Page
1
of
9
UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON
D.
C.,
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
PC
Code:
056502
DP
Barcode:
D328772
Date:
April
26,
2006
MEMORANDUM
SUBJECT:
Synopsis
of
Pentachloronitrobenzene
Environmental
Loading
and
Ecological
Risk
TO:
Jill
Bloom,
Chemical
Review
Manager
Special
Review
and
Reregistration
Division
(
7508C)
Office
of
Pesticide
Programs
FROM:
Thomas
Steeger,
Ph.
D.,
Senior
Scientist
Cheryl
A.
Sutton,
Ph.
D.,
Environmental
Scientist
R.
David
Jones,
Ph.
D.,
Senior
Agronomist
Environmental
Risk
Branch
IV
Environmental
Fate
and
Effects
Division
(
7507C)
Office
Pesticide
Programs
APPROVED
BY:
Elizabeth
Behl,
Branch
Chief
Environmental
Risk
Branch
IV
Environmental
Fate
and
Effects
Division
(
7507C)
Office
Pesticide
Programs
Given
the
complex
nature
of
the
pentachloronitrobenzene
(
PCNB)
ecological
risk
assessment,
and
the
associated
need
to
examine
the
compound's
persistence
and
bioaccumulation
to
evaluate
potential
ecological
risks,
summarized
below
is
a
synopsis
of
the
assessment
and
the
significant
features
of
the
analyses.
This
summary
is
based
on
the
original
(
DP
Barcode
D291276)
and
revised
(
DP
Barcode
D319590)
environmental
fate
and
ecological
risk
assessment.

EXECUTIVE
SUMMARY
OF
PCNB
ENVIRONMENTAL
RISK
PCNB
is
a
contact
fungicide
used
on
a
broad
range
of
crops
as
both
a
soil
and
seed
treatment
and
foliar
application.
The
ecological
risk
assessment
focused
on
five
major
uses,
i.
e.,
turf,
peanuts,
cole
crops,
potatoes
and
cotton
which
account
for
over
86%
of
PCNB
uses
nationally.
Turf
and
cotton
combined
account
for
76%
of
the
total
pounds
of
active
ingredient
applied
domestically,
with
potatoes
accounting
for
an
additional
9.9%.

PCNB
and
its
degradates
have
persistence
and
toxicity
properties
that
are
consistent
with
national
and
international
criteria
for
identifying
persistence,
bioaccumulative
toxicants
(
PBTs).
The
compound's
Page
2
of
9
ability
to
bioconcentrate
in
fish
and
plants
from
water
only
exposures
(
approximately
1000
to
3000X)
meets
some
US
criteria
for
bioconcentration,
but
do
not
approach
those
of
DDT
(
42,000X)
or
dicofol
(
17,500X),
for
example.

Field
data
demonstrate
that
there
are
sufficient
PCNB
residues
to
affect
rotational
crops
two
years
after
the
chemical
has
been
applied.
Field
data
also
demonstrate
that
significant
quantities
of
PCNB
can
volatilize
from
the
field
and
will
undergo
long­
range
atmospheric
transport.
PCNB
residues
in
most
soils
will
partition
to
organic
matter
in
the
soil
and
move
to
surface
water
through
erosion.
PCNB
in
aquatic
environments
is
expected
to
be
associated
with
benthic
sediments.
The
chemical's
persistence
and
albeit
uncertain
potential
to
bioconcentrate
makes
it
logical
to
anticipate
that
the
aquatic
food
chain
is
a
reasonable
mechanism
for
PCNB
to
accumulate
at
higher
concentrations
with
increasing
levels
of
an
aquatic
food
chain
(
e.
g.,
water/
sediment
to
invertebrates/
algae
to
invertebrate/
algae
eating
fish
to
predatory
fish
to
fish
eating
birds
or
mammals).
Terrestrial
animals
dependent
on
the
aquatic
environment
as
a
source
of
food
can
potentially
be
exposed
to
PCNB
residues
at
levels
that
exceed
chronic
no­
observed
effect
concentrations
by
several
orders
of
magnitude.
There
are
uncertainties
in
estimating
PCNB's
bioaccumulation
potential;
however,
moderate
estimates
of
PCNB
accumulation
result
in
projected
fish
residues
that
could
result
in
chronic
reproductive
and
growth
effects
in
aquatic
and
terrestrial
animals.
Even
without
taking
bioaccumulation
into
account,
acute
and
chronic
risk
levels
of
concern
(
LOCs)
are
exceeded
for
aquatic
animals
and
chronic
risk
LOCs
are
exceeded
for
terrestrial
organisms.
To
the
extent
that
bioaccumulation
does
occur,
RQ
values
may
underestimate
risk,
which
could
potentially
increase
by
many
orders
of
magnitude.

The
salient
aspects
of
the
screening
level
and
final
ecological
risk
characterizations
are
further
highlighted
below.

SCREENING­
LEVEL
PCNB
ECOLOGICAL
RISK
ASSESSMENT
As
discussed
in
the
environmental
fate
and
ecological
risk
assessment
of
PCNB
(
DP
Barcode
D291276)
and
in
the
revised
assessment
(
DP
Barcode
D319590),
EPA
used
models
and
limited
available
monitoring
data
to
estimate
concentrations
of
PCNB
in
surface
and
ground
water.
EPA's
standard
screening­
level
approach
to
estimating
ecological
risk
is
to
compare
environmental
exposure
concentrations
to
toxic
effect
thresholds
established
in
toxicity
studies.
Although
acute
and
chronic
risk
quotients
exceed
levels
of
concern
for
many
nontarget
organisms
(
Table
1),
the
magnitude
of
the
exceedances
is
relatively
low
compared
to
other
pesticides.
As
indicated
in
the
subsequent
sections
of
this
memorandum,
the
screening
approach
for
assessing
risks
of
pesticides
to
aquatic
life
are
based
on
estimated
water
concentrations
and
does
not
consider
dietary
routes
of
exposure.
As
the
persistence
and
bioaccumulation
potential
of
a
pesticide
increases,
it
is
the
increasingly
likely
that
uptake
of
the
compound
through
the
food
is
a
significant
route
of
exposure.
To
the
extent
that
dietary
exposure
is
not
quantified
in
these
situations,
the
overall
risk
potential
is
underestimated.
In
a
similar
fashion,
chronic
risks
to
fish­
eating
wildlife
from
pesticides
that
are
persistent
and
bioaccumulative
will
typically
be
underestimated,
using
the
screening
approach
only,
because
accumulation
of
the
pesticides
in
the
aquatic
food
chain
is
not
quantified.

Table
1.
Summary
of
acute
and
chronic
risk
quotient
ranges
for
non­
target
organisms
following
unincorporated
application
of
pentachloronitrobenzene
to
agricultural
sites
(
cabbage,
peanuts,
cotton).

Taxa
Acute
Level
of
concern
Chronic
Level
of
concern
Freshwater
Fish
0.08
 
0.36
0.5
0.15
­
0.73
1.0
Page
3
of
9
Freshwater
Invertebrates
0.01
 
0.05
0.5
0.17
­
0.85
1.0
Estuarine/
marine
Fish
<
0.01
0.5
No
data
1.0
Estuarine/
marine
Invertebrates
0.68
 
3.0
0.5
No
data
1.0
Birds
<
0.01
0.5
0.04
 
9.0
1.0
Mammals
0.01
 
0.46
0.5
65
 
1045
(
dietary­
based)*
54
 
8712
(
dose­
based)*
1.0
Plants
No
data
1.0
Not
Estimated
*
revised
dietary
and
dose­
based
chronic
RQ
values
based
on
NOAEC=
1.2
ppm
for
decreased
pup
growth.

FINAL
PCNB
ECOLOGICAL
RISK
ASSESSMENT
Conceptual
Model
for
the
PCNB
Risk
Assessment
PCNB
is
a
persistent,
moderately
volatile
chemical
that
is
not
likely
to
be
very
mobile
in
most
soils,
given
the
chemical's
tendency
to
sorb
to
organic
matter.
However,
on
sandy
soils
low
in
organic
matter,
PCNB
may
leach
to
groundwater
and
can
also
move
to
surface
waters
in
runoff
or
sedimentbound
residues
and
through
spray
drift
(
particularly
for
foliar
applications
such
as
to
turf).
Consistent
with
other
chemicals
with
moderate
to
high
volatility,
PCNB
can
also
move
to
areas
distant
from
use
sites
via
long­
range
atmospheric
transport.
PCNB
and
its
major
degradates
(
pentachloroaniline,
pentachlorothioanisole,
pentachlorothioanisole
sulfoxide,
pentachlorothioanisole
sulfone,
pentachlorophenol
and
pentachlorobenzene)
are
likely
to
be
persistent
in
the
environment.

Figure
1
depicts
the
conceptual
model
for
potential
movement
(
environmental
loading)
of
PCNB
into
the
atmosphere
and
surface
waters
following
non­
incorporated
agricultural
applications.
PCNB
and
its
degradates
have
been
found
in
rotational
crops
two
years
after
it
was
applied,
indicating
that
soilincorporated
uses
may
reduce
movement
to
water
bodies.
PCNB
that
volatilizes
and
moves
into
the
atmosphere
is
not
expected
to
degrade.
PCNB
that
moves
into
surface
waters
via
spraydrift
and
erosion
is
likely
to
partition
to
the
sediment.
Page
4
of
9
Evaluating
Exposure
and
Effects
for
PCNB:
Integrating
Persistence,
Bioaccumulation
and
Toxicity
Some
chemicals
that
are
highly
persistent
and
toxic
can
bioaccumulate
in
the
environment,
and
depending
on
their
toxicological
characteristics,
can
cause
significant
long­
term
adverse
effects.
While
PCNB
shares
some
of
these
characteristics,
there
is
some
uncertainty
regarding
the
extent
to
which
it
meets
national
and
international
standards
as
a
PBT
material.
The
extent
to
which
PCNB
is
persistent
and
bioaccumulative
and
the
extent
to
which
it
is
subject
to
long
range
transport
after
volatilization
influence
its
environmental
loading.
The
extent
to
which
PCNB
is
persistent
and
can
bioaccumulate
markedly
change
estimates
of
ecological
risk.
While
the
screening­
level
ecological
risk
assessment
of
PCNB
identifies
acute
and
chronic
risks
to
aquatic
animals
and
chronic
risk
to
terrestrial
animals,
these
estimates
are
based
on
exposure
through
the
water
column
only,
i.
e.,
uptake
through
the
gills
of
fish
was
assessed,
but
the
potential
risk
due
to
uptake
of
PCNB
through
the
diet
was
not
evaluated.
For
both
aquatic
and
terrestrial
animals
that
depend
on
the
aquatic
food
chain
for
their
diet,
the
extent
to
which
PCNB
accumulates
in
the
food
chain,
will
increase
their
aggregate
exposure
compared
to
a
`
water
only'
exposure
assumption
and
as
a
result
estimated
risks
would
likely
increase.

PBT
Characteristics
Multiple
national
and
international
criteria
have
been
reported
for
categorization
of
PBT
chemicals.
PCNB
meets
national
and
international
PBT
criteria
for
being
both
persistent
and
toxic
(
Table
2).
Figure
1.
Movement
of
pentachloronitrobenzene
into
the
atmosphere
and
surface
waters
and
its
eventual
bioaccumulation
in
food
chains
following
unincorporated
applications
to
agricultural
sites.
PCNB
is
transported
from
agricultural
sources
primarily
via
soil
erosion,
spray
drift,
and
runoff
PCNB
is
expected
to
accumulate
in
streambed
sediments
and
in
tissues
of
benthic
organisms
­

Concentrations
increase
in
predatory
animals
through
bioaccumulation,
causes
reproductive
and
growth
effects
P
C
N
B
PCNB
Page
5
of
9
Table
2.
Summary
of
whether
PCNB
meets
national
and
international
criteria*
for
persistence,
bioaccumulation
(
as
measured
by
bioconcentration
potential)
and
toxicity.

National/
International
Agency
or
Convention
Do
Persistence
Data
Meet
Thresholds?
Do
Bioconcentration
data
Meet
Threshold?
Do
Toxicity
Data
Meet
Threshold?

U.
S.
EPA
Office
of
Environmental
Information:
Yes,
all
media*
Yes
Yes
UNECE
(
United
Nations
Economic
Commission
for
Europe)
Convention
on
Long­
Range
Transboundary
Air
Pollution
(
LRTAP).
Yes,
all
media*
No
Yes
UNEP
POPs/
CEG
(
United
Nations
Environment
Program
Persistent
Organic
Pollutants
Criteria
Expert
Group)
Framework
(
Stockholm
Convention).
Yes,
all
media*
No
Yes
Environment
Canada
Toxic
Substances
Management
Policy.
Yes,
all
media*
Possible
data
would
show
short
half­
life
in
sediment.
No
Yes
International
Council
of
Chemical
Associations.
Yes,
all
media*
No
Yes
*(
http://
www.
unece.
org/
env/
lrtap/)
Page
6
of
9
 
Persistence
According
to
the
U.
S.
EPA's
Office
of
Environmental
Information
(
OEI),
the
criterion
(
http://
www.
epa.
gov/
fedrgstr/
EPA­
TOX/
1999/
November/
Day­
04/
t28888.
htm)
used
for
determining
whether
a
compound
is
persistent
is
if
it
has
a
soil
half­
life
greater
than
two
months
(
60
days);
the
United
Nations
Economic
Commission
for
Europe
Convention
on
Long­
Range
Transboundary
Air
Pollution
(
UNECE
LRTAP)
criteria
for
persistence
is
a
half­
life
greater
than
2
months
in
water,
greater
than
6
months
in
soil
or
sediment
or
otherwise
sufficiently
persistent
to
be
of
concern.
The
United
Nations
Environment
Program's
Persistent
Organic
Pollutants
Criteria
Expert
Group
(
UNEP
POP
CEG
)
defines
persistent
as
a
half­
life
greater
than
2
months
in
water;
greater
than
2
or
6
months
in
soil
or
sediment,
or
other
evidence
that
substance
is
sufficiently
persistent
to
be
of
concern.
Environment
Canada
defines
persistent
as
a
half­
life
of
2
days
air,
6
months
in
water/
soil
and
1
year
in
sediment.
The
International
Council
of
Chemical
Associations
(
ICCA)
defines
persistent
as
a
half­
life
6
months
in
water,
1
year
in
soil/
sediment,
or
5
days
air.
PCNB
meets
these
criteria
with
aerobic
soil
metabolism
half­
life
of
189
days.
Half­
lives
up
to
1,052
days
for
all
PCNB
degradates
have
also
been
reported.
Field
data
demonstrates
in
some
settings
that
PCNB
residues
can
be
found
in
rotational
crops
two
years
after
PCNB
application.
The
persistence
of
PCNB
in
the
environment
readily
meets
the
national
and
internal
criteria.

 
Bioconcentration
The
OEI
criterion
is
a
bioconcentration
factor
(
BCF)
greater
than
1000X;
the
UNECE
LRTAP
and
Environment
Canada
criterion
for
bioconcentration
is
a
BCF
greater
than
5000
or
log
octanol­
water
partition
coefficient
(
log
Kow)
of
greater
than
5.
The
UNEP's
POP
CEG
defines
bioaccumulative
as
a
BCF
greater
than
5000
or
log
Kow
greater
than
5
or
evidence
that
a
substance
with
a
significantly
lower
BCF
is
of
concern
(
e.
g.,
due
to
high
toxicity/
ecotoxicity
or
monitoring
data
in
biota
indicating
sufficient
bioaccumulation
to
be
of
concern).
The
ICCA
defines
bioaccumulative
as
a
BCF
of
5,000
or
log
Kow
between
5
and
7.5
and
the
chemical
is
not
metabolized.
PCNB
meets
OEI
criterion
with
bioconcentration
factors
in
whole
fish
of
1,100X
and
in
viscera
of
1,800X.
Higher
BCF
values
for
viscera
suggest
that
the
compound
is
readily
partitioning
into
lipids.
International
standards
for
bioconcentration
typically
require
a
BCF
of
greater
than
5,000X.
PCNB's
ability
to
bioconcentrate
does
not
approach
those
of
DDT
(
42,000X)
or
dicofol
(
17,500X).
For
example.
PCNB
has
demonstrated
a
propensity
for
bioconcentration
in
aquatic
plants
(
algae)
with
BCF
factors
as
high
as
3,100X
based
on
wet
weight.
Thus,
depending
on
which
set
of
criteria
are
used,
PCNB
may
or
not
meet
the
thresholds
for
bioaccumulation
potential.

 
Toxicity
The
OEI
criterion
for
toxicity
is
to
defer
to
best
professional
judgment
while
international
standards
(
UNEP
and
UNECE)
simply
require
the
potential
for
damage
to
human
health
and
the
environment.
According
to
OPP
criteria
discussed
in
the
risk
assessment,
PCNB
is
classified
as
very
highly
toxic
to
aquatic
invertebrates
(
LC50<
0.1
mg/
L)
on
an
acute
exposure
basis,
and
there
is
ample
evidence
based
on
screening­
level
risk
assessments
that
PCNB
is
likely
to
adversely
impact
the
environment.
There
is
sufficient
evidence
to
indicate
that
total
toxic
residues
of
PCNB
will
persist
in
the
environment
and
that
the
aquatic
community
is
particularly
vulnerable
to
this
chemical.
Based
on
the
screening­
level
assessment,
estimated
environmental
concentrations
are
sufficient
to
result
in
both
acute
and
chronic
effects
on
aquatic
animals
even
without
bioaccumulation
and
dietary
exposure
being
factored
into
the
exposure
estimate.
However,
when
coupled
with
the
potential
bioaccumulation
of
PCNB
in
the
food
chain,
aquatic
organisms
could
be
exposed
to
PCNB
residues
that
exceed
acute
and
chronic
effect
thresholds
by
several
orders
of
magnitude.
Page
7
of
9
Considering
Food
Chain
Effects
in
Risk
Estimates
The
propensity
of
a
compound
to
bioaccumulate
is
different
than
bioconcentration.
The
BCF
is
the
ratio
of
tissue
chemical
residues
to
the
chemical
concentration
in
water;
exposure
to
the
organism
(
e.
g.,
a
fish)
is
only
from
the
water
column
(
i.
e.,
exposure
is
due
to
uptake
by
the
gills
of
the
fish
only).
Bioaccumulation
factors
(
BAFs)
are
also
ratios
of
tissue
chemical
residues
to
chemical
concentration
in
the
water,
but
exposure
to
the
organism
(
e.
g.,
a
fish)
is
from
water
column
exposure
(
i.
e.,
gill
uptake)
and
the
diet.
With
increasing
propensity
of
a
chemical
to
be
fat
soluble
and
resistant
to
biotic
or
abiotic
degradation,
the
concentration
of
a
substance
will
increase
in
organisms
higher
in
the
food
chain
(
i.
e.,
insect­
eating
fish
will
have
lower
residues
that
fish­
eating
fish).
The
BCF
is
an
important
factor
in
estimating
bioaccumulation
potential,
because
it
is
very
difficult
to
empirically
measure
BAFs
in
the
laboratory.
Field­
measured
BAFs,
while
available
in
the
literature
for
many
compounds,
are
water­
body
specific
and
depend
on
the
nature
of
the
food
chain
and
the
amount
of
organic
carbon
in
the
sediment
and
water.
While
PCNB,
with
BCFs
ranging
between
1,100X
to
3,100X
for
various
aquatic
organisms,
shows
properties
that
are
indicators
of
the
potential
to
bioaccumulate,
the
actual
extent
of
bioaccumulation
for
PCNB
is
not
known.

To
estimate
PCNB's
bioaccumulation
potential
in
aquatic
food
chains,
OPP
used
a
model
implemented
by
the
EPA
Office
of
Water
(
see
Appendix
A).
Example
model
outputs
illustrate
the
magnitude
to
which
PCNB
could
bioaccumulate
in
aquatic
animals.

 
Residues
in
sediment
(
5,824
µ
g/
kg)
are
estimated
to
increase
to
100,582
µ
g/
kg
in
algae,
increase
to
105,018
µ
g/
kg
in
planktivorous
fish,
and
reach
105,097
to
722,418
µ
g/
kg
in
pisicivorous
fish,
depending
on
assumptions
for
PCNB's
ability
to
partition
in
organic
carbon
in
the
water
column.

Therefore,
depending
on
the
extent
to
which
PCNB
residues
partition
to
carbon
and
into
lipid
reserves,
residues
could
amplify
in
the
aquatic
food
chain.
The
extent
to
which
terrestrial
animals
will
be
impacted
by
PCNB
in
the
aquatic
food
chain
will
depend
on
their
reliance
on
aquatic
plants
and
animals
in
their
diet.
Although
PCNB
is
practically
nontoxic
to
both
birds
and
mammals
on
an
acute
exposure
basis,
the
length
of
exposure
required
to
result
in
chronic
effects
cannot
be
determined
from
the
data
available.
Large
piscivorus
mammals
could
consume
sufficient
quantities
of
PCNB
residues
to
exceed
chronic
toxicity
endpoints
for
mammals
by
several
orders
of
magnitude.

Characterizing
Ecological
Risk
 
Exposure
models
do
not
take
into
account
long­
range
transport.
Although
monitoring
data
targeting
PCNB
are
limited,
there
are
data
indicating
the
presence
of
PCNB
at
sites
in
Canada
distant
from
where
it
was
applied.

 
Field
studies
demonstrate
that
PCNB
persists
in
the
soil.
Current
terrestrial
exposure
models
do
not
account
for
uptake
of
persistent
residues
by
plants
several
years
after
PCNB
use.
Additionally,
the
screening­
level
risk
assessment
does
not
take
risk
to
terrestrial
invertebrates
into
account;
long­
term
exposure
of
soil
invertebrates
to
PCNB
appears
likely.

 
The
screening­
level
risk
assessment
for
aquatic
life
is
based
on
a
water
only
exposure
scenario.
For
chemicals
that
partition
to
sediments
and
are
persistent,
long­
term
aquatic
exposure,
and
chronic
risks,
can
be
underestimated
unless
a
dietary
exposure
route
is
included
in
the
risk
assessment.

 
PCNB
is
expected
to
move
to
surface
water
through
runoff
of
sediment­
bound
residues
and
Page
8
of
9
through
spraydrift.
PCNB
in
aquatic
systems
is
expected
to
be
associated
with
benthic
sediments
due
its
propensity
to
partition
into
organic
carbon
and
its
persistence.
PCNB
is
also
expected
to
bioaccumulate
in
aquatic
food
chains
(
see
Figure
2).
Even
if
PCNB
were
to
undergo
degradation
in
benthic
sediments,
its
degradates
are
also
considered
persistent
and
are
also
likely
to
bioaccumulate.
Benthic
invertebrates
as
well
as
phytoplankton
can
serve
as
a
major
routes
of
PCNB
entry
into
the
aquatic
food
chain.
Since
PCNB
and
its
degradates
are
highly
toxic
to
freshwater
invertebrates,
it
is
possible
that
benthic
macroinvertebrates
are
also
at
risk
to
increasing
concentrations
of
PCNB
and/
or
its
degradate
residues
in
sediments.

In
the
screening­
level
risk
assessment,
the
estimates
of
potential
of
adverse
effects
to
fish
and
wildlife
did
not
take
into
account
the
potential
for
PCNB
bioaccumulation.
The
wildlife
and
aquatic
life
chronic
screening­
level
RQ
values
for
PCNB
underestimate
risk
because
of
accumulation
of
this
persistent
compound
in
the
aquatic
food
chain
and
its
transfer
to
terrestrial
animals
that
may
depend
on
fish
and
aquatic
invertebrates
in
their
diet.
Including
an
estimate
of
dietary
exposure,
based
on
modeled
predictions
of
PCNB
bioaccumulation
in
the
food
chain,
increases
the
likelihood
of
adverse
effects
by
several
orders
of
magnitude.
Figure
2.
Potential
bioaccumulation
of
PCNB
residues
through
aquatic
food
chain
(
see
Appendix
A,
assumes
a
Koc
­
organic
carbon
partition
coefficient
of
17,508).
36
ug/
L
312,303
ug/
kg
441,189
ug/
kg
722,418
ug/
kg
Water
Algae
Planktivorous
Fish
Piscivorous
Animals
?

Piscivorous
Fish
Page
9
of
9
Appendix
A:
description
of
the
bioaccumulation
model
A
food
web
bioaccumulation
model,
implemented
by
the
EPA
Office
of
Water
(
http://
www.
epa.
gov/
glnpo/
lmmb/
foodweb.
html),
was
used
to
estimate
the
accumulation
of
PCNB
residues
in
the
aquatic
food
chain.
The
model
is
based
on
the
octanol­
water
partition
coefficient
of
the
chemical,
but
it
does
not
take
into
account
degradation.
The
model
was
used
to
estimate
the
extent
to
which
PCNB
could
bioaccumulate
in
aquatic
animals
based
on
PRZM/
EXAMS­
estimated
water
column
concentration
of
36.4
µ
g/
L
(
based
on
applications
to
cabbage).
Using
an
average
estimated
octanol­
water
partition
coefficient
(
Kow)
of
43651,
residues
in
sediment
expressed
on
a
dry
weight
basis
(
5,824
µ
g/
kg)
are
estimated
to
increase
to
100,582
µ
g/
kg
in
algae
and
reach
105,097
µ
g/
kg
in
pisicivorous
fish.
Using
the
highest
estimated
Kow
(
186,209),
PCNB
residues
in
pisicivorous
fish
reach
722,418
µ
g/
kg.
Therefore,
depending
on
the
extent
to
which
PCNB
residues
partition
into
lipid,
residues
could
amplify
in
the
aquatic
food
chain.
Although
the
residues
estimated
by
the
model
are
presumed
to
be
parent
PCNB
and
that
no
degradation
has
taken
place,
they
do
provide
an
upper
bound
on
possible
PCNB
residues
within
various
compartments
of
the
aquatic
food
chain
at
application
rates
used
on
cole
(
cabbage)
crops.
Estimated
environmental
concentrations
(
EECs)
for
cole
crops
do
not
represent
maximum
EECs
as
PRZM/
EXAMSestimated
water
column
concentrations
for
turf
were
as
high
as
97
µ
g/
L.

Although
there
are
no
residue
toxicity
studies
of
PCNB
available
with
which
to
compare
effects
levels
for
aquatic
animals,
it
is
possible
to
estimate
potential
effects
to
mammals
from
consumption
of
contaminated
prey.
The
equation
used
for
calculating
the
daily
food
intake
for
a
1000­
g
mammal
is
provided
below
(
Nagy
1987;
USEPA
1995).
The
analysis
assumed
that
large
mammals
would
weigh
1000
g
and
would
consume
roughly
263
g
(
wet
wgt.)
of
food
per
day
(
EQ
1).
The
estimated
dose
of
PCNB
in
pisicivorous
fish
would
range
between
28
to
190
mg
a.
i.
day­
1
based
on
the
range
of
residues
estimated
by
the
model.

Therefore,
large
(
1000
g)
piscivorous
mammals
would
consume
sufficient
quantities
of
PCNB
residues
to
exceed
the
chronic
no
observed
adverse
effect
concentration
(
NOAEC)
for
mammals
(
1.2
mg/
kg)
by
several
orders
of
magnitude.
Run­
off
from
turf
following
applications
to
sod
farms
are
expected
to
result
in
even
higher
residues
in
the
aquatic
food
chain.
(
EQ
1)
F
BW
W
=
 
0
621
1
0
564
.
*

(
)
.
