel
exhaust
"
"
"
-,
"
..
Laboratory
Perform-
ing Study
HERL- Ci
"
„
-
Illinois Institute
of Technology
Research Instiiute
for HERL-RTP
HERL-Ci
,,
"
"
"
• •
Oak Ridge
National
Laboratory
(ORNL) for
HERL-RTP
"
"
"
,,
"
HERL- Q
Study
Status/
Results
Results
available
9/79
Results
available
6/81
Results
available
9/80
Results
available
early 1981
Results
available
First results
available
12/79
Resu Its
available
12/79
First results
available
12/79
Results
available
12/79
Results
available
12/79
Results
available
12/79
Fetal death
not increased
No noticeable
effects
Increased
germ cell
killing and
fetal death
Results
available
11/79
Results
available
1/80
Results
available
2/80
No abnormalities
observed in
rats or rabbits
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12
The studies vary in the route of
exposure used (Figure 4), the
dose levels administered, and the
biological endpoints (effects)
being investigated. Each study is
designed to provide a different
perspective on the ability of
diesel emissions to cause cancer
or mutations. Several
comparative studies are also
being conducted to determine
the carcinogenic potential of
diesel particles relative to known
human carcinogens.
Cancer Studies. In many of the
cancer studies, the animals are
being exposed to diesel exhaust
through inhalation. This work is
being done at the EPA's Health
Effects Research Laboratory in
Cincinnati, Ohio, where a special
exposure facility has been built
for the inhalation experiments
(Figure 5). The animals are being
exposed to diesel exhaust
generated by a light-duty diesel
engine attached to a
dynamometer. As with the
particulate collection, the
dynamometer is programmed to
drive the engine in a manner that
simulates actual driving patterns.
The resulting exhaust is diluted
with purified air and shunted into
the animal exposure chambers
where it is monitored for
concentrations of particles and
gases.
Diesel Exhaust
Diesel Particles
Diesel Particulate
Extract
Gasoline Exhaust
GPE
RTV. CSC. COE
KEY
GPE = Gasoline particulate extract
RTV = Roofing tar volatiles extract
CSC = Cigarette smoke condensate
COE = Coke oven emissions extract
Inhalation
Skin Intraperitoneal Intratracheal
Painting Injection Instillation
© Work in progress
O Proposed study
^t Test organisms are insects
Figure 4.
Exposure methods and test substances for the Diesel Emissions Research Program
whole animal studies.
-------
13
Figure 5.
Exposure chambers for inhalation experiments.
Animals in the carcinogenicity
inhalation experiments are being
examined for a variety of
biological effects indicative of
carcinogenic potential, including
lung and skin tumors and
cancerous-like changes in
individual cells of exposed
animals. Inhalation studies are
limited, however, in the size of
the dose that can be given to the
animals. High concentrations of
the test substance may cause
short-term toxic effects that
adversely affect the animal
before long-term effects such as
cancer can appear. Because of
this limitation, the cumulative
dose received during the
inhalation exposure period is
often not sufficient to elicit
cancer, even when the substance
administered is a known
carcinogen. To counteract this
problem, several of HERL-Ci's
carcinogenicity inhalation
studies are making use of
innovative techniques that
increase the chance of detecting
a carcinogen. For instance, some
studies are using special strains
of animals that are highly
tumor-prone. Others are treating
the test animals with chemicals
to enhance the development of
an effect within the animals'
lifetime or the test period.
-------
Intratracheal instillation
Figure 6.
Administration of diesel particles to hamsters by intratracheal instillation.
(Photographs courtesy of Mr. Alan Sftefner. Illinois Institute for Technology Research Institute. Chicago. Illinois)
14
To examine the effects that may
occur at higher levels of
exposure than are possible in
inhalation experiments, a study is
being performed using the
intratracheal instillation route of
exposure in which concentrated
doses of diesel particles or
extract are directly applied to the
respiratory tract of the test
animals (Figure 6). The
intratracheal instillation study is
an important complement to the
inhalation experiments because
it increases the probability of
observing an effect as well as
reduces the amount of time
necessary for the effect to
appear. Using this technique,
researchers may be able to
obtain meaningful results in a
period of months rather than
years.
-------
Mutation Studies. A mutation is
a permanent change in a cell's
DMA, the genetic material that
directs the reproduction and
development of an organism.
Mutation may occur in both
nonreproductive (somatic) and
reproductive (germ) cells. When
a mutation occurs in the DMA of
germ (i.e., sperm or egg) cells,
nonviable or mutant offspring
may result. To identify mutagenic
substances, scientists can either
examine the offspring of exposed
animals for mutants, or they can
look at the individual somatic or
germ cells of exposed organisms
for signs of DNA damage (Figure
7). (This latter approach is the
basis for the in vitro mutagenicity
tests described under In Vitro
Studies.) ORD is using both
experimental approaches in a
series of animal studies being
conducted by HERL-Ci and by
the Oak Ridge National
Laboratory (ORNL) in Oak Ridge,
Tennessee for HERL-RTP to
investigate the mutagenic
potential of diesel emissions.
At HERL-Ci, individual somatic
cells, eggs, and sperm of animals
exposed to diesel exhaust
through inhalation are being
examined for signs of genetic
damage or abnormalities that
could lead to the occurrence of
mutations affecting future
generations. At Oak Ridge,
exposed animals are being bred
to see whether they produce any
mutant offspring. For instance, in
the specific locus test, scientists
expose a special strain of
Exposure to chemical, radiation or
other mutation-causing agent
Somatic (nonreproductive) cells
Examine somatic cells for signs
of genetic damage
Examine offspring for mutation
(e.g., patchy skin color)
Examine germ cells for
signs of genetic damage
15
Figure 7.
Approaches for detecting mutagenic substances.
-------
Figure 8.
Normal (dark) and mutant (dark and light) offspring of mice exposed to a mutagen in the
specific locus test. Patchy skin is one of several specific types of mutation that may
occur when this strain of mice is exposed to a mutagen.
(Photograph courtesy of Or- Walderico Generoso. Oak Ridge National Laboratory. Oak Ridge. Tennessee}
16
mutation-sensitive mice to diesel
emissions and then examine
their offspring for patchy skin
color (Figure 8) and abnormally
shaped ears. Other studies at
ORNL will look for sterility of
exposed animals, changes in
litter size, and increased fetal
death.
Teratogenicity Studies.
Teratogenic effects, more
commonly known as birth
defects, are any effects which
result from damage to the fetus.
Like mutation and cancer,
teratogenic studies are believed
to result from damage to a
cell's genetic material. To
examine diesel exhaust's
teratogenic potential, HERL-Ci
scientists have been exposing
pregnant rats and rabbits to
diesel exhaust through inhalation
and then examining the exposed
animals for impaired
reproductive performance and
their offspring for birth defects.
So far, no abnormalities have
been observed.
Comparative Studies. One
method of evaluating the
cancer- or mutation-causing
ability of a substance is to
compare its performance in a
series of tests with the
performance of other chemicals
whose potency is already known.
The Diesel Emissions Research
Program is pursuing this strategy,
by comparing diesel emissions to
other substances — cigarette
smoke, roofing tar fumes, and
coke oven emissions — whose
human carcinogenic potential
has been determined from
previous epidemiological
studies. Three comparative
-------
Table 2 Comparative Studies for Carcinogenicity and Mutagenicity
Route of
Type of Study Administration
Carcinogenicity:
a) Initiation Skin
painting
b) Promotion
c) Cocarcinogenesis
d) Complete "
carcinogenesis
Carcinogenicity Intraperitoneal
injection
Carcinogenicity Intratracheal
instillation
Mutagenicity Inhalation
(whole-body
exposure)
'Key: DPE = Diesel particulate extract
CSC = Cigarette smoke condensate
RTV = Roofing tar volatiles extract
COE = Coke oven emissions extract
GPE = Gasoline particulate extract
B(a)P = Benzo(a)pyrene
7
Laboratory Study
Test Biological Substances Perform- Status/
Animal Endpoint Tested' ing Study Results
Mice Skin tumors, DPE from three Oak Ridge Papilloma results
both malignant engines, CSC, National available 2/80-
(carcinoma) and RTV, COE, GPE, Laboratory for carcinoma results
nonmalignant B(a)P HERL-RTP available early
(papHloma) 1931
DPE from three " Carcinoma results
engines, CSC, available early
RTV, COE, B(a)P 1981
Carcinoma results
available early
1981
"
Results available
early 1981
Strain A Lung cancer DPE, CSC, RTV, HERL-Ci Results available
mice B(a)P 3/80
Hamsters Respiratory DP, DPE, CSC, Illinois Institute Results available
tract cancer RTV, B(a)P, and for Technology early 1980
possibly GPE Research Institute
for HERL-RTP
Fruit Mutation Whole diesel - Oak Ridge Results available
flies exhaust, National early 1980
gaseous diesel Laboratory
emissions, for HERL-RTP
gasoline exhaust
cancer studies are being Ideally, gasoline exhaust would
conducted (Table 2): one using also be evaluated in comparative
the intratracheal instillation experiments to determine
exposure technique, another in whether diesel exhaust is more
which the substances are or less carcinogenic than the
injected into the abdominal gasoline exhaust it will replace.
cavity (a technique known as Unfortunately, the problems
intraperitoneal injection), and a associated with obtaining
third study in which the extracts sufficient amounts of gasoline
are applied directly to the skin of particulateextractforafull range
mice (skin painting). of comparative whole animal
cancer experiments may
preclude this line of
The latter study, known as a skin investigation. Enough extract
tumorigenesis study, will look nas been obtained, however, to
for the formation of both benign conduct a skin initiation study in
and malignant (cancerous) mice- ln tnis study, extract is
tumors on the skin of exposed painted on the skin once,
mice (Figure 9). The followed by repeated application
study includes several
experiments to examine whether
diesel particulate extract can act
as a complete carcinogen,
whether it requires the presence
of another substance to exert a
carcinogenic effect (promoter or
initiator), or whether it can
augment the carcinogenic effect
of another (cocarcinogen)
chemical (Figure 10).
-------
Figure 9.
Skin tumors on mice treated with a known carcinogen. The smaller nodules on the
righthand mouse are benign tumors. The larger nodules present on the center and
left hand mouse are cancerous. HERL-RTP's skin painting studies will look for similar
effects on mice treated with diesel particulate extract.
(Photograph courtesy of Dr. Thomas Slags, Oak Ridge National Laboratory. Oak Ridge, Tennessee)
COMPLETE CARCINOGEN
Multiple application of
a complete carcinogen
No added treatment
->- Tumors
INITIATOR and PROMOTER
Initiator
Subsequent treatment with promoter
Tumors
Note: An initiator or promoter acting alone will not produce tumors.
COCARCINOGEN
Simultaneous treatment
with initiator & cocarcinogen
Subsequent treatment with promoter
>• Greater or
more rapid appearance
of tumors than without
cocarcinogen
18
Figure 10.
Testing protocols for complete carcinogens, tumor initiators, tumor promoters and
cocarcinogens.
-------
of a chemical that is known to
promote tumor formation. The
study will compare the relative
ability of gasoline and diesel
extracts to act as tumor initiators
— that is, to cause irreversible
cellular damage capable of
developing into tumors in the
presence of a tumor promoter.
A comparative study exposing
fruit flies to whole diesel and
gasoline exhaust will also be
conducted to compare the ability
of diesel and gasoline emissions
to cause mutations. This
relatively rapid test will be used
to provide a preliminary idea of
whether diesel exhaust is more
or less mutagenic than gasoline
exhaust.
Noncarcinogenic Effects.
Noncarcinogenic effects of
combustion emissions (such as
chronic lung diseases) are
generally caused by combustion
gases, such as sulfur dioxide and
nitrogen oxide, and by the
particles with or without
associated organic matter. These
components are present in both
gasoline and diesel exhaust. The
replacement of gasoline by diesel
emissions is therefore not
expected to cause new or
unusual noncarcinogenic human
health effects. To test this
hypothesis, and to determine the
range and magnitude of diesel's
noncarcinogenic effects,
scientists at the EPA's Health
Effects Research Laboratory in
Cincinnati, Ohio are conducting
a series of noncarcinogenic
health effects studies.
study conducted prior to the
Diesel Emissions Research
Program had shown that diesel
exhaust is capable of causing
serious damage to respiratory
tissue in hamsters. The questions
that remain to be answered are:
What sort of damage will diesel
exhaust cause, and under what
exposure conditions will diesel
exhaust harm human respiratory
tissues?
In 1977, HERL-Ci conducted a
50-day pilot study to survey the
potential noncarcinogenic health
effects of diesel exhaust. These
experiments exposed cats, rats,
mice and guinea pigs to relatively
high concentrations of exhaust
through inhalation for a few days
or weeks. Animals were then
examined for a variety of
short-term effects including lung
damage, increased susceptibility
to infection, biochemical
changes in the lung and other
tissues, signs of fibrosis and
emphysema, changes in
behavior, and the ability of the
lungs to clear away particles. The
only short-term effects observed
were increased susceptibility to
infection and some behavioral
alterations in exposed rats.
19
The noncarcinogenic effect of
greatest concern is the ability of
diesel exhaust to cause chronic
lung diseases such as pulmonary
fibrosis and emphysema. Many
combustion products, including
gasoline emissions, are known to
cause lung damage, and there is
little question that diesel
exhaust, if inhaled in sufficient
concentration over a long
enough period of time, would
have a similar effect. In fact, one
-------
To follow up this study, HERL-Ci
is conducting a series of
inhalation experiments (Table 3)
to examine various types of
noncarcinogenic damage that
may occur in animals exposed to
diesel exhaust for extended
periods of time. These studies
include:
• Long-term studies in cats and
mice to look for various types
of structural, chemical, and
functional lung damage
• Neurobehavioral studies to
investigate effects on the
nervous system and behavioral
developments
• A series of experiments to
determine the degree to which
diesel exhaust impairs an
animal's resistance to
infection.
Some of these studies have been
completed. The neurobehavioral
studies have shown that rats
exposed to diesel emissions are
less active than normal and that
diesel emissions may delay
development in young animals.
In the infectivity study, resistance
to infection was found to be
impaired in exposed mice,
confirming the preliminary
results obtained in the pilot
study. Unfortunately, it is not
easy to extrapolate
dose-response data for
noncarcinogenic effects down
from the relatively high doses
used in these studies to the much
lower environmental exposure
levels. Nevertheless, the studies
are valuable for identifying
possible health effects of
concern.
Table 3 Mammalian Studies to Investigate the Noncarcinogenic Effects of Diesel Exhaust
Type of Study
Neuro-
behavioral
Infectivity
Reproduction
(multigeneration)
Lung damage
Lung function
Lung deposition,
retention, and
Hoaranrp
Laboratory
Route of Test Biological Substances Perform-
Ad ministration Animal Endpoint Tested ing Study
Inhalation Newborn Neurobehavioral Whole diesel HERL-Ci
and adult abnormalities exhaust
rats
Mice Impaired
resistance to
infection
Effects on
fertility and
other aspects of
reproduction and
development
Effects on
lung cells
Cats Noncarcinogenic
lung disease;
sperm
abnormalities
Hamsters Body and Carbonaceous HERL-RTP
organ burdens particles
of diesel exhaust (diesel surrogate)
Study
Status/
Results
Reduced activity
and possibly
delayed
development in
exposed animals
Impaired
resistance to
infection
observed in
exposed animals
Results
available
10/80
Results
available
9/79
Results
available
11/80
Study
proposed
for funding
20
-------
60 days post-exposure
One-hour post-exposure
Figure 11.
Clearance of diesel particles from lung tissue. Hamsters were treated with a single dose
of diesel particles by intratracheal instillation and then sacrificed either one hour or
60 days after treatment. The proposed deposition, retention, and clearance study would
investigate similar phenomena in animais exposed to particles through inhalation.
(Photographs courtesy of Mr. A/an Shefner, Illinois Institute for Technology Research Institute. Chicago, Illinois)
21
One other noncarcinogenicity
study, proposed by HERL-RTP, is
being considered for funding.
This study would investigate the
deposition, retention, and
clearance (Figure 11) of particles
in the lungs of animals exposed
through inhalation. Specifically,
the study would attempt to
answer such questions as:
• What concentration of
particles will overload an
animal's natural defense and
clearance mechanisms thus
making the animal more
susceptible to disease ?
• What happens to the organics
associated with the inhaled
particles? For instance, how
fast do they enter the blood
stream? At what site(s) in the
body do they tend to
accumulate? How fast can
they be cleared away after
termination of exposure?
-------
In Vitro Studies
22
In vitro tests (Figure 12) detect
the ability of a chemical to alter
the genetic material (DNA) of
simple organisms (bacteria,
yeast) or mammalian cells
(human or animal). In humans,
genetic alterations may cause
mutation, birth defects, and
possibly cancer. Since simple
organisms or single cells do not
have the biological complexity
of the human body, positive
in vitro tests are currently
considered to be suggestive but
not definitive evidence that a
chemical is carcinogenic or
mutagenic to humans.
In vitro tests are rapid and
inexpensive compared to animal
tests and epidemiological
studies. They are most commonly
used as rapid screening devices
to provide a preliminary idea of a
chemical's mutagenic or
carcinogenic potential until more
conclusive animal or
epidemiological studies can be
conducted. In vitro tests are also
valuable in cases where animal
tests simply cannot be
conducted; for instance, when
the number of substances to be
tested is so large that animal
tests would be prohibitively
expensive, or when not enough
of the test substance is available
to conduct a whole animal test.
Testing for Carcinogenic and
Mutagenic Potential. At the
beginning of the Diesel
Emissions Research Program,
diesel particulate extract was
tested in the Ames test (Figure
13), a well known in vitro test for
mutagenicity. The Ames test uses
TEST SYSTEM
CONTROL
Apply substance of
interest to microorganism
or cell system
Use same microorganism
or cells as test system but
do not add chemical
Figure 12.
Basic in vitro test procedure.
-------
a special strain of bacteria that
will not grow unless they have
been mutated. Bacteria exposed
to diesel extract in the Ames test
did grow, indicating that diesel
exhaust was potentially
mutagenic and possibly
carcinogenic* to humans. To
support this finding, scientists at
the EPA's Health Effects
Research Laboratory in Research
Triangle Park (HERL-RTP) are
examining diesel particles and
particulate extract in a battery of
in vitro tests (or assays) using
human and mammalian cells
{Table 4). Whole and gaseous
(particle-free) emissions are also
Figure 13.
Counting bacterial colonies in the Ames
test.
'Mutation involves damage to a cell's
DNA. Cancer is also believed to result
1rorn damage to a cell's DNA, so
chemicals that are mutagenic are
generally suspected of being
carcinogenic.
Table 4 In Vitro Tests to Determine the Carcinogenic and Mutagenic Potential of Diesel Emissions*
Type of Study
Carcinogenesis
Carcinogenesis
Mutagenesis
Mutagenesis
(Ames test)
Mutagenesis
Mutagenesis
Mutagenesis
Test
Organism
or Cells
Embryonic Syrian
hamster cells
Mouse cells
(BALBc3T3
fibroblasts) and
embryonic Syrian
hamster cells
Chinese hamster
ovary cells
Bacteria
(Salmonella
typhimurium)
Mouse cells
(L5178Y lymphoma
cells and BALBc3T3
fibroblasts)
Yeast
(Saccharomyces
cerevisiae D3)
Humal cells
(lymphocytes)
Biological
Endpoint
Viral enhancement
of oncogenic
transformation
Oncogenic
transformation
Chromosomal damage
(sister chromatid
exchange)
Gene mutation
Gene mutation
DNA damage
(mitotic
recombination)
Chromosomal damage
Laboratory
Performing
Study
Northrop Services,
Inc. for HERL-RTP
Microbiological
Associates and
Northrop Services,
Inc. for HERL-RTP
Northrop Services,
Inc. for HERL-RTP
HERL-RTP
SRI, International
and Microbiological
Associates for
HERL-RTP
North Carolina
State University
for HERL-RTP
Study
Status/
Results
Results available
late 1979
Results available
early 1980
Results available
late 1979
Results available
late 1979
Results available
late 1979
Results available
late 1979
Results available
1980
* The following substances are being tested in the in vitro tests: diesel particles and diesel particulate extract from five diesel engines; coke oven
emissions extract; cigarette smoke condensate; roofing tar volatiles extract and gasoline particulate extract.
23
-------
A.
Figure 14.
Oncogenic transformation assay. A. Positive response. Following exposure to a test
substance, three cells on the petri plate became transformed and spread in a cancerous-
(ike growth, indicating that the test substance may be carcinogenic. B. Negative
response. Exposure to a second test substance had no effect on the cells on the petri
plate, suggesting that the second test substance may not have carcinogenic properties.
C, Scanning electron micrograph of transformed cells (2000x). D. Scanning electron
micrograph of normal cells (3000x).
(Scanning Electron Micrographs courtesy of Dr. K. Muse, Department of Zoology, North Caroline State University
Rtteigk, NCI
scheduled for testing. The test
battery will look for the potential
of diesel emissions to cause
several different types of genetic
alterations, including:
• Gene mutation
• DMA damage
• Chromosomal alterations
• Oncogenic transformation, or
cancerous-like changes
(Figure 14).
Resu Its of these tests will provide
a preliminary idea of diesel's
mutagenicand carcinogenic
potential until results of the
long-term animal studies become
available. In vitro tests will also
enable HERL-RTP scientists to
characterize the type(s) of
genetic effects that diesel
exhaust is capable of causing at
the cellular level.
24
-------
Preparations are underway to
examine whole, gaseous, and
participate emissions from
gasoline engines in the same
battery of tests to compare the
carcinogenic and mutagenic
potential of diesel and gasoline
emissions.
Relative Potency Ranking. In
another line of research,
HERL-RTP scientists are
investigating the use of in vitro
tests for ranking various
substances with respect to
carcinogenic potency.* Extracts
from five different diesel engines
and three known carcinogens
(cigarette smoke, roofing tar
fumes, and coke oven emissions)
are being tested in the battery of
in vitro tests and in the whole
animal skin painting tests
described earlier (see Cancer
and Related Effects). HERL-RTP
scientists will attempt to
determine whether there is a
consistent pattern of activity in
the in vitro and the more
definitive skin painting tests. For
instance: Does the substance
that shows least activity in the/'/7
vitro tests also cause the fewest
skin tumors?
If an in vitro test appears to be a
fairly accurate potency indicator,
it may be used in the Diesel
Emissions Research Program to
provide a rapid estimate of
relative potency when time or
cost constraints do not permit
more extensive testing. For
instance, by examining particles
trapped by the various control
devices being developed (see
Control Technologies), the test
could provide rapid assessment
as to which technologies are
most successful in reducing
hazardous emissions.
25
*At present, in vitro tests are only used as
yes/no indicators of mutagenic and
carcinogenic potential. Although the level
of biological activity observed (for
instance, the number of bacteria that
mutate) varies with the substance being
tested, scientists do not yet know whether
the level of activity correlates with
mutagenic or carcinogenic potency.
Streamlining Chemical Analysis.
In another innovative line of
research, the Ames test is being
used to help identify specific
hazardous chemicals in diesel
particulate extract. Normally, the
chemical analysis of a complex
mixture containing thousands of
chemicals is an expensive and
time-consuming procedure. The
substance must first be divided
into a large number of distinct
fractions, each of which must
then be analyzed separately for
its individual chemical
components. To simplify this
process, HERL-RTP is using the
Ames test as a rapid screening
tool to indicate which of the
fractions should receive highest
priority for chemical analysis.
As a first step in this research,
diesel extract was divided into
seven fractions by scientists at
the EPA's Environmental
Sciences Research Laboratory in
Research Triangle Park. Each
fraction was then tested in the
Ames test for mutagenic
potential. Mutagenic fractions
were further divided and the
resulting subfractions were
tested in the Ames test. By
repeating this process, ORD
scientists hope to isolate the
most hazardous elements of
diesel extract. Once the
subfractions reach a manageable
size, they will be chemically
analyzed for specific toxic
chemicals.
Hazardous subfractions are
important since they may be the
subject of specific regulatory
action. For instance, in
establishing regulations for
controlling diesel emissions, the
EPA may set forth standard
procedures for fractionating
diesel particulate extract, and
then require that the
carcinogenic potential and
toxicity of specific subfractions
generated by these procedures
be reduced or eliminated in
controlled emissions.
-------
Air Monitoring Studies
26
The Diesel Emissions Research
Program is funding two studies
to monitor and analyze diesel
emissions in the ambient air. This
research is being performed by
the EPA's Environmental
Monitoring Systems Laboratory
in Research Triangle Park
(EMSL-RTP). One short-term
study will compare the risk from
diesel emissions to health risks
posed by pollutants already
present in ambient air. The other,
a long-term monitoring study,
will determine how air quality is
affected by an increasing use of
the diesel engine.
SAMPLING
J
42nd St
Outside bus
terminal
(Ambient diesel jevels)
41st St
New York Port
Authority Bus
Terminal (High
diesel levels)
ANALYSIS
Biological Tests
In vitro test
• Particulate extract
Tradescantia test
• Whole and gaseous
(particle-free)
emissions
Skin painting
• Particulate extract
Chemical Analysis
Particulate extract
Whole and gaseous
emissions
Figure 15.
Comparing air from areas of high and
ambient diesel emission levels.
Comparative Study. In the
short-term study, whole air,
gaseous (particle-free), and
particulate samples were taken
from areas with expected high
and ambient concentrations of
diesel emissions. The high level
samples were collected over a
15-day period from inside the
New York Port Authority Bus
Terminal. This site has high
diesel levels due to the constant
flow of buses, but is relatively
free of gasoline and other
exhausts. Ambient concentration
samples were taken from a site
near the terminal. The particulate
samples were collected using
massive-volume air samplers.
Only recently developed, these
samplers are unique in their
ability to separate the collected
particles into various size ranges.
Particulate extracts from both
sites are being compared in a
series of chemical and biological
tests (Figure 15). Chemical
analysis will identify known
carcinogens and mutagens,
while in vitro tests will examine
the carcinogenic and mutagenic
potential of the extracts. Animal
(skin) painting tests may be
conducted if a sufficient sample
is available, pf particular interest
will be the biological and
chemical characteristics of the
smaller-sized (respirable)
particles.
Whole and gaseous samples
from the two sites are also being
subjected to chemical analysis to
identify organic chemicals and
other gaseous components
present in diesel emissions. In
addition, the biological activity of
these samples is being examined
in a recently developed
mutagenicity test for gaseous
substances. This unusual test
utilizes the plant Tradescantia
(commonly known as
spiderwort), whose flower petals
and stamen hair cells turn from
blue to pink following contact
with gaseous mutagens. To
conduct this test, a mobile
laboratory (Figure 16} was used so
-------
Mobile laboratory for on-site testing of
ambient air
Exposure chamber inside the mobile
laboratory.
Tradescantia flower
Normal (darker) and mutant (lighter)
stamen hair cells
Figure 16.
Tradescantia mutagenicity test.
(Photographs courtesy of Mr. Lloyd Schairer. Brookhaven National Laboratory. Brookhaven. New York)
27
plants could be directly exposed to
ambient air at both sampling sites.
By counting the number of stamen
hair cells that change color
following exposure, scientists will
be able to rapidly determine the
mutagenic potential of the test
substances.
Results of this short-term study
will be used in assessing whether
high ambient concentrations of
diesel pollutants pose a greater
human health hazard than
pollutants present in ambient air
in a major metropolitan area.
Also, data on the air samples
taken within the Port Authority
Terminal will aid in determining
potential health effects of
"worse-case" ambient exposure.
Long-Term Monitoring.
EMSL-RTP's long-term air
monitoring study is designed to
monitor the change in air quality
that will take place during the
next few years as large numbers
of New York City taxicabs convert
from gasoline to diesel engines.
Diesel conversion of taxicabs is
expected to have a measurable
impact on local diesel pollutant
levels because taxicabs account
for approximately one-third of
the passenger miles driven in
Manhattan. In this study, air
samples from a site in New York
City's Central Park will be
collected at 3-month intervals for
3 years and tested in In vitro and
possibly skin painting tests for
mutagenic and carcinogenic
potential. Like the short-term
study, this project will be used in
estimating whether the change
from gasoline to diesel fuel will
pose a greater human health
threat than ambient air now
present in New York City. It will
also provide baseline data
against which to compare any
future changes in air pollutant
levels.
-------
Exposure
Exposure information is essential
for assessing the overall public
health impact of widespread
introduction of diesel cars.
Human population exposure to
air pollutants can either be
directly measured using portable
sampling devices or estimated
using complex computer models
(Figure 17). Computer models
combine information on such
factors as vehicle types, number
of miles travelled, emissions
characteristics, roadway
configurations, and directly
measured pollutant
concentrations to predict
pollutant levels as a function of
distance from the pollution
sources. Ideally, data on the
average proximity of the U.S.
population with respect to the
pollution sources would then be
worked into the computer model
to project the number of
individuals that will be exposed
to various levels of pollutants.
Computer Modeling of Pollutant
Levels. As part of the Diesel
Emissions Research Program,
scientists at the EPA's
Environmental Sciences
Research Laboratory in Research
Triangle Park are using existing
computer models to project how
diesel conversion of motor
vehicles will affect the levels of
various pollutants in five U.S.
cities— New York, St. Louis,
Kansas City, Phoenix, and Los
Angeles. Future pollutant levels
are being predicted for a range of
diesel particulate control
scenarios. Where possible,
projections will be tested against
ambient air quality
measurements in order to verify
the accuracy of the various
models. The program's ambient
air monitoring studies will
contribute to this work by
establishing a baseline against
which future particle levels can
be compared as diesel cars are
introduced.
Emissions characteristics
Roadway configurations
Number of vehicles
Types of vehicles
Average number of miles travelled
Weather data
Population activity patterns
Pollutant levels with respect to
distance from traffic arteries and
other diesel emissions sources
Exposure projections
Diesel Pollutant Levels
Figure 17.
Computer modeling of human population exposure to diesel emissions.
28
-------
Meter showing
instantaneous
carbon monoxide
level
' Digital display of cumulative exposure
'Strip chart with permanent record of pollutant concentration
Figure 18.
Portable monitor to measure individual exposure to carbon monoxide.
Research to Help Estimate
Population Exposure. At the
EPA's Environmental Monitoring
Systems Laboratory in Research
Triangle Park, scientists are
working to define patterns in
population activities (e.g., work,
recreation, commuting) so that
they can generate more precise
population exposure data. In
order to broaden our knowledge
about pollutant exposure,
EMSL-RTP scientists are also
conducting a study to measure
individual exposure to carbon
monoxide, one of the gases
present in diesel and other
vehicular emissions. This study is
utilizing personal monitors
attached to passengers in buses
and cars, and portable monitors
placed inside the vehicles (Figure
18). Passengers are generally
subjected to higher pollutant
levels than pedestrians, so the
data generated will provide an
idea of worst-case general
exposure to carbon monoxide.
Portable carbon monoxide
monitors may also prove useful
for estimating individual
exposure to diesel particles if
research indicates that ambient
diesel particle levels correlate
with ambient carbon monoxide
levels. Commercial companies
are currently developing portable
monitors for directly measuring
individual exposure to diesel
particles. If suitable, these
instruments may be used by
EMSL-RTP in future exposure
studies.
29
-------
Risk Assessment
Ultimately, the human health
effects and exposure data
generated by the Diesel
Emissions Research Program
will be combined to assess the
public health risk associated with
diesel exhaust—a process known
as risk assessment (Figure 19).
The estimated risk will then be
used by the EPA along with other
important factors in deciding
how stringently to regulate diesel
emissions. Risk assessment will
be performed by the EPA's Office
of Health and Environmental
Assessment (OHEA) in
Washington, D.C.
In assessing diesel's
noncarcinogenic health risk,
OHEA will draw heavily upon
previous experience with other
atmospheric pollutants. The
noncarcinogenic effects of
combustion gases have been
well studied, and there is good
reason to believe that diesel
exhaust will have similar effects.
To establish the carcinogenic
risk of diesel exhaust, diesel
particles and paniculate extract
are being examined in animal
studies (see Identification of
Potential Health Threats). These
studies will generate information
on how the likelihood of
developing cancer varies with
dose. However, because the
doses used in animal
experiments are generally much
higher than actually occur in the
ambient environment, the
dose-response data from these
experiments must be
extrapolated downward in order
to predict the increased
incidence of cancer that could
occur in human populations
exposed to lower environmental
levels of diesel pollutants.
30
QUANTIFICATION OF
HEALTH EFFECTS
QUANTIFICATION OF
EXPOSURE
Identify health effect
of concern
I
Define the nature and degree
of the effect at different
doses (dose-response)
Determine who is exposed
Determine the level(s)
of exposure
Estimate the level of
occurrence of effects on
the population
Figure 19.
The risk assessment process.
-------
i
LINEAR THRESHOLD LINEAR NONTHRERHOI n
^
ence of Cancer
T3
c
D)
1
(1
C
t
0)
o
c
The lowest dose at Q
which no effect occurs -g
is greater than zero
x -c
- u>
' j» °
Effect may occur
at any dose greater
than zero
/X
fc'
Figure 20.
The threshold concept.
In extrapolating the
dose-response data to
low-exposure levels, the EPA's
current policy is to use a linear
nonthreshold dose-response
relationship. This relationship
assumes that exposure to even
extremely low doses of a
substance can potentially result
in cancer (Figure 20). Such a
relationship is considered to be
conservative because it probably
overestimates cancer incidence
at low exposures. It is the EPA's
cancer assessment policy to use
such an extrapolation in the
absence of better information
because of its conservative
nature.
To assist the linear nonthreshold
extrapolation of risk, the relative
carcinogenic risk of diesel
exhaust will be determined as
discussed in the Program
Strategy section by comparing
them vitro and in vivo activity of
diesel exhaust to carcinogenic
agents — coke oven emissions,
roofing tar fumes, and cigarette
smoke — whose relative potency
is already known from previous
epidemiological studies. These
substances will be used as a
yardstick against which to
estimate the carcinogenic
potency of diesel exhaust in
animal and in vitro experiments.
Such a comparison will provide
an idea of the degree of human
health risk associated with diesel
exhaust.
While the above risk assessments
will be very valuable, even more
informative for regulatory
decision-making would be an
estimate of the risk of diesel
exhaust relative to gasoline and
other combustion emissions
already present in ambient air.
Unfortunately, technical
problems associated with
collecting sufficient samples for
definitive health effects
experiments may limit the extent
of risk comparison that can be
made between diesel emissions
and gasoline exhaust, and
between diesel emissions and
ambient air. It is possible,
however, to collect enough
particles from gasoline
emissions and ambient air to
perform the in vitro and, in some
cases, whole animal skin
painting tests for rough potency
assessments. At present, this
work is being done on a limited
scale. If early results of the
comparison suggest that this
information will be important for
regulatory action, these studies
will be expanded.
31
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Control Technologies
32
The primary responsibility for
developing control technologies
lies with automobile
manufacturers, who must ensure
that every new vehicle meets
emissions standards set by the
EPA. To keep abreast of the
control technology development
situation, the Diesel Emissions
Research Program is funding a
small effort to investigate and
develop technologies for
controlling diesel emissions.
Results of this research will
assist regulators in determining
what level of control is
technologically and
economically feasible.
Paniculate Control. The main
thrust of the control technologies
research, currently under way at
the EPA's Industrial
Environmental Research
Laboratory in Research Triangle
Park (IERL-RTP) is to develop
and evaluate particulate control
devices. IERL-RTP is currently
investigating five particulate
control concepts — three filters,
an electrostatic device, and a
cyclonic agglomerator (Table 5).
Prototypes of these devices will
be built and tested by IERL-RTP
and its contractors.
An important factor that must be
considered in designing these
devices is how to handle the
large amount of toxic particles
that accumulate as light flaky
material on the after-treatment
device at the rate of about 1
kilogram every 1,000 to 2,000
miles (Figure 21). These particles
Figure 21.
Particulate control filter and collected particles. A. Clean filter prior to diesel exhaust
exposure. B. Outer casing (silver) and exposed filter (black). Filter contains particles that
accumulated after exposure to emissions from a light-duty diesel engine run for
approximately 2,000 kilometers. Jar contains additional loose particles that
accumulated within the device during the same exposure period. C. Photomicrograph
of diesel particles removed from a control device.
fPhotograph courtesy of Eikosha Company, Tokyo. Japan)
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Table 5 Control Devices Under Development by IERL-RTP
Type of Device
Collection
Storage
Disposal
Cyclonic agglomerator
Deep-bed filter
Catalytic filter
Electrostatic filter
Two-stage electrostatic collector
Particles are agglomerated
on a fine mesh and then
transported to a secondary
collector by a cyclonic device
which directs the particle flow
Particles are collected on a
deep-bed filter with suitable
capacity for particle storage
Particles are collected on a
relatively shallow filter which
has a suitable surface (substrate)
for catalytic oxidation
Particles are charged and then
collected on an electrostatically
charged filter
Particles are electrostatically
charged and then collected in
electrostatic fields between
concentric rings
Particles are compacted and
stored in the secondary
collector
Particles are compacted and
stored in the filter
Particles are not stored
Particles are stored on the
filter
Particles are automatically
washed off the rings with oil;
oil is stored in a sump
Secondary collector must be
emptied at approximately
5,000-mile intervals
Filter must be replaced at
approximately 5,000-mile intervals
Particles are continuously burned
off by catalytic oxidation
Disposal method to be developed
Particle-laden oil must be
drained from the sump at
approximately 5,000-mile intervals
33
must be either burned off or
stored and periodically removed.
If the latter approach is used,
sufficient storage capacity must
be available so that car owners
are not unduly inconvenienced
by a frequent need to attend to
particle removal and disposal.
Provisions must also be made for
ultimate disposal of the toxic
particles. IERL-RTP is
investigating a variety of particle
storage and removal methods
(Table 5) as potential solutions
for the particle handling
problem. In some cases,
conventional particle removal
technologies for stationary
sources are being modified for
application to moving vehicles.
Testing of the particulate control
technologies will involve a
determination of how successful
each device is in reducing the
amount of particles contained in
the exhaust. Each device will be
tested on a variety of diesel
engines to determine how engine
parameters affect control
effectiveness. Particles emitted
by controlled and uncontrolled
engines will also be compared in
the Ames mutagenicity test to
provide an idea of whether the
control technologies reduce the
levels of mutagenic and possibly
carcinogenic chemicals in diesel
exhaust.
Organic Emissions Control.
Since specific organic fractions
of diesel emissions may be
regulated in the future,
IERL-RTP is investigating
methods of reducing the level of
toxic organics in diesel
emissions. One approach for
organics control is to reduce
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ENGINE MODIFICATION
Fuel injection systems
Variable geometry turbo charging
Fumigation
Insulated engines
FUEL MODIFICATION
• Additives
• Emulsions
• Fuel properties
AFTERTREATMENT-
• Filters
• Scrubbers
• Electrostatic precipitators
• Catalytic converters
Approaches for diesel emissions control.
participate emissions since
diesel particles contain
substantial amounts (10 to 50
percent by weight) of organics.
As described above, participate
control devices are being tested
to determine their effectiveness
for reducing organic emissions.
In another line of research,
IERL-RTP engineers are
exploring the possibility of using
oxidation catalysts to burn the
organics, thereby reducing them
to relatively innocuous gases.
Since catalysts generally work
best on molecules in the gas
phase, tests are being done to
determine how soon the diesel
organics condense onto the
particles after leaving the engine.
Preliminary results indicate that
diesel organics may remain
gaseous in the tail pipe long
enough to be acted upon by a
catalytic device. If these results
are confirmed by further tests,
IERL-RTP may try to develop
suitable catalyses) for oxidizing
the high molecular weight
organics that characterize diesel
emissions.
Fuel and Engine Modification.
Other possible means of
reducing hazardous emissions
include modifying the fuel or
the engine. These approaches
are being pursued under other
EPA programs and, if they prove
fruitful, may be utilized or
expanded upon by the Diesel
Emissions Research Program.
34
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Other Federal Agency
Diesel Health Effects
Research
This document describes
EPA's Diesel Emission
Research Program. In addition
to this effort, the Department
of Energy is conducting a
research program which will
provide additional data to
permit the Federal Govern-
ment to develop and
implement a regulatory
program which will protect
human health while minimiz-
ing restrictions on the
utilization of thediesel engine.
The two prog rams are
coordinated and comple-
mentary.
Both Programs:
• augmentthesmall eptdemi-
ological data base presently
available concerning the
health effects of actual
human exposures to diesel
emissions.
• improve our knowledge of
the chemical characteriza-
tion of mutagenic and
carcinogenic agents that are
associated with diesel
paniculate emissions.
• improve knowledge of the
potential human exposures
to diesel paniculate
emissions.
• provide risk assessments of
increased diesel use.
Budgets for diesel health
effects research:
DOE
EPA
FY79
FY80
FY81*
2.2
2.8
2.4
5.7
6.3
6.5
'Presidential Budget Submission
Distinctive features of the
programs:
DOE
• Uses primarily animal inhala-
tion experiments.
• Uses multiple exposure/dose
levels to determine dose-
response relationships.
• Focuses on carcinogenic end
point.
EPA
• Uses inhalation, other in vivo
models such as skin painting
and intraperitoneal injection
and in vitro bioassays.
• Determines relative carcino-
genic potency of diesel
paniculate extract as compared
to other known carcinogens.
• Uses pulmonary, behavioral,
mutagenic effects, and enzyme
induction end points in addition
tocarcinogenicity.
• Performs bioassays in particles
found in ambient air samples
where diesels are and are not
expected to be significant
contributors.
35
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This project was coordinated by the Center for Environmental Resear? Information
under the direction of Clarence A. demons. This report was prepared for the EPA Mobile Source
Research Committee under the guidance of Roger S. Cortesi, Matrix Manager Mobile Source Research
Program. All material was written by Jan Connery of Energy Resources Co. Inc. Cambridge,
Massachusetts from material provided by the Research Comm.ttee; Virginia Hathaway of JACA Corp.
Philadelphia, Pennsylvania was coordinator for production.
Acknowledgement is made to the many persons who were involved in reviewing draft material and
especially to those who provided technical assistance. Major contributors were:
Enviromental Monitoring Systems Laboratory— RTF
Thomas R. Mauser and Robert H. Jungers
Environmental Sciences Research Laboratory— RTP
Ronald L. Bradow
Health Effects Research Laboratory— Ci
Norman A. Clarke, R. John Garner, Robert K. Miday, and William E. Pepelko
Health Effects Research Laboratory — RTP
Larry Claxton, Judith A. Graham, Joellen Huisingh,
Stephen Nesnow, James R. Smith, and Orin W. Stopinski
Industrial Environmental Research Laboratory— RTP
James H. Abbot, Dennis Drehmel, and John W. Wasser
Office of Health and Environmental Assessment — DC
Roy Albert and Todd Thorslund
Office of Mobile Source Air Pollution Control — Ann Arbor
Allan Ader, Charles Gray, Karl Hellman, and Joseph H. Somers
Office of Monitoring and Technical Support— DC
Lance Wallace
Office of Research Program Management— DC
Mitchell Luxenberg
Comments or questions regarding this report should be addressed to:
Roger S. Cortesi
Office of Health Research (MD-683)
U. S. Environmental Protection Agency
Washington, DC 20460
Area Code (202) 426-2382
This report has been reviewed and approved for publication. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
Single copies of this report are available from:
Center for Environmental Research Information
U. S. Environmental Protection Agency
Cincinnati, OH 45268
36
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