CARBOFURAN:

Weight
Of
Evidence
Comparison
Of
Human
And
Animal
Studies
For
Single
And
Cumulative
Chemical
Assessment
John
Liccione,
Ph.
D.

John
Liccione,
Ph.
D.

Elissa
Elissa
Reaves,
Ph.
D.

Reaves,
Ph.
D.

U.
S.
EPA
Office
of
Pesticide
Programs
U.
S.
EPA
Office
of
Pesticide
Programs
May
2,
2006
May
2,
2006
2
Outline
for
Carbofuran
Presentation
Outline
for
Carbofuran
Presentation

Background/
History
of
Carbofuran

Single
Oral
Dose
Human
Study

Dermal
Human
Studies

BMD
Analyses

Incorporation
of
HS
into
Cumulative
Risk
Assessment
3
Carbofuran
in
Single
and
Cumulative
Carbofuran
in
Single
and
Cumulative
Assessments
Assessments

The
60­
day
public
comment
period
for
the
carbofuran
acute,
aggregate
(
single
chemical)

risk
assessment
closes
mid­
May
2006

Carbofuran
is
a
member
of
the
N­
methyl
carbamate
(
NMC)
common
mechanism
group

Rapid
inhibition
of
acetylcholinesterase
(
AChE)

followed
by
recovery
4
What
is
Carbofuran?

What
is
Carbofuran?


Broad
spectrum
N­
methylcarbamate
insecticide/
nematocide

Soil
and
foliar
pests
 
field,
fruit
and
vegetable
crops

Ornamentals
5
Human
Intentional
Dosing
Studies
Human
Intentional
Dosing
Studies
1.
Single
Oral
Dose
(
1976)

2.
Acute
Dermal
Dose
(
1977)

3.
Acute
Dermal
Dose
(
1978)
6
Animal
Toxicity
Studies
Animal
Toxicity
Studies

Acute
Oral

Rat,
rabbit,
guinea
pig

Repeat
Oral

Subchronic/
Chronic
dog,
rat,
mouse

DNT,
Sub
Neurotox,

Special
PK,
CCA

21­
Day
Dermal

Rabbit

Repeat
Inhalation

None

Developmental

Rat,
rabbit

Reproduction

Rat
7
Carbofuran:
Noncancer
Effects
Carbofuran:
Noncancer
Effects

Animals

ChE
inhibition
 
plasma,
RBC,
brain

Clinical
signs
­
 
motor
activity
&
tremors
(
rat
CCA),
 

landing
foot
splay
(
rat
sub
neurotox)


Timing
of
peak
inhibition
(
as
early
as
15
min.
for
RBC
ChE
in
adult
rats;
15
min.
for
brain
ChE
in
pup
and
adult
rats)


Human

ChE
inhibition

Clinical
signs
8
1.

1.
Acute
Oral
Study
Acute
Oral
Study
(
Arnold
1976)

(
Arnold
1976)

Design:
9
healthy
male
subjects.
Pt
A:
Open
Pt
B:

Randomized,
double
blind
2
­

­

1
Part
B
2
­

­

(
3)
­

2
­

(
2)
­

­

2
None
(
1)

PART
A
0.25
0.1
0.05
0
Dose
(
mg/
kg)

Study
Phase
(
Session)
9
1.

1.
Acute
Oral
Study
Acute
Oral
Study
(
Arnold
1976)

(
Arnold
1976)


Parameters

RBC/
plasma
ChE,
EKG,
blood
pressure,

heart
rate,
temperature,
respiration,

pupil
size,
blood
chemistry,
urinalysis,

clinical
signs,
vestibular
fn
(
balance),

eye
accomodation

Pre
and
up
to
24
hr
postdose.
For
ChE
 
0,
0.5,
1,
2,
3,
6
&
24
hrs.
10
1.

1.
Acute
Oral
Study
Acute
Oral
Study
(
Arnold
1976)

(
Arnold
1976)

Results
of
Single
Oral
Human
Study
with
Carbofuran
Dose
RBC
ChEI1
Symptoms
Control
10%

0.05
mg/
kg
11%,

22%
2
No
symptoms
noted.

1
Percent
decrease
provided
for
each
individual
subject
on
study.

2
Seen
at
1­
hr;
almost
returned
to
normal
by
3
hr
in
all
subjects.
11
1.

1.
Acute
Oral
Study
Acute
Oral
Study
(
Arnold
1976)

(
Arnold
1976)

Results
of
Single
Oral
Human
Study
with
Carbofuran
(
Continued)

Dose
(
mg/
kg)
RBC
ChEI1
Symptoms
0.1
33%,

31%
2
­
Headache
(
subject
1);
lightheadedness
(
subject
2)

­
abnorm
EKG;
deterioration
in
vestibular
fn
(
balance)

2
Seen
at
1­
hr;
almost
returned
to
normal
by
3
hr
in
all
subjects.
12
1.

1.
Acute
Oral
Study
Acute
Oral
Study
(
Arnold
1976)

(
Arnold
1976)

Results
of
Single
Oral
Human
Study
with
Carbofuran
(
Continued)

Dose
(
mg/
kg)
RBC
ChEI
Symptoms
0.25
46%,
63%,
62%,

59%
3
of
4
subjects:

­
multiple
clinical
signs
­
 
heart
rate
 
body
temp.,
 
respiration
rates,

abnormal
EKG
13
1.

1.
Acute
Oral
Study
Acute
Oral
Study
(
Arnold
1976)

(
Arnold
1976)


Study
Strengths

Clear
clinical
signs
at
0.25
mg/
kg
(
2
were
the
only
non­
smokers)


Multiple
doses
used

Frequent
monitoring
of
parameters

ChEI
 
occurred
at
expected
peak
time
14
1.

1.
Acute
Oral
Study
Acute
Oral
Study
(
Arnold
1976)

(
Arnold
1976)


Study
Weaknesses

2
subjects
for
low
&
mid
dose;
4
for
high­
dose;

males
only

Control
subject
 
erratic
plasma
ChE
inhibition

Abnormal/
borderline
vestibul
fn
(
balance)
&
EKG
in
control
and
some
of
tx
subjects

Cigarette
smoking
 
confounder?
15
1.

1.
Acute
Oral
Study
Acute
Oral
Study
(
Arnold
1976)

(
Arnold
1976)


Study
weaknesses
continued:


Predosing
blood
and
urine
values
were
erratic;

limited
individual
data;


Different
measurement
of
RBC
 
may
not
be
optimal

No
dose
selection
rationale

Open
design
(
Pt
A)


No
statistics
16
2.

2.
Acute
Dermal
Acute
Dermal
(
1977)

(
1977)
­
Design
Design
Dose
(
mg/
kg)

1
High
temp
(
85­
95
°
F)/
high
humidity
(
68­
89%)
conditions.
2
Normal
temperature/
normal
humidity
conditions
­

­

­

­

2
­

C
1
2
2
2
2
­

­

B
2
­

­

­

2
2
2
2
­
­

A
1
32
8.0
4.0
2.0
1.0
0.5
0
Phase
17
2.

2.
Acute
Dermal
Acute
Dermal
(
1977)

(
1977)


Design:
Open,
18
healthy
adult
males.
75%
a.
i.


50%
slurry
on
upper
back
(
5.7­
40
cm
2
:
size
 
with
dose)


Mild
exercise
 
5min;
rest
 
15
min;
repeat
cycle
11X/
4hrs

Test
material
removed;
24
hr.
monitor.
Parameters
­
RBC/
plasma
ChE,
EKG,
BP,
HR,
Temp,
Resp,
pupil
size,
eye
accom,
hematol,
urinalysis,
clinical
signs
18
2.

2.
Acute
Dermal
Acute
Dermal
(
1977)

(
1977)

Results
of
Arnold
1977
Study:
Part
A
(
High
temperature/
humidity)

Dose
RBC
ChEI
Symptoms
Control
10%,
10%

0.5
mg/
kg
20%,
23%

(@
3
hrs)

1.0
mg/
kg
39%,
9%

(@
3
and
1
hrs)
No
symptoms
noted.
19
2.

2.
Acute
Dermal
Acute
Dermal
(
1977)

(
1977)­
Part
A
Part
A
Results
of
Human
Dermal
Study
(
Arnold,
1977)
with
Carbofuran:
Part
A
continued
Dose
RBC
ChEI
Symptoms
2.0
mg/
kg
46%,

65%

(@
4
hrs)
­
One
subject:
weak
and
shaky
at
3.5
hrs
(
atropine
at
5
hrs).

­
Second
subject:
lightheadedness,
hazy
vision,

vomiting,
defecation,
muscular
cramps,
chills
(
2.5
to
4
hrs.)
Back
washed.
Atropine
 
3
times.

­
Both:
abnormal
balance.
Both
subjects
were
asymptomatic
at
24
hrs
post­
dosing.
20
2.

2.
Acute
Dermal
Acute
Dermal
(
1977)

(
1977)­
Part
B
Part
B
Results
of
Arnold
1977
Study:
Part
B
(
Normal
Temperature/
Humidity)

Dose
RBC
ChEI2
Symptoms
2.0
mg/
kg
10%,
20%

(
both
@
6
hrs.)

4.0
mg/
kg
13%,
11%

(@
6
and
2
hrs.)

8.0
mg/
kg
7%,
17%

(@
3
and
6
hrs)

32.0
mg/
kg
24%,
16%

(@
8
and
4
hrs)
No
symptoms
noted.
21
2.

2.
Acute
Dermal
Acute
Dermal
(
1977)

(
1977)­
Part
C
Part
C
Results
of
Arnold
1977
Study:
Part
C
(
High
Temp/
Humidity
 
3
days)

Dose
RBC
ChEI
Symptoms
1.0
mg/
kg
26%,
29%

(@
24
hrs.
on
day
2)
No
symptoms
noted.
22

Study
Strengths

RBC
ChEI
and
clinical
signs
observed

Multiple
dose
used

Frequent
monitoring

High
temp/
humidity
 
worker
exposure
2.

2.
Acute
Dermal
Acute
Dermal
(
1977)

(
1977)
23
2.

2.
Acute
Dermal
Acute
Dermal
(
1977)

(
1977)


Study
Weaknesses

Individual
data
not
fully
reported
(
only
ChE)


2
subjects/
group;
males
only

smoking
 
potential
confounder

RBC/
plasma
ChE
method
 
different

No
rationale
for
dose
selection

Open
design;
no
statistics
24
3.

3.
Acute
Dermal
Acute
Dermal
(
1978)

(
1978)

All
subjects
were
placed
in
a
room
under
high
temp
(
90­
96
°
F)/
high
humidity
(
70­
80%)
conditions
for
the
4
hr
exposure
period.
­

­

2
2
2
2
­

Carbofuran
16
8.0
4.0
2.0
1.0
0.5
0
Dose
(
mg/
kg)

Session
25
3.

3.
Acute
Dermal
Acute
Dermal
(
1978)

(
1978)


Design

Carbofuran
formulation
(
44
%
ai)


50%
test
article
dilution
 
applied
to
upper
back
(
0.5
mg/
cm2)


Mild
exercise
(
0­
4
hrs
postdx)
for
5
min.
then
15
min
rest.
Repeat
cycle
11X
over
4
hrs.
High
temp
and
humidity
conditions.


Test
material
removed;
24
hr.
monitor.
Parameters
­

RBC/
plasma
ChE,
EKG,
BP,
HR,
Temp,
Resp,
pupil
size,
eye
accom,
hematol,
urinalysis,
clinical
signs
26
Results
of
Carbofuran
Data
From
Dermal
Study
(
Arnold
1978)

Dose
RBC
ChEI
Symptoms
0.5
mg/
kg
22%,

7%
One
subject:
nausea
[
at
40
min
and
2
hrs
10
min.
post­
dosing].
The
first
episode
lasted
10
min
and
the
second
about
40
min.

1.0
mg/
kg
29%,

21%

2.0
mg/
kg
42%,

40%
No
symptoms
reported
3.

3.
Acute
Dermal
Acute
Dermal
(
1978)

(
1978)
27
3.

3.
Acute
Dermal
Acute
Dermal
(
1978)

(
1978)

Results
of
Dermal
Study
(
Arnold
1978)­
continued
Dose
RBC
ChEI
Symptoms
4.0
mg/
kg
61%,

49%
­
Both
subjects:
nausea,
dizziness,
and
weakness.

­
One
subject:
vomiting
and
tremors.
Back
washed
and
removed
from
high
temp/
humid
room.

­
Most
symptoms
began
about
3
hrs.
and
disappeared
within
2
hrs
of
onset.

­
In
both
cases
atropine
was
administered
28
3.

3.
Acute
Dermal
Acute
Dermal
(
1978)

(
1978)


Study
Strengths

RBC
ChEI
and
clinical
signs
observed

Multiple
doses
used

Parameters
monitored

High
temp/
humidity
 
worker
exposure
29
3.

3.
Acute
Dermal
Acute
Dermal
(
1978)

(
1978)


Study
Weaknesses

Few
subjects/
group;
males
only;
no
controls

No
dose
selection
rationale

Open
design;
no
statistics
30
Single
Chemical
Single
Chemical
­
Conclusion
Conclusion

Animal
studies
°
ChEI
­
most
sensitive
endpoint
°
Effects
do
not
accumulate
over
time

Human
data
°
ChEI
and
symptoms
°
Consistent
with
animal
observations
°
Oral
&
dermal
human
studies
appropriate
for
PoD
31
NMC
Cumulative
Risk
Assessment
NMC
Cumulative
Risk
Assessment­
Carbofuran
Carbofuran

Brain
ChE
data
of
the
rat
chosen
for
use
in
NMC
CRA
(
supported
by
FIFRA
SAP,
2005)


The
Agency
must
consider
interspecies
extrapolation
(
i.
e.,
animal
to
human)


Rat
ChE
data
indicate
RBC
slightly
more
sensitive
than
brain

Rat
ChE
data
indicate
no
sex
difference

Agency
received
additional
data
that
will
inform
BMD
analyses
32
Carbofuran
Charge
To
The
HSRB
Carbofuran
Charge
To
The
HSRB
Comment
on
the
scientific
evidence
that
supports
the
conclusion
to
use
the
human
studies
for
identifying
a
point
of
departure,
both
oral
and
dermal,
for
the
single
chemical
assessment
and
in
informing
the
interspecies
uncertainty
factor
for
the
cumulative
assessment.
33
BMD
Analyses
for
Carbofuran
BMD
Analyses
for
Carbofuran
Rat
Human
Brain
RBC
RBC
BMD
Analysis
BMD10
(
mg/
kg)
BMDL10
(
mg/
kg)
BMD10
(
mg/
kg)
BMDL10
(
mg/
kg)
BMD10
(
mg/
kg)
BMDL10
(
mg/
kg)

Adult
(
CCA)
0.11
M
0.12
F
0.05
M
0.06
F
­­
­­
­­
­­

Preliminary
Cumulative
RA
0.155
M
0.129
M
0.031
(
M&
F)
0.009
(
M&
F)
­­
­­

Human
Oral
­­
­­
­­
­­
0.038
M
0.025
M
