Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
1
Final
draft
Chapter
V.
Health
Effects
in
Animals
A.
Short­
Term
Exposures
Cyanogen
chloride.
Toxicity
studies
on
cyanogen
chloride
are
summarized
in
Table
VIII­
1.
Very
few
studies
are
available
on
the
toxicity
of
cyanogen
chloride,
and
the
existing
studies
are
generally
old
and
incompletely
reported.
No
short­
term
studies
of
cyanogen
chloride
by
the
oral
or
dermal
route
were
located.
The
available
studies
(
Reed,
1920;
Haymaker,
1952;

Aldridge
and
Evans,
1946;
Flury
and
Zernik,
1931)
are
primarily
useful
for
hazard
identification,

rather
than
dose­
response
assessment,
because
they
were
conducted
with
small
numbers
of
animals,
and
typically
investigated
only
one
exposure
level.
However,
they
may
provide
some
useful
quantitative
comparisons
between
cyanogen
chloride
and
hydrogen
cyanide.

Aldridge
and
Evans
(
1946)
report
the
effects
of
acute
inhalation
exposures
of
various
species
to
cyanogen
chloride.
The
reported
air
concentrations
ranged
from
50
to
120
mg/
m3,
but
only
single
exposure
levels
were
tested,
so
the
studies
are
not
useful
for
exposure­
response
assessment.
However,
the
studies
do
provide
some
useful
hazard
identification
information.

Effects
of
acute,
high­
level
exposure
to
cyanogen
chloride
included
irritation
of
the
respiratory
passages,
lachrimation,
and
severe
blepharospasm
(
spasmodic
winking).
The
authors
noted
that
the
initial
symptoms
of
exposure
to
100
mg/
m3
decreased
after
the
first
minute
or
two,
indicating
some
degree
of
adaptation.
The
authors
reported
that
vomiting,
deep
respiration,
and
loss
of
consciousness
occurred
at
high
levels,
and
convulsions
may
occur
after
cessation
of
exposure.

Coughing
and
increased
ventilation
rate
were
considered
reflex
responses,
and
the
coughing
was
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
2
Final
draft
eliminated
by
cutting
the
vagus
nerve.
Concentrations
of
50
mg/
m3
were
reported
to
be
fatal
in
dogs,
yet
other
dogs
appeared
to
survive
exposures
to
120
mg/
m3.
Death
was
preceded
by
lung
edema,
and
respiration
failed
before
circulation
did.
Necropsy
revealed
inflammation
of
upper
respiratory
tract,
lung
edema,
and
dilated
right
ventricle.
Exposure
of
one
dog
for
3
hours
to
40­

50
mg/
m3,
followed
immediately
by
exposure
to
81­
105
mg/
m3
for
approximately
2.75
hours,

resulted
in
the
dog
being
unconscious
for
several
days.
After
the
animal
recovered,
it
was
blind,

and
had
an
altered
(
less
friendly)
personality.

Aldridge
and
Evans
(
1946)
exposed
anesthetized
cats
to
3000
mg/
m3
and
anesthetized
rabbits
to
2000
mg/
m3
cyanogen
chloride
by
inhalation
for
1­
2
minutes.
Arterial
pressure
demonstrated
a
transitory
rise,
followed
by
a
decrease.
The
heart
rate
ultimately
slowed,
after
a
brief
period
of
acceleration.
The
initial
reaction
of
the
animals
was
violent
with
rapid
coughing,

followed
by
deep,
sometimes
rapid
breathing,
which
became
reduced
in
depth
and
frequency,
with
intermittent
gasping
breaths.
Circulation
continued
to
function
for
some
period
after
respiration
failed.
If
the
animals
were
exposed
a
second
time,
the
amount
of
coughing
was
reduced.
The
authors
concluded
that
this
effect
was
"
probably
because
of
damage
to
sensory
surfaces."
A
second
exposure
also
resulted
in
a
less­
evident
increase
in
ventilation;
the
authors
concluded
that
this
was
due
to
damage
to
respiratory
center
or
various
chemoreceptors.
The
general
course
of
events
following
acute
inhalation
exposure
to
cyanogen
chloride
was
identified
as
stimulation
of
upper
respiratory
passages,
resulting
in
coughing.
This
was
followed
by
stimulation
of
chemoreceptors,
resulting
in
hyperpnea,
followed
by
paralysis
of
the
respiratory
center,
with
gasping
breathing.
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
3
Final
draft
Haymaker
et
al.
(
1952)
examined
the
neurological
effects
in
dogs
of
acute
exposure
to
both
cyanogen
chloride
and
cyanide
following
inhalation
and
intravenous
injection.
Eleven
adult
mongrel
dogs
(
sex
not
specified)
were
exposed
by
inhalation
to
concentrations
of
cyanogen
chloride
ranging
from
2
to
3.8
mg/
L
(
2000
to
3800
mg/
m3)
for
approximately
2
minutes
(
one
dog
was
exposed
for
49
minutes).
Three
of
the
animals
were
pretreated
with
amyl
nitrate
just
prior
to
exposure,
and
two
were
given
p­
aminopropiophenone
3
to
4
hours
before
exposure
to
cyanogen
chloride.
In
a
separate
experiment,
one
dog
was
administered
cyanogen
chloride
intravenously
at
a
dose
of
3
mg/
kg.
In
order
to
compare
the
toxicity
of
cyanogen
chloride
and
HCN,
six
adult
mongrel
dogs
were
exposed
by
inhalation
to
HCN
concentrations
ranging
from
0.2
to
0.7
mg/
L
(
200
to
700
mg/
m3)
for
approximately
2
minutes.
Converted
to
cyanide
equivalents,
the
dogs
were
exposed
to
850­
1600
mg
CN/
m3
as
cyanogen
chloride,
and
190­
680
mg
CN/
m3
as
hydrogen
cyanide.
Five
dogs
were
also
administered
sodium
cyanide
intravenously
at
doses
ranging
from
1.5
to
2.25
mg/
kg.
All
dogs
either
died
or
were
sacrificed.
The
brains
and
abdominal
and
thoracic
viscera
were
evaluated
histopathologically.
Survival
in
the
animals
exposed
by
inhalation
to
cyanogen
chloride
ranged
from
5
minutes
to
7
days;
5
animals
died
within
21
minutes
of
exposure.
In
contrast,
survival
in
the
animals
exposed
to
HCN
ranged
from
16
to
28
hours.

Clinical
signs
observed
in
animals
treated
with
cyanogen
chloride
include
coma,
apnea,
rigidity
and
weakness
in
limbs,
and
incoordination.
One
animal
receiving
cyanogen
chloride
by
inhalation
and
the
dog
receiving
cyanogen
chloride
intravenously
had
convulsive
seizures
during
the
period
of
administration.
In
contrast,
4
of
6
dogs
receiving
HCN
by
inhalation
had
convulsive
seizures.
The
authors
note
that
"
with
the
exception
of
severe
pulmonary
edema
in
a
few
of
the
dogs,
the
only
lesions
of
significance
were
in
the
CNS
(
central
nervous
system)."
However,
the
authors
do
not
indicate
whether
the
edema
was
observed
following
exposure
to
cyanogen
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
4
Final
draft
chloride,
HCN,
or
both.
Also,
the
authors
note
that
the
pathological
changes
in
the
CNS
were
essentially
the
same
following
exposure
to
both
cyanogen
chloride
and
HCN.
No
CNS
effects
were
observed
in
dogs
that
died
within
3
hours.
The
CNS
effects
in
the
remaining
animals
consisted
of
necrosis
of
the
cerebral
cortex,
the
caudate
nucleus,
putamen,
substantia
nigra,

globus
pallidus,
pulvinar
of
the
thalamus,
and
cerebellar
cortex.
Although
many
of
the
dogs
exposed
to
cyanogen
chloride
died
at
earlier
post­
exposure
timepoints
than
the
dogs
exposed
to
HCN,
the
higher
exposure
level
(
in
cyanide
equivalents)
in
the
former
group
and
the
lack
of
quantitative
effect
measures
precludes
a
quantitative
comparison
of
toxicity
of
these
two
compounds.
It
is
interesting
to
note,
however,
that
the
survival
time
of
the
dogs
exposed
to
HCN
was
rather
narrow
(
16­
28
hours),
while
that
for
the
dogs
exposed
to
cyanogen
chloride
ranged
from
5
minutes
to
7
days.
The
latter
range
could
have
been
due
to
a
higher
variability
in
that
group
of
dogs,
but
the
results
suggest
that
there
may
be
multiple
mechanisms
by
which
cyanogen
chloride
exerts
its
toxic
effects,
and
that
these
mechanisms
occur
at
different
rates.

Flury
and
Zernik
(
1931)
reported
the
effects
of
exposing
various
species
to
cyanogen
chloride
for
durations
ranging
from
a
few
breaths
to
6
hours.
Most
of
the
exposure
levels
were
fatal.
The
observed
effects
were
reported
to
be
similar
to
those
of
cyanide,
except
that
irritation
was
also
observed,
and
the
lower
concentrations
only
caused
irritation.
Pathology
analysis
showed
severe
irritation
of
the
bronchioles
and
respiratory
tubes,
and
bloody
lung
edema.

Reed
(
1920)
evaluated
the
short­
term
toxicity
of
cyanogen
chloride
vapor
in
animals.
Five
dogs
and
a
goat
(
sex
and
strain
not
specified)
were
exposed
to
sublethal
concentrations
(
concentration
not
reported)
of
vaporized
cyanogen
for
30
minutes
to
2
hours/
day
for
two
weeks.
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
5
Final
draft
No
mortality
was
observed
following
exposure.
The
dogs
lost
an
average
of
13%
of
their
body
weight;
the
goat
lost
17%
of
its
body
weight.
The
symptoms
observed
during
the
exposure
period
included
convulsions,
irritation,
excitement,
nausea,
vomiting,
urination,
defecation,

tearing,
and
salivation.
Subsequent
symptoms
included
muscular
tremors,
weakness,
listlessness,

diarrhea,
depression
of
reflexes,
cardiac
irregularities,
conjunctivitis,
and
rhinitis.
Necropsy
revealed
that
all
animals
developed
severe
pulmonary
congestion.
These
symptoms
were
similar
to
those
observed
in
dogs
administered
a
single
sublethal
injection
of
cyanogen
chloride,

suggesting
that
the
toxicity
of
cyanogen
chloride
is
not
route
dependent.
The
author
compared
these
results
to
those
he
obtained
in
a
similar
study
of
cyanide
gas
and
reported
that
the
symptoms
observed
following
exposure
to
cyanide
gas
were
less
severe
than
those
observed
following
exposure
to
cyanogen
chloride
vapor
(
although
it
is
unclear
whether
comparable
exposure
levels
were
tested).
The
author
also
suggested
that
some
of
the
symptoms
observed
following
cyanogen
chloride
exposure,
such
as
the
lung
congestion,
are
due
to
the
presence
of
"
chloride,"
presumably
the
chlorine
moiety
in
cyanogen
chloride.

Reed
(
1920)
also
investigated
the
effects
of
cyanogen
chloride
in
dogs
following
exposure
by
injection.
Six
dogs
(
strain
and
sex
not
specified)
were
injected
with
a
single
sublethal
dose
of
cyanogen
chloride
(
dose
not
specified)
in
0.9%
sodium
chloride
and
were
observed
for
10
to
12
days.
The
dogs
lost
up
to
15%
of
their
body
weight
and
demonstrated
symptoms
of
listlessness,

diarrhea,
cachexia,
depressed
reflexes,
cardiac
irregularity,
conjunctivitis,
and
rhinitis.
Autopsy
revealed
no
gross
lesions.
In
a
second
study,
eight
dogs
(
sex
and
strain
not
specified)
first
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
1It
is
now
known
that
sodium
thiosulfate
acts
as
a
sulfur
donor,
thus
enhancing
the
conversion
of
cyanide
to
thiocyanate
by
the
enzyme
rhodanese
(
ATSDR,
1997).
Therefore,
if
the
toxic
effects
of
cyanogen
chloride
were
due
to
its
metabolism
to
cyanide,
pretreatment
with
thiosulfate
should
reduce
the
toxicity
of
cyanogen
chloride
by
enhancing
conversion
of
its
primary
metabolite
to
a
less
toxic
compound.

EPA/
OW/
OST/
HECD
V­
6
Final
draft
received
a
protective
subcutaneous
injection
of
sodium
thiosulfate1
and
then
received
a
lethal
injection
of
cyanogen
chloride
(
dose
not
reported).
The
dogs
receiving
the
thiosulfate
lost
up
to
14%
of
their
body
weight
and
showed
greater
general
depression
and
greater
depression
of
reflexes
than
the
dogs
in
the
first
study.
Necropsy
revealed
several
dogs
had
varying
degrees
of
pulmonary
congestion.
Although
the
dogs
demonstrated
less
cardiac
irregularity,
the
author
concluded
that,
in
general,
the
symptoms
in
the
second
study
were
much
more
severe
than
those
in
the
first
study,
despite
the
administration
of
a
protective
dose
of
thiosulfate.
This
apparent
inconsistency
can
be
explained
by
the
assumption
that
the
dogs
in
the
second
study
received
a
higher
dose
of
cyanogen
chloride
than
the
dogs
in
the
first
study.
In
fact,
the
author
described
the
dose
in
the
second
study
as
lethal,
and
yet
no
mortality
was
reported.
This
suggests
that
the
sodium
thiosulfate
was
indeed
having
a
protective
effect
against
the
acute
toxicity
of
cyanogen
chloride,
and
further
suggests
that
at
least
some
of
the
acute
toxicity
of
cyanogen
chloride
results
from
its
metabolism
to
cyanide.

Cyanide.
Oral
toxicity
studies
for
cyanide
are
summarized
in
Table
VIII­
2
and
inhalation
studies
are
summarized
in
Table
VIII­
3.
Oral
LD
50
values
for
cyanide
in
rats
range
from
3
mg
CN/
kg­
day
(
Ballantyne,
1988)
to
8
mg
CN/
kg­
day
(
Smyth
et
al.,
1969)
for
cyanide
administered
as
sodium
cyanide,
and
have
been
reported
as
22
mg
CN/
kg­
day
for
cyanide
administered
as
calcium
cyanide
(
Smyth
et
al.,
1969).
In
contrast,
single
doses
of
4
mg
CN/
kg­
day
in
rats
and
6
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
7
Final
draft
mg
CN/
kg­
day
in
mice
as
potassium
cyanide
resulted
in
95%
mortality
(
Ferguson,
1962).

ATSDR
(
1997)
summarizes
the
acute
dermal
studies
of
cyanide.
Dermal
LD
50
s
in
rabbits
range
from
4.1
to
8.9
mg
CN/
kg.
Clinical
signs
observed
following
single
dermal
doses
ranging
from
0.9
to
2.5
mg
CN/
kg
include
rapid
breathing,
dizziness,
weakness,
convulsions
and
loss
of
consciousness.
ATSDR
(
1997)
also
summarizes
the
acute
inhalation
studies
of
cyanide.
LC
50
s
in
animals
range
from
154
to
543
mg
CN/
m3.

In
evaluating
oral
toxicity
of
cyanide,
both
the
total
amount
administered
and
the
rate
of
absorption
are
important.
This
is
because
toxicity
results
from
exceeding
the
body's
capacity
for
detoxification
of
cyanide
(
which
occurs
primarily
in
the
liver).
Like
any
other
enzymaticallycatalyzed
reaction,
this
detoxification
reaches
a
maximum
rate
in
the
presence
of
excess
substrate.

If
absorption
of
ingested
cyanide
proceeds
too
quickly,
the
capacity
of
the
liver
to
form
thiocyanate
upon
first
pass
of
mesenteric
blood
through
the
organ
may
be
exceeded.
In
contrast,

slow
absorption
of
the
same
total
oral
load
of
cyanide
may
allow
complete
metabolism
by
the
liver.
For
the
most
part,
cyanide
is
readily
absorbed
from
the
GI
tract,
especially
since
at
physiological
pH
(
and
in
acidic
solution)
it
is
present
mostly
in
the
highly
diffusible
nonionized
form.
However,
the
rate
of
absorption
may
be
influenced
by
factors
such
as
the
composition
and
volume
of
the
intestinal
contents
and
by
the
rate
of
peristalsis.
This
influence
of
the
rate
of
absorption
is
why
the
LD
50
values
for
sodium
cyanide
presented
above
are
lower
than
the
acute
and
chronic
LOAELs.

Palmer
and
Olson
(
1979)
administered
potassium
cyanide
to
groups
of
7
male
Sprague­

Dawley
rats
at
0
or
200
ppm
in
drinking
water,
or
at
0
or
200
ppm
in
feed
for
21
days.
These
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
8
Final
draft
doses
correspond
to
approximately
14
mg
CN/
kg­
day
in
drinking
water
and
8
mg
CN/
kg­
day
in
feed.
(
Dose
conversions
were
conducted
using
an
average
body
weight
of
0.12
kg,
water
consumption
of
0.17
L/
day,
and
food
consumption
of
0.10
kg/
day,
calculated
using
the
methods
of
U.
S.
EPA,
1988).
The
only
endpoints
evaluated
were
body
weight
gain
and
liver
weight.
No
effects
were
seen
in
the
rats
administered
cyanide
in
feed,
but
a
statistically
significant
17%

increase
in
absolute
liver
weight
was
observed
in
the
group
administered
cyanide
in
drinking
water.
The
study
authors
noted
that
the
analysis
of
the
feed
resulted
in
<
20%
of
the
theoretical
value
for
cyanide,
compared
to
95%
recovery
for
cyanide
added
to
the
feed
immediately
before
analysis.
The
study
authors
suggested
that
cyanide
added
to
the
diet
was
lost
or
fixated
(
and
therefore
unavailable),
suggesting
that
the
NOAEL
for
cyanide
in
the
diet
in
this
study
was
<
20%

of
8
mg
CN/
kg­
day,
or
<
1.6
mg
CN/
kg­
day;
the
actual
administered
dose
in
uncertain.
Some
of
the
toxicity
difference
may
have
also
been
due
to
the
difference
in
doses,
or
to
differences
in
absorption
rate
from
food
and
water.
Benchmark
dose
(
BMD)
modeling
could
not
be
conducted
for
this
study,
because
no
measure
of
variability
was
provided.

Kreutler
et
al.
(
1978)
evaluated
the
short­
term
effects
on
the
thyroid
of
oral
exposure
to
cyanide.
Male
albino
rats
(
strain
not
specified;
10­
24
animals/
group)
were
fed
diets
containing
either
2%
or
20%
casein;
treated
rats
received
the
same
diets
supplemented
with
0.2%
potassium
cyanide
for
two
weeks
(
equivalent
to
87
mg
CN/
kg­
day,
using
an
average
body
weight
of
85
g
and
the
allometric
equation
of
U.
S.
EPA
[
1988],
and
adjusting
by
the
molecular­
weight
ratio
of
cyanide
to
potassium
cyanide).
In
addition,
one
group
receiving
2%
casein
diet
with
or
without
potassium
cyanide,
and
with
or
without
iodide
supplementation.
Body
weights
and
food
consumption
were
recorded.
Blood
was
collected
and
evaluated
for
plasma
thyroid
stimulating
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
9
Final
draft
hormone
(
TSH)
levels.
Thyroids
were
removed
and
weighed.
No
difference
in
body
weight
was
observed
between
cyanide­
treated
rats
and
their
respective
controls.
Rats
treated
with
cyanide
on
the
2%
casein
diet
had
significantly
elevated
plasma­
TSH
levels
and
increased
thyroid
weights
compared
to
the
2%
casein
controls;
supplementation
with
iodide
in
addition
to
cyanide
eliminated
these
effects.
There
was
no
effect
on
TSH
or
thyroid
weight
in
the
cyanide­
treated
rats
on
the
20%
casein
diet.
This
study
suggests
that
people
with
protein­
and
iodine­
deficient
diets
may
be
a
sensitive
population.
No
consistent
guidance
is
available
on
the
interpretation
of
thyroid
effects
and
the
determination
of
which
thyroid
effects
constitute
an
adverse
effect
rather
than
an
adaptive
effect.
A
recent
peer
review
panel
evaluating
this
issue
(
Research
Triangle
Institute,

1999)
concluded
that
hormone
changes,
increased
thyroid
weight,
and
thyroid
hypertrophy
were
all
considered
to
be
adaptive
effects,
although
these
effects
are
necessary
precursors
to
adverse
effects.
Thyroid
hyperplasia
was
considered
to
be
an
adverse
effect
in
the
thyroid.
Based
on
this
analysis,
the
increased
TSH
levels
and
thyroid
weight
observed
in
Kreutler
et
al
(
1978)
could
be
considered
adaptive
effects;
although
they
are
precursors
to
adverse
effects.
However,
because
thyroid
histopathology
was
not
conducted,
it
is
not
known
whether
these
effects
were
accompanied
by
thyroid
hyperplasia.
Therefore,
the
dose
level
tested
in
this
study
is
considered
to
be
a
minimal
LOAEL.
The
BMDL
(
95%
lower
confidence
limit
on
the
benchmark
dose)
for
this
study
was
2.1
mg/
kg­
day,
based
on
increased
plasma
TSH,
but
confidence
in
this
value
is
limited,

because
only
one
nonzero
dose
was
tested
and
significant
extrapolation
below
the
data
was
required
to
reach
the
BMDL.
Details
of
the
modeling
are
provided
in
Appendix
A,
and
the
modeling
output
is
provided
in
Appendix
B.
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
2BMD
modeling
was
not
conducted
for
any
of
the
thiocyanate
studies,
since
thiocyanate
was
not
chosen
as
the
surrogate
for
calculation
of
effect
levels
for
cyanogen
chloride.

EPA/
OW/
OST/
HECD
V­
10
Final
draft
Purser
et
al.
(
1984)
exposed
Cynomolgus
monkeys
individually
to
100,
102,
123,
147,
or
156
ppm
HCN
for
up
to
30
minutes.
These
concentrations
correspond
to
106,
108,
131,
156,
and
166
mg
CN/
m3.
A
single
monkey
was
exposed
per
concentration,
with
one
monkey
exposed
to
100
ppm
and
147
ppm
in
separate
experiments.
There
was
no
control.
The
time
to
incapacitation
decreased
with
increasing
exposure
levels,
and
ranged
from
8
minutes
to
19
minutes.
The
authors
noted
that
three
of
the
exposures
(
exposure
levels
not
reported)
were
terminated
prior
to
30
minutes
due
to
the
severity
of
the
symptoms.
The
observed
symptoms
included
hyperventilation,

decreased
and
arrhythmic
heart
rate,
loss
of
muscle
tone
and
reflexes,
and
convulsions.
Blood
cyanide
levels
reached
steady
state
within
10
minutes.
There
was
no
correlation
between
air
concentration
and
blood
cyanide
levels.

Bhattacharya
et
al.
(
1994)
investigated
the
effects
of
the
inhalation
of
55
ppm
HCN
(
58
mg
CN/
m3)
for
30
minutes
on
the
pulmonary
mechanics
of
six
male
Wistar
rats.
The
air
flow
was
increased,
accompanied
by
increased
transthoracic
pressure
and
tidal
volume.
The
respiratory
rate,
compliance,
and
minute
volume
decreased,
accompanied
by
a
decrease
in
pulmonary
lipids.

Other
effects
of
cyanide
were
not
evaluated.

Thiocyanate.
Toxicity
studies
for
thiocyanate
are
summarized
in
VIII­
4.
No
short­
term
inhalation
or
dermal
toxicity
studies
of
thiocyanate
in
animals
were
identified.
2
Most
of
the
acute
toxicity
studies
with
thiocyanate
were
conducted
prior
to
the
advent
of
modern
toxicologicaltesting
methods,
and
concentrated
on
identifying
lethal
doses.
For
example,
Gorman
et
al.
(
1949)
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
11
Final
draft
reported
that
the
minimal
lethal
dose
of
sodium
thiocyanate
in
guinea
pigs
is
200­
400
mg/
kg
(
143­

286
mg
SCN/
kg).
Anderson
and
Chen
(
1940)
reviewed
the
literature
on
acute
toxicity
of
thiocyanate
in
animals.
They
found
that
600­
800
mg/
kg
of
potassium,
sodium,
or
ammonium
thiocyanate
was
lethal
to
guinea
pigs
(
dose
conversion
not
possible
because
form
not
specified).

They
also
reported
that
1000
mg/
kg
potassium
thiocyanate
was
always
fatal
to
rabbits,
and
a
single
dose
of
500
mg/
kg
was
"
never
fatal."
These
doses
correspond
to
600
and
300
mg
SCN/
kg,

respectively.

Taubman
and
Heilborn
(
1930;
as
cited
in
Lindberg
et
al.,
1941;
study
in
German)
reported
that
administration
of
2
doses
of
200
mg/
kg
potassium
thiocyanate
(
120
mg
SCN/
kg)
to
15
guinea
pigs
(
sex
and
strain
not
specified)
resulted
in
a
25%
decrease
in
hemoglobin
and
erythrocytes.
Information
was
not
available
as
to
whether
the
doses
were
administered
on
the
same
day.
Smaller
doses
given
over
longer
periods
resulted
in
greater
decreases
in
these
parameters
(
dosing
regimen
not
specified).
No
NOAEL
was
determined
in
this
study.
Given
the
information
provided
in
the
study,
the
LOAEL
was
120
mg
SCN/
kg,
but
the
likely
target
organ
(
thyroid)
was
apparently
not
evaluated.

Wolff
et
al.
(
1946)
exposed
rats
(
4­
6/
group;
sex
and
strain
not
specified)
to
0.5%

potassium
thiocyanate
in
the
diet
for
18
or
24
days.
Assuming
a
food
factor
of
0.096
(
based
on
the
average
across
strains
and
sexes,
U.
S.
EPA,
1988),
this
corresponds
to
a
dose
of
approximately
287
mg
SCN/
kg­
day.
Controls
received
a
basal
diet.
Only
body
weight
and
thyroid
parameters
were
evaluated.
There
was
no
clear
effect
on
body
weight,
although
this
was
difficult
to
evaluate,
since
several
of
the
control
and
exposed
animals
lost
weight.
Treated
rats
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
12
Final
draft
had
increased
thyroid
weights
and
decreased
thyroxine
iodine
and
total
iodine
in
the
thyroid.

Protein­
bound
iodine
in
the
plasma
(
a
measure
of
triiodothyronine
[
T3]
and
thyroxine
[
T4])
was
also
decreased
in
the
treated
rats.
No
NOAEL
was
determined,
and
the
LOAEL
was
287
mg
SCN/
kg­
day,
based
on
the
thyroid
effects.

Rawson
et
al.
(
1944)
exposed
male
Sherman
rats
(
25/
group)
to
0.25%
potassium
thiocyanate
in
drinking
water
for
28
days.
Controls
received
drinking
water
without
added
potassium
thiocyanate.
Using
the
average
drinking­
water
consumption
across
male
rats
of
0.145
L/
kg­
day
(
calculated
from
U.
S.
EPA,
1988),
this
corresponds
to
doses
of
0
and
217
mg
SCN/

kgday
The
authors
noted
that
the
intake
of
iodine
was
borderline­
deficient,
based
on
the
amount
in
the
diet,
together
with
iodine
supplementation
of
the
drinking
water.
Thyroid
weight
was
increased
in
the
potassium
thiocyanate­
treated
rats.
At
necropsy,
the
thyroids
of
treated
rats
were
dark
red,
highly
vascularized,
and
grossly
enlarged;
histopathology
revealed
marked
hyperplasia
and
loss
of
colloid.
Uptake
of
radiolabeled
iodine
by
the
thyroid
was
increased.
No
NOAEL
was
determined
in
this
study,
and
the
LOAEL
was
217
mg
SCN/
kg­
day,
based
on
thyroid
toxicity.

De
Groot
et
al.
(
1991)
exposed
male
F344
rats
(
10/
group)
to
0
or
0.2%
potassium
thiocyanate
in
the
diet
for
4
weeks.
Based
on
the
average
of
the
initial
and
final
body
weights
(
124
g)
and
the
reported
food
intake
of
12.8
g/
rat/
day,
the
daily
dose
was
123
mg
SCN/
kg­
day.

There
was
no
effect
on
relative
liver
or
kidney
weight.
A
statistically
significant
decrease
in
hemoglobin
and
increase
in
prothrombin
time
was
observed.
However,
the
most
marked
effects
were
on
the
thyroid,
with
marked
and
statistically
significant
decreases
in
T4
and
increased
TSH
and
thyroid
weight.
(
T3
levels
were
not
measured.)
A
blind
evaluation
of
the
thyroid
also
found
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
13
Final
draft
moderate
activation
of
the
thyroid
follicles
(
20­
50%
of
follicles
activated).
The
LOAEL
in
this
study
was
123
mg
SCN/
kg­
day.

Summary
of
Short­
Term
Exposures
Only
four
old
short­
term
studies
of
cyanogen
chloride
were
located
(
Reed,
1920;
Aldridge
and
Evans,
1946;
Haymaker
et
al.,
1952;
Flury
and
Zernik,
1931).
Rats,
cats,
dogs,
and
a
goat
were
exposed
by
either
inhalation
or
injection.
These
studies
are
unsuitable
for
risk
assessment
because
key
information
about
doses
and
study
design
are
not
reported.
However,
the
studies
do
help
to
identify
the
potential
health
effects
of
cyanogen
chloride,
which
include
neurotoxicity
(
depressed
reflexes,
muscular
tremors,
rigidity
and
weakness
of
limbs,
convulsions,
necrosis
in
brain),
weight
loss,
cardiac
irregularities,
and
pulmonary
congestion
and
edema.
Cyanogen
chloride
also
irritates
the
respiratory
passages
and
eyes.

Only
limited
information
regarding
the
short­
term
effects
of
cyanide
in
animals
is
available.

LD
50
s
(
either
oral
or
dermal)
for
cyanide
range
from
about
3
to
9
mg/
kg;
inhalation
LC
50
s
range
from
154
to
543
mg/
m3.
Inhalation
exposure
of
rats
or
monkeys
for
30
minutes
resulted
in
signs
of
neurotoxicity
(
loss
of
muscle
tone
and
reflexes,
convulsions),
decreased
and
arrhythmic
heart
rate,
and
alterations
in
respiration
(
increased
air
flow,
decreased
respiratory
rate,
compliance,
and
minute
volume)
(
Purser
et
al.,
1984;
Bhattacharya
et
al.,
1994).
Two­
week
oral
exposure
of
rats
to
87
mg
CN/
kg­
day
resulted
in
thyroid
toxicity
(
decreased
TSH
and
increased
thyroid
weights)

in
animals
that
were
protein­
and
iodine­
deficient
(
Kreutler
et
al.,
1978).
No
effects
were
observed
in
animals
with
an
adequate
protein
diet.
Supplementation
of
protein­
deficient
rats
with
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
14
Final
draft
iodine
also
eliminated
the
effects
of
cyanide
on
thyroid.
Protein
deficiency
is
rare
in
Western
populations
(
U.
S.
FDA,
1999),
but
iodine
deficiency
occurs
in
approximately
5­
8%
of
the
U.
S.

population
(
Hollowell
et
al.,
1998),
as
described
further
in
Chapter
7.

Although
there
is
a
relatively
large
number
of
animal
studies
on
the
effects
of
thiocyanate
in
animals,
most
of
the
studies
concentrated
on
the
key
target
organ,
the
thyroid,
rather
than
evaluating
a
range
of
endpoints.
More
importantly,
many
of
the
studies
tested
only
a
single
dose,

so
a
dose­
response
could
not
be
evaluated,
and
often
a
NOAEL
could
not
be
identified.
The
animal
studies
consistently
reported
decreased
plasma­
T4
levels
and
increased
thyroid
weight;

effects
on
T3
were
inconsistent.
Other
studies
reported
decreased
mammary
development
at
similar
doses
(
possibly
secondary
to
thyroid
effects),
and
decreased
hemoglobin.
Short­
term
animal
toxicity
data
are
available
from
rats
(
Wolff
et
al.,
1946;
Rawson
et
al.,
1944;
De
Groot
et
al.,
1991)
and
guinea
pigs
(
Taubman
and
Heilborn,
1930).
No
NOAEL
was
identified
in
any
of
the
studies.
The
lowest
reliable
LOAEL
was
123
mg
SCN/
kg­
day,
based
on
decreased
T4,

increased
thyroid
weight,
and
activation
of
thyroid
follicles
(
De
Groot
et
al.,
1991).
Decreased
hemoglobin
was
also
observed
in
guinea
pigs
following
2
doses
of
120
mg
SCN/
kg/
dose
(
Taubman
and
Heilborn,
1930).

B.
Long­
Term
Exposures
Cyanogen
chloride.
No
long­
term
toxicity
studies
of
cyanogen
chloride
via
any
route
were
located.
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
15
Final
draft
Cyanide.
No
long­
term
toxicity
studies
of
cyanide
by
the
inhalation
or
dermal
routes
were
located.
NTP
(
1993)
reported
the
results
of
a
subchronic
bioassay
of
sodium
cyanide
administered
in
drinking
water
to
rats
and
mice.
F344
rats
and
B6C3F1
mice
(
10/
sex/
group)
were
administered
sodium
cyanide
in
drinking
water
at
concentrations
of
0,
3,
10,
30,
100,
or
300
ppm
for
13
weeks.
These
concentrations
are
equivalent
to
the
following
doses,
estimated
by
the
study
authors
(
and
converted
to
CN
equivalents)
based
on
measured
body
weights
and
water
consumption:
male
rats
­
0,
0.16,
0.48,
1.4,
4.5,
and
12.5
mg
CN/
kg­
day;
female
rats
­
0,
0.16,

0.53,
1.7,
4.9,
and
12.5
mg
CN/
kg­
day;
male
mice
­
0,
0.26,
0.96,
2.7,
8.6,
and
24.4
mg
CN/

kgday
female
mice
­
0,
0.32,
1.1,
3.3,
10.1,
and
28.8
mg
CN/
kg­
day.
The
parameters
evaluated
included
body
weight,
clinical
signs,
water
consumption,
clinical
chemistry,
hematology,

urinalysis,
selected
organ
weights
(
heart,
kidney,
liver,
lungs,
testis,
and
thymus),
histopathology,

sperm
motility,
and
vaginal
cytology.
NTP
did
not
measure
thyroid
hormones.

In
rats,
there
were
no
treatment­
related
effects
on
mortality,
body
weight,
or
clinical
signs
in
either
males
or
females.
There
was
a
dose­
related
decrease
in
water
consumption
that
was
greater
than
10%
in
both
sexes
receiving
100
or
300
ppm,
compared
with
controls.
Decreased
urine
volume
and
increased
urine
specific
gravity
were
observed
in
the
high­
dose
male
rats
(
these
endpoints
were
apparently
not
measured
in
females)
but
were
attributed
to
the
decrease
in
water
consumption
rather
than
a
specific
adverse
effect
of
cyanide.
Urinary
thiocyanate
concentration
increased
in
all
animals
at
concentrations
of
30
ppm
and
higher.
There
was
no
effect
on
organ
weight
in
males,
but
there
was
a
small
(
16%
for
absolute
weight),
statistically
significant
increase
in
absolute
and
relative
liver
weight
in
high­
dose
females.
The
study
authors
did
not
consider
any
effects
on
organ
weights
to
be
chemical­
related.
There
were
no
histopathological
changes
that
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
16
Final
draft
were
attributed
to
cyanide
exposure.
In
particular,
no
effects
were
observed
in
either
the
thyroid
or
the
brain.
In
male
rats,
there
were
significant
decreases
in
left
cauda
epididymis
weight
and
sperm
motility
at
concentrations

30
ppm
(
1.4
mg
CN/
kg­
day)
(
Table
V­
1).
However,
the
authors
considered
that
the
changes
in
sperm
motility
were
not
biologically
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
17
Final
draft
Table
V­
1.
Reproductive
Effects
in
Rats
and
Mice
Administered
Sodium
Cyanide
in
Drinking
Water
for
13
Weeks.

Study
Parameter
0
ppm
30
ppm
100
ppm
300
ppm
Male
Rats
Dose
(
mg
CN/
kg­
day)
0
1.4
4.5
12.5
Body
weight
(
g)
338
±
5a
335
±
5
338
±
4
319
±
5*

Left
epididymis
(
g)
0.448
±
0.006
0.437
±
0.005
0.425
±
0.007
0.417
±
0.005**

Left
cauda
epididymis
(
g)
0.162
±
0.003
0.150
±
0.004*
0.148
±
0.004*
0.141
±
0.003**

Left
testis
(
g)
1.58
±
0.03
1.56
±
0.02
1.52
±
0.02
1.46
±
0.02**

Spermatid
heads
(
107/
testis)
17.86
±
0.61
16.94
±
0.81
16.58
±
0.63
15.42
±
0.44*

Spermatid
count
(
mean/
10­
4
mL
suspension)
89.28
±
3.05
84.68
±
4.03
82.90
±
3.16
77.10
±
2.20*

Motility
(%)
94.24
±
0.58
90.67
±
1.25*
92.09
±
0.85*
90.66
±
1.46*

Male
Mice
Dose
(
mg
CN/
kg­
day)
0
2.7
8.6
24.3
Body
weight
(
g)
37
±
1.0
39.2
±
1.3
38.6
±
1.1
35.5
±
1.1
Left
epididymis
(
g)
0.049
±
0.001
0.047
±
0.002
0.047
±
0.001
0.044
±
0.001*

Left
cauda
epididymis
(
g)
0.017
±
0.001
0.016
±
0.000
0.015
±
0.001
0.014
±
0.001*

Left
testis
(
g)
0.121
±
0.002
0.113
±
0.008
0.117
±
0.002
0.118
±
0.003
Spermatid
heads
(
107/
testis)
2.24
±
0.14
2.26
±
0.14
2.03
±
0.15
2.11
±
0.16
Spermatid
count
(
mean/
10­
4
mL
suspension)
69.94
±
4.34
70.80
±
4.25
63.28
±
4.53
66.06
±
4.87
Motility
(%)
92.38
±
0.81
90.63
±
1.34
91.43
±
0.55
89.52
±
0.96
Adapted
from
NTP
(
1993)
a.
Mean
±
S.
E.
*
Significantly
different
from
control
p

0.05
**
Significantly
different
from
control
p

0.01
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
18
Final
draft
significant,
because
they
were
small
and
within
the
range
of
historical
controls.
Dose­
related
decreases
in
the
left
epididymis
weight,
left
testis
weight,
number
of
spermatid
heads
(
per
testis),

and
spermatid
count
(
per
mL
suspension)
were
observed,
with
the
decreases
at
the
high
dose
(
12.5
mg
CN/
kg­
day)
statistically
significant.
The
study
authors
considered
the
effect
at
the
high
dose
to
be
consistent
with
a
small
but
measurable
adverse
effect
on
male
reproduction,
although
they
suggested
that
the
observed
effects
alone
are
insufficient
to
decrease
fertility
in
rats.
Female
rats
in
the
100­
and
300­
ppm
groups
(
4.9
and
12.5
mg
CN/
kg­
day)
spent
significantly
more
time
in
proestrus
and
diestrus
compared
with
controls,
but
there
was
no
clear
dose
response
and
the
authors
did
not
consider
these
results
to
be
chemical­
related.
Although
1.4
mg
CN/
kg­
day
might
be
considered
a
minimal
LOAEL
based
on
a
statistically
significant
decrease
in
left
caudal
epididymis
weight,
the
dose­
response
at
this
dose
and
the
next
higher
dose
(
4.5
mg/
kg­
day)
was
very
shallow
and
the
magnitude
of
the
decrease
was
only
6.5%
and
9%,
respectively.
Based
on
the
minimal
degree
of
effect
at
the
dose
of
4.5
mg/
kg­
day,
the
high
dose
of
12.5
mg
CN/
kg­
day
is
the
LOAEL
in
this
study,
based
on
male
reproductive
effects
in
several
related
endpoints
(
decreased
epididymal
weight,
decreased
sperm
levels,
decreased
testis
weight),
and
the
NOAEL
is
4.5
mg
CN/
kg­
day.
Benchmark
dose
modeling
was
conducted
for
several
endpoints
in
this
study,
as
described
in
Appendix
A.
The
most
sensitive
BMDL
was
0.79
mg
CN/
kg­
day,

calculated
based
on
decreased
left
epididymis
weight,
supported
by
a
BMDL
of
1.3
mg/
kg­
day
for
both
decreased
spermatid
heads/
testis
and
decreased
spermatid
count.

In
mice,
there
were
no
significant
treatment­
related
effects
on
mortality,
body
weight,
or
clinical
signs.
Water
consumption
in
both
males
and
females
was
decreased
in
the
100­
and
300­

ppm
groups.
No
treatment­
related
effects
were
observed
in
clinical
chemistry,
hematology,
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
19
Final
draft
urinalysis,
organ
weights,
or
histopathology.
In
males,
the
weights
of
the
left
epididymis
and
left
cauda
epididymis
were
significantly
decreased
in
the
high­
dose
group
(
24.4
mg
CN/
kg­
day).

However,
there
were
no
effects
on
sperm
motility
or
spermatid
density
in
males,
or
on
estrous
cycle
length
in
females.
Absolute
and
relative
liver
weights
were
statistically
significantly
increased
by
18%
(
absolute
weight)
in
the
high­
dose
group,
and
there
was
an
indication
of
a
doseresponse
The
study
authors
considered
the
increased
organ
weights
sporadic
and
not
chemicalrelated
Based
on
male
reproductive
effects
(
decreased
epididymal
weight),
this
study
identified
a
NOAEL
of
8.6
mg
CN/
kg­
day
and
a
LOAEL
of
24.4
mg
CN/
kg­
day
in
mice.
Benchmark
dose
modeling
was
conducted
for
several
endpoints
in
this
study,
as
described
in
Appendix
A.
The
most
sensitive
BMDL
was
12
mg
CN/
kg­
day,
calculated
based
on
decreased
left
caudal
epididymis
weight.

Kamalu
(
1993)
evaluated
the
short­
term
toxicity
of
inorganic
cyanide
administered
in
diet
to
dogs.
Six
male
dogs
per
group
(
strain
not
specified)
were
administered
sodium
cyanide
in
diet
for
14
weeks
at
doses
of
0
or
1.04
mg
CN/
kg­
day
(
based
on
a
reported
food
consumption
of
0.1
kg
food/
kg
body
weight).
Blood
was
obtained
from
each
dog
at
weeks
1,
3,
and
14;
urine
was
collected
at
weeks
1,
3,
5,
7,
and
14.
Plasma­
and
urinary­
thiocyanate
concentrations
were
determined.
In
addition,
serum
enzymes,
total
serum
protein,
serum
albumin,
serum
globulin,
and
urinary
protein
were
measured.
A
histopathological
evaluation
was
performed
on
the
liver,

kidney,
myocardium,
testis
and
adrenal
gland
of
each
dog.
Both
plasma­
and
urinary­
thiocyanate
concentrations
were
significantly
increased
in
the
treated
dogs
compared
with
controls
at
all
time
points
evaluated.
In
addition,
treated
dogs
had
significantly
increased
urinary
protein
concentrations
compared
with
controls
at
weeks
5
and
14.
No
treatment­
related
effects
were
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
20
Final
draft
observed
in
serum
enzymes,
total
serum
protein,
albumin,
or
globulin.
No
histopathological
changes
were
observed
in
the
liver
or
myocardium
of
treated
dogs;
however,
treatment­
related
effects
were
observed
in
kidney,
testis,
and
adrenal
gland.
Kidneys
of
the
treated
dogs
demonstrated
casts
in
the
lumina
of
the
tubules
and
occasional
desquamation.
In
testis,
the
treated
dogs
had
a
significantly
decreased
percentage
of
tubules
in
stage
8
of
the
spermatogenic
cycle
(
characterized
by
elongated
spermatids
lining
the
seminiferous­
tubule
lumens)
compared
with
controls.
In
addition,
treated
dogs
had
an
increased
incidence
compared
to
the
controls
of
animals
with
abnormal
cells
and
sloughing
of
germ
cells
in
the
seminiferous
tubules.
Finally,
the
zona
glomerulosa
of
the
adrenal
gland
was
significantly
wider
in
treated
dogs
compared
with
controls.
This
study
indicates
that
cyanide
may
be
a
reproductive
toxicant
in
male
dogs.
Based
on
histopathological
changes
in
kidney,
testis,
and
adrenal
gland,
the
dose
of
1.04
mg
CN/
kg­
day
is
considered
to
be
a
LOAEL.
However,
this
LOAEL
is
not
relevant
for
the
assessment
of
effects
in
humans.
Dogs
are
not
a
suitable
model
for
the
toxicity
of
cyanide
in
humans,
because
levels
of
rhodanese
(
the
enzyme
which
detoxifies
cyanide)
in
dogs
are
much
lower
than
the
levels
in
humans
(
ATSDR,
1997).
Therefore,
dogs
are
more
sensitive
than
humans
to
the
effects
of
cyanide.
Similarly,
BMD
modeling
was
not
done
on
this
study,
since
dogs
are
not
an
appropriate
model
for
cyanide
risk
assessment.

Jackson
(
1988)
evaluated
the
effects
of
oral
administration
of
potassium
cyanide
on
thyroid
function
and
behavior
in
miniature
pigs.
Doses
of
0,
0.4,
0.7,
or
1.2
mg
CN/
kg­
day
potassium
cyanide
were
administered
to
3
pigs/
group
using
a
plastic
syringe
placed
at
the
back
of
the
animals'
throats.
The
solutions
were
administered
once
daily
for
24
weeks,
just
before
the
daily
meal
to
increase
the
absorption
of
cyanide.
A
total
of
five
females
and
seven
males
were
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
21
Final
draft
used;
each
group
contained
both
male
and
female
animals.
Serum
levels
of
T3,
T4,
glucose,
and
thiocyanate
were
measured
every
six
weeks.
Behavioral
evaluations
were
conducted
daily.
The
scope
of
behaviors
evaluated
fell
into
two
major
categories:
performance
measures
included
innate
behavior,
and
learning
measures
included
the
acquisition
and
retention
of
new
behaviors.

No
other
endpoints
were
evaluated.
Both
T3
and
T4
demonstrated
a
dose­
related
decrease
that
was
statistically
significant
by
week
18
of
the
study.
Serum­
thiocyanate
levels
were
positively
correlated
with
cyanide
dose,
demonstrating
that
the
cyanide
was
being
metabolized
by
the
animals.
A
variety
of
behaviors
were
significantly
altered
in
treated
animals,
including
a
decrease
in
dominance
behavior
(
high­
dose
group),
decrease
in
fighting
(
mid­
and
high­
dose
group),

increase
in
victimization
(
all
treated
groups),
decrease
in
exploratory
behaviors
(
all
groups),
and
less
aggressive
feeding
patterns
(
high­
dose
group).
The
authors
concluded
that
the
overall
pattern
of
behavioral
changes
in
the
1.2
mg
CN/
kg­
day
group
was
different
from
the
untreated
animals,
but
that
the
changes
at
the
lower
doses
were
too
inconsistent
to
be
considered
adverse.

This
study
is
limited
by
the
small
number
of
animals
(
only
3/
group).
Because
an
uneven
number
of
males
and
females
were
used,
at
least
one
group
would
have
had
to
include
one
male
and
two
females,
while
the
remaining
groups
would
have
had
two
males
and
one
female.
The
small
size
and
mixed
sexes
of
the
groups
would
contribute
to
high
variability
in
the
results,
particularly
because
the
endpoints
evaluated,
hormone
levels
and
behavior,
tend
to
differ
between
sexes.

Also,
no
information
is
provided
on
the
biological
significance
of
the
altered
hormone
levels.

Although
the
hormones
showed
statistically
significant
differences
between
groups,
they
could
still
be
within
the
range
of
normal
for
this
species.
In
addition,
the
study
did
not
evaluate
thyroid
histopathology
to
determine
if
cyanide's
effects
were
adverse
or
adaptive.
Although
this
study
is
incomplete
for
risk­
assessment
purposes,
it
does
confirm
that
the
thyroid
and
nervous
system
are
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
22
Final
draft
target
organs
for
cyanide.
Based
on
behavioral
changes
and
decreased
thyroid
hormones,
the
1.2
mg
CN/
kg­
day
dose
level
is
considered
to
be
a
LOAEL
and
the
0.7
mg
CN/
kg­
day
dose
is
considered
to
be
a
NOAEL.
BMD
modeling
was
not
done
on
this
study,
due
to
the
uncertainties
regarding
the
data
reporting,
particularly
reporting
of
averages
across
males
and
females
in
group
despite
differences
in
response
by
sex
and
differences
in
the
numbers
of
males/
females
per
group.

Philbrick
et
al.
(
1979)
evaluated
the
long­
term
health
effects
of
oral
exposure
to
cyanide
in
rats.
Male
rats
(
10/
group,
strain
not
specified)
received
diets
(
10%
casein
supplemented
with
0.3%
methionine,
potassium
iodide
and
vitamin
B
12)
containing
either
0
or
1500
ppm
potassium
cyanide
for
11.5
months.
Parallel
studies
were
conducted
with
rats
provided
a
diet
deficient
in
methionine,
iodine,
and
vitamin
B
12,
containing
0
or
1500
ppm
potassium
cyanide.
Based
on
the
average
food
factor
across
rat
strains
of
0.073
kg/
kg
body
weight/
day
for
a
chronic
study
(
U.
S.

EPA,
1988)
and
adjusting
for
the
molecular
weight
ratio
of
cyanide
to
potassium
cyanide,
the
rats
received
a
dose
of
0
or
44
mg
CN/
kg­
day.
At
4
and
11
months,
plasma
T4
levels,
T4
secretion
rates,
and
urinary
thiocyanate
levels
were
measured
in
5
animals/
group.
After
sacrifice,
brain,

heart,
liver,
and
thyroid
weights
were
recorded.
Histopathologic
evaluation
was
conducted
on
the
brains,
optic
and
sciatic
nerves,
spinal
cords,
and
thyroid
glands.
Body­
weight
gains
of
the
treated
animals
were
significantly
lower
than
controls
beginning
at
week
8.
Administration
of
cyanide
altered
thyroid
function
at
both
4
and
11
months.
Compared
with
control
animals,
rats
in
the
cyanide
exposure
groups
had
significantly
decreased
plasma
T4
levels,
decreased
T4
secretion
rates,
and
increased
thyroid
weights
at
4
months.
At
11.5
months,
thyroid
weight
was
increased
and
T4
secretion
rate
was
decreased.
Similar,
but
more
severe
effects
were
observed
in
the
rats
provided
the
deficient
diet.
No
histopathologic
effects
were
observed
in
optic
or
sciatic
nerve,
or
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
23
Final
draft
thyroid.
However,
vacuolation
and
demyelination
was
observed
in
the
spinal­
cord
white
matter
of
treated
animals
compared
to
controls.
As
discussed
above
for
Kreutler
et
al.
(
1978),
altered
thyroid
hormones
and
increased
thyroid
weight
without
accompanying
thyroid
hyperplasia
could
be
considered
adaptive
rather
than
adverse.
Based
on
neurotoxicity,
the
dose
of
44
mg
CN/

kgday
is
considered
to
be
a
LOAEL.
BMD
modeling
could
not
be
done
on
the
neurological
effects
in
this
study,
because
no
quantitative
results
were
available.
A
BMDL
of
19
mg
CN/
kg­
day
was
calculated
for
decreased
thyroxine
(
T4)
secretion
in
the
rats
with
normal
diets,
and
a
BMDL
of
12
mg
CN/
kg­
day
was
calculated
for
the
same
endpoint
in
rats
fed
the
deficient
diets.
However,
this
endpoint
may
be
adaptive,
rather
than
adverse.

Howard
and
Hanzal
(
1955)
conducted
a
2­
year
dietary
study
in
which
10
rats/
sex/
group
were
administered
food
fumigated
with
hydrogen
cyanide
(
HCN).
The
average
daily
concentrations
were
73
and
183
mg
CN/
kg
diet.
From
the
data
reported
on
food
consumption
and
body
weight,
daily
estimated
doses
were
4.3
mg
and
10.8
mg
CN/
kg
body
weight.
The
average
concentrations
of
cyanide
in
the
food
were
estimated
based
on
the
authors'
data
for
concentrations
at
the
beginning
and
end
of
each
food
preparation
period
and
by
assuming
a
firstorder
rate
of
loss
for
the
intervening
period.
There
were
no
treatment­
related
effects
on
growth
rate,
no
gross
signs
of
toxicity,
and
no
histopathologic
lesions.
BMD
modeling
could
not
be
done
for
this
study,
since
no
adverse
effects
were
observed.

Thiocyanate.
Several
studies
in
animals
examined
the
effects
of
subchronic
oral
exposure
to
thiocyanate
(
Kanno
et
al.,
1990;
Lindberg
et
al.,
1941;
Nagasawa
et
al.,
1980;
Philbrick
et
al.,

1979;
Pyska,
1977).
Most
of
these
studies
have
concentrated
on
further
elucidating
the
known
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
24
Final
draft
thyroid
effects
of
thiocyanate.
BMD
modeling
was
not
conducted
for
any
of
the
thiocyanate
studies,
since
thiocyanate
was
not
chosen
as
the
surrogate
for
calculation
of
effect
levels
for
cyanogen
chloride.

Kanno
et
al.
(
1990)
exposed
male
Fischer
344/
DuCrj
rats
(
28­
30/
group)
to
0.5%

potassium
thiocyanate
in
the
drinking
water
for
25
weeks.
Assuming
a
reference
body
weight
of
0.18
kg
and
water
consumption
of
0.028
L/
day
(
U.
S.
EPA,
1988),
and
adjusting
for
the
molecular
weight
of
thiocyanate
and
potassium
thiocyanate,
the
estimated
dose
is
465
mg
SCN/
kg­
day.

Controls
received
drinking
water
without
added
potassium
thiocyanate.
Only
thyroid­
related
parameters
were
evaluated.
Treated
rats
showed
a
significant
increase
in
thyroid
weight.

Histopathologic
analysis
of
the
thyroids
showed
slight
diffuse
hyperplasia
and
increased
colloid,

so
that
the
percent
area
occupied
by
the
follicular
epithelial
cells
relative
to
total
thyroid
area
was
decreased
relative
to
controls.
Treated
rats
had
significantly
increased
serum
levels
of
thyroid
stimulating
hormone
and
T3,
and
decreased
serum
levels
of
T4.
No
neoplasias
were
observed
in
the
thyroids
of
control
or
treated
rats.
A
NOAEL
was
not
determined
in
this
study.
The
LOAEL
for
this
study
was
465
mg
SCN/
kg­
day,
based
on
thyroid
toxicity.

Nagasawa
et
al.
(
1980)
exposed
female
SHN
mice
(
18/
group)
to
0.1%
or
0.3%
potassium
thiocyanate
in
the
drinking
water
for
12
weeks.
Controls
received
tap
water.
Using
the
average
water
consumption
across
strains
of
0.2718
L/
kg­
day
(
calculated
from
U.
S.
EPA,
1988),
this
corresponds
to
doses
of
0,
163,
and
488
mg
SCN/
kg­
day.
Plasma
T4
was
statistically
significantly
decreased
at
both
doses
of
potassium
thiocyanate,
and
T3
was
decreased
at
the
high
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
25
Final
draft
dose.
Other
systemic
toxicity
endpoints
were
not
evaluated.
A
NOAEL
was
not
determined
in
this
study.
The
LOAEL
was
163
mg
SCN/
kg­
day,
based
on
thyroid
toxicity.

Pyska
(
1977)
exposed
3­
week­
old
female
Wistar
rats
(
17
 
19/
group)
to
0
or
0.1%

potassium
thiocyanate
in
drinking
water
for
approximately
10
weeks
(
until
the
rats
were
3
months
old).
Using
the
allometric
equation
of
U.
S.
EPA
(
1988)
and
a
body
weight
of
0.14
kg,
a
food
factor
of
0.167
can
be
calculated,
resulting
in
an
estimated
dose
of
100
mg/
kg­
day.
However,
the
actual
dose
may
have
been
lower,
in
light
of
the
lower
drinking
water
consumption
in
the
accompanying
developmental
toxicity
study
(
see
Section
V.
C).
Higher
doses
were
reported
to
cause
mortality,
but
no
supporting
data
were
provided.
There
was
a
statistically
significant
decrease
in
final
body
weight
of
the
dosed
group
compared
to
the
controls,
although
the
magnitude
of
the
decrease
(
only
8%)
did
not
reach
biological
significance.
There
was
also
a
statistically
significant
decrease
in
plasma
protein­
bound
iodine
(
a
measure
of
T3
and
T4).
The
only
dose
tested,
100
mg
SCN/
kg­
day,
was
a
LOAEL,
based
on
thyroid
toxicity.

Philbrick
et
al.
(
1979)
fed
male
weanling
rats
(
10/
group;
strain
not
specified)
for
11.5
months
with
control
casein
diets
(
supplemented
with
0.3%
DL­
methionine,
potassium
iodide,
and
vitamin
B
12)
or
with
similarly­
supplemented
casein
diets
containing
2240
ppm
potassium
thiocyanate.
Assuming
a
food
factor
of
0.073
(
average
across
strains,
U.
S.
EPA,
1988),
this
corresponds
to
a
dose
of
98
mg
SCN/
kg­
day.
No
deaths,
clinical
signs,
or
adverse
effects
on
body
weight
gain
were
observed
in
the
potassium
thiocyanate­
treated
rats.
However,
the
rats
treated
with
potassium
thiocyanate
had
significantly
decreased
T4­
secretion
rates
and
plasma­
T4
levels
after
4
months;
after
11
months
of
exposure,
thyroid
weight
was
significantly
increased
and
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
26
Final
draft
plasma
T4
was
significantly
decreased,
but
T4­
secretion
rate
was
unaffected.
Histopathological
analysis
showed
no
effects
on
the
thyroid,
optic
nerve,
sciatic
nerve,
or
other
neural
tissues.
The
effects
on
the
thyroid
were
seen
with
or
without
potassium
iodide
supplementation.
In
addition,

modest
myelin
degeneration
(
compared
to
the
corresponding
unsupplemented
control)
was
observed
in
the
group
receiving
thiocyanate
but
no
iodide
supplement.
No
NOAEL
was
determined
in
this
study.
The
LOAEL
was
98
mg
SCN/
kg­
day,
based
on
thyroid
toxicity.

Lindberg
et
al.
(
1941)
gave
12
dogs
(
breed
and
sex
not
specified)
potassium
thiocyanate
orally
(
325
mg/
dose,
corresponding
to
194
mg
SCN/
dose)
and
examined
effects
on
erythrocyte
count,
hematocrit,
serum
proteins,
and
plasma
cholesterol.
Neither
the
frequency
nor
the
duration
of
dosing
was
reported,
although
the
authors
reported
that
the
dosing
was
for
a
"
long
period."

Thiocyanate
levels
in
blood
and
hematology
were
monitored
for
4­
27
weeks,
but
it
is
unclear
whether
dosing
continued
for
that
long.
Thyroid­
related
endpoints
were
not
evaluated.
Blood
thiocyanate
levels
ranged
from
13
mg/
100
mL
to
75
mg/
100
mL.
Decreases
in
serum
cholesterol,

total
protein,
erythrocyte
count,
and
hematocrit
were
observed.
Histopathological
analyses
showed
bone­
marrow
acellularity
and
fatty
vacuolation
of
the
liver.
Insufficient
information
was
provided
to
determine
a
NOAEL
or
LOAEL
for
these
effects.

Summary
of
Long­
Term
Exposures
No
long­
term
toxicity
studies
of
cyanogen
chloride
are
available.
Subchronic
toxicity
data
for
cyanide
by
oral
exposure
are
available
in
rats
(
NTP,
1993;
Philbrick
et
al.,
1979),
mice
(
NTP,
1993),
dogs
(
Kamalu,
1993),
and
miniature
pigs
(
Jackson,
1988).
The
only
chronic
study
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
27
Final
draft
(
Howard
and
Hanzal,
1955)
of
cyanide
identified
a
free­
standing
NOAEL
of
10.8
mg
CN/
kg­
day.

No
data
on
the
effects
of
subchronic
or
chronic
exposure
to
cyanide
by
the
inhalation
or
dermal
routes
were
located.
The
older
studies
of
cyanide
(
Philbrick
et
al.,
1979;
Jackson,
1988)

established
that
the
CNS
and
thyroid
are
targets
of
long­
term
cyanide
toxicity.
Philbrick
et
al.

(
1979)
observed
demyelination
of
the
spinal
cord,
decreased
plasma­
T4
levels,
and
increased
thyroid
weights
in
rats
ingesting
cyanide
(
44
mg
CN/
kg­
day)
in
the
diet
for
11.5
months.
Jackson
(
1988)
observed
behavioral
changes
and
decreased
levels
of
T3
and
T4
in
pigs
that
received
cyanide
in
water
for
24
weeks,
with
a
NOAEL
of
0.7
mg
CN/
kg­
day
and
a
LOAEL
of
1.2
mg
CN/
kg­
day.
However,
this
study
is
limited
by
the
small
group
size,
the
lack
of
information
on
the
biological
significance
of
the
hormone
changes,
and
the
lack
of
thyroid
histopathology
data
that
would
confirm
that
cyanide
is
having
an
adverse,
rather
than
adaptive,
effect
on
the
thyroid
at
these
doses.
Kamalu
(
1993)
observed
histopathological
changes
in
kidney,
adrenal,
and
testis
of
dogs
that
received
cyanide
(
1.04
mg
CN/
kg­
day)
in
the
diet
for
14
weeks.
In
particular,
this
study
suggests
that
cyanide
may
be
a
male
reproductive
toxicant,
based
on
the
presence
of
abnormal
cells
and
sloughing
of
germ
cells
in
the
seminiferous
tubules
and
a
decreased
percentage
of
tubules
in
stage
8
of
the
spermatogenic
cycle.
However,
Kamalu
(
1993)
did
not
conduct
histopathology
on
the
CNS
or
thyroid
tissue
and
did
not
measure
thyroid
hormones.
Therefore,
it
is
not
possible
to
rule
out
the
CNS
and
thyroid
as
target
organs
based
on
this
study,
or
to
evaluate
the
relative
sensitivities
of
the
thyroid,
CNS,
and
male
reproductive
tract.
In
addition,
dogs
have
low
levels
of
rhodanese,
so
they
are
not
good
models
for
human
toxicity
(
ATSDR,
1997).
Male
reproductive
effects,
characterized
by
decreased
epididymis
and
testis
weights,
were
also
observed
in
rats
and
mice
exposed
to
cyanide
in
drinking
water
for
13
weeks
(
NTP,
1993).
The
NOAEL
was
4.5
mg
CN/
kg­
day
in
rats,
and
8.6
mg
CN/
kg­
day
in
mice.
This
study
did
not
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
28
Final
draft
observe
histopathological
changes
in
brain
or
thyroid
tissue,
but
did
not
measure
plasma
levels
of
thyroid
hormones
or
measure
thyroid
weight.
Although
evidence
of
thyroid
hyperplasia
would
be
needed
to
determine
that
a
given
dose
of
cyanide
is
adverse
to
the
thyroid,
it
is
possible
that
this
study
did
not
detect
early
signs
of
adaptive
effects
in
the
thyroid.

Long­
term
toxicity
data
for
thiocyanate
are
available
from
mice
(
Nagasawa
et
al.,
1980)

and
rats
(
Pyska,
1977;
Philbrick
et
al.,
1979;
Kanno
et
al.,
1990)
exposed
to
thiocyanate
via
the
diet
and
drinking
water.
No
data
on
the
effects
of
inhalation
or
dermal
exposure
were
located.

As
for
the
short­
term
studies,
no
subchronic
or
chronic
studies
were
located
that
meet
EPA
test
guidelines
(
including
serum
biochemistry
for
a
number
of
endpoints
and
histopathology
of
an
extensive
list
of
tissues
and
organs).
Nonetheless,
there
is
fairly
good
support
that
the
target
organ
(
the
thyroid)
has
been
identified,
and
a
number
of
studies
have
focused
on
effects
on
that
organ.
None
of
the
studies
that
evaluated
thyroid
endpoints
identified
a
NOAEL.
The
lowest
LOAEL
was
identified
by
Philbrick
et
al.
(
1979),
who
reported
a
statistically
significant
decrease
in
plasma
T4
and
increased
thyroid
weight
(
but
no
thyroid
histopathology)
in
rats
administered
98
mg
SCN/
kg­
day
in
diet
for
11.5
months;
plasma
T4
was
increased
at
this
dose
after
4
months
of
exposure.
Pyska
et
al.
(
1977)
also
reported
decreased
plasma
protein­
bound
iodine
(
a
measure
of
plasma
T3
and
T4)
in
rats
administered
100
mg
SCN/
kg­
day
for
approximately
10
weeks
in
drinking
water.
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
29
Final
draft
C.
Reproductive/
Developmental
Toxicity
Cyanogen
chloride.
No
studies
on
the
reproductive
or
developmental
toxicity
of
cyanogen
chloride
by
any
route
of
exposure
were
located
in
the
literature.
The
remainder
of
this
section
presents
the
data
available
on
metabolites
of
cyanogen
chloride.

Cyanide.
NTP
(
1993)
conducted
a
subchronic
bioassay
on
sodium
cyanide
administered
in
drinking
water
to
F344
rats
and
B6C3F1
mice.
Decreases
in
epididymis
weight,
testis
weight,

and
sperm
count
were
observed
at
12.5
mg
CN/
kg­
day
in
rats
(
NOAEL
of
4.5
mg
CN/
kg­
day)

and
24.4
mg
CN/
kg­
day
in
mice
(
NOAEL
of
8.6
mg
CN/
kg­
day).
Female
rats
treated
with
4.9
or
12.5
mg
CN/
kg­
day
had
altered
estrous
cycles,
but
the
authors
suggested
that
this
effect
may
not
have
been
chemical­
related,
in
the
absence
of
a
clear
dose­
response.
This
study
was
described
in
detail
in
Section
V.
B.
Kamalu
(
1993)
observed
histopathological
changes
in
the
testis
of
dogs
that
received
cyanide
(
1.04
mg
CN/
kg­
day)
in
the
diet
for
14
weeks.
Although
dogs
have
low
levels
of
rhodanese
and
are
not
good
models
for
human
cyanide
toxicity
(
ATSDR,
1997),
this
study
suggests
that
cyanide
can
be
a
male
reproductive
toxicant,
based
on
the
presence
of
abnormal
cells
and
sloughing
of
germ
cells
in
the
seminiferous
tubules
and
a
decreased
percentage
of
tubules
in
stage
8
of
the
spermatogenic
cycle.

In
the
only
available
study
that
evaluated
the
developmental
effects
of
cyanide
exposure,

Tewe
and
Maner
(
1981)
evaluated
the
effects
of
cyanide
in
the
diet
of
rats.
Female
rats
(
20/
group,
strain
not
specified)
were
offered
either
a
basal
diet
prepared
from
low­
HCN
cassava
meal
or
the
basal
diet
supplemented
with
500
ppm
of
potassium
cyanide
throughout
mating,
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
30
Final
draft
gestation,
and
lactation.
In
addition,
two
female
weanling
rats
per
litter
were
maintained
on
each
diet
for
an
additional
28
days.
Rats
receiving
the
basal
diet
alone
received
a
dose
of
1.2
mg
CN/
kg­
day
(
based
on
a
dietary
HCN
concentration
of
12
mg/
kg
and
an
average
food
consumption
across
female
rats
of
0.102
kg/
kg
body
weight).
Adult
rats
receiving
the
KCN
treatment
received
a
total
CN
dose
of
21.6
mg
CN/
kg­
day
(
including
the
1.2
from
the
basal
diet
and
20.4
mg
CN/

kgday
as
KCN).
For
the
weanling
rats,
the
corresponding
doses
were
approximately
1.9
mg
CN/

kgday
for
the
basal
diet
and
34.3
mg
CN/
kg­
day
for
the
KCN
diet,
based
on
an
average
food
factor
of
0.162
for
female
weanling
rats
(
U.
S.
EPA,
1988).
Supplementation
with
KCN
had
no
effect
on
body
weight
of
pregnant
rats,
food
consumption,
maternal
liver
or
kidney
weights,
litter
size,

birth
weight
of
pups,
or
pup
mortality.
In
the
weanling
rats,
the
high­
cyanide
diet
resulted
in
significant
decreases
in
food
consumption
and
growth
rate,
and
an
increase
in
the
ratio
of
food
consumption
to
body
weight
gain.
The
high­
cyanide
diet
also
resulted
in
significant
increase
in
serum
thiocyanate
in
both
dams
and
weanlings
compared
with
animals
on
the
basal
diet
alone.

However,
the
activity
of
rhodanese,
the
enzyme
that
metabolizes
cyanide
to
thiocyanate,
in
the
liver
and
kidney
was
comparable
in
all
groups.
A
LOAEL
of
34.3
mg
CN/
kg­
day
was
identified
in
this
study,
based
on
decreased
daily
weight
gain
in
weanlings;
the
corresponding
BMDL
was
15
mg
CN/
kg­
day.
However,
confidence
in
the
BMDL
is
limited,
because
only
one
positive
dose
was
tested,
and
so
no
information
was
available
on
the
shape
of
the
dose­
response
curve.

Thiocyanate.
Nagasawa
et
al.
(
1980)
exposed
female
8­
week­
old
SHN
(
18/
group)
or
5­
week­
old
GR/
A
(
32/
group)
mice
to
0%,
0.1%
or
0.3%
potassium
thiocyanate
in
the
drinking
water.
Using
an
average
water
consumption
of
0.27
L/
kg­
day,
this
corresponds
to
doses
of
0,

163,
and
488
mg
SCN/
kg­
day.
In
the
SHN
mice,
normal
mammary
development
was
significantly
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
31
Final
draft
decreased
after
exposure
to
the
high
dose
for
12
weeks,
based
on
a
staged
rating
of
end­
bud
and
lobulo­
alveolar
growth.
However,
no
effect
on
the
weight
of
the
pituitary
or
adrenals
or
ovarian
histology
was
observed.
In
the
GR/
A
mice,
exposure
for
5
weeks
prior
to
mating
and
then
for
4
additional
weeks
had
no
effect
on
fertility,
litter
size,
fetal
viability,
or
pup
weight.
In
addition,

maternal
pituitary
levels
of
prolactin
and
growth
hormone
were
unaffected
when
measured
on
lactation
day
4.
No
LOAEL
for
developmental
toxicity
was
determined
in
the
GR/
A
mice.
The
developmental
NOAEL
in
that
strain
was
488
mg
SCN/
kg­
day,
but
the
study
did
not
include
a
full
assessment
of
developmental
toxicity
endpoints.
The
effect
on
mammary
development
in
the
SHN
mice
could
be
considered
evidence
of
developmental
toxicity
of
thiocyanate.
However,
the
significance
of
this
finding
is
unclear,
since
the
strain
was
chosen
based
on
its
high
incidence
of
mammary
tumors.
In
addition,
the
effect
on
mammary
development
occurred
at
a
higher
dose
than
the
thyroid
effects
in
the
same
study
(
described
in
the
section
on
long­
term
exposure).
The
study
authors
attributed
the
inhibition
of
normal
mammary
development
(
as
well
as
the
inhibition
of
mammary
tumor
development,
described
in
the
section
on
carcinogenicity)
to
decreased
circulating
thyroid
hormones.

Pyska
(
1977)
exposed
3
week­
old
female
Wistar
rats
(
17
 
19/
group)
to
0.1%
potassium
thiocyanate
in
the
drinking
water
for
approximately
10
weeks
(
until
the
rats
were
3
months
old).

Controls
received
tap
water.
Water­
consumption
data
were
not
reported
for
this
phase
of
the
study.
Based
on
a
body
weight
of
0.14
kg
and
the
allometric
equation
of
U.
S.
EPA
(
1988)
for
calculating
water
consumption,
the
dose
can
be
estimated
as
100
mg/
kg­
day.
However,
the
actual
dose
may
have
been
lower,
in
light
of
the
lower
maternal
drinking
water
consumption
described
below.
Mammary
weight
and
DNA
content
(
which
is
a
measure
related
to
cell
number)
were
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
32
Final
draft
significantly
decreased
in
the
treated
rats,
indicating
that
the
thiocyanate
inhibited
mammary­
gland
development.
In
another
experiment,
female
rats
(
12
 
27/
group)
were
exposed
to
0,
0.1%,
0.3%,

or
0.5%
potassium
thiocyanate
in
the
drinking
water
during
pregnancy
and
14
days
of
lactation.

The
daily
intake
of
drinking
water
was
reported
as
20
 
30
mL.
Based
on
the
reported
maternal
body
weight
and
the
lower
drinking­
water
intake
(
as
more
conservative),
the
daily
doses
can
be
estimated
at
0,
52,
156,
and
260
mg
SCN/
kg­
day.
There
was
a
statistically
significant,

doserelated
decrease
in
plasma
protein­
bound
iodine
at
all
doses.
Maternal
mammary­
gland
dry
weight,
total
DNA,
and
RNA
content
were
also
significantly
decreased
at
all
doses,
indicating
depressed
mammary
growth.
The
authors
suggested
that
the
depressed
mammary
growth
was
associated
with
the
depressed
thyroid
activity.
There
was
also
a
marked
and
statistically
significant
decrease
compared
to
controls
in
maternal
body
weight
at
the
high
dose,
and
in
the
weight
of
14­
day
litters
at
the
mid
and
high
doses.
It
is
unclear
whether
the
effects
on
litter
weight
were
due
to
pre­
or
post­
natal
exposure
to
thiocyanate.
Based
on
thyroid
toxicity
and
inhibited
mammary­
gland
development,
the
maternal
LOAEL
was
52
mg/
kg­
day;
no
NOAEL
was
identified.
Based
on
decreased
litter
weight,
the
NOAEL
for
developmental
toxicity
was
52
mg
SCN/
kg­
day
and
the
LOAEL
was
156
mg
SCN/
kg­
day.
However,
the
study
did
not
evaluate
thyroid
effects
in
the
pups
or
other
standard
developmental
toxicity
endpoints.

Bala
et
al.
(
1996)
fed
groups
of
6
female
Wistar/
NIN
rats
a
semi­
synthetic
diet
sufficient
in
iodine
and
containing
0
or
25
mg
potassium
thiocyanate/
rat.
The
diet
was
provided
for
8
weeks
before
mating,
and
during
gestation
and
lactation.
Additional
groups
were
fed
the
control
diet
until
conception,
and
then
provided
the
thiocyanate
during
gestation
and
lactation,
or
during
lactation
only.
Based
on
the
reported
body
weight
of
139
g
after
8
weeks,
the
dose
can
be
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
33
Final
draft
estimated
as
108
mg
SCN/
kg­
day.
Increased
maternal
thyroid
weight
and
urinary
excretion
of
iodine,
and
decreased
serum
T4
were
reported
in
the
dams.
Body
weight
and
T3
levels
were
not
affected.
Pups
also
had
significantly
decreased
serum
T4
under
all
of
the
treatment
scenarios.

Weanling­
pup
body
weight
was
also
significantly
decreased
in
the
group
provided
thiocyanate
during
gestation
and
lactation,
but
not
prior
to
mating.
Other
markers
of
developmental
toxicity
were
not
assessed.
This
study
identifies
a
maternal
and
developmental
LOAEL
of
108
mg
SCN/
kg­
day,
based
on
thyroid
effects.

In
a
related
study
from
the
same
laboratory,
Raghunath
and
Bala
(
1998)
measured
the
effect
of
potassium
thiocyanate
on
T4
in
Wistar/
NIN
rats
fed
through
two
generations.
The
number
of
rats
exposed
was
not
reported,
although
it
appears
that
only
6­
8
pups
from
the
F1
and
F2
generations
were
evaluated.
Female
weanling
rats
were
fed
either
a
nutrient­
sufficient
caseinbased
semisynthetic
diet
(
control)
or
the
same
diet
with
added
potassium
thiocyanate.
The
authors
did
not
provide
the
concentration
of
the
added
KSCN
in
the
diet,
but
stated
that
the
treatment
animals
received
about
25
mg
KSCN/
rat/
day.
Using
a
body
weight
of
0.14
kg
(
based
on
the
data
from
Bala
et
al.,
1996),
the
daily
intake
can
be
estimated
at
about
108
mg
SCN/

kgday
After
eight
weeks
on
the
diet,
the
treated
female
rats
became
hypothyroidic,
were
mated
with
control
males,
and
continued
on
their
respective
diets
throughout
the
subsequent
gestation
and
lactation
periods.
The
females
from
the
F1
offspring
were
weaned
and
fed
their
respective
dam's
diet
for
eight
additional
weeks
and,
likewise,
mated
with
control
males
and
continued
through
to
gestation
and
lactation.
At
weaning,
the
F2
pups
were
assessed
for
thyroid
status.

Continued
feeding
of
KSCN
over
two
generations
had
no
effect
on
the
body
weights
of
F1
or
F2
pups
at
birth
or
at
weaning
as
compared
to
corresponding
controls.
Serum
T4
levels
were
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
34
Final
draft
significantly
decreased
in
F1
and
F2
pups
compared
to
their
respective
controls.
The
decrease
of
T4
levels
was
more
pronounced
in
the
F2
generation.
There
was,
however,
no
effect
on
pup
body
weight
or
brain
weight
in
the
F2
generation
(
the
only
generation
in
which
these
endpoints
were
assessed).
Other
reproductive
and
developmental
toxicity
endpoints
were
not
evaluated.
Overall,

the
single
dose
tested,
108
mg
SCN/
kg­
day,
was
a
maternal
and
developmental
LOAEL.

Kreutler
et
al.
(
1978)
administered
sodium
thiocyanate
in
drinking
water
at
0,
40,
80,
or
160
mg
SCN/
L
to
groups
of
4­
7
pregnant
rats
(
strain
not
reported,
but
source
was
Charles
River)

during
gestation
through
postpartum
day
10.
The
authors
reported
that
the
rats
drank
about
40
mL
water
daily,
but
did
not
report
the
body
weight.
Using
the
average
water
consumption
of
0.158
L/
kg­
day
for
female
rats
in
a
subchronic
study
(
calculated
from
U.
S.
EPA,
1988),
the
doses
can
be
estimated
as
0,
6.3,
12.6,
and
25.3
mg
SCN/
kg­
day.
The
rats
were
allowed
to
deliver,
and
the
litters
were
culled
to
6
pups
at
birth.
The
only
index
of
toxicity
evaluated
was
increased
thyroid
weight;
other
developmental
endpoints
were
not
evaluated.
In
the
dams,
thyroid
weights
(
relative
to
body
weight)
were
significantly
increased
at
all
doses
at
5
days
postpartum,
but
only
at
the
high
dose
at
10
days
postpartum.
However,
this
difference
may
be
an
artifact
of
the
small
sample
size,
since
the
control
relative
thyroid
weight
was
much
lower
at
day
5
than
at
day
10.
In
the
pups,
there
were
dose­
related
increases
in
thyroid
weights
that
were
statistically
significant
at
all
doses
on
day
5,
but
only
at
the
two
top
doses
on
day
10.
These
results
suggest
that
the
pup
is
more
sensitive
than
the
dam
to
effects
of
thiocyanate,
particularly
since
the
plasma­
thiocyanate
levels
were
much
lower
in
the
pups.
The
absence
of
an
evaluation
of
other
endpoints
of
thyroid
toxicity
(
e.
g.,
thyroid­
hormone
levels,
histopathology)
makes
it
difficult
to
determine
whether
the
increased
thyroid
weight
in
the
pups
was
adaptive
or
adverse.
Increased
thyroid
weight
can
be
an
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
35
Final
draft
adaptive
homeostatic
response
to
changes
in
thyroid­
hormone
levels,
and
can
be
followed
by
a
return
of
thyroid
hormones
to
basal
levels.
In
the
absence
of
data
on
other
thyroid
endpoints,
the
increase
in
thyroid
weight
at
the
low
dose
indicates
that
6.3
mg
SCN/
kg­
day
is
an
minimal
developmental
and
maternal
LOAEL.

Heydens
(
1985)
exposed
female
rats
(
number/
dose
and
strain
not
specified)
to
55
or
220
mg/
kg
of
thiocyanate
on
gestation
days
6
 
15
or
to
150
mg/
kg
of
thiocyanate
throughout
gestation
(
route
of
exposure
not
specified).
No
teratogenicity
was
observed,
but
postnatal
growth
and
development
were
reported
to
have
been
retarded.
Continued
exposure
throughout
the
period
of
lactation
did
not
result
in
substantially
greater
growth
retardation,
indicating
that
the
effects
observed
were
caused
primarily
during
gestation.
Limited
experimental
details
and
results
were
presented
in
this
report.
No
NOAEL
was
reported.
Based
on
the
information
provided,
the
LOAEL
for
this
study
was
55
mg
thiocyanate/
kg­
day,
based
on
developmental
retardation.

Summary
of
Reproductive/
Developmental
Toxicity
No
studies
on
the
reproductive
or
developmental
toxicity
of
cyanogen
chloride
by
any
route
of
exposure
were
located.
No
standard
multigeneration
or
developmental
toxicity
studies
of
cyanide
are
available.
Cyanide
appears
to
be
a
male
reproductive
toxicant
in
rats,
mice,
and
dogs
as
discussed
in
the
previous
section
(
NTP,
1993;
Kamalu,
1993).
Tewe
and
Maner
(
1981)
found
no
effects
on
litter
size,
birth
weight
of
pups,
or
pup
mortality
in
the
offspring
of
female
rats
receiving
cyanide
in
the
diet
throughout
mating,
gestation,
and
lactation,
although
weanling
body
weight
gain
was
decreased.
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
36
Final
draft
No
standard
multigeneration
reproduction
study
of
thiocyanate
by
any
route
was
located.

A
multigeneration
study
(
Raghunath
and
Bala,
1998)
was
conducted
in
rats
administered
108
mg
SCN/
kg­
day
in
feed,
and
decreased
serum
T4
was
observed
at
the
single
dose
tested,
with
a
somewhat
stronger
effect
in
the
F2
generation.
In
addition,
there
was
no
developmental
toxicity
study
that
included
morphological
evaluation
of
the
pups.
Two
studies
reported,
however,
that
mammary
gland
development
of
young
females
is
inhibited
at
doses
at
or
above
those
that
cause
thyroid
effects
(
Pyska,
1977;
Nagasawa
et
al.,
1980).
No
standard
developmental
toxicity
studies
were
identified,
although
Nagasawa
et
al.
(
1980)
found
no
effect
on
fertility,
litter
size,
fetal
viability,
or
pup
weight
when
mice
were
administered
thiocyanate
in
drinking
water
up
to
488
mg
SCN/
kg­
day.
Decreased
litter
weight
was
observed
in
the
offspring
of
rats
administered
approximately
156
or
260
mg
SCN/
kg­
day
in
drinking
water,
but
not
52
mg
SCN/
kg­
day
(
Pyska,

1977).
Several
studies
evaluated
thyroid
effects
in
pups
that
were
exposed
to
thiocyanate
during
gestation
and
lactation
(
Bala
et
al.,
1996;
Raghunath
and
Bala,
1998;
Kreutler
et
al.,
1978),
but
no
NOAEL
was
identified.
Kreutler
et
al.
(
1978)
included
the
lowest
doses,
testing
rats
down
to
6.3
mg
SCN/
kg­
day
in
drinking
water.
Unfortunately,
these
authors
only
evaluated
relative
thyroid
weight,
and
increases
in
thyroid
weight
may
be
adaptive
or
adverse,
depending
on
the
effects
on
thyroid
hormones
and
histopathology.
Using
the
most
conservative
interpretation,
the
low
dose
of
6.3
mg
SCN/
kg­
day
in
the
Kreutler
et
al.
(
1978)
study
can
be
considered
a
minimal
LOAEL.
The
next­
lowest
developmental
LOAEL
was
108
mg
SCN/
kg­
day,
identified
by
Bala
et
al.
(
1996)
and
Raghunath
and
Bala
(
1998),
based
on
decreased
serum
T4
in
pups.

In
general,
the
reproductive
and
developmental
database
for
cyanogen
chloride
and
its
metabolites
is
incomplete:
standard
2­
generation
reproductive
and
developmental
toxicity
studies
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
37
Final
draft
are
missing
for
all
three
chemicals.
Of
particular
concern
for
cyanide
is
the
fact
that
two
subchronic
studies
found
altered
epididymis
weights,
testis
weights,
and
sperm
counts
in
rats
and
altered
testis
weight
in
dogs.
Therefore,
a
significant
data
gap
is
a
reproductive
study
that
evaluates
male
reproductive
function.
Although
limited
data
suggest
that
neither
cyanide
nor
thiocyanate
affect
some
endpoints
evaluated
in
developmental
toxicity
studies,
such
as
litter
size,

pup
weights,
or
pup
viability,
none
of
the
studies
evaluated
the
full
spectrum
of
developmental
toxicity
endpoints,
particularly
morphological
evaluation
of
pups.
Thus,
a
significant
data
gap
is
the
lack
of
studies
that
evaluate
the
potential
of
cyanogen
chloride
or
its
metabolites
to
have
teratogenic
effects.
Thiocyanate
appears
to
alter
thyroid
function
in
pups
exposed
during
gestation
and
lactation,
including
altered
thyroid
weights
and
thyroid
hormone
levels.
However,

the
existing
studies
did
not
do
a
complete
analysis
of
thyroid
to
determine
if
the
effects
observed
were
adaptive
or
adverse.
In
addition,
decreased
T4
levels
in
mothers
and
fetuses/
neonates
has
been
associated
with
significant
neurological
deficit
in
children.
Therefore,
lack
of
neurodevelopmental
toxicity
studies
on
cyanogen
chloride
or
its
metabolites
also
represents
a
significant
data
gap.

D.
Mutagenicity
and
Genotoxicity
Cyanogen
chloride.
No
studies
regarding
the
mutagenicity
or
genotoxicity
of
cyanogen
chloride
were
located.

Cyanide.
The
limited
information
available
on
the
mutagenicity
of
cyanide
is
summarized
by
ATSDR
(
1997).
Potassium
cyanide
was
not
mutagenic
in
strains
TA82,
TA102,
TA98,
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
38
Final
draft
TA100,
TA1535,
TA1537,
and
TA1538
of
the
Salmonella
typhimurium
reverse
mutation
assay
with
or
without
metabolic
activation
(
De
Flora,
1981;
De
Flora
et
al.,
1984).
Sodium
cyanide
was
not
mutagenic
in
strains
TA97,
TA98,
TA100,
and
TA1535
with
or
without
metabolic
activation
(
NTP,
1993).
However,
a
positive
response
was
reported
for
hydrogen
cyanide
in
strain
TA100
without
metabolic
activation;
adding
metabolic
activation
reduced
the
magnitude
of
the
positive
response
to
40%
of
what
it
had
been
without
metabolic
activation
(
Kushi
et
al.,

1983).
Negative
results
were
also
obtained
in
the
DNA­
repair
test
in
Escherichia
coli
strains
WP67,
CM871,
and
WP2
(
De
Flora
et
al.,
1984)
and
in
a
test
for
inhibition
of
DNA
synthesis
in
HeLa
cells
(
Painter
and
Howard,
1982).

A
report
of
U.
S.
EPA's
Gene­
Tox
program
summarized
data
on
the
Arabidopsis
plant
assay
for
chemical
mutagens
(
Redei,
1982).
This
assay
allows
the
screening
of
thousands
of
gene
loci
for
recessive
forward
mutations.
This
summary
report
cited
an
earlier
unpublished
study
by
Müller
(
1965),
in
which
potassium
cyanide
was
negative
up
to
10
mM.
Further
details
were
not
provided,
but
the
studies
presented
met
some
(
unspecified)
criteria
for
acceptability.

Kihlman
(
1957)
conducted
a
chromosome
aberration
assay
with
potassium
cyanide
using
the
Vicia
faba,
a
broad
bean
plant.
Exposure
was
to
potassium
cyanide
in
air.
Both
exchanges
and
isolocus
breaks
were
observed,
with
the
concentration
in
air
being
more
important
than
the
exposure
duration.
Production
of
aberrations
increased
as
the
oxygen
concentration
increased
from
0
to
100%.
Noting
that
cyanide
inhibits
peroxidase
and
catalase,
other
authors
have
hypothesized
that
cyanide­
induced
chromosome
aberrations
result
from
the
accumulation
of
hydrogen
peroxide.
Noting,
however,
that
peroxide
alone
does
not
cause
chromosome
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
39
Final
draft
aberrations
in
the
Vicia
test
system,
Kihlman
(
1957)
proposed
that
cyanide
acts
by
forming
a
complex
with
iron
or
other
heavy
metals
bound
to
chromosomes,
and
that
the
metals
act
to
mediate
redox
reactions.

Overall,
cyanide
has
been
negative
in
bacterial
mutagenicity
studies
with
and
without
S9
activation
(
De
Flora,
1981;
De
Flora
et
al.,
1984;
NTP,
1993),
although
a
positive
result
was
obtained
in
strain
TA100
with
and
without
S9
activation
in
one
study
(
Kushi
et
al.,
1983).

Mammalian
gene
mutation
studies
of
cyanide
are
not
available,
but
a
negative
result
was
obtained
in
a
study
of
Arabidopsis
(
Müller,
1965,
as
cited
by
Redei,
1982).
Standard
chromosome
aberration
assays
of
cyanide
are
also
not
available.
Potassium
cyanide
in
air
caused
chromosome
aberrations
in
the
broad
bean
plant,
apparently
by
a
mechanism
related
to
the
production
of
reactive
oxygen
species
(
Kihlman,
1957).
Cyanide
was
negative
in
assays
for
the
production
of
DNA
damage
and
repair
(
De
Flora
et
al.,
1984;
Painter
and
Howard,
1982).

Thiocyanate.
The
data
on
the
genotoxicity
of
thiocyanate
are
very
limited.
Marginal
results
were
reported
in
the
S.
typhimurium
mutagenicity
assay
(
Kier,
1988,
as
reported
by
Rosenkranz
and
Klopman,
1990).
Further
study
details
were
not
available.
No
other
standard
gene
mutation
or
chromosome
aberration
assays
were
located.
Rosenkranz
and
Klopman
(
1990)

reported
that
potassium
thiocyanate
does
not
have
any
structural
alerts
for
genotoxicity.
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
40
Final
draft
Summary
of
Genotoxicity
No
data
are
available
on
the
genotoxicity
of
cyanogen
chloride.
Although
the
data
for
some
known
or
potential
metabolites
of
cyanogen
chloride
are
limited,
the
available
data
suggest,

overall,
that
none
of
the
metabolites
is
genotoxic.
Overall,
cyanide
has
been
negative
in
bacterial
mutagenicity
assays
(
De
Flora,
1981;
De
Flora
et
al.,
1984;
NTP,
1993)
and
assays
of
DNA
damage
and
repair
(
De
Flora
et
al.,
1984;
Painter
and
Howard,
1982),
although
a
positive
result
was
obtained
in
one
strain
of
Salmonella
with
and
without
S9
activation
(
Kushi
et
al.,
1983).
No
assays
of
mammalian
gene
mutation
or
chromosome
aberration
induction
by
cyanide
are
available.

Genotoxicity
data
on
thiocyanate
are
limited
to
marginal
results
in
a
S.
typhimurium
mutagenicity
assay
(
Kier,
1988,
as
reported
by
Rosenkranz
and
Klopman,
1990).
Potassium
thiocyanate
does
not
have
any
structural
alerts
for
genotoxicity
(
Rosenkranz
and
Klopman,
1990).

E.
Carcinogenicity
Cyanogen
chloride.
No
carcinogenicity
studies
of
cyanogen
chloride
via
any
route
were
located.

Cyanide.
No
carcinogenicity
studies
of
cyanide
via
any
route
of
exposure
were
located.

Thiocyanate.
In
a
cancer
bioassay,
Lijinsky
and
Reuber
(
1982)
fed
male
Fischer
rats
(
20/
group)
a
powdered
diet
with
or
without
sodium
thiocyanate
at
800
mg/
kg
for
130
weeks.

Using
a
food
factor
of
0.079
for
a
chronic
study
in
male
Fischer
rats
(
U.
S.
EPA,
1988),
this
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
41
Final
draft
corresponds
to
doses
of
0
and
45
mg
SCN/
kg­
day.
The
purpose
of
the
study
was
to
examine
the
effect
of
in
vivo
transnitrosation
of
nitrosamines.
SCN
was
used
as
a
catalyst
of
nitrosation
when
administered
with
other
nitroso
compounds;
the
group
receiving
SCN
alone
was
essentially
considered
a
control
group
by
the
study
authors.
Therefore,
this
study
was
not
conducted
with
the
intent
of
evaluating
SCN
carcinogenicity
and
the
reporting
of
SCN
health
effects
is
limited.

All
animals
were
necropsied
and
the
major
organs
and
all
lesions
were
fixed
for
histological
examination.
Food
consumption
was
not
reported
by
the
authors,
nor
was
the
composition
of
the
diet.
Survival
of
the
rats
given
SCN
was
comparable
to
the
untreated
control
at
all
time
points.

Survival
at
1
year
was
100%
in
both
groups;
survival
at
100
weeks
(
approximately
2
years)
was
65%
in
untreated
controls
compared
with
85%
in
SCN
treated
animals.
By
week
120,
survival
was
45%
in
both
groups.
The
number
of
hepatic
tumors
was
elevated
in
the
SCN­
treated
group
(
5/
20)
as
compared
to
the
control
group
(
0/
20).
There
were
no
differences
in
tumor
incidences
between
SCN­
treated
and
control
rats
at
all
other
sites
examined.
No
other
information
was
presented
regarding
the
type
of
tumor,
the
time
of
first
tumor
appearance,
or
the
presence
of
any
nonneoplastic
lesions.
This
study
is
limited
by
the
small
size
of
the
dose
groups,
and
the
incomplete
evaluation
of
SCN
carcinogenicity.
It
is
unclear
whether
a
sufficiently
high
dose
was
tested,
although
higher
doses
were
tested
in
the
follow­
up
study
described
in
the
next
paragraph.

Nonetheless,
it
is
of
interest
that
the
number
of
thyroid
tumors
(
2/
20)
was
the
same
in
the
exposed
group
as
in
the
controls.

In
a
follow­
up
study,
Lijinsky
and
Kovatch
(
1989)
exposed
Fischer
344
rats
(
20­

24/
sex/
dose)
to
0%
or
0.32%
sodium
thiocyanate
in
drinking
water
5
days/
week
for
112
weeks.

The
study
continued
until
all
of
the
animals
died,
or
until
130
weeks.
The
study
authors
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
42
Final
draft
determined
that
the
total
dose
of
sodium
thiocyanate
ingested
was
approximately
1
mole/
kg
in
males
and
1.7
mole/
kg
in
females.
The
authors
estimated
that
this
was
roughly
equivalent
to
a
daily
dose
of
250
mg/
kg
of
sodium
thiocyanate
in
females
(
147
mg/
kg
of
sodium
thiocyanate
in
males,
by
extrapolation).
Thus,
the
thiocyanate
doses
were
75
mg
SCN/
kg­
day
for
males
and
128
mg
SCN/
kg­
day
for
females,
after
adjusting
for
dosing
5/
7
days/
week.
No
increase
in
mortality,

noticeably
adverse
effects,
or
tumor
formation
was
reported
in
the
treated
rats.
It
is
unclear
from
the
report
whether
the
incidence
of
any
nonneoplastic
lesions
was
increased
in
treated
rats.
The
increase
in
liver
tumors
seen
by
Lijinsky
and
Reuber
(
1982)
was
not
confirmed.
However,
the
incidence
of
thyroid
tumors
doubled
for
both
treated
males
(
3/
20
or
15%)
and
females
(
2/
20
or
10%)
compared
to
controls
(
2/
24
or
8%
for
males,
1/
24
or
4%
for
females).
The
study
authors
did
not
conduct
statistical
analysis
of
thyroid
tumor
incidence;
EPA
conducted
a
Fisher's
Exact
test,
which
indicated
that
the
increase
was
not
statistically
significant.
No
additional
information
is
provided
on
the
type
of
tumors,
the
time
of
first
tumor
appearance,
or
other
nonneoplastic
lesions
associated
with
thyroid
toxicity.
This
study
is
limited
by
the
small
sample
size
and
the
incomplete
reporting
of
information
needed
to
completely
assess
the
carcinogenicity
of
SCN.

In
a
short­
term
test
of
carcinogenicity,
Nagasawa
et
al.
(
1980)
exposed
female
SHN
mice
(
18/
group)
to
0.1%
or
0.3%
potassium
thiocyanate
in
the
drinking
water
for
12
weeks.
Controls
received
tap
water.
Using
the
average
water
consumption
of
0.27
L/
kg­
day
across
mouse
strains
(
U.
S.
EPA,
1988),
this
corresponds
to
doses
of
0,
163,
and
488
mg/
kg­
day.
The
strain
was
chosen
due
to
its
high
incidence
of
mammary
tumors,
but
thiocyanate
did
not
increase
the
incidence
of
mammary
tumors.
Instead,
there
was
a
dose­
related
decrease
in
mammary
tumor
incidence
and
in
the
incidence
of
mammary
hyperplastic
alveolar
nodules.
Significantly
decreased
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
43
Final
draft
T3
(
at
the
high
dose)
and
T4
(
at
both
doses)
indicated
that
sufficiently­
high
doses
were
tested.
In
a
related
study,
female
inbred
GR/
A
mice
(
19­
22/
group)
received
the
same
doses
for
5
weeks
prior
to
mating
and
during
gestation.
There
were
dose­
related
decreases
in
the
incidence
and
size
of
pregnancy­
dependent
mammary
tumors,
although
the
effect
on
tumor
size
was
not
statistically
significant.
The
authors
attributed
the
inhibition
of
mammary
tumor
development
by
thiocyanate,

as
well
as
the
inhibition
of
normal
mammary
development
(
described
above
in
the
section
on
reproductive/
developmental
toxicity)
to
decreased
thyroid
hormones,
since
body
weight
and
weights
of
the
pituitary
and
adrenals
were
not
affected.
Other
tumor
endpoints
were
not
evaluated.

Summary
of
Carcinogenicity
There
are
no
cancer
bioassays
of
cyanogen
chloride
or
cyanide.
There
are
no
wellconducted
standard
cancer
bioassays
of
thiocyanate.
Two
oral
carcinogenicity
studies
in
rats
were
conducted
in
the
same
laboratory
(
Lijinsky
and
Reuber,
1982;
Lijinsky
and
Kovatch,
1989).

The
only
effect
in
the
first
study
was
an
increase
in
liver
tumors,
and
this
was
not
confirmed
at
the
higher
dose
tested
in
the
second
study.
The
second
study
suggested
higher
doses
of
SCN
may
be
associated
with
increased
incidence
of
thyroid
tumors.
Although
the
increase
of
thyroid
tumors
was
not
statistically
significant,
the
observation
of
thyroid
tumors
in
consistent
with
what
is
known
about
SCN
mode
of
action
on
the
thyroid.
However,
these
studies
suffer
from
a
number
of
limitations.
Only
a
single
dose
was
tested
in
each
study,
limited
numbers
of
animals
were
tested
(
20/
group
first
study;
20/
sex/
group
second
study),
and
the
studies
did
not
provide
a
complete
report
of
the
information
needed
to
adequately
assess
SCN
carcinogenicity.
Drinking
Water
Criteria
Document
for
Cyanogen
Chloride
and
Potential
Metabolites
EPA/
OW/
OST/
HECD
V­
44
Final
draft
Based
on
these
considerations,
cyanogen
chloride,
cyanide,
and
thiocyanate
would
all
be
classified
as
Group
D,
Not
Classifiable
as
to
Human
Carcinogenicity,
using
the
U.
S.
EPA
(
1986)

guidelines
for
carcinogen
risk
assessment.
Using
the
U.
S.
EPA
(
1999)
Draft
Guidelines
for
Carcinogen
Risk
Assessment,
the
data
are
inadequate
for
an
assessment
of
the
human
carcinogenic
potential
of
these
compounds.
