Page
1
of
15
UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
April
14,
2004
MEMORANDUM
SUBJECT;
Environmental
Fate
Science
Chapter
on
Zinc
Pyrithione
(
Zinc
Omadine
®
)
For
Reregistration
Eligibility
Document
(
RED)

To:
Deborah
Smegal
Science
Coordinator
for
Zinc
Pyrithione
RED,
Risk
Assessment
and
Science
Support
Branch
Antimicrobials
Division(
7510C)

From:
A.
Najm
Shamim,
Ph.
D.,
Chemist
Regulatory
Management
Branch
II
Antimicrobials
Division
(
7510C)

Thru:
Connie
Welch,
Chief
Regulatory
Management
Branch
Antimicrobials
Division
(
7510C)

A.
I.
Chemical
Name:
Zinc­
2­
pyridinethiol­
1­
oxide
DP
Barcode:
301372
Registrant:
Arch
Chemicals,
Inc.

PC
Code:
088002
Attached
is
the
Science
Chapter
on
the
Environmental
Fate
Assessment
of
Zinc
Pyrithione
(
Zinc
Omadine
®
)
for
the
Reregistration
Elegibility
Decision
(
RED).
This
document
was
peer
reviewed
by
Bob
Quick.
Concurrence
and
sign­
off
are
requested.
Page
1
of
15
ZINC
OMADINE:
ENVIRONMENTAL
FATE
SCIENCE
CHAPTER
Executive
Summary
Zinc
Pyrithione
(
Zinc
Omadine
®
)
appears
hydrolytically
stable
in
abiotic,
buffered
and
simulated
water
systems
with
an
extrapolated
half
life
between
99,
120
and
123
days
in
buffered
medium
and
96
days
(
extrapolated)
in
simulated
sea
water.
Photolytically,
however,
it
rapidly
degrades
with
a
half
life
of
13
minutes
in
buffered
aqueous
medium
and
17
minutes
in
simulated
sea
water.
It
may
not
pose
a
concern
for
surface
water
run­
off.

There
are
multiple
degradation
pathways
for
zinc
pyrithione
Under
aerobic
conditions,
zinc
pyrithione
degradation
half
life
is
0.6
hours
in
aqueous
system
and
0.89
days
in
sediment.
Similarly
zinc
pyrithione
shows
a
tendency
of
degrading
anaerobically
in
water
within
0.5
hours
and
in
about
19
hours
in
sediments.
It
may
not
be
a
concern
for
ground
water
contamination.

Zinc
pyrithione
shows
a
moderately
strong
tendency
to
bind
with
soils
and
sediments:
With
salt
water
soil
and
sediment
its
Kds
are
50
and
99
respectively.
Tendency
to
bind
with
freshwater
soils
and
sediments
are
less
strong
and
observed
Kds
are
11
and
48
respectively.
There
may
be
a
short­
lived
water/
sediment
partitioning
issue.
There
could
be
an
acute
adverse
impact
on
benthic
aquatic
organisms.
However,
since
it
degrades
fairly
quickly
in
freshwater
and
saltwater
soils
and
sediments
(
half
lives
0.89
days
to
19
hours),
the
acute
adverse
impact
may
be
very
short­
lived.
It
is
not
likely
to
persist
in
water
and
microbial
soils
and
sediments.

Reported
Octanol/
Water
Partition
coefficient
KOW
is
<
1000,
and
therefore
zinc
pyrithione
is
not
likely
to
bioaccumulate
in
aquatic
organisms
(
fish
etc.)

I.
Environmental
Fate
Assessment
A.
Abiotic:

Zinc
pyrithione,
in
a
30
day
study
appears
hydrolytically
stable
under
abiotic
and
buffered
conditions
at
pHs
5,
7,
and
9.
The
extrapolated
hydrolytic
half
life
was
99,
120
and
123
days.
In
simulated
sea
water
system
(
pH
8),
its
hydrolytic
half
life
was
extrapolated
at
96
days.

Photolytic
studies
conducted
in
a
buffered
aqueous
system
and
pH
9,
zinc
pyrithione
rapidly
degraded
with
a
half
life
of
13
minutes
and
at
the
same
pH
and
in
a
simulated
sea
water
system,
zinc
pyrithione
degraded
in
17
minutes.
It
does
not
appear
to
be
stable
on
surface
water.
Page
2
of
15
B.
Biotic:

In
a
study
on
aerobic
aquatic
system,
zinc
pyrithione
degradation
follows
a
biphasic
process
and
in
the
first
phase
it
degrades
rapidly
with
a
half
life
of
0.065
hours
in
salt
water
and
in
1.3
hours
in
fresh
water
samples.
In
the
second
phase,
zinc
pyrithione
degradation
half
life
was
365
hours
(
15
days)
in
salt
water
samples
and
in
fresh
water
samples
it
degraded
in
298
hours
(
about
12.3
days).

A
second
aerobic
aquatic
degradation
study
was
conducted
on
a
salt
water
harbor
used
as
a
boat
maintenance
site.
Degradation
data
were
obtained
on
zinc
and
copper
pyrithiones.
Degradation
half
lives
were
extracted
by
using
a
two­
compartment
model
(
water/
sediment).
Half
lives
were
determined
for
water
and
sediment
samples
separately.
In
water
samples,
and
in
the
presence
of
pyrithione
thiosulfate
(
OTS,
which
may
be
formed
as
a
degradate
or
may
be
present
in
the
sample),
the
half
life
was
0.60
hours.
Degradation
half
life
in
the
sediment
samples,
in
the
presence
of
OTS,
was
0.89
days,
(
OTS
may
be
initially
present
or
may
be
formed
due
to
degradation
process.
Kinetic
pathway
in
the
sediment
samples
was
non­
linear.
In
the
absence
of
OTS,
and
through
non­
linear
pathway,
the
degradation
half
life
decreased
to
0.03
days.
The
sediment
in
this
study
was
characterized
as
sand
(%
sand
=
90,
silt:
4%
and
clay:
6%)

In
anaerobic
aquatic
samples
from
fresh
and
salt
water,
zinc
pyrithione
degraded
through
biphasic
process.
Anaerobically
fresh
water
and
salt
water
samples
of
zinc
pyrithione
degraded
rapidly
in
the
first
phase
with
a
half
life
of
about
2
hours.
In
the
second
phase,
the
degradation
half
life
in
fresh
and
salt
water
samples
increased
to
25.5
hours.
Fresh
water
and
salt
sediment
samples
,
zinc
pyrithione
degradation
half
was
measured
at
13.1
hours.

In
a
second
study,
water
and
sediment
samples
collected
from
a
salt
marina
(
Little
Harbor,
MarbleHead,
MA).
Two
compartment
model
was
used
to
analyze
the
kinetic
data:
zinc
pyrithione
degraded
in
0.50
hours
in
water
sample
and
in
18.9
hours
in
the
sediment
sample.
The
sediment
of
this
marina
was
characterized
as
sand
(
%
sand
=
86,
silt:
6%,
and
clay:
8%).
pH
of
the
sediment
was
basic
(
7.9)
and
%
organic
C
=
2.3.

A
soil
column
leaching
study
conducted
on
four
soil
samples:
sand,
sandy
loam,
loam
and
clay
(
unaged)
and
on
sandy
loam
(
aged)
indicated
that
zinc
pyrithione
is
immobile
in
these
systems.

An
absorption/
desorption
study
conducted
on
Marblehead
salt
water
soil,
Marblehead
salt
water
sediment,
Portland
freshwater
soil
and
Portland
freshwater
sediment
(
all
from
MA),
showed
that
zinc
pyrithione
binds
moderately
strongly
with
Marble
saltwater
soil
and
sediment
(
K
d=
50
and
99
respectively)
and
less
strongly
with
Portland
freshwater
soil
and
sediment
(
K
d
=
11
and
48).
Marblehead
salt
water
soil
and
sediment
were
characterized
as
sandy
loam
and
Portland
freshwater
soil
and
sediment
as
loamy
or
silt
loam.

An
outdoor
Microcosm
study
submitted
by
registrants
is
not
required
by
environmental
Page
3
of
15
fate
data
requirements.
This
study
was
found
deficient
in
many
ways.
However,
OPP
has
reviewed
it
and
has
retained
as
supplemental
study.
The
study
does
indicate
that
zinc
pyrithione
degrades
under
simulated
seawater
conditions,
under
dark
or
in
the
presence
of
light.
The
half­
lives
under
all
conditions
were
less
than
twenty
four
hours.

For
use
of
zinc
pyrithione
as
an
antifoulant
paint
on
small
boat
and
ship
bottoms
a
special
study
called
Aqueous
Availability
study
which
measures
the
rate
of
leaching
when
boats
and
ships
painted
with
the
Antifoulant
paint
navigate
in
fresh
or
salt
water
bodies
(
marinas,
or
lakes
or
sea)
,
a
number
of
aqueous
availability
studies
were
conducted
on
a
number
formulations
containing
zinc
pyrithione
and
in
some
cases
zinc
pyrithione
and
another
biocide.
The
percent
of
zinc
pyrithione
in
the
formulations
varied
from
2.0
to
4.7
and
the
average
leach
rate/
day
ranged
from
1.2
µ
g/
cm2/
day
to
8.4
µ
g/
cm2/
day.
These
were
non­
guideline
studies
and
aqueous
availability
studies
were
carried
by
using
the
EPA
approved
ASTM
Method
D
5108­
90.

The
Octanol/
Water
Partition
Coefficient
(
K
OW)
of
zinc
pyrithione
is
reported
to
be
less
than
1000
which
makes
it
less
likely
to
bioaccummulate
in
aquatic
organisms,
although
because
of
moderately
high
K
d
s
with
salt
water
sediments
it
may
and
partition
in
water
and
become
available
to
benthic
organisms.

Coordination
or
complex
substances
like
zinc
pyrithione
have
a
tendency
to
transmetallate
with
other
metals
present
in
aquatic
media
(
copper,
mercury,
cadmium
and
other
metal
ions).
Copper
pyrithione
is
shown
to
be
more
stable
than
zinc
pyrithione.
However,
it
also
degrades
with
comparable
rates
as
zinc
pyrithione
in
the
aerobic
and
environmental
media
of
water
and
sediments.

Appendix
Environmental
Fate
Data
For
Zinc
Pyrithione
A.
Environmental
Fate
Guideline
Studies:

Olin
Corporation
originally
submitted
the
required
guideline
studies
for
environmental
fate
assessment.
The
studies
were
aimed
at
fulfilling
the
requirements
for
zinc
pyrithione's
use
as
an
antifoulant.
The
Agency
has
decided
to
use
these
environmental
fate
studies
for
fate
assessment
of
zinc
pyrithione
to
fulfill
the
reregistration
requirements.
Arch
Chemicals,
Inc.
is
now
actively
seeking
reregistration
for
zinc
pyrithione.

1.
Hydrolysis
(
Guideline
number:
161­
1,
MRID
#:
438646­
02)

This
study
was
reviewed
by
the
Agency,
was
found
acceptable,
and
has
satisfied
the
hydrolysis
data
requirement
for
zinc
pyrithione.

The
hydrolysis
study
was
conducted
in
sterile
buffered
solutions
on
radiolabelled
zinc
pyrithione
(
14C
attached
in
the
pyridine
ring
at
2,
6
positions
of
the
molecule)
at
an
application
rate
of
2
ppm
Page
4
of
15
in
aqueous
solutions
at
pH
5,
7
and
9
as
required
by
the
guideline.
The
percent
purity
of
the
test
substance
was
determined
to
be
97%.
The
same
study
was
also
conducted
in
simulated
sea
water
at
pH
8.2.
A
cosolvent
of
less
than
1%
(
dimethyl
sulfoxide)
was
also
present
in
the
system.
The
study
was
carried
out
at
25
±
1o
C
in
the
dark.
The
samples
were
analyzed
on
day
0,
3,
7,
14,
21
and
30
after
the
study
was
initiated
by
Liquid
Scintillation
counting
(
LSC)
and
high
performance
liquid
chromatography
(
HPLC)
with
radiometric
detection
and
thin
layer
chromatography
(
TLC).

The
percent
recoveries
of
radiolabelled
parent
compound
and
a
hydrolytic
transformation
product
at
pH
5,
7,
9
and
8.2
(
saline
water)
were
100.6,
96.6,
101.2
and
98.1.
The
analysis
on
samples
at
pH
5
and
7
on
day
30
showed
the
presence
of
a
major
transformation
product
identified
as
Pyrithione
disulfide
and
this
product
accounted
for
21.23%
at
pH
5
(
76.8%
for
the
parent)
and
16.3%
at
pH
7
(
80.0%
for
the
parent).
Two
minor
transformation
products
were
observed
and
accounted
for
<
3%
of
the
total
radioactivity
at
pH
5
and
one
transformation
product
at
pH
7
accounted
for
<
3.3%
of
the
radioactivity.

At
pH
9,
the
30
day
sample
showed
the
presence
of
the
parent
compound
and
accounted
for
82.8%.
Six
transformation
products
were
also
identified.
The
major
transformation
product
identified
was
pyrithione
sulfinic
acid
at
11.6%
Pyrithione.
Pyrithione
disulfide
was
detected
at
4.3%
on
day
1
and
it
declined
to
1.8%
on
day
30.
Other
transformation
products
never
exceeded
2.9%
over
the
entire
period
of
study.

In
this
study,
the
half
lives
at
pH
5,
7
and
9
were
extrapolated
at
:
99,
120
and
123
days.

In
the
simulated
sea
system
(
pH
8.2),
the
parent
compound
accounted
for
76.1%
of
the
total
radioactivity.
Five
transformation
products
were
identified
and
two
of
them
were
the
same
as
found
in
the
other
media,
pyrithione
disulfide
and
pyrithione
sulfinic
acid.
By
day
30,
pyrithione
disulfide
was
at
2.4%.
Pyrithione
sulfinic
acid
reached
a
maximum
of
17.3%
of
the
total
applied
radioactivity.
All
other
transformation
products
never
exceeded
2.4%
of
the
applied
radioactivity.
The
major
transformation
product
pyrithione
sulfinic
acid
was
identified
by
using
a
host
of
analytical
techniques
including
LC­
MS
with
electron
spray
mode.

Degradation
of
zinc
pyrithione
was
slow
in
simulated
sea
water
(
pH
8.2)
and
the
extrapolated
half
life
was
96
days.
The
percent
recovery
in
the
simulated
water
system
was
98.1%
while
for
the
sterile
buffered
system
the
percent
recoveries
were:
100.6,
96.5
and
101.2
at
pHs
5,
7
and
9
respectively.

2.
Photolysis
in
Water
(
Guideline
number
161­
2,
MRID
#:
440115­
01)

This
study
was
reviewed
by
the
Agency,
was
found
acceptable,
and
satisfies
the
photolysis
in
water
data
requirements
for
zinc
pyrithione.

Radiolabelled
zinc
pyrithione
(
14C
at
positions
2
and
6
in
the
pyridine
ring)
was
investigated
for
photolytic
stability
in
buffered
water
at
pH
9
and
also
in
simulated
sea
water
with
light
and
dark
Page
5
of
15
cycles
(
about
12
for
each
duration).

The
study
was
conducted
at
an
application
rate
of
2
ppm
in
the
presence
of
simulated
sunlight
(
xenon
arc
lamp,
Wave­
length
range:
330­
88
nm
and
average
light
flux
for
the
lamp
was
154.5
watts
per
square
meter
(
W/
m2)
)
at
25
±
1
oC.
Cosolvents
in
this
study
were
acetonitrile
and
dimethyl
sulfoxide.

Samples
were
analyzed
at
0,
1,
3,
5,
and
15
minutes
and
at
1,6,
and
24
hours
and
at
14
and
30
days
after
the
study
commenced.
The
analytical
techniques
used
for
the
analysis
of
the
parent
and
the
transformation
products
were
Liquid
Scintillation
Counting
(
LSC),
high
performance
liquid
chromatography
(
HPLC)
and
thin­
layer
chromatography
(
TLC).
Average
percent
recovery
for
samples
and
the
controls
in
the
sterile
buffered
medium
was
101.8%
at
pH
9
and
the
percent
recovery
was
102.1%
for
the
simulated
sea
water
samples.

At
pH
9,
zinc
pyrithione
was
97.99%
level
of
the
total
radioactivity
at
the
start
of
the
study
(
zero
time)
and
the
percent
radioactivity
declined
to
32.9%
in
15
minutes
and
within
an
hour
the
percent
radioactivity
attributable
to
the
parent
compound
declined
to
less
than
5%.
Fourteen
transformation
products
were
identified
and
five
of
them
were
more
than
10%
of
the
applied
radioactivity:
three
transformation
products
showed
applied
radioactivity
over
5%
and
the
rest
of
the
transformation
products
were
below
5%
level.

In
all,
fourteen
degradates
formed
in
sterile
medium
and
all
of
them
were
identified.
Only
three
degradates
D6,
D7
and
D8
reached
levels
higher
than
10%.
D6
and
D7
reached
a
level
of
13.6%
and
45%
respectively
in
over
an
hour
and
declined
thereafter.
D8,
on
the
other
hand,
reached
a
level
of
63%
after
six
hours
and
remained
at
74%
after
14
days.
The
degradates
D6,
D7
and
D8
were
detected
in
dark
samples
and
hence
were
true
photodegradates.

Analysis
of
the
simulated
sea
water
also
showed
a
similar
pattern.
At
the
15
minute
interval
after
the
commencement
of
the
experiment,
the
parent
compound
accounted
for
44.61%
of
the
total
radioactivity.
After
twenty
four
hours
into
the
study,
the
applied
radioactivity
attributable
to
the
parent
compound
declined
to
1.3%.
As
in
the
buffered
medium,
fourteen
transformation
products
were
identified
and
four
of
them
greater
than
ten
percent
of
the
applied
radioactivity,
seven
of
these
products
exceeded
5%
of
the
applied
radioactivity
and
the
remaining
(
three)
were
less
than
5%
of
the
applied
radioactivity.
As
in
the
sterile
water
system,
D6,
D7
and
D8
were
the
major
degradates
in
the
simulated
water
system.
D7
and
D8
degradates
reached
levels
of
13.6
%
and
45%
respectively
in
about
an
hour
after
the
study
commenced.
These
degradates
were
not
detected
in
the
dark
control
samples.

The
major
degradates
D6,
D7
and
D8
were:
pyridine
disulfide
(
PDS),
pyridine
sulfinic
acid
(
PSiA)
and
pyridine
sulfonic
acid
(
PsoA)
respectively.
Other
degradates
of
interest
were:
Pyrithione
disulfide
(
D3),
Pyrithione
sulfonic
acid
(
D10),
pyrithione
sulfinic
acid(
D9),
mixed
disulfide
(
D2)
and
2­
mercatopyridine
(
D5).
Page
6
of
15
The
aqueous
photolytic
half
life
in
buffered
medium
was
13
minutes
and
17
minutes
in
simulated
sea
water.

3.
Aerobic
Aquatic
Metabolism
(
Guideline
#:
162­
4,
MRID#:
440104­
01)

The
guideline
study
was
reviewed
by
the
Agency,
was
found
acceptable,
and
satisfies
the
aerobic
aquatic
metabolism
data
requirement
for
zinc
pyrithione.

The
study
was
conducted
on
the
radiolabelled
zinc
pyrithione
in
fresh
water/
sediment
and
sea
water/
sediment
samples.
The
samples
were
purged
in
air
and
kept
in
dark
at
25
±
1
o
C
for
incubation
for
0,
1,
3,
7,
14,
21
and
30
days.
The
extracted
samples
were
analyzed
using
Liquid
Scintillation
Counting
(
LSC)
,
high
performance
chromatography
(
HPLC)
and
thin
layer
chromatography
(
TLC).
Sediment
and
water
samples
were
separately
analyzed.
The
percent
recovery
was
between
90
to
112%
of
the
applied
radioactivity.
Unextractable
radioactivity
increased
from
about
9%
of
the
dose
at
time
zero
to
38%
at
day­
21
in
salt
water
samples.
It
increased
from
8%
at
time
zero
to
64%
at
day­
21
in
freshwater
samples.
Unextractable
radioactivity
declined
from
day
21
to
day
30
samples.
After
day
30
11.9%
of
the
radioactivity
was
due
to
the
evolution
of
carbon
dioxide
in
fresh
water
and
0.1%
in
saltwater.
Transformation
kinetics
(
degradation)
of
zinc
pyrithione
was
biphasic.
Almost
50%
of
the
applied
radioactivity
decreased
at
time
zero
after
which
there
was
a
slow
decline.
Half
life
in
the
first
phase
was
0.065
hour
in
saltwater
samples
and
1.3
hours
in
the
freshwater
samples.
In
the
second
phase
the
half
life
was
365
hours
in
saltwater
and
298
hours
in
the
freshwater.
Transformation
products
identified
were:
Pyrithione
disulfide,
pyrithione
sulfinic
acid,
pyrithione
sulfonic
acid,
and
mixed
sulfides
of
2­
mercaptopyridine
and
2­
mercaptopyridine
N­
oxide.
Pyrithione
disulfide
reached
a
level
of
16.9%
in
the
fresh
water
system
and
33.2%
in
the
salt
water
system.

The
fresh
water
and
sediments
were
obtained
from
the
shore
of
the
Connecticut
River
at
Portland
Boat
Works,
Portland,
CT
and
salt
water
and
sediments
were
procured
from
200
feet
off
shore
at
Little
Harbor,
Marble
Head,
Massachussets.
These
were
characterized
as
follows:

Fresh
(
water)
river
sediment
Salt(
sea)
water
sediment
%
sand
42
76
%
silt
54
14
%
clay
4
10
pH
6.8
7.7
Organic
matter
2.3%
1.6%
Cation
exchange
Cap.
4.3/
meq/
100g
23.5
meq/
100g
Bulk
Density
1.09
g/
cm3
1.42
g/
cm3
Classification
silt
loam
Sandy
loam
The
amounts
of
zinc
pyrithione
in
both
fresh
water
and
salt
water
declined
to
less
than
one
percent
after
30
days.
This
reduction
was
attributed
to
the
transchelation
of
zinc
pyrithione
to
copper
pyrithione
complex
which
is
said
to
be
a
more
stable
complex.
The
zinc
pyrithione
Page
7
of
15
amounts
in
the
salt
water
sediment
reduced
from
48.6%
on
day
1
to
36.8%
on
day
3
to
29%
on
day
7,
19%
on
day
14
and
20.4%
on
day
21
and
15.3%
on
day
30.
In
freshwater
sediment
the
zinc
pyrithione
amounts
reduced
from
33.2%
on
day
1
to
21.1%
on
day
3,
to
14.7%
on
day
7,
17.1%
on
day
14,
8.4%
on
day
21,
and
7.6%
on
day
30.
The
decline
of
zinc
pyrithione
was
more
pronounced
in
the
freshwater
sediment
than
in
the
sea
water
sediment.

The
amounts
of
extractable
residues
in
both
fresh
and
salt
water
sediments
declined
generally
from
day
one
to
day
30
samples.
The
extractable
residues
(
acetonitrile/
1%
HCL
system)
in
the
freshwater
system
declined
from
26.6%
on
day
1
to
16.3%
on
day
14
to
6.3%
on
day
30.
The
extractable
residues
in
the
freshwater
sediment
(
in
0.10M
KOH
medium)
declined
from
56.2%
on
day
1
to
36.4%
on
day
30.
The
extractable
residue
amounts
of
zinc
pyrithione
in
the
salt
water
sediments
(
acetonitrile/
0.10M
HCL
system)
declined
from
39.7%
on
day
1
to
29.0%
on
day
7,
18.9%
on
day
14
to
18.5
%
on
day
30.
In
0.10M
KOH
system,
the
salt
water
sediments
extractable
residues
declined
from
28.2%
on
day
1
to
25.5%
on
day
30.

The
amounts
of
unextractables
in
freshwater
sediments
increased
from
11.7%
on
day
1
to
34.3%
on
day
30.
The
amounts
of
unextractables
in
the
salt
water
sediment
increased
from
13.8
%
on
day
1
to
37.8%
on
day
21
to
26.5%
on
day
30.

3a.
Supplemental
Aerobic
Aquatic
Metabolism
(
162­
4,
MRID#:
448500­
04)

The
study
was
reviewed
by
the
Agency
and
was
found
acceptable
as
a
supplemental.
It
has
satisfied
the
aerobic
aquatic
metabolism
data
requirements
for
zinc
pyrithione.

This
study
was
conducted
on
a
saltwater
harbor
used
as
a
boat
maintenance
site.
Simultaneous
data
were
generated
for
copper
pyrithione
to
compare
the
degradation
patterns
between
the
tow
pyrithiones.

Each
sample
was
prepared
thus:
to
10
ml
water
5
grams
of
sediment
was
added
and
this
mixture
was
dosed
with
radiocarbon
(
C­
14)
labeled
52
ng/
g
(
ppb)
zinc
Pyrithione
and
incubated
under
aerobic
conditions
for
0,
3,
7,
and
30
days.
These
dosed
samples
were
extracted,
centrifuged
to
separate
the
water
from
the
sediments.
Each
water
and
sediment
fraction
was
analyzed
using
Liquid
Scintillation
Counting
(
LSC)
and
HPLC
Techniques.
Material
balance
for
individual
sample
ranged
between
93.5%
to
98.2%
of
the
applied
radioactivity.

Four
degrades
identified
represented
5%
of
the
dose
were:
pyrithione
sulfinic
acid,
pyrithione
sulfonic
acid,
2­
pyridine
sulfonic
acid,
and
pyrithione
thiosulfate
(
OTS).
However,
in
the
KOH
extract
of
the
sediment
only
degradate
identified
at
25.5%
was
pyrithione
thiosulfate(
OTS).
This
substance
may
have
present
in
the
sediment
of
may
have
been
produced
during
extraction
process
with
KOH
by
the
reaction
of
pyrithione
and
incipient
presence
of
sulfite
in
the
soil.

The
data
from
this
study
showed
that
both
pyrithiones
(
zinc
and
copper)
degraded
by
same
pathways
as
the
formation
and
decline
of
degradates
followed
the
same
pattern.
Kinetic
data
were
Page
8
of
15
collected
using
a
two­
compartment
model
(
water/
sediment)
and
rate
constants
and
half
lives
were
derived
for
both
water
and
sediment.
Water
extract,
with
no
OTS
present
yielded
a
degradation
of
zinc
pyrithione
half
life
=
0.60
hour.
Only
3%
of
pyrithione
remained
after
six
hours
and
after
three
days,
pyrithione
was
non­
detect.
Degradation
of
zinc
pyrithione
in
sediment
followed
a
nonlinear
kinetics
and
50%
of
it
degraded
after
0.89
dyas,
75%
after
5.1
days,
90%
after
34
days,
and
95%
after
134
days.
This
pattern
was
observed
in
the
presence
of
OTS.
In
the
absence
of
OTS
degradtion
time
declined
even
more:
50%
of
pyrithione
was
gone
in
0.03
day,
75%
in
0.19
day,
90%
in
1.3
day
and
95%
of
pyrithione
degraded
in
5.2
days.

The
sediment
was
characterized
with
the
following
properties:
%
sand
=
90
%
silt
=
4
%
Clay
=
6
pH
=
6
(
acidic)
Organic
Matter
=
0.7%
Cation
Exchange
Capacity
=
10.5
meq/
100
g
Bulk
Density
=
1.44
g/
cm3
Sediment
Type:
Sand
4.
Anaerobic
Aquatic
Metabolism
(
162­
3,
MRID#:
440104­
03)

The
study
was
reviewed
by
the
Agency,
was
found
acceptable,
and
satisfies
the
anaerobic
aquatic
metabolism
fate
data
requirement
for
zinc
pyrithione.

Radiolabelled
zinc­
pyrithione
at
a
treatment
level
of
3
and
6
ppm
was
investigated
for
anaerobic
aquatic
metabolism
at
25
±
1
o
C
with
samples
in
freshwater
and
saltwater
and
sediments.
Samples
were
collected
on
day
0,
0.25,
0.50,
0.75,
1,
2,
3,
7,
14,
30,
60
and
90
days.
The
extracted
samples
were
analyzed
by
Liquid
Scintillation
Counting
(
LSC),
high
performance
liquid
chromatography
(
HPLC)
and
thin
layer
chromatography(
TLC).
Percent
recoveries
ranged
from
93.9%
to
102.0%
for
the
fresh
water
samples
and
between
95.0%
to
101.6%
for
the
sea
water
samples.
The
average
over
all
recovery
of
the
applied
radioactivity
was
99.2%
for
entire
90
day
study
period.

The
fresh
water
and
salt
water
and
sediments
for
this
study
were
collected
from
the
same
locations
as
was
done
for
the
aerobic
aquatic
metabolism
study
(
i.
e.,
Connecticut
River).
The
water
/
sediment
samples
were
dosed
at
3
and
6
ppm.
Before
the
study
was
conducted
all
samples
were
purged
with
nitrogen,
stoppered
and
incubated
in
the
dark
at
25
C.
To
main
the
aerobic
atmosphere,
the
samples
were
purged
with
nitrogen
twice
a
month.

The
quantity
of
zinc
pyrithione
in
the
fresh
water
sample
declined
with
time.
It
was
at
14.8%
level
on
day
0,
5.5%
level
on
day
0.75,
5%
on
day
2,
3.1%
on
day
14
and
1.2%
on
day
30.
The
Page
9
of
15
average
amount
of
zinc
pyrithione
in
fresh
water
sediment
was
30%
on
day
0,
and
remaining
in
water
and
it
increased
in
the
sediment
to
50%
on
day
91.
The
extractable
residues
from
fresh
water
sediments
(
acetonitrile/
1%
HCL)
decreased
from
9.3%
on
day
0
to
9.4%
on
day
0.5
to
non­
detectable
level
on
day
0.75.
Similarly,
the
extractable
residues
in
1M
KOH
in
fresh
water
sediment
were
4.4%
on
day
0,
3.5%
on
day
0.50
,
5.5%
on
day
1
and
1.6%
on
day
2
to
nondetectable
thereafter.
The
freshwater
sediment
showed
undetectable
residues
of
17.2%
on
day
0,
18.1%
on
day
0.75,
21.1%
on
day
3
and
18.6%
on
day
91.

The
extractable
residues
in
the
sea
water(
salt
water),
was
72.5%
(
as
radioactivity)
for
day
0,
69%
for
day
0.25,
69.9%
for
day
1,
75.7%
for
day
14,
68%
for
day
60
and
73%
for
day
90.
The
extractable
residues
in
the
salt
water
sediment
(
acetonitrile/
1%
HCL)
increased
from
5.4%
on
day
0
to
8.8%
on
day
7
to
10.4%
on
day
14,
11.4%
on
day
60
to
10.9%
on
day
60.
The
extractable
residues
in
1M
KOH
from
the
salt
water
sediment
decreased
from
16.6%
on
day
0,
17.5%
on
day
0.25,
6%
on
day
14,
4.4%
on
day
60
and
8.2%
on
day
90.

The
quantity
of
zinc
pyrithione
in
fresh
and
salt
waters
was
less
than
one
percent
after
day
30.
Analysis
of
the
freshwater
samples
indicated
that
50.5%
of
the
applied
radioactivity
was
in
the
water
layer
of
the
samples.
At
day
90,
the
organosoluble
fraction
accounted
for
8.2%
of
the
total
applied
radioactivity.
NaOH
extracts
from
the
solids
accounted
for
15.9%
at
the
end
of
90­
day
study.

Sea
water
samples
analysis
showed
that
the
applied
radioactivity
in
the
water
layer
was
between
66.2%
to
76.1%.
The
organosolvent
layer
contained
about
10%
of
the
total
applied
radioactivity.
NaOH
extracts
from
solids
showed
that
by
day­
90,
only
3.6
%
of
the
applied
radioactivity
was
present
in
these
samples.
In
sea
water
carbon
dioxide
accounted
for
2.1%
of
the
applied
radioactivity.

Non­
extractables
from
both
freshwater
and
seawater
samples
showed
a
large
variation.
Freshwater
sediments
showed
the
presence
of
7.2%
fulvic
acids,
5.6%
humic
acid
and
5.9%
humins.
The
analysis
of
sea
water
showed
the
presence
of
3.0%
fulvic
acid,
1.3%
humic
acid
and
1.9%
humins.

The
half
life
of
zinc
pyrithione
in
fresh
and
sea
water,
under
anaerobic
conditions
was
estimated
to
be
less
than
2
hours
in
the
first
phase
and
in
the
second
phase
a
half
life
of
25.5
hours
and
13.1
hours
in
freshwater
and
seawater
sediments
respectively.

Some
of
the
major
transformation
products
identified
under
these
conditions
were:
Pyrithione
sulfinic
acid,
pyrithione
sulfonic
acid,
pyrithione
disulfide,
pyridine
sufinic
acid,
pyridine
sulfonic
acid,
2­
mercaptopyridine,
a
mixture
of
2­
mercaptopyridine
and
2­
mercaptopyridine
Noxide
and
pyridine
thiosulfonic
acid
and
pyridine
disulfide
.
In
addition,
five
minor
transformation
products
were
also
detected.

4a.
Supplemental
Anaerobic
Aquatic
Metabolism
of
Zinc
Pyrithione
in
Marine
Page
10
of
15
Water
and
Sediment
(
MRID#:
448500­
02)

The
study
was
reviewed
by
the
Agency
and
was
found
acceptable
as
a
supplemental
study
for
anaerobic
aquatic
metabolism
in
Marine
water
and
sediment
A
Companion
Study
on
anaerobic
aquatic
metabolism
of
zinc
pyrithione
was
conducted
along
side
with
copper
pyrithione
for
comparative
purposes.
This
study
was
conducted
on
the
sediment/
water
samples
collected
from
Little
Harbor
(
a
salt
Marina),
Marblehead,
MA.
Mixtures
of
water
and
sediment
(
5
grams
sediment
in
10
ml
water)
were
dosed
with
50
ng/
g
of
zinc
pyrithione).
The
mixtures
were
incubated
in
the
dark
at
25
o
C
and
samples
analyzed
at
day
=
0,
1,
7
and
30.
Anaerobic
conditions
were
maintained
by
constantly
purging
samples
with
nitrogen.
Analyses
were
performed
using
the
Liquid
Scintillation
counting
(
LSC)
and
HPLC
techniques.
Both
zinc
and
copper
pyrithiones
degraded
by
the
same
metabolic
pathway.
Half
life
of
zinc
pyrithione
degradation
under
these
anaerobic
conditions
was
less
than
a
day
and
over
99%
of
zinc
pyrithione
was
degraded
within
seven
days.
Copper
pyrithione
followed
a
similar
half
life
pattern.

Two
compartment
model
was
used
to
calculate
the
half
lives
in
water
and
sediment
compartments.
Degradation
of
zinc
pyrithione
rate
constants
were
calculated
and
water
phase
rate
constant
=
31
days­
1,
which
gives
a
half
life
of
0.5
hours,
and
for
the
sediment
phase
the
rate
constant
is
0.88
days­
1
which
corresponds
to
a
half
life
of
18.9
hours.

The
sediment
of
the
Little
Harbor
Salt
Marina
(
Marblehead,
MA)
was
classified
as
loose
sand
(%
sand:
86,
%
silt:
6
and
%
clay:
8,
and
the
sediment
was
basic).
PH
of
the
sediment
=
7.9,
%
organic
matter
=
2.3.

5.
Adsorption/
Desorption
in
soils/
sediments
(
Guideline
#:
163­
1,
MRID#:
440104­
02)

The
study
was
reviewed
by
the
Agency,
was
found
acceptable,
and
it
satisfies
the
adsorption/
desorption
data
requirement
for
zinc
pyrithione.

The
binding
constants
or
binding
potentials
or
partition
coefficients
of
zinc
pyrithione
were
determined
by
a
batch
equilibrium
method
on
two
terrestrial
soils
and
two
sediments
from
fresh
and
salt
water
sources
(
Marblehead
salt
soil,
Portland
fresh
soil,
Marblehead
salt
sediment
and
Portland
fresh
sediment).
The
nominal
concentrations
of
the
pesticide
in
the
samples
were:
0.50,
1,
2,
and
4
ppm.

For
two
soils
,
soil­
to­
solution
ratio
was
1:
5;
for
the
salt
sediment
it
was
1:
100
and
was
1:
50
for
the
fresh
sediment.
Optimum
equilibration
time
was
4
hours
for
the
salt
soils
and
2
hours
for
the
fresh
soil
and
72
hours
for
the
two
sediments(
for
both
adsorption
and
desorption
processes).
The
HPLC
analyses
showed:
Page
11
of
15
Zinc
pyrithione:
43.4%
in
the
Marblehead
salt
sediment
Unknown
product:
30.7%,
Marblehead
salt
soil
Pyrithione
disulfide:
39.6%,
Portland
fresh
soil
Pyrithione
sulfinic
acid:
22.2%,
Portland
fresh
sediment
14.85%
of
2,2'­
dithiopyridine
was
also
identified
in
Portland
salt
sediment
and
3.91%
of
mixed
disulfide
in
Marblehead
salt
sediment
was
also
present.

Soil/
sediment
K
ads
K
des
Marblehead
salt
soil
50
71
Portland
fresh
soil
11
13
Marblehead
salt
sediment
99
202
Portland
fresh
sediment
48
87
Soil/
sediment
K
OC
Marblehead
salt
soil
2,347
Marblehead
salt
sediment
10,633
Portland
fresh
soil
784
Portland
fresh
sediment
3,597
The
classification
of
the
Marblehead
and
Portland
soils
and
sediments
were:

Marblehead
salt
soil:
Sandy
Loam
Marblehead
Sediment:
Sandy
Loam
Portland
Fresh
Soil:
Loam
Portland
Sediment:
Silt
Loam
The
Agency
further
noted
that
zinc
pyrithione,
when
it
dissociates
by
the
photolytic
pathway,
forms
many
transformation
products.
Major/
key
products
that
have
been
identified
are:

1.
Pyrithione
disulfide
2.
Pyrithione
sulfonic
acid
3.
Pyrithione
sulfinic
acid
4.
Pyridine
disulfide
5.
Pyridine
sulfonic
acid
6.
Pyridine
sulfinic
acid
7.
Mixed
disulfide
8.
2­
Mercaptopyridine
Page
12
of
15
6.
Soil
Column
Leaching
(
Guideline
#:
163­
1
,
MRID#
455652­
01)

The
Agency
reviewed
the
study
and
found
acceptable.
This
study
fulfils
the
Agency's
fate
requirement
guideline
study
163­
1.

A
soil
column
leaching
study
was
conducted
to
determine
mobility
of
zinc
pyrithione
in
various
soils.
Segmented
soil
columns
using
sand,
sandy
loam,
loam,
and
clay
were
made
to
determine
mobility.
Radiocarbon
(
C14)
labeled
zinc
pyrithione
(
3
µ
g
per
sample
were
added
to
each
soil
column
and
flushed
with
546
ml
of
calcium
chloride
(
0.01M),
which
amounts
to
20
inches
of
rain.
Similarly
aged
columns
were
made
with
sandy
loam
and
dosed
with
3
µ
g/
g
of
zinc
pyrithione
sample,
incubated
in
dark
at
25
o
C
for
25
hours.
11
grams
of
this
aged
soil
sample
was
put
on
the
top
of
a
column
in
a
layer
of
6
mm
height.
It
was
flushed
with
0.01
M
Calcium
chloride.
Metabolites
identified
in
both
aged
and
unaged
columns
were
same
and
had
similar
distribution
pattern
in
both
aged
and
unaged
soil
columns.
In
both
columns,
it
was
shown
that
zinc
pyrithione
was
immobile
and
did
not
move
down
beyond
the
first
(
top)
segment
of
a
column.
Table
A
lists
the
soil
types
(
and
their
characteristics)
used
for
this
study
(
reproduced
from
the
Study:
Zinc
Pyrithione
Soil
Column
Study
(
Lab.
ID#
72­
00B10ZPT,
submitted
by
Arch
Chemicals,
Inc.
and
the
performing
Lab.
Was:
Arch
Chemicals,
Inc.
Biocides
Technology,
350
Knotter
Drive,
Cheshire,
CT.;
Date
of
completion
of
study:
Dec.
17,
2001,
Table
1,
page
30)

Table
A
Soil
Characteristics
Used
for
This
Study
Classification/
Characteristic
Sand
Loam
Clay
Loam
Sandy
Loam
%
Sand
89
30
22
68
%
Silt
6
44
46
26
%
Clay
5
26
32
6
pH
7.5
6.9
6.3
6.6
%
Organic
Carbon
1.0
5.4
4.4
1.0
Cation
Exchange
Capacity
(
meq/
100g)
9.6
26.4
25.4
5.7
Bulk
Density
(
g/
cm3)
1.29
1.07
1.07
1.48
Field
Moisture
Capacity
(
1/
3
bar)
9.2%
35.7%
36.7%
13.3%

Notes:
1.
Leaching
time
for
sandy
loam
was
between
2
and
3
days
Page
13
of
15
2.
Leaching
time
for
sand
was
between
0.03
to
0.04
day
3.
Leaching
time
for
loam
was
between
0.19
to
0.14
day
(
one
value
was
estimated
to
be
around
1.51
day)
4.
Leaching
time
for
clay
loam
was
between
0.17
to
0.50
day
5.
Leaching
time
for
aged
sandy
loam
was
between
0.98
to
1.24
days.
6.
Metabolites
identified
from
this
study
are:
2­
pyridine
sulfinic
acid,,
N­
oxide;
2­
pyridine
sulfonic
acid,
N­
oxide;
2­
pyrdine
sulfinic
acid,
and
2­
pyridine
sulfonic
acid.

7.
Special
Leaching
Studies
for
Antifoulant
Use,
ASTM
Method
D
5108­
90,
MRID#
s:
448333­
10,
453472­
01,
453498­
01,
448771­
03,
448771­
04,
448771­
05,
448771­
06).

These
studies
were
reviewed
by
the
Agency
and
found
acceptable
for
leaching
of
zinc
pyrithione
when
used
as
an
antifoulant
on
small
boat
bottoms.
The
Agency
recognizes
the
ASTM
Method
5108­
90
as
a
standard
laboratory
method
for
leaching
of
antifoulants
from
ship/
boat
bottoms.

The
special
leaching
studies,
or
aqueous
availability
studies,
were
conducted
on
different
formulations
containing
zinc
pyrithione.
These
are
laboratory
studies
which
mimic
the
conditions
that
ships/
boats
encounter
when
they
are
docked
in
a
marina
or
a
harbor.
On
an
area
of
200
cm2
of
polycarbonate
cylinders,
antifoulants
are
applied
with
a
known
thickness.
These
cylinders
are
kept
in
holding
tanks
which
contain
synthetic
sea
water
(
prepared
by
ASTM
Method
D
1141­
90).
These
painted
cylinders
are
rotated
for
sixty
minutes
at
60
rate
per
minute
(
rpm)
which
resembles
the
boat
motion
in
the
sea.
Samples
of
zinc
pyrithione
are
collected
and
analyzed
by
HPLC.
The
pH
of
the
holding
tank
is
kept
between
7.9
and
8.1,
salinity
of
synthetic
sea
water
is
maintained
between
30
to
35
parts
per
thousand
(
ppt).
The
temperature
of
the
holding
tank
is
maintained
at
25
o
C
±
2
o
C.
Duration
of
the
entire
study
is
45
days.
Samples
are
collected
and
analyzed
on
days,
1,
7,
14,
21,
35,
and
45.
A
pseudo
steady
state
of
leach
rate
is
attained
around
day21/
22.
Average
leach
rate/
day
and
cumulative
leach
rates
are
calculated.
Table
B
summarizes
the
average
leach
rate/
day
(
for
days
between
21/
22
and
45)
along
with
the
percent
of
zinc
pyrithione
in
various
formulations.

Table
B
Average
Leach
Rate
Per
Day
of
Zinc
Pyrithione
in
Various
Formulations
Product
Name
Leach
Rate/
Day
(
µ
g/
cm2/
day)
%
ZnOM
MRID#

Ecoloflex
BEA
369
6.5
3.8
448771­
04
Page
14
of
15
Ecoloflex
BEA
468
5.4
3.8
448771­
05
Ecoloflex
BEA
469
4.3
3.8
448771­
06
Ecoloflex
BEA
368
7.2
3.8
448771­
03
EPaint
SN­
1
1.2
2
448333­
10
EPaint
2000
2.02
4.7
448333­
10
Micron
Optima
Red
8.4
3.7
453472­
01
Ecoloflex
BEA
363
7.3
3.2
453498­
01
Notes:
1.
Average
Leach
Rate
per
day
(
µ
g/
cm2/
day)
=
5.3
2.
Average
%
of
zinc
pyrithione
=
3.6
8.
Zinc
Pyrithione
Outdoor
Microcosm
Study
This
study
was
submitted
by
the
registrants
and
reviewed
by
the
Agency,
although
it
was
not
a
required
study.
The
study
report
states
that
it
was
conducted
using
OPPTS
Guideline
835.3180
as
guidance;
however,
the
study
does
not
fully
meet
the
guideline
requirements.
OPP
is
retaining
the
study
as
supplemental
information
on
the
degradation
of
zinc
pyrithione
under
simulated
natural
conditions.
The
results
of
the
study
do
indicate
that
pyrithione,
added
to
seawater
in
a
manner
to
simulate
leaching
from
treated
vessels,
degrades
rapidly
and
essentially
completely
within
twenty
four
hours,
regardless
of
the
time
of
the
day
or
night
that
leaching
occurs.
The
half­
life
of
zinc
pyrithione
in
the
light­
dosed
tank
was
36
minutes,
while
the
half­
life
in
the
dark­
dosed
tank
was
estimated
to
be
approximately
20
hours.
The
study
also
indicates
that
zinc
pyrithione
shows
little
tendency
to
accumulate
in
sediment,
particularly
if
light
is
present.
These
results
provide
additional
support
to
the
findings
of
laboratory
studies
conducted
to
evaluate
the
various
degradation
pathways
for
zinc
pyrithione.
The
results
of
those
studies
will
be
incorporated
into
the
revised
modeling
of
the
antifoulant
use
during
the
reassessment
of
the
conditional
registration
of
antifoulant
products.

BIBLIOGRAPHY
1.
EPA
Document:
MRID#
438646­
02
2.
EPA
Document:
MRID#
440115­
01
3.
EPA
Document:
MRID#
440104­
01
4.
EPA
Document:
MRID#
440104­
02
5.
EPA
Document:
MRID#
440104­
03
6.
EPA
Document:
MRID#:
448500­
02
7.
EPA
Document:
MRID#:
455652­
01
Page
15
of
15
8.
EPA
Document:
MRID#:
448333­
10
9.
EPA
Document:
MRID#:
453472­
01
10.
EPA
Document:
MRID#:
453498­
01
11.
EPA
Document:
MRID#:
448771­
03
12.
EPA
Document:
MRID#:
448771­
04
13.
EPA
Document:
MRID#:
448771­
05
14.
EPA
Document:
MRID#:
448771­
06
15.
EPA
Document:
MRID#:
448500­
04
16.
EPA
Document:
MRID#:
458765­
01
17.
Chris
Jiang,
DER:
Leach
Rate
Data
of
Zinc
Pyrithione
from
Ecoloflex,
BEA
368/
G584,
Nov.,
1999
18
Chris
Jiang,
DER:
Leach
Rate
Data
of
Zinc
Omadien
from
Ecoloflex
BEA
369/
G044,
Nov.,
1999
19.
Chris
Jiang,
DER
Leach
Rate
Data
of
Zinc
Pyrithione
from
Ecoloflex
BEA
468/
G580,
Nov,
1999
20.
Chris
Jiang,
DER:
Leach
Rate
Data
of
Zinc
Pyrithione
from
Ecoloflex
BEA
469/
G043,
Nov,
1999
21.
A.
Najm
Shamim
DER:
Leach
Rate
Data
of
Zinc
Pyrithione
from
E
Paint:
SN­
1
22.
A.
Najm
Shamim
DER:
Leach
Rate
Data
of
Zinc
Pyrithione
from
E
Paint:
EP2000,
1998
23.
A.
Najm
Shamim
DER:
Leach
Rate
Data
of
Zinc
Pyrithione
from
Micron
Optima
RED,
1998
24.
A.
Najm
Shamim
DER:
Leach
Rate
Data
of
Zinc
Pyrithione
from
Intersmooth
Ecoloflex
BEA
363
25.
Srinivas
Gowda
DER:
Soil
Column
Leaching
Data
for
Zinc
Pyrithione,
May
2002.
26.
Srinivas
Gowda,
DER:
Supplemental
Anaerobic
Aquatic
Metabolism
of
Zinc
Pyrithione
in
Marine
Water
and
Sediment,
July,
2002
27.
Akiva
Abramovitch,
Science
Chapter
on
Zinc
Pyrithione
Environmental
Fate
Science
Review,
July,
1999,
and
references
therein.
28.
Sodium
Pyrithione
RED,
1996:
EPA
Document
#:
738­
R­
95­
031
