Document ID: EPA-HQ-OPP-2002-0250-0012
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2002-09-24T04:00Z

UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
PC
Code:
206600
DP
Barcode
D282389
DATE:
May
3,
2002
MEMORANDUM
SUBJECT:
Response
to
Registrant's
30­
Day
Error
Comments
on
the
Drinking
Water
Assessment
and
Aqueous
Photolysis
Photodegradation
of
Fenarimol
FROM:
E.
Laurence
Libelo,
Ph.
D.,
Environmental
Engineer
Norman
B.
Birchfield,
Ph.
D.
Biologist
Environmental
Risk
Branch
IV
Environmental
Fate
and
Effects
Division
(
7507C)

THROUGH:
Elizabeth
Behl,
Chief
Environmental
Risk
Branch
IV,
Environmental
Fate
and
Effects
Division
(
7507C)

TO:
Tom
Myers,
Product
Manager
Reregistration
Branch
II,
SRRD
(
7508C)

Gowan
has
submitted
comments
on
the
EFED
Drinking
Water
Assessment
to
Support
the
TRED
for
fenarimol.
The
few
comments
on
estimated
drinking
water
exposure
are
general
criticisms
of
the
tools,
approaches
and
policies
used
by
the
Agency
to
estimate
pesticide
concentrations
in
drinking
water.
The
registrant
states
the
results
of
the
FIRST
model
is
not
adequate
to
support
"
risk
mitigation
decisions".
Gowan
supports
this
position
by
stating
that
the
FIRST
model
is
a
screening
model
and
that
an
earlier
Gowan
submission
suggests
that
monitored
concentrations
in
a
study
on
organophosphates
are
substantially
lower
than
EFED
modeling
results.

EFED
agrees
that
there
is
a
large
amount
of
uncertainty
in
the
EECs
produced
using
the
Tier
I
screening
model
FIRST.
FIRST,
and
other
models
used
in
EFED
risk
assessments
have
been
reviewed
by
the
Science
Advisory
Panel,
and
it
is
a
standard,
accepted
tool
for
generating
initial,
conservative
EECs.
In
contrast
to
Gowan's
statement
that
EFED
uses
a
pond
scenario
to
estimate
drinking
water
exposures,
FIRST
models
pesticides
applied
to
a
vulnerable
agricultural
watershed
which
drains
into
a
drinking
water
reservoir.
The
Agency
routinely
uses
FIRST
modeling
in
screening­
level
assessments
and
if
levels
of
concern
are
exceeded
more
refined
modeling
is
typically
used
to
refine
estimates.
However,
the
FIRST
model
(
as
well
and
PRZM
and
EXAMS)
requires
a
certain
amount
of
information
to
be
input
on
the
persistence
and
mobility
2
of
a
pesticide.
Typically
these
inputs
are
derived
from
CFR
part
158
data
required
in
support
of
registration.
In
the
case
of
fenarimol,
this
data
is
lacking.
Until
data
on
the
fate
and
transport
of
the
compound
is
submitted
it
is
not
possible
to
refine
the
assessment
using
higher
tier
models.
An
initial
attempt
to
use
PRZM/
EXAMS
modeling
with
the
current
lack
of
data
has
shown
that
"
refinement"
may
result
in
an
increase
in
the
drinking
water
exposure
values
by
more
than
an
order
of
magnitude.
EFED
does
not
believe
that
a
refinement
would
be
meaningful
at
this
point
in
time
given
the
lack
of
required
basic
data;
with
the
current
lack
of
reliable
data
it
is
not
possible
to
determine
drinking
water
concentrations
with
any
reasonable
level
of
certainty.
EFED
has
requested
that
additional
data
be
provided
to
fulfill
the
basic
core
data
requirements
for
this
compound.
Upon
submission
of
adequate
data
more
refined
modeling
may
be
used
to
better
estimate
fenarimol
concentrations
in
drinking
water.

In
addition
to
the
uncertainty
around
fenarimol
concentrations
in
drinking
water
there
is
also
substantial
uncertainty
regarding
the
occurrence,
identity
and
concentration
of
fenarimol
degradates.
Only
one
of
the
degradates
formed
in
the
aqueous
photolysis
study
has
been
identified.
This
degradate,
4­
chloro­
2­(
5­
pyrimidyl)­
2'­
clorobenzophenone,
was
deemed
to
be
of
toxicological
concern
by
the
Health
Effects
Division's
MARC
panel.
Gowan
has
supplied
no
data
on
the
mobility,
persistence
or
toxicity
of
this
degradate.
In
their
comments
the
registrant
states
that
this
degradate
is
one
of
many
unknown
degradates
which
form
as
a
result
of
aqueous
photolysis.
The
lack
of
identification
and
assessment
of
these
compounds
increases
the
uncertainty
in
this
assessment.

A
default
Percent
Cropped
Area
(
PCA)
factor
of
0.87
should
be
applied
to
the
surface
water
EECs
as
the
registrant
indicated.
This
has
resulted
in
recalculated
EEC
values
that
are
slightly
lower
then
initially
modeled.
Using
this
PCA,
the
new,
highly
uncertain
EEC
values
for
surface
water
are:
211
ppb
for
the
acute
and
51
ppb
for
the
chronic
drinking
water
exposure
values.
These
values
represent
the
1­
in­
10
year
peak
surface
water
concentration
and
1­
in­
10
year
mean
yearly
concentration
based
on
very
limited
data
for
estimating
the
magnitude
and
duration
of
exposure.
This
concentration
applies
to
fenarimol
alone
(
insufficient
data
exists
to
model
the
photodegradate
of
toxicological
concern).

The
registrant
makes
reference
to
the
formation
and
information
on
the
identity
of
"
more
then
80"
degradates.
This
and
any
other
data
which
may
be
used
to
better
understand
the
environmental
behavior
of
fenarimol
and
its
degradates
should
submitted
to
the
Agency.
Similarly,
the
monitoring
study
conducted
by
the
CDC
that
the
registrant
refers
to
in
their
comments
should
be
submitted.