UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
Date:
January
25,
2005
Subject:
Boric
Acid/
Sodium
Borate
Salts:
Supplement
to
HED
Chapter
of
the
Tolerance
Reassessment
Eligibility
Decision
Document
(
TRED).
PC
Codes:
011001
(
boric
acid),
011102
(
sodium
tetraborate
decahydrate),
011110
(
sodium
tetraborate
pentahydrate),
011112
(
sodium
tetraborate
anhydrous),
011103
(
disodium
octaborate
tetrahydrate),
011107
(
disodium
octaborate
anhydrous),
011104
(
sodium
metaborate).
Case
#
0024,
DP
Barcode
D320894.

To:
Linnea
Hansen,
Risk
Assessor
Health
Effects
Division
Toxicology
Branch
(
7509C)

From:
Jeff
Evans,
Biologist
Health
Effects
Division
Chemistry
and
Exposure
Branch
(
7509C)

Thru:
David
J.
Miller,
Branch
Chief
Health
Effects
Division
Chemistry
and
Exposure
Branch
(
7509C)

This
document
presents
an
additional
exposure
scenario
to
be
included
in
the
Boric
Acid
risk
assessment
dated
January
25,
2006.
The
exposure
scenario
addressed
is
based
on
the
use
of
disodium
octaborate
tetrahydrate
as
a
deck
treatment
to
control
wood
destroying
insects.
An
inhalation
exposure
assessment
was
conducted
for
the
potential
consumer
use
of
the
product
Betanix
®
as
a
deck
spray
application.
It
is
not
clear
from
the
labeling
if
this
is
available
for
use
by
non­
professionals.
A
screening
level
assessment
was
also
conducted
for
childrens'
postapplication
exposure
to
treated
decks
(
non­
dietary
ingestion
due
to
mouthing
behavior).

As
stated
in
the
Boric
Acid
TRED,
the
endpoint
for
assessing
short­
and
intermediate­
term
residential
exposure
was
a
No
Observed
Adverse
Effect
Level
(
NOAEL)
of
8.8
mg
boron/
kg­
day
based
on
reproduction
effects
(
testicular
atrophy)
observed
at
29
mg/
kg­
day
in
both
a
sub­
chronic
(
28
week)
and
chronic
(
2­
year)
study
in
dogs
(
WHO,
1998).
An
uncertainty
factor
of
100
(
10
for
interspecies
extrapolation
and
10
for
intraspecies
variation)
was
used
for
this
assessment
and
therefore,
a
Margin
of
Exposure
(
MOE)
of
100
is
required
for
the
residential
exposure
risk
assessment.
Postapplication
exposure
to
boric
acid
and
its
sodium
salts
was
examined
in
terms
of
hand­
to­
mouth
transfer
for
children.
Application
rates
were
calculated
in
terms
of
pounds
of
active
ingredient
applied
per
square
foot,
based
either
on
product
label
information
or
assumptions
of
application
areas.
Using
the
oral
NOAEL
of
8.8
mg
boron/
kg­
day,
the
MOE
for
children's
non­
dietary
ingestion
is
13.
The
MOE
for
inhalation
exposure
is
98,000.

Dermal
exposures
were
not
included
in
the
assessment
since
there
is
a
low
toxicological
concern
for
dermal
exposure
since
these
compounds
are
so
poorly
absorbed
by
the
skin.
Several
studies
have
shown
that
dermal
absorption
across
intact
skin
is
negligible
in
human
infants
and
adults.

Physical/
Chemical
Properties:

The
physical
and
chemical
properties
of
boric
acid
and
its
sodium
salt
disodium
octaborate
tetrahydrate
(
DOT)
are
provided
in
Table
1.

Table
1.
Physical/
Chemical
Properties
of
Boric
acid
and
its
Sodium
Salt
Chemical
Molecular
formula
Molecular
weight
Physical
state
Melting
point
Solubility
in
water
pH
Density/
Specific
Gravity
Vapor
Pressure
Estimated
Octanol/
Water
Coefficient
Boric
Acid
H3BO3
61.9
Solid
crystalline
powder
171oC
5.6
g/
100mL
5.1
(
1%
solution
at
20oC)
1.51
at
20oC
<
10­
4
torr
at
200C
0.175
Disodium
octaborate
tetrahydrate
Na2B8O13
.

4H20
412.31
Powder
815oC
9.5%
at
20oC
8.5
(
1%
solution
at
23oC)
25­
35
lbs/
ft3
(
specific
gravity)
<
10­
6
torr
No
data
References:
EPA,
1993;
NIOSH,
2001.

Toxic
Endpoint
Selection:

For
this
assessment
of
boric
acid
and
its
sodium
salts,
both
handler
inhalation
and
postapplication
oral
(
specifically
for
children)
and
inhalation
exposures
were
examined.
Dermal
exposures
were
not
included
in
the
assessment
since
there
is
a
low
toxicological
concern
for
dermal
exposure
In
addition,
the
WHO
document
and
the
ATSDR
document
also
state
that
several
studies
have
shown
that
dermal
absorption
across
intact
skin
is
negligible
in
human
infants
and
adults
(
WHO,
1998;
ATSDR,
1992).

Since
there
are
no
inhalation
toxicological
studies
available
in
the
existing
literature,
an
oral
NOAEL
was
used
to
assess
short­
and
intermediate­
term
inhalation
exposure.
The
inhalation
dose
was
conservatively
converted
to
an
equivalent
oral
dose
using
a
100%
inhalation
absorption
factor.
The
oral
toxicological
NOAEL
endpoint
of
8.8
mg
boron/
kg­
day
was
used.
This
NOAEL
was
based
on
reproduction
effects
(
testicular
atrophy)
observed
at
29
mg/
kg­
day
in
both
a
sub­
chronic
(
28
week)
and
chronic
(
2­
year)
study
in
dogs
(
WHO,
1998).
An
uncertainty
factor
of
100
(
10
for
interspecies
extrapolation
and
10
for
intraspecies
variation)
was
used
for
this
assessment
and
therefore,
a
Margin
of
Exposure
(
MOE)
of
100
is
required
for
residential
exposure
risk
assessment.

The
NOAEL
used
in
this
assessment
is
reported
in
boron
equivalents
and
therefore,
doses
calculated
for
boric
acid
and
its
sodium
salts
were
adjusted
to
account
for
the
percent
boron
before
calculation
of
their
respective
MOEs
(
see
Table
4).

Table
2.
Boron
Equivalents
Chemical
Percent
boron
Boric
acid
17.5%

Disodium
octaborate
tetrahydrate
20.96%

Exposure
Assessment:

Residential
handler
inhalation
exposure
and
postapplication
oral
exposure
to
disodium
tetraborate
tetrahydrate
was
examined
for
this
risk
assessment.
The
exposure
scenarios
chosen
for
this
risk
assessment
were
based
on
the
anticipated
use
patterns
and
current
labeling
for
use
to
treat
decks.
It
should
be
noted
that
the
postapplication
non­
dietary
ingestion
exposure
assessment
may
overestimate
exposure
based
on
assumptions
regarding
transferablilty
of
boron
from
treated
wood
surfaces
that
are
meant
to
be
sealed.
Label
directions
specify
that
the
treated
decks
are
to
be
sealed
after
the
DOT
has
dried.
The
extent
to
which
this
sealing
mitigates
boron
transfer
to
childrens'
hands
is
unknown
at
this
time.
Transferable
residue
data
representing
this
use
followed
by
applying
a
sealant
would
help
refine
this
exposure
assessment.
The
estimates
of
exposure
and
risk
for
residential
handler
and
toddler
post
application
exposure
are
presented
in
Table
3
and
4
respectively.
Table
3.
Residential
Handler
Inhalation
Risks
Due
to
Exposure
to
Disodium
Octaborate
Tetrahydrate
While
Treating
Decks
Registration
Number
Exposure
Scenario
Percent
active
ingredient
Assumptions
for
estimating
product
application
rate
Calculations
of
product
application
rate
(
AR)
Application
Rate
Inhalation
Unit
Exposure
from
PHED
Area
Treated
or
Amount
Handled
Dailya
Average
Daily
Dose
(
mg/
kg/
day)
MOEb
72468­
2
Applying
dilute
sprays
to
decks
using
low
pressure
handwand
10
10%
DOT
=
1
lb
ai/
gal/
200
sq
ft
DOT
=
20.96%

boron
1
lb
ai
*
20.96%
boron
=

0.21
lb
boron
applied
0.20
lb/
gal
/
200
sq.
ft
30
µ
g/
lb
ai
handled
200
sq
ft
0.00009
98,000
a
Amount
handled
per
day
values
are
determined
from
the
product
label.

b
Baseline
Inhalation
MOE
=
NOAEL
(
8.8
mg
boron/
kg­
day)
/
adjusted
dermal
daily
dose
(
mg/
kg­
day),
where
adjusted
inhalation
dose
=[
daily
unit
exposure
(
Fg/
lb
ai)
x
application
rate
x
amount
handled
per
day
x
conversion
factor
(
if
needed)
/
body
weight
(
70
kg
adult)]
*
percent
boron.

Table
4.
Toddler
Non­
Dietary
Ingestion
Risks
Due
to
Disodium
Octaborate
Tetrahydrate
Treated
Decks
Registration
number/

Formulation
Application
Rate
a
(
µ
g
ai/
sq
ft)
Percent
available
Percent
active
ingredient
dislodgeable
Surface
area
(
cm2)
Hand
to
Mouth
(
events/
hr)
Extraction
by
Saliva
Exposure
Time
(
hours)
Body
Weight
(
kg)
Deposition
Residue
(
Fg/
cm2)
b
Average
Daily
Dose
(
mg/
kg­
day)
c
MOEd
72468­
2
Deck
spray
462469.8
100%
10%
20
20
50%
1
15
498
0.66
13
a
From
label,
apply
1
gallon
10%
DOT
to
200
ft2:

9.72
lbs
product
*
10%
DOT
*
20.96%
boron
*
454
grams
*
106
µ
g
÷
200
ft2
gallon
pound
gram
b
Surface
residue
(
Fg/
cm2)
=
application
rate
(
lb
ai/
sq
ft)
*
(
conversion
factor
sq
ft/
sq
cm
(
1/
929)).

c
Average
daily
dose
(
mg/
kg­
day)
=
(
Deposition
residue
*
percent
active
ingredient
dislodgeable
*
surface
area
*
Hand
to
mouth
events
*
percent
extraction
by
saliva
*
exposure
time
*
1
mg/
1000
µ
g)/
body
weight.

d
MOE
=
NOAEL
(
8.8
mg
boron/
kg­
day)/
average
daily
dose.
