U.
S.
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
DC
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
PC
Code:
1090001
DP
Code:
D281176
MEMORANDUM
DATE:
April
15,
2002
SUBJECT:
Tier
II
Estimated
Drinking
Water
Concentrations
(
EDWCs)
for
Human
Health
Risk
for
oxadiazon
on
Florida
Golf
Course
TO:
Veronique
LaCapra,
Chemical
Review
Manager
Margaret
Rice,
Branch
Chief
Special
Review
and
Reregistration
Division
(
7508C)

FROM:
Faruque
A.
Khan,
Ph.
D.,
Environmental
Scientist
José
Luis
Meléndez,
Chemist
Environmental
Fate
and
Effects
Division
THROUGH:
Mah
T.
Shamim,
Ph.
D.,
Chief
Jean
Holmes,
Biologist,
RAPL
Environmental
Risk
Branch
V
Environmental
Fate
and
Effects
Division
This
memo
presents
the
Tier
II
surface
drinking
water
assessment
for
oxadiazon.
The
EDWCs
for
oxadiazon
were
based
on
the
proposed
maximum
application
rate
(
8.0
lbs
a.
i./
A,
3
applications)
on
golf
coarse,
which
constitute
the
major
use
of
the
chemical.
The
mean
values
of
EDWCs
over
a
36­
year
period
based
on
Florida
Turf
Scenario
for
various
segments
of
the
golf
course
(
green,
tees,
fairways,
and
rough
)
are
summarized
in
Table
1.
Adjustments
can
be
made
to
calculate
cumulative
EDWCs
for
various
segments
of
the
golf
coarse
by
adding
EECs
for
each
segment
of
interest.
For
example,
the
sum
of
the
chronic
EDWCs
for
green,
tees
and
,
fairways
would
be
20.73
(
i.
e.
2.10+
18.63)
µ
g
L­
1.

Table
1.
Recommended
EDWCs
of
Oxadiazon
for
human
health
risk
assessment.

Exposure
Greens
&
Tees
Fairways
Roughs
Golf
Coarse
­­­­­­­­­­­­­­­­­­(
µ
g
L­
1)­­­­­­­­­­­­­­­­­­

Acute
(
1/
10
peak
value)
7.7
44.28
128.65
180.63
Non­
cancer
Chronic
(
1/
10
yearly
value)
2.76
15.87
46.24
64.87
Cancer
Chronic
(
Mean
36­
year
annual
concentration)
2.10
18.63
35.22
55.95
Note:
µ
g
L­
1
=
ppb
2
1.0
Estimation
of
surface
water
exposure
concentrations
The
maximum
application
rate
and
relevant
environmental
fate
parameters
for
oxadiazon
were
used
in
the
Tier
II
model
(
PRZM/
EXAMS)
for
EDWCs
in
the
surface
water.
The
output
of
the
screening
model
represent
an
upper­
bound
estimate
of
the
concentrations
of
oxadiazon
that
might
be
found
in
surface
water
due
to
use
of
oxadiazon
on
golf
coarse.

2.0
Background
Information
on
PRZM/
EXAMS
simulation
PRZM/
EXAMS
modeling
using
the
Index
Reservoir
(
IR)
and
the
Percent
Crop
Area
(
PCA)
adjustment
was
used
to
estimate
concentrations
in
surface
water
used
as
a
source
of
drinking
water.
The
index
reservoir
represents
a
watershed
that
is
more
vulnerable
than
most
used
as
drinking
water
sources.
It
was
developed
from
a
real
watershed
in
western
Illinois.
The
index
reservoir
is
used
as
a
standard
watershed
that
is
combined
with
local
soils,
weather,
and
cropping
practices
to
represent
a
vulnerable
watershed
for
each
crop
that
could
support
a
drinking
water
supply.
If
a
community
derives
its
drinking
water
from
a
large
river,
the
estimated
exposure
would
likely
be
higher
than
the
actual
exposure.
Conversely,
a
community
that
derives
its
drinking
water
from
smaller
bodies
of
water
with
minimal
outflow
would
likely
get
higher
drinking
water
exposure
than
estimated
using
the
index
reservoir.
Areas
with
a
more
humid
climate
that
use
a
similar
reservoir
and
golf
coarse
turf
management
practices
would
likely
get
more
pesticides
in
their
drinking
water
than
predicted
levels.

A
single
steady
flow
has
been
used
to
represent
the
flow
through
the
reservoir.
Discharge
from
the
reservoir
also
removes
chemical
from
it
so
this
assumption
will
underestimate
removal
from
the
reservoir
during
wet
periods
and
overestimates
removal
during
dry
periods.
This
assumption
can
both
underestimate
or
overestimate
the
concentration
in
the
reservoir
depending
upon
the
annual
precipitation
pattern
at
the
site.
The
index
reservoir
scenario
uses
the
characteristic
of
a
single
soil
to
represent
all
soils
in
the
basin.
Soils
can
vary
substantially
across
even
small
areas,
thus,
this
variation
is
not
reflected
in
these
simulations.

The
index
reservoir
scenario
does
not
consider
tile
drainage.
Areas
that
are
prone
to
substantial
runoff
are
often
tile
drained.
This
may
underestimate
exposure,
particularly
on
a
chronic
basis
(
the
watershed
on
which
the
IR
is
based
had
no
documented
tile
drainage).
Additionally,
EXAMS
is
unable
to
easily
model
spring
and
fall
turnover
which
would
result
in
complete
mixing
of
a
chemical
through
the
water
column
during
these
events.
Because
of
this
inability,
Shipman
City
Lake
has
been
simulated
without
stratification.
There
is
data
to
suggest
that
Shipman
City
Lake
does
stratify
in
the
deepest
parts
of
the
lake
at
least
in
some
years.
This
may
result
in
both
an
over
and
underestimation
of
the
concentration
in
drinking
water
depending
upon
the
time
of
the
year
and
the
depth
the
drinking
water
intake
is
drawing
from.
A
full
description
of
the
Index
Reservoir
is
provided
in
the
"
Guidance
for
Use
of
the
Index
Reservoir
in
Drinking
Water
Exposure
Assessment"
from
EFED
upon
request.

Development
a
Percent
Crop
Area
(
PCA),
watershed­
based
adjustment
factor
for
the
percent
of
land
in
production
for
golf
coarse
has
not
been
performed.
Therefore,
the
drinking
water
concentrations
for
oxadiazon
were
estimated
using
adjusting
factors
recommended
in
the
EFED
guidance
document
for
the
turf
scenario
(
Carleton,
et.
al.,
2001).
The
predicted
concentrations
are
multiplied
by
0.04
(
fractional
area
analogous
to
PCA)
for
an
average
green
and
tee
areas,
0.23
(
fractional
area
analogous
to
PCA)
for
fairways,
and
an
average
0.67
(
fractional
area
analogous
to
PCA)
for
roughs
(
Appendix
A).
These
multipliers
were
comparable
to
the
surveyed
data
conducted
by
the
Golf
Course
Superintends
3
Table
2.
PRZM/
EXAM
Input
Parameters
for
Oxadiazon
Parameters
and
Units
Oxadiazon
Source
PC
Code
1090001
Molecular
Weight
(
g
Mole­
1)
345.2
Product
Chemistry
Vapor
pressure
(
Torr)
1.0
E­
6
Product
Chemistry
Water
solubility
(
mg
L­
1)
*
1.0
Product
Chemistry
Hydrolysis
half­
life
@
pH
5
(
Days)
Stable
MRID
41863603
Hydrolysis
half­
life
@
pH
7
(
Days)
Stable
MRID
41863603
Hydrolysis
half­
life
@
pH
9
(
Days)
38
MRID
41863603
Aerobic
soil
metabolism
t
½
,
(
Days)*
841
MRID
42772801
Aerobic
aquatic
metabolism
(
Days)*
1682**
EFED
Guidence
Anaerobic
aquatic
metabolism
(
Days)*

365
MRID
42773802
Direct
Aqueous
Photolysis
(
Days)
2.75
MRID
41897201
Soil
Water
Partition
Coefficient
(
Koc,
L
Kg­
1)
2352
MRID
1898202
Florida
Turf
Management
Pesticide
Application
Rates
(
lbs
a.
i./
A)
2.0
and
4.0
SRRD
Application
Frequency
2X
and
1X
SRRD
Application
Interval
(
days)
30
and
135
SRRD
First
Application
Date
March
15
SRRD
Spray
Efficiency
99%
EFED
Spray
Drift
6.40%
EFED
PCA***
Green
and
Tees
Fairways
Roughs
4.00%
23.00%
67.00%
EFED
*
=
Water
solubility
was
multiplied
by
10
according
to
Guidance
for
selecting
input
parameters
in
modeling
for
environmental
fate
and
transport
of
*
=
Selected
input
parameters
were
multiplied
by
3
according
to
Guidance
for
selecting
input
parameters
in
modeling
for
environmental
fate
and
**
=
2X
of
soil
aerobic
metabolismhalf­
life
input
value.

***
=
Fractional
use
area
analogous
to
percent
crop
area
Association
of
America.
They
reported
that
an
average
for
teeing
areas
is
2%,
putting
green
2%,
fairways
23%,
rough/
wood/
water
70%,
and
building
and
grounds
3%
and
that
an
average
of
150­
200
acres
of
total
land
is
used
for
an
18­
hole
golf
course
facility.

The
linked
PRZM
and
EXAM
model
is
typically
used
by
EFED
in
estimating
pesticides
concentrations
in
surface
waters.
PRZM
is
employed
to
evaluate
runoff
loading
to
a
receiving
surface
body.
As
soon
as
the
pesticides
residues
reaches
the
surface
water,
EXAMS
uses
algorithms
to
estimate
the
4
pesticides
concentrations
by
taking
into
account
different
dissipation
mechanisms
in
the
aqueous
and
sediment
phases,
weather
patterns,
and
periodic
application
of
pesticides
for
several
years.

3.0
Florida
Turf
Scenario
This
scenario
based
on
the
the
EFED
standard
citrus
scenario,
models
a
field
located
in
Osceola
County,
Florida
in
the
Adamsville
sand,
a
hyperthermic,
uncoated
Aquic
Quartzipsamment
in
MLRA
156A.
The
Adamsville
sand
is
a
somewhat
poorly
drained,
rapidly
permeable
soil
that
formed
in
thick
sandy
marine
sediments
occurring
in
Central
and
Southern
Florida
on
slopes
of
0­
5
percent.
Adamsville
sand
ranges
from
a
Hydrologic
Group
A
soil
to
a
Hydrologic
Group
C
soil,
depending
on
the
water
table.
For
the
purpose
of
this
modeling,
EFED
used
the
curve
numbers
from
the
PIC
of
the
Adamsville
sand
as
a
Group
C
soil.
Runoff
from
application
on
turf
was
modeled
using
the
EFED
standard
turf
scenario
(
Carleton,
et.
al.,
2001).

To
develop
a
turf
scenario
the
citrus
scenario
was
modified
by
adding
a
2
cm
thick
layer
of
A
thatch@
on
top
of
the
soil
profile.
The
thatch
layer
has
the
following
properties:
bulk
density
=
0.37;
field
capacity
=
0.47;
wilting
point
=
0.27;
organic
carbon
=
7.5%.
Curve
numbers
were
selected
based
on
A
good
condition@
open
space
areas
as
specified
in
TR­
55,
that
for
hydrologic
soil
groups.
A
2
cm
layer
of
thatch
is
typical
for
golf
course
fairways,
but
is
probably
thicker
than
average
for
golf
course
greens.

Turf
is
considered
to
be
essentially
generic,
with
no
distinction
made
between
sod
farms,
golf
course
fairways,
greens
and
tees,
or
residential
lawns.
For
chemicals
applied
to
golf
courses,
the
fraction
of
the
total
area
composed
of
greens,
tees,
and
fairways
may,
however
be
used
to
modify
the
results
of
a
modeling
run,
somewhat
in
the
fashion
of
a
percent
cropped
area
(
PCA)
adjustment.
The
approximate
average
percent
areas
(
confirmed
by
Mike
Kenna,
USGA,
personal
communication)
are
as
follows:
fairways,
23%;
greens,
2%;
tees,
2%.
Thus
if
a
pesticide
is
only
used
on
greens
and
tees,
for
example,
the
modeling
results
would
be
multiplied
by
a
factor
of
0.04.

4.0
Modeling
Inputs
and
Results
The
weather,
golf
coarse
management
practices,
and
oxadiazon
applications
were
simulated
over
36
years
so
that
the
ten
year
excedence
probability
at
the
site
could
be
estimated.
The
EDWC's
generated
in
this
analysis
were
estimated
using
PRZM
3.12
(
Pesticide
Root
Zone
Model
)
for
simulating
runoff
and
erosion
from
the
agricultural
field
and
EXAMS
2.97.5
(
Exposure
Analysis
Modeling
System)
for
estimating
environmental
fate
and
transport
in
surface
water.
Table
2
summarizes
the
input
values
used
in
the
Florida
Golf
Coarse
model
run
for
PRZM/
EXAMS.
Attached
to
this
memo
is
a
copy
of
the
printout
generated
from
the
PRZM/
EXAMS
run
(
See
Appendix
A).

5.0
References
Carleton,
J.,
J.
Lin,
and
M.
Corbin.
2002.
Development
of
a
modeling
approach
to
estimate
runoff
of
pesticide
residues
from
managed
turf
grass.
Memorandum
issued
on
February
27,
2002
on
the
subject
"
PRZM
Standard
Crop/
Location
Scenarios,
Procedure
to
Develop
and
Approve
New
Scenarios,
and
PRZM
Turf
Modeling
Scenarios
to
Date"
by
Elizabeth
Leovey,
Acting
Director
of
Environmental
Fate
And
Effect
Division
of
the
Office
of
Pesticides,
Environmental
Protection
Agency,
Washington
D.
C.

EFFD
Guidance
document.
2001.
Guidance
for
selecting
input
parameters
in
modeling
for
environmental
fate
and
transport
of
pesticides.
Version
II.
December
4,
2001.
5
Appendix
A
Florida
Turf(
2.00
lbs
X
2X
and
4.00
lbs
X
1X
applications)

Chemical:
Oxadiazon
PRZM
environment:
FLOXATRF.
inp
EXAMS
environment:
INDEXRES.
EXV
Metfile:
met156A.
met
WATER
COLUMN
DISSOLVED
CONCENTRATION
(
PPB)

YEAR
PEAK
96
HOUR
21
DAY
60
DAY
90
DAY
YEARLY
­­­­
­­­­
­­­­­­­
­­­­­­
­­­­­­
­­­­­­
­­­­­­
1948
242.000
236.000
215.000
180.000
160.000
50.980
1949
112.000
109.000
101.000
90.350
83.690
63.400
1950
74.410
72.960
68.120
58.650
53.490
38.110
1951
73.530
72.160
66.680
56.480
51.260
39.540
1952
210.000
205.000
187.000
154.000
139.000
63.590
1953
105.000
103.000
99.710
87.230
79.180
60.070
1954
92.800
91.020
85.580
77.490
71.290
53.220
1955
63.750
62.710
59.680
53.670
49.610
40.750
1956
55.700
54.680
52.380
50.060
47.080
33.150
1957
161.000
157.000
143.000
119.000
112.000
66.870
1958
169.000
166.000
151.000
129.000
115.000
66.050
1959
113.000
111.000
104.000
89.500
82.190
59.850
1960
140.000
137.000
128.000
116.000
106.000
67.850
1961
85.600
84.050
78.420
73.590
68.740
52.540
1962
68.250
67.010
62.160
56.550
56.250
42.300
1963
111.000
109.000
102.000
88.070
78.290
49.370
1964
107.000
105.000
96.260
90.100
86.820
60.240
1965
148.000
145.000
133.000
122.000
108.000
62.890
1966
109.000
107.000
100.000
94.900
87.020
71.590
1967
109.000
107.000
103.000
95.120
88.300
65.750
1968
112.000
111.000
108.000
101.000
94.220
67.920
1969
79.310
78.140
72.690
63.590
56.750
45.180
1970
98.620
96.960
90.130
76.970
69.270
50.640
1971
84.820
83.200
77.290
68.930
63.760
44.640
1972
93.450
91.590
84.920
79.580
74.520
48.020
1973
50.060
49.180
46.770
42.220
39.300
31.670
1974
63.840
62.890
58.230
49.290
46.990
34.390
1975
40.150
39.430
36.700
32.370
31.470
26.370
1976
54.370
53.310
49.600
45.990
43.700
33.380
1977
235.000
232.000
214.000
198.000
181.000
87.790
1978
67.640
66.730
63.140
56.240
52.850
40.150
1979
185.000
181.000
170.000
144.000
130.000
73.100
1980
84.110
82.580
78.420
70.970
64.470
53.390
1981
101.000
99.370
92.320
78.970
72.440
47.590
1982
107.000
105.000
102.000
96.830
92.650
59.920
1983
54.200
53.310
50.180
46.460
45.450
39.870
SORTED
FOR
PLOTTING
­­­­­­
­­­
­­­­­­­­

PROB
PEAK
96
HOUR
21
DAY
60
DAY
90
DAY
YEARLY
­­­­
­­­­
­­­­­­­
­­­­­­
­­­­­­
­­­­­­
­­­­­­
0.027
242.000
236.000
215.000
198.000
181.000
87.790
0.054
235.000
232.000
214.000
180.000
160.000
73.100
6
0.081
210.000
205.000
187.000
154.000
139.000
71.590
0.108
185.000
181.000
170.000
144.000
130.000
67.920
0.135
169.000
166.000
151.000
129.000
115.000
67.850
0.162
161.000
157.000
143.000
122.000
112.000
66.870
0.189
148.000
145.000
133.000
119.000
108.000
66.050
0.216
140.000
137.000
128.000
116.000
106.000
65.750
0.243
113.000
111.000
108.000
101.000
94.220
63.590
0.270
112.000
111.000
104.000
96.830
92.650
63.400
0.297
112.000
109.000
103.000
95.120
88.300
62.890
0.324
111.000
109.000
102.000
94.900
87.020
60.240
0.351
109.000
107.000
102.000
90.350
86.820
60.070
0.378
109.000
107.000
101.000
90.100
83.690
59.920
0.405
107.000
105.000
100.000
89.500
82.190
59.850
0.432
107.000
105.000
99.710
88.070
79.180
53.390
0.459
105.000
103.000
96.260
87.230
78.290
53.220
0.486
101.000
99.370
92.320
79.580
74.520
52.540
0.514
98.620
96.960
90.130
78.970
72.440
50.980
0.541
93.450
91.590
85.580
77.490
71.290
50.640
0.568
92.800
91.020
84.920
76.970
69.270
49.370
0.595
85.600
84.050
78.420
73.590
68.740
48.020
0.622
84.820
83.200
78.420
70.970
64.470
47.590
0.649
84.110
82.580
77.290
68.930
63.760
45.180
0.676
79.310
78.140
72.690
63.590
56.750
44.640
0.703
74.410
72.960
68.120
58.650
56.250
42.300
0.730
73.530
72.160
66.680
56.550
53.490
40.750
0.757
68.250
67.010
63.140
56.480
52.850
40.150
0.784
67.640
66.730
62.160
56.240
51.260
39.870
0.811
63.840
62.890
59.680
53.670
49.610
39.540
0.838
63.750
62.710
58.230
50.060
47.080
38.110
0.865
55.700
54.680
52.380
49.290
46.990
34.390
0.892
54.370
53.310
50.180
46.460
45.450
33.380
0.919
54.200
53.310
49.600
45.990
43.700
33.150
0.946
50.060
49.180
46.770
42.220
39.300
31.670
0.973
40.150
39.430
36.700
32.370
31.470
26.370
1/
10
192.500
188.200
175.100
147.000
132.700
69.021
MEAN
OF
ANNUAL
VALUES
=
52.559
STANDARD
DEVIATION
OF
ANNUAL
VALUES
=
14.081
UPPER
90%
CONFIDENCE
LIMIT
ON
MEAN
=
56.034
EEC
calculations:

FOR
Tees
and
Greens
Acute
EEC
=
(
1/
10
peak
value)(
Percent
area
for
Green
&
Tee)
=
(
192.5
µ
g/
L)(
0.04)
=
7.70
µ
g/
L
Non­
cancer
Chronic
EEC
=(
1/
10
yearly
value)(
Percent
area
for
Green
&
Tee)
(
69.02
µ
g/
L)(
0.04)
=
2.76
µ
g/
L
Cancer
chronic
EEC
=
(
Mean
of
annual
value)(
Percent
area
for
Green
&
Tee)
(
52.56
µ
g/
L)(
0.04)
=
2.10
µ
g/
L
7
FOR
Fairways
Acute
EEC
=
(
1/
10
peak
value)(
Percent
area
for
Fairway)
=
(
192.5
µ
g/
L)(
0.23)
=
44.28
µ
g/
L
Non­
cancer
Chronic
EEC
=(
1/
10
yearly
value)(
Percent
area
for
FAirways)
(
69.02
µ
g/
L)(
0.23)
=
15.87
µ
g/
L
Cancer
chronic
EEC
=
(
Mean
of
annual
value)(
Percent
area
for
Fairways)
(
52.56
µ
g/
L)(
0.23)
=
12.08
µ
g/
L
FOR
Roughs
Acute
EEC
=
(
1/
10
peak
value)(
Percent
area
for
Roughs)
=
(
192.5
µ
g/
L)(
0.67)
=
128.65
µ
g/
L
Non­
cancer
Chronic
EEC
=(
1/
10
yearly
value)(
Percent
area
for
Rough)
(
69.02
µ
g/
L)(
0.67)
=
46.24
µ
g/
L
Cancer
chronic
EEC
=
(
Mean
of
annual
value)(
Percent
area
for
Rough)
(
52.56
µ
g/
L)(
0.67)
=
35.22
µ
g/
L
