1
PC
Code:
32501
DP
Barcode
267486
MEMORANDUM
TO:
Christina
Scheltema
PM
Team
Reviewer
Betty
Shackleford
Chief
Reregistration
Branch
3
Special
Review
and
Registration
Branch
7508C
FROM:
James
K.
Wolf
Soil
Scientist
THRU:
Arnet
Jones
Chief
Environment
Risk
Branch
3
Environmental
Fate
and
Effects
Division
7507C
RE:
The
Interagency
Study
of
the
Impact
of
Pesticide
Use
on
Ground
Water
in
North
Carolina.
March
4,
1997
(Ground
­water
contamination
from
disulfoton
use
on
Christmas
trees
in
NC
was
the
only
topic
considered
in
this
assessment).

DATE:
July
28,
2000
Conclusions:

Based
upon
this
monitoring
study
and
OPP's
understanding
of
the
use
practices
of
disulfoton
(e.
g.,
hand
broadcast
below
a
tree)
associated
with
Christmas
tree
production
in
North
Carolina,
no
additional
ground­
water
monitoring
for
disulfoton
resulting
from
Christmas
tree
production
is
necessary
at
this
time.
This
recommendation
could
change
depending
upon
the
results
of
other
monitoring
efforts
(e.
g.,
NAWQA)
associated
with
other
uses
(e.
g.,
high
frequency
of
detections)
or
concern
for
degradates
not
considered
in
the
monitoring
study.
Detection
limits
or
limits
of
quantification
should
be
lower
in
any
broader
base
sampling.

There
were
no
detections
of
disulfoton,
disulfoton
sulfoxide,
and
disulfoton
in
the
ground­
water
monitoring
study
conducted
in
North
Carolina.
Efforts
were
made
to
place
the
wells
in
vulnerable
areas
where
the
pesticide
use
was
known,
so
that
the
pesticide
analyzed
for
would
reflect
the
use
history
around
the
well.
Limitations
of
the
study
include
that
sites
were
sampled
only
twice
and
the
limits
of
detections
were
high
(e.
g.,
>
1.0
µg/
L)
for
some
of
disulfoton
analytes.
Uncertainties
associated
with
the
study
include
whether
two
samples
from
eight
wells
are
adequate
to
represent
the
ground­
water
concentrations
of
disulfoton
residues,
did
2
DRASTIC
correctly
identify
a
site's
vulnerability,
and
were
the
wells
placed
down­
gradient
of
the
use
areas.

General:

The
North
Carolina
Departments
of
Agriculture
(NCDA)
and
Environment,
Health,
and
Natural
Resources
(DEHNR)
conducted
a
cooperative
study
under
the
direction
of
the
North
Carolina
Pesticide
Board.
The
purpose
of
the
statewide
study
was
to
determine
if
the
labeled
uses
of
pesticide
products
were
impacting
the
ground
water
resources
in
North
Carolina.

The
study
was
conducted
in
two
phases.
In
phase
I,
55
wells
in
the
DEHNR
Ground
Water
Section's
ambient
monitoring
network
representing
the
major
drinking
water
aquifers
of
the
state
were
sampled
at
least
twice
and
analyzed
for
selected
pesticides.
In
phase
II,
97
cooperator
monitoring
wells
were
installed
and
subsequently
sampled
at
least
twice
in
36
counties
across
the
North
Carolina.
Sites
for
the
cooperator
monitoring
wells
were
chosen
based
on
an
evaluation
of
the
vulnerability
of
ground
water
to
risk
of
contamination
from
the
use
of
pesticides.

Monitoring
wells
were
located
adjacent
to
and
down­
gradient
from
areas
where
pesticides
were
reported
to
have
been
applied
(within
300
feet)
during
the
previous
five
years.
Wells
were
constructed
so
that
the
shallowest
ground
water
could
be
collected
for
analysis.
The
objective
of
these
criteria
was
to
use
a
scientific
method
for
determining
monitoring
well
locations
so
that
the
results
could
be
used
as
an
early
indication
of
the
potential
for
problems
associated
with
pesticides
leaching
to
ground
water.
The
study
authors
make
the
following
statement,
"Results
cannot
be
interpreted
as
representing
the
quality
of
ground
water
near
pesticide
use
areas
statewide
because
the
study
methods
targeted
areas
of
highly
vulnerable
ground
water".

The
study
used
tools
and
information
available
at
the
time
of
the
study
to
identify
vulnerable
locations
for
well
placement.
This
included
statewide
agricultural
data
from
the
N.
C.
Agricultural
Statistics
which
were
used
to
identify
crop
growing
areas,
the
USEPA
DRASTIC
method
(Aller
et
al.,
1987)
was
used
to
locate
the
most
vulnerable
locations
in
the
target
crop
growing
areas,
and
local
county
agents
of
the
USDA
Natural
Resources
Conservation
Service
(NRCS)
helped
identify
cooperators­
farmers
for
placement
of
wells.
The
Pesticide
Study
staff
and
county
agents
also
met
with
the
cooperators
to
obtain
pesticide
use
information.
Other
studies
have
shown
that
DRASTIC
is
not
as
good
a
method
to
identify
vulnerable
areas
as
hoped.
The
study
appeared
to
QA/
QC
practices.

Wells
were
sampled
in
two
rounds
in
phase
II,
approximately
six
months
apart.
If
a
chemical
was
detected
in
any
well,
a
follow­
up
sample
was
collected
from
the
same
well
and
analyzed
for
the
same
chemical.

Seven
of
the
55
ambient
monitoring
wells
in
phase
I
had
pesticide
residues
detected
in
at
least
one
sample
collected.
In
the
cooperator
phase
(II)
of
the
study,
26
of
97
wells
had
pesticide
3
detected
in
at
least
one
water
sample
collected
from
each
well.
None
were
disulfoton
residues.

Disulfoton:

Disulfoton,
disulfoton
sulfone,
and
disulfoton
sulfoxide
represented
three
analytes
measured
in
the
study.
Two
different
labs
conducted
the
analysis
of
water
samples.
The
stated
limits
of
quantification
were
1.0
µg/
L,
2.3
µg/
L,
and
not
established
for
disulfoton,
disulfoton
sulfone,
and
disulfoton
sulfoxide,
respectively
for
the
Division
of
Environmental
Management
Laboratory.
The
second
lab's
limits
of
quantification
were
0.3
µg/
L,
3.8
µg/
L,
and
0.38
for
disulfoton,
disulfoton
sulfone,
and
disulfoton
sulfoxide,
respectively
for
the
North
Carolina
Department
of
Agricultural
Laboratory.

Disulfoton
residues
were
monitored
for
in
five
North
Carolina
counties,
Alleghany,
Ash,
Beaufort,
Madison,
and
Robeson.
Seven
wells
were
located
in
Christmas
Tree
growing
areas,
one
in
wheat
growing
county,
and
2
in
tobacco
areas.
The
breakout
of
wells
sampled
and
analyzed
for
disulfoton
in
each
county
by
crop
are
summarized
in
the
Table
1.
There
were
no
detections
of
disulfoton
residues
in
any
samples
collected
in
the
study.
Simazine
and
lindane
were
detected
at
two
of
the
Christmas
tree
sites
Table
1.
Summary
of
sites
samples
for
disulfoton
or
Christmas
tree
growing
area
in
North
Carolina.

County
Crop
Disulfoton
Use
Ground
Water
Detection
Alleghany
Christmas
Trees
no
no
Ash
Christmas
Trees
no
no
Ash
Christmas
Trees
yes
no
Ash
Christmas
Trees
yes
no
Alleghany
Christmas
Trees
yes
no
Alleghany
Christmas
Trees
yes
no
Ash
Christmas
Trees
yes
no
Beaufort
Wheat
yes
no
Madison
Tobacco
yes
no
Robeson
Tobacco
yes
no
Aller,
L.
T.,
T.
Bennett,
J.
H.
Lehr,
R.
J.
Petty,
and
G.
Hackett.
1987.
DRASTIC:
A
Standardized
4
System
for
Evaluating
Ground
Water
Pollution
Potential
Using
Hydrogeologic
Setting.
USEPA
Document
#
EPA/
600/
2­
85­
018.
