Document ID: EPA-HQ-OPPT-2004-0128-0002
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2006-10-12T04:00Z

PROPOSED:
9/
2003
Styrene
(
CAS
Reg.
No.
100­
42­
5)

PROPOSED
ACUTE
EXPOSURE
GUIDELINE
LEVELS
(
AEGLs)
PREFACE
Under
the
authority
of
the
Federal
Advisory
Committee
Act
(
FACA)
P.
L.
92­
463
of
1972,
the
National
Advisory
Committee
for
Acute
Exposure
Guideline
Levels
for
Hazardous
Substances
(
NAC/
AEGL
Committee)
has
been
established
to
identify,
review
and
interpret
relevant
toxicologic
and
other
scientific
data
and
develop
AEGLs
for
high
priority,
acutely
toxic
chemicals.

AEGLs
represent
threshold
exposure
limits
for
the
general
public
and
are
applicable
to
emergency
exposure
periods
ranging
from
10
minutes
to
8
hours.
Three
levels
 
AEGL­
1,
AEGL­
2
and
AEGL­
3
 
are
developed
for
each
of
five
exposure
periods
(
10
and
30
minutes,
1
hour,
4
hours,
and
8
hours)
and
are
distinguished
by
varying
degrees
of
severity
of
toxic
effects.
The
three
AEGLs
are
defined
as
follows:

AEGL­
1
is
the
airborne
concentration
(
expressed
as
parts
per
million
or
milligrams
per
cubic
meter
[
ppm
or
mg/
m3])
of
a
substance
above
which
it
is
predicted
that
the
general
population,
including
susceptible
individuals,
could
experience
notable
discomfort,
irritation,
or
certain
asymptomatic,
non­
sensory
effects.
However,
the
effects
are
not
disabling
and
are
transient
and
reversible
upon
cessation
of
exposure.

AEGL­
2
is
the
airborne
concentration
(
expressed
as
ppm
or
mg/
m3)
of
a
substance
above
which
it
is
predicted
that
the
general
population,
including
susceptible
individuals,
could
experience
irreversible
or
other
serious,
long­
lasting
adverse
health
effects
or
an
impaired
ability
to
escape.

AEGL­
3
is
the
airborne
concentration
(
expressed
as
ppm
or
mg/
m3)
of
a
substance
above
which
it
is
predicted
that
the
general
population,
including
susceptible
individuals,
could
experience
life­
threatening
health
effects
or
death.

Airborne
concentrations
below
the
AEGL­
1
represent
exposure
levels
that
could
produce
mild
and
progressively
increasing
but
transient
and
nondisabling
odor,
taste,
and
sensory
irritation
or
certain
asymptomatic,
non­
sensory
effects.
With
increasing
airborne
concentrations
above
each
AEGL,
there
is
a
progressive
increase
in
the
likelihood
of
occurrence
and
the
severity
of
effects
described
for
each
corresponding
AEGL.
Although
the
AEGL
values
represent
threshold
levels
for
the
general
public,
including
susceptible
subpopulations,
such
as
infants,
children,
the
elderly,
persons
with
asthma,
and
those
with
other
illnesses,
it
is
recognized
that
individuals,
subject
to
unique
or
idiosyncratic
responses,
could
experience
the
effects
described
at
concentrations
below
the
corresponding
AEGL
level.
Styrene
NAC:
02/
2004
iii
TABLE
OF
CONTENTS
PREFACE
........................................................................................................................................
1
EXECUTIVE
SUMMARY............................................................................................................
VI
1
INTRODUCTION....................................................................................................................
1
2
HUMAN
TOXICITY
DATA...................................................................................................
3
2.1
Acute
Lethality..................................................................................................................
3
2.2
Nonlethal
Toxicity.............................................................................................................
3
2.2.1
Case
Reports..........................................................................................................
3
2.2.2
Occupational
exposure...........................................................................................
4
2.2.3
Experimental
Studies.............................................................................................
5
2.3
Developmental/
Reproductive
Toxicity............................................................................
13
2.4
Genotoxicity
....................................................................................................................
13
2.5
Carcinogenicity
...............................................................................................................
14
2.6
Summary.........................................................................................................................
14
3
ANIMAL
TOXICITY
DATA................................................................................................
17
3.1
Acute
Lethality................................................................................................................
17
3.1.1
Rats......................................................................................................................
17
3.1.2
Mice
.....................................................................................................................
21
3.1.3
Guinea
pigs
..........................................................................................................
23
3.1.4
Hamsters..............................................................................................................
23
3.2
Nonlethal
Toxicity...........................................................................................................
24
3.2.1
Nonhuman
primates.............................................................................................
24
3.2.2
Rats......................................................................................................................
24
3.2.3
Mice
.....................................................................................................................
27
3.2.4
Guinea
pigs
..........................................................................................................
29
3.2.5
Rabbits.................................................................................................................
29
3.3
Developmental/
Reproductive
Toxicity............................................................................
30
3.3.1
Rats......................................................................................................................
30
3.3.2
Mice
.....................................................................................................................
31
3.3.3
Rabbits.................................................................................................................
32
3.3.4
Hamsters..............................................................................................................
32
3.4
Genotoxicity
....................................................................................................................
32
3.5
Carcinogenicity
...............................................................................................................
34
3.6
Summary.........................................................................................................................
37
4
SPECIAL
CONSIDERATIONS............................................................................................
41
4.1
Toxicokinetics
.................................................................................................................
41
4.2
Mechanism
of
Toxicity
....................................................................................................
48
4.3
Other
relevant
information.............................................................................................
48
4.3.1
PBPK­
Modelling..................................................................................................
48
4.3.2
Species
variability................................................................................................
49
4.3.3
Susceptible
populations
.......................................................................................
49
4.3.4
Concurrent
exposure
issues
.................................................................................
50
Styrene
NAC:
02/
2004
iv
5
DATA
ANALYSIS
AND
PROPOSED
AEGL­
1
...................................................................
50
5.1
Summary
of
Human
Data
Relevant
to
AEGL­
1.............................................................
50
5.2
Summary
of
Animal
Data
Relevant
to
AEGL­
1
.............................................................
50
5.3
Derivation
of
AEGL­
1
....................................................................................................
51
6
DATA
ANALYSIS
AND
PROPOSED
AEGL­
2
...................................................................
51
6.1
Summary
of
Human
Data
Relevant
to
AEGL­
2.............................................................
51
6.2
Summary
of
Animal
Data
Relevant
to
AEGL­
2
.............................................................
52
6.3
Derivation
of
AEGL­
2
....................................................................................................
54
7
DATA
ANALYSIS
AND
PROPOSED
AEGL­
3
...................................................................
55
7.1
Summary
of
Human
Data
Relevant
to
AEGL­
3.............................................................
55
7.2
Summary
of
Animal
Data
Relevant
to
AEGL­
3
.............................................................
56
7.3
Derivation
of
AEGL­
3
....................................................................................................
56
8
SUMMARY
OF
PROPOSED
AEGLS..................................................................................
58
8.1
AEGL
Values
and
Toxicity
Endpoints
...........................................................................
58
8.2
Comparison
with
Other
Standards
and
Guidelines
........................................................
60
8.3
Data
Adequacy
and
Research
Needs
..............................................................................
62
9
REFERENCES.......................................................................................................................
62
APPENDIX
A:
DERIVATION
OF
AEGL
VALUES...................................................................
73
APPENDIX
B:
DERIVATION
OF
EXPONENTIAL
FUNCTION
FOR
TEMPORAL
SCALING
77
APPENDIX
C:
BENCHMARK
CALCULATIONS
FOR
STYRENE........................................
79
APPENDIX
D:
DERIVATION
SUMMARY
FOR
STYRENE
AEGLS......................................
83
APPENDIX
E:
DERIVATION
OF
THE
LEVEL
OF
DISTINCT
ODOR
AWARENESS.........
87
LIST
OF
TABLES
TABLE
1:
CHEMICAL
AND
PHYSICAL
PROPERTIES
...........................................................
2
TABLE
2:
SUMMARY
OF
ACUTE
NON­
LETHAL
EFFECTS
IN
CONTROLLED
HUMAN
STUDIES
FOLLOWING
INHALATION
OF
STYRENE....................................................
9
TABLE
3:
SUMMARY
OF
LETHAL
EFFECTS
IN
ANIMALS
AFTER
ACUTE
INHALATION
EXPOSURE
TO
STYRENE..................................................................................................
18
TABLE
4:
SUMMARY
OF
ACUTE
NON­
LETHAL
EFFECTS
IN
ANIMALS
AFTER
INHALATION
EXPOSURE
TO
STYRENE........................................................................
25
TABLE
5:
SUMMARY
OF
RESULTS
ON
STUDIES
OF
CANCER
IN
RATS
TREATED
WITH
STYRENE
*
...........................................................................................................................
35
Styrene
NAC:
02/
2004
v
TABLE
6:
SUMMARY
OF
RESULTS
ON
STUDIES
OF
CANCER
IN
MICE
TREATED
WITH
STYRENE
*
...........................................................................................................................
37
TABLE
7:
EXPOSURE
CONCENTRATIONS
AND
BLOOD
LEVEL
OF
STYRENE
IN
HUMANS
AND
RATS......................................................................................................
44
TABLE
8:
AEGL­
1
VALUES
FOR
STYRENE...........................................................................
51
TABLE
9:
AEGL­
2
VALUES
FOR
STYRENE...........................................................................
55
TABLE
10:
AEGL­
3
VALUES
FOR
STYRENE
.........................................................................
57
TABLE
11:
SUMMARY/
RELATIONSHIP
OF
PROPOSED
AEGL
VALUES.........................
58
TABLE
12:
EXTANT
STANDARDS
AND
GUIDELINES
FOR
STYRENE.............................
60
LIST
OF
FIGURES
FIGURE
1:
SYMPTOM
RATINGS
AT
OR
AFTER
ACUTE
EXPOSURE
OF
HUMANS
TO
STYRENE
................................................................................................................................
8
FIGURE
2:
CONCENTRATION­
RESPONSE
CURVE
FOR
ACUTE
LETHALITY
FOLLOWING
INHALATION
OF
STYRENE
IN
RATS....................................................
18
FIGURE
3:
STYRENE
CONCENTRATION
IN
ARTERIAL
BLOOD
OF
HUMANS
DURING
AND
AFTER
A
2­
HOUR
EXPOSURE
TO
69
PPM
STYRENE
IN
AIR............................
42
FIGURE
4:
OBSERVED
(
CIRCLES)
AND
SIMULATED
CONCENTRATIONS
OF
STYRENE
IN
ARTERIALIZED
CAPILLARY
BLOOD
FROM
TWO
HUMAN
VOLUNTEERS.....
42
FIGURE
5:
STYRENE
CONCENTRATION
IN
BLOOD
OF
RATS
DURING
A
5­
HOUR
EXPOSURE
TO
DIFFERENT
CONCENTRATIONS
OF
STYRENE
IN
AIR..................
43
FIGURE
6:
PATHWAYS
FOR
THE
METABOLISM
OF
STYRENE
IN
HUMANS
AND
RODENTS..............................................................................................................................
47
FIGURE
7:
CATEGORICAL
REPRESENTATION
OF
STYRENE
INHALATION
DATA...
59
Styrene
NAC:
02/
2004
vi
EXECUTIVE
SUMMARY
Styrene
is
a
colorless
or
slightly
yellow,
viscous
liquid,
soluble
in
ethanol,
benzene
and
petroluem
ether
and
slightly
soluble
in
water.
Owing
to
its
volatility,
low
flash
point,
and
the
range
of
explosive
limits
in
air
(
lower:
1.1
%,
upper:
6.3
%
v/
v),
styrene
poses
an
acute
fire
and
explosion
hazard.
Due
to
its
tendency
to
polymerize
at
room
temperature
in
the
presence
of
oxygen
and
to
oxidize
on
exposure
to
light
and
air,
styrene
is
normally
stabilized
by
the
addition
of
<
0.006
­
0.01%
w/
w
tertiary
butylcatechol
(
4­
tert­
butylbenzene­
1,2­
diol)
as
an
inhibitor.
Styrene
is
one
of
the
most
important
monomers
in
industry
worldwide.
It
is
predominantly
used
for
the
production
of
polymers
(
polystyrene
and
copolymers
of
styrene
with
acrylonitrile
and/
or
butadiene).
Worldwide
production
reached
17
945
thousand
tonnes
in
1998.

In
humans,
the
observed
effects
associated
with
acute
exposure
to
styrene
are
irritation
of
eyes
and
mucous
membranes
and
central
nervous
system
(
CNS)
depression.
Limited
data
in
humans
provide
no
evidence
that
(
occupational)
styrene
exposure
causes
lesions
of
the
nasal
epithelia
or
decrements
in
olfactory
function
(
Dalton
et
al.
2003;
Ödkvist
et
al.
1985).
No
data
were
available
indicating
reproductive
or
developmental
effects
of
styrene
in
humans
following
acute
exposure.
Epidemiological
studies
revealed
no
sound
evidence
for
an
association
between
repeated
occupational
exposure
to
styrene
and
reproductive
or
developmental
effects.
Genotoxicity
was
observed
in
human
cells
in
vitro;
in
vivo,
no
data
were
available
with
respect
to
genotoxicity
following
acute
exposure
of
humans.
In
epidemiological
studies,
evidence
for
an
association
of
occupational
exposure
to
styrene
and
genotoxic
effects
were
observed.
With
respect
to
carcinogenicity
in
humans,
in
its
latest
evaluation
IARC
(
2002)
concluded
that
there
is
"
limited
evidence
in
humans
for
the
carcinogenicity
of
styrene"
and,
taking
into
account
the
results
from
animal
carcinogenicity
studies,
that
styrene
is
"
possibly
carcinogenic
to
humans
(
Group
2B)".
Styrene
is
being
reassessed
under
the
IRIS
Program
of
the
US­
EPA,
no
quantitative
carcinogenicity
assessment
for
lifetime
exposure
is
currently
proposed.
US­
EPA
´
s
Office
of
Research
and
Development
has
updated
previous
assessments
on
the
carcinogenic
potential
of
styrene
and
concluded
that
styrene
is
appropriately
classified
as
a
Group
C
(
possible
human
carcinogen)
(
US
EPA
2003).

Animal
studies
were
mostly
carried
out
with
rats
and
mice,
limited
data
are
available
for
guinea
pigs,
hamsters
and
an
unspecified
species
of
monkeys.
As
in
humans,
irritation
and
CNS
effects
are
also
observed
in
animals
following
acute
inhalation
exposure.
In
mice,
RD50
values
for
sensory
irritation
of
156
ppm
­
980
ppm
were
reported.
Signs
indicating
irritation
were
also
reported
in
toxicity
studies
with
rats
at
concentrations
as
low
as
200
ppm,
immediate
irritation
in
rats
was
noted
at
1300
ppm.
CNS­
depression
in
rats
and
mice
was
observed
at
higher
concentrations.
Rats
lost
consciousness
at
2000
ppm
after
5
hours
of
exposure
and
showed
reduced
attention
at
6­
hour
exposures
to
1500
ppm.
In
mice,
signs
of
CNS
depression
during
a
4­
hour
exposure
were
staggered
gait
at
1420
ppm
and
apathy
and
finally
narcosis
at
higher
concentrations
of
2983
and
3766
ppm.
In
rats,
death
was
observed
when
animals
were
exposed
for
4
hours
to
4814
ppm
and
higher
concentrations
(
BASF
1979b).
Death
was
mostly
rapid
due
to
CNS
depression
but
some
delayed
deaths
with
signs
of
pulmonary
lesions
were
observed
in
rats
at
concentrations
also
causing
severe
CNS
effects.
Mice
were
much
more
sensitive
than
rats
(
and,
based
on
a
limited
number
of
data,
guinea
pigs
and
monkeys).
Death
of
mice
was
observed
following
a
single
6­
hour
exposure
to
250
ppm
or
500
ppm.
Also,
at
these
concentrations,
respiratory
toxicity
with
lesions
of
the
nasal
epithelia
and
of
the
bronchioles
were
observed
in
mice
but
not
in
rats.

With
respect
to
developmental
or
reproductive
effects,
no
embryo­/
fetotoxicity
or
malformations
were
observed
in
rats
after
a
single
oral
treatment
on
the
11th
or
17th
day
of
gestation,
respectively.
In
mice,
decreased
postnatal
survival
was
observed
after
signe
oral
administration
of
a
maternally
toxic
dose
on
day
17
of
gestation,
while
no
effect
was
noted
at
a
lower
dose.
Following
repeated
exposure
of
rats
through
gestation
day
6
 
20
to
300
ppm,
an
increased
neonatal
death
rate
and
delayed
postnatal
Styrene
NAC:
02/
2004
vii
development
was
observed
compared
to
pair­
fed
controls.
Fetotoxicity
was
also
seen
in
hamsters
exposed
to
1000
ppm
6
hours/
day
from
gestation
day
6
­
18,
but
not
at
750
ppm.
In
other
studies
with
repeated
oral
or
inhalation
exposure
of
rats,
mice,
and
rabbits,
no
significant
developmental
effects
were
observed.
Styrene
is
genotoxic
in
vitro,
provided
there
is
sufficient
activation
to
styrene
oxide
(
SO),
and
in
vivo.
Data
from
laboratory
animals
indicate
that
styrene
exposure
may
lead
to
the
formation
of
DNA­
adducts,
sister
chromatid
exchange,
and
chromosomal
aberrations.
With
respect
to
carcinogenicity,
no
clear
effect
was
observed
in
rats.
In
mice,
an
increase
of
lung
tumors
was
observed.

Styrene
has
a
pungent,
slightly
sweetish
odor.
The
derivation
of
the
level
of
distinct
odor
awareness
(
LOA)
was
based
on
results
from
human
studies
presented
in
the
report
of
Van
Doorn
et
al.
(
2002)
and
follows
the
guidance
as
described
in
the
same
report.
The
LOA
represents
the
concentration
above
which
it
is
predicted
that
more
than
half
of
the
exposed
population
will
experience
at
least
a
distinct
odor
intensity,
while
about
10
%
of
the
population
will
experience
a
strong
odor
intensity.
The
LOA
should
help
chemical
emergency
responders
in
assessing
the
public
awareness
of
the
exposure
due
to
odor
perception.
For
styrene,
the
calculated
level
of
distinct
odor
awareness
(
LOA)
is
0.54
ppm.

The
AEGL­
1
derivation
is
based
on
irritating
effects
of
styrene
in
humans.
In
a
study
on
psychological
reactions
related
to
chemosensory
irritation,
ratings
for
odor
and
annoyance
increased
similarily
with
increasing
styrene
concentrations
ranging
from
0.5
 
40
ppm,
while
there
was
only
a
marginal
increase
for
irritation.
Effects
sizes
comparing
the
ratings
between
exposure
to
20
ppm
and
preexposure
were
higher
for
odor,
irritation,
and
annoyance.
Effects
sizes
were
also
higher
compared
to
"
clean
air
only"­
exposure.
However,
the
ratings
for
irritation
indicated
only
marginal
effects
in
this
respect
(
Seeber
et
al.
2002).
No
increase
in
irritation
or
headaches
compared
to
control
was
noted
at
20
ppm
in
a
further
study
(
Hake
et
al.
1983).
Subjective
signs
and
symptoms
of
irritation
and
CNS
effects
were
not
negatively
influenced
during
a
6­
hour
exposure
at
25
ppm
or
50
ppm
or
at
50
ppm
with
4
peak
exposures
of
15
minutes
at
100
ppm
(
Ska
et
al.
2003).
At
50
ppm,
a
further
study
indicated
a
slight
increase
in
subjective
symptoms
ratings
for
eye
and
nose
irritation,
headache,
and
fatigue
(
Oltramare
et
al.
1974).
At
100
ppm,
Oltramare
et
al.
(
1974)
further
reported
that
signs
of
irritation
and
of
mild
subjective
CNS
effects
(
headaches,
fatigue,
poor
concentration,
sleepiness)
were
felt
more
often
than
at
50
ppm.
Complaints
of
mild
eye
and
throat
irritation
at
99
ppm
in
one
test
but
not
in
another
at
116
ppm
were
reported
by
Stewart
et
al.
(
1968).
Complaints
of
eye
and
nose
irritation
were
frequent
at
about
200
ppm
(
Oltramare
et
al.
1974;
Stewart
et
al.
1968).

A
concentration
of
20
ppm
(
Seeber
et
al.
2003)
was
selected
to
derive
AEGL­
1.
Because
this
concentration
represents
a
NOAEL
for
local
(
as
well
as
CNS)
effects
and
in
other
studies
effects
at
50
ppm
and
100
ppm
were
only
weak
or
absent,
an
intraspecies
factor
of
1
is
applied.
The
value
of
20
ppm
was
used
for
all
timepoints
since
slight
irritation
and
subjective
discomfort
that
were
reported
at
higher
concentrations
did
not
increase
within
several
hours
of
exposure.

The
derivation
of
AEGL­
2
is
based
on
human
studies.
Irritation
and
CNS
effects
have
to
be
considered
for
the
derivation
of
AEGL­
2.
Nasal
and
mild
eye
irritation
were
reported
by
volunteers
exposed
to
376
ppm
(
Stewart
et
al.
1968).
In
their
study
of
styrene
exposed
workers,
Götell
et
al.
(
1972)
reported
that
they
themselves
suffered
from
immediate
lacrymation
and
irritation
of
the
nasopharynx
when
exposed
to
300
 
400
ppm,
and
concentrations
of
500
 
800
ppm
caused
irritation
intolerable
to
the
investigators
within
1
or
2
minutes.
Strong
eye
and
nasal
irritation
was
also
reported
by
volunteers
exposed
to
concentrations
 
600
ppm
(
Carpenter
et
al.
1944;
Wolf
et
al.
1956).

With
respect
to
effects
on
the
CNS,
a
6­
hour
exposure
at
50
ppm
with
4
repeated
15­
minute
peaks
at
100
ppm
had
no
negative
influence
on
performance
to
neuropsychological
tests
(
Ska
et
al.
2003).
Styrene
NAC:
02/
2004
viii
At
99
ppm,
intermittent
difficulties
in
performing
a
modified
Romberg
test
were
observed
in
3/
6
subjects
exposed
for
7
hours
with
a
30­
minute
break
in
between.
Other
tests
on
coordination
and
on
manual
dexterity
were
normal,
and
no
effects
were
noted
at
the
end
of
exposure.
No
CNS
effects
were
seen
in
another
experiment
with
116
ppm
exposure
for
2
hours
or
216
ppm
for
1
hour
in
the
same
study
(
Stewart
et
al.
1968).
Headaches,
but
no
effects
on
equilibrium
and
cognitive
function
tests
were
noted
in
male
and
female
volunteers
at
repeated
exposures
to
100
and
125
ppm
for
at
least
one
hour
(
Hake
et
al.
1983).
Oltramare
et
al.
(
1974)
noted
slight
difficulties
in
balance
performance
at
50
 
200
ppm
(
1.5
hours),
but
there
was
no
concentration­
response,
and
slight
difficulties
in
balance
performance
at
200
ppm
(
1
hour),
but
the
variation
of
data
was
large.
No
effects
on
simple
and
choice
reaction
time
was
seen
following
exposure
to
250
ppm
for
30
minutes.
However,
when
the
concentration
was
raised
to
350
ppm
for
30
minutes
directly
afterwards,
both
simple
and
choice
reaction
time
were
increased
(
Gamberale
and
Hultengren
1974).
More
pronounced
effects
were
observed
during
exposure
to
376
ppm
for
one
hour:
One
subject
complained
of
nausea
that
persisted
one
hour
after
the
end
of
exposure,
2
subjects
had
a
feeling
of
being
inebriated,
3
of
5
subjects
exposed
were
unable
to
normally
perform
a
modified
Romberg
test,
and
also
3
subjects
had
significant
decrements
in
other
tests
of
coordination
and
manual
dexterity
(
Stewart
et
al.
1968).
In
a
toxicokinetic
study,
2
subjects
were
exposed
to
386
ppm
styrene
for
2
hours
while
performing
light
physical
exercise
of
50
W
(
Löf
and
Johanson
1993).
In
that
study,
no
information
was
presented
as
to
the
presence
or
absence
of
subjective
or
objective
signs
of
intoxication
or
irritation.
However,
it
may
reasonably
be
assumed
that
no
severe
CNS
effects
will
have
occurred
in
such
a
study.
At
higher
concentrations,
the
irritation
becomes
very
strong
(
see
above),
and
only
one
controlled
study
was
located
that
was
conducted
at
this
level
(
Carpenter
et
al.
1944).
In
this
study,
2
subjects
exposed
to
800
ppm
for
4
hours
suffered
from
listlessness,
drowsiness,
impairment
of
balance,
and,
after
cessation
of
exposure,
muscular
weakness
and
unsteadiness
with
inertia
and
depression.
A
"
steadiness
test"
measuring
manual
dexterity
indicated
a
marked
decreased
of
performance
compared
to
pre­
exposure
level.
Besides
CNS­
depression,
the
subjects
complained
of
eye
and
throat
irritation.

The
AEGL­
2
is
based
on
the
CNS
effects
observed
in
humans
following
exposure
to
376
ppm
for
1
hour:
nausea
in
one
subject;
feeling
of
being
inebriated
in
two,
and
unability
to
normally
perform
the
modified
Romberg
test
and
significant
decrements
in
other
tests
of
coordination
and
manual
dexterity
in
three
of
five
subjects
(
Stewart
et
al.
1968).
The
effects
described
address
a
level
of
CNS
depression
that
seems
still
below
a
level
for
an
impairment
of
the
ability
to
escape
and
therefore
a
concentration
of
376
ppm
is
considered
a
NOAEL.
However,
this
level
is
close
to
concentrations
causing
intolerable
irritation
in
humans
that
may
limit
the
ability
to
escape
and
thus
are
above
AEGL­
2.

Generally,
for
volatile
substances
with
CNS­
depressant
effects
an
intraspecies
factor
of
3
is
applied
to
account
for
sensitive
individuals
because
the
effective
concentration
range
does
not
differ
more
than
2­
3fold
between
individuals.
In
case
of
styrene,
it
must
be
taken
into
account
that
physical
activity
has
a
marked
effect
on
the
uptake
of
styrene
and
its
level
in
blood.
In
the
studies
used
to
derive
AEGL­
2,
the
subjects
were
at
rest.
In
controlled
studies,
the
observed
increase
of
styrene
in
arterial
blood
at
exposure
to
about
150
ppm
styrene
was
approximately
3fold
when
the
physical
activity
was
increased
from
rest
to
light
exercise
(
50
W),
5fold
at
moderate
exercise
(
100
W),
and
10fold
at
heavy
exercise
(
150
W)
(
Astrand
1975).
Therefore,
it
could
be
argued
that
an
intraspecies
uncertainty
factor
of
10
to
account
for
sensitive
subgroups
would
be
necessary
to
protect
individuals
at
heavy
physical
exercise.
Application
of
a
factor
of
10
would
lead
to
a
1­
hour
AEGL­
2
of
38
ppm
and
similar
values
at
longer
time
periods.
On
the
other
hand,
the
following
two
points
which
indicate
that
a
factor
of
3
is
justified,
are
believed
to
outweigh
the
above
rationale:
Firstly,
due
to
physiological
limitations,
heavy
physical
exercise
(
150
W)
cannot
be
performed
continuously
for
longer
periods
of
time.
Therefore,
it
is
unrealistic
to
consider
an
exposure
scenario
with
heavy
exercise
for
one
or
several
hours.
In
contrast,
light
exercise
(
50
W)
may
be
performed
over
a
longer
period
of
time.
In
this
case,
the
increase
of
the
styrene
concentration
in
blood
will
be
about
3fold
which
is
Styrene
NAC:
02/
2004
ix
within
the
range
of
an
uncertainty
factor
of
three.
Secondly,
an
AEGL­
2
value
in
the
range
of
38
ppm
as
mentioned
above
would
be
in
conflict
with
styrene
exposure
data
at
occupational
workplaces.
At
workplaces,
such
concentrations
are
or
were
frequently
observed
(
IARC
2002)
without
workers
showing
signs
of
CNS
depression
that
would
have
limited
their
ability
to
escape.

Therefore,
an
intraspecies
uncertainty
factor
of
3
is
considered
adequate
to
protect
sensitive
subgroups
including
groups
exposed
to
styrene
during
longer
periods
of
light
exercise.
This
leads
to
a
value
of
130
ppm
as
AEGL­
2
for
1
hour.

This
experimentally
derived
exposure
value
was
scaled
to
shorter
periods
of
time
using
the
equation
cn
x
t
=
k
(
Ten
Berge
et
al.
1986).
In
accordance
with
NRC
(
2001),
a
default
of
n
=
3
for
shorter
periods
of
time
(
30
minutes
and
10
minutes)
was
applied,
due
to
the
lack
of
suitable
experimental
data
for
deriving
the
concentration
exponent.
The
"
n"
value
of
1.2
used
for
calculations
of
AEGL­
3
(
see
below)
was
not
used
for
AEGL­
2
for
following
reasons:
Firstly,
the
exponent
was
derived
from
lethality
studies
in
which
delayed
mortality
was
observed
that
was
not
related
to
narcotic
effects
on
the
CNS
(
which
are
relevant
for
AEGL­
2)
but
probably
to
pulmonary
lesions
observed
at
these
very
high
concentrations
(
in
addition
to
CNS
effects
which
are
the
major
cause
of
death).
Secondly,
toxicokinetics
at
high
exposure
concentrations
over
several
hours
of
exposures
(
as
in
the
lethality
studies)
is
different
from
that
at
lower
concentrations
for
shorter
time
periods.

Toxicokinetic
studies
with
humans
exposed
to
styrene
concentrations
at
70
 
200
ppm
show
that
most
of
the
increase
of
the
styrene
concentration
in
blood
is
seen
during
the
first
30
minutes
of
exposure
and
that
there
is
no
or
very
little
increase
at
1
 
3
hours
at
these
concentrations.
Therefore,
no
additional
extrapolation
is
necessary
and
the
AEGL­
2
of
130
ppm
derived
for
1
hour
is
applied
to
longer
periods
of
time.

The
AEGL­
3
values
are
derived
from
a
lethality
study
with
rats
(
BASF
1979b).
In
rats,
exposure
to
high
concentrations
of
styrene
leads
to
progressive
CNS
depression
with
narcosis
and,
finally,
death.
At
concentrations
leading
to
severe
CNS
effects,
delayed
deaths
with
pulmonary
lesions
were
also
described
in
these
studies.
In
humans,
the
acute
effects
on
the
CNS
are
well
described.
However,
no
reports
of
lethal
intoxications
following
styrene
exposure
were
identified
in
the
literature;
therefore,
it
is
not
known
if
the
pulmonary
lesions
observed
in
rats
may
also
occur
in
humans
exposed
to
life­
threatening
or
potentially
lethal
concentrations
of
styrene.

For
a
conservative
approach,
data
from
studies
with
rats
taking
into
account
delayed
deaths
with
pulmonary
lesions
were
used
to
derive
AEGL­
3.
From
the
data
of
the
4­
hour
exposure
study
of
BASF
(
1979b),
a
benchmark
calculation
was
performed
with
the
lethality
data
using
different
models.
A
BMDL05
for
female
rats
of
3409
ppm
(
rounded
to
3400
ppm)
was
used
as
a
starting
point
to
derive
AEGL­
3.

A
total
uncertainty
factor
of
10
was
applied.
This
total
factor
may
formally
be
split
up
into
an
interspecies
factor
of
3
and
an
intraspecies
factor
also
of
3.
For
volatile
solvents
like
styrene
with
a
CNSdepressant
effect,
an
interspecies
uncertainty
factor
of
3
has
been
applied
in
the
derivation
of
AEGL
for
several
substances.
This
is
based
on
the
similarity
of
effects
manifested
in
rodents
compared
to
humans.
In
case
of
styrene,
limited
data
indicate
no
gross
differences
in
the
concentration
of
styrene
in
blood
between
rats
and
humans.
According
to
a
toxicokinetic
model,
at
concentrations
exceeding
200
ppm
styrene
in
air,
the
non­
steady­
state
concentration
of
styrene
in
blood
of
humans
(
calculated
for
6
hours
of
exposure)
will
always
be
lower
than
that
in
blood
of
rats
(
Ramsey
and
Andersen
1984).
Styrene
levels
in
human
blood
were
in
accordance
with
this
model
up
to
376
ppm
in
air,
however,
no
experimental
human
data
are
available
for
validation
of
the
model
at
higher
concentrations.
Styrene
NAC:
02/
2004
x
An
intraspecies
uncertainty
factor
of
3
was
applied
to
account
for
sensitive
individuals
since
the
threshold
for
CNS
impairment
is
not
expected
to
vary
much
among
individuals.
As
in
case
of
the
derivation
of
AEGL­
2,
an
intraspecies
uncertainty
factor
of
3
is
considered
adequate
to
protect
sensitive
subgroups
including
groups
exposed
to
styrene
during
longer
periods
of
light
exercise.

Extrapolation
was
made
to
the
relevant
AEGL
time
points
of
30
minutes
and
1
hour
using
the
relationship
Cn
x
t
=
k
with
a
value
of
n
=
1.2
which
was
derived
from
extrapolation
of
the
LC50
in
rats
for
4­
and
6
hours
(
BASF
1979b;
Bonnet
et
al.
1982a).
The
10­
minutes
AEGL­
3
was
assigned
the
same
value
as
that
for
the
30­
minutes
AEGL­
3
as
it
was
considered
inappropriate
to
extrapolate
from
an
experimental
period
of
4
hours
to
10
minutes.
The
8­
hour
AEGL­
3
was
assigned
the
same
value
as
that
for
the
4­
hour
AEGL­
3
as
toxicokinetic
data
indicate
that
there
is
at
most
little
increase
of
internal
dose
after
4
hours
of
exposure;
moreover,
lower
values
which
would
be
derived
by
default
calculations
are
not
supported
by
toxicological
data
for
humans.

Individual
cases
of
respiratory
sensitization
to
styrene
were
described.
Taking
into
account
the
wide
use
of
styrene
both
in
industry
and
in
do­
it­
yourself
products,
sensitization
seems
to
be
an
exceptionally
rare
event.
Although
the
risk
of
sensitization
following
a
single
exposure
at
AEGL
is
considered
negligible,
individuals
already
sensitized
to
styrene
may
not
be
able
to
tolerate
styrene
concentrations
that
are
without
effect
in
non­
sensitized
individuals
and
may
not
be
protected
by
the
AEGL
developed
for
styrene
in
this
TSD.

SUMMARY
TABLE
OF
AEGL
VALUES
FOR
STYRENE
a
Classification
10­
Minute
30­
Minute
1­
Hour
4­
Hour
8­
Hour
Endpoint
(
Reference)

AEGL­
1
(
Nondisabling)
20
ppm
(
85
mg/
m
³
)
20
ppm
(
85
mg/
m
³
)
20
ppm
(
85
mg/
m
³
)
20
ppm
(
85
mg/
m
³
)
20
ppm
(
85
mg/
m
³
)
NOAEL
for
slight
irritation
(
Seeber
et
al.
2002)

AEGL­
2
(
Disabling)
230
ppm
(
980
mg/
m
³
)
160
ppm
(
680
mg/
m
³
)
130
ppm
(
550
mg/
m
³
)
130
ppm
(
550
mg/
m
³
)
130
ppm
(
550
mg/
m
³
)
CNS
effects
in
humans
(
Gamberale
and
Hultengren
1974;
Stewart
et
al.
1968)

AEGL­
3
(
Lethality)
1900
ppm
*
(
8090
mg/
m
³
)
1900
ppm
*
(
8090
mg/
m
³
)
1100
ppm
(
4690
mg/
m
³
)
340
ppm
(
1450
mg/
m
³
)
340
ppm
(
1450
mg/
m
³
)
No
lethality
in
rats
(
BASF
1979b)

a:
Since
liquid
styrene
is
an
eye
irritant,
eye
contact
must
be
avoided.
*:
The
lower
explosive
limit
(
LEL)
of
styrene
in
air
is
1.1
%
(
11,000
ppm).
The
AEGL­
3
value
of
1900
ppm
(
8090
mg/
m
³
)
for
10
minutes
and
30
minutes
are
higher
than
1/
10
of
the
LEL.
Therefore,
safety
considerations
against
hazard
of
explosion
must
be
taken
into
account.

References
Astrand,
I.
1975.
Uptake
of
solvents
in
the
blood
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tissues
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man.
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review.
Scandinavian
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Environment
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Health
1:
199­
218.

BASF.
1979b.
Bericht
über
die
Bestimmung
der
akuten
Inhalationstoxizität
LC50
von
Styrol
als
Dampf
bei
4stündiger
Exposition
an
Sprague­
Dawley­
Ratten.
Unveröfffentlichte
Untersuchung.
[
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on
the
Styrene
NAC:
02/
2004
xi
determination
of
the
acute
inhalation
toxicity
LC50
of
styrene
as
vapor
following
a
4­
hour
exposure
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Sprague­
Dawley
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study.]
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AG,
Ludwigshafen,
Germany.

Bonnet,
P.,
Y.
Morele,
G.
Raoult,
D.
Zissu,
and
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Gradiski.
1982a.
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de
la
concentration
léthales50
des
principaux
hydrocarbures
aromatiques
chez
le
rat.
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des
Maladies
Professionnelles
de
Medecine
du
Travail
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de
Securite
Sociale
43:
261­
265.

Carpenter,
C.
P.,
H.
F.
Jr.
Smyth,
and
D.
C.
Pozzani.
1944.
Studies
on
the
inhalation
of
1:
3­
butadiene;
with
a
comparison
of
its
narcotic
effect
with
benzol,
toluol,
and
styrene,
and
a
note
on
the
elimination
of
styrene
by
the
human.
Journal
of
Industrial
Hygiene
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26:
69­
78.

Dalton,
P.,
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Cowart,
D.
Dilks,
M.
Gould,
P.
S.
Lees,
A.
Stefaniak,
and
E.
Emmett.
2003.
Olfactory
function
in
workers
exposed
to
styrene
in
the
reinforced­
plastics
industry.
American
Journal
of
Industrial
Medicine
44:
1­
11.

Gamberale,
F.
and
M.
Hultengren.
1974.
Exposure
to
styrene.
II.
Psychological
functions.
Work,
Environment
and
Health
11:
86­
93.

Götell,
P.,
O.
Axelson,
and
B.
Lindelöf.
1972.
Field
Studies
on
Human
Styrene
Exposure.
Work,
Environment
and
Health
9:
76­
83.

Hake,
C.
L.,
R.
D.
Stewart,
A.
Wu,
S.
Graff,
H.
V.
Forster,
W.
H.
Keeler,
A.
J.
Lebrun,
P.
E.
Newton,
and
R.
J.
Soto.
1983.
Styrene
­
Development
of
a
Biologic
Standard
for
the
Industrial
Worker
by
Breath
Analysis.
NIOSH­
MCOW­
ENVM­
STY­
77­
2.
Medical
College
of
Wisconsin,
Milwaukee.
Cited
in
NIOSH
(
1983).

IARC.
2002.
Some
Traditional
Herbal
Medicines,
some
Mycotoxins,
Naphthalene
and
Styrene.
Summary
of
Data
Reported
and
Evaluation.
IARC
Monographs
on
the
Evaluation
of
Carcinogenic
Risks
to
Humans
82,
p.
437­
550.
IARC
(
International
Agency
for
Research
on
Cancer),
WHO
(
World
Health
Organization),
Lyon,
France.

Löf,
A.
and
G.
Johanson.
1993.
Dose­
dependent
kinetics
of
inhaled
styrene
in
man.
IARC
Scientific
Publications
89­
99.

NIOSH.
1983.
Criteria
for
a
Recommended
Standard
­
Occupational
Exposure
to
Styrene.
DHHS
(
NIOSH)
Report.
83­
119.
National
Institute
for
Occupational
Safety
and
Health
(
NIOSH),
Cincinnati,
OH.

Ödkvist,
L.
M.,
C.
Edling,
and
H.
Hellquist.
1985.
Influence
of
vapours
on
the
nasal
mucosa
among
industry
workers.
Rhinology
23:
121­
127.

Oltramare,
M.
E.,
E.
Desbaumes,
C.
Imhoff,
and
W.
Michiels.
1974.
Toxicologie
du
styrene
monomere
[
Toxicology
of
Monomeric
Styrene
­
Experimental
and
Clinical
Studies
on
Man.].
Editions
Medicine
et
Hygienique.
Geneva,
Switzerland.
Cited
in
NIOSH
(
1983)
and
WHO
(
1983).

Seeber,
A.,
C.
van
Thriel,
K.
Haumann,
E.
Kiesswetter,
M.
Blaszkewicz,
and
K.
Golka.
2002.
Psychological
reactions
related
to
chemosensory
irritation.
International
Archives
of
Occupational
and
Environmental
Health
75:
314­
325.
Styrene
NAC:
02/
2004
xii
Ska,
B.,
A.
Vyskocil,
R.
G.
Tardif,
G.
Carrier,
R.
Thuot,
K.
Muray,
and
C.
Viau.
2003.
Effects
of
peak
concentrations
on
the
neurotoxicity
of
styrene
in
volunteers.
Human
and
Experimental
Toxicology
22:
407­
415.

Stewart,
R.
D.,
H.
C.
Dodd,
E.
D.
Baretta,
and
A.
W.
Schaffer.
1968.
Human
exposure
to
styrene
vapor.
Archives
of
Environmental
Health
16:
656­
662.

US
EPA.
2003.
Technology
Transfer
Network
Air
Toxics
Website.
Styrene.
Air
Toxics
Website.
U.
S.
Environmental
Protection
Agency,
Washington,
DC.
http://
www.
epa.
gov/
ttn/
atw/
htlhef/
styrene.
htm.

van
Doorn,
R.,
M.
W.
Ruijten,
and
T.
van
Harreveld.
2002.
Guidance
for
the
Application
of
Odor
in
Chemical
Emergency
Response.
Version
2.1;
August,
29.,
2002.
Presented
at
the
NAC/
AEGL­
Meeting
September
2002,
Washington
DC.

WHO.
1983.
Styrene.
Environmental
Health
Criteria
(
EHC)
26.
International
Programme
on
Chemical
Safety
(
IPCS);
World
Health
Organization,
Geneva,
Switzerland.

Wolf,
J.
R.,
V.
K.
Rowe,
D.
D.
McCollister,
R.
L.
Hollingsworth,
and
F.
Oyen.
1956.
Toxicological
studies
of
certain
alkylated
benzenes
and
benzene.
Experiments
on
laboratory
animals.
Archives
of
Industrial
Health
14:
387­
398.
Styrene
NAC:
02/
2004
1
1
INTRODUCTION
Styrene
is
a
colorless
or
slightly
yellow,
viscous
liquid.
It
is
slightly
soluble
in
water,
soluble
in
ethanol
and
very
soluble
in
benzene
and
petroleum
ether.
Due
to
its
tendency
to
polymerize
at
room
temperature
in
the
presence
of
oxygen
and
to
oxidize
on
exposure
to
light
and
air,
styrene
is
normally
stabilized
by
the
addition
of
<
0.006
­
0.01%
w/
w
tertiary
butylcatechol
(
4­
tert­
butylbenzene­
1,2­
diol)
as
an
inhibitor
(
WHO
1983).

Pure
styrene
has
a
pungent,
slightly
sweetish
odor.
However,
oxidation
may
lead
to
the
formation
of
peroxides,
certain
aldehydes
and
ketones
giving
a
sharp,
penetrating,
disagreeable
odor.
When
emitted
into
the
air,
its
half­
time
is
estimated
to
be
about
2
hours,
and
chemical
transformation
products
include
benzaldehyde
and
formaldehyde,
both
of
which
are
odorous
air
pollutants
(
WHO
2000).

Styrene
is
one
of
the
most
important
monomers
in
industry
worldwide.
The
first
step
in
its
industrial
production
is
the
catalytic
alkylation
of
benzene
with
ethylene
leading
to
ethylbenzene.
In
the
second
step,
ethylbenzene
is
dehydrogenated
to
styrene.
In
an
alternative
process,
styrene
is
formed
as
a
coproduct
in
the
synthesis
of
propylene
oxide
from
ethylbenzene
and
propene
via
ethylbenzene
hydroperoxide
and
1­
phenylethanol
(
WHO
1983).
Purified
products
typically
are
99.7%
to
greater
than
99.9%
w/
w
styrene
with
less
than
0.1
%
ethylbenzene,
cumene,
phenylpropene,
phenyl
acetate
and
p­
xylene.

Styrene
is
predominantly
used
for
the
production
of
polymers
(
polystyrene,
copolymers
of
styrene
with
acrylonitrile
and/
or
butadiene)
that
find
wide
application
in
latex
paints
and
coatings,
synthetic
rubbers,
polyesters
and
styrene­
alkyd
coatings.
Styrene
is
a
HPV
(
high
production
volume)
chemical
with
a
worldwide
production
of
17
945
thousand
tonnes
in
1998.
Small
amounts
of
styrene
can
be
found
in
gum
exudate
from
the
damaged
trunk
of
certain
trees,
probably
being
produced
by
decomposition
of
cinnamic
acid
derivatives
that
are
present
in
such
exudates
in
large
quantities.
Styrene
also
occurs
in
many
agricultural
products
and
foods,
however,
it
is
not
clear
whether
styrene
is
naturally
produced
within
plants
(
IARC
2002).

Owing
to
its
volatility,
low
flash
point,
and
the
range
of
explosive
limits
in
air
(
lower:
1.1
%,
upper:
6.3
%
v/
v),
styrene
poses
an
acute
fire
and
explosion
hazard.
Chemical
and
physical
properties
of
styrene
are
presented
in
Table
1.
Styrene
NAC:
02/
2004
2
TABLE
1:
CHEMICAL
AND
PHYSICAL
PROPERTIES
Parameter
Data
Reference
Synonyms
Vinylbenzene,
phenylethene,
ethenylbenzene,
cinnamene
WHO
1983
Chemical
formula
C8H8
Molecular
weight
104.14
g/
mol
WHO
1983
CAS
Reg.
No.
100­
42­
5
ATSDR
1992
Physical
state
Liquid
at
room
temperature
Weast
1973
Solubility
300
mg/
l
in
water
(
at
20
°
C),
soluble
in
alcohol,
ether,
acetone,
miscible
with
benzene
and
petrol
ether
Weast
1973;
WHO
1983
Vapor
pressure
3.1
hPa
(
at
10
°
C),
6.67
hPa
(
at
20
°
C),
8.67
hPa
(
at
25
°
C),
13.3
hPa
(
at
35
°
C)
ATSDR
1992;
NIOSH
1983;
WHO
1983
Vapor
density
(
air
=
1)
3.6
Liquid
density
(
g/
cm
³
)
0.9060
(
at
20
°
C)
Weast
1973
Melting
point
­
30.63
°
C
Weast
1973
Boiling
point
145.2
°
C
(
at
1013
hPa)
Weast
1973
Explosive
limits
in
air
1.1
 
6.3
%
ATSDR
1992
Flash
point
(
closed
cup)
31
°
C
ATSDR
1992
Autoignition
temperature
490
°
C
ATSDR
1992
Conversion
factors
(
at
25
°
C)
1
ppm
=
4.26
mg/
m
³
1
mg/
m
³
=
0.234
ppm
Calculated
according
to
NRC
2001
Styrene
NAC:
02/
2004
3
2
HUMAN
TOXICITY
DATA
2.1
Acute
Lethality
No
reports
of
lethal
intoxication
following
styrene
exposure
were
located
in
the
literature.

2.2
Nonlethal
Toxicity
2.2.1
Case
Reports
The
investigators
of
a
field
study
on
styrene
exposure
of
workers
noted
that
they
could
not
withstand
styrene
concentrations
of
500
 
800
ppm
for
more
than
1
 
2
minutes,
whereas
the
workers
exposed
to
this
level
complained
of
only
minor
to
moderate
irritation
of
eyes
and
nasopharynx.
The
authors
further
report
that
they
themselves
(
five
unadapted
persons)
suffered
from
lacrymation
and
irritation
of
the
nasopharynx
at
about
300
 
400
ppm
(
Götell
et
al.
1972).

By
degassing
the
tank
of
a
ship
on
a
river,
styrene
was
blown
into
the
surrounding
air
without
sufficient
dilution.
15
employees
of
a
nearby
power
plant
and
3
river
police
men
who
were
exposed
to
an
unknown
concentration
of
styrene
complained
of
immediate
eye
irritation
and
tickle
in
the
throat,
dizziness,
headache
and
nausea
(
Hahn
et
al.
2000).

After
using
a
polyester
resin
canoe
building
kit,
a
36­
year
old
man
twice
suffered
from
neurologic
symptoms
(
MacFarlane
et
al.
1984).
The
work
had
been
carried
out
in
an
unventilated
shed
for
about
4
 
5
hours
during
which
styrene
evaporated
from
the
construction
kit.
The
man
developed
severe
postural
hypotension,
neurological
signs
(
slurred
speech,
nystagmus,
limb
ataxia)
and
conjunctivitis.

Moscato
et
al.
(
1987)
described
two
cases
of
workers
employed
in
plastics
factories
that
had
bronchial
asthma
or
runny
nose,
dry
irritating
cough
and
chest
tightness.
They
were
exposed
to
styrene
and
ethyl
benzene
and
one
of
them
to
polyester
resin.
However,
specific
inhalation
challenges
revealed
an
immediate
bronchospastic
response
only
after
provoked
inhalation
exposure
to
styrene
(
15
ppm
for
15
minutes).
In
both
subjects,
symptoms
completely
disappeared
after
changing
their
job.
A
further
case
of
asthma
in
a
subject
occupationally
exposed
to
styrene
and
showing
a
positive
reaction
to
styrene
in
a
provoked
exposure
test
was
reported
by
Hayes
et
al.
(
1991).
A
case
of
skin
dermatitis
following
dermal
exposure
to
styrene
was
reported
by
Sjöborg
et
al.
(
1982),
skin
patch
tests
revealed
a
strong
reaction
to
styrene
and
a
cross­
reaction
to
vinyl
toluene,
but
a
weak
one
to
benzoyl
peroxide
(
used
in
hardeners
for
styrene­
based
plastics)
and
no
reaction
to
styrene
polymerization
inhibitors
and
typical
styrene
impurities.

Non­
inhalation
exposure
Repare
of
a
water
tank
led
to
contamination
of
tap
water
with
styrene
and
subsequent
oral
and
inhalation
exposure
(
Arnedo­
Pena
et
al.
2003).
Residents
of
27
apartments
in
two
buildings
using
the
contaminated
water
were
contacted.
A
questionnaire
on
subjective
symptoms
was
administered
to
84
out
of
93
persons
living
in
affected
apartments
at
the
time
of
the
accident.
Styrene
measured
in
samples
of
water
collected
two
days
after
the
accident
reached
concentrations
up
to
900
µ
g/
L.
Symptoms
were
reported
by
46
persons,
most
frequently
irritation
of
the
throat
(
26%),
nose
(
19%),
eyes
(
18%)
and
skin
(
14%).
General
gastrointestinal
symptoms
were
observed
with
11%
reporting
abdominal
pain
and
7%
diarrhea.
The
factors
most
strongly
associated
with
symptoms
were
drinking
tap
water,
exposure
to
vapors
from
the
basement
and
eating
foods
prepared
with
tap
water.
All
residents
in
the
ground
floor
reported
symptoms.
Styrene
NAC:
02/
2004
4
2.2.2
Occupational
exposure
A
great
number
of
studies
on
workers
with
occupational
exposure
to
styrene
in
different
workplaces
have
been
carried
out.
These
studies
have
been
repeatedly
reviewed
and
summarized
(
ACGIH
1997;
ATSDR
1992;
Cohen
et
al.
2002;
DFG
1987;
Government
Canada
1993;
IARC
2002;
OEHHA
1999;
Sherrington
and
Routledge
2001;
US
EPA
1998;
WHO
1983;
WHO
2000).
Workers
are
exposed
to
styrene
in
a
number
of
industries,
e.
g.
in
the
production
of
styrene
and
styrene
polymers.
In
the
fabrication
of
reinforced­
polyester
plastics
composites,
8­
hour
average
samples
in
breathing
zones
often
exceed
styrene
concentrations
of
100
ppm
(
IARC
2002).
Here,
the
highest
exposure
concentrations
were
observed
in
chopper
gun
operators
where
8­
hour
mean
concentrations
in
personal
breathing
zone
of
564
mg/
m
³
(
range
307
 
938
mg/
m
³
)
(
132
ppm;
range
72
 
219
ppm)
were
measured
(
Truchon
et
al.
1992).
In
previous
studies
on
workers
in
the
manufacture
of
reinforced
plastics,
8­
hours
TWA
concentrations
in
the
breathing
zone
of
up
to
292
ppm
were
reported,
with
peaks
of
about
1500
ppm
during
shorter
periods
of
work
for
about
5
 
10
minutes
(
Götell
et
al.
1972).

In
workers
exposed
to
styrene,
central
and
peripheral
nervous
systems
effects
have
been
observed.
Especially,
reversible
decrease
in
color
discrimination
has
been
described
in
many
studies.
Decrements
of
auditory
function
(
threshold
for
hearing
at
high
frequencies,
hearing
acuity)
was
also
observed
in
several
smaller
cross­
sectional
studies,
however,
in
the
largest
study
on
workers
in
the
glass
fibre­
reinforced
plastics
industry,
no
evidence
was
observed
that
exposure
to
styrene
had
an
effect
on
hearing
acuity
when
both
lifetime
styrene
exposure
and
noise
were
taken
into
account.
Studies
of
effects
on
the
immune
and
hematopoetic
system,
liver,
and
kidney
did
not
reveal
consistent
changes
(
IARC
2002).
Generally,
in
these
studies
effects
on
workers
with
long­
term
exposure
to
styrene
were
investigated.
A
detailed
description
of
the
findings
from
these
studies
is
beyond
the
scope
of
this
document
because
they
do
not
provide
data
that
can
be
used
for
the
derivation
of
AEGL.
Therefore,
only
studies
are
described
here
in
which
effects
following
acute
occupational
exposure
to
styrene
were
investigated.

Acute
behavioral
effects
and
symptoms
of
exposure
to
styrene
were
investigated
in
a
crosssectional
study
(
Edling
and
Ekberg
1985).
12
workers
(
mean
age
30
years)
with
a
mean
exposure
to
styrene
of
2.5
years
took
part
in
the
study.
Neuropsychiatric
symptoms
(
questionnaire)
and
a
reaction
time
test
were
conducted
after
an
exposure
free
intervall
of
at
least
24
hours
before
and
after
the
morning
and
the
afternoon
shift.
A
reference
group
of
10
non­
exposed
men
was
available
for
the
morning
shift.
The
mean
8­
hour
TWA
of
breathing
zone
personal
samples
was
43
±
28
mg/
m
³
(
10
±
6.5
ppm)
in
the
morning
shift
and
54
±
37
mg/
m
³
(
13
±
9
ppm)
in
the
afternoon
shift.
No
significant
differences
in
neuropsychiatric
symptoms
and
reaction
time
were
observed
between
pre­
and
postshift
evaluations
and
between
exposed
and
controls.

Acute
(
and
chronic)
effects
of
styrene
on
the
nervous
system
were
investigated
in
a
further
crosssectional
study
(
Triebig
et
al.
1989).
A
total
of
36
workers
from
companies
handling
polyester
resin
materials
for
1
 
16
(
median:
7)
years
and
two
control
groups
were
each
examined
on
a
Monday.
One
control
group
formed
to
compare
acute
effects
consisted
of
20
men
from
two
companies
with
no
exposure
to
neurotoxic
chemicals.
To
compare
chronic
effects,
a
second
control
group
was
formed
by
"
one
to
one
matching"
with
respect
to
age,
socio­
economic
status,
and
pre­
exposure
intelligence
level.
Ambient
air
monitoring
using
active
sampling
(
short
time)
and
passive
samplers
(
long
time)
showed
styrene
in
air
of
3
 
251
ppm
(
median:
18
ppm)
and
140
 
600
ppm
during
lamination
of
the
inside
of
boats.
Clinical
examination
revealed
no
signs
or
symptoms
of
peripheral
neuropathy
or
encephalopathy.
Acute
eye
irritation
was
noted
after
exposure
to
about
200
ppm
or
more.
Neurobehavioural
tests
showed
neither
significant
differences
in
acute
effects
between
the
two
groups
nor
between
pre­
and
postshift
testing
nor
significant
differences
in
relevant
neurobehavioural
variables
between
the
styrene
workers
and
controls.
Styrene
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5
Limited
data
on
the
effects
of
styrene
vapors
on
the
nasal
mucosa
are
available
from
a
crosssectional
study
(
Ödkvist
et
al.
1985).
11
ship
builders
(
mean
age
39
years,
range
26
 
57
years)
exposed
to
styrene
for
a
mean
of
7
years
(
range
1
 
16
years)
took
part
in
the
study.
Air
levels
in
the
plant
were
in
the
range
of
200
 
250
mg/
m
³
(
47
 
59
ppm)
(
no
details
reported).
25
men
matched
for
age
and
smoking
habits
and
without
industrial
exposure
served
as
controls.
Nasal
biopsies
were
taken
from
the
mucosa
of
the
inferior
turbinates,
and
morphological
findings
were
graded
according
to
a
scoring
system
evaluating
histological
characteristics.
No
statistically
significant
differences
between
the
mean
scores
of
both
groups
were
found.

2.2.3
Experimental
Studies
Two
male
subjects
were
exposed
to
800
ppm
styrene
for
4
hours
in
a
4000
cubic
ft.
room
(
about
110
m
³
)
in
which
fans
were
arranged
to
produce
rapid
and
thorough
mixing
of
the
air
(
Carpenter
et
al.
1944).
Styrene
was
evaporated
at
room
temperature
from
large
wicks
in
air
stream
and
the
vapor
concentration
was
monitored
(
using
an
"
interferometer"
developed
for
the
iodometric
determination
of
organic
vapors)
and
controlled
manually.
Psycho­
motor
response
was
followed
by
means
of
a
"
steadiness"
test.
The
test
was
performed
by
the
subject
holding
at
arm
´
s
length
a
small
wire
in
a
hole
drilled
in
a
copper
strip.
The
number
of
contacts
and
the
time
the
wire
was
in
contact
with
the
periphery
of
the
hole
was
recorded
during
a
3­
minute
period.
Exposure
to
styrene
caused
immediate
eye
and
throat
irritation,
increased
nasal
mucous
secretion,
pronounced
and
persistent
metallic
taste,
and
CNS
depression
with
listlessness,
drowsiness,
impairment
of
balance,
and,
after
termination
of
exposure,
muscular
weakness
and
unsteadiness
that
were
accompanied
by
inertia
and
depression.
In
the
steadiness
test,
the
contact
time
was
630
%
of
the
day
´
s
normal
value.
There
was
apparently
no
control
without
exposure
so
it
cannot
completely
be
ruled
out
that
some
of
the
effects
described
might
not
be
related
to
the
styrene
exposure
but
to
the
experimental
conditions.
However,
this
seems
unlikely
since
the
styrene
concentration
was
very
high
and
the
effects
noted
were
very
pronounced.
Furthermore,
during
exposure
to
lower
concentrations
of
other
chemicals
(
butadiene,
toluene)
in
the
same
experiment,
weaker
or
no
effects
were
observed.

An
unspecified
number
of
humans
were
exposed
to
a
range
of
analytically
determined
concentrations
of
styrene
in
an
enclosed,
tightly
sealed
room
(
Wolf
et
al.
1956).
The
subjects
qickly
entered
the
room
and
noted
their
reactions
with
respect
to
odor,
eye
irritation,
and
nasal
irritation.
Probably,
there
was
no
unexposed
control,
but
experimental
details
(
esp.,
number
of
subjects,
duration
of
exposure)
were
not
reported
by
the
authors.
At
60
ppm,
there
was
a
"
detectable
odor
but
no
irritation".
100
ppm
were
"
tolerated
without
excessive
discomfort"
though
the
odor
was
"
strong".
An
"
objectionably
strong
odor"
was
felt
between
200
and
400
ppm,
while
600
ppm
or
more
caused
strong
eye
and
nasal
irritation.

In
a
toxicokinetic
study,
two
volunteers
were
exposed
to
styrene
at
concentrations
up
to
386
ppm
for
2
hours
while
performing
light
physical
exercise
of
50
W
(
Löf
and
Johanson
1993,
see
section
4.1).
No
information
was
presented
with
respect
to
subjective
or
objective
signs
of
intoxication
or
irritation,
but
it
may
reasonably
be
assumed
that
no
severe
effects
will
have
occurred
in
such
a
study.

Local
irritation
and
effects
on
the
nervous
system
were
studied
by
Stewart
et
al.
(
1968).
The
study
was
conducted
with
a
group
of
9
healthy
male
technical
employees
(
32
 
55
years
old)
with
no
known
exposure
to
styrene
for
at
least
a
year.
In
5
experiments,
a
number
of
1
 
5
subjects
were
exposed
for
1,
2
or
(
with
a
30­
minute
break
at
half­
time)
7
hours
in
an
exposure
chamber
of
about
50
m
³
to
analytically
(
infrared
analysis
and
gas
chromatography)
confirmed
styrene
concentrations
of
51.4
ppm
(
1
hour),
99.4
ppm
(
7
hours),
116.7
ppm
(
2
hours),
216.1
ppm
(
1
hour),
and
376
ppm
(
1
hour).
During
exposure,
subjective
and
objective
responses
of
each
individual
were
recorded
every
15
minutes.
A
neurological
examination
was
performed
every
15
minutes
during
exposures
lasting
up
to
2
hours
and
every
hour
at
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6
longer
lasting
exposures.
This
examination
included
a
modified
Romberg
test
(
balancing
on
one
foot
with
eyes
closed
and
both
arms
at
a
side),
heel
and
toe,
and
finger
to
nose
test.
Additionally
a
manual
dexterity
and
a
Flannigan
coordination
test
were
performed
the
morning
and
afternoon
during
the
7­
hour
exposure
and
after
30
minutes
during
the
1­
hour
exposure
to
216
and
376
ppm.

No
untoward
subjective
symptoms
or
objective
signs
of
illness
were
recorded
during
a
1­
hour
exposure
to
51
ppm
(
3
subjects)
or
during
a
2­
hour
exposure
to
117
ppm
(
1
subject).
The
odor
was
strong,
but
not
judged
to
be
objectionable.
At
216
ppm
(
3
subjects),
the
odor
was
initially
strong,
and
one
subject
noted
nasal
irritation
after
20
minutes.
No
signs
of
CNS
effects
were
observed
during
the
1­
hour
exposure.

Effects
were
seen
at
376
ppm
(
5
subjects).
Three
of
the
subjects
previously
exposed
to
216
ppm
reported
they
were
able
to
discern
that
they
were
now
exposed
to
a
higher
concentration.
"
Mild"
eye
irritation
occurred
within
3
minutes.
All
subjects
complained
of
nasal
irritation
within
15
minutes
and
one
of
them
of
a
burning
sensation
of
the
skin
of
his
face.
Neurological
alterations
also
were
seen
at
this
concentration.
After
25
minutes,
one
subject,
after
60
minutes
two
subjects
were
unable
to
normally
perform
the
modified
Romberg
test.
After
50
minutes,
significant
decrements
were
found
in
3
of
5
subjects
in
other
tests
of
coordination
and
manual
dexterity.
Furthermore,
nausea
after
45
minutes
in
one
subject
(
persisting
one
hour
post
exposure),
and
feeling
of
being
inebriated
(
2
subjects)
and
headache
(
one
subject)
after
one
hour
were
reported.

Exposure
to
99
ppm
for
2
x
3.5
hours
caused
complaints
of
mild
eye
and
throat
irritation
in
3
of
6
subjects
after
20
 
30
minutes
which
later
subsided.
3
of
6
subjects
reported
intermittent
difficulties
in
performing
the
Romberg
test
one
or
two
times
at
the
eight
trials
of
this
test
during
exposure.
Tests
of
coordination
and
manual
dexterity
were
normal.
At
the
end
of
exposure,
there
were
no
reports
of
subjective
symptoms.
Throughout
the
study,
clinical
and
laboratory
data
were
normal
and
not
altered
compared
to
preexposure
(
Stewart
et
al.
1968).

Effects
of
styrene
on
psychological
functions
were
studied
in
12
healthy
male
volunteers
(
age
21
 
31
years)
(
Gamberale
and
Hultengren
1974).
They
were
exposed
in
groups
of
six
to
either
air
(
control)
or
to
nominal
but
analytically
(
gas
chromatography)
monitored
concentrations
of
50,
150,
250
and
350
ppm
styrene
via
mouthpiece
in
four
continuous
30­
minute
periods.
After
each
30­
minute
period,
the
concentration
of
styrene
was
raised
to
the
next
higher
level
without
interruption
of
exposure.
In
a
second
set
of
experiments,
the
control
group
was
exposed
to
styrene
and
vice
versa.
Performance
tests
were
carried
out
during
each
period
of
eposure.
Care
was
taken
that
the
volunteers
were
unaware
of
the
exposure
status
by
introducing
menthol
into
the
inhaled
air,
breathing
through
a
mouthpiece
only,
and
use
of
nose
clips.
Additionally,
control
experiments
were
initiated
with
a
a
relatively
strong
smell
of
styrene
in
the
mouthpiece
and
ended
with
a
short
exposure
to
styrene
after
completion
of
the
final
test.
All
subjects
believed
that
they
had
been
exposed
on
both
trial
days.
Local
irritation
was
almost
completely
absent
because
the
subjects
were
exposed
via
mouthpiece
so
that
eyes
and
nose
were
spared
from
direct
exposure.
Nevertheless,
compared
to
control
exposure,
subjects
felt
slight
discomfort
(
feeling
of
tension
and
being
affected)
after
exposure
to
styrene.
In
the
performance
tests,
the
performance
level
in
the
two
perceptual
tests
(
Identical
Numbers
and
Spokes),
was
affected
by
training,
both
under
control
and
exposure
conditions.
In
both
tests,
the
training
effect
in
exposure
to
styrene
was
somewhat
less
pronounced
than
in
control
conditions,
especially
at
the
two
higher
concentrations.
This
could
indicate
that
training
was
less
effective
under
styrene
exposure,
however,
the
differences
between
the
mean
performance
values
for
control
and
styrene
exposure
were
not
significantly
different
in
any
case.
There
was
a
clear
effect
of
styrene
on
reaction
time.
The
reaction
time
was
significantly
impaired
in
two
tests
(
simple
and
choice
reaction
time)
at
350
ppm
but
not
at
lower
concentrations.
Styrene
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7
In
a
further
study,
6
volunteers
were
exposed
to
analytically
(
Beckman
hydrocarbon
analyzer)
monitored
concentrations
of
styrene
in
room
of
about
15
m
³
(
Oltramare
et
al.
1974).
3
of
the
6
volunteers
had
been
exposed
occpationally
to
styrene
but
not
during
the
last
1
days
prior
to
the
experiment.
Altogether,
42
exposure
sessions
were
held
each
lasting
1
 
3
hours
and
usually
exposing
one
or
two
subjects
at
a
time.
2
subjects
were
exposed
to
styrene
once
at
300
ppm,
all
were
exposed
once
or
twice
to
100
and
200
ppm,
and
most
were
exposed
at
3
 
5
ppm
("
odor­
blinded"
control)
and
50
ppm.

Psychomotor
functions
of
the
three
subjects
with
previous
occupational
exposed
to
styrene
were
studied
in
sessions
each
lasting
90
minutes.
Volunteers
were
individually
exposed.
All
were
exposed
to
3
 
5
ppm
first,
then
to
50
(
only
two
subjects),
100,
or
200
pm
in
random
order,
and
finally
to
3
 
5
ppm
again.
Reaction
time
was
determined
before,
1
hour
after
start,
and
30
minutes
after
termination
of
exposure.
Simple
reaction
time
was
about
the
same
as
pre­
exposure
at
3
 
5
ppm
but
was
lengthened
by
12
 
37
%
at
50,
100,
and
200
ppm
during
exposure.
Similar
results
were
obtained
in
an
audiovisual
reaction
test.
However,
there
was
no
concentration
response
trend.
In
a
multiple
stimulus
reaction
test,
no
effect
on
performance
was
seen
at
50
ppm.
As
the
ability
to
perform
this
test
improved
with
repeated
trials,
both
during
each
session
and
from
session
to
session,
the
authors
comment
that
an
effect
of
styrene
at
50
ppm
might
have
been
masked.
A
decrement
of
about
2
%
at
100
ppm
and
of
10
%
at
200
ppm
during
and
after
exposure
were
seen
(
Oltramare
et
al.
1974).

Difficulties
in
balance
performance
were
also
studied
by
Oltramare
et
al.
(
1974)
in
3
of
6
subjects.
Statistically
significant
differences
in
a
modified
Romberg­
test
on
a
swaying
platform
were
observed
after
1­
hour
exposure
to
200
ppm
compared
to
control.
No
difference
was
seen
when
results
from
control
and
the
100­
ppm
group
were
compared.
The
authors
noted
that
 
due
to
the
small
sample
size
and
the
large
variation
of
data
 
the
results
should
be
confirmed
before
definite
conclusions
are
drawn.

Also,
the
6
volunteers
were
asked
to
note
the
occurrence
of
12
subjective
symptoms
(
irritation:
lips,
nose,
eyes;
gastralgia,
CNS
effects:
nausea,
dizziness,
headaches,
sleepiness,
poor
concentration,
intoxication,
fatigue,
malaise)
during
and
after
the
exposure
(
FIGURE
1).
A
total
of
55
individual
responses
were
available
for
analysis
from
all
of
the
exposure
sessions.
For
each
of
the
12
symptoms,
the
number
of
positive
responses
was
presented
as
numerator
and
the
total
number
of
exposures
at
this
concentration
as
the
denominator
of
a
ratio.
Since
a
given
subject
could
have
been
exposed
more
than
once
at
a
given
concentration,
it
is
not
evident
if
multiple
positive
responses
for
each
individual
symptom
mean
that
several
subjects
experienced
a
symptom
or
that
one
subject
experienced
that
symptom
at
several
occasions.
Also,
it
cannot
be
deduced
from
the
data
which
symptoms
were
reported
by
the
3
previously
exposed
workers.
However,
the
authors
state
that
the
workers
reported
irritation
at
3
 
5
ppm,
and
the
authors
considered
that
this
may
have
been
due
to
chronic
inflammation
from
working
with
styrene.
On
the
other
hand,
the
symptoms
noted
for
CNS
effects
were
consistently
fewer
for
the
subjects
with
previous
exposure.
For
the
parameters
indicating
CNS
effects
and
also
for
gastralgia,
there
was
a
clear
increase
in
positive
symptom
reports
at
100
ppm
and
higher
concentrations.
The
authors
reported
that
at
50
ppm
about
half
of
the
subjects
experienced
what
was
described
as
a
prenarcotic
discomfort.
For
irritation,
an
increase
in
symptom
reports
seems
evident
only
for
eye
irritation
at
200
ppm,
and,
less
so,
for
irritation
of
the
lips
at
200
ppm
(
Oltramare
et
al.
1974).
Styrene
NAC:
02/
2004
8
FIGURE
1:
SYMPTOM
RATINGS
AT
OR
AFTER
ACUTE
EXPOSURE
OF
HUMANS
TO
STYRENE
(
Table
adopted
from
Oltramare
et
al.
1974)

Vestibulo­
oculomotor
disturbances
were
studied
by
Ödkvist
et
al.(
1982).
10
healthy
nonsmoking
volunteers
(
5
man,
5
women,
age
20
 
30
years)
inhaled
styrene
via
mouth­
tube
at
an
analytically
confirmed
concentration
between
87
and
139
ppm
(
fluctuating
<
2
%
during
each
individual
exposure)
during
light
exercise
(
50
W)
for
one
hour.
Vestibulo­
oculomotor
tests
(
swing
test,
optovestibular
test,
visual
suppression
test,
optokinetic
test,
saccade
test,
slow
pursuit
moving
test)
were
performed
before,
during
and
1
hour
after
exposure.
Each
individual
served
as
its
own
control.
There
were
no
effects
on
any
test
except
the
saccade
test
in
which
8
of
10
subjects
showed
an
enhanced
maximum
speed
of
the
saccade
during
exposure.
The
authors
conclude
that
the
results
suggest
an
effect
of
styrene
on
the
vestibulo­
ocular
system
by
blocking
inhibitory
mechanisms
in
the
CNS.

Pierce
et
al.
(
1998)
exposed
4
healthy
male
non­
smoking
volunteers
(
26
 
30
years
old,
no
known
history
of
solvent
exposure)
in
a
13.8
m
³
chamber
to
analytically
(
infrared
spectrophotometry)
confirmed
concentrations
of
15
 
99
ppm
styrene
in
different
exposure
scenarios.
No
changes
were
Styrene
NAC:
02/
2004
9
observed
in
a
digit
recognition
test
performed
after
35
minutes
of
exposures
and
in
electroencephalogram
performed
after
each
100­
minute
exposure.

TABLE
2:
SUMMARY
OF
ACUTE
NON­
LETHAL
EFFECTS
IN
CONTROLLED
HUMAN
STUDIES
FOLLOWING
INHALATION
OF
STYRENE
Exposure
duration
Concentration
ppm
(
mg/
m
³
)
Effects
and
remarks
Reference
1
 
2
minutes
500
 
800
ppm
300
 
400
ppm
Intolerable
irritation
of
previously
non­
exposed
subjects;
lacrymation,
irritation
of
nasopharynx
Götell
et
al.
1972
4
hours
800
Immediate
eye
and
throat
irritation,
CNS
depression
with
listlessness,
drowsiness,
impairment
of
balance,
and,
after
termination
of
exposure,
muscular
weakness
and
unsteadiness
with
inertia
and
depression
Carpenter
et
al.
1944
Not
reported
60
ppm
100
ppm
200
 
400
ppm
 
600
pm
Rapid
onset
of
effects:
"
detectable
odor
but
no
irritation"
"
tolerated
without
excessive
discomfort",
"
strong"
odor
"
objectionably
strong
odor"
strong
eye
and
nasal
irritation
Wolf
et
al.
1956
4
x
30
minutes
with
stepwise
increasing
concentration
50
ppm
150
ppm
250
ppm
350
ppm
Exposure
via
mouthpiece
(
avoiding
eye
irritation);
slight
increase
of
simple
and
choice
reaction
time
at
350
ppm
Gamberale
and
Hultengren
1974
1
hour
87
 
139
ppm
No
effect
on
vestibulo­
oculomotor
parameters
except
saccade
test
where
8
of
10
subjects
showed
an
enhanced
maximum
speed
of
the
saccade
Ödkvist
et
al.
1982
35
minutes
100
minutes
15
 
99
ppm
15
 
99
ppm
No
changes
in
digit
recognition
test
No
changes
in
electroencephalogram
Pierce
et
al.
1998
1
hour
2
hours
20
minutes
1
hour
3
minutes
15
minutes
25
min.
 
1
hour
2
x
3.5
hours
(
with
30
minutes
break)
51
ppm
117
ppm
216
ppm
216
ppm
376
ppm
376
ppm
376
ppm
99
ppm
No
subjective
symptoms
or
objective
signs
of
illness;
strong,
but
not
objectionable
odor
Odor
initially
strong,
nasal
irritation
No
signs
of
CNS
effects
"
Mild"
eye
irritation
Nasal
irritation
CNS
effects:
difficulties
in
balance
performance
tests,
decrements
in
manual
dexterity
test,
nausea,
inebriation,
headaches
Complaints
of
mild
eye
and
throat
irritation
after
20
 
30
minutes,
subsiding
later;
intermittent
difficulties
in
performing
Romberg
test
in
3/
6
subjects.
No
subjective
symptoms
or
signs
of
CNS
effects
at
the
end
of
exposure.
Clinical
and
laboratory
data
normal.
Stewart
et
al.
1968
Styrene
NAC:
02/
2004
10
TABLE
2:
SUMMARY
OF
ACUTE
NON­
LETHAL
EFFECTS
IN
CONTROLLED
HUMAN
STUDIES
FOLLOWING
INHALATION
OF
STYRENE
Exposure
duration
Concentration
ppm
(
mg/
m
³
)
Effects
and
remarks
Reference
1
 
3
hours
1
hour
1.5
hours
50,
100,
200
ppm
200
ppm
50,
100,
200
ppm
Rating
scores
for
subjective
symptoms
of
CNS
effects
(
headaches,
sleepiness,
nausea,
fatigue,
poor
concentration)
 

in
rating
score
at
 
100
ppm
Scores
for
irritation
at
50
ppm
also
 ,
but
no
evident
concentration
response
Slight
difficulties
in
balance
performance,
but
large
variation
of
data
Possibly
slight
increase
in
reaction
time,
but
no
dose­
response
Oltramare
et
al.
1974
6
hours
25
 
50
(
with/
without
4
peaks
15
min
100
ppm)
Neither
performance
to
neuropsychological
tests
nor
subjective
signs
and
symptoms
of
irritation
or
CNS
effects
negatively
influenced
Ska
et
al.
2003;
Vyskocil
et
al.
2002a
1
­
7.5
hours
0
ppm
20
ppm
75
 
125
ppm*
100
ppm
125
ppm
Men:
3
days
at
20
ppm,
4
days
at
100
ppm,
4
days
at
75
 
125
ppm
(
average
100
ppm),
5
days
at
125
ppm,
7
days
at
0
ppm
Women:
4
days
at
100
ppm,
2
days
at
0
ppm
No
CNS
effects
in
equilibrium
and
cognitive
testing
Subjective
symptoms
(
exposure
times
not
reported):

Irritation
(
eyes,
nose,
throat)
Headache:
Men/
Women
Men/
Women
13
%/
8
%
3
%/
0
%
17
%
0
%
20
%
0
%
33
%/
32
%
13
%/
35
%
45
%
12
%
Hake
et
al.
1983
3
 
4
hours
20
ppm
0.5
 
40
ppm
(
peak)
Ratings
for
odor,
annoyance
and,
marginally,
for
irritation
increase
with
concentration;
ratings
of
irritation
verbally
labelled
as
"
hardly
at
all"
Seeber
et
al.
2002
*:
fluctuating
exposure
concentration,
average
100
ppm.

Acute
effects
of
styrene
on
the
CNS
were
also
studied
in
a
total
group
of
healthy
male
volunteers
(
20
 
50
years
old,
smokers
and
non­
smokers)
not
previously
exposed
to
styrene
and
with
no
documented
exposure
to
neurotoxicants
during
the
study
(
Ska
et
al.
2003;
Vyskocil
et
al.
2002a;
2002b).
The
volunteers
were
exposed
to
styrene
at
rest
to
5
different
scenarios
that
lasted
6
hours
each:
a)
continuously
to
106
mg/
m
³
(
25
ppm),
b)
variable
exposure
with
a
mean
of
25
ppm
and
four
15­
minutes
peak
exposures
up
to
213
mg/
m
³
(
50
ppm),
c)
exposure
to
1
ppm,
control),
d)
exposure
to
50
ppm,
e)
mean
exposure
to
50
ppm
with
four
15­
minutes
peaks
up
to
426
mg/
m
³
(
100
ppm).
The
sequence
of
exposures
was
c­
a­
b­
c­
d­
e.
Exposure
was
carried
out
in
an
18
m
³
chamber
and
the
styrene
concentration
was
monitored
by
gas
chromatography
and
infrared
analysis.
Before
and
after
exposure,
the
volunteers
were
submitted
to
a
battery
of
test
proposed
by
the
World
Health
Organization
to
detect
neurotoxic
effects
of
chemicals:
sensory
tests
(
visual:
Lanthony
D­
15
and
vision
contrast
test,
olfactory:
smell
test),
neuropsychological
tests
(
reaction
time,
attention,
memory,
psychomotricity),
and
self­
evaluation
questionnaires
for
mood
(
seven­
category
response
scale)
and
symptoms
(
four­
point
scale
for
17
items
regarding
irritation
and
CNS
effects)
in
a
test­
retest
design.
The
testings
were
performed
before
exposure
Styrene
NAC:
02/
2004
11
(
Base­
line)
and
within
1
hour
after
the
end
of
exposure.
Initially,
42
subjects
took
part
in
the
study.
However,
only
data
from
subjects
who
had
taken
part
in
all
scenarios
were
retained
for
further
analyses.
Missing
data
were
due
to
absence
of
subjects
at
a
given
scenario
or
to
factual
problems
during
testing.
Therefore,
complete
data
were
available
for
24
subjects.
The
different
exposure
scenarios
negatively
influenced
neither
the
performance
to
any
test
nor
the
subjective
signs
and
symptoms.

Psychological
reactions
related
to
chemosensory
irritation
during
exposure
to
a
number
of
chemicals
including
styrene
were
investigated
by
Seeber
et
al.
(
2002).
Exposure
studies
were
conducted
in
a
ventilated
room
of
28
m
³
(
air
exchange
about
250
m
³
/
h)
with
continuous
control
of
the
concentration
of
the
test
substance
(
deviations
<
3
%).
In
all
experiments,
4
young
healthy
male
volunteers
who
had
no
knowledge
of
the
experimental
conditions,
were
investigated
simultaneously.
The
concentrations
of
styrene
were
20
ppm
for
3
hours
or
0,5
ppm
periods
for
50
minutes
followed
by
40
ppm
peaks
for
30
minutes
during
a
total
4
hours.
At
control
and
at
20
ppm
each,
a
total
number
of
16
volunteers
were
exposed,
at
0.5/
40
ppm,
the
total
number
of
volunteers
was
24.
Ratings
for
irritation,
odor
and
annoyance
were
assessed
and
mean
values
were
calculated
from
2
 
5
repeated
ratings
for
a
given
exposure
level
(
total
observations
16
 
246).
For
odor
and
annoyance,
ratings
increased
similarly
with
increasing
styrene
concentration
while
there
was
only
a
marginal
report
for
irritation.
Thus,
annoyance
was
more
closely
associated
with
odor
than
with
irritation.
Effect
sizes
comparing
the
ratings
during
exposure
to
20
ppm
and
during
the
pre­
exposure
test
were
higher
for
odor,
irritation
and
annoyance.
Effect
sizes
were
also
higher
compared
to
"
clean
air
only"­
exposure.
However,
the
ratings
for
irritation
(
in
case
of
styrene
and
all
other
solvents
investigated)
reached
only
levels
verbally
labelled
"
hardly
at
all".

Studies
with
repeated
inhalation
exposure
In
a
study
conducted
for
and
summarized
by
NIOSH
(
1983),
10
men
were
exposed
in
groups
of
2
 
4
for
1,
3,
or
7.5
hours/
day
to
0,
20,
100,
or
125
ppm
styrene
(
Hake
et
al.
1983).
8
women
were
exposed
in
groups
of
1
 
4
at
0
or
100
ppm.
For
men,
there
were
3
days
of
exposure
at
20
ppm,
4
days
at
100
ppm,
4
days
at
100
ppm
with
concentrations
fluctuating
between
75
and
125
ppm,
5
days
at
125
ppm,
and
7
days
at
0
ppm.
For
women,
there
were
4
days
at
100
ppm
and
2
days
at
0
ppm.
In
control
exposures,
the
chamber
was
odorized
with
10
ppm
styrene
upon
entry
of
the
subjects
after
which
exposure
was
reduced
to
0
ppm
within
10
minutes.
Each
subject
was
exposed
to
more
than
one
concentration,
non­
exposure
weekends
or
control
exposures
were
interspersed
with
exposure
to
styrene.

There
were
no
deleterious
effects
on
equilibrium
as
measured
by
Romberg­
and
heel­
to­
toe
tests.
Some
changes
in
visual
evoked
response
and
amplitude
of
electroencephalogram
(
EEC)
were
observed
in
3
of
6
subjects
studied
that
 
according
to
the
authors
 
were
consistent
with
CNS­
depression.
However,
the
changes
were
neither
consistent
between
subjects
nor
in
magnitude
within
subjects.
Furthermore,
there
was
no
significant
variance
in
cognitive
testing
scores
related
to
styrene
exposure.
Respiratory
parameters
generally
showed
no
effects
of
styrene
exposure;
however,
the
authors
observed
decrements
in
maximal
expiration
values
in
subjects
repeatedly
exposed
to
100
ppm
for
7.5
hours
(
no
details
reported).

With
respect
to
subjective
symptoms
noted
on
a
checklist
during
exposure,
the
overall
data
indicated
some
dose­
response
for
irritation
(
eyes,
nose,
and
throat)
and
headaches.
For
men,
the
reported
incidences
of
irritation
were
13
%
(
0
ppm),
17
%
(
20
ppm);
20
%
(
100
ppm),
33
%
(
100
ppm
fluctuating),
45
%
(
125
ppm);
for
headaches,
incidences
were
3
%,
0
%,
0
%,
13
%,
12
%.
For
women,
the
incidence
of
irritation
was
8
%
(
0
ppm)
ad
32
%
(
100
ppm),
for
headaches,
incidences
were
0
%
and
35
%.
There
was
no
specific
indication
as
to
which
exposure
time
the
various
subjective
responses
were
elicited
at
a
given
exposure
concentration
(
Hake
et
al.
1983).
Styrene
NAC:
02/
2004
12
Odor
perception
The
odor
of
styrene
has
been
described
as
solventy,
rubbery,
and
plasticy
(
Leonardos
et
al.
1969;
Ruth
1986)
and
also
as
strongly
metallic
(
Gamberale
and
Hultengren
1974).
A
wide
range
of
odor
thresholds
is
reported
in
the
literature.
This
wide
range
may
be
due
to
different
degrees
of
purities
of
the
test
substances
used,
the
presence
or
absence
of
polymerization
inhibitors,
different
methodology
used,
different
bases
used
(
median,
mean,
range),
individual
variability
or
an
adaptation
to
odor
perception
following
repetitive
exposure.

The
olfactory
function
and
the
styrene
odor
detection
threshold
were
compared
between
a
group
of
workers
exposed
to
styrene
at
least
4
years
(
reinforced­
plastics
industry,
current
mean
personal
air
sampling
concentrations
of
styrene
about
11
 
66
ppm)
and
a
group
of
age­
and
gender­
matched
naïve
controls
(
Dalton
et
al.
2003).
Absolute
odor
threshold
concentration
values
were
not
presented
in
the
study.
The
styrene
odor
detection
threshold
for
workers
was
on
average
32­
fold
higher
than
for
controls.
Furthermore,
when
the
results
were
stratified
by
age,
the
most
pronounced
increase
in
odor
threshold
was
observed
in
workers
who
were
in
their
5th
or
6th
decade,
while
duration
of
exposure
was
not
related
to
the
effect.
No
differences
were
found
betweeen
workers
and
controls
with
respect
to
the
odor
threshold
for
an
olfactory
standard,
phenylethyl
alcohol,
and
for
the
ability
to
identify
a
variety
of
20
different
aroma
compounds
in
an
odor
identification
test.
The
results
do
not
provide
evidence
that
styrene
is
an
olfactory
toxicant
in
humans.

Van
Doorn
et
al.
(
2002)
present
results
of
odor
threshold
determinations
for
styrene
that
were
a)
measured
by
olfactometry
methods
considered
compatible
with
a
precursor
of
the
NVN2820
and
EN13725
method
or
b)
were
measured
by
TNO
in
the
Netherlands
using
a
precursor
of
the
NVN2820
and
EN
13725
methods,
with
a
mean
n­
butanol
threshold
of
25
ppb.
Results
of
both
were
converted
to
the
reference
agreed
in
EN13725
of
400
ppb
n­
butanol
by
using
a
factor
of
40:
25
=
1.6.
Thereby,
odor
thresholds
of
0.049
ppm
and
0.025
ppm,
respectively,
were
obtained.
Taking
into
account
the
threshold
value
of
0.033
ppm
obtained
by
the
Japanese
method
(
see
below
Hoshika
et
al.
1993),
Van
Doorn
et
al.
(
2002)
calculated
a
mean
odor
threshold
of
0.0345
ppm
for
styrene.

A
comparison
of
odor
threshold
values
determined
by
different
methods
in
Japan
(
triangle
olfactometer
method,
odor
room,
20
trained
male
perfumers
30
 
45
years
old)
and
in
the
Netherlands
(
olfactometer,
4
men,
4
women
18
 
40
years
old),
showed
that
the
"
barely
perceptible
or
detectable
odor
thresholds"
of
0.033
ppm
and
0.016
ppm,
respectively,
are
quite
similar
(
Hoshika
et
al.
1993).
The
Japanese
"
triangle
olfactometer
method"
produces
an
n­
butanol
threshold
of
38
ppb
that
is
compatible
with
the
value
(
40
ppb)
of
the
method
according
to
EN13725
(
Van
Doorn
et
al.
2002).

In
accordance
with
these
data,
WHO
(
1983)
reported
an
odor
perception
threshold
of
0.05
 
0.08
ppm.
In
other
older
studies
and
compilations,
substantially
higher
values
were
reported.
Odor
thresholds
ranging
from
0.1
 
201
ppm
(
0.43
 
860
mg/
m
³
)
for
styrene
(
inhibited)
and
from
0.047
 
201
ppm
(
0.2021
 
860
mg/
m
³
)
for
styrene
(
uninhibited)
were
reported
by
Ruth
(
1986).
Based
on
10
original
literature
references
which
were
not
explicitly
reported,
a
geometric
mean
odor
threshold
of
0.32
ppm
styrene
(
standard
error
2.0
ppm)
was
calculated
(
Amoore
and
Hautala
1983).

The
odor
recognition
threshold
was
determined
for
53
odorant
chemicals
including
styrene
under
controlled
laboratory
conditions
using
a
standardized
and
defined
procedure
(
Leonardos
et
al.
1969).
The
odor
threshold
represents
that
concentration
at
which
all
four
trained
panelists
could
positively
recognize
the
odor.
Different
threshold
values
were
obtained
for
styrene
without
inhibitor
(
0.047
ppm)
or
with
inhibitor
Styrene
NAC:
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13
(
0.10
ppm)
and
for
inhibited
styrene
additionally
purified
by
gas­
liquid
chromatography
(
0.21
ppm).
The
chemical
nature
of
the
inhibitor
was
not
reported.

2.3
Developmental/
Reproductive
Toxicity
No
data
regarding
developmental
or
reproductive
toxicity
in
humans
following
single
exposure
to
styrene
have
been
found
in
the
available
literature.

Studies
with
repeated
inhalation
exposure
The
epidemiological
data
have
been
extensively
reviewed
recently
(
Brown
et
al.
2000;
IARC
2002).
In
case
reports,
malformations
in
children
of
styrene­
exposed
mothers
and
spontaneous
abortion
in
female
workers
occupationally
exposed
to
styrene
were
described.
However,
these
observations
could
not
be
confirmed
in
epidemiological
studies.
According
to
the
reviews
mentioned
above,
there
is
no
sound
evidence
for
an
association
between
workplace
exposure
to
styrene
and
spontaneous
abortions,
malformations
or
decreased
male
fecindity.

2.4
Genotoxicity
Genotoxicity
studies
have
been
extensively
evaluated
and
summarized
in
a
number
of
reviews
(
ATSDR
1992;
Bonassi
et
al.
1996;
Cohen
et
al.
2002;
IARC
1994;
IARC
2002;
Vodicka
et
al.
2002;
WHO
1983;
WHO
2000).
Since
a
detailed
description
of
the
findings
from
these
studies
is
beyond
the
scope
of
this
TSD,
findings
as
described
in
these
reviews
are
summarized.

In
in
vitro
systems
with
human
cells,
styrene
induced
chromosomal
aberrations
(
CA),
sister
chromatid
exchanges
(
SCE),
micronuclei,
and
hypoploidy
in
whole­
blood
cultures
in
the
absence
of
exogenous
metabolic
activation
system
were
observed.
CA
and
SCE
were
also
observed
in
lymphocyte
cultures
in
the
absence
of
exogenous
metabolic
activation
system.

In
vivo,
no
data
regarding
genotoxic
effects
in
humans
following
single
exposure
to
styrene
have
been
found
in
the
available
literature.

Studies
with
repeated
inhalation
exposure
A
number
of
cytogenetic
studies
have
been
conducted
on
workers
with
occupational
exposure
to
styrene,
especially
in
the
reinforced
plastics
industry.
The
workers
in
the
individual
studies
had
been
exposed
between
less
than
one
year
and
about
30
years
to
widely
differing
concentrations
of
styrene
as
estimated
from
air
sample
or
monitoring
or
biological
monitoring
of
urinary
styrene
metabolites.
The
number
of
workers
included
in
individual
studies
mostly
was
less
than
50.
With
respect
to
chromosomal
aberrations,
the
majority
of
studies
revealed
a
significant
increase
in
CA
(
including
gaps),
and
doseresponses
were
observed
in
several
studies.
A
cross­
studies
evaluation
found
a
positive
association
among
studies
between
the
level
of
styrene
exposure
and
the
frequency
of
CA.
Fewer
studies
have
looked
at
sister
chromatide
exchange
(
SCE),
and
the
percentage
of
positive
studies
was
smaller
than
the
percentage
of
positive
studies
of
CA.
However,
two
regression
analyses
revealed
significant
associations
between
styrene
in
air
or
urinary
mandelic
acid
excretion
and
SCE
frequency.
There
is
less
evidence
of
an
association
between
styrene
exposure
and
the
frequency
of
micronuclei,
and
in
a
cross­
studies
evaluation,
no
such
association
could
be
found.
Other
studies
in
workers
have
provided
evidence
that
occupational
exposure
to
exposure
may
lead
to
a
several­
fold
increase
in
the
formation
of
DNA­
adducts
(
O6­
deoxyguanosine
and
N7­
deoxyguanosine
adducts),
DNA
single­
strand
breaks,
and
gene
mutations
at
the
HPRT
and
the
glycophorin
A
locus.
Styrene
NAC:
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14
Recently,
physiological
modeling
of
the
relative
contributions
of
styrene­
7,8­
oxide
(
SO)
derived
from
direct
inhalation
and
from
styrene
metabolism
to
the
systemic
dose
in
humans
has
been
performed.
From
these
calculations,
it
has
been
suggested
that
SO
which
is
present
in
the
air
at
workplaces
in
the
reinforced
plastics
industry
could
present
a
greater
hazard
of
cytogenetic
damage
than
inhalation
of
styrene
(
Tornero­
Velez
and
Rappaport
2001).

2.5
Carcinogenicity
No
data
regarding
the
development
of
cancer
in
humans
following
single
exposure
have
been
found
in
the
available
literature.

Studies
with
repeated
inhalation
exposure
The
cancer
epidemiology
data
have
been
reviewed
recently
(
Cohen
et
al.
2002;
IARC
2002).

Retrospective
cohort
mortality
studies
and
nested
case­
control
studies
were
conducted
in
three
types
of
industy:
in
the
production
of
styrene
monomer
and
polystyrene,
of
glass­
fibre
reinforced
plastics,
and
of
styrene­
butadiene
rubber.

Because
workers
in
the
reinforced
plastics
industry
have
higher
styrene
exposure
and
less
potential
for
exposure
to
other
substances
than
the
other
cohorts
studied,
the
most
informative
data
with
regard
to
an
association
between
styrene
exposure
and
cancer
come
from
studies
of
these
cohorts.
In
three
studies
in
such
cohorts,
an
excess
of
lung
or
respiratory
cancer
was
found.
However,
the
excess
occurred
in
those
groups
of
workers
with
lower
exposure.
An
excess
of
lymphatic
and
hematopoietic
(
LH)
cancers
was
observed
in
some
epidemiological
studies
in
the
reinforced
plastics
industry,
but
not
in
others.
Such
an
association
also
was
found
in
two
studies
of
workers
in
styrene
production,
but
exposure
was
poorly
documented
and
may
have
been
also
to
other
chemicals
beside
styrene.
Studies
in
workers
of
the
styrenebutadiene
rubber
production
also
found
a
small
excess
of
leukemia
mortality.
However,
these
findings
are
difficult
to
evaluate
because
of
the
high
correlation
between
exposure
to
styrene
and
butadiene
(
Cohen
et
al.
2002).

Reports
of
increased
risks
of
other
cancers
(
rectal,
pancreatic,
nervous
system)
are
also
reported
in
some
studies.
Mostly,
the
numbers
of
cases
are
small,
and
these
findings
are
not
supported
from
data
of
larger
cohort
studies.

2.6
Summary
A
great
number
of
studies
on
workers
with
occupational
exposure
to
styrene
in
different
workplaces
have
been
carried
out.
These
studies
have
been
repeatedly
reviewed
and
summarized
(
ACGIH
1997;
ATSDR
1992;
Cohen
et
al.
2002;
DFG
1987;
Government
Canada
1993;
IARC
2002;
OEHHA
1999;
Sherrington
and
Routledge
2001;
US
EPA
1998;
WHO
1983;
WHO
2000).
The
highest
exposure
occurs
in
the
fabrication
of
reinforced­
polyester
plastics
composites,
where
8­
hour
average
samples
in
breathing
zones
often
exceeded
100
ppm
styrene
(
IARC
2002).
In
older
studies
on
workers
in
the
manufacture
of
reinforced
plastics,
8­
hours
TWA
concentrations
in
the
breathing
zone
of
up
to
292
ppm
were
reported,
with
peaks
of
about
1500
ppm
during
shorter
periods
of
work
for
about
5
 
10
minutes
(
Götell
et
al.
1972).

In
workers
with
chronic
exposure
to
styrene,
effects
on
the
central
and
peripheral
nervous
systems
that
were
described
in
many
studies
include
a
reversible
decrease
in
color
discrimination.
Decrements
of
auditory
function
was
also
observed,
though
findings
made
in
several
smaller
cross­
sectional
Styrene
NAC:
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2004
15
studies
could
not
be
confirmed
in
the
largest
study.
Studies
of
effects
on
the
immune
and
hematopoetic
system,
liver,
and
kidney
did
not
reveal
consistent
changes
(
IARC
2002).

No
reports
of
lethal
intoxication
following
styrene
exposure
were
located
in
the
literature.

Pure
styrene
has
a
pungent,
slightly
sweetish
odor.
A
wide
range
of
odor
thresholds
has
been
reported.
Van
Doorn
et
al.
(
2002)
presented
results
of
odor
threshold
determinations
for
styrene
and
calculated
an
n­
butanol
corrected
mean
odor
threshold
of
0.0345
ppm
for
styrene.

Styrene
is
irritating
to
eyes
and
the
respiratory
tract.
In
a
number
of
controlled
studies
with
human
volunteers,
irritation
and
effects
on
the
CNS
were
investigated.

In
a
study
on
psychological
reactions
related
to
chemosensory
irritation,
ratings
for
odor
and
annoyance
increased
similarily
with
increasing
styrene
concentrations
ranging
from
20
 
40
ppm,
while
there
was
only
a
marginal
increase
for
irritation.
Effects
sizes
comparing
the
ratings
between
exposure
to
20
ppm
and
pre­
exposure
were
higher
for
odor,
irritation,
and
annoyance.
Effects
sizes
were
also
higher
compared
to
"
clean
air
only"­
exposure.
However,
the
ratings
for
irritation
reached
only
levels
verbally
labelled
as
"
hardly
at
all"
(
Seeber
et
al.
2002).
No
increase
in
irritation
or
headaches
compared
to
control
was
noted
at
20
ppm
in
a
further
study
(
Hake
et
al.
1983).
At
50
ppm,
one
study
indicated
a
marginal
increase
in
subjective
symptoms
ratings
for
eye
and
nose
irritation,
headache,
and
fatigue
(
Oltramare
et
al.
1974).
In
that
study,
signs
of
irritation
and
of
mild
subjective
CNS
effects
(
headaches,
fatigue,
poor
concentration,
sleepiness)
were
reported
more
often
at
100
ppm.
Complaints
of
mild
eye
and
throat
irritation
at
100
ppm
in
one
test
but
not
in
another
were
reported
by
Stewart
et
al.
(
1968).
In
a
recent
study,
subjective
signs
and
symptoms
during
6­
hour
exposure
to
25
 
50
ppm
styrene
with
4
peaks
of
15
minutes
at
100
ppm
indicated
no
irritation
(
Vyskocil
et
al.
2002a,
b).
At
about
200
ppm,
most
subjects
noted
irritation
of
eye
and
nose
(
Oltramare
et
al.
1974;
Stewart
et
al.
1968)
and
the
severity
increased
with
a
further
increase
in
concentration
to
376
ppm.
In
their
study
on
styrene­
exposed
workers,
Götell
et
al.
(
1972)
noted
that
they
themselves
suffered
from
immediate
lacrymation
at
300
 
400
ppm
and
could
not
withstand
500
 
800
ppm
for
more
than
1
 
2
minutes
although
the
workers
tolerated
such
concentrations.
In
two
further
studies
with
controlled
exposure
of
volunteers,
concentrations
 
600
ppm
caused
strong
eye,
nasal,
and
throat
irritation
(
Carpenter
et
al.
1944;
Wolf
et
al.
1956).

No
lesions
of
the
nasal
mucosa
were
observed
in
a
cross­
sectional
study
on
styrene­
exposed
workers.
Furthermore,
the
ability
to
detect
and
identify
different
odors
in
a
controlled
odor
test
was
not
affected
in
workers
with
long­
term
exposure
to
styrene.
These
limited
data
provide
some
evidence
that
 
in
contrast
to
rats
and
especially
mice
 
styrene
does
not
seem
to
be
an
olfactory
or
upper
respiratory
tract
toxicant
in
humans.
Support
for
this
conclusion
also
comes
from
toxicokinetic
studies
in
vitro
in
which
the
metabolic
capacity
of
nasal
epithelia
from
humans,
rats,
and
mice
was
compared
(
see
section
4.1,
page
47).

With
respect
to
CNS
effects,
one
study
reported
higher
ratings
of
headaches,
poor
concentration,
and
fatigue
at
50
ppm
compared
to
 
odor­
blinded"
control
exposed
to
3
 
5
ppm
(
Oltramare
et
al.
1974).
In
another
study,
headaches
did
not
occur
when
subjects
were
repeatedly
exposed
to
fluctuating
concentrations
of
75
 
125
ppm
(
average:
100
ppm),
but
were
reported
at
125
ppm
(
Hake
et
al.
1983).
Pierce
et
al.
(
1998)
found
no
changes
in
a
digit
recognition
test
after
35
minutes
of
exposure
and
in
electroencephalogram
after
100
minutes
of
exposure
to
15
 
99
ppm
styrene
in
different
exposure
scenarios.
At
100
ppm,
intermittent
difficulties
in
performing
a
modified
Romberg
test
were
observed
in
3/
6
subjects
exposed
for
7
hours
with
a
30­
minute
break
in
between.
Other
tests
on
coordination
and
on
manual
dexterity
were
normal,
and
no
effects
were
noted
at
the
end
of
exposure.
In
the
same
study,
no
CNS
effects
were
seen
in
another
experiment
with
100
ppm
exposure
for
2
hours
or
216
ppm
for
1
hour
(
Stewart
et
al.
1968).
Also,
exposure
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2004
16
for
6
hours
at
50
ppm
with
4
peaks
of
15
minutes
at
100
ppm
had
no
negative
influence
on
performance
to
neuropsychological
tests
(
Vyskocil
et
al.
2002a,
b).
No
effects
on
equilibrium
and
cognitive
function
tests
were
noted
in
male
and
female
volunteers
at
repeated
exposures
to
100
and
125
ppm
for
at
least
one
hour
(
Hake
et
al.
1983).
Oltramare
et
al.
(
1974)
noted
that
slight
difficulties
in
balance
performance
at
50
 
200
ppm
(
1.5
hours),
but
there
was
no
concentration­
response,
and
slight
difficulties
in
balance
performance
at
200
ppm
(
1
hour),
but
the
variation
of
data
was
large.
No
effects
on
simple
and
choice
reaction
time
was
seen
following
exposure
to
250
ppm
for
30
minutes.
However,
when
the
concentration
was
raised
to
350
ppm
for
30
minutes
directly
afterwards,
both
simple
and
choice
reaction
time
were
increased
(
Gamberale
and
Hultengren
1974).
More
pronounced
effects
were
observed
during
exposure
to
376
ppm
for
one
hour:
one
subject
complained
of
nausea
that
persisted
one
hour
after
the
end
of
exposure,
2
had
a
feeling
of
being
inebriated,
and
3
of
5
subjects
exposed
were
unable
to
normally
perform
the
modified
Romberg
test
and
also
3
subjects
(
unclear,
if
the
same
3
subjects)
had
significant
decrements
in
other
tests
of
coordination
and
manual
dexterity
(
Stewart
et
al.
1968).
Only
one
controlled
study
was
located
in
which
CNS
effects
were
followed
at
a
higher
concentration
than
376
ppm.
In
that
study,
two
subjects
exposed
to
800
ppm
for
4
hours
reported
that
they
suffered
from
listlessness,
impairment
of
balance,
drowsiness,
and,
after
termination
of
exposure,
from
muscular
weakness
and
unsteadiness
with
inertia
and
depression.
CNSdepression
was
also
indicated
by
a
marked
decrease
in
performance
in
a
"
steadiness
test"
(
measuring
manual
dexterity)
(
Carpenter
et
al.
1944).

No
data
are
are
available
indicating
reproductive
or
developmental
toxicity
of
styrene
in
humans
after
acute
exposure.

In
in
vitro
systems
with
human
cells,
styrene
induced
chromosomal
aberrations
(
CA),
sister
chromatid
exchanges
(
SCE),
micronuclei,
and
hypoploidy.
No
data
regarding
genotoxic
effects
in
humans
following
single
exposure
to
styrene
are
available.
Epidemiological
studies
provide
evidence
for
genotic
effects
(
chromosomal
aberrations,
mutations,
DNA­
adducts)
in
occupationally
exposed
workers.

With
respect
to
carcinogenicity,
IARC
(
2002)
concluded
that
the
increased
risks
for
cancers
of
the
lymphatic
and
hematopoetic
system
are
small,
statistically
unstable
and
often
based
on
subgroup
analyses,
the
findings
are
not
very
robust
and
that
it
cannot
be
ruled
out
that
the
observations
are
the
results
of
chance,
bias
or
confounding.
Cohen
et
al.
(
2002)
conclude
that,
although
the
balance
of
epidemiologic
studies
do
not
suggest
a
causal
association
between
styrene
and
any
human
cancer,
because
of
the
limited
power
of
these
studies,
the
inconclusive
results
do
not
rule
out
the
possibility
that
the
observed
increase
of
lung
tumors
in
mice
are
of
relevance
to
humans.

In
its
latest
evaluation,
IARC
(
2002)
concluded
that
there
is
"
limited
evidence
in
humans
for
the
carcinogenicity
of
styrene"
and,
taking
into
account
the
results
from
animal
carcinogenicity
studies
(
see
3.5),
that
styrene
is
"
possibly
carcinogenic
to
humans
(
Group
2B)"
(
IARC
2002).
US­
EPA
´
s
Office
of
Research
and
Development
has
also
updated
previous
assessments
on
the
carcinogenic
potential
of
styrene
and
concluded
that
styrene
is
appropriately
classified
as
a
Group
C,
possible
human
carcinogen
(
US
EPA
2003).

Based
on
the
body
burden
of
styrene­
7,8­
epoxide
or
its
adducts
with
hemoglobin
and
DNA,
and
taking
into
account
the
results
from
carcinogenicity
studies
with
styrene
in
animals,
a
cancer
risk
has
been
estimated
in
the
range
of
1.7
 
7.5
per
100,000
persons
exposed
for
40
years
to
20
ppm
styrene,
8
hours/
day,
5
days/
week,
48
weeks/
year
(
Greim
2003).
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17
3
ANIMAL
TOXICITY
DATA
3.1
Acute
Lethality
Data
on
acute
lethality
after
inhalation
exposure
to
styrene
are
available
for
rats,
mice,
and
guinea
pigs
(
TABLE
3).
Non­
lethal
effects
observed
in
these
studies
are
described
in
section
3.2.2.

3.1.1
Rats
Female
and
male
Sprague­
Dawley
rats
(
10
of
each
sex/
group;
20
of
each
sex
at
the
highest
concentration)
were
exposed
to
analytically
(
gas
chromatography)
determinded
concentrations
of
2983,
3766,
4814,
5911,
6621,
7218
and
8407
ppm
styrene
in
a
180
L
dynamic
exposure
chamber
for
4
hours
(
BASF
1979b).
Survival
of
animals
was
followed
for
14
days
after
the
exposure.
No
deaths
were
observed
at
2983
and
3766
ppm.
At
the
other
conentrations,
deaths
were
observed
up
to
three
days
after
exposure.
No
differences
in
LC50
between
female
and
male
rats
were
observed.
A
combined
LC50
of
6410
ppm
(
95
%
conf.
limit
6025
 
6769
ppm)
for
male
and
female
rats
was
determined.
Necroscopy
revealed
acute
dilation
and
congestive
hyperemia
in
the
heart,
enlarged
lung,
and
centrilobular
liver
changes
with
fatty
degeneration.
Other,
non­
lethal
effects
are
described
in
section
3.2.2.

The
LC50
values
were
determined
for
a
number
of
benzene
derivatives
in
male
Sprague­
Dawley
rats
(
Bonnet
et
al.
1982a).
Groups
of
12
rats
each
were
exposed
(
as
more
precisely
described
in
Gradiski
et
al.(
1978))
in
170
L
dynamic
exposure
chambers
to
analytically
(
gas
chromatography)
confirmed
vapor
concentrations
of
styrene
for
6
hours.
Animals
were
observed
for
14
days
after
the
end
of
exposure.
The
6­
hour
LC50
for
styrene
was
4618
ppm
(
95
%
confidence
interval
4399
 
4894
ppm).
Death
was
preceded
by
somnolence,
tremors,
and
muscular
seizures
but
no
lacrymation
was
observed.
From
the
figure
presented
in
the
publication,
it
can
be
estimated
that
90
%
of
the
animals
died
(
LC90)
at
about
5000
ppm
and
10
%
died
(
LC10)
at
about
3300
ppm
(
FIGURE
2)
indicating
a
steep
concentration­
response
curve.
The
authors
also
reported
the
occurrence
of
delayed
deaths
(
more
than
24
hours
after
the
end
of
exposure)
and
that
surviving
animals
showed
growth
retardation
betweeen
day
7
and
14
post
exposure.
However,
no
detailed
data
were
presented.

A
total
number
of
405
rats
(
sex,
strain
and
number
of
animals
per
exposure
group
not
reported)
were
exposed
to
styrene
concentrations
ranging
from
1300
ppm
to
10,000
ppm
for
one
hour
to
up
to
more
than
30
hours
(
Spencer
et
al.
1942).
After
the
exposure
the
animals
were
observed
for
2
 
4
weeks.
No
LC50
but
only
LC0
and
LC100
were
reported
in
the
study.
The
highest
concentration
that
could
be
reached
without
observed
condensation
of
the
chemical
out
of
the
atmosphere
was
10,000
ppm1.
At
this
concentration,
no
deaths
were
observed
after
one
hour
of
exposure,
but
all
rats
exposed
for
3
hours
died.
At
5000
ppm,
no
animal
died
after
exposure
for
2
hours
but
all
animals
exposed
for
8
hours
died.
At
2500
ppm,
all
animals
survived
an
8­
hour
exposure
and
death
of
all
animals
only
was
observed
when
the
exposure
lasted
21
hours.
All
animals
survived
16
hours
of
exposure
to
2000
ppm.
Immediate
deaths
during
or
shortly
after
the
end
of
exposure
were
due
to
the
effect
of
styrene
on
the
CNS
(
see
3.2.2).
However,
there
were
also
delayed
deaths
with
pulmonary
edema
and
hemorrhages
that
were
considered
to
develop
as
a
result
of
the
acute
irritating
effect
of
styrene
on
the
lung.

1
[
Note:
from
the
vapor
pressure
data
 
see
TABLE
1
 
a
saturated
vapor
concentration
of
6580
ppm
at
20
°
C
and
of
8560
ppm
at
25
°
C
can
be
calculated].
Styrene
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18
FIGURE
2:
CONCENTRATION­
RESPONSE
CURVE
FOR
ACUTE
LETHALITY
FOLLOWING
INHALATION
OF
STYRENE
IN
RATS
(
Figure
from
Bonnet
et
al.
1982a)

Shugaev
(
1969)
exposed
rats
(
strain,
sex
and
number
of
animals
not
reported)
to
analytically
(
gas
chromatography)
controlled
styrene
vapor
concentrations
for
4
hours
in
dynamic
flow
exposure
chambers.
A
LC50
of
11.8
mg/
l
(
95
%
confidence
interval
10.3
 
13.5
mg/
l)
(
2761
ppm;
95
%
confidence
interval
2410
 
3159
ppm)
was
calculated.
It
was
also
reported
that
animals
"
often"
died
after
the
exposure.
It
is
further
reported
that
these
animals
were
not
used
for
the
determination
of
lethal
brain
styrene
concentrations
but
it
is
not
clear
if
data
for
animals
dying
after
the
end
of
exposure
were
included
in
the
determination
of
the
LC
values.

Groups
of
ten
female
Sprague­
Dawley
rats
were
exposed
to
analytically
(
infrared
analysis)
confirmed
styrene
vapor
concentrations
for
4
or
8
hours,
respectively
(
Lundberg
et
al.
1986).
Deaths
were
counted
24
hours
after
the
start
of
exposure.
At
33,200
mg/
m
³
(
7769
ppm),
a
concentration
that
corresponded
to
approximately
saturated
styrene
vapor
in
air
at
25
°
C
(
see
footnote
1),
no
deaths
were
seen
after
a
4­
hour
exposure
but
four
of
ten
animals
died
within
24
hours
after
an
8­
hour
exposure.
No
LC50
could
be
determined.

TABLE
3:
SUMMARY
OF
LETHAL
EFFECTS
IN
ANIMALS
AFTER
ACUTE
INHALATION
EXPOSURE
TO
STYRENE
Species,
sex,
strain
Concentration
in
ppm
Exposure
Duration
Effect/
Remarks
Reference
Rat,
f,
m,
S­
D
6410
6310
6480
4
hours
LC50,
female
and
male
LC50,
females
only
LC50,
males
only
BASF
1979b
Styrene
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2004
19
TABLE
3:
SUMMARY
OF
LETHAL
EFFECTS
IN
ANIMALS
AFTER
ACUTE
INHALATION
EXPOSURE
TO
STYRENE
Species,
sex,
strain
Concentration
in
ppm
Exposure
Duration
Effect/
Remarks
Reference
Rat,
f,
m,
S­
D
8407
7218
6621
5911
4814
3766
2983
4
hours
18/
20
f,
20/
20
m,
38/
40
m
+
f
died
5/
10
f,
8/
10
m,
13/
20
m
+
f
died
6/
10
f,
3/
10
m,
9/
20
m
+
f
died
6/
10
f,
1/
10
m,
7/
20
m
+
f
died
1/
10
f,
2/
10
m,
3/
20
m
+
f
died
0/
10
f,
0/
10
m,
0/
20
m
+
f
died
0/
10
f,
0/
10
m,
0/
20
m
+
f
died
BASF
1979b
Rat,
nd,
nd
1300
2000
2500
5000
10,000
30
hours
>
40
hours
16
hours
>
30
hours
8
hours
21
hours
2
hours
8
hours
1
hour
3
hours
LC0
LC100
LC0
LC100
LC0
LC100
LC0
LC100
LC0
LC100
Spencer
et
al.
1942
Rat
(
18
f;
15
m)
5100
1
hour
No
death
during
exposure
Niklasson
et
al.
1993
Rat,
nd,
nd
2270
(
9.7
mg/
l)
2761
(
11.8
mg/
l)
3276
(
14.0
mg/
l)
4
hours
4
hours
4
hours
LC16
LC50
LC84
Shugaev
1969
Rat,
nd,
nd
2700
4
hours
LC50;
abstract
only
Jaeger
et
al.
1974
Rat,
f,
m,
CD
1500
6
hours
0/
20
died
after
repeated
(
subchronic)
exposure
Cruzan
et
al.
1997b
Rat,
f,
m,
CD
1000
6
hours
0/
70
died
after
repeated
(
chronic)
exposure
Cruzan
et
al.
1998
Rat,
m,
S­
D
~
5000
4618
~
3300
6
hours
6
hours
6
hours
LC90
estimated
from
figure
LC50
LC10
estimated
from
figure
Bonnet
et
al.
1982a
Rat,
f,
S­
D
7769
(
33.2
mg/
l)
4
hours
8
hours
0/
10
animals
died
4/
10
animals
died
Lundberg
et
al.
1986
Mouse,
f,
m,
NMRI
1600
1840
1370
4
hours
LC50,
female
and
male
LC50,
females
only
LC50,
males
only
BASF
1979a
Mouse,
f,
m,
NMRI
3766
2983
1528
1420
864
680
4
hours
10/
10
f,
10/
10
m
died
7/
10
f,
9/
10
m
died
3/
10
f,
8/
10
m
died
4/
10
f,
6/
10
m
died
1/
10
f,
0/
10
m
died
0/
10
f,
0/
10
m
died
BASF
1979a
Styrene
NAC:
02/
2004
20
TABLE
3:
SUMMARY
OF
LETHAL
EFFECTS
IN
ANIMALS
AFTER
ACUTE
INHALATION
EXPOSURE
TO
STYRENE
Species,
sex,
strain
Concentration
in
ppm
Exposure
Duration
Effect/
Remarks
Reference
Mouse,
f,
OF1
2429
6
hours
LC50
Bonnet
et
al.
1979b;
1982a
Mouse,
nd,
nd
4142
(
17.7
mg/
l)
4914
(
21.0
mg/
l)
5873
(
25.1
mg/
l)
2
hours
2
hours
2
hours
LC16
LC50
LC84
Shugaev
1969
Mouse
2223
(
9.5
mg/
l)
4
hours
LC50
(
no
details
reported)
Izmerov
et
al.
1982
Mouse,
B6C3F1,
65
f,
23­
27
m
500
250
6
hours
6
hours
5
m,
0
f
died
after
one
exposure
no
death
after
one
exposure
Morgan
et
al.
1993c
Mouse,
B6C3F1,
5
m
500
250
6
hours
6
hours
4/
5
found
moribund
and
sacrificed,
no
death/
moribund
after
one
exposure
Morgan
et
al.
1993c
Mouse,
B6C3F1,
36
f,
36
m
500
250
6
hours
6
hours
6/
36
m,
1/
36
f
died
after
one
exposure
no
death
after
one
exposure
Morgan
et
al.
1993a
Mouse,
B6­
C3F1,
30
m
500
6
hours
2/
30
died
after
one
exposure
Mahler
et
al.
1999
Mouse,
B6­
C3F1,
20
f,
20
m
500
6
hours
no
death
after
one
exposure
Cruzan
et
al.
1997b
Mouse,
CD­
1,
20
f,
20
m
500
250
6
hours
1/
20
m
died
after
one
exposure
no
death
after
one
exposure
Cruzan
et
al.
1997b
Mouse,
B6­
C3F1,
39
m
250
6
hours
4/
39
died
after
one
exposure
Sumner
et
al.
1997
Mouse,
CD­
1,
30
m
250
6
hours
0/
39
died
after
one
exposure
Sumner
et
al.
1997
Guinea
pig,
nd,
nd
1300
2000
2500
5000
10,000
16
hours
40
hours
7
hours
30
hours
6
hours
14
hours
3
hours
8
hours
1
hour
3
hours
LC0
LC100
LC0
LC100
LC0
LC100
LC0
LC100
LC0
LC100
Spencer
et
al.
1942
f:
female;
m:
male;
nd:
no
data;
S­
D:
Sprague­
Dawley.

According
to
an
abstract
(
Jaeger
et
al.
1974),
a
4­
hour
LC50
of
2700
ppm
was
estimated
for
fed
and
fasted
rats.
It
is
further
reported
that
styrene
caused
death
by
pulmonary
irritation
and
edema,
but
no
Styrene
NAC:
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21
further
details
were
presented
(
strain,
no.
of
animals
and
dose
gropus,
treatment
with
inducers,
inhalation
exposure
conditions,
occurrence
of
CNS
effects).

No
deaths
occurred
in
CD
(
Sprague­
Dawley)
rats
exposed
6
hours/
day,
5
days/
week
to
1500
ppm
for
13
weeks
(
Cruzan
et
al.
2001a)
or
to
1000
ppm
for
104
weeks
(
Cruzan
et
al.
1998).
Acute
non­
lethal
(
irritation)
effects
observed
in
these
studies
are
described
in
section
3.2.2.

Studies
with
non­
inhalation
exposure
The
oral
toxicity
of
styrene
was
determined
in
a
total
number
of
57
young
adult
white
rats
raised
from
a
stock
obtained
from
the
Wistar
institute.
Styrene
was
given
by
gavage,
but
it
is
not
clear
whether
the
compound
was
given
undiluted
or
as
an
olive­
oil
or
corn­
oil
solution
emulsified
with
an
aqueous
soltion
of
gum
arabic.
The
oral
toxicity
was
low
as
indicated
by
an
LD50
of
5.0
g/
kg
b.
w.
(
Wolf
et
al.
1956).
In
accordance
with
these
data,
in
another
study
no
death
of
rats
was
observed
after
oral
administration
of
1600
mg/
kg
b.
w.
but
all
rats
died
after
treatment
with
8000
mg/
kg
b.
w.
(
Spencer
et
al.
1942).

Groups
of
six
female
Sprague­
Dawley
rats
were
treated
i.
p.
with
styrene
(
Lundberg
et
al.
1986).
Deaths
were
counted
24
hours
and
14
days
after
the
injection.
The
reported
LD50
of
898
mg/
kg
b.
w.
and
the
95
%
confidence
limits
(
768
 
1051
mg/
kg
b.
w.)
were
identical
at
both
time
points
indicating
that
there
were
no
delayed
deaths
after
intraperitoneal
administration
of
styrene.

3.1.2
Mice
Bonnet
et
al.
(
1979)
studied
the
toxicity
of
styrene
in
female
OF1
mice.
Groups
of
at
least
20
mice
were
exposed
by
whole
body
exposure
in
170
L
dynamic
exposure
chambers
(
as
more
precisely
described
in
Gradiski
et
al.
(
1978)
to
analytically
(
gas
chromatography)
confirmed
vapor
concentrations
of
styrene
for
6
hours.
Animals
were
observed
for
14
days
after
the
end
of
exposure.
The
6­
hour
LC50
for
styrene
was
2429
ppm
(
95
%
confidence
intervals
2352
 
2530
ppm).
The
authors
reported
the
occurrence
of
delayed
deaths
on
the
5th
to
10th
day
after
exposure
but
no
detailed
data
were
presented.

Shugaev
(
1969)
exposed
mice
(
strain,
sex
and
number
of
animals
not
reported)
to
analytically
controlled
styrene
vapor
concentrations
for
2
hours
in
dynamic
flow
exposure
chambers.
A
LC50
of
21.0
mg/
l
(
95
%
confidence
interval
17.8
 
24.8
mg/
l)
(
2761
ppm;
95
%
confidence
interval
4165
 
5803
ppm)
was
calculated.
It
was
also
reported
that
animals
"
often"
did
not
die
during,
but
after
the
exposure.

BASF
(
1979)
conducted
an
acute
inhalation
toxicity
study
with
NMRI
mice.
10
female
and
10
male
mice
per
dose
group
were
exposed
"
whole
body"
to
analytically
(
gas
chromatography)
determined
concentrations
of
680,
864,
1420,
1528,
2983
or
3766
ppm
styrene
for
4
hours
in
a
180
L
dynamic
exposure
chamber.
Survival
of
animals
was
followed
for
14
days
after
the
exposure.
No
deaths
were
observed
at
680
ppm.
At
the
other
conentrations,
deaths
were
observed
1
 
4
days
after
the
exposure.
The
concentration­
response
curve
was
steeper
for
male
mice,
and
males
seemed
more
sensitive
than
females.
LC50
of
1370
ppm
(
95
%
conf.
limit
1087
 
1653
ppm)
for
male
mice
and
of
1840
ppm
(
1486
 
2359
ppm)
for
female
mice
were
determined.
Necroscopy
revealed
acute
dilation
and
congestive
hyperemia
in
the
heart,
enlarged
lung,
and
centrilobular
liver
changes.
Other,
non­
lethal
effects
are
described
in
section
3.2.3.

Without
presenting
further
details,
a
4­
hour
LC50
of
9500
mg/
m
³
(
2223
ppm)
for
mice
is
reported
by
Izmerov
et
al.
(
1982).
Styrene
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In
a
study
to
evaluate
toxic
effects
of
short­
term
exposure
to
B6C3F1
mice,
23
 
27
male
and
65
female
animals
(
8
weeks
old)
per
group
were
exposed
to
analytically
confirmed
concentrations
of
0,
125,
250,
or
500
ppm
styrene
(
99.9
%
pure)
for
6
hours/
day
(
starting
at
7
AM)
for
up
to
14
days
(
Morgan
et
al.
1993c).
Each
animal
was
exposed
individually
in
Hazleton
2000
chambers
and
the
styrene
concentration
was
measured
every
minute
by
infrared
spectophotometry.
After
one
exposure
day,
5
males
exposed
to
500
ppm
died.
Mortality
and
morbidity
were
delayed
after
exposure
and
typically
animals
were
found
dead
or
moribund
the
morning
after
the
exposure
day.
In
an
additional
experiment
in
the
same
study
conducted
only
with
male
mice,
4
of
5
animals
died
after
one
6­
hour
exposure
at
500
ppm.
No
deaths
were
observed
after
one
exposure
in
male
mice
at
lower
concentrations
or
at
any
concentration
in
female
mice.

In
a
further
study
of
the
same
group
(
Mahler
et
al.
1999),
2/
30
male,
8­
week
old
B6C3F1
mice
were
found
dead
one
day
after
a
single
6­
hour
exposure
to
500
ppm
styrene.
Death
was
attributed
to
massive
hepatic
necrosis.
In
another
study,
death
of
4/
39
male
B6C3F1
mice
was
observed
following
one
exposure
to
250
ppm
for
6
hours
(
Sumner
et
al.
1997).

Sex
differences
in
susceptibility
of
B6C3F1
mice
were
further
investigated
(
Morgan
et
al.
1993a).
36
animals
(
8
weeks
old)
per
sex
and
dose
were
exposed
as
described
above
to
0,
125,
250,
or
500
ppm
styrene.
At
500
ppm,
six
male
and
one
female
mice
were
found
dead
or
were
terminated
moribund
after
one
exposure.
No
deaths
occurred
after
one
exposure
to
250
ppm
or
125
ppm.
Necropsy
of
dead
or
moribund
mice
revealed
that
the
liver
of
these
animals
was
engorged
with
blood,
and
microscopic
examination
showed
severe
congestion
and
necrosis
in
the
liver
of
these
animals.

In
a
subacute
toxicity
study
with
CD­
1
and
B6C3F1
mice,
one
of
20
male
CD­
1
mice
exposed
to
500
ppm
died
after
one
6­
hour
exposure
(
Cruzan
et
al.
1997b).

Data
on
lethality
following
repeated
short­
term
exposure
in
Morgan
et
al.
(
1993a),
Morgan
et
al.
(
1993c)
and
Cruzan
et
al.
(
1997)
are
summarized
below
("
studies
with
repeated
exposure").

Studies
with
repeated
inhalation
exposure
In
a
developmental
toxicity
study,
2
of
6
pregnant
BMR/
T6T6
mice
exposed
to
500
ppm
6
hours/
day
from
the
6th
day
of
gestation
on
died
before
the
intended
end
of
the
exposure
phase
on
day
16.
At
750
ppm,
3
of
5
mice
died.
Surviving
dams
carried
a
high
number
of
dead
and
resorbed
fetuses
(
Kankaanpää
et
al.
1980,
see
3.3.2).

B6C3F1
mice
were
exposed
up
to
14
consecutive
days
to
styrene
as
described
above
(
see
3.1.2,
Morgan
et
al.
1993c).
No
animals
died
at
0
and
125
ppm
styrene.
The
highest
mortality
was
observed
at
250
ppm
where
7
males
and
2
females
died
after
two
exposures
and
a
total
of
11
males
and
6
females
after
14
days.
At
500
ppm,
no
deaths
occurred
in
females,
7
males
died
after
2
exposures
and
a
total
of
8
males
died
during
the
14­
day
exposure.

In
a
second
study
investigating
sex­
related
differences
in
susceptibility
of
B6C3F1
mice
to
styrene,
animals
were
exposed
up
to
3
consecutive
days
to
styrene
as
described
above
(
see
3.1.2,
Morgan
et
al.
1993a).
No
control
mice
or
mice
exposed
to
125
ppm
died.
At
250
ppm,
2
males
and
3
females
died
or
were
terminated
moribund
after
2
exposures.
At
500
ppm,
6
males
and
one
female
died
after
one
exposure
but
no
additional
deaths
occurred
after
subsequent
exposures.

The
susceptibility
of
different
strains
of
mice
to
styrene
inhalation
exposure
was
studied
(
Morgan
et
al.
1993b).
8
week
old
B6C3F1,
C57BL/
6,
Swiss
and
DBA/
2
mice
(
20
of
each
sex
and
strain
at
each
dose
group)
were
exposed
to
styrene
(
99.9
%
pure)
at
nominal
but
analytically
confirmed
Styrene
NAC:
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2004
23
concentrations
of
0,
125,
250,
or
500
ppm
in
Hazleton
2000
chambers
for
6
hours/
day
for
4
consecutive
days.
No
animals
of
any
strain
died
at
0
and
125
ppm.
Both
strain
and
sex
differences
in
mortality
(
or
sacrifice
in
moribund
condition)
were
observed.
The
highest
mortality
occurred
in
Swiss
mice
and
both
sexes
proved
similarly
susceptible
(
male:
10/
20
died
at
500
ppm,
female:
3/
20
at
250
ppm,
8/
20
at
500
ppm
died).
Overall
mortality
in
B6C3F1
mice
was
comparable
to
that
in
Swiss
mice
but
there
was
a
clear
sexspecific
effect
with
mortality
in
male
B6C3F1
mice
(
14/
20
at
250
ppm,
3/
20
at
500
ppm
died)
being
much
higher
than
in
females
(
1/
20
at
250
ppm).
Mortality
in
C57/
BL6
mice
also
differed
between
males
(
7/
20
at
250
ppm,
1/
20
at
500
ppm)
and
females
(
1/
20
at
250
ppm
and
500
ppm
each).
Mortality
in
male
B6C3F1
and
C57BL/
6
mice
at
250
ppm
was
higher
than
at
500
ppm.
No
mortality
was
observed
in
male
and
female
DBA/
2
mice.

Sex­
related
differences
in
mortality
were
also
observed
in
B6C3F1
and
CD­
1
mice
in
another
subacute
study
in
which
mice
(
20
per
sex
and
dose
group)
were
exposed
in
0.75
m
³
inhalation
chambers
to
analytically
confirmed
concentrations
of
0,
15,
60,
250
or
500
ppm
styrene
for
6
hours/
day,
5
days/
week
for
14
days
(
Cruzan
et
al.
1997b).
No
deaths
were
observed
at
15
and
60
ppm.
Remarkably,
the
concentration­
response
was
non­
linear
in
female
mice
of
both
strains
as
mortality
after
two
weeks
clearly
was
higher
at
250
ppm
(
7
CD­
1,
10
B6C3F1)
than
at
500
ppm
(
2
CD­
1,
0
B6C3F1).
This
was
not
observed
in
male
mice
of
both
strains
where
mortality
increased
with
increasing
concentration:
One
male
of
each
strain
died
at
250
ppm,
7
male
CD­
1
and
8
B6C3F1
males
died
at
500
ppm.

In
a
further
study
by
Morgan
et
al.
(
1995),
8
week
old
male
and
female
B6C3F1
and
Swiss
mice
were
exposed
to
0,
150
or
200
ppm
styrene
as
described
above
for
6
hours/
day
on
4
consecutive
days.
One
female
Swiss
mouse
died
after
four
exposures
to
200
ppm,
necropsy
revealed
centrilobular
hepatocellular
necrosis
in
this
mouse.
No
deaths
were
observed
in
male
Swiss
or
in
B6C3F1
mice
of
both
sexes.

3.1.3
Guinea
pigs
A
total
number
of
410
guinea
pigs
(
sex,
strain
and
number
of
animals
per
exposure
group
not
reported)
were
exposed
to
styrene
concentrations
ranging
from
1300
ppm
to
10,000
ppm
for
one
hour
to
40
hours
(
Spencer
et
al.
1942).
After
the
exposure
the
animals
were
observed
for
2
 
4
weeks.
No
LC50
but
only
LC0
and
LC100
were
reported
in
the
study.
The
highest
concentration
that
could
be
reached
without
condensation
of
the
chemical
out
of
the
atmosphere
was
10,000
ppm.
At
this
concentration,
no
deaths
were
observed
after
one
hour
of
exposure,
but
all
guinea
pigs
exposed
for
3
hours
died.
At
5000
ppm,
no
animal
died
after
exposure
for
3
hours
but
all
animals
exposed
for
8
hours
died.
At
2500
ppm,
all
animals
survived
a
6­
hour
exposure
and
death
of
all
animals
only
was
observed
when
the
exposure
lasted
14
hours.
All
animals
survived
7
hours
of
exposure
to
2000
ppm
but
all
animals
died
when
exposure
at
this
concentration
was
extended
to
30
hours.
Immediate
deaths
during
or
shortly
after
the
end
of
exposure
were
due
to
the
effect
of
styrene
on
the
CNS.
However,
there
were
also
delayed
deaths
with
pulmonary
edema
and
hemorrhages
that
were
considered
to
develop
as
a
result
of
the
acute
irritating
effect
of
styrene
on
the
lung.

3.1.4
Hamsters
Studies
with
non­
inhalation
exposure
Groups
of
23
male
Syrian
hamsters
were
treated
with
0,
450
or
600
mg/
kg
b.
w.
styrene
in
corn
oil
by
gavage
(
Parkki
1978).
3
of
the
animals
that
had
received
600
mg/
kg
b.
w.
styrene
died
within
24
hours
after
administration.
No
deaths
occurred
at
450
mg/
kg
b.
w.
Styrene
NAC:
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2004
24
3.2
Nonlethal
Toxicity
3.2.1
Nonhuman
primates
Studies
with
repeated
inhalation
exposure
Spencer
et
al.
(
1942)
exposed
4
monkeys
(
two
of
each
sex,
species
not
specified)
to
1300
ppm
styrene
7
 
8
hours/
day,
5
days/
week.
Male
monkeys
received
142
exposures
during
7
months,
females
262
 
264
exposures
over
a
period
of
12
months.
Additionally,
there
were
at
least
3
control
monkeys.
No
further
experimental
details
were
reported.
There
were
no
signs
of
irritation
or
intoxication.
Furthermore,
the
animals
were
reported
to
be
in
excellent
condition
and
to
show
no
gross
or
microscopic
pathological
lesions
(
at
least
lung,
liver,
kidney,
spleen,
pancreas,
adrenals
were
examined).
Blood
examination
revealed
no
differences
between
the
four
exposed
and
three
control
monkeys.

3.2.2
Rats
Female
and
male
Sprague­
Dawley
rats
(
10
of
each
sex/
group;
20
of
each
sex
at
the
highest
concentration)
were
exposed
to
2983,
3766,
4814,
5911,
6621,
7218
and
8407
ppm
styrene
for
4
hours
(
BASF
1979b,
see
3.1.1).
Styrene
was
irritating
to
eyes
and
respiratory
tract
as
indicated
by
closed
eyes,
eye
and
nasal
secretion,
salivation,
and
dyspnoe.
Signs
of
CNS
impairment
were
staggered
or
stalking
gait,
tremors,
lying
on
the
side,
and
narcosis.
Symptoms
were
not
differentiated
with
respect
to
the
individual
exposure
concentrations
except
that
it
was
reported
that
narcosis
was
"
slight"
at
the
lowest
concentration.

Shugaev
(
1969)
reported
that
rats
(
strain,
sex
and
number
of
animals
not
reported)
inhaling
styrene
for
one
hour
at
a
concentration
corresponding
to
the
4­
hour
LC50
(
reported
to
be
2761
ppm)
were
in
a
state
of
deep
narcosis
at
the
end
of
the
1­
hour
exposure.

Effects
on
the
nervous
system
(
somnolence,
tremors,
and
muscular
seizures)
that
preceded
death
were
also
reported
by
Bonnet
et
al.
(
1982).
Lacrymation
was
not
observed
in
styrene
exposed
animals
in
this
study.

Exposure
of
rats
to
1300
ppm
led
to
immediate
irritation
of
eyes
and
nose
with
lacrymation,
salivation,
and
nasal
discharge
(
Spencer
et
al.
1942,
see
3.1.1
for
further
information).
At
this
concentration,
no
other
signs
of
intoxication
were
noted
until
12
hours
of
exposure
when
general
weakness
and
unsteadiness
became
apparent.
These
effects
were
more
evident
at
2000
ppm
but
more
pronounced
signs
of
effects
on
the
CNS
with
loss
of
consciousness
were
only
seen
in
"
some"
animals
after
24
 
30
hours.
At
2500
ppm,
rats
showed
definite
CNS
depression
(
weakness,
stupor,
incoordination,
loss
of
equilibrium,
tremor,
finally
unconsciousness)
after
10
 
12
hours.
Animals
were
"
usually"
completely
unconscious
within
one
hour
exposure
to
5000
ppm
and
even
more
rapid
at
10,000
ppm.
Unconsciousness
was
preceded
by
loss
of
quilibrium,
falling
on
the
side,
running
leg
movements,
tremors
and
convulsions.
In
addition
to
the
immediate
irritant
action
and
the
effects
on
the
CNS,
pulmonary
changes
were
observed.
These
varied
from
slight
congestion
to
hemorrhages,
edema,
exudation,
and
leucocytic
infiltration.
Generally,
the
severity
of
effects
varied
with
the
exposure
concentration
and
duration.
Marked
pulmonary
lesions
were
seen
at
all
concentrations
when
the
exposure
time
was
so
long
that
at
least
some
of
the
exposed
animals
died
following
exposure.
Regarding
other
organs,
liver
and
kidney
changes
were
seen
in
"
comparatively
few
animals";
these
changes
were
most
often
recorded
at
2500
ppm
but
less
frequently
at
higher
concentrations.

Irritation
during
exposure
also
was
observed
in
a
subchronic
study
in
which
female
and
male
CD
(
Sprague­
Dawley)
rats
(
10
females,
10
males
per
group)
were
exposed
to
analytically
(
gas
Styrene
NAC:
02/
2004
25
chromatography)
confirmed
concentrations
of
200,
500,
1000
and
1500
ppm
styrene
in
0.75
m
³
inhalation
chambers
for
6
hours/
day,
5
days/
week
for
13
weeks
(
Cruzan
et
al.
1997b).
Irritation
was
observed
at
all
concentrations
during
exposure.
Signs
reached
from
closed
eyes
at
200
ppm
to
salivation
and
rubbing
of
paws
and
chin
on
the
cage
at
higher
concentrations.
Similar
effects
(
salivation,
restlessness,
hunched
posture)
were
also
observed
in
groups
of
70
male
and
female
CD
rats
each
during
exposure
to
500
and
1000
ppm
for
6
hours/
day,
5
days/
week
for
104
weeks;
generally,
effects
tended
to
decrease
during
each
week
of
exposure
(
Cruzan
et
al.
1998).

Salivation
and
reduced
attention
were
observed
in
a
subacute
study
in
which
10
male
Wistar
rats/
group
were
exposed
6
hours/
day
on
5
consecutive
days
to
an
analytically
confirmed
concentration
of
1500
ppm.
At
the
beginning
of
the
exposure
period,
signs
of
sensory
irritation
were
also
observed
at
500
ppm
but
not
at
150
ppm
(
Jarry
et
al.
2002).

Male
Wistar
rats
were
exposed
to
analytically
(
infrared
spectophotometry)
confirmed
concentrations
of
0,
100,
300,
or
600
ppm
styrene
12
hours/
day,
5
days/
week
for
4
weeks
(
Mäkitie
et
al.
2003).
During
the
exposures,
the
animals
were
mostly
recumbent,
especially
at
600
ppm.
The
authors
saw
no
clear
signs
of
irritation
of
skin,
eye
or
mucous
membranes
at
the
end
of
the
daily
exposures.

TABLE
4:
SUMMARY
OF
ACUTE
NON­
LETHAL
EFFECTS
IN
ANIMALS
AFTER
INHALATION
EXPOSURE
TO
STYRENE
Species
(
strain,
sex,
no./
group)
a
Concentration
(
ppm)
Exposure
Duration
Effect
Reference
Rat
(
Wistar,
m)
2000
ppm
5
hours
Loss
of
consciousness
in
"
many
of
the
test
animals"
Withey
and
Collins
1979
Rat
(
nd;
18
f,
15
m)
1730
ppm
1
hour
Inability
to
suppress
nystagmus
Niklasson
et
al.
1993
Rat
(
Wistar,
10
m)
1500
ppm
500
ppm
6
hours
Reduced
attention,
sensory
irritation
Sensory
irritation
at
start
of
exposure
Jarry
et
al.
2002
Rat
(
nd)
4­
hour
LC50
(
2760
ppm)
1
hour
State
of
deep
narcosis
Shugaev
1969
Mouse
(
Swiss
OF1,
10
m)
549
ppm
4
hours
50
%
decrease
in
immobility
time
in
behavioral
"
despair
swimming"
test
de
Ceaurriz
et
al.
1983
Mouse
(
Swiss
Webster,
m)
156
ppm
3
minutes
RD50
Alarie
1973
Mouse
(
Swiss
OF1,
6
m)
586
ppm
5
minutes
RD50
de
Ceaurriz
et
al.
1981
Mouse
(
Swiss
Webster,
m)
980
ppm
10
minutes
RD50
Bos
et
al.
1992
Mouse
(
NMRI,
10
f,
10
m)
1420
ppm
2983
ppm
3766
ppm
4
hours
Staggered
gait
Apathy
Narcosis
BASF
1979a
Styrene
NAC:
02/
2004
26
Effects
of
styrene
on
the
vestibulo­
and
opto­
oculo
motor
system
effects
were
studied
in
a
total
number
of
18
female
and
15
male
"
pigmented
rats"
(
Niklasson
et
al.
1993).
Each
rat
was
used
for
an
initial
control
experiment
with
no
solvent
exposure
and
one
or
two
subsequent
experiments
with
exposure
to
one
or
two
styrene
concentration
levels.
Exposure
for
each
animal
was
separated
by
at
least
one
week.
Animals
were
exposed
in
a
dynamic
exposure
chamber
to
nominal
concentrations
(
fluctuating
within
about
15
%
as
confirmed
analytically
during
all
exposures)
of
3600;
7400;
13,400;
17,300;
and
21,800
mg/
m
³
of
styrene
(
840,
1730,
3140,
4050,
5100
ppm).
10
minutes
after
initiation
of
exposure,
a
few
eye
saccades
were
provoked
and
registered.
Then,
during
continuous
exposure,
repeated
vestibular
stimulations
in
darkness
and
combined
vestibular
and
optokinetic
stimulations
were
performed
(
lasting
35
minutes)
followed
by
optokinetic
stimulations
(
lasting
15
minutes).
Optokinetic
stimulation
caused
nystagmus
with
a
gain
that
was
reduced
by
styrene
exposure
in
a
concentration­
dependent
manner.
Effects
could
be
observed
at
the
lowest
concentration
of
styrene
applied.
Repeated
vestibular
stimulations
in
darkness
showed
a
prolongation
of
nystagmus
at
4050
and
5100
ppm.
The
combined
vestibular
and
optokinetic
stimulation
caused
no
or
little
nystagmus
in
control
experiments
since
the
visual
input
suppressed
the
vestibular
reaction.
Styrene
exposure
caused
a
concentration­
dependent
inability
to
suppress
the
nystagmus
at
concentrations
 
1730
ppm.

Pulmonary
toxicity
was
studied
in
Sprague­
Dawley
rats
(
Green
et
al.
2001b).
Groups
of
5
female
and
5
male
animals
were
exposed
"
whole
body"
in
3.4
m
³
chambers
to
analytically
(
gas
chromatography)
controlled
concentrations
of
0
or
500
ppm
styrene
for
6
hours.
No
treatment­
related
effects
were
observed
in
the
lung
of
animals
exposed
to
styrene
for
1,
5,
6,
or
10
days.

The
serum
activity
of
sorbitol
dehydrogenase
(
SDH)
was
used
as
an
indicator
of
liver
damage
in
a
study
with
female
Sprague­
Dawley
rats
(
Lundberg
et
al.
1986).
Animals
were
exposed
from
1/
32
to
½
of
the
saturation
concentration
of
styrene
in
air
(
33,200
mg/
m
³
;
7769
ppm)
for
4
hours
and
sacrificed
20
hours
after
the
end
of
exposure.
No
increase
in
serum
SDH­
activity
was
observed
at
any
concentration.

Studies
with
non­
inhalation
exposure
In
the
study
of
Lundberg
et
al.
(
1986),
female
Sprague­
Dawley
rats
were
also
treated
by
i.
p.
injections
of
styrene
in
peanut
oil
at
doses
of
1/
8,
1/
16,
and
1/
32
of
the
LD50
(
898
mg/
kg
b.
w.).
The
serum
activity
of
sorbitol
dehydrogenase
(
SDH)
was
used
as
an
indicator
of
liver
damage;
no
increase
was
observed
at
any
of
the
concentrations.

Studies
with
repeated
inhalation
exposure
The
degeneration
and
regeneration
of
respiratory
mucosa
of
the
trachea
and
the
nose
following
subacute
exposure
of
male
Sprague­
Dawley
rats
was
studied
by
Ohashi
et
al.
(
1986).
Groups
of
10
animals
each
were
exposed
to
analytically
(
gas
chromatography)
determined
concentrations
of
171
±
21.8
ppm
or
1108
±
73.8
ppm
of
styrene
or
air
in
dynamic
exposure
chambers
for
4
hours/
day,
5
days/
week
for
3
weeks.
On
the
first
day
of
the
post­
exposure
period,
the
ciliary
activity
of
the
tracheal
mucosa
showed
some
deterioration
in
the
171­
ppm
group
(
80
%
of
control
value).
There
was
also
an
increased
number
of
dense
bodies
and
small
vacuoles
in
the
epithelial
cells
and
small
compound
cilia
were
observed
but
there
was
no
severe
degeneration
of
epithelial
cells.
In
the
nasal
mucosa,
ciliary
activity
was
reduced
(
41
%
of
control)
and
morphological
alterations
(
ballooning
of
cells,
fewer
ciliated
cells,
increase
of
dense
bodies)
were
seen.
12
weeks
after
the
last
exposure,
the
ciliar
activity
of
the
tracheal
and
nasal
mucosa
was
normal
and
cells
with
an
increased
number
of
dense
bodies
were
only
sporadically
found
in
the
trachea.
At
1200
ppm,
ciliar
activity
of
the
tracheal
mucosa
was
poor
(
18
%
of
control)
the
first
day
after
the
last
exposure,
and
cells
showed
morphological
changes
(
vacuolization,
increased
number
of
dense
bodies,
cytoplasm
Styrene
NAC:
02/
2004
27
protuberances).
In
the
nasal
mucosa,
ciliary
activity
was
disabled
the
first
post­
exposure
day,
there
were
few
ciliated
cells
and
severe
degeneration
of
epithelial
cells.
The
effects
in
the
trachea
largely
resolved
within
the
following
12
weeks
but
in
the
nasal
mucosa
reduced
ciliary
activity
and
morphological
alterations
were
still
detectable.

In
the
nasal
olfactory
epithelium
of
female
and
male
CD
(
Sprague­
Dawley)
rats,
histopathological
changes
were
seen
in
a
subchronic
study
after
exposure
to
500,
1000
and
1500
ppm
for
6
hours/
day,
5
days/
week
for
13
weeks.
At
200
ppm,
no
effects
were
seen.
In
the
same
study,
no
styrenerelated
effects
were
observed
in
the
lungs
at
any
concentration
(
Cruzan
et
al.
1997b).

Effects
on
serum
prolactin
and
dopamine
levels
and
on
hypothalamic
and
striatal
catecholamie
concentrations
were
studied
in
male
Wistar
rats
(
Jarry
et
al.
2002).
Groups
of
10
animals
each
were
exposed
to
analytically
(
gas
chromatography)
confirmed
concentrations
of
0,
150,
500,
and
1500
ppm
styrene
for
6
hours/
day
on
5
consecutive
days.
Parameters
were
measured
immediately
after
the
end
of
exposure
and
after
a
recovery
period
of
24
hours.
No
significant
changes
in
dopamine,
dihydroxyphenylacetic
acid,
noradrenaline,
and
homovanillic
acid
levels
were
observed
in
hypothalamus
and
striatum
of
styrene­
exposed
rats
compared
to
controls.
Also,
no
change
in
prolactin
level
in
serum
was
observed.
The
dopamine
level
in
peripheral
blood
was
higher
at
150
ppm
and
at
1500
ppm
in
the
24­
hour
recovery
group
at
150
ppm,
but
no
concentration­
response
was
obvious;
no
change
was
seen
immediate
after
cessation
of
exposure.

Ototoxicity
of
styrene
was
investigated
in
several
studies.
When
male
Long­
Evans
rats
were
exposed
to
concentrations
between
500
ppm
and
1500
ppm
6
hours/
day,
5
days/
week,
for
4
weeks,
a
permanent
increase
in
auditory
threshold
was
observed
at
mid
frequency
ranges
in
animals
exposed
to
850
and
1000
ppm.
At
higher
concentrations,
the
threshold
was
increased
in
the
mid­
low,
mid­
and
high
frequency
(
Loquet
et
al.
1999).
In
a
further
study,
Long­
Evans
rats
were
exposed
to
1000
ppm,
6
hours/
day,
for
5
days.
Immediately
after
the
end
of
exposure,
cochlear
function
as
tested
by
DPOAE
(
distortion
product
otoacoustic
emissions)
showed
no
decrease
in
DPOAE
amplitude
compared
to
preexposure
However,
2
and
4
weeks
after
the
end
of
exposure,
DPOAE
indicated
a
disruption
of
auditory
function
(
Lataye
et
al.
2003).
Histological
lesions
of
the
cochlea
and
worsening
of
the
electrophysiological
results
(
evoked
potentials
from
the
inferior
colliculus
of
the
cochlea)
after
the
end
of
exposure
was
also
described
in
another
publication
of
the
same
group
in
which
Long­
Evans
rats
were
exposed
to
1000
ppm,
6
hours/
day,
5
days/
week,
for
up
to
4
weeks
(
Campo
et
al.
2001).
In
male
Wistrar
rats
exposed
to
100,
300,
or
600
ppm
styrene
for
12
hours/
day,
5
days/
week,
for
4
weeks,
100
and
300
ppm
caused
no
hearing
impairment
as
measured
by
auditory
brain
response
(
ABR).
At
600
ppm,
a
slight
hearing
loss
(~
3
dB)
was
observed
only
at
the
highest
test
frequeny
of
8
kHz;
cytocochleograms
showed
a
substantial
loss
of
the
outer
hair
cells.
A
synergism
with
exposure
to
noise
(
100
dB)
was
observed
only
when
styrene
was
applied
in
concentrations
that
were
ototoxic
without
noise
(
Mäkitie
et
al.
2003).

3.2.3
Mice
10
female
and
10
male
NMRI
mice
per
dose
group
were
exposed
to
680,
864,
1420,
1528,
2983
or
3766
ppm
styrene
for
4
hours
(
BASF
1979a,
see
3.1.2).
Symptoms
(
not
reported
separately
for
both
sexes)
included
hunched
position
at
exposures
exceeding
1420
ppm
and
rough
fur
at
all
concentrations.
Styrene
was
irritating
to
the
respiratory
tract
and
to
the
eyes
(
intermittent
breathing
at
all
concentrations,
rubbing
of
nose
and
mouth,
secretion
from
nose
and
eyes,
eyes
closed
at
2983
and
3766
ppm).
Signs
of
CNS
impairment
(
staggered
or
stalking
gait)
were
noted
from
1420
ppm
upwards
and
were
more
severe
at
higher
concentrations
with
apathy
and
narcosis
occurring
at
2983
and
3766
ppm.
Styrene
NAC:
02/
2004
28
In
a
subacute
study,
B6C3F1
and
CD­
1
mice
(
20
per
sex
and
dose
group)
were
exposed
in
0.75
m
³
inhalation
chambers
to
analytically
confirmed
concentrations
of
0,
14,
58,
250
or
519
ppm
styrene
for
6
hours/
day,
5
days/
week
for
14
days
(
Cruzan
et
al.
1997b).
Mice
exposed
to
all
concentrations
of
styrene
showed
signs
of
irritation.
At
500
ppm,
animals
adopted
a
prone
position
during
exposure.
Treatment
related
signs
between
exposures
occurred
in
mice
exposed
to
250
or
519
ppm.
These
signs
included
lethargy,
shallow
breathing,
and
unsteady
gait.
250
and
500
ppm
caused
liver
lesions
with
centrilobular
hepatocyte
necrosis
and
associated
changes.
B6C3F1
mice
were
more
susceptible
than
CD­
1
mice.
Mortality
also
occurred
at
these
two
highest
concentrations
(
see
3.1.2).

Sensory
irritation
Male
Swiss
OF1
mice
(
six
at
each
concentration)
were
exposed
"
head
only"
to
at
least
4
different
analytically
(
gas
chromatography)
controlled
concentrations
of
styrene
in
dynamic
200
L
inhalation
test
chambers
for
5
minutes.
For
the
determination
of
the
reflex
decrease
in
respiratory
rate
that
served
as
an
index
of
sensory
irritation,
the
animals
were
secured
in
individual
body
plethysmographs.
An
RD50
of
586
ppm
(
no
confidence
limits
given)
was
determined
(
de
Ceaurriz
et
al.
1981).

In
a
similar
study,
Swiss
Webster
mice
were
exposed
to
styrene
for
3
minutes
(
Alarie
1973).
The
test
substance
was
solubilized
in
polyethylene
glycol
and
aerosols
were
prepared.
An
RD50
of
666
µ
g/
l
(
156
ppm)
(
95
%
conf.
limit
574
 
758
µ
g/
l;
134
 
177
ppm)
was
determined.
In
a
further
study
by
the
same
author
(
cited
in
Bos
et
al.
1992),
Swiss
Webster
mice
were
exposed
for
10
minutes
and
an
RD50
of
980
ppm
(
85
%
conf.
limit
826
 
1297
ppm)
was
determined.

Behavioral
studies
Behavioral
changes
in
a
"
despair
swimming
test"
were
studied
in
Swiss
OF1
mice
(
de
Ceaurriz
et
al.
1983).
Groups
of
10
male
animals
were
exposed
to
analytically
(
gas
chromatography)
confirmed
concentrations
of
413,
610,
807,
or
851
ppm
styrene
or
air
in
200­
L
chambers
for
4
hours.
Immediately
afterwards,
total
duration
of
immobility
during
a
3­
minute
period
in
a
"
despair
swimming
test"
was
determined.
Immobility
was
defined
as
cessation
of
struggling
to
get
out
of
the
water.
Exposure
to
solvents
including
styrene
caused
a
dose­
dependent
decrease
in
duration
of
immobility
as
compared
to
the
corresponding
controls.
In
case
of
styrene,
the
mean
duration
of
immobility
decreased
significantly
by
28,
60,
77,
or
83
%
of
control
at
the
concentrations
noted
above.
An
ID50
(
50
%
decrease
in
immobility)
of
549
ppm
(
95
%
confidence
interval
522
 
573
ppm)
was
calculated.

Immunological
effects
It
is
reported
that
female
BALB/
c
mice
(
6
per
group)
exposed
to
300
ppm
but
not
to
200
or
100
ppm
styrene
showed
an
increase
in
IgM
response
of
lung­
associated
lymph
nodes
in
an
anti­
SRBC
(
sheep
red
blood
cells)
assay.
Furthermore,
the
ex
vivo
release
of
 ­
interferon
from
lung­
associated
lymph
nodes
decreased
with
increasing
concentration
of
styrene
but
was
higher
than
control
values
at
all
styrene
concentrations.
No
effects
were
seen
in
the
spleen
(
Ban
et
al.
2003).
An
evaluation
of
the
results
is
not
possible
since
the
duration
of
exposure
is
not
reported.

Studies
with
repeated
inhalation
exposure
Pulmonary
toxicity
was
studied
in
CD­
1
mice
(
Green
et
al.
2001b).
Groups
of
5
female
and
5
male
mice
were
exposed
"
whole
body"
in
3.4
m
³
chambers
to
analytically
(
gas
chromatography)
controlled
concentrations
of
0,
40
or
160
ppm
styrene
for
6
hours.
At
40
ppm,
in
mice
killed
immediately
after
exposure,
there
was
evidence
of
necrosis
and
loss
of
cells,
believed
to
be
Clara
cells,
from
large
bronchioles,
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while
Clara
cells
in
the
terminal
bronchioles
were
not
overtly
affected.
At
160
ppm,
no
significant
effect
was
seen
at
this
time
point.
In
animals
killed
18
hours
after
exposure,
minimal
necrosis
but
treatmentrelated
focal
loss
of
cytoplasm
from
non­
ciliated
cells
was
observed,
predominantly
at
the
terminal
bronchiolar
area.
Females
seemed
slightly
more
affected
than
males.
The
lesions
observed
at
this
time
point
were
similar
at
both
styrene
concentrations.
In
mice
that
had
received
5­
bromo­
2­
deoxyuridine
3
days
prior
to
sacrifice,
no
evidence
of
an
increase
in
cell
replication
in
the
alveoli,
terminal
or
large
bronchioles
was
observed
after
one
day
of
exposure
to
styrene.

In
a
further
study
of
the
authors,
the
toxicity
of
styrene
to
the
nasal
epithelium
was
studied
in
male
CD­
1
mice.
20
mice
per
dose
group
were
exposed
to
analytically
(
gas
chromatography)
confirmed
concentrations
of
0,
40
or
160
ppm
styrene
for
6
hours/
day
for
3
days.
Mice
were
killed
17
hours
after
the
last
exposure.
At
160
ppm,
degenerative,
mostly
focal
changes
in
the
olfactory
tissue
were
observed
in
all
mice.
Most
obvious
was
the
presence
of
cellular
and
serious
fluid
exudate
in
the
airways
of
the
nasal
passages
in
the
olfactory
epithelium
of
the
dorsal
meatus.
Atrophy
of
the
olfactory
mucosa
with
loss
of
cellular
organisation
and
focal
decrease
of
Bowman
´
s
glands
were
also
observed.
At
40
ppm,
animals
were
largely
unaffected,
only
one
mouse
showed
minimal
atrophy
of
the
olfactory
mucosa
(
Green
et
al.
2001a).

Effects
on
the
nasal
passages
and
the
lung
were
also
investigated
by
Cruzan
et
al.
(
2001).
Groups
of
55
male
CD­
1
mice
were
exposed
to
analytically
(
gas
chromatography)
confirmed
concentrations
of
0,
40
or
80
ppm
styrene
in
2.43
m
³
inhalation
chambers
for
6
hours/
day,
5
days/
week
for
up
to
13
weeks.
A
subgroup
of
5
mice
was
terminated
after
one
exposure
(
and
further
subgroups
after
repeated
exposures).
In
the
nasal
olfactory
epithelium,
single
cell
necrosis
was
found
after
a
single
exposure
to
80
ppm,
but
not
to
40
ppm.
No
changes
were
observed
in
the
lung
at
40
or
80
ppm
up
to
the
end
of
the
13th
week.

3.2.4
Guinea
pigs
In
the
study
of
Spencer
et
al.
(
1942),
guinea
pigs
generally
showed
the
same
reactions
to
styrene
exposure
than
rats:
irritation
of
mucous
membranes,
CNS­
depression
and
pulmonary
changes
(
see
3.2.2).
The
effects
occurred
at
the
same
concentrations,
however,
it
was
reported
that
under
comparable
conditions
of
exposure
the
pulmonary
changes
were
more
severe
in
guinea
pigs
than
in
rats.

Studies
with
repeated
inhalation
exposure
In
a
study
on
ototoxicity
of
styrene,
pigmented
guinea
pigs
were
exposed
to
1000
ppm,
6
hours/
day,
for
5
days.
Cochlear
function
as
tested
by
DPOAE
(
distortion
product
otoacoustic
emissions)
was
measured
before
exposure,
immediately
afterwards,
and
2
and
4
weeks
after
exposure.
In
contrast
to
the
observations
made
in
rats
similarily
exposed
in
the
same
study
(
see
3.2.2),
no
disruption
of
auditory
function
was
observed
in
guinea
pigs
(
Lataye
et
al.
2003).

3.2.5
Rabbits
Studies
with
repeated
inhalation
exposure
In
the
study
of
Spencer
et
al.
(
1942),
2
rabbits
(
strain,
sex,
and
further
experimental
details
not
reported)
received
up
to
126
exposures
to
2000
ppm
for
7.5
 
8
hours/
day,
5
days/
week
The
rabbits
were
reported
not
to
be
affected
by
these
exposures.
In
contrast,
rats
and
guinea
pigs
showed
marked
eye
and
nose
irritation
during
the
exposures.
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30
3.3
Developmental/
Reproductive
Toxicity
Data
are
available
from
studies
with
rats,
mice,
rabbits,
and
hamsters
(
for
review,
see
Brown
1991;
2000;
IARC
2002).

3.3.1
Rats
No
studies
were
identified
concerning
the
effects
of
a
single
inhalation
exposure
to
styrene
on
developmental
or
reproductive
toxicity.

Studies
with
non­
inhalation
exposure
Sprague­
Dawley
rats
were
treated
on
the
11th
day
of
gestation
with
a
single
dose
of
300
mg/
kg
styrene
in
corn
oil
by
gavage
(
Daston
et
al.
1991).
The
dose
led
to
maternal
toxicity
(
decreased
body
weight,
reduced
food
intake)
but
no
effects
on
pre­
and
postimplantation
losses,
malformations
and
variations
were
observed
on
gestation
day
20.

In
a
carcinogenicity
study
(
Ponomarkov
and
Tomatis
1978),
female
BD
IV
rats
were
given
1350
mg/
kg
b.
w.
styrene
in
olive
oil
by
gavage
on
day
17
of
gestation
(
followed
by
weekly
treatment
of
the
offsprings
with
500
mg/
kg
b.
w.
after
weaning).
Preweaning
mortality
in
offsprings
from
styrene­
treated
dams
was
non­
significantly
higher
(
10
%)
than
in
the
control
group
(
2.5
%).
There
was
no
effect
on
litter
size
at
birth,
postweaning
survival,
or
body
weight
development.

Studies
with
repeated
inhalation
exposure
A
"
segment
II"
developmental
toxicity
study
was
conducted
by
Murray
et
al.
(
1978).
Female
Sprague­
Dawley
rats
were
exposed
to
0,
300
or
600
ppm
for
7
hours/
day
during
day
6
 
15
of
gestation.
Both
styrene
concentrations
were
maternally
toxic
(
decreased
body
weight
gain
and
decreased
food
consumption).
A
greater
incidence
of
skeletal
variations
but
no
other
embryo
or
fetal
developmental
effects
were
observed
in
offsprings
of
styrene­
treated
dams
compared
to
controls.
The
authors
reported
that
the
observed
incidence
was
within
the
range
(
number
not
reported)
of
historical
controls.

Postnatal
neurochemical
changes,
growth,
and
physical
landmarks
of
development
were
studied
in
offsprings
of
female
Wistar
rats
that
had
been
treated
with
0,
50
or
300
ppm
6
hours/
day
during
gestation
day
6
 
20
(
Katakura
et
al.
2001).
To
adjust
for
nutritional
effects,
pair­
fed
and
ad­
libitum
controls
were
included.
Food
consumption
of
dams
was
decreased
at
300
ppm,
but
maternal
weight
gain
was
not
significantly
different
from
that
of
both
control
groups.
Litter
size,
birth
weight
and
sex
ratio
were
found
to
exhibit
no
effects
within
the
variation
range
studied.
At
300
ppm,
an
increased
neonatal
death
rate
was
observed
compared
to
the
pair­
fed
control
group.
Postnatal
development
(
incisor
eruption,
eye
opening,
air
righting
reflex)
was
also
delayed
at
300
ppm
compared
to
both
control
groups.
Furthermore,
neurochemical
alterations
were
observed
as
indicated
by
a
significantly
decreased
5­
hydroxytryptamine
concentration
in
the
cerebrum
at
postnatal
day
21
in
offspring
exposed
in
utero
to
300
ppm
styrene.
These
results
suggest
that
the
offspring
were
susceptible
to
the
effects
of
styrene
on
a
few
developmental
landmarks
and
the
results
support
previous
findings
of
alterations
in
postnatal
development
in
offsprings
of
styrene
treated
dams
(
Kishi
et
al.
1992;
1995).

Studies
with
non­
inhalation
exposure
In
the
study
of
Murray
et
al.
(
1978)
(
see
above),
pregnant
rats
were
also
treated
with
90
or
150
mg/
kg
b.
w.
styrene
by
gavage
twice
daily
from
the
6th
to
15th
day
of
gestation.
Compared
to
non­
treated
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31
controls,
maternal
weight
gain
was
reduced
and
the
incidence
of
skeletal
variation
was
higher
in
styreneexposed
groups.
However,
the
authors
reported
that
the
observed
incidences
were
within
the
range
(
numbers
not
reported)
of
historical
controls.

In
a
further
segment­
II
teratology
study,
albino
rats
were
treated
orally
with
250
or
400
mg/
kg
b.
w.
styrene
in
peanut
oil
on
gestation
days
6
 
15
(
Srivastava
et
al.
1990).
At
400
mg/
kg
b.
w.,
maternal
toxicity
(
severe
reduction
in
weight
gain),
increased
pre­
and
postimplantation
losses
and
reduction
in
fetal
weight
was
observed
but
no
gross
or
structural
defects.
No
maternal
toxicity
and
embryo/
fetotoxic
or
developmental
effects
were
seen
at
250
mg/
kg
b.
w.

Maternal
toxicity
(
severe
reduction
in
body
weight,
but
no
deaths)
were
also
seen
in
a
further
study
in
which
Sprague­
Dawley
rats
were
administered
1147
mg/
kg
b.
w.
styrene
on
gestation
day
6
 
15
(
Chernoff
et
al.
1990).
No
differences
compared
to
control
were
observed
with
respect
to
fetal
weight,
embryo/
fetal
death,
and
skeletal
or
soft
tissue
malformations
or
variations.

Interactions
of
styrene
exposure
with
protein
malnutrition
were
studied
by
Khanna
et
al.
(
1991).
Rats
were
given
a
diet
of
20
%
casein
or
8
%
casein
throughout
pregnancy
and
lactation,
with
or
without
100
mg/
kg
b.
w.
of
styrene
given
orally
from
day
6
of
gestation
onward.
Low
casein
diet
alone
led
to
a
reduction
in
postnatal
weight
gain
and
a
delay
in
development
(
eye
opening,
behavioral
responses).
These
effects
were
more
pronounced
in
pups
of
dams
that
were
treated
with
styrene
and
receiving
the
low
casein
diet.
These
pups
also
showed
a
decrease
in
brain
enzyme
activities.
No
such
effects
were
seen
in
offsprings
of
dams
that
were
given
the
normal
casein
diet.

In
a
three­
generation
reproductive
toxicity
study,
female
and
male
rats
were
continuously
exposed
to
125
or
250
ppm
styrene
in
drinking
water
(
7
 
10
mg/
kg
b.
w.
or
14
 
21
mg/
kg
b.
w.,
respectively).
Water
consumption
was
reduced
in
both
groups.
In
high
dose
females,
body
weight
gain
was
slightly
reduced
but
no
consistent
treatment­
related
effects
on
pup
survival,
pup
body
weights,
or
developmental
parameters
could
be
observed
(
Beliles
et
al.
1985).

3.3.2
Mice
In
a
carcinogenicity
study
(
Ponomarkov
and
Tomatis
1978),
female
O20
and
C57Bl
mice
were
given
styrene
in
olive
oil
by
gavage
on
day
17
of
gestation
(
O20:
1350
mg/
kg
b.
w.;
C57Bl:
300
mg/
kg
b.
w.
each
followed
by
weekly
treatment
of
the
offsprings
with
the
same
dose
after
weaning).
In
O20
mice,
the
maximum
tolerated
dose
was
exceeded.
There
was
no
effect
on
litter
size
at
birth
or
on
body
weight
gain
but
survival
prior
to
weaning
was
decreased
in
the
offspring
of
treated
animals.
In
C57Bl
mice,
no
effects
on
maternal
mortality,
litter
size
or
preweaning
mortality
was
observed.

Studies
with
repeated
inhalation
exposure
Pregnant
female
BMR/
T6T6
mice
were
exposed
to
an
analytically
(
infrared
spectophotometry)
controlled
concentration
of
250
ppm
styrene
or
air
(
control)
for
6
hours/
day
from
the
6th
to
the
16th
day
of
gestation
and
sacrificed
the
last
day
of
exposure
(
Kankaanpää
et
al.
1980).
The
number
of
dead
or
resorbed
fetuses
was
higher
in
styrene
exposed
mice
(
26.9
%)
compared
to
controls
(
18.2
5)
but
did
not
reach
statistical
significance
(
0.05
<
p
<
0.10).
Among
94
live
fetuses
in
the
styrene
exposed
group,
3
were
malformed
(
rib
fusion,
extra
rib),
in
the
control
group,
among
76
live
fetuses,
one
was
malformed
(
exteriorization
of
the
liver).
No
statistical
evaluation
of
these
results
was
presented
in
the
report,
but
it
seems
unlikely
that
the
effect
would
have
been
significant.
In
preliminary
experiments
with
exposure
to
500
and
750
ppm,
high
maternal
mortality
was
observed
(
250
ppm:
2/
6;
750
ppm:
3/
5
died
before
gestation
day
Styrene
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32
16).
Surviving
mice
carried
a
high
number
of
dead
and
resorbed
fetuses
(
fetal
death
rate
at
250
ppm:
47
%;
at
750
ppm:
95
%).

3.3.3
Rabbits
Studies
with
repeated
inhalation
exposure
A
"
segment
II"
developmental
toxicity
study
was
conducted
by
Murray
et
al.
(
1978).
Female
New
Zealand
white
rabbits
were
exposed
to
0,
300
or
600
ppm
for
7
hours/
day
during
day
6
 
18
of
gestation.
No
maternal
toxicity,
no
embryo­/
fetotoxicity
and
no
teratogenic
effects
were
evident
in
styrene
exposed
groups.
Compared
to
the
concurrent
control,
a
higher
incidence
of
a
single
skeletal
variation
was
observed
at
600
ppm.
However,
the
authors
state
that
the
observed
incidence
was
within
the
range
of
historical
controls.
It
is
reported
(
Brown
et
al.
2000)
that
styrene
is
not
maternally
toxic
to
rabbits
at
concentrations
up
to
1000
ppm
so
the
validity
of
the
study
seems
to
be
limited.

3.3.4
Hamsters
Studies
with
repeated
inhalation
exposure
Pregnant
Chinese
hamsters
were
exposed
to
analytically
(
infrared
spectophotometry)
controlled
concentrations
of
300,
500,
750,
and
1000
ppm
styrene
or
air
(
control)
for
6
hours/
day
from
the
6th
to
the
18th
day
of
gestation
and
sacrificed
the
last
day
of
exposure
(
Kankaanpää
et
al.
1980).
No
fetal/
embryotoxic
effects
or
malformations
were
seen
at
300,
500,
and
750
ppm.
At
1000
ppm,
the
only
effect
seen
was
a
significantly
increased
number
of
dead
or
resorbed
fetuses
(
66
%)
compared
to
26.2
%
in
the
control
group.

3.4
Genotoxicity
A
large
number
of
studies
have
been
published
in
which
genotoxic
effects
(
including
DNAadducts
of
styrene
were
investigated
in
vitro
and
in
vivo.
These
studies
have
been
extensively
evaluated
and
summarized
in
a
number
of
reviews
(
ATSDR
1992;
Cohen
et
al.
2002;
IARC
1994;
IARC
2002;
Scott
and
Preston
1994;
Vodicka
et
al.
2002;
WHO
1983;
WHO
2000).
Since
a
detailed
description
of
the
findings
from
these
studies
is
beyond
the
scope
of
this
TSD,
results
described
in
these
reviews
are
summarized.

Styrene
itself
does
not
react
with
DNA
or
other
nucleophiles
in
vitro
in
the
absence
of
metabolic
activation.
The
genotoxic
potential
of
styrene
depends
on
the
ability
of
the
in
vitro
or
in
vivo
system
to
metabolize
styrene
to
reactive
elecrophiles.
The
main
primary
metabolite
of
styrene
in
mammals
is
styrene
oxide
(
SO),
an
electrophilic
epoxide
that
is
able
to
form
covalent
adducts
with
nucleophiles
such
as
DNA.
In
accordance
with
this,
SO
binds
to
DNA
and
shows
genotoxic
activity
in
vitro
and
in
vivo.
The
potency
of
styrene
in
metabolically
active
test
systems
is
dependent
on
a
number
of
additional
factors,
e.
g.,
the
ability
to
detoxify
SO
to
non­
reactive
metabolites
and
to
repair
initial
DNA­
lesions.

In
several
studies
with
bacteria
test
systems
(
different
strains
of
Salmonella
typhimurium),
styrene
was
not
mutagenic
in
the
absence
of
exogenous
metabolic
activation
system.
In
the
presence
of
such
activation
system,
in
some
but
not
all
studies,
mutagenic
effects
were
observed.
Styrene
induced
gene
conversion
and
mitotic
recombination
in
yeast
cells
in
vitro
and
in
a
host­
mediated
assay
using
mice
as
hosts.
In
Drosophila
melanogaster,
somatic
mutations
were
only
observed
in
insecticide
resistant
strains
that
have
a
high
bioactivation
capacity.
Styrene
NAC:
02/
2004
33
In
in
vitro
tests
using
rodent
cells,
styrene
induced
sister
chromatid
exchanges
(
SCE)
in
a
study
using
whole­
blood
rat
lymphocyte
cultures.
An
increase
in
SCE
was
also
observed
in
several
studies
with
Chinese
hamster
ovary
(
CHO)
cells,
mostly
in
the
presence
of
exogenous
metabolic
activation
(
S9
mix,
human
erythrocytes),
and
a
further
increase
was
observed
by
the
addition
of
cyclohexane
epoxide,
an
epoxide
hydrolase
inhibitor.
Furthermore,
styrene
induced
chromosomal
aberrations
(
CA)
in
Chinese
hamster
lung
(
CHL)
cells
in
the
presence
but
not
in
the
absence
of
exogenous
metabolic
activation.

In
vivo
assays
with
rodents
were
performed
with
rats,
mice,
and
hamsters.
Chromosomal
aberrations
(
CA)
and
polyploidy,
but
not
aneuploidy,
in
bone
marrow
were
observed
in
one
inhalation
study
in
which
Wistar
rats
were
exposed
to
300
ppm
styrene
(
6
hours/
day,
5
days/
week,
9
weeks).
No
increase
in
CA
was
observed
in
other
inhalation
studies
in
bone
marrow
of
Sprague­
Dawley
rats
(
600,
1000
ppm,
6
hours/
day,
5
days/
week,
12
months),
in
blood
and
spleen
lymphocytes
of
B6C3F1
mice
(
124
 
491
ppm,
6
hours/
day,
14
days),
and
in
bone
marrow
of
Chinese
hamsters
(
300
ppm,
6
hours/
day,
4
days
or
5
days/
week
for
3
weeks).
Also,
no
increase
in
CA
in
bone
marrow
was
observed
following
oral
administration
of
styrene
in
CD­
1
mice
(
1000
mg/
kg
once;
500
mg/
kg
for
4
days,
200
mg/
kg
for
70
days)
or
i.
p.
administration
in
C57/
BL6
mice
(
50
 
1000
mg/
kg).
Induction
of
micronuclei
(
MN)
in
bone
marrow
occurred
following
i.
p.
treatment
of
C57BL6
mice
(
250
 
1500
mg/
kg),
but
not
in
blood
erythrocytes
and
spleen
lymphocytes
of
B6C3F1
mice
following
inhalation
exposure
(
124
 
491
ppm,
6
hours/
day,
14
days)
or
in
bone
marrow
of
hamsters
after
i.
p.
administration
(
1000
mg/
kg).
Sister
chromatid
exchanges
(
SCE)
were
not
observed
in
blood
lymphocytes
of
F344
rats
after
inhalation
of
styrene
(
150
 
1000
ppm,
6
hours
/
day,
5
days/
week,
up
to
4
weeks).
In
mice,
however,
an
increase
in
SCE
in
liver,
bone
marrow,
alveolar
macrophages,
lung,
blood
and
spleen
lymphocytes
was
observed
after
single
(
922
ppm,
6
hours)
or
repeated
(
387
ppm,
6
hours/
day,
4
days)
inhalation
of
styrene
in
BDF1
mice
and
in
C57/
Bl6
and
B6C3F1
mice
after
i.
p.
administration
of
styrene.
In
a
recently
published
study
that
is
not
included
in
the
reviews
mentioned
above,
no
evidence
of
clastogenicity
in
bone
marrow
of
NMRI
mice
was
observed
following
styrene
inhalation
exposure
at
750
mg/
m
³
(
175
ppm)
or
1500
mg/
m
³
(
350
ppm),
6
hours/
day,
for
1,
3,
7,
14,
or
21
consecutive
days
(
Engelhardt
et
al.
2003).

DNA
strand
breaks
were
detected
in
a
comet
assay
in
liver,
kidney,
lymphocytes,
and
bone
marrow
of
C57/
Bl6
mice
following
single
i.
p.
administration
of
250
or
350
mg/
kg
b.
w.
styrene.

DNA­
adducts
of
SO
have
been
detected
in
several
studies
with
rodents.
In
CD­
1
mice
and
Sprague­
Dawley
rats
exposed
by
inhalation
to
160
ppm
14C­
styrene
for
6
hours,
an
increase
of
N7­
guanine
DNA­
adducts
was
found
in
lung
in
liver
of
both
species
42
hours
later.
More
recent
studies
use
32Ppostlabelling
assays
to
detect
and
quantify
different
DNA­
adducts.
A
dose
respondent
increase
in
N7­
and
O6­
guanine
DNA­
adducts
of
SO
could
be
detected
3
hours
after
a
single
i.
p.
administration
of
styrene
(
up
to
450
mg/
kg
b.
w.)
to
NMRI
mice.
The
adduct
level
in
the
lungs
was
higher
than
that
in
liver.
Similar
results
were
obtained
in
a
further
study
with
NMRI
in
which
animals
were
exposed
by
inhalation
to
175
or
350
ppm
styrene,
6
hours/
day,
7
days/
week,
for
1
 
21
days.
The
adduct
levels
increased
linearily
with
time.

Differences
in
adduct
levels
between
rats
and
mice
with
respect
to
differences
in
carcinogenicity
between
these
two
species
were
studied
by
Otteneder
et
al.(
2002).
In
samples
of
liver
tissue
from
CD
rats
treated
with
styrene
via
inhalation
for
2
years,
levels
of
O6­
SO­
guanine
adducts
were
above
the
limit
of
detection
only
in
the
highest
dose
group
(
1000
ppm).
It
was
concluded
that
rat
liver
is
able
to
tolerate
a
comparatively
high
level
of
styrene­
derived
DNA­
adducts
without
a
detectable
increase
of
the
tumor
rate.
Further,
CD­
1
mice
were
exposed
6
hours/
day,
5
days/
week,
2
weeks,
to
0,
40,
or
160
ppm
styrene,
CD
rats
were
exposed
to
0
or
500
ppm.
No
increase
in
O6­
SO­
guanine
adducts
could
be
detected
in
any
of
the
lung
samples
despite
the
observation
from
carcinogenicity
studies
that
styrene
increases
the
rate
of
lung
tumors
in
mice
but
not
in
rats.
The
authors
concluded
that
species­
and
site­
specific
tumor
formation
by
Styrene
NAC:
02/
2004
34
styrene
is
not
reflected
by
DNA­
adducts
in
tissues.
However,
this
conclusion
has
been
questioned
because
the
expected
levels
of
O6­
SO­
guanine
adducts
may
be
far
below
the
detection
limit
(
Vodicka
et
al.
2002).

3.5
Carcinogenicity
No
carcinogenicity
studies
with
single
inhalation
exposure
of
animals
have
been
found
in
the
literature.

Studies
with
non­
inhalation
exposure
No
increase
in
tumor
incidence
compared
to
"
vehicle
only"
controls
was
observed
in
40
female
and
40
male
Sprague­
dawley
rats
given
a
single
subcutaneous
dose
of
50
mg
styrene
per
animal
in
olive
oil
or
four
i.
p.
doses
of
50
mg
per
animal
in
olive
oil
over
a
period
of
4
months
(
Conti
et
al.
1988).

Studies
with
repeated
inhalation
exposure
Carcinogenicity
studies
with
repeated
inhalation
or
oral
exposure
were
performed
with
different
strains
of
rats
(
TABLE
5)
and
mice
(
TABLE
6).
A
detailed
review
with
a
critical
comprehensive
evaluation
has
recently
been
published
(
Cohen
et
al.
2002).

Rats
Sprague­
Dawley
rats
(
initially
96
females,
96
males)
were
exposed
to
0,
600
or
1000
­
1200
ppm
styrene
in
air
for
6
hours/
day,
5
days/
week
for
20.7
months
(
females)
or
18.3
months
(
males).
The
higher
concentration
was
reduced
from
1200
ppm
to
1000
ppm
after
2
months
because
of
excessive
treatmentrelated
effects
(
decreased
weight
gain)
in
male
rats
(
Jersey
et
al.
1978).
The
authors
observed
an
incidence
(
7/
85
animals)
of
mammary
adenocarcinoma
at
600
ppm
in
females
that
was
statistically
higher
compared
to
the
corresponding
control
(
1/
85)
but
was
within
the
range
of
historical
controls
(
0
 
9
%).
There
was
no
significant
association
at
1000
ppm.
The
incidence
of
lymphosarcomas
and
leukemia
in
females
was
identical
at
both
styrene
exposures
and
was
not
statistically
higher
than
in
the
corresponding
control
but
exceeded
that
observed
in
historical
controls.

In
another
inhalation
study,
Sprague­
Dawley
rats
(
30
females
and
30
males)
were
exposed
to
25,
50,
100,
200
or
300
ppm
styrene
for
4
hours/
day,
5
days/
week
for
52
weeks.
The
study
was
terminated
when
the
survival
rate
reached
50%
in
at
least
one
experimental
group
(
Conti
et
al.
1988).
Inhalation
exposure
to
styrene
was
associated
with
a
higher
incidence
of
overall
mammary
tumors
(
benign
and
malignant
combined,
control:
57
%,
exposed:
70
 
83
%)
and
of
malignant
mammary
tumors
alone
(
control:
10
%,
exposed:
13
 
40
%).
However,
in
the
colony
of
rats
used
the
incidence
of
mammary
tumors
was
quite
high
and
fluctuating
and
there
was
no
clear
concentration­
response.

In
the
most
recently
conducted
inhalation
study,
groups
of
60
female
and
60
male
CD
(
Sprague­
Dawley
derived)
rats
were
exposed
to
0,
50,
200,
500
or
1000
ppm
styrene
for
6
hours/
day,
5
days/
week
for
104
weeks
(
Cruzan
et
al.
1998).
In
female
rats,
there
was
no
increase
of
any
tumor
or
in
the
number
of
tumor­
bearing
rats
in
the
exposed
groups
compared
to
controls;
there
was
a
decrease
in
pituitary
adenomas
and
mammary
adenocarcinomas.
In
males,
a
significant
trend
for
an
increase
in
the
incidence
of
interstitial
cell
testicular
adenomas
was
observed
(
control:
3.3
%,
exposed
3.3
 
11.5
%).
However,
all
rates
were
within
the
range
of
historical
controls
(
0
 
13.5
%),
none
of
the
incidences
were
significantly
different
from
controls
by
pairwise
comparison,
and
no
treatment­
related
increase
in
histological
alterations
(
cell
hyperplasia,
seminiferous
tubular
atrophy)
typically
associated
with
chemically
induced
interstitial
cell
Styrene
NAC:
02/
2004
35
tumors
was
observed.
Therefore,
the
authors
judged
the
observed
effect
to
be
incidental
and
not
related
to
styrene
exposure.

TABLE
5:
SUMMARY
OF
RESULTS
ON
STUDIES
OF
CANCER
IN
RATS
TREATED
WITH
STYRENE
*

Exposure
Strain
Route
Concentration
or
dose
Duration
Tumor
incidence
statistically
elevated,
type
of
tumor
Reference
SD
Inhalation
600,
1000
­
1200
ppm
6
hours/
day,
5
days/
week
f:
18.3
months,
m:
20.7
months
Yes,
for
mammary
adenocarcinoma
Jersey
et
al.
1978
SD
Inhalation
25,
50,
100,
200,
300
ppm
4
hours/
day,
5
days/
week
52
weeks
Yes,
for
combined
mammary
tumors
and
for
malignant
mammary
tumors
only
Conti
et
al.
1988
CD
(
SDderived
Inhalation
50,
200,
500,
1000
ppm
6
hours/
day,
5
days/
week
104
weeks
Yes,
for
testicular
tumors
Cruzan
et
al.
1998
SD
Gavage
50,
250
mg/
kg
b.
w.
4
or
5
days/
week
No
Conti
et
al.
1988
SD
Drinking
water
125,
250
ppm
a
2
years
No
Beliles
et
al.
1985
SD
Drinking
water
15
 
19
mg/
animal
x
day
561
days
No
Oettel
and
Schulze
1962
F
344/
N
Gavage
500
mg/
kg
b.
w.

1000,
2000
mg/
kg
b.
w.
5
days/
week;
103
weeks
5
days/
week,
78
weeks
No
NCI
1979b
F
344/
N
Gavage
175,
350,
700
mg/
kg
b.
w.
3
days/
week,
79
weeks
No
NCI
1979a
BDIV
Gavage
500
mg/
kg
b.
w.
once
a
week
b
No
Ponomarkov
and
Tomatis
1978
*
Table
from
Cohen
et
al.
(
2002),
modified
and
supplemented;
a:
doses
at
125
ppm
were
7.7
mg/
kg
b.
w.
in
males
and
12
mg/
kg
b.
w.
in
females,
at
250
ppm,
14
mg/
kg
b.
w.
in
males
and
21
mg/
kg
b.
w.
in
females;
b:
Dams
were
administered
1350
mg/
kg
b.
w.
styrene
on
day
17
of
gestation,
offspring
received
500
mg/
kg
b.
w.
after
weaning
once
weekly
for
lifetime.

Studies
with
non­
inhalation
exposure
Six
studies
were
performed
in
which
rats
were
exposed
orally
by
gavage
or
via
drinking
water
to
styrene
(
Beliles
et
al.
1985;
Conti
et
al.
1988;
NCI
1979b;
Oettel
and
Schulze
1962;
Ponomarkov
and
Tomatis
1978)
or
to
a
mixture
of
70
%
styrene
and
30
%
ß­
nitrostyrene
(
NCI
1979a).
None
of
these
studies
Styrene
NAC:
02/
2004
36
did
show
an
association
between
exposure
to
styrene
and
the
development
of
tumors.
However,
it
must
be
noted
that
none
of
these
studies
are
fully
acceptable
under
current
standards
(
number
of
animals,
maximum
tolerated
dose
not
reached,
low
survival,
exposure
to
mixture,
or
only
weekly
dosing).

Mice
With
mice,
only
one
carcinogenicity
study
was
performed
in
which
the
animals
were
exposed
to
styrene
via
inhalation.
In
this
study,
50
female
and
50
male
CD­
1
mice
per
group
were
exposed
to
0,
20,
40,
80
or
160
ppm
styrene
for
6
hours/
day,
5
days/
week
for
98
weeks
(
females)
or
104
weeks
(
males).
An
increased
incidence
for
lung
tumors
was
observed
in
male
and
female
mice.
The
incidence
of
bronchioalveolar
adenomas
was
significantly
increased
in
males
at
all
except
the
lowest
concentration
of
styrene,
and
in
females
at
20,
40,
and
160
ppm.
In
males,
the
incidence
of
bronchio­
alveolar
carcinomas
in
the
styrene­
treated
group
was
not
significantly
increased
compared
to
the
control.
In
females
exposed
to
160
ppm,
the
incidence
of
bronchio­
alveolar
carcinomas
was
higher
than
in
controls.
In
interim
sacrifices
after
12
and
months,
respectively,
did
not
reveal
lung
tumors
in
male
or
female
mice.
Since
the
lung
tumors
observed
after
2
years
in
styrene­
exposed
and
in
control
mice
showed
no
difference
in
intensity
of
immunostaining,
tumor
location
and
type
of
tumor,
the
authors
concluded
that
styrene
increased
the
number
of
tumors
seen
spontaneously
in
this
strain
of
mice
(
Cruzan
et
al.
2001a).

Studies
with
non­
inhalation
exposure
In
three
studies,
mice
were
exposed
orally
by
gavage
to
styrene
(
NCI
1979b;
Ponomarkov
and
Tomatis
1978)
or
to
a
mixture
of
70
%
styrene
and
30
%
ß­
nitrostyrene
(
NCI
1979a).
It
must
be
noted
that
none
of
these
studies
is
fully
acceptable
under
current
standards
(
number
of
animals
too
low,
exposure
to
mixture,
or
only
weekly
dosing).

In
the
NCI
study
with
styrene
(
NCI
1979b),
50
female
and
50
male
B6C3F1
mice
per
styrene
dose
group
(
20
females,
20
males
for
control
receiving
vehicle
only)
received
150
or
300
mg/
kg
b.
w.
styrene
in
corn
oil
for
5
days/
week
for
78
weeks
followed
by
a
27­
week
postexposure
observation
period.
No
treatment­
induced
effect
on
the
incidence
of
tumors
was
seen
in
female
mice.
In
males,
an
increase
in
the
combined
incidence
of
lung
adenomas
and
carcinomas
was
observed.
The
incidence
in
the
low­
dose
group
(
13.6
%)
was
clearly
higher
than
in
the
corresponding
control
(
0
%)
but
about
as
high
as
in
historical
controls
(
12
%,
range
0
 
20
%).
In
the
high­
dose
group,
the
incidence
(
20.9
%)
exceeded
that
observed
in
historical
controls.
In
the
NCI
study
using
a
mixture
of
styrene
and
ß­
nitrostyrene
(
NCI
1979a),
no
increase
in
the
incidence
of
any
tumor
was
observed.

In
the
study
of
Ponomarkov
and
Tomatis
(
1978),
29
pregnant
O20
mice
were
treated
with
1350
mg/
kg
b.
w.
in
olive
oil
on
day
17
of
gestation.
Offsprings
(
39
females,
45
males)
received
1350
mg/
kg
b.
w.
in
olive
oil
once
a
week
for
16
weeks
when
exposure
was
ended
due
to
high
mortality
with
hepatic
necrosis,
lung
congestion,
and
spleen
hypoplasia
(
20
%
of
females
and
50
%
of
males
had
died).
Controls
(
22
females,
20
males)
received
vehicle
only.
Animals
were
sacrificed
after
120
weeks.
The
combined
incidence
of
lung
adenomas
and
carcinomas
was
significantly
higher
in
the
group
of
styrenetreated
animals.
No
treatment­
related
effects
were
described
with
respect
to
other
tumors.
It
must
be
noted
that
the
maximum
tolerated
dose
had
been
exceeded.

Ponomarkov
and
Tomatis
(
1978)
also
exposed
15
pregnant
C57
mice
and
their
offspring
(
27
females,
27
males)
to
styrene
similarly
as
described
above
but
to
a
lower
dose
of
only
300
mg/
kg
b.
w.
There
were
no
effects
of
styrene
on
survival,
growth
or
the
incidence
of
any
tumor
in
this
experiment.
Styrene
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In
a
further
study
with
i.
p.
administration,
groups
of
25
female
A/
J
mice
received
a
total
amount
of
200
µ
mol
styrene
(
20.8
mg)
in
olive
oil
3
times
a
week
for
a
total
of
20
injections
(
Brunnemann
et
al.
1992),
25
control
animals
received
vehicle
only.
20
weeks
after
the
last
dose,
three
treated
animals
and
one
control
animal
had
lung
adenoma,
the
difference
was
not
statistically
significant.
No
lung
adenocarcinomas
were
found
in
any
animal.
It
must
be
noted
that
the
total
dose
applied
was
very
low.

Taking
together,
these
studies
provide
evidence
of
an
increase
of
lung
tumors
in
styrene­
treated
mice.

TABLE
6:
SUMMARY
OF
RESULTS
ON
STUDIES
OF
CANCER
IN
MICE
TREATED
WITH
STYRENE
*

Exposure
Strain
Route
Concentration
or
dose
Duration
Tumor
incidence
statistically
elevated,
type
of
tumor
Reference
CD­
1
Inhalation
20,
40,
80,
160
ppm
6
hours/
day,
5
days/
week
f:
98
week,
m:
104
weeks
Yes,
for
lung
tumors
Cruzan
et
al.
2001a
O20
Gavage
1350
mg/
kg
b.
w.
once
a
week
a
Yes,
for
lung
tumors
Ponomarkov
and
Tomatis
1978
C57
Gavage
300
mg/
kg
b.
w.
once
a
week
b
No
Ponomarkov
and
Tomatis
1978
B6C3F1
Gavage
150,
300
mg/
kg
b.
w.
5
days/
week,
78
weeks
Yes,
for
lung
tumors
NCI
1979b
B6C3F1
Gavage
200,
400
mg/
kg
b.
w.
3
days/
week,
78
weeks
c
No
NCI
1979a
A/
J
I.
p.
total:
200
µ
mol
(
20.8
mg)
3
days/
week,
20
injections
No
Brunnemann
et
al.
1992
*
Table
from
Cohen
et
al.
(
2002),
modified.
a:
Dams
were
administered
1350
mg/
kg
b.
w.
styrene
on
day
17
of
gestation,
offspring
received
1350
mg/
kg
b.
w.
after
weaning
once
a
week
for
lifetime.
b:
Dams
were
administered
300
mg/
kg
b.
w.
styrene
on
day
17
of
gestation,
offspring
received
300
mg/
kg
b.
w.
after
weaning
once
a
week
for
lifetime.
c:
Mice
were
given
a
mixture
of
70
%
styrene
wih
30
%
ß­
nitrostyrene.

3.6
Summary
Lethality
data
were
available
for
rats,
mice,
and
guinea
pigs.
Mice
were
much
more
sensitive
than
the
other
species
as
death
in
this
but
not
in
the
other
species
was
observed
in
a
number
of
studies
with
single
or
short­
term
repeated
6­
hour
exposures
to
250
and
500
ppm
(
Cruzan
et
al.
1997b;
Mahler
et
al.
1999;
Morgan
et
al.
1993c;
Morgan
et
al.
1993a;
Sumner
et
al.
1997).
In
contrast,
no
death
occurred
in
rats
upon
subchronic
daily
6­
hour
exposures
to
1500
ppm
(
Cruzan
et
al.
1997b).
Guinea
pigs
could
be
more
sensitive
than
rats
as
indicated
by
the
lethality
data
provided
by
Stewart
et
al.
(
1942),
but
the
data
base
is
too
limited
to
allow
firm
conclusions.
Limited
data
for
monkeys
(
4
animals,
species
not
reported;
Stewart
et
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38
al.
1942)
that
were
exposed
in
a
subchronic
study
at
1300
ppm
of
styrene
for
7­
8
hours/
day
do
not
provide
any
evidence
that
monkeys
may
be
more
sensitive
to
styrene
than
rats.

In
studies
with
rats,
the
reported
lethality
data
(
LC0;
LC50;
LC100)
show
considerable
differences
between
individual
studies:

10,000
ppm
1
hour
LC0
(
Spencer
et
al.
1942)
5000
ppm
1
hour
LC0
(
Niklasson
et
al.
1993)
5000
ppm
2
hours
LC0
(
Spencer
et
al.
1942)
10,000
ppm
3
hours
LC100
(
Spencer
et
al.
1942)
2761
ppm
4
hours
LC50
(
Shugaev
1969)
2700
ppm
4
hours
LC50
(
Jaeger
et
al.
1974;
abstract
only)
6410
ppm
4
hours
LC50
(
BASF
1979b)
7769
ppm
4
hours
LC0
(
Lundberg
et
al.
1986)
1500
ppm
6
hours
LC0
(
Cruzan
et
al.
1997;
repeated
exposure)
4618
ppm
6
hours
LC50
(
Bonnet
et
al.
1982)
2500
ppm
8
hours
LC0
(
Spencer
et
al.
1942)
7769
ppm
8
hours
"
LC40"
(
Lundberg
et
al.
1986)
5000
ppm
8
hours
LC100
(
Spencer
et
al.
1942)

Most
notable,
the
4­
hour
LC50
reported
in
two
studies
(
Jaeger
et
al.
1974;
Shugaev,
1969)
was
lower
than
the
LC50
in
a
third
study
(
BASF
1979b)
and
only
1/
3
of
the
4­
hour
LC0
in
another
study
(
Lundberg
et
al.
1986).
Also,
it
must
be
noted
that
these
two
"
low"
4­
hour
LC50
were
even
lower
than
the
6­
hour
LC50
in
another
study
(
Bonnet
et
al.
1982b)
and
similar
to
an
8­
hour
LC0
in
a
further
study
(
Spencer
et
al.
1942).
Furthermore,
the
4­
hour
LC50
of
BASF
(
1979b)
and
the
6­
hour
LC50
are
lower
than
the
8­
hour
concentration
which
caused
death
in
4/
10
animals
("
LC40")
(
Lundberg
et
al.
1986).

Experimental
differences
between
the
studies
are
likely
to
have
affected
the
outcomes
of
the
studies.
In
the
study
of
BASF
(
1979b),
animals
were
observed
for
14
days
after
the
exposure,
and
delayed
deaths
that
were
observed
up
to
3
days
after
exposure
were
taken
into
account.
In
contrast,
Lundberg
et
al.
(
1986)
counted
the
number
of
deaths
only
24
hours
after
start
of
the
inhalation
exposure
but
not
at
later
time
points.
Therefore,
delayed
deaths
will
have
been
missed
in
this
study.
Niklasson
et
al.
(
1993)
obviously
observed
no
death
during
the
neurological
studies
they
performed
in
rats,
but
it
cannot
be
deduced
from
their
data
whether
the
rats
exposed
to
the
highest
concentration
were
observed
for
one
week
after
exposure
or
not.

The
data
of
Jaeger
et
al.
(
1974)
only
were
published
in
an
abstract
lacking
any
experimental
details.
Shugaev
(
1969)
also
did
not
report
important
data,
especially,
the
number
of
animals
and
of
dose
groups
used
were
not
given.
In
addition
to
data
for
rats,
Shugaev
(
1969)
also
reported
a
2­
hour
LC50
of
4914
ppm
for
an
unspecified
strain
of
mice.
Interestingly,
this
value
is
much
higher
than
the
LC50
for
rats
although
it
is
clear
from
a
vast
number
of
studies
that
mice
are
more
susceptible
to
styrene
than
rats.
Furthermore,
whereas
the
LC50
reported
by
Shugaev
(
1969)
for
rats
is
much
lower
than
the
LC50
determined
in
other
studies,
the
opposite
is
true
fot
the
LC50
for
mice
in
Shugaev
(
1969);
this
value
is
much
higher
than
others
reported
in
other
studies,
even
when
the
different
exposure
times
are
taken
into
account
(
BASF
1979a;
Bonnet
et
al.
1979b;
Izmerov
et
al.
1982).
Although
it
cannot
be
ruled
out
that
differences
in
the
susceptibility
of
different
strains
of
mice
to
styrene
could
play
some
role,
it
is
tempting
to
speculate
that
the
LC50
for
rats
and
mice
could
have
been
erroneously
mixed
up
with
each
other
in
the
publication
of
Shugaev
(
1969).
Styrene
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39
In
the
study
of
Spencer
et
al.
(
1942),
the
concentration
of
10,000
ppm
may
be
doubted
in
view
of
the
observation
of
Lundberg
et
al.
(
1986)
that
7769
ppm
was
the
highest
attainable
(
analytically
confirmed)
vapor
concentration
of
styrene.
Therefore,
it
seems
possible
that
in
the
study
of
Spencer
et
al.
(
1942)
some
condensation
of
styrene
vapor
at
the
highest
concentration
used
had
occurred
(
leading
to
a
lower
vapor
concentration
but
possibly
to
additional
dermal
exposure).

The
studies
of
BASF
(
1979b)
and
Bonnet
et
al.
(
1982a)
both
reported
the
experimental
conditions
in
detail
(
especially,
number
of
animals
and
dose
groups,
analytically
determined
vapor
concentrations,
and
consideration
of
delayed
deaths
during
post­
exposure
period).
These
studies
thus
provide
the
most
reliable
and
relevant
acute
lethality
data
for
rats.

Following
i.
p.
treatment
of
rats
with
styrene,
no
differences
in
LD50
and
the
corresponding
confidence
limits
were
observed
when
deaths
were
counted
24
days
and
14
days
after
the
injection
(
Lundberg
et
al.
1986).
This
indicates
that
the
delayed
deaths
observed
after
inhalation
exposure
are
not
due
to
a
systemic
effect
but
probably
are
related
to
the
local
toxic
effects
that
are
observed
in
the
lung
of
animals
dying
some
days
after
styrene
exposure.

Very
limited
data
from
one
study
are
available
for
styrene
toxicity
in
monkeys
(
species
not
reported)
(
Spencer
et
al.
1942).
In
this
study,
none
of
4
animals
died
during
subchronic
exposure
to
1300
ppm
styrene,
7
 
8
hours/
day,
5
days/
week.
It
was
further
reported
that
there
were
no
signs
of
irritation
or
intoxication
and
no
pathological
findings
in
inner
organs
or
in
hematology
compared
to
3
control
animals.

At
non­
lethal
concentrations,
rats
showed
CNS­
depression.
Animals
were
in
state
of
deep
narcosis
after
1
hour
of
exposure
to
the
4­
hour
LC50
(
reported
to
be
2761
ppm,
but
see
discussion
above)
(
Shugaev
1969)
and
lost
consciousness
at
2000
ppm
after
5
hours
(
Withey
and
Collins
1979).
Reduced
attention
was
described
to
occur
at
6­
hours
of
exposure
to
1500
ppm
(
Jarry
et
al.
2002),
and
an
inability
to
supress
nystagmus
in
an
optokinetic
test
were
seen
at
1730
ppm
after
about
30
minutes
of
exposure
(
Niklasson
et
al.
1993).
Animals
were
mostly
recumbent
at
12
hours
of
exposure
to
600
ppm
(
Mäkitie
et
al.
2003),
this
may
also
indicate
CNS­
depression.
In
mice,
signs
of
CNS­
depression
that
occurred
during
a
4­
hour
exposure
included
staigered
gait
at
1420
ppm
and
apathy
and
finally
narcosis
at
higher
concentrations
(
2983
and
3766
ppm)
(
BASF
1979a).

In
rats,
immediate
sensory
irritation
occurred
at
1300
ppm
(
Spencer
et
al.
1942).
Cruzan
et
al.
(
1997b,
1998)
observed
a
concentration­
dependent
increase
of
irritation
reaching
from
closed
eyes
at
200
ppm
to
salivation
and
rubbing
of
paws
and
chin
at
higher
concentrations
(
500,
100,
1500
ppm).
Signs
of
sensory
irritation
were
also
observed
at
500
ppm
during
initial
exposure
in
one
study
(
Jarry
et
al.
2002),
but
in
another
study,
no
clear
signs
of
eye,
skin
or
mucous
membrane
irritation
could
be
observed
at
600
ppm
(
Mäkitie
et
al.
2003).
In
mice,
RD50
for
sensory
irritation
of
156
ppm
(
3
minutes),
586
ppm
(
5
minutes)
and
980
ppm
(
10
minutes)
were
reported
(
Alarie
1973;
de
Ceaurriz
et
al.
1981;
Bos
et
al.
1992).

In
rats,
pulmonary
lesions
at
acute
exposure
only
were
observed
at
concentrations
that
also
caused
severe
and
mostly
lethal
CNS
effects.
Mice
were
more
sensitive
to
styrene
than
rats.
At
250
ppm
and
500
ppm,
upper
respiratory
tract
and
lung
toxicity,
liver
lesions
and
sometimes
death
were
observed
following
one
or
few
exposures,
and
differences
in
sensitivity
between
strains
were
observed;
B6C3F1
were
most
sensitive
(
Morgan
et
al.
1993a,
c;
Mahler
et
al.
1999;
Cruzan
et
al.
1997;
Sumner
et
al.
1997).

Ototoxicity
of
styrene
was
observed
in
rats
after
repeated
exposure.
Exposure
for
6
hours/
day,
5
days/
week,
for
4
weeks
to
850
ppm
and
higher
concentrations
caused
a
permanent
increase
in
auditory
Styrene
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40
threshold,
at
500
ppm,
no
effect
was
observed
(
Loquet
et
al.
1999).
In
another
study,
no
effect
was
seen
immediately
after
exposure
to
1000
ppm,
6
hours/
day,
for
5
days,
but
tests
indicated
a
disruption
of
cochlear
auditory
function
2
and
4
weeks
after
the
end
of
exposure.
In
the
same
study,
no
effects
were
detected
in
similarily
exposed
guinea
pigs
(
Lataye
et
al.
2003).
Histological
lesions
of
the
cochlea
and
worsening
of
the
electrophysiological
results
after
the
end
of
exposure
were
also
described
in
another
publication
of
the
same
group
after
exposure
of
rats
to
1000
ppm,
6
hours/
day,
5
days/
week,
for
up
to
4
weeks
(
Campo
et
al.
2001).
No
hearing
impairment
was
detected
in
rats
exposed
to
100
or
300
ppm
styrene
for
12
hours/
day,
5
days/
week,
for
4
weeks;
at
600
ppm,
a
hearing
loss
of
~
3
dB
was
observed
only
at
the
highest
test
frequeny
of
8
kHz,
and
cytocochleograms
showed
a
substantial
loss
of
the
outer
hair
cells
of
the
cochlea
from
these
animals
(
Mäkitie
et
al.
2003).

No
studies
were
available
concerning
effects
of
a
single
inhalation
exposure
to
styrene
on
reproductive
or
developmental
toxicity.
A
single
oral
administration
of
300
mg/
kg
b.
w.
of
styrene
on
day
11
of
gestation
caused
maternal
toxicity
in
rats,
but
had
no
developmental
or
fetotoxic
effects
(
Daston
et
al.
1991).
In
another
study
with
rats
and
mice
that
were
treated
orally
with
styrene
on
gestation
day
17,
1350
mg/
kg
b.
w.
styrene
had
no
significant
effect
on
preweaning
mortality,
litter
size
at
birth,
or
body
weight
development
in
BD
IV
rats.
In
O20
mice,
survival
prior
to
weaning
was
reduced
after
1350
mg/
kg
b.
w.,
no
effect
was
seen
in
C57Bl
mice
given
300
mg/
kg
b.
w.
(
Ponomarkov
and
Tomatis
1978).

Following
repeated
6­
hour
exposure
of
rats
to
300
ppm
during
gestation
day
6
 
20,
an
increased
neonatal
death
rate
was
observed
compared
to
pair­
fed
controls
(
that
were
included
to
control
for
a
styreneinduced
reduction
of
food
intake;
maternal
weight
gain
was
not
affected).
Postnatal
development
(
incisor
eruption,
eye
opening,
air
righting
reflex)
also
was
delayed.
No
effects
were
seen
at
50
ppm
(
Katakura
et
al.
2001).
These
findings
supported
those
from
earlier
studies
in
which
similar
effects
were
described
but
no
pair­
fed
controls
were
used
(
Kishi
et
al.
1992;
1995).
In
a
study
with
hamsters,
the
number
of
dead
or
resorbed
fetuses
was
increased
in
the
group
exposed
to
1000
ppm
6
hours/
day
from
gestation
day
6
­
18,
but
not
at
750
ppm
or
lower
concentrations
(
Kankaanpää
et
al.
1980).
In
other
studies
with
repeated
oral
or
inhalation
exposure
of
rats,
mice,
and
rabbits,
no
significant
developmental
effects
were
seen
(
Murray
et
al.
1978;
Srivastava
et
al.
1990;
Chernoff
et
al.
1990;
Beliles
et
al.
1985;
Kankaanpää
et
al.
1980).

Styrene
is
genotoxic
in
vitro,
provided
there
is
sufficient
activation
to
styrene
oxide
(
SO),
and
in
vivo.
Data
from
laboratory
animals
indicate
that
styrene
exposure
may
lead
to
the
formation
of
DNAadducts
sister
chromatid
exchange,
and
chromosomal
aberrations.

With
respect
to
carcinogenicity,
no
clear
effect
was
observed
in
rats.
In
mice,
the
studies
provide
evidence
for
an
increase
of
lung
tumors.
IARC
recently
has
re­
evaluated
the
data
on
carcinogenicity
of
styrene
and
concluded
that
there
is
"
limited
evidence"
in
experimental
animals
for
the
carcinogenicity
of
styrene.
In
the
overall
evaluation,
it
was
concluded
that
styrene
is
"
possibly
carcinogenic
to
humans
(
Group
2B)"
(
IARC
2002).
Styrene
is
being
reassessed
under
the
IRIS
Program
of
the
US­
EPA,
no
quantitative
carcinogenicity
assessment
for
lifetime
exposure
is
currently
proposed
(
US
EPA
1998).
US­
EPA
´
s
Office
of
Research
and
Development
has
updated
previous
assessments
on
the
carcinogenic
potential
of
styrene
and
concluded
that
styrene
is
appropriately
classified
as
a
Group
C,
possible
human
carcinogen
(
US
EPA
2003).
Styrene
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41
4
SPECIAL
CONSIDERATIONS
4.1
Toxicokinetics
The
toxicokinetics
of
styrene
both
in
humans
and
laboratory
animals
has
been
reviewed
(
e.
g.
ATSDR
1992;
Bond
1989;
Cohen
et
al.
2002;
Engelhardt
et
al.
2003;
Government
Canada
1993;
Linhart
2001;
Sherrington
and
Routledge
2001;
Sumner
et
al.
2001).

Uptake
and
distribution
In
studies
with
human
volunteers
and
occupationally
exposed
workers,
retention
of
styrene
was
about
70
%
of
the
inhaled
dose.
E.
g.,
in
two
studies
on
male
healthy
volunteers
who
were
exposed
to
300
mg/
m
³
(
70
ppm)
of
styrene
during
light
exercise,
the
average
uptake
of
styrene
was
68
%
of
the
amount
supplied;
the
percentage
of
uptake
was
nearly
constant
during
the
whole
exposure
period
(
0
 
30
minutes:
71.0
%;
90
 
120
minutes:
66.7
%
(
Wigaeus
et
al.
1983;
Wigaeus
et
al.
1984).

Experimental
and
simulation
studies
suggest
a
washin­
washout
effect
for
styrene
in
the
upper
respiratory
airways
of
humans
(
Jonsson
and
Johanson
2002).
In
rats
and
mice,
styrene
has
been
shown
to
be
taken
up
and
metabolized
in
surgically
isolated
upper
respiratory
tract
preparations;
uptake
amounted
to
about
10
%
of
styrene
at
200
ppm
(
Morris
2000).

For
styrene,
a
high
in
vitro
blood:
air
partition
coefficient
at
equilibrium
of
32
was
reported
by
Astrand
(
1975).
Even
higher
coefficients
of
40
for
rats
and
mice
and
52
for
humans
were
reported
by
Ramsey
and
Andersen
(
1984).
In
controlled
human
studies
in
vivo,
the
blood:
air
coefficient
was
found
to
depend
on
the
work
load
during
exercise:
At
50
and
150
ppm
styrene,
the
coefficient
of
the
concentration
of
styrene
in
alveloar
air:
blood
was
15
at
rest
and
increased
to
50,
85,
and
105
at
work
loads
of
50
W,
100
W,
and
150
W
during
subsequent
30­
minute
exposure
periods,
respectively
(
Astrand
1975).

Concentrations
of
styrene
determined
in
blood
of
humans
and
rats
and
in
rat
brain
are
summarized
in
TABLE
7.
In
humans
exposed
to
69
ppm
for
two
hours
during
light
physical
exercise
(
50
W),
the
concentration
of
styrene
in
arterial
blood
rose
steeply
during
the
first
30
minutes
and
reached
a
plateau
at
about
60
minutes
(
FIGURE
3)
(
Wigaeus
et
al.
1984).
Controlled
studies
further
show
that
the
concentration
of
styrene
in
blood
depends
on
the
intensity
of
physical
work
load.
When
volunteers
were
exposed
at
154
ppm
styrene
for
consecutive
30­
min
periods
with
increasing
intensity
of
physical
exercise
(
0,
light
exercise:
50
W,
100
W,
heavy
exercise:
150
W),
the
arterial
blood
concentration
increased
with
increasing
exercise
activity
and
was
approximately
3fold
higher
at
50
W,
5fold
higher
at
100
W,
and
10fold
higher
at
150
W
than
at
rest
(
Astrand
1975).
However,
care
must
be
taken
when
interpreting
these
observations
since
a
30­
minute
exposure
period
(
at
154
ppm)
is
not
sufficient
to
reach
a
plateau
level
of
styrene
in
blood.
Thus,
the
experimental
condition
in
the
study
of
Astrand
(
1975)
leads
to
an
overestimation
of
the
effect
of
work
load.

At
higher
inhalation
concentrations,
no
constant
styrene
concentration
in
blood
is
reached
(
data
for
humans
see
FIGURE
4,
Löf
and
Johanson
1993).
In
rats
exposed
to
520,
1274,
and
2850
ppm
styrene
by
inhalation
for
up
to
5
hours,
the
level
of
styrene
in
jugular
venous
blood
rose
continuously.
After
about
90
minutes,
a
nearly
linear
increase
was
observed
at
the
three
higher
concentrations
and
no
equilibrium
was
reached
during
exposure.
At
45
ppm,
no
marked
increase
with
continuing
exposure
was
observed
(
FIGURE
5,
Withey
and
Collins
1979).
Styrene
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42
FIGURE
3:
STYRENE
CONCENTRATION
IN
ARTERIAL
BLOOD
OF
HUMANS
DURING
AND
AFTER
A
2­
HOUR
EXPOSURE
TO
69
PPM
STYRENE
IN
AIR
(
Human
volunteers
(
n
=
5)
were
exposed
to
69
ppm
styrene
(
open
symbols)
or
a
mixture
of
70
ppm
styrene
and
520
ppm
acetone
(
closed
symbols)
during
a
work
load
of
50
W
(
light
exercise)
(
Graph
from
Wigaeus
et
al.
1984).
1
µ
M
=
104
µ
g/
l.).

FIGURE
4:
OBSERVED
(
CIRCLES)
AND
SIMULATED
CONCENTRATIONS
OF
STYRENE
IN
ARTERIALIZED
CAPILLARY
BLOOD
FROM
TWO
HUMAN
VOLUNTEERS
(
2
hours
of
exposure
during
light
(
50
W)
exercise.
Continuous
line:
PBPK
model
simulation
with
a
linear
model
(
nonsaturable
metabolism
in
liver);
broken
lines:
same
model
with
saturable
metabolism.
The
study
did
not
indicate
which
of
the
values
were
determined
in
the
female
and
the
male
volunteer.
Graph
from
Löf
and
Johanson
(
1993)).
Styrene
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43
FIGURE
5:
STYRENE
CONCENTRATION
IN
BLOOD
OF
RATS
DURING
A
5­
HOUR
EXPOSURE
TO
DIFFERENT
CONCENTRATIONS
OF
STYRENE
IN
AIR
(
Animals
were
exposed
to
the
styrene
vapor
concentrations
indicated
and
styrene
was
determined
in
blood
from
jugular
vein
at
different
time
points
by
means
of
an
indwelling
cannula
fixed
prior
to
exposure.
Graph
from
Withey
and
Collins
1979.)

Styrene
is
widely
distributed
throughout
the
body.
From
its
high
lipophilicity,
the
highest
concentrations
may
be
expected
in
lipid­
rich
tissues.
However,
it
must
be
taken
into
account
that
the
distribution
of
styrene
is
affected
by
its
rapid
metabolic
clearance
(
see
below).
Thus,
at
low
exposure
concentrations
(
54
ppm),
the
concentration
of
styrene
in
rat
brain
was
lower
than
in
blood.
At
higher
concentrations
( 
470
ppm)
where
metabolic
clearance
approaches
saturation
(
see
below),
the
concentration
in
rat
brain
was
1.17
 
1.89
fold
higher
than
in
blood.
Similar
effects
were
observed
in
heart,
lung,
liver,
and
spleen,
but
not
in
kidney
where
the
styrene
concentration
was
higher
than
in
blood
at
all
concentrations.
Concentrations
at
least
10fold
higher
than
in
every
other
tissue
were
observed
in
perirenal
fat
(
Withey
and
Collins
1979).
In
humans,
the
ratio
between
the
styrene
concentration
in
subcutaneous
adipose
tissue
(
from
the
gluteal
region)
and
arterial
blood
reached
3
at
the
end
of
a
2­
hour
exposure
to
70
ppm
styrene.
This
value
is
far
below
the
value
in
equilibrium
that
can
be
calculated
from
the
oil:
air
(
about
5.5)
and
blood:
air
partition
(
52)
coefficient
of
styrene
indicating
that
styrene
in
adipose
tissue
does
not
reach
equilibrium
under
the
condition
of
the
study.
Taking
into
account
the
long
half­
life
of
styrene
in
subcutaneous
adipose
tissue
(
2.2
 
5.2
days),
the
authors
further
estimated
that
several
days
of
continuous
exposure
would
be
necessary
to
reach
90
%
of
steady
state
(
Wigaeus
et
al.
1983).
Styrene
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44
TABLE
7:
EXPOSURE
CONCENTRATIONS
AND
BLOOD
LEVEL
OF
STYRENE
IN
HUMANS
AND
RATS
Exposure
time
Conc.
in
air
(
ppm)
Concentration
in
blood
(
mg/
L)
or
brain(
mg/
kg)
Remarks
Reference
Humans
50
min
87­
139
2.7
Exposure
at
light
physical
exercise
(
50
W)
Ödkvist
et
al.
1982
55
min
1
h
55
min
3
h
30
min
51.4
116.7
116.7
99
0.2
 
0.7
(
vb)
1.7
(
vb)
2.7
(
vb)
0.9
 
1.4
(
vb)
Exposure
at
rest
Stewart
et
al.
1968
30
min
1
h
2
h
69
1.8
(
ab)
2.1
2.2
Exposure
with
light
physical
exercise
(
50
W)
Wigaeus
et
al.
1983;
1984
30
min
154
~
2
(
ab)
~
6
~
9
~
16
Exposure
at
rest
50
W
exercise
100
W
exercise
150
W
exercise;
all
values
estimated
from
figure
Astrand
1975
2
h
69
1.6
(
ab)
Exposure
with
light
physical
exercise
(
50
W);
study
with
occupationally
exposed
workers
Löf
et
al.
1984
6
h
80
0.92
(
vb)
Exposure
at
rest
Ramsey
et
al.
1980
2
h
26
77
201
386
~
0.7/
0.7
(
acb)
~
2/
3.1
~
6.2/
8.3
~
15/
21
Values
for
2
volunteers
exposed
with
light
physical
exercise
(
50
W);
values
estimated
from
figure
Löf
and
Johanson
1993
Rats
2
h
520
1274
2850
~
24
~
73
~
100
Values
estimated
from
graph
Withey
and
Collins
1979
5
h
45
520
1274
2800
<
2
(
vb)
~
43
~
149
~
198
Values
estimated
from
graph
Withey
and
Collins
1979
5
h
54
470
1018
1522
2144
2240
0.65
(
vb)/
0.2
(
brain)
2
31.8
/
43
65.3
/
76
72.8
/
105
173.7
/
302
135.5
/
256
Withey
and
Collins
1979
>
75
(
ab)
i.
v.
exposure;
effects
on
vestibular
system
as
indicated
by
changes
in
nystagmus
Tham
et
al.
1982
6
h
80
1.0
(
wb)
Ramsey
and
Styrene
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TABLE
7:
EXPOSURE
CONCENTRATIONS
AND
BLOOD
LEVEL
OF
STYRENE
IN
HUMANS
AND
RATS
Exposure
time
Conc.
in
air
(
ppm)
Concentration
in
blood
(
mg/
L)
or
brain(
mg/
kg)
Remarks
Reference
1200
63
Andersen
1984
6
h
50
200
500
1000
0.43/
0.29
(
m/
f)
2.8/
1.95
12.5/
9.5
33.2/
29.7
Values
determined
in
week
95
of
chronic
study
Cruzan
et
al.
1998
4
h
1
h
2760
*

2760
*
250
(
brain)

218
(
brain)
222
(
brain)
177
(
brain)
86
(
brain)
0
­
max.
44
(
brain)
Exposure
to
LC50
End
of
exposure,
animal
in
deep
narcosis
15
min
after
end
of
exposure
30
min
after
end
of
exposure
60
min
after
end
of
exposure
90
min
after
end
of
exposure
Shugaev
1969
6
h
+
4
h1
1750
37.5
(
ab)
68
(
brain)
At
end
of
exposure
Campo
et
al.
1999
ab:
arterial
blood;
acb:
arterialized
capillary
blood;
vb:
venous
blood;
wb:
whole
blood;
m/
f:
values
for
males/
females;
1:
6
hours
on
1st
and
4
hours
on
2nd
day;
2:
approximate
concentration,
calculated
from
values
presented
as
brain
concentration
relative
to
blood
in
original
reference.
*
see
section
3.6
for
discussion
of
validity
of
data
from
this
study.

Metabolism
The
metabolism
of
styrene
was
compared
in
male
Sprague­
Dawley
rats
and
B6C3F1
mice.
In
both
species,
the
rate
of
metabolism
of
inhaled
styrene
was
found
to
increase
linerarily
with
concentration
up
to
about
300
ppm.
In
this
concentration
range,
delivery
of
styrene
to
the
site
of
metabolism
but
not
metabolic
capacity
was
the
rate­
limiting
step
for
metabolism.
Above
300
ppm,
the
rate
of
metabolism
at
steady
state
became
more
and
more
limited
by
metabolic
parameters.
Metabolism
approached
nearly
saturation
at
about
700
ppm
in
rats
and
800
ppm
in
mice;
exposure
concentrations
at
half
maximum
rates
of
metabolism
were
190
ppm
in
rats
and
270
ppm
in
mice,
respectively.
Repeated
exposure
for
6
hours/
day
on
5
consecutive
days
to
150
or
500
ppm
caused
no
detectable
changes
in
the
rates
of
styrene
metabolism
(
Filser
et
al.
1993).
However,
evidence
for
an
induction
of
styrene
metabolism
in
male
rats
following
preexposure
to
styrene
was
observed
in
another
study
in
which
prior
exposure
to
styrene
(
1000
ppm,
6
hours/
day,
4
days)
increased
Vmax
about
twofold.
Significant
induction
of
styrene
metabolism
was
observed
in
24­
hr
continuous
exposure
to
400,
600,
or
1200
ppm.
Calculations
using
a
physiological
model
of
styrene
inhalation
kinetics
to
estimate
the
dynamics
of
the
induction
indicated
that
induction
at
1200
ppm
began
4.6
hr
after
the
start
of
exposure
and
reached
4.4
times
the
Vmax
of
naive
rats.
No
induction
occurred
in
48­
hr
exposure
to
200
ppm
(
Andersen
et
al.
1984).

In
humans,
evidence
from
controlled
studies
indicates
that
saturation
of
metabolic
capacity
to
clear
styrene
becomes
noticeable
at
concentrations
around
200
ppm.
In
one
study,
one
female
and
one
male
volunteer
were
exposed
to
analytically
confirmed
concentrations
of
26,
77,
201
and
386
ppm
styrene
vapor
for
2
hours
with
light
exercise
(
50
W).
During
the
2­
h
exposure,
the
concentration
of
styrene
in
blood
Styrene
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46
reached
a
plateau
at
the
lower
concentrations
in
both
individuals.
At
386
ppm,
the
arterial
styrene
concentration
only
approached
a
plateau
in
one
individual
but
continued
to
increase
steadily
in
the
other
(
FIGURE
4);
it
was
not
indicated
in
the
study
which
of
the
values
were
determined
in
the
male
and
in
the
female
volunteer).
This
non­
linear
relationship
between
the
level
of
exposure
to
styrene
and
the
concentration
of
styrene
in
arterial
blood
(
and
also
the
0
 
5
hours
cumulative
excretion
of
mandelic
acid,
see
below)
indicated
metabolic
saturation.
A
physiologically
based
pharmacokinetic
model
was
used
to
estimate
metabolic
parameters.
According
to
the
model,
transition
to
metabolic
saturation
is
seen
at
about
100
ppm
(
at
50
W
physical
activity)
and
at
about
200
ppm
at
rest
(
Löf
and
Johanson
1993).
Previous
studies
also
provided
evidence
that
styrene
metabolism
in
rats,
mice
and
humans
becomes
saturated
at
concentrations
exceeding
200
ppm.
At
lower
concentrations,
the
ratio
of
styrene
concentration
in
blood
to
inhaled
air
is
controlled
by
perfusion
limited
metabolism,
while
at
higher
concentrations,
the
ratio
is
controlled
by
the
blood:
air
coefficient
(
Ramsey
and
Andersen
1984).

An
overview
of
the
pathways
of
styrene
metabolism
is
presented
in
FIGURE
6.
The
major
metabolic
pathway
starts
with
the
formation
of
styrene­
7,8­
oxide
(
SO)
by
cytochrome
P450­
dependent
monoxygenases.
SO
is
either
conjugated
with
glutathione
(
GSH)
to
finally
produce
mercapturic
acids
or
it
is
hydrolyzed
by
epoxide
hydrolase
to
styrene
glycol
that
is
subsequently
oxidized
to
mandelic
and
phenylglyoxylic
acid.
Phenylacetic
acid
and
benzoic
acid
or
rather
hippuric
acid,
its
glycine
conjugation
product,
are
also
found
in
urine.

Different
CYP
isozymes
are
involved
in
the
oxidation
of
styrene
to
SO.
Based
on
in
vitro
studies,
CYP2B6
and
CYP2E1
seem
most
important
in
liver
and
CYP2F2
in
lung,
but
other
isozyms
also
seem
to
play
a
role.
In
mice
devoid
of
CYP2E1
activity
(
Cyp2e1­
null
mice),
the
amount
of
metabolites
derived
from
SO
was
higher
and
that
derived
from
phenylacetaldehyde
was
lower
as
compared
to
control
mice.
The
excretion
of
total
urinary
metabolites
was
higher
in
"
null
mice"
than
in
wild­
type
controls.
These
data
indicate
that
CYP2E1
may
not
be
a
major
isozyme
involved
in
the
metabolism
of
styrene
to
SO
in
mice
(
Sumner
et
al.
2001).
In
humans
with
individual
differences
in
xenobiotic
metabolism
capacity
determined
with
enzyme­
specific
substrates
for
CYP2E1,
CYP1A2,
and
CYP2D6,
no
correlation
was
found
between
the
blood
clearance
of
styrene
and
the
metabolic
capacity
as
measured
by
urinary
excretion
of
mandelic
and
phenylglyoxylic
acid.
Under
the
experimental
conditions
(
24
and
84
ppm
styrene,
1
hour
exposure,
light
exercise),
the
apparent
blood
clearance
of
styrene
(
1.4
l/
min)
was
similar
to
the
hepatic
blood
flow
(
IARC
2002).
These
data
further
support
the
assumption
that
styrene
metabolism
at
low
concentrations
is
limited
by
perfusion
and
not
by
the
capacity
of
the
metabolism.

Qualitatively,
styrene
metabolism
is
similar
in
humans
and
rodents
(
FIGURE
6),
and
in
both,
humans
and
animals,
more
than
90
%
of
styrene
taken
up
is
metabolized.
However,
there
are
quantitative
differences
between
rats
and
humans,
and,
more
pronounced,
humans
and
mice.
With
respect
to
the
metabolism
of
styrene
in
the
liver,
the
experimental
data
indicate
that
the
order
of
the
oxidation
rate
of
styrene
to
SO
is
mice
>
rats
>
humans,
while
the
order
for
microsomal
epoxide
hydrolase
activity
of
the
liver
is
humans
>
rats
>
mice
(
Mendrala
et
al.
1993).
However,
enzymatic
activities
in
tissues
other
than
in
liver
may
be
different
(
Vodicka
et
al.
2002).
In
humans,
conversion
of
SO
preceeds
predominantly
via
oxidation
to
styrene
glycol,
whereas
conjugation
with
GSH
and
formation
of
mercapturic
acid
is
important
in
mice
and,
to
a
much
lesser
extent,
in
rats.
Furthermore,
in
mice
up
to
30
%
of
styrene
metabolism
leads
to
the
formation
of
phenylaceturic
acid.
This
pathway
likely
involves
the
formation
of
phenylacetaldehyde
as
a
reactive
intermediate
that
is
able
to
react
with
proteins.
In
rats
and
humans,
this
pathway
is
of
minor
impotance
(
rats:
5
%;
humans:
less
than
5
%)
(
Sumner
et
al.
2001).
Styrene
NAC:
02/
2004
47
FIGURE
6:
PATHWAYS
FOR
THE
METABOLISM
OF
STYRENE
IN
HUMANS
AND
RODENTS
(
modified
from
IARC
2002;
main
pathways
are
illustrated
by
arrows
in
bold)

Nasal
metabolism
of
styrene
is
thought
to
be
related
to
olfactory
epithelium
toxicity
that
is
pronounced
in
mice
and
less
or
marginal
in
rats
(
Cruzan
et
al.
2002).
The
metabolism
of
styrene
in
nasal
epithelia
of
rats,
mice,
and
humans
was
studied
by
Green
et
al.
(
2001a).
Pretreatment
of
mice
with
5­
phenyl­
1­
pentyne,
an
inhibitor
of
CYP2F2
and
CYP2E1,
prevented
the
development
of
nasal
lesions
upon