May
4­
6,
2004
1
PROPOSED
HAZARD
IDENTIFICATION
METHODOLOGY
FOR
ASSESSMENT
OF
DERMAL
SENSITIZATION
RISK
Timothy
F.
McMahon,
Ph.
D
Jonathan
Chen,
Ph.
D.

Office
of
Pesticide
Programs
U.
S.
EPA,
Washington
D.
C.
May
4­
6,
2004
2
Outline
Current
regulatory
approaches
Biology
of
dermal
sensitization
Methods
for
induction
thresholds
Methods
for
elicitation
thresholds
Scientific
uncertainty
Populations
of
concern
May
4­
6,
2004
3
Acknowledgements
Norm
Cook
(
OPP)

Nader
Elkassabany,
Ph.
D.
(
OPP)

Timothy
Leighton
(
OPP)

William
Jordan
(
OPP)

Winston
Dang,
Ph.
D.
(
OPP)

Denise
Sailstad,
Ph.
D.
(
ORD)

Michele
Burgess,
Ph.
D.(
OSWER)

Lee
Hoffman,
Ph.
D.,
D.
A.
B.
T
(
OSWER)

Joseph
Merenda
(
OSCP)

Karen
Hamernik,
Ph.
D.
(
OSCP)

Nancy
Chiu,
Ph.
D.
(
OW)
May
4­
6,
2004
4
°
USEPA,
§
40
CFR
798.4100:

"
Information
derived
from
tests
for
skin
sensitization
serves
to
identify
the
possible
hazard
to
a
population
repeatedly
exposed
to
a
test
substance."

°
USFDA:
FFDCA
Section
601
(
cosmetics)

Prohibits
distribution
of
cosmetics
in
interstate
commerce
which
are
adulterated
or
misbranded.
A
cosmetic
is
considered
adulterated
if
it
contains
a
substance
which
may
make
the
product
harmful
or
injurious
to
consumers
under
customary
conditions
of
use.

DERMAL
SENSITIZATION­
CURRENT
APPROACHES
May
4­
6,
2004
5
°
USFDA
cosmetics
cont.

If
tests
are
needed
to
determine
dermal
sensitization
potential,
classical
animal
tests
or
in
vitro
lternatives
are
used.

°
USFDA:
drugs
In
published
guidance,
the
Buehler
and
GPMT
tests
are
cited
as
reliable
assays
for
determining
the
sensitization
potential
of
topically
applied
drugs.
The
LLNA
is
cited
as
a
"
quantitative
rather
than
essentially
subjective"
test.

DERMAL
SENSITIZATION­
CURRENT
APPROACHES
(
Continued)
May
4­
6,
2004
6
DERMAL
SENSITIZATION­
CURRENT
APPROACHES
(
Continued)

°
CPSC
1500.3(
b)(
9)

Before
designating
any
substance
as
a
strong
sensitizer,
the
Commission,
upon
consideration
of
the
frequency
of
occurrence
and
severity
of
the
reaction,

shall
find
that
the
substance
has
a
significant
potential
for
causing
hypersensitivity.

To
determine
whether
a
substance
is
a
  
strong'`

sensitizer,
the
Commission
considers
the
available
data
for
a
number
of
factors,
including
but
not
limited
to
"
the
result
of
experimental
assays
in
animals
or
humans
(
considering
dose­
response
factors),
with
human
data
taking
precedence
over
animal
data."
May
4­
6,
2004
7
A
registered
pesticide
is
incorporated
into
an
article
to
protect
the
integrity
of
the
article
or
substance
itself.

Treated
articles
such
as
treated
wood
do
not
bear
pesticide
labels
or
other
communication
methods
to
inform
the
public
about
potential
hazards,
including
dermal
sensitization.
Treated
Articles
May
4­
6,
2004
8
EPA's
Office
of
Pesticides
Programs
(
OPP)
is
seeking
expert
advice
on
how
to
evaluate
general
population
exposure
to
a
pesticide
that
is
recognized
to
cause
dermal
sensitization.
Specifically,
the
Agency
is
interested
in
better
understanding
how
such
exposures
may
induce
sensitization
in
the
general
population
and
how
to
establish
criteria
to
protect
against
unacceptable
dermal
reaction.

The
Agency
is
also
seeking
guidance
from
the
SAP
on
how
such
exposures
impact
individuals
already
sensitized.

ISSUE
BEFORE
THE
SAP
PANEL
May
4­
6,
2004
9
Allergic
Contact
Dermatitis
(
ACD)

Contact
Hypersensitivity
Contact
Allergy
Delayed
Contact
Hypersensitivity:

 
A
delayed,
immunologically
mediated
inflammatory
skin
disease
consisting
of
various
degrees
of
erythema,

edema,
and
vesiculation. 
(
Marzulli
and
Maibach,
1996)

 
stimulation
by
chemical
allergen
(
in
an
inherently
susceptible
individual)
of
an
immune
response
of
the
quality
and
vigor
required
to
permit
the
provocation
of
an
elicitation
reaction
upon
subsequent
encounter
with
the
same
chemical. 
(
Kimber,
2004)
May
4­
6,
2004
10
Allergic
Contact
Dermatitis
Characterized
by
two
phases:

Induction:


An
exposure
of
sufficient
magnitude
and/
or
duration
to
activate
specific
immune
mechanisms
resulting
in
the
acquisition
of
sensitization
Elicitation/
challenge
:


Responses
induced
in
sensitized
individuals
upon
exposure
to
the
allergen
by
a
relevant
route.
May
4­
6,
2004
11
Dermal
Irritation
vs.
ACD
Edema
Erythema
Reaction
time:

immediate
Response
on
1st
exposure
No
immune
memory
Edema
Erythema
Reaction
time:
24
 
72
hrs
No
response
on
1st
exposure
Requires
immune
memory
Irritation
Irritation
ACD
ACD
INDUCTION
ELICITATION
LOW
MOLECULAR
WT
ALLERGEN
MIGRATION
TO
LOCAL
LYMPH
NODE
IL­
1
 ,
IL­
6,
IL­
12
IL­
1
 ,

TNF­
 ,

GM­
CSF
T­
CELL
LYMPHOCYTE
PROLIFERATION
ICAM­
1
LANGERHANS
CELL
(
LC)
"
PRIMED"
LYMPHOCYTES
SPECIFIC
INFLAMMATORY
RESPONSE
CYTOKINES,
COSTIMULATORY,

ADHESION
MOLECULES
INCREASE
CELLULAR
INFLUX
EDEMA
AND
ERYTHEMA
Contact
Hypersensitivity*

Reprinted
with
permission
from
Sailstad,
2003
May
4­
6,
2004
13
°
ACD
is
generally
recognized
as
a
threshold
phenomenon,
i.
e.

below
a
certain
concentration,
ACD
will
not
be
expected
to
occur.

°
However,
thresholds
are
largely
determined
by
the
potency
of
the
allergen,
and
induction/
elicitation
thresholds
vary
mongIndividuals
(
Kimber
et
al.,
2003)
Dose­
response
relationships
are
observed
for
both
induction
and
elicitation
(
Scott
et
al.,
2002).

°
In
addition,
induction
of
ACD
may
occur
after
a
single
exposure,
after
contact
with
a
sufficiently
large
area
of
skin,
or
as
a
consequence
of
repeated
skin
exposures
(
Marzulli
and
Maibach.,
1996).
In
some
cases
(
i.
e.
DNCB)
a
single
contact
can
be
sufficient
for
sensitization
(
Griem
et
al.,
2003).

Allergic
Contact
Dermatitis
(
Continued)
May
4­
6,
2004
14
METHODS
Contact
Hypersensitivity
Animal
Models
for
Hazard
ID
GPMT
and
Buehler
Test
GPMT
GPMT
ID
injection
w/
and
without
ID
injection
w/
and
without
FCA
FCA
plus
topical
application:

plus
topical
application:

Days
0
and
Days
5
Days
0
and
Days
5­
8
Day
20
Day
20­
22
topical
challenge
22
topical
challenge
Read
Read:
24,48
h
after
challenge
:
24,48
h
after
challenge
Topical
application
Topical
application
­
closed
closed
patch:

patch:

Days
0,
6
Days
0,
6­
8,
and
13
8,
and
13­
15
15
Day
27
Day
27­
28
topical
challenge
28
topical
challenge
of
the
untreated
flank
for
6
h
of
the
untreated
flank
for
6
h
Read
Read:
24,48
h
after
:
24,48
h
after
removing
patch
removing
patch
BT
BT
Induction
Induction
Challenge
Challenge
Endpoint
Endpoint
May
4­
6,
2004
16
Animal
Models
for
Hazard
ID
The
Buehler
test
and
the
maximization
test
are
best
suited
for
providing
information
on
whether
a
substance
is
a
skin
sensitizer
or
not.
The
Local
Lymph
Node
Assay
(
LLNA)
is
a
more
recent
method
for
assessing
the
induction
phase
of
sensitization.
Local
Lymph
Node
Assay
Days
1,
2
&
3
Apply
Sensitizer
Day
6
­
Inject
H­
Thymidine
3
5
h
Make
Cell
Suspension
Determine
H­
Thymidine
Incorporation
by
Liquid
Scintillation
Counting
3
Reprinted
with
permission
From
Sailstad,
2003.
May
4­
6,
2004
18
Local
Lymph
Node
Assay
(
LLNA)

As
an
alternative
to
traditional
tests,
the
LLNA
provides:


Potential
for
determining
a
NOAEL

Use
of
fewer
animals

Evaluation
of
induction
phase

Biological
basis
for
the
endpoint
of
concern

Extensive
assay
data
available
May
4­
6,
2004
19
LLNA
cont.

The
Immunotoxicity
Working
Group
of
ICCVAM
in
1999
recommended
the
LLNA
as
a
stand­
alone
alternative
for
contact
sensitization
hazard
provided
certain
protocol
modifications
were
made
At
that
time
the
ICCVAM
IWG
considered
that
the
LLNA
was
not
appropriate
for
certain
classes
of
chemicals,
including
metals,
strong
irritants,
and
aqueous
soluble
materials.
May
4­
6,
2004
20
LLNA
cont.

In
2001,
the
FIFRA
SAP
agreed
with
the
Agency
proposal
that
the
LLNA
was
applicable
for
testing
chemicals
for
contact
sensitization
and
should
be
considered
a
preferred,

standalone
assay.

The
SAP
also
noted
that
expanding
application
of
the
LLNA
to
metals,
strong
irritants,
and
aqueous
soluble
materials
should
be
considered
based
on
additional
data
published
since
the
1999
ICCVAM
peer
review.
May
4­
6,
2004
21
INDUCTION
THRESHOLDS
­
METHODS
Approaches
for
quantitative
determination
of
induction
thresholds
have
been
published
using
LLNA
data
(
Gerberick
et
al.,
2001;
Felter
et
al.,
2003;

Griem
et
al.,
2003).

As
reviewed
by
Felter
et
al.
(
2003),

Gerberick
et
al.
(
2001)
proposed
a
methodology
for
derivation
of
a
`
sensitization
reference
dose'
(
S­
RfD)
May
4­
6,
2004
22
This
method
employs
the
same
fundamental
concepts
of
a
risk
assessment,
i.
e.
hazard
identification,

doseresponse
assessment,
exposures
assessment,
and
risk
characterization.

Hazard
is
first
identified
from
the
available
data,

Including
animal
and
human
test
results.
May
4­
6,
2004
23
Gerberick
et
al.
2001
Dose­
response
is
then
done
using
a
weight­
of­
evidence
approach,
in
which
chemicals
can
be
categorized
into
potency
classes.
For
each
potency
class,

a
`
default
NOAEL'
is
assigned,
as
available
NOAELs
in
the
literature
do
not
have
a
high
degree
of
precision.
May
4­
6,
2004
24
Gerberick
et
al.,
cont.

May
4­
6,
2004
Hazard
Assessment
 
Murine
LLNA
data
­

Default
NOAEL
for
Use
in
Risk
Assessment
­
Gerberick
(
2000,
2001)

1

10
Potent

10
1,000
1000
 
10,000
Weak
1000
 
10,000
10
10
­
100
Strong
10
 
100
100
100
­
1000
Moderate
100
 
1000
10,000
>
10,000
Extremely
Weak
>
10,000
NA
NC
Non­
Sensitizing
NC
Default
NOAEL
(

g/
cm2)

Experimental
Human
NOAEL
(

g/
cm
2)

Sensitization
Potential
A
LLNA
EC3
(

g/
cm2)

NC
=
Not
Calculated,
No
Positive
response
is
obtained
at
any
concentration
tested.
An
EC3
value
cannot
be
calculated.

NA
=
Not
Applicable.
The
Material
is
non­
sensitiser.
A
default
NOAEL
is
not
needed
for
risk
assessment.
May
4­
6,
2004
25
Uncertainty
factors
are
then
considered
to
account
for:


Intra­
species
variation
(
age,
genetic
factors,
skin
integrity)


Vehicle
or
product
matrix
effects
(
e.
g.,
soil,
wood)


Exposure
considerations
(
formulations,
repeated
exposures)


Maximum
UF
for
each
area
is
10,
with
a
maximum
UF
of
1000

No
inter­
species
extrapolation
UF,
as
LLNA
data
are
currently
used
only
for
potency
classification
and
not
for
determination
of
an
actual
NOAEL.

Gerberick
et
al.,
cont.
May
4­
6,
2004
26
Gerberick
et
al.,
cont.

S­
RfD
=
Default
NOAEL
uncertainty
factor
Comparison
of
S­
RfD
to
calculated
exposure
to
Determine
a
Margin
of
Safety
Principle
could
be
potentially
be
applied
to
induction
and/
or
elicitation
May
4­
6,
2004
27
Griem
et
al.
(
2003)

Proposed
an
an
approach
to
derive
a
`
safe
area
skin
dose'
for
induction
based
on
use
of
LLNA
data.
Comparison
was
made
between
EC3
values
from
LLNA
tests
and
NOAEL/
LOAEL
values
from
HRIPT
or
HMT
tests
for
known
human
sensitizers.
May
4­
6,
2004
28
Griem
et
al
(
2003)
cont.
May
4­
6,
2004
29
Uncertainty
factors
were
then
applied
for
derivation
of
safe
area
Induction
doses
Interspecies
extrapolation
UF
of
3x
Intraspecies
variability
UF
of
10x
10x
to
account
for
a
possible
higher
inducing
potency
of
a
chemical
upon
repeated
exposure
Division
of
the
LLNA
EC3
by
the
total
UF
of
300
results
in
an
area
dose
which
"
should
not
induce
sensitization
in
the
vast
majority
of
humans."

Griem
et
al.
(
2003)
Cont.
May
4­
6,
2004
30
Elicitation
thresholds­
Methods
Methods
have
also
been
proposed
for
determination
of
concentrations
or
safe
area
doses
for
protection
against
elicitation
in
sensitized
individuals.
By
inference,
protection
against
elicitation
would
also
be
protective
of
induction,

as
thresholds
for
induction
are
generally
higher
than
those
for
elicitation
(
Kimber
et
al.,
2003)
May
4­
6,
2004
31
Griem
et
al.
(
2003)

Theoretically,
a
correlation
should
be
expected
between
Sensitizing
and
elicitation
potency
of
a
chemical
However,
elicitation
thresholds
have
been
determined
for
only
a
small
number
of
sensitizers.

Comparison
of
sensitization
and
elicitation
area
doses
showed
no
obvious
correlation.

ELICITATION
THRESHOLDS­
METHODS
May
4­
6,
2004
32
Griem
et
al.
(
2003)
cont.
May
4­
6,
2004
33
Griem
et
al
(
2003)
cont.

Relevant
for
assessing
elicitation
is
the
ratio
of
the
induction
to
elicitation
threshold.
A
linear
correlation
was
used
to
describe
the
relationship
between
log(
induction/
elicitation
threshold
ratio)
and
log(
elicitation
threshold).

Based
on
this,
it
is
proposed
that
the
induction/
elicitation
threshold
ratio
can
be
predicted
on
the
basis
of
an
established
induction
threshold.
Griem
et
al.,
2003
May
4­
6,
2004
35
Uncertainty
factors
for
derivation
of
the
safe
area
dose
for
elicitation
­
Griem
et
al.
2003
(
cont.)

When
based
upon
the
EC3
induction
threshold
from
an
LLNA,
the
total
UF
=
300
(
3x
interspecies,
10x
intraspecies,
10x
repeated
exposure)

When
based
upon
a
NOAEL/
LOAEL
from
one
time
HRIPT
or
sensitization
potency
from
LLNA,
total
UF
=

100­
1000
(
10x
interspecies,
10x
intraspecies,
3­
10x
LOAEL
to
NOAEL),
plus
inclusion
of
variable
UF
based
on
induction/
elicitation
ratio.
May
4­
6,
2004
36
Uncertainty
factors
for
derivation
of
the
safe
area
dose
for
elicitation
­
Griem
et
al.
SAP
Comment
To
an
EC3
value
of
8.8
ug/
cm
2
were
applied
Uncertainty
factors
of:

1x
interspecies
10x
intraspecies
10x
time
(
repeated
exposure)

15x
Induction/
elicitation
factor
Total
UF
=
1500
`
safe
area
dose
for
Cr(
VI)
=
8.8/
1500
=
0.006
ug/
cm
2
May
4­
6,
2004
37
Griem
et
al.,
2003
(
cont.)

To
a
benchmark
value
of
0.05
ug/
cm
2
from
human
patch
test
data
were
applied
uncertainty
factors
of:

10x
intraspecies
3x
time
(
repeated
exposure)

Total
UF
=
30
`
safe
area
dose'
=
0.05/
30
=
0.002
ug/
cm
2
May
4­
6,
2004
38
MET
Approach
Minimum
Elicitation
Threshold
Based
on
the
concept
that
there
is
an
`
elicitation
threshold'

Below
which
sensitization
is
not
expected
MET
usually
derived
from
tests
in
sensitized
individuals
Uniform
scientific
criteria
for
establishing
the
MET
are
not
yet
established,
i.
e.
what
is
the
appropriate
response
Level
(
5%?
10%?).
Further,
it
is
not
known
whether
this
concept
can
be
applied
to
all
chemical
sensitizers.
May
4­
6,
2004
39
Uncertainty
factors
May
4­
6,
2004
40
Areas
of
Uncertainty
Inter­
species
extrapolation
Intra­
species
variation
Product
matrix
effects
Exposure
considerations
May
4­
6,
2004
41
Inter­
species
extrapolation
Intended
to
account
for
differences
in
response
between
animals
and
humans
Griem
et
al.
(
2003)
reported
that
sensitizing
area
doses
are
similar
for
murine
LLNA
and
human
data;

therefore,
the
inter­
species
factor
may
be
less
than
10
May
4­
6,
2004
42
Inter­
species
factor,
cont.

Not
all
proposals
use
this
factor
Felter
et
al.
(
2003)
recognizes
this
factor
but
also
recognizes
that
the
murine
LLNA
has
not
been
yet
used
for
derivation
of
a
NOAEL
for
use
in
quantitative
assessment
May
4­
6,
2004
43
Intra­
species
variation
A
10x
factor
is
proposed
to
account
for
variability
based
on
age
(
children
vs.

adults),
race,
sex,
and
genetic
make­
up
(
Gerberick
et
al.,
2001;
Griem
et
al.,

2003;
Felter
et
al,
2002).
May
4­
6,
2004
44
Product
Matrix
Effects
Range
of
of
1­
10x
proposed
(
Gerberick
et
al.,
2001;
Felter
et
al.,
2002)

Accounts
for
exposure
to
the
contact
allergen
in
the
product
matrix
vs.
results
from
experimental
studies
Various
components
of
the
product
may
affect
sensitizing
potency
of
the
allergen,
e.
g.

dermal
irritation
can
increase
the
sensitizing
potency.

Smaller
factors
may
be
considered
for
mild
formulations.
May
4­
6,
2004
45
Exposure
Variables
Uncertainty
factor
proposed
(
1­
10x)
to
account
for:


Site
of
the
body
exposed

Repeated
exposures

Bioavailability
in
matrix
(
soil/
wood/
patch)
May
4­
6,
2004
46
Populations
of
Concern
Non­
sensitized
individuals
Sensitized
individuals
Relative
susceptibility
of
children
vs.

adults
(
Paustenbach
et
al.,
1992;
Felter
et
al.
2003;
Wohrl
et
al.,
2003)
May
4­
6,
2004
47
Worhl
et
al.,
2003
May
4­
6,
2004
48
Worhl
et
al.,
2003
May
4­
6,
2004
49
End
