Subject:
Diuron­
Revised
Q1*,
(
3/
4'
s
Interspecies
Scaling
Factor),
1985
Wistar
Rat
2
Year
Dietary
Study
PC
035505
From:
Bernice
Fisher,
Biostatistician
Statistics
Section
Science
Analysis
Branch/
HED
(
7509C)

To:
Linda
Taylor,
Ph.
D,
Pharmacologist
Review
Section
II
Toxicology
Branch
II/
HED
(
7509C)

Thru:
Hugh
M.
Pettigrew,
PhD.,
Section
Head
Statistics
Section
Science
Analysis
Branch/
HED
(
7509C)

The
revised
unit
risk,
Q1*(
mg/
kg/
day)­
1
of
Diuron,
based
upon
male
rat
urinary
bladder
carcinomas
is
1.91x10­
2
in
human
equivalents
(
converted
from
animals
to
humans
by
use
of
the
3/
4'
s
scaling
factor­
1994,
Tox_
Risk,
3.5­
K.
Crump)
a.
The
dose
levels
used
in
the
Wistar
rat
dietary
study
(
1985­
Bayer
AG
T
8010647)
were
0,
25,
250
and
2500
ppm
of
Diuron.
The
corresponding
tumor
rates
in
male
rats
were
1/
49,
0/
50,
1/
49
and
35/
48
respectively.
These
doses
and
rates
were
obtained
from
the
memorandum
by
L.
L.
Brunsman­
Diuron
Qualitative
Risk
Assessment
Based
on
Wistar
Rat
and
NMRI(
SPF
Han)
Mouse
Dietary
Studies,
November
11,1996.

a
See
Memo
­
Deriving
Q1*
s
Using
the
Unified
Interspecies
Scaling
Factor,
P.
A.
Fenner­
Crisp,
Director­
HED,
7/
1/
94.

cc:
Caswell
file
M.
Metzger
E.
Waldman
B.
Doyle
C.
Scheltema
L.
Nisenson
Background
The
Health
Effects
Division
Carcinogenicity
Peer
Review
Committee,
December
18,
1996
recommended
that
the
estimate
of
unit
risk
should
be
based
on
male
Wistar
rat
carcinomas
in
the
urinary
bladder.
Dose­
Response
Analysis
Since
mortality
was
not
affected
differentially
with
increasing
doses
of
Diuron,
the
estimate
of
the
unit
risk,
Q1*
in
human
equivalents
was
obtained
by
the
application
of
the
Multi­
Stage
model(
Tox_
Risk
program,
version
3.5
­
K.
Crump).

The
estimate
of
unit
risk,
Q1*,
was
based
upon
the
urinary
bladder
carcinomas
in
male
rats.

For
the
conversion
to
human
equivalents,
weights
of
.40
kg
for
the
males
and
70
kg
for
humans
and
the
3/
4'
s
scaling
factor
were
used.

It
is
to
be
noted
that
Q1*
(
mg/
kg/
day)­
1
is
an
estimate
of
the
upper
bound
on
risk
and
that
(
as
stated
in
the
EPA
Risk
Assessment
Guidelines)
"
the
true
value
of
the
risk
is
unknown,
and
may
be
as
l
