MEMORANDUM
July
5,
2001
SUBJECT:
MONURON:
Quantitative
Risk
Assessment
(
Q1*)
Based
On
F344/
N
Rat
Dietary
Study
With
3/
4'
s
Interspecies
Scaling
Factor,
P.
C.
Code
035501
TO:
Guruva
Reddy,
Veterinary
Medical
Officer
Registration
Action
Branch
1
Health
Effects
Division
(
7509C)

FROM:
Lori
L.
Brunsman,
Statistician
Science
Information
Management
Branch
Health
Effects
Division
(
7509C)

THROUGH:
Jess
Rowland,
Branch
Chief
Science
Information
Management
Branch
Health
Effects
Division
(
7509C)

Conclusion
The
most
potent
unit
risk,
Q1*(
mg/
kg/
day)­
1,
of
those
calculated
for
Monuron
is
that
for
male
rat
liver
neoplastic
nodule
and/
or
carcinoma
combined
tumor
rates
at
1.52
x
10­
2
in
human
equivalents.
The
dose
levels
used
from
the
104­
week
dietary
study
were
0,
750
and
1500
ppm
of
Monuron.
The
corresponding
tumor
rates
were
1/
50,
6/
49,
and
9/
50,
respectively.

Background
Quantifications
of
risk
have
subsequently
been
estimated
for
male
rat
liver
and
kidney
tumors.
The
most
potent
unit
risk
will
be
used
for
the
purpose
of
lifetime
cancer
risk
assessment
by
the
Agency.
In
this
case,
the
most
potent
unit
risk,
Q1*,
is
that
for
male
rat
liver
neoplastic
nodule
and/
or
carcinoma
combined
tumor
rates
at
1.52
x
10­
2
in
human
equivalents.

All
unit
risks
have
been
converted
from
animals
to
humans
by
use
of
the
3/
4'
s
scaling
factor
(
Tox_
Risk
program,
Version
3.5,
K.
Crump,
1994)
1.
For
the
conversion
to
human
equivalents,
weights
of
0.35
kg
for
the
rat,
70
kg
for
humans,
and
the
use
of
104
weeks
for
the
rat
life­
span
default
were
used.

It
is
to
be
noted
that
the
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
low
as
zero.

Dose­
Response
Analysis
The
study
indicated
survival
rates
of
male
rats
of
the
high
dose
group
to
be
increased
relative
to
the
controls,
but
the
actual
statistical
significance
of
mortality
could
not
be
determined
due
to
lack
of
individual
animal
data.
These
unit
risks,
Q1*>
s,
were
obtained
by
the
application
of
the
Multi­
Stage
model
(
Tox_
Risk
program,
Version
3.5,
K.
Crump,
1994).

Male
rats
had
a
significant
increasing
trend,
and
a
significant
difference
in
the
pairwise
comparison
of
the
1500
ppm
dose
group
with
the
controls,
for
liver
neoplastic
nodules
and/
or
carcinomas
combined,
both
at
p
<
0.01.

Additional
Q1*
Calculations
The
unit
risk,
Q1*(
mg/
kg/
day)­
1,
of
Monuron
based
upon
male
rat
liver
neoplastic
nodule
tumor
rates
is
1.31
x
10­
2
in
human
equivalents.
The
dose
levels
used
from
the
104­
week
dietary
study
were
0,
750
and
1500
ppm
of
Monuron.
The
corresponding
tumor
rates
were
1/
50,
6/
49,
and
7/
50,
respectively.

The
unit
risk,
Q1*(
mg/
kg/
day)­
1,
of
Monuron
based
upon
male
rat
kidney
renal
tubular
cell
adenoma
and/
or
adenocarcinoma
tumor
rates
is
1.30
x
10­
2
in
human
equivalents.
The
dose
levels
used
from
the
104­
week
dietary
study
were
0,
750
and
1500
ppm
of
Monuron.
The
corresponding
tumor
rates
were
0/
50,
3/
50,
and
15/
50,
respectively.

The
unit
risk,
Q1*(
mg/
kg/
day)­
1,
of
Monuron
based
upon
male
rat
kidney
renal
tubular
cell
adenocarcinoma
tumor
rates
is
8.22
x
10­
3
in
human
equivalents.
The
dose
levels
used
from
the
104­
week
dietary
study
were
0,
750
and
1500
ppm
of
Monuron.
The
corresponding
tumor
rates
were
0/
50,
1/
50,
and
8/
50,
respectively.

The
unit
risk,
Q1*(
mg/
kg/
day)­
1,
of
Monuron
based
upon
male
rat
kidney
renal
tubular
cell
adenoma
tumor
rates
is
9.91
x
10­
3
in
human
equivalents.
The
dose
levels
used
from
the
104­
week
dietary
study
were
0,
750
and
1500
ppm
of
Monuron.
The
corresponding
tumor
rates
were
0/
50,
2/
50,
and
7/
50,
respectively.

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