Document ID: EPA-HQ-OAR-2003-0188-0028
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2003-11-20T05:00Z

An
Evaluation
of
the
Human
Carcinogenic
Potential
of
Ethylene
Glycol
Butyl
Ether
National
Center
for
Environmental
Assessment
Office
of
Research
and
Development
U.
S.
Environmental
Protection
Agency
August
2003
(
INTERIM
FINAL)

NOTICE
This
document
is
intended
for
internal
use
only
and
presents
the
Agency's
interim
position
based
on
the
available
information.
It
has
not
been
formally
released
by
the
U.
S.
Environmental
Protection
Agency
and
should
not
at
this
stage
be
construed
to
represent
the
Agency's
final
position
on
this
chemical.

U.
S.
Environmental
Protection
Agency
Washington
D.
C.
AUGUST,
2003
INTERIM
FINAL
­
DO
NOT
CITE
OR
QUOTE
ii
DISCLAIMER
This
document
is
intended
for
internal
use
only
and
presents
the
Agency's
interim
position
based
on
the
available
information.
It
has
not
been
formally
released
by
the
U.
S.
Environmental
Protection
Agency
and
should
not
at
this
stage
be
construed
to
represent
the
Agency's
final
position
on
this
chemical.
Mention
of
trade
names
or
commercial
products
does
not
constitute
endorsement
or
recommendation
for
use.
AUGUST,
2003
INTERIM
FINAL
­
DO
NOT
CITE
OR
QUOTE
iii
TABLE
OF
CONTENTS
AUTHORS,
CONTRIBUTORS,
AND
REVIEWERS
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iv
EXECUTIVE
SUMMARY
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1
ATTACHMENT
1:
Forestomach
Tumors
in
Female
Mice
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
.
.
A1­
1
ATTACHMENT
2:
Liver
Hemangiosarcoma
and
Hepatocellular
Carcinoma
in
Male
Mice
.
A2­
1
ATTACHMENT
3:
Benchmark
Dose
Assessment
of
Forestomach
Lesions
in
Female
Mice
Using
PBPK
Models
to
Estimate
Human
Equivalent
Exposures
.
.
A3­
1
ATTACHMENT
4:
External
Peer
Review
 
Summary
of
Comments
and
Disposition
.
.
.
.
.
A4­
1
AUGUST,
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iv
AUTHORS
AND
REVIEWERS
Primary
Author
Jeff
Gift,
Ph.
D.
U.
S.
EPA
National
Center
for
Environmental
Assessment
Internal
EPA
Reviewers
Jennifer
Jinot,
Ph.
D.
U.
S.
EPA
National
Center
for
Environmental
Assessment
Jean
Parker,
Ph.
D.
U.
S.
EPA
Office
of
Prevention,
Pesticides
and
Toxic
Substances
Paul
White,
Ph.
D.
U.
S.
EPA
National
Center
for
Environmental
Assessment
John
Lipscomb,
Ph.
D.
U.
S.
EPA
National
Center
for
Environmental
Assessment
Larry
Valcovich,
Ph.
D.
U.
S.
EPA
National
Center
for
Environmental
Assessment
Michel
Stevens,
Ph.
D.
U.
S.
EPA
National
Center
for
Environmental
Assessment
External
Peer
Reviewers
Burhan
I.
Ghanayem,
Ph.
D.
National
Institute
of
Environmental
Health
Sciences
Dale
Hattis,
Ph.
D.
Center
for
Technology,
Environment,
and
Development
(
CENTED)

Philip
Leber,
Ph.
D.
The
Goodyear
Tire
&
Rubber
Co.

Andrew
Gale
Salmon
M.
A.,
D.
Phil.,
C.
Chem.,
M.
R.
S.
C.
California
EPA
Office
of
Environmental
Health
Hazard
Assessment
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v
Michael
D.
Shelby,
Ph.
D.
Director,
NTP
Center
for
the
Evaluation
of
Risks
to
Human
Reproduction
Summaries
of
the
external
peer
reviewers'
comments
and
the
disposition
of
their
recommendations
are
in
Attachment
4.
AUGUST,
2003
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1
An
Evaluation
of
the
Human
Carcinogenic
Potential
of
Ethylene
Glycol
Butyl
Ether
EXECUTIVE
SUMMARY
Since
the
publication
of
NTP's
draft
report
(
NTP,
1998)
on
their
2­
year
inhalation
bioassay
of
ethylene
glycol
butyl
ether
(
EGBE;
2­
butoxyethanol),
there
has
been
continued
discussion
among
scientists
from
government,
industry,
and
academia
concerning
the
human
carcinogenic
potential
of
EGBE.
NTP
(
1998;
2000)
reported
that
their
study
results
indicate
no
evidence
of
carcinogenic
activity
in
male
F344/
N
rats,
equivocal
evidence
of
carcinogenic
activity
in
female
F344/
N
rats
based
on
increased
combined
incidence
of
benign
and
malignant
pheochromocytomas,

some
evidence
of
carcinogenic
activity
in
male
B6C3F1
mice
based
on
increased
incidence
of
hemangiosarcomas
of
the
liver,
and
some
evidence
of
carcinogenic
activity
in
female
B6C3F1
mice
based
on
increased
incidence
of
forestomach
squamous
cell
papillomas
or
carcinomas.
The
U.
S.

Environmental
Protection
Agency
(
EPA)
IRIS
(
Integrated
Risk
Information
System)
assessment
(
U.
S.
EPA,
1999a)
concluded
that,
in
accordance
with
the
proposed
Guidelines
for
Carcinogen
Risk
Assessment
(
U.
S.
EPA,
1996),
the
human
carcinogenicity
of
EGBE
"
cannot
be
determined
at
this
time,
but
suggestive
evidence
exists
from
rodent
studies."
Under
the
pre­
existing
EPA
guidelines
(
U.
S.
EPA,
1986),
EGBE
was
judged
to
be
a
possible
human
carcinogen."
These
findings
by
EPA
and
NTP
prompted
investigators,
largely
supported
by
the
Glycol
Ethers
Panel
of
the
American
Chemistry
Council,
to
design
research
projects
aimed
at
determining
the
mode
of
action
for
the
formation
of
the
forestomach
and
liver
tumors
observed
in
mice.
In
this
paper,

recent
findings
reported
in
scientific
publications
and
meetings
and
EPA
interim
(
U.
S.
EPA,
1The
increased
incidence
of
pheochromocytomas
reported
by
NTP
is
not
addressed
here
because
these
tumors
were
reported
to
have
been
difficult
to
distinguish,
were
not
statistically
increased
over
chamber
controls,
and
were
not
a
contributing
factor
in
the
IRIS
assessment
of
human
carcinogenic
risk
from
EGBE
exposure
(
U.
S.
EPA,
1999a).

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2
1999b)
and
draft
final
(
U.
S.
EPA,
2003)
cancer
guidelines
are
used
to
provide
an
up­
to­
date
evaluation
of
the
mode
of
action
involved
in
the
origin
of
these
tumors1
in
mice
and
their
human
relevance.

Establishing
the
mode
of
action
is
critical
for
determining
relevance
to
humans
and
for
choosing
the
approach
most
appropriate
for
dose­
response
modeling
(
i.
e.,
whether
to
use
a
linear
or
nonlinear
approach).
As
is
extensively
discussed
in
the
Agency's
interim
and
draft
cancer
guidelines
(
U.
S.
EPA,
1999b;
2003),
in
order
to
determine
a
chemical's
mode
of
action,
one
must
consider
the
full
range
of
key
influences
a
chemical
or
its
metabolites
might
have
as
an
initiator
or
promoter
of
the
complex
carcinogenic
process.
With
this
in
mind,
EGBE's
role
in
the
formation
of
female
mouse
forestomach
(
Attachment
1)
and
male
mouse
liver
(
Attachment
2)
tumors
observed
following
two­
years
of
inhalation
exposure
(
National
Toxicology
Program,
2000)
were
evaluated.

These
assessments
are
summarized
below.

Forestomach
papillomas
and
carcinoma
in
female
mice
Table
1
summarizes
the
dose­
response
data
for
key
tumor
types
observed
in
female
mice
in
the
NTP
(
2000)
inhalation
study
of
EGBE.
At
the
250
ppm
exposure
level,
the
10%
incidence
of
squamous
cell
papillomas
and
12%
combined
incidence
of
squamous
cell
papillomas
or
carcinomas
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3
were
significantly
increased
over
study
controls
and
exceeded
the
ranges
for
historical
controls
of
0­
2%
and
0­
3%,
respectively.
NTP
(
2000)
reports
that
8%
is
the
highest
incidence
of
forestomach
neoplasms
that
has
been
observed
in
contemporary
historical
controls.
NTP
(
2000)
did
not
observe
significant
increases
in
forestomach
papillomas
and
carcinomas
at
other
exposure
levels
in
female
mice,
nor
at
any
exposure
level
in
male
mice
or
either
sex
of
rats.

Recent
reviews
of
available
in
vitro
and
in
vivo
genotoxicity
assays
are
in
agreement
that
EGBE
is
not
likely
to
be
genotoxic
(
Commonwealth
of
Australia,
1996;
Elliot
and
Ashby,
1997;

U.
S.
EPA,
1999a;
NTP,
2000).
NTP
(
2000)
suggested
that
EGBE
caused
chronic
irritation
leading
to
forestomach
injury
including
penetrating
ulcers
and
that
the
observed
"
neoplasia
[
papillomas
and
one
carcinoma]
was
associated
with
a
continuation
of
the
injury/
degeneration
process."
Table
2
provides
a
summary
of
the
strength
of
the
evidence
and
the
relevance
to
humans
of
this
nongenotoxic
and
nonlinear
mode
of
action
for
EGBE's
role
in
the
formation
of
these
forestomach
papillomas
and
carcinomas
(
Cantox,
2000;
NTP,
2000;
Green
et
al.,
2002;
Poet
et.

al.,
2003).

The
Agency
believes
that
a
nonlinear
mode
of
action
similar
to
that
which
is
represented
in
Table
2
and
described
further
in
Attachment
1,
is
principally
responsible
for
the
increased
forestomach
tumor
incidence
reported
by
NTP
(
2000).
However,
reports
of
weak
positive
effects
by
EGBE
at
high
concentrations
in
some
in
vitro
DNA
repair,
sister
chromatic
exchange
and
cell
transformation
assays
(
see
discussion
in
Attachment
1
under
"
Other
Possible
Modes
of
Action
for
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4
Forestomach
Tumor
Development
in
Female
Mice")
make
it
difficult
to
completely
exclude
the
potential
for
contribution
from
direct
interaction
of
an
EGBE
metabolite
with
DNA.
While
these
positive
findings
may
be
due
to
study
design
artifacts
(
e.
g.,
changes
in
pH
or
osmolarity
associated
with
high
EGBE
concentrations),
they
may
also
be
due
to
butoxyacetaldehyde
(
BAL),
a
shortlived
metabolite
of
EGBE
that
has
caused
clastogenic
changes
in
Chinese
hamster
lung
(
V79)
and
human
lymphocyte
cells
(
Elliot
and
Ashby,
1997).
As
is
discussed
in
Attachment
1,
available
evidence
from
a
published
EGBE
PBPK
model
that
has
been
modified
to
include
kinetics
for
the
metabolism
of
the
BAL
intermediate
(
Corley,
2003)
suggests
that
the
conditions
of
these
in
vitro
assays
(
e.
g.,
no
metabolic
activation;
high,
cytotoxic
concentrations
of
BAL)
are
of
little
relevance
to
expected
target
organ
(
forestomach)
environment
(
e.
g.,
high
metabolic
activity;
low
concentrations
of
BAL).
However,
additional
research
(
e.
g.,
verification
of
these
PBPK
modeling
results
and
further
genotoxicity
research
using
more
appropriate
assays
and
currently
accepted
test
protocols)
is
needed
before
a
more
definitive
determination
can
be
made
regarding
the
role
of
BAL
in
the
formation
of
forestomach
tumors
in
female
mice.

Liver
Tumors
in
Male
Mice
Table
3
summarizes
the
data
for
tumor
types
which
were
significantly
increased
in
male
mice
exposed
to
EGBE
by
NTP
(
2000).
Particular
focus
has
been
placed
on
hemangiosarcomas
of
the
liver
because
this
was
the
only
tumor
type
that
was
increased
over
both
concurrent
and
historical
controls
and
because
a
mode
of
action
involving
EGBE
has
been
proposed
for
this
tumor
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5
(
Siesky
et
al.,
2002).
Though
the
incidence
of
hepatocellular
carcinomas
was
within
the
range
of
historical
controls
for
male
mice,
consideration
was
given
to
this
tumor
because
the
dose­
response
trend
is
significant
and
because
a
similar
mode
of
action
has
been
suggested
for
this
tumor.

Table
4
summarizes
the
strength
of
the
evidence
and
the
relevance
to
humans
of
the
mode
of
action
described
in
Attachment
2
for
EGBE's
potential
role
in
the
formation
of
hemangiosarcomas
and
hepatocellular
carcinomas
in
the
livers
of
male
mice.
A
metabolite
of
EGBE,
butoxyacetic
acid
(
BAA),
has
long
been
known
to
cause
hemolysis
in
rodents
(
Carpenter
et
al,
1956).
This
hemolysis
leads
to
the
accumulation
of
hemosiderin
(
iron)
in
phagocytic
Kupffer
cells
of
the
liver
of
both
rats
and
mice
(
NTP,
2000).
Recent
research
in
mice
and
rats
indicates
that
the
increased
iron
levels
associated
with
EGBE­
induced
hemolysis
produces
liver
oxidative
damage
that
is
more
severe
in
mice
and
increased
DNA
synthesis
in
both
endothelial
cells
and
hepatocytes
that
is
unique
to
mice
(
Siesky
et
al.,
2002).
It
is
hypothesized
that
these
events
can
contribute
to
the
transformation
of
the
endothelial
cells
to
hemangiosarcomas
and
hepatocytes
to
hepatocellular
carcinomas
in
male
mice.
Given
the
high
background
rate
of
these
two
tumor
types
in
male
mice
(
2.9%
and
24%)
relative
to
female
mice
(
0.9%
and
14%)
and
rats
(
0%
and
0.4%;

combined
male
and
female)
(
NTP,
2002),
it
is
reasonable
to
hypothesize
that
the
endothelial
cells
and
hepatocytes
in
the
livers
of
male
mice
are
more
susceptible
to
oxidative
stress
resulting
from
iron
buildup
in
local
Kupffer
cells.
While
additional
research
would
be
informative
with
respect
to
mechanistic
issues
such
as
the
relative
susceptibility
of
endothelial
cells
and
hepatocytes
to
oxidative
stress
caused
by
the
hemolytic
effects
of
EGBE
and
the
apparent
resistance
of
female
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6
mice
to
the
development
of
hemangiosarcomas
despite
experiencing
similar
hemolytic
effects,
there
is
enough
evidence
at
this
time
to
support
an
EPA
determination
that
events
associated
with
hemolysis
contributed
to
the
increased
incidence
of
these
tumors
in
male
mice
exposed
to
EGBE.

Available
evidence
appears
to
support
a
nonlinear
mode
of
action
similar
to
the
one
described
here
and
in
Attachment
2
as
principally
responsible
for
the
increased
liver
tumor
incidence
reported
by
NTP
(
2000)
for
male
mice.
However,
as
described
above
for
forestomach
tumors
observed
in
female
mice,
the
weak
positive
effects
by
EGBE
in
some
in
vitro
genotoxicity
assays
and
the
reported
clastogenicity
of
the
EGBE
metabolite
(
BAL)
make
it
difficult
to
completely
exclude
the
potential
for
contribution
from
direct
interaction
of
an
EGBE
metabolite
with
DNA.
As
is
discussed
in
Attachment
2,
the
Corley
(
2003)
PBPK
model
suggests
that
the
conditions
of
these
in
vitro
assays
(
e.
g.,
no
metabolic
activation;
high,
cytotoxic
concentrations
of
BAL)
are
of
little
relevance
to
expected
target
organ
(
liver)
environment
(
e.
g.,
high
metabolic
activity;
low
concentrations
of
BAL).
Here
again,
additional
research
(
e.
g.,
verification
of
the
PBPK
modeling
results
and
improved
genotoxicity
research)
is
needed
before
a
more
definitive
determination
can
be
made
regarding
the
role
of
BAL
in
the
formation
of
liver
tumors
in
male
mice.
2These
analyses
are
consistent
with
the
nonlinear
assessment
approach
described
in
existing
interim
(
U.
S.
EPA,
1999a)
and
draft
(
2003)
cancer
guidelines.

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7
Risk
to
Humans
Forestomach
tumors
in
female
mice
­
Available
data
establish
a
plausible
nonlinear,

nongenotoxic
mode
of
action
for
the
moderate
increase
observed
by
NTP
(
2000)
in
the
incidence
of
forestomach
tumors
in
female
mice
following
chronic
inhalation
exposure
to
EGBE.

Forestomach
tissue
irritation
caused
by
constant
exposure
to
EGBE
and
its
metabolites
and
subsequent
cell
proliferation
appear
to
be
key
precursor
events
in
the
mode
of
action
for
these
tumors.
While
certain
dosimetric
processes
and
morphological
aspects
of
the
forestomach
make
rodents
particularly
susceptible
to
these
events,
this
mode
of
action
is
judged
to
be
of
qualitative
relevance
to
humans.
However,
due
to
the
lack
of
a
comparable
organ
for
storage
and
the
long
term
retention
of
EGBE,
the
exposure
concentrations
that
would
be
necessary
to
cause
hyperplastic
effects
and
tumors
in
humans,
if
attainable,
are
likely
to
be
much
higher
than
the
concentrations
necessary
to
cause
forestomach
effects
in
mice.
In
fact,
the
analysis
in
Attachment
3
indicates
that
the
exposure
concentrations
necessary
to
cause
hyperplastic
effects
in
humans
would
be
much
higher
than
the
existing
RfD
and
RfC
for
EGBE.
Given
that
humans,
including
potentially
sensitive
subpopulations
such
as
children,
have
no
known
organ
for
the
retention
of
a
comparable
target
dose
of
EGBE
or
its
metablolites,
it
appears
reasonable
to
assume
that
the
RfC
and
RfD
developed
for
EGBE
(
EPA,
1999a)
are
sufficient
for
the
prevention
of
hyperplasia
and
associate
tumors
in
humans.
2
3These
analyses
are
consistent
with
the
nonlinear
assessment
approach
described
in
existing
interim
(
U.
S.
EPA,
1999a)
and
draft
(
2003)
cancer
guidelines.

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8
Liver
tumors
in
male
mice
­
Available
data
establish
a
plausible
nonlinear,
nongenotoxic
mode
of
action
for
the
moderate
increase
observed
by
NTP
(
2000)
in
the
incidence
of
liver
tumors
in
male
mice
following
chronic
inhalation
exposure
to
EGBE.
The
proposed
mode
of
action
suggests
that
the
endothelial
cells
and
hepatocytes
of
male
mice
are
sensitive
to
the
formation
of
the
subject
neoplasms
(
as
evidenced
by
the
relatively
high
background
rate
of
these
tumors
in
male
mice)
and
that
excess
iron
from
EGBE­
induced
hemolysis
can
result
in
sufficient
iron­
induced
oxidative
stress
to
cause
the
observed,
marginal
increase
in
the
incidence
of
liver
hemangiosarcomas
and
hepatocellular
carcinomas
in
these
animals
(
NTP,
2000).
Given
the
relatively
low
sensitivity
of
humans,
including
subpopulations
such
as
children,
to
the
hemolytic
effects
of
EGBE,
it
appears
reasonable
to
assume
that
the
EGBE
RfC
and
RfD
(
EPA,
1999a)
are
sufficient
for
the
prevention
of
hemolysis
and
associate
tumors
in
humans.
3
Conclusion
Concerning
EGBE's
Cancer
Risk
­
Information
available
to
the
Agency
at
this
time
indicate
that
nonlinear
modes
of
action
are
likely
responsible
for
the
increased
incidence
of
tumors
observed
by
NTP
(
2000)
in
mice
following
chronic
EGBE
exposure.
Application
of
nonlinear
quantitative
assessment
methods
indicate
that
the
noncancer
RfD
(
0.5
mg/
kg/
day)
and
RfC
(
13
mg/
m3)
values
developed
for
EGBE
(
EPA,
1999a)
are
adequately
protective
of
these
carcinogenic
effects.
However,
this
determination
assumes
a
nonlinear
mechanism
that
requires
exposure
levels
to
be
high
enough
to
cause
certain
lesions
that
are
considered
to
be
precancerous.

Information
is
currently
inadequate
to
dismiss
the
potential
contribution
of
a
linear
mechanism
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9
associated
with
the
possible
mutagenic
metabolite
BAL.
A
definitive
determination
regarding
the
appropriateness
of
a
nonlinear
approach
can
not
be
made
until
questions
regarding
the
role
of
BAL
are
resolved.
As
discussed
above,
additional
research
(
e.
g.,
verification
of
existing
PBPK
modeling
results
and
improved
genotoxicity
assays)
would
assist
the
Agency
in
making
a
more
informed
decision
concerning
the
potential
for
BAL
to
contribute
to
the
adverse
effects
seen
in
animals
following
EGBE
exposure
and
use
of
the
proposed
nonlinear
assessment
approach.
4Poly­
3
test
estimate
taken
from
NTP,
2000
technical
report
series
484
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10
Table
1
­
Key
Tumors
Observed
in
Female
Mice
Exposed
to
EGBE
(
NTP,
2000)

Control
62.5
ppm
125
ppm
250
ppm
Squamous
Cell
Papilloma
­
Forestomach
Overall
rate
Rate
adjusted
for
intercurrent
mortality4
First
incidence
(
days)
0/
50
0%
0%
NA
1/
50
2%
2.4%
731
2/
50
4%
4.8%
731
5/
50
10%
11.2%
582
Squamous
Cell
Papilloma
or
Carcinoma
­
Forestomach
Overall
rate
Rate
adjusted
for
intercurrent
mortality
First
incidence
(
days)
0/
50
0%
0%
NA
1/
50
2%
2.4%
731
2/
50
4%
4.8%
731
6/
50
12%
13.4%
582
5Weight
of
Evidence
is
either
strong,
moderate
or
weak;
a
strong
weight
of
evidence
is
defined
as
having
several
studies
which
support
the
proposed
mode
of
action,
preferably
from
multiple
laboratories
with
limited
evidence
of
contradiction.
Weak
evidence
is
normally
defined
as
a
single
study
from
a
single
laboratory
or
with
a
significant
amount
of
contradiction
in
the
literature
between
reports.

6Specificity
to
the
proposed
mode
of
action.
Specificity
is
high
if
an
event
is
unique
to
this
particular
mode
of
action.
Specificity
is
low
if
the
event
may
be
seen
in
many
other
modes
of
action.

7This
step
is
confirmed
by
recent
research
in
mice
(
Green
et
al.,
2002;
Poet
et
al.,
2003)
but
has
not
been
investigated
in
rats,
which
do
not
develop
forestomach
tumors
following
EGBE
exposure.

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11
Table
2
­
Concordance
Table
Showing
the
Relationship
of
Proposed
Mode
of
Action
for
Formation
of
Forestomach
Tumors
in
Female
Mice
to
Humans
Event
Relation
to
Animal
Tumors
Overall
Weight
of
Evidence5
Qualitative
Relation
to
Humans
Quantitative
Relation
to
Humans
Specificity6
Dose/
Temporal
Relation
Biological
plausibility
1.
Deposition
of
EGBE/
BAA
in
stomach
and
forestomach
via
consumption
or
reingestion
of
EGBE
laden
mucous,
salivary
excretions
and
fur
material
Moderate7
Lower/
Earlier
Moderate
Strong
Moderate
Moderate
2.
Retention
of
EGBE/
BAA
in
food
particles
of
the
forestomach
long
after
being
cleared
from
other
organs
Moderate4
Lower/
Earlier
Moderate
Moderate
Low
Not
Likely
3.
Metabolism
of
EGBE
to
BAA
systemically
and
in
forestomach
High
Lower/
Earlier
High
Strong
??
??

4.
Irritation
of
target
cells
leading
to
hyperplasia
and
ulceration
High
Lower/
Earlier
High
Moderate
Not
Likely
Not
Likely
5.
Continued
injury
and
degeneration
leading
to
high
cell
proliferation
and
turnover
High
??
High
Weak
Not
Likely
Not
Likely
6.
High
cell
proliferation
and
turnover
leads
to
clonal
growth
of
initiated
forestomach
cells
Moderate
??
High
Moderate
Not
Likely
Not
Likely
8Poly­
3
test
estimate
taken
from
NTP,
2000
technical
report
series
484
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12
Table
3
­
Key
Tumors
Observed
in
Male
Mice
Exposed
to
EGBE
(
NTP,
2000)

Control
62.5
ppm
125
ppm
250
ppm
Hemangiosarcomas
­
All
organs
Overall
rate
Rate
adjusted
for
intercurrent
mortality8
First
Incidence
(
days)
1/
50
2%
2.2%
729
1/
50
2%
2.1%
670
2/
50
4%
5.0%
704
5/
50
10%
12.4%
454
Hemangiosarcomas
­
Liver
only
Overall
rate
Rate
adjusted
for
intercurrent
mortality
First
Incidence
(
days)
0/
50
0%
0%
NA
1/
50
2%
2.1%
670
2/
49
4%
5.0%
704
4/
49
8%
10%
454
Hemangiosarcomas/
hemangiomas
­
All
organs
Overall
rate
Rate
adjusted
for
intercurrent
mortality
First
Incidence
(
days)
1/
50
2%
2.2%
NA
1/
50
2%
2.1%
670
4/
50
8%
10%
704
5/
50
10%
12.4%
454
Hepatocellular
Carcinoma
Overall
rate
Rate
adjusted
for
intercurrent
mortality
First
Incidence
(
days)
10/
50
20%
20.8%
374
11/
50
22%
22.9%
621
16/
49
33%
35.9%
430
21/
49
43%
45.9%
312
Hepatocellular
Adenoma
or
Carcinoma
Overall
rate
Rate
adjusted
for
intercurrent
mortality
First
Incidence
(
days)
30/
50
60%
61.9%
374
24/
50
48%
48.9%
549
31/
49
63%
67.5%
430
30/
49
61%
64.8%
312
9Event,
weight
of
evidence
and
specificity
columns
were
adopted
from
Klaunig
and
Kamendulis
(
2003)

10EGBE
is
metabolized
to
BAA
in
rats
and
mice,
but
the
tumor
is
only
increased
in
male
mice.

11Hemolysis
is
observed
in
both
sexes
of
rats
and
mice,
but
the
tumor
is
only
increased
in
male
mice.

12Hemosiderin
is
observed
in
Kupffer
cells
of
both
sexes
of
rats
and
mice,
but
the
tumor
is
only
increased
in
male
mice.
Early
(
subchronic)
hemosiderin
buildup
is
only
observed
in
male
mice,
however.

13These
effects
have
been
observed
to
be
more
pronounced
in
mice
(
Siesky
et
al,
2002),
which
are
also
more
susceptible
to
EGBE
induced
liver
tumor
formation
than
rats
(
NTP,
2000).

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Table
4
­
Concordance
Table
Showing
the
Relationship
of
Proposed
Mode
of
Action
for
Formation
of
Liver
Hemangiosarcomas
&
Hepatocellular
Carcinomas
in
Male
Mice
to
Humans9
Event
Relation
to
Animal
Tumors
Overall
Weight
of
Evidence5
Qualitative
Relation
to
Humans
Quantitative
Relation
to
Humans
Specificity6
Dose/
Temporal
Relation
Biological
Plausibility
1.
EGBE
metabolism
to
BAA
by
alcohol
dehydrogenase
High
Lower/
Earlier
Moderate
Moderate
to
Strong10
High
Moderate
2.
RBC
hemolysis
by
BAA
High
for
Hemolysis
Lower/
Earlier
Moderate
Moderate
to
Strong11
Low
Not
Likely
3.
Buildup
of
Hemosiderin
in
Kupffer
cells
of
liver
Low
Lower/
Earlier
Moderate
Moderate
to
Strong12
Not
Likely
Not
Likely
4a.
Production
of
reactive
oxygen
species
by
Fenton
or
Haber­
Weiss
reactions
Low
Higher/
Earlier
High
Weak13
Not
Likely
Not
Likely
4b.
Kupffer
cells
activated
and
release
cytokine
Low
??
Moderate
Weak
Not
Likely
Not
Likely
5.
Reactive
oxygen
species
results
in
oxidative
DNA
damage
to
endothelial
cells
Low
Higher/
Earlier
High
Weak12
Not
Likely
Not
Likely
6.
Modulation
of
endothelial
cell
gene
expression
Low
??
Moderate
Weak
Not
Likely
Not
Likely
7.
Endothelial
cell
proliferation
Low
??
Moderate
Strong
Not
Likely
Not
Likely
8.
Promotion
of
initiated
endothelial
cells
Low
??
High
Weak
Not
Likely
Not
Likely
9.
Neoplasm
formation
Low
??
High
Strong
Not
Likely
Not
Likely
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14
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