inc.

M
E
M
O
R
A
N
D
U
M
TO:
Lynn
Zipf
cc:
110476.1000.020
FROM:
Kathy
Coon,
Jim
Buchert
DATE:
Toxic
Weighting
Factors
for
Sodium
Nitrite
and
Sodium
Cyanide
SUBJECT:
December
16,
2003
At
your
request,
Versar
has
reviewed
the
Toxic
Weighting
Factors
(
TWFs)
for
sodium
nitrite
and
sodium
cyanide.
The
following
information
was
determined.

Sodium
Nitrite
Toxicity
information
for
sodium
nitrite
was
last
updated
in
the
Toxics
Data
Base
in
October
1999.

The
freshwater
acute
toxic
effect
level
of
150

g/
L
is
the
lowest
reported
96­
hour
LC50
for
the
rainbow
trout.
The
value
was
obtained
from
EPA's
ASTER/
AQUIRE
system
and
was
verified
by
a
current
(
December
2003)
ASTER/
AQUIRE
retrieval
performed
by
EPA's
National
Health
and
Environmental
Effects
Research
Laboratory
in
Duluth.
A
freshwater
chronic
toxicity
value
of
15

g/
L
was
estimated
based
on
an
acute:
chronic
ratio
of
10:
1.
Selection
of
these
values
follows
a
hierarchy
established
by
EPA/
Versar.
Investigation
of
other
literature
sources
(
e.
g.,
Material
Safety
Data
Sheets,
EPA
"
Gold
Book")
support
the
use
of
these
values.
However,
it
should
be
noted
that
the
toxicity
of
nitrite
is
pH
dependent
and
is
dependent
in
varying
degrees
upon
many
of
the
anions
that
are
commonly
found
in
natural
aquatic
environments.

In
addition,
EPA's
"
Gold
Book"
states
that
"
Recognizing
that
concentrations
of
nitrate
or
nitrite
that
would
exhibit
toxic
effects
on
warm
or
cold
water
fish
would
rarely
occur
in
nature,
restrictive
criteria
are
not
recommended."

Sodium
Cyanide
Toxicity
information
for
sodium
cyanide
has
not
been
updated
since
at
least
1993.
The
freshwater
acute
toxic
effect
level
of
150

g/
L
is
a
96­
hour
LC50
for
the
bluegill.
The
value
was
obtained
from
a
1973
document:
"
Toxicity
of
Power
Plant
Chemicals
to
Aquatic
Life."
A
freshwater
chronic
toxicity
value
of
15

g/
L
was
estimated
based
on
an
acute:
chronic
ratio
of
10:
1.
A
current
(
December
2003)

ASTER/
AQUIRE
retrieval
performed
by
EPA
had
a
lowest
reported
96­
hour
LC50
of
156

g/
L.
Further
investigation
revealed
values
for
freshwater
fish
ranging
from
52
to
350

g/
L.
These
values
are
based
on
the
fact
that
in
aqueous
solutions,
the
cyanide
radical
from
simple
alkali
cyanides
such
as
sodium
cyanide
hydrolyze
to
form
free
cyanide.
Applying
the
acute:
chronic
ratio
of
10:
1
results
in
estimated
chronic
toxicity
values
of
5.2
to
35.0

g/
L.
EPA's
published
recommended
national
water
quality
criteria
for
free
cyanide
are
22

g/
L
(
freshwater
acute)
and
5.2

g/
L
(
freshwater
chronic).
Based
on
these
findings,
Versar
recommends
using
values
of
22

g/
L
(
freshwater
acute)
and
5.2

g/
L
(
freshwater
chronic)
for
sodium
cyanide.
Using
a
freshwater
chronic
value
of
5.2

g/
L
for
sodium
cyanide
yields
a
TWF
of
1.1,
compared
to
the
TWF
of
0.37
for
sodium
nitrite.

Please
contact
us
if
you
have
any
comments
or
questions.
