Document ID: EPA-HQ-OPP-2002-0138-0013
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2002-07-31T04:00Z

Page
1
of
8
U.
S.
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
DC
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
MEMORANDUM
PC
Code
No.
129106
DP
Barcode:
D279109
SUBJECT:
EFED
Review
of
Documents
Relative
to
Section
24c
Special
Local
Needs
Registration
of
Carbaryl
for
Use
on
Oyster
Beds.

TO:
Anthony
Britten,
Chemical
Review
Manager
Betty
Shackleford,
Product
Manager
Special
Review
and
Reregistration
Division
FROM:
Thomas
M.
Steeger,
Ph.
D.,
Senior
Biologist
Environmental
Risk
Branch
IV/
EFED
(7507C)

Through:
Betsy
Behl,
Branch
Chief
Environmental
Risk
Branch
IV/
EFED
(7507C)

The
Environmental
Fate
and
Effects
Division
(EFED)
has
completed
its
review
of
the
materials
submitted
relative
to
the
Section
24c
Special
Local
Needs
registration
of
carbaryl
for
use
on
oyster
beds
in
Willapa
Bay
and
Grays
Harbor,
Washington,
to
control
ghost
shrimp
(Callianassa
californiensis)
and
mud
shrimp
(Upogebia
pugettensis).
The
documents
included
1)
a
report
on
concentrations
of
carbaryl
and
its
degradate
(1­
naphthol)
in
marine
sediments
from
sites
treated
with
or
adjacent
areas
treated
with
Sevin
(Stonic
1999);
2)
a
fact
sheet
on
chemicals
of
special
concern
in
Washington
State;
3)
a
memo
from
the
State
of
Washington's
Department
of
Ecology's
review
of
data
relevant
to
the
environmental
effects
of
applying
Sevin
™
to
control
burrowing
shrimp
in
Willapa
Bay
and
Grays
Harbor
oyster
beds;
4)
a
copy
of
the
memorandum
of
agreement
between
the
Washington
State
Department
of
Ecology,
the
Willapa/
Grays
Harbor
Oyster
Growers'
Association
and
other
state
government
and
private
organizations;
and
5)
a
Washington
State
Department
of
Ecology
publication
entitled
Carbaryl
Concentrations
in
Willapa
Bay
and
Recommendations
for
Water
Quality
Guidelines
(Johnson
2001).
Except
for
more
recent
studies
conducted
by
Washington
State
University
and
the
Washington
Department
of
Ecology,
much
of
the
older
(pre­
1996)
data
had
procedural
problems
that
limited
the
utility
of
the
data.
The
more
recent
data
indicate
that
carbaryl
residues
in
the
water
column
were
generally
at
or
below
an
effect
threshold
of
0.1
ug/
L
Although
large
carbaryl
applications
can
affect
water
quality
in
areas
distant
from
spray
sites,
the
Washington
Department
of
Ecology
concluded
that
"no
widespread
effects
from
carbaryl
would
be
expected
in
Wallapa
Bay
after
the
end
of
the
[carbaryl]
application
period."

Carbaryl
has
been
used
on
approximately
600
acres
of
Willapa
Bay
and
200
acres
of
Grays
Harbor
at
a
rate
of
7.5
to
10
lbs/
acre/
year
since
the
1960's.
Carbaryl
is
applied
as
a
wettable
powder
Page
2
of
8
to
tidelands
at
low
low
[Spring]
tide
primarily
by
helicopter;
however,
hand
spraying
is
used
in
some
instances.
The
label
restricts
aerial
applications
within
200
feet
of
a
channel
or
slough;
hand
spraying
is
prohibited
within
50
feet
of
a
channel
or
slough.

The
data
collected
and/
or
reviewed
by
the
Washington
Department
of
Ecology
indicate
that
carbaryl
residues
drop
below
the
level
of
quantitation
(<
0.004
ug/
L)
approximately
6
weeks
after
application.
While
concentrations
in
nontarget
areas
immediately
following
the
carbaryl
application
period
are
likely
to
inflict
mortality
to
aquatic
organisms,
no
data
are
provided
to
demonstrate
that
threatened
and/
or
endangered
species
(e.
g.
salmonids)
are
adversely
affected
by
the
treatments
to
oyster
beds.

While
these
documents
provide
additional
information
on
the
environmental
fate
and
effects
of
carbaryl
in
estuarine/
marine
environments,
EFED's
review
of
Washington's
Section
24c
petition
was
based
on
the
required
guideline
fate
and
effects
data
provided
by
the
registrant
in
support
of
the
reregistration
of
carbaryl.
Although
the
EFED
reregistration
eligibility
document
(RED)
for
carbaryl
does
not
estimate
environmental
concentrations
for
applications
directly
to
tidelands
for
control
of
burrowing
shrimp
in
oyster
culture,
it
does
discuss
the
use.
Data
submitted
in
support
of
reregistration
(MRID
419826­
06)
indicate
that
estuarine/
marine
invertebrates
will
likely
be
impacted
by
this
route
of
exposure
and
that
certain
species,
e.
g.,
Dungenese
crab
(Cancer
magister),
may
experience
100%
mortality
in
the
application
area.
However,
the
assessment
goes
on
to
note
that
effects
on
aquatic
invertebrates
will
likely
be
temporary
as
most
populations
show
signs
of
recovery
within
2
months.
Additionally,
the
chapter
suggests
that
carbaryl
applications
that
reduce
the
potential
for
drift
to
nontarget
sites,
such
as
direct
injection
of
carbaryl
into
the
sediment,
may
help
mitigate
nontarget
effects.

Review
of
Submitted
Literature
1)
Screening
Survey
of
Carbaryl
(Sevin)
and
1­
naphthol
Concentrations
in
Willapa
Bay
Sediments
The
study
was
undertaken
to
determine
the
long­
term
persistence
of
carbaryl
and
1­
naphthol;
more
specifically,
the
study
objectives
were
to:

°
Determine
if
there
are
residues
of
carbaryl
and
its
degradate
1­
naphthol
in
the
marine
sediments
at
historically
sprayed
sites
and
unsprayed
adjacent
sites
°
Monitor
the
depletion
of
these
compounds
in
sediments
following
applications
of
Seven
™
.
°
Measure
concentrations
of
carbaryl
in
centrifuged
sediment
pore
water.
°
Determine
drift
potential.

The
study
was
divided
into
two
phases,
pre­
spray
and
post­
spray.
Sampling
was
conducted
in
Willapa
Bay
in
areas
deemed
to
be
conducive
to
carbaryl
persistence.
Thus,
areas
with
muddy
and/
or
fine
sediments
were
selected
since
they
were
believed
to
be
more
likely
to
retain
both
carbaryl
and
1­
naphthol.
Sandy
sediments
were
not
believed
to
provide
sufficient
clay
or
organic
material
with
which
carbaryl
and/
or
its
degradate
could
sorb.
Page
3
of
8
0
500
1000
1500
2000
2500
3000
3500
010
2030
40
50
60
Days
after
Treatment
Carbaryl
(ppb)

Figure
1
Average
carbaryl
concentrations
in
sediment
collected
from
Willapa
Bay
at
2,
30
and
60
days
after
treatment.
Pre­
spray
samples
were
collected
from
areas
that
had
been
sprayed
in
previous
years
or
were
adjacent
to
areas
that
had
been
sprayed
in
previously.
A
reference
site,
Nemah
Oyster
Reserve,
was
sampled
as
an
area
that
had
never
been
sprayed.

Post­
spray
samples
were
collected
immediately
following
carbaryl
treatment
and
also
included
areas
adjacent
to
spray
sites.
Treated
sites
included
areas
that
had
been
sprayed
in
years
past
in
addition
to
the
recent
treatment.
Sampling
was
typically
conducted
2,
30
and
60
days
after
treatment
(DAT).
Sediment
samples
were
collected
using
a
stainless
steel
17­
cm
diameter
device
that
allowed
sediment
samples
to
be
stratified
into
0
­
2
cm,
2
­
7.5
cm,
and
7.5
­
15
cm
depths.
Total
organic
carbon
(TOC)
and
sediment
size
were
also
analyzed.
Carbaryl
and
1­
naphthol
residues
were
measured
both
in
whole
sediment
and
in
centrifuged
pore
water.
Quality
assurance
spiked
sediment
samples
suggest
considerable
amount
of
variability
in
recovery
of
standards.
The
results
may
be
negatively
biased.

Based
on
the
pre­
spray
study
results,
all
of
the
historically
sprayed
sites,
adjacent
unsprayed
sites
and
the
reference
site
showed
no
carbaryl
or
1­
naphthol
residues
above
the
detection
limit
range
of
21
to
58
ppb.
One
sample
representing
the
shallowest
area
adjacent
to
historically
sprayed
beds
had
trace
(29
ppb)
residues
of
carbaryl.

Post­
spray
study
results
indicate
that
carbaryl
concentrations
at
sprayed
sites
ranged
from
2,000
to
3,400
ppb
by
2
DAT,
180
to
220
ppb
by
30
DAT,
and
86
­
120
ppb
by
60
DAT
(Figure
1).
Although,
adjacent
sites
contained
as
much
as
2,000
ppb
2
DAT,
residues
in
sediment
at
all
adjacent
sites
at
60
DAT
were
close
to
detection
limits
and
ranged
from
27
to
32
ppb.

Residues
for
the
1­
naphthol
ranged
from
detection
limits
to
as
high
as
170
ppb
at
2
DAT
and
by
30
DAT
all
samples
had
dropped
to
detection
limits
(22
to
33
ppb);
one
sample
at
60
DAT
contained
naphthol
at
34
ppb.
The
report
concluded
that
once
carbaryl
degrades
to
1­
naphthol,
the
degradate
appears
to
readily
leave
the
sediment.
It
did
not
however,
allow
for
the
fact
that
the
degradate
could
have
been
present
in
deeper
reaches
of
the
sediment.
At
adjacent
sites,
1
naphthol
ranged
as
high
as
120
ppb
2
DAT
and
then
dropped
to
below
detection
limits
for
the
remaining
sample
periods.

Carbaryl
residues
in
pore
water
were
only
detected
60
DAT
and
ranged
from
0.57
to
1.15
ppb.
It
is
difficult
to
understand
though
how
the
limit
of
detection
for
pore
water
was
so
much
lower
than
that
for
sediment.
Carbaryl
was
only
detected
in
one
sediment
pore
water
sample
collected
from
an
adjacent
site;
the
residue
was
close
to
the
limit
of
detection
at
0.05
ppb.
Page
4
of
8
Analyses
of
sediment
grain
size
and
total
organic
carbon
revealed
that
the
clay­
silt
fraction
of
the
post
spray
sites
ranged
from
25%
to
73%
while
TOC
ranged
from
0.58%
to
2.07%.
Grain
size
and
TOC
were
strongly
correlated
(Pearson
R
2
range
0.89
­
0.96);
however,
there
was
no
correlation
between
carbaryl
residues
and
TOC.

The
study
concludes
that
carbaryl
is
clearly
persistent
in
treatment
areas
with
residues
being
detected
up
to
60
DAT.
Additionally,
residues
in
sites
adjacent
to
treated
areas
indicate
that
drift
does
occur.
Drift
to
nontarget
sites
was
attributed
to
wind,
depth
of
water
sampled,
and
both
surface
and
bottom
water
currents.
Additionally,
sediment
pore
water
concentrations
exceeded
the
National
Academy
of
Sciences
and
Engineering
water
quality
recommendation
for
carbaryl
of
0.06
ppb.
Additionally,
historic
sampling
revealed
that
water
column
concentrations
prior
to
application
ranged
as
high
as
9.2
ppb.
The
report
notes
that
QA/
QC
standards
suggested
that
actual
pore
water
concentrations
may
be
higher
than
those
reported.
It
is
uncertain
how
much
naphthol
was
present
in
the
water
column;
however,
given
that
naphthol
is
more
toxic
than
the
parent,
the
potential
affect
of
the
residues
on
aquatic
animals
is
a
legitimate
concern.

Finally
the
report
compares
the
sediment
residue
data
to
available
toxicity
data
on
carbaryl
and
concludes
that
Dungeness
crab
larvae
exposed
to
carbaryl
at
concentrations
ranging
from
0.1
to
10
ppb
for
25­
days
exhibited
both
molting
effects
and
mortality.
Although
no
formal
data
were
provided
on
the
numbers
of
organisms
affected;
the
author
reports
that
marine
fish
and
invertebrate
mortality
was
observed
2
DAT.
The
author
proposes
that
the
incidental
kills
could
serve
as
forage
for
other
fish
and
foraging
birds
that
would
then
bioaccumulate
carbaryl
in
their
tissues.
The
report
further
suggests
that
indirect
effects,
such
as
endocrine
disruption
and
mutagenicity,
are
not
sufficiently
characterized
and
that
coupled
with
direct
effects
and
the
potential
for
bioaccumulation
in
the
food
chain,
carbaryl
and
1­
naphthol
have
the
potential
to
impact
threatend
and/
or
endangered
salmon
stocks.

The
study
would
have
been
more
thorough
had
water
column
concentrations
of
carbaryl
been
measured.
Given
that
the
compound
was
applied
using
both
aerial
and
hand­
held
sprayers,
it
is
difficult
to
assess
the
affect
of
drift
relative
to
application
method.
It
would
have
also
been
helpful
to
know
how
representative
the
areas
sampled
were
of
the
total
areas
treated
in
terms
of
TOC
and
grain
size.
Additionally,
the
limit
of
detection
(25
­
35
ppb)
was
not
sufficiently
low
to
document
residues
in
sediment
and
pore
water
that
may
have
been
sufficiently
high
to
effect
benthic
invertebrates.

2)
Chemicals
of
Special
Concern
in
Washington
State
Report
published
by
the
Washington
Department
of
Ecology
provides
a
brief
overview
of
the
environmental
fate
and
effects
of
carbaryl.
Although
the
overview
has
footnote
numbers,
no
references
were
provided;
therefore,
data
supporting
carbaryl's
characterization
could
not
be
verified.
The
report
implies
that
carbaryl
is
relatively
persistent
and
that
recoveries
of
aquatic
systems
exposed
to
carbaryl
have
taken
as
long
as
3
years.
According
to
the
overview,
carbaryl
is
teratogenic,
immunosuppressive,
and
degrades
to
carcinogenic
compounds.
Page
5
of
8
3)
Washington
Department
of
Ecology
Review
of
Data
Relevant
to
the
Envrionmental
Effects
of
Applying
Carbaryl
to
Control
Burrowing
Shrimp
in
Willapa
Bay
and
Grays
Harbor
Oyster
Beds
(1987).

The
object
of
the
Washington
Department
of
Ecology
review
was
to
answer
the
following
questions:

°
How
long
do
carbaryl
and
its
primary
hydrolysis
product
1­
naphthol
persist
in
the
water
column?
°
What
concentrations
of
carbaryl
and
1­
naphthol
in
water
are
toxic
to
marine
organisms?
°
How
long
do
carbaryl
and
1­
naphthol
persist
in
the
sediments?
°
What
concentrations
of
carbaryl
and
1­
naphthol
in
sediment
are
toxic
to
marine
organisms?
°
What
are
the
effects
on
abundance
and
diversity
of
infauna?
°
What
are
the
effects
on
abundance
and
diversity
of
epifauna?
°
What
mortality
is
experienced
by
Dungenees
crab
and
how
does
this
affect
the
fishery?
°
What
mortality
is
experienced
by
fish?
°
Are
birds
adversely
affected?
°
What
are
the
potential
ecological
impacts
of
Sevin
applications?

While
the
environmental
fate
studies
on
water
column
and
sediment
concentrations
during
and
after
application
of
carbaryl
showed
a
decline
in
carbaryl
and
1­
naphthol
concentrations,
much
of
the
data
were
discounted
due
to
poor
detection
limits
and
procedural
deficiencies.
Open
literature
reviews
of
ecological
effects
revealed
that
carbaryl
is
more
toxic
to
crustaceans
than
to
molluscs
or
fish;
however,
the
degradate
1­
naphthol
is
less
toxic
to
crustaceans
than
carbaryl
but
more
toxic
than
the
parent
to
molluscs
and
fish.
Subacute
effects
of
carbaryl
were
reported
at
concentrations
below
the
detection
limit
(1
mg/
L)
of
most
of
the
monitoring
studies
reported;
the
report
states
that
circumstantial
evidence
suggests
the
potential
for
toxic
effects
at
or
below
0.1
mg/
L
in
sediment.
Sublethal
effects
included
reduced
development
of
oysters
and
delayed
molting
of
crab
larvae,
malformations
in
fish
eggs
and
adults.
Toxicity
of
carbaryl
is
reported
to
increase
with
temperature.

Although
the
report
fails
to
conclusively
resolve
whether
carbaryl
and
its
1­
naphthol
degradate
are
sufficiently
persistent
to
effect
aquatic
life,
it
notes
that
the
target
population
of
burrowing
shrimp
take
a
number
of
years
to
recover.
However,
failure
of
a
treated
area
to
recover
may
be
due
to
a
number
of
factors
and
may
not
result
exclusively
on
the
toxicity
of
carbaryl
or
its
degradate.
Page
6
of
8
0
100
200
300
400
500
600
1976
1978
1980
1982
1984
1986
1988
Year
Acres
Treated
Figure
2.
Number
of
acres
treated
with
carbaryl
in
Willapa
Bay
over
years.

0
10000
20000
30000
40000
50000
60000
0
100
200
300
400
500
600
Number
of
AcresTreated
Number
of
Crabs
Killed
Figure
3.
Number
of
crabs
killed
versus
number
of
acres
treated
with
carbaryl
in
Willapa
Bay.
Fisheries
data
collected
on
Willapa
Bay
from
1977
to
1986
show
(Figure
2)
that
the
number
of
acres
treated
with
carbaryl
increased
each
year.
And
that
the
number
of
crabs
killed
by
carbaryl
treatment
also
increased
(Figure
3)
as
the
number
of
acres
treated
increased.
The
number
of
crabs
killed
was
significantly
correlated
(Pearson
Correlation
coefficient
=
0.72;
p
>
rho
=
0.0187)
with
the
number
of
acres
treated.
Over
the
observation
period
an
average
of
53
crabs
(standard
error
=
13)
were
killed
per
acre.

Follow70000
up
studies
by
the
University
of
Washington
that
[Dungeness]
crab
in
treated
areas
are
impacted
but
that
further
studies
are
required
to
establish
population­
level
effects
in
Willapa
Bay.

Mortalities
to
fish
were
limited
to
small
specimens
which
were
entrapped
in
shallow
pools
by
the
outgoing
tide
and
directly
exposed
to
carbaryl
during
treatment;
however,
the
reviewed
literature
did
not
address
the
potential
for
indirect
mortality.

Althoughno
studieswereconducted,the
reportconcludedthatlikelihood
ofacuteorchronic
effects
of
carbaryl
on
birds
was
remote.

Whether
there
are
broad
ecological
impacts
associated
with
the
use
of
carbaryl
to
control
burrowing
shrimp
in
Willapa
Bay
remains
an
uncertainty.
The
Environmental
Impact
Statement
concluded
that
the
use
of
carbaryl
by
the
commercial
oyster
industry
was
not
expected
to
cause
significant
impacts
on
the
estuarine
ecosystem
when
applied
at
current
levels.
It
based
this
conclusion
on
the
fact
that:

°
Carbaryl
is
not
accumulated
by
any
food
chain
component
or
transmitted
to
higher
levels
in
the
food
chain.
°
No
chemically
active
radical
group
remains
to
contaminate
the
estuarine
environment.
°
Only
a
small
percentage
of
the
total
intertidal
lands
are
treated
annually;
0.8%
in
Willapa
Bay
and
0.3%
in
Grays
Harbor.
Page
7
of
8
The
report
recommends
though
that
further
work
be
conducted
to
evaluate
the
persistence
of
carbaryl
and
1­
naphthol
in
sediment
and
to
better
document
the
effects
of
nontarget
mortality.

4)
Burrowing
Shrimp
Integrated
Pest
Management
Memorandum
of
Agreement
The
memorandum
of
agreement
(MOA)
was
established
between
the
Washington
State
Department
of
Ecology,
Washington
State
Department
of
Agriculture,
the
Washington
State
Commission
on
Pesticide
Registration,
the
Washington
Department
of
Fish
and
Wildlife,
the
Willapa/
Grays
Harbor
Oyster
Growers
Association,
the
Pacific
Coast
Shellfish
Growers
Association
and
the
Pacific
Shellfish
Institute.
The
agreement
acknowledges
that
while
carbaryl
and
its
1­
naphthol
degradate
affect
nontarget
species,
are
likely
transported
several
hundred
yards
offsite
by
tidal
action,
and
may
persist
for
several
weeks
in
the
water
column
and
sediments
within
Willapa
Bay/
Grays
Harbor,
treatment
for
burrowing
shrimp
is
necessary
if
economic
losses
due
to
diminished
oyster
harvests
are
to
be
avoided.
The
agreement
acknowledges
that
additional
data
on
the
environmental
fate
and
effects
of
carbaryl
are
necessary
and
that
alternative
methods
of
control
should
be
explored
to
mitigate
adverse
effects
especially
on
threatened/
endangered
salmonids.
The
MOA
establishes
a
process
and
time
for
the
development
of
a
"sustainable
site­
specific,
environmentally
sound
and
ecologically
based
[integrated]
pest
management
plan
for
the
control
of
burrowing."
The
MOA
outlines
criteria
to
be
met,
i.
e.,
demonstration
that
burrowing
shrimp
populations
have
reached
a
size
sufficient
to
inflict
economic
losses,
before
which
carbaryl
can
be
applied.

5)
Carbaryl
Concentrations
in
Willapa
Bay
and
Recommendations
for
Water
Quality
Guidelines.

In
the
summer
of
2000,
the
Washington
State
Department
of
Ecology
initiated
a
study
of
Willapa
Bay.
The
study
was
a
follow­
up
on
the
Stonic
(1999)
study
from
1996
to
1997
and
concern
that
carbaryl
persisted
at
a
level
of
0.7
ug/
L.
The
objectives
of
the
study
were
to:

°
determine
if
there
is
a
carbaryl
background
that
persists
in
Willapa
Bay
water
outside
the
July
to
August
spray
period;
°
analyzie
carbaryl
in
other
potential
sources
to
Willapa
Bay;
°
achieve
quantitation
limits
for
carbaryl
sufficiently
low
to
evaluate
the
potential
for
causing
toxicity
to
sensitive
marine
organisms;
°
review
the
literature
on
carbaryl's
effects
on
marine
organisms
and
evaluate
appropriate
water
quality
guidelines
for
carbaryl
in
Willapa
Bay.

Results
from
the
study
show
that
carbaryl
was
frequently
detected
in
Willapa
Bay
up
to
4
days
after
application
to
oyster
beds
and
that
carbaryl
was
transported
several
miles
from
the
site
of
application.
However,
the
study
showed
no
evidence
of
carbaryl
background
in
the
Willapa
Bay
water
column.
Additionally,
tributaries
and
cranberry
bog
drainages
were
not
significant
carbaryl
sources.
Carbaryl
had
dropped
to
levels
below
quantitation
(0.004
ug/
L)
approximately
1
month
after
application
Page
8
of
8
Based
on
a
review
of
toxicity
data
on
35
marine
species,
the
report
recommended
0.06
ug/
L
as
a
probable
safe
level
for
marine
organisms
and
a
range
of
0.1
to
0.7
ug/
L
as
a
potential
effects
threshold.
The
value
of
0.06
ug/
L
was
based
on
a
National
Academy
of
Science
approach
using
an
EC50
of
6
ug/
L
for
inhibiting
molting
in
Dungeness
crab
larvae
divided
by
a
100X
safety
factor.
The
data
collected
from
open
literature
suggests
that
carbaryl
is
more
toxic
to
crustaceans
and
echinoderms
than
to
fish,
molluscs,
or
polychaetes.
The
study
notes
that
while
similar
information
was
not
collected
on
the
1
naphthol
degradate,
one
study
has
shown
it
to
be
roughly
twice
as
toxic
to
fish
as
the
parent
compound
but
less
toxic
to
crustaceans.
Carbaryl
was
detected
at
concentrations
within
the
proposed
potential
effects
threshold
several
miles
from
treatment
areas
up
to
several
days
following
application.
The
report
recommended
that
future
water
quality
monitoring
focus
on
the
period
during
or
immediately
after
carbaryl
applications
and
that
data
are
collected
on
carbaryl's
1­
naphthol
transformation
product.
Additionally,
the
report
recommends
that
future
effects
testing
include
more
sensitive
test
species
and
indigenous
aquatic
species
that
serve
as
prey
for
endangered/
threatened
species
References
Stonic,
Cynthia.
1999.
Screening
Survey
of
Carbaryl
(Sevin
™
)
and
1­
naphthol
Concentrations
in
Willapa
Bay
Sediments.
Washington
State
Department
of
Ecology.
Publication
No.
99­
323.

Johnson,
Art.
2001.
Carbaryl
Concentrations
in
Willapa
Bay
and
Recommendations
for
Water
Quality
Guidelines.
Washington
State
Department
of
Ecology.
Environmental
Assessment
Program.
Publication
No.
01­
03­
005.