Dihalodialkylhydantoins:
Environmental
Hazard
and
Risk
Assessment
Page
2
of
18
1TGAI
=
technical
grade
active
ingredient
2TEP
=
typical
end­
use
product
Introduction
Dihalodialkylhydantoin
is
an
antimicrobial
used
to
control
algae
and
prevent
slime
formation
in
water
systems.
Registered
uses
include
cooling
water
systems
(
once­
through
and
recirculating),
paper
and
paperboard
process
water,
wastewater
treatment,
in­
tank
toilet
bowl
sanitizer,
greenhouse
irrigation,
and
swimming
pools.
The
toxicity
of
various
dihalodialkylhydantoin
compounds
varies,
depending
on
the
specific
halogen
group
added
to
the
5,5­
dimethylhydantoin
(
DMH)
core.
The
Office
of
Pesticide
Programs
has
previously
determined
that
the
moieties
of
toxicological
concern
are
5,5­
dimethylhydantoin
(
DMH)
and
5
ethyl­
5
methyl
hydantoin
(
EMH),
and
recognized
that
it
is
most
appropriate
to
test
these
organic
moieties
as
representative
of
the
toxicity
of
the
dihalodialkylhydantoins.
Therefore,
the
environmental
risk
assessment
will
be
conducted
using
DMH
endpoints.
However,
ecological
hazard
data
for
other
Halohydantoin
compounds,
as
well
as
DMH,
are
summarized
in
the
ecological
hazard
section
of
this
document,
below.

Several
data
requirements,
necessary
to
support
the
once­
through
cooling
tower
use
of
Halohydantoins,
are
not
fulfilled:
72­
4b/
850.1400
Invertebrate
life­
cycle
testing
­
freshwater
TGAI1
123­
1/
850.4225
Seedling
emergence
dose­
response
in
rice
TEP2
123­
1/
850.4250
Vegetative
vigor
dose­
response
in
rice
TEP
123­
2/
850.4400
Aquatic
vascular
plant
dose­
response
toxicity­
Lemna
sp.
TGAI
or
TEP
123­
2/
850.5400
Acute
algal
dose­
response
toxicity
­
4
species
TGAI
or
TEP
Ecological
Hazard
Assessment:

A.
Toxicity
to
Terrestrial
Animals
i.
Birds,
Acute
and
Subacute
An
acute
oral
toxicity
study
using
the
technical
grade
of
the
active
ingredient
(
TGAI)
is
required
to
establish
the
toxicity
of
Halohydantoins
to
birds.
The
preferred
test
species
is
either
mallard
duck
(
a
waterfowl)
or
bobwhite
quail
(
an
upland
game
bird).
The
results
of
one
toxicity
study
are
provided
in
the
following
table.
Page
3
of
18
Table
1.
Acute
Oral
Toxicity
of
Halohydantoins
to
Birds
Substance/%
Active
Ingredient
(
AI)
Organism
Endpoints/
Results
(
95%
conf.
interval)
mg/
kg
Reference
Study
classification
DMH/
97.2%
TGAI
Northern
bobwhite
(
Colinus
virginianus)
LD50
>
2150
NOEL
=
2150
Helsten,
1994
MRID
43289905
core
DMH/
96%
TGAI
Northern
bobwhite
(
Colinus
virginianus
LD50
=
1839
(
1350­
2250)
NOEL
=
1350
Grimes,
1986
MRID
#
147319
core
DMH/
99%
TGAI
Northern
bobwhite
(
Colinus
virginianus
LD50
=
1070
(
781
­
1542)
NOEL
=
250
Wildlife
International.,
1984
no
acc
or
MRID
#
core
DMH/
60/
27
formulated
product
Northern
bobwhite
(
Colinus
virginianus
LD50
>
2250
NOEL=
1780
1984
Acc
253966­
253972
core
DMH
97%
Northern
bobwhite
(
Colinus
virginianus)
LD50
=
1715
(
1252
­
2581)
NOEL
=
631
Fink,
1981
Acc
#
253071
and
253073
core
BCDMH
90%
Northern
bobwhite
(
Colinus
virginianus)
>
5620
Fink,
1981
Acc
#
252719
core
BCDMH
90%
Northern
bobwhite
(
Colinus
virginianus)
>
2510
Fink,
1981
Acc
#
252719
core
DBDMH
Northern
bobwhite
(
Colinus
virginianus)
>
2510
Acc
#
137088
supplemental
DCDMH
86%
Northern
bobwhite
(
Colinus
virginianus)
>
2510
NOEL
=
398
Acc#
137088
supplemental
These
results
indicate
that
Halohydantoins
are
slightly
toxic
to
practically
non­
toxic
to
birds
on
an
acute
oral
basis.
The
guideline
requirement
(
71­
1/
OPPTS
850.2100)
is
fulfilled.

Two
subacute
dietary
studies
using
the
technical
grade
of
the
active
ingredient
are
required
to
establish
the
toxicity
of
a
pesticide
to
birds.
The
preferred
test
species
are
mallard
duck
(
a
waterfowl)
and
Northern
bobwhite
quail
(
an
upland
gamebird).
Results
of
avian
subacute
dietary
Page
4
of
18
tests
are
tabulated
below.

Table
2.
Avian
Subacute
Dietary
Toxicity
of
Halohydantoins
Substance/%
AI
Species
LC50
(
ppm)
(
95
%
c.
i.)
NOAEC
(
ppm)
MRID
No.
Author/
Year
Study
Classification
DMH/
99.0%
Northern
bobwhite
(
Colinus
virginianus)
>
5620
1000
(
based
on
body
weight
gain)
Wildlife
International,
1984
No
acc
or
MRID
#
core
BCDMH
96.0%
Northern
bobwhite
(
Colinus
virginianus)
>
5620
3160
Grimes,
1986
acc
#
147321
core
DMH
97.2%
Northern
bobwhite
(
Colinus
virginianus)
>
5000
5000
Helsten,
1994
MRID
#
432899­
04
core
DMH
97%
Northern
bobwhite
(
Colinus
virginianus)
>
5620
N.
R.
Fink,
1981
Acc
#
253071
core
DMH
96%
Northern
bobwhite
(
Colinus
virginianus)
>
5620
N.
R.
Beavers,
1985
MRID
#
147321
core
DMH
97%
Mallard
(
Anas
platyrhynchos)
>
5620
N.
R.
Fink,
1981
Acc
#
253071
and
253073
core
BCDMH
96%
Mallard
(
Anas
platyrhynchos)
>
5620
3160
Grimes,
1986
acc
#
147321
core
DMH
97.2%
Mallard
(
Anas
platyrhynchos)
>
5000
5000
Helsten,
1994
MRID
432899­
03
core
DEMH
99.4%
Mallard
(
Anas
platyrhynchos)
>
5620
1780
Acc
#
253996­
72
core
These
results
indicate
that
Halohydantoins
are
practically
non­
toxic
to
birds
on
a
subacute
dietary
basis.
The
guideline
requirement
(
71­
2/
OPPTS
850.2200)
is
fulfilled.

ii.
Birds,
Chronic
Avian
reproduction
studies
using
the
technical
grade
of
the
active
ingredient
are
required
for
a
pesticide
when
any
of
the
following
conditions
are
met:
(
1)
birds
may
be
subject
to
repeated
or
continuous
exposure
to
the
pesticide,
especially
preceding
or
during
the
breeding
season,
(
2)
the
pesticide
is
stable
in
the
environment
to
the
extent
that
potentially
toxic
amounts
may
persist
in
animal
feed,
(
3)
the
pesticide
is
stored
or
accumulated
in
plant
or
animal
tissues,
and/
or,
(
4)
information
derived
from
mammalian
reproduction
studies
indicates
reproduction
in
terrestrial
vertebrates
may
be
adversely
affected
by
the
anticipated
use
of
the
product.
The
currently
Page
5
of
18
registered
uses
of
Halohydantoins
do
not
require
avian
reproduction
testing.
Page
6
of
18
iii.
Mammals
Wild
mammal
testing
was
not
required
for
Halohydantoins.
In
most
cases,
rodent
oral
toxicity
values
obtained
from
studies
conducted
to
support
data
requirements
for
human
health
risk
assessment
substitute
for
wild
mammal
testing.
This
information
is
discussed
in
the
Toxicology
chapter
of
this
RED
document,
from
which
the
following
is
excerpted:

The
acute
toxicity
of
dimethylhydantoin
is
low
by
the
oral
and
dermal
routes
of
exposure
(
Toxicity
categories
III
and
IV,
respectively).
Acute
lethality
by
the
inhalation
route
is
more
significant
(
Toxicity
category
II).
The
dimethylhydantoins
are
significant
eye
and
skin
irritants
(
Toxicity
category
I
and
II,
respectively).
Positive
dermal
sensitization
has
also
been
observed.

Non­
acute
toxicity
testing
of
dimethylhydantoins
(
including
subchronic,
developmental,
reproductive,
and
chronic
toxicity
testing)
all
show
the
presence
of
non­
specific
toxicity
only
at
relatively
high
doses
of
the
test
chemical.
Developmental
and
reproductive
toxicity
data
demonstrate
no
increase
in
susceptibility
to
the
toxic
effects
of
DMH
with
the
exception
of
one
study,
where
fetal
and
litter
effects
were
observed
at
a
lower
dose
level
than
that
which
resulted
in
maternal
toxicity.
However,
this
dose
level
(
500
mg/
kg)
was
considered
a
relatively
high
dose
for
an
effect
level.

B.
Toxicity
to
Freshwater
Aquatic
Animals
i.
Freshwater
Fish,
Acute
Two
fish
toxicity
studies
using
the
TGAI
are
required
to
establish
the
toxicity
of
a
pesticide
to
freshwater
fish.
The
preferred
test
species
are
rainbow
trout
(
a
coldwater
fish)
and
bluegill
sunfish
(
a
warmwater
fish).
The
results
of
studies
submitted
for
Halohydantoins
are
provided
in
the
following
table.

Table
3.
Acute
Toxicity
of
Halohydantoins
to
Freshwater
Fish
Substance/%
Active
Ingredient
(
AI)
Organism
Endpoints/
Results
(
mg
ai/
L)
Reference
Status
DMH/
97.1%
Bluegill
(
Lepomis
macrochirus)
LC50
>
1,017
NOEC
=
1,017
Murphy
and
Smith,
1992
MRID
­
423685­
01
core
BCDMH
90%
Bluegill
(
Lepomis
macrochirus)
LC50
=
1.17
(
1.05
­
1.30)
NOEC
=
0.75
Graney,
1981
Acc
#
252719
core
Page
7
of
18
DMH/
97.1%
Rainbow
trout
(
Oncorhynchus
mykiss)
LC50
>
972
NOEC
=
972
Murphy
and
Smith,
1992
MRID
­
423736­
01
core
BCDMH
97.1%
Fathead
minnow
(
Pimephales
promelas)
LC
50
>
1085
NOEC
=
1085
Murphy
and
Smith,
1992
MRID
#
423747­
02
core
BCDMH
99%
Bluegill
(
Lepomis
macrochirus)
LC50
=
0.36
(
0.18­
0.56)
NOEC
=
0.18
no
acc
or
MRID
core
DCDMH
97%
Bluegill
(
Lepomis
macrochirus)
LC50
=
2.35
(
1.87
­
2.96)
NOEC
=
0.87
Graney,
1981.
Acc
#
253071
core
DCEMH
99.4%
Bluegill
(
Lepomis
macrochirus)
LC50
=
2.1
(
0.87­
3.2)
NOEC
=
0.87
1984,
MRID
#
145356
core
Mixed
Halohydantoins:
60%
BCDMH,
27.4%
DDMH,
10.6%
DCEMH
Bluegill
(
Lepomis
macrochirus)
LC50
=
1.2
NOEC
=
0.9
Spare,
1982
Acc
#
253074
and
253072
core
Mixed
Halohydantoins:
60%
BCDMH,
27.4%
DDMH,
10.6%
DCEMH
Rainbow
trout
(
Oncorhynchus
mykiss)
LC50
=
0.5
(
0.3
­
0.9)
NOEC
=
0.3
Spare,
1982
Acc
#
253074
and
253072
core
Halobrom,
96%
Bluegill
(
Lepomis
macrochirus)
LC50
=
0.46
(
0.37­
0.59)
NOEC
0.18
McAllister
and
Cohle,
1984
MRID
#
147322
core
BCDMH,
99%
Rainbow
trout
(
Oncorhynchus
mykiss)
LC50
=
0.75
NOEC
=
0.56
1984,
no
ID#
core
Mixed
Halohydantoins
Rainbow
trout
(
Oncorhynchus
mykiss)
LC50
=
0.87
(
0.76­
0.91)
NOEC
=
0.3
Horne,
et
al.,
1980
MRID
#
46053
core
Mixed
Halohydantoins
Pimephales
promelas
LC50
=
2.25
(
2.05
­
2.48)
NOEC
=
1.7
Horne,
et
al.,
1980
MRID
#
46053
core
Halobrom,
96%
Rainbow
trout
(
Oncorhynchus
mykiss)
LC50
=
0.40
(
0.3­
0.56)
NOEC
=
0.18
McAllister
and
Cohle,
1984
MRID
#
147323
core
DMH,
97%
Rainbow
trout
(
Oncorhynchus
mykiss)
LC50
=
12700
(
11300­
14200)
NOEC
=
5000
Horne,
et
al.,
1980
MRID
#
46053
supplement
al
Page
8
of
18
DMH,
97%
Fathead
minnow
(
Pimephales
promelas)
LC50
=
14200
(
13386­
14990)
NOEC
=
10000
Horne,
et
al.,
1980
MRID
#
46053
supplement
al
DCDMH,
97%
Rainbow
trout
(
Oncorhynchus
mykiss)
LC50
=
0.91
(
0.82­
1.0)
NOEC
<
0.56
Graney,
1981
ACC
#
253071
core
DCEMH,
99.4%
Rainbow
trout
(
Oncorhynchus
mykiss)
LC50
=
1.17
(
0.97
­
1.3)
NOEC
=
0.56
1984,
MRID
#
145358
core
BCDMH,
96%
Rainbow
trout
(
Oncorhynchus
mykiss)
LC50
=
0.17
(
0.13
­
0.20)
NOEC
=
0.04
1986,
no
id
#
core
BCDMH,
90%
Rainbow
trout
(
Oncorhynchus
mykiss)
LC50
=
0.65
(
0.58
­
0.74)
NOEC
=
0.38
Graney,
1981
ACC
#
252719
core
Mix,
93.9%
total
Halohydantoins
Bluegill
(
Lepomis
macrochirus)
LC50
=
0.27
(
0.22
­
0.41)
NOEC
=
0.11
Sword,
et
al.,
1993.
MRID
#
431797­
06
core
Mix,
93.9%
total
Halohydantoins
Rainbow
trout
(
Oncorhynchus
mykiss)
LC50
=
0.16
(
0.14
­
0.24)
NOEC
=
0.076
Sword,
et
al.,
1993
MRID
#
431797­
05
core
These
results
indicate
that
Halohydantoins
range
from
highly
toxic
to
practically
non­
toxic
to
freshwater
fish
on
an
acute
basis.
DMH
is
practically
non­
toxic
to
freshwater
fish.
The
guideline
requirement
(
72­
1/
OPPTS
850.1075)
is
fulfilled.

ii.
Freshwater
Fish,
Chronic
A
freshwater
fish
early
life­
stage
test
using
the
technical
grade
of
the
active
ingredient
is
required
for
a
pesticide
when
it
may
be
applied
directly
to
water
or
if
the
end­
use
product
is
expected
to
be
transported
to
water
from
the
intended
use
site,
and
any
of
the
following
conditions
are
met:
(
1)
the
pesticide
is
intended
for
use
such
that
its
presence
in
water
is
likely
to
be
continuous
or
recurrent
regardless
of
toxicity,
(
2)
any
aquatic
acute
LC50
or
EC50
is
less
than
1
mg/
l,
(
3)
the
EEC
in
water
is
equal
to
or
greater
than
0.01
of
any
acute
LC50
or
EC50
value,
or,
(
4)
the
actual
or
estimated
environmental
concentration
in
water
resulting
from
use
is
less
than
0.01
of
any
acute
LC50
or
EC50
value
and
any
one
of
the
following
conditions
exist:
studies
of
other
organisms
indicate
the
reproductive
physiology
of
fish
may
be
affected,
physicochemical
properties
indicate
cumulative
effects,
or
the
pesticide
is
persistent
in
water
(
e.
g.,
half­
life
greater
than
4
days).
The
preferred
test
species
is
rainbow
trout,
but
other
species
may
be
used.
Freshwater
fish
early
life­
stage
testing
is
required
for
Halohydantoins
in
order
to
support
oncethrough
cooling
tower
uses.
The
results
of
one
study,
conducted
with
DMH,
are
summarized
in
the
table
below:
Page
9
of
18
Table
4.
Chronic
Toxicity
of
DMH
to
Freshwater
Fish
Substance/%
Active
Ingredient
(
AI)
Organism
Endpoints/
Results
(
mg/
L)
Comments
Reference
Status
DMH/
99.9%
Fathead
minnow
(
Pimephales
promelas)
NOEC
=
14
LOEC
=
29
­
dry
weight
was
the
most
sensitive
parameter
Holmes
and
Swigert,
1993
(
MRID
­
427217­
02)
core
The
guideline
requirement
(
72­
4/
OPPTS
850.1300)
is
fulfilled.

iii.
Freshwater
Invertebrates,
Acute
A
freshwater
aquatic
invertebrate
toxicity
test
using
the
TGAI
is
required
to
establish
the
toxicity
of
Halohydantoin
active
ingredients
to
freshwater
aquatic
invertebrates.
The
preferred
test
species
is
Daphnia
magna.
Results
of
this
test
are
tabulated
below.

Table
5.
Acute
Toxicity
of
Halohydantoins
to
Freshwater
Invertebrates
Substance/%
Active
Ingredient
(
AI)
Organism
Endpoints/
Results
(
mg/
L)
Reference
Status
DMH/
97.1%
Daphnia
magna
EC50
>
1070
NOEC
=
1070
Holmes
and
Smith,
1992
MRID
423736­
03
core
DMH,
97%
Daphnia
magna
LC50
=
6200
(
5300
­
6765)
NOEC
=
3000
Horne
et
al.,
1980
MRID
#
46053
supplemental
BCDMH
96%
Daphnia
magna
LC50
=
0.75
(
0.56
­
1.0)
NOEC
=
0.32
Forbis
et
al.,
1984
MRID
#
147324
core
DCDMH,
97%
Daphnia
magna
LC50
=
0.50
(
0.43
­
0.57
)
NOEC
=
0.10
Graney,
1981
ACC
#
253071
core
Mixed
Halohydantoins
Daphnia
magna
LC50
=
0.48
(
0.42
­
0.53)
NOEC
=
0.3
Horne,
et
al.,
1980
ACC
#
46053
core
BCDMH,
90%
Daphnia
magna
LC50
=
0.87
(
0.81
­
0.93)
NOEC
=
0.18
Graney,
1981
ACC
#
252719
core
Page
10
of
18
DCEMH,
99.4%
Daphnia
magna
LC50
=
0.95
(
0.75
­
1.2)
NOEC
=
0.75
1984
MRID
#
145357
core
BCDMH,
99%
Daphnia
magna
LC50
=
2.3
NOEC
=
1.0
1984,
no
id
#
core
BCDMH,
96%
Daphnia
magna
LC50
=
0.10
NOEC
=
0.022
Hoberg,
1986
no
id#
core
Mixed,
total
93.9%
Halohydantoins
Daphnia
magna
LC50
=
0.63
(
0.42
­
0.94)
NOEC
=
0.42
Sword
et
al.,
1993
MRID
#
431797­
07
core
Mixed
Halohydantoins:
60%
BCDMH,
27.4%
DCDMH,
10.6%
DCEMH
Daphnia
magna
LC50
=
0.4
(
0.3
­
0.5)
NOEC
=
0.3
Spare,
1982
ACC#
253074
and
253072
core
This
study
indicates
that
Halohydantoins
range
from
highly
toxic
to
practically
non­
toxic
to
aquatic
invertebrates
on
an
acute
basis.
DMH
is
practically
non­
toxic
to
freshwater
invertebrates.
The
guideline
requirement
(
72­
2/
OPPTS
850.1010)
is
fulfilled.

iv.
Freshwater
Invertebrates,
Chronic
A
freshwater
aquatic
invertebrate
life­
cycle
test
using
the
technical
grade
of
the
active
ingredient
is
required
for
a
pesticide
if
the
end­
use
product
may
be
applied
directly
to
water
or
expected
to
be
transported
to
water
from
the
intended
use
site,
and
any
of
the
following
conditions
are
met:
(
1)
the
pesticide
is
intended
for
use
such
that
its
presence
in
water
is
likely
to
be
continuous
or
recurrent
regardless
of
toxicity,
(
2)
any
aquatic
acute
LC50
or
EC50
is
less
than
1
mg/
l,
or,
(
3)
the
EEC
in
water
is
equal
to
or
greater
than
0.01
of
any
acute
EC50
or
LC50
value,
or,
(
4)
the
actual
or
estimated
environmental
concentration
in
water
resulting
from
use
is
less
than
0.01
of
any
aquatic
acute
EC50
or
LC50
value
and
any
of
the
following
conditions
exist:
studies
of
other
organisms
indicate
the
reproductive
physiology
of
invertebrates
may
be
affected,
physicochemical
properties
indicate
cumulative
effects,
or
the
pesticide
is
persistent
in
water
(
e.
g.,
half­
life
greater
than
4
days).
The
preferred
test
species
is
Daphnia
magna.
Freshwater
fish
early
life­
stage
testing
is
required
for
Halohydantoins
in
order
to
support
once­
through
cooling
tower
uses.
No
data
under
this
topic
have
been
submitted;
therefore
Guideline
72­
4b/
850.1400
is
not
fulfilled.

v.
Freshwater
Field
Studies
Freshwater
field
testing
is
required
for
pesticides
in
cases
where
there
are
risks
of
concern
from
labeled
use
patterns.
This
testing
was
not
required
for
Halohydantoins,
and
is
reserved
at
the
present
time.
Page
11
of
18
III.
Toxicity
to
Estuarine
and
Marine
Animals
A.
Estuarine
and
Marine
Fish,
Acute
Acute
toxicity
testing
with
estuarine/
marine
fish
using
the
technical
grade
of
the
active
ingredient
is
required
for
a
chemical
when
the
end­
use
product
is
intended
for
direct
application
to
the
marine/
estuarine
environment
or
the
active
ingredient
is
expected
to
reach
this
environment
because
of
its
use
in
coastal
counties.
The
preferred
test
species
is
sheepshead
minnow.

Table
5.
Acute
Toxicity
of
Halohydantoins
to
Estuarine/
Marine
Fish
Substance/
%
ai
Species
LC50
mg/
L
(
ppm)
NOAEC
mg/
L
(
ppm)
MRID
No.
Author/
Year
Status
BCDMH
90%
Sheepshead
minnow
(
Cyprinodon
variegatus)
1.5
0.32
Sousa,
1991
MRID
#
42076102
1991
and
43687301
1996
core
Dantobro
m
RW:
mixed
Halohydan
toins
Sheepshead
minnow
(
Cyprinodon
variegatus)
1.2
mg
Br2/
L
<
0.19
409931­
03
core
DMH,
97.1%
Sheepshead
minnow
(
Cyprinodon
variegatus)
>
1006
1006
Murphy
and
Smith,
1992
MRID
#
423747­
01
core
The
results
indicate
that
Halohydantoins
are
moderately
toxic
to
practically
non­
toxic
to
estuarine/
marine
fish
on
an
acute
basis.
The
guideline
requirement
(
72­
3a/
OPPTS
850.1025)
is
fulfilled.

B.
Estuarine
and
Marine
Fish,
Chronic
Estuarine/
marine
fish
early
life­
stage
testing
is
not
required
for
the
currently
registered
uses
of
Halohydantoins.
The
freshwater
fish
early
life­
stage
test,
which
is
required,
should
provide
an
adequate
endpoint
for
use
in
risk
assessments,
since
freshwater
fish
species
appear
to
be
more
sensitive
to
Halohydantoins
than
marine/
estuarine
species.

C.
Estuarine
and
Marine
Invertebrates,
Acute
Acute
toxicity
testing
with
estuarine/
marine
invertebrates
using
the
technical
grade
of
the
active
ingredient
is
required
for
a
pesticide
when
the
end­
use
product
is
intended
for
direct
application
to
the
marine/
estuarine
environment
or
the
active
ingredient
is
expected
to
reach
this
environment
because
of
its
use
in
coastal
counties.
The
preferred
test
species
are
mysid
shrimp
and
eastern
oyster.
Results
of
these
tests
are
tabulated
below.
Page
12
of
18
Table
6:
Acute
Toxicity
of
Halohydantoins
to
Estuarine/
Marine
Invertebrates
Substance/
%
ai.
Species
96­
hour
LC50/
EC50
mg/
L
(
ppm)
(
95%
c.
i.)
MRID
No.
Author/
Year
Status
BCDMH
90%
Eastern
oyster
(
Crassostrea
virginica)
shell
deposition
1.1
(
1.0
­
1.2)
NOEC
=
0.73
Sousa,
1991
42076101
1991
and
43687302
1996
core
DMH
90%
Mysid
(
Mysidopsis
bahia)
1.8
NOEC=
0.36
Sousa,
1991
42076103
1991
and
43687303
1996
core
Mixed
Halohydantoins:
60%
BCDMH,
10.6%
DEMH,
27.4%
DCDMH
Eastern
oyster
(
Crassostrea
virginica)
shell
deposition
EC50
=
0.86
mg
Br2/
L
NOEC
=
0.37
mg
Br2/
L
Suprenant,
1988
MRID
#
409931­
01
core
Mixed
Halohydantoins:
60%
BCDMH,
10.6%
DEMH,
27.4%
DCDMH
Mysid
(
Mysidopsis
bahia)
LC50
=
0.9
mg
Br2/
L
NOEC
=
0.10
mg
Br2/
L
Suprenant,
1988
MRID
#
409931­
01
core
DMH,
97.1%
Mysid
(
Mysidopsis
bahia)
LC50
>
921
(
limit
test)
Murphy
and
Smith,
1992
MRID
#
423736­
02
core
DMH,
97.2%
Eastern
oyster
(
Crassostrea
virginica)
shell
deposition
EC50
>
125
NOEC
=
125
McElwee,
1993
MRID
#
432899­
02
supplemental
The
results
indicate
that
Halohydantoins
are
highly
toxic
to
moderately
toxic
to
estuarine/
marine
invertebrates
on
an
acute
basis.
The
guideline
requirements
(
72­
3b
and
72­
3c/
OPPTS
850.1035
and
850.1045)
are
fulfilled.

D.
Estuarine
and
Marine
Invertebrate,
Chronic
An
estuarine/
marine
invertebrate
life­
cycle
toxicity
test
is
required
for
a
pesticide
if
the
end­
use
product
may
be
applied
directly
to
estuarine
or
marine
waters,
or
is
expected
to
be
transported
to
these
waters
from
the
intended
use
site,
and
any
of
the
following
conditions
are
met:
(
1)
the
pesticide
is
intended
for
use
such
that
its
presence
in
water
is
likely
to
be
continuous
or
recurrent
regardless
of
toxicity,
(
2)
any
aquatic
acute
LC50
or
EC50
is
less
than
1
mg/
l,
or,
(
3)
the
EEC
in
water
is
equal
to
or
greater
than
0.01
of
any
acute
EC50
or
LC50
value,
or,
(
4)
the
actual
or
estimated
environmental
concentration
in
water
resulting
from
use
is
less
than
0.01
of
any
aquatic
acute
EC50
or
LC50
value
and
any
of
the
following
conditions
exist:
studies
of
other
organisms
indicate
the
reproductive
physiology
of
invertebrates
may
be
affected,
physicochemical
properties
Page
13
of
18
indicate
cumulative
effects,
or
the
pesticide
is
persistent
in
water
(
e.
g.,
half­
life
greater
than
4
days).
Estuarine/
marine
invertebrate
life­
cycle
testing
is
not
required
for
Halohydantoins.
Lifecycle
testing
with
a
freshwater
invertebrate
is
required,
and,
since
freshwater
invertebrates
are
comparably
sensitive
to
Halohydantoins
on
an
acute
basis,
the
freshwater
life­
cycle
endpoints
will
suffice
for
assessing
risk
to
estuarine/
marine
invertebrate
species.

E.
Estuarine
and
Marine
Field
Studies
No
estuarine
or
marine
field
study
testing
is
currently
required
for
Halohydantoins.

IV.
Toxicity
to
Plants
A.
Terrestrial/
Semi­
aquatic
Currently,
terrestrial
plant
testing
is
not
required
for
pesticides
other
than
herbicides
except
on
a
case­
by­
case
basis
(
e.
g.,
labeling
bears
phytotoxicity
warnings,
incidents
of
plant
damage
have
been
reported,
or
literature
indicating
phytotoxicity
is
available).
The
once­
through
cooling
tower
use
of
Halohydantoins
requires
such
testing,
due
to
the
algaecidal
nature
of
the
chemical
and
the
likelihood
of
exposure
to
semi­
aquatic
plants
along
surface
waters
receiving
industrial
facility
outfall
from
the
cooling
system.
Guideline
123­
1/
850/
4225
and
850.4250,
Seedling
Emergence
and
Vegetative
Vigor
testing
with
Rice
(
Oryza
sativa)
is
not
fulfilled.
An
on­
line
search
of
the
ECOTOX
database
(
EPA,
2002)
did
not
provide
any
aquatic
plant
toxicity
data
for
Halohydantoins.

B.
Aquatic
Aquatic
plant
testing
was
previously
not
required
for
pesticides
other
than
herbicides
except
on
a
case­
by­
case
basis
(
e.
g.,
labeling
bears
phytotoxicity
warnings,
incidents
have
been
reported
involving
plants,
or
literature
is
available
that
indicates
phytotoxicity).
The
once­
through
cooling
tower
use
of
Halohydantoins
requires
such
testing,
due
to
the
algaecidal
nature
of
the
chemical
and
the
likelihood
of
exposure
to
aquatic
plants
in
surface
waters
receiving
industrial
facility
outfall
from
the
cooling
system.
Guideline
123­
2/
850/
4400
and
850.5400,
Vascular
Aquatic
Plant
and
Algal
dose­
response
toxicity
testing
(
5
species),
is
not
fulfilled.
An
on­
line
search
of
the
ECOTOX
database
(
EPA,
2002)
did
not
provide
any
aquatic
plant
toxicity
data
for
Halohydantoins.

B.
Risk
Assessment
and
Characterization
Risk
assessment
integrates
the
results
of
the
exposure
and
ecotoxicity
data
to
evaluate
the
likelihood
of
adverse
ecological
effects.
One
method
of
integrating
the
results
of
exposure
and
ecotoxicity
data
is
called
the
quotient
method.
For
this
method,
risk
quotients
(
RQs)
are
calculated
by
dividing
exposure
estimates
by
ecotoxicity
values,
both
acute
and
chronic:

RQ
=
EXPOSURE/
TOXICITY
RQs
are
then
compared
to
levels
of
concern
(
LOCs).
These
LOCs
are
criteria
used
by
OPP
to
Page
14
of
18
indicate
potential
risk
to
nontarget
organisms
and
the
need
to
consider
regulatory
action.
The
criteria
indicate
that
a
pesticide
used
as
directed
has
the
potential
to
cause
adverse
effects
on
nontarget
organisms.
LOCs
currently
address
the
following
risk
presumption
categories:
(
1)
acute
high
­
potential
for
acute
risk
is
high
regulatory
action
may
be
warranted
in
addition
to
restricted
use
classification;
(
2)
acute
restricted
use
­
the
potential
for
acute
risk
is
high,
but
this
may
be
mitigated
through
restricted
use
classification;
(
3)
acute
endangered
species
­
the
potential
for
acute
risk
to
endangered
species
is
high,
and
regulatory
action
may
be
warranted,
and
(
4)
chronic
risk
­
the
potential
for
chronic
risk
is
high,
and
regulatory
action
may
be
warranted.
Currently,
AD
does
not
perform
assessments
for
chronic
risk
to
plants,
acute
or
chronic
risks
to
nontarget
insects,
or
chronic
risk
from
granular/
bait
formulations
to
mammalian
or
avian
species.

The
ecotoxicity
test
values
(
i.
e.,
measurement
endpoints)
used
in
the
acute
and
chronic
risk
quotients
are
derived
from
the
results
of
required
studies.
Examples
of
ecotoxicity
values
derived
from
the
results
of
short­
term
laboratory
studies
that
assess
acute
effects
are:
(
1)
LC50
(
fish
and
birds)
(
2)
LD50
(
birds
and
mammals
(
3)
EC50
(
aquatic
plants
and
aquatic
invertebrates)
and
(
4)
EC25
(
terrestrial
plants).
The
NOEC
value
is
used
as
the
ecotoxicity
test
value
in
assessing
chronic
effects.

Risk
presumptions,
along
with
the
corresponding
RQs
and
LOCs
are
tabulated
below.

Risk
Presumptions
for
Terrestrial
Animals
Risk
Presumption
RQ
LOC
Birds
and
Wild
Mammals
Acute
High
Risk
EEC1/
LC50
or
LD50/
sqft2
or
LD50/
day3
0.5
Acute
Restricted
Use
EEC/
LC50
or
LD50/
sqft
or
LD50/
day
(
or
LD50
<
50
mg/
kg)
0.2
Acute
Endangered
Species
EEC/
LC50
or
LD50/
sqft
or
LD50/
day
0.1
Chronic
Risk
EEC/
NOEC
1
1
abbreviation
for
Estimated
Environmental
Concentration
(
ppm)
on
avian/
mammalian
food
items
2
mg/
ft2
3
mg
of
toxicant
consumed/
day
LD50
*
wt.
of
bird
LD50
*
wt.
of
bird
Risk
Presumptions
for
Aquatic
Animals
Risk
Presumption
RQ
LOC
Acute
High
Risk
EEC1/
LC50
or
EC50
0.5
Acute
Restricted
Use
EEC/
LC50
or
EC50
0.1
Acute
Endangered
Species
EEC/
LC50
or
EC50
0.05
Chronic
Risk
EEC/
MATC
or
NOEC
1
Page
15
of
18
1
EEC
=
(
ppm
or
ppb)
in
water
Risk
Presumptions
for
Plants
Risk
Presumption
RQ
LOC
Terrestrial
and
Semi­
Aquatic
Plants
Acute
High
Risk
EEC1/
EC25
1
Acute
Endangered
Species
EEC/
EC05
or
NOEC
1
Aquatic
Plants
Acute
High
Risk
EEC2/
EC50
1
Acute
Endangered
Species
EEC/
EC05
or
NOEC
1
1
EEC
=
lbs
ai/
A
2
EEC
=
(
ppb/
ppm)
in
water
1.
Environmental
Fate
Assessment
Summary
(
excerpted
from
the
Environmental
Fate
Science
Chapter
of
this
RED
document):

Dihalodialkylhydantoin
degrades
relatively
rapidly
in
water
under
abiotic
conditions.
However,
there
is
environmental
concern
for
soil
or
surface
water
contamination
from
the
major
degradate
DMH,
as
DMH
is
hydrolytically
and
photolytically
stable.
No
additional
fate
data
on
dimethylhydantoins
are
available
to
further
assess
fate
of
this
chemical.

Since
the
halogen
(
bromine
or
chlorine)
is
released
from
the
Halohydantoin
ring,
leaving
the
hydrolytically
and
photolytically
stable
DMH,
the
moiety
of
concern
for
environmental
exposure
is
DMH.
Environmental
risks
from
bromine
and
chlorine
are
addressed
in
separate
Agency
assessments.
2.
Environmental
Exposure
Assessment
The
PDM4
Model
was
used
to
estimate
exposure
from
once­
through
cooling
tower
uses.
The
details
of
this
model
are
found
in
the
Environmental
Modeling
Chapter
of
this
document.
A
lowflow
power
plant
(
100
+
10
million
gallons
per
day)
was
used
as
the
scenario
providing
the
maximum
concentrations
of
DMH
in
the
receiving
water,
e.
g.,
the
"
worst
case"
scenario.
Actual
concentrations
in
receiving
waters
are
likely
lower,
and
will
likely
not
show
the
increasing
trend
indicated
in
Table
7,
due
to
higher
flow
rates
and
possible
degradation/
dissipation
of
DMH
by
mechanisms
other
than
hydrolysis.
A
summary
of
the
estimated
environmental
concentrations
(
EECs)
over
time
is
provided
below:
Page
16
of
18
Table
7:
Summary
of
Estimated
Environmental
Concentrations
of
DMH
in
Rivers
Receiving
Outfall
from
Low­
Flow
Power
Plants
Using
Once­
Through
Cooling
Systems
Time
Period
Modeled
Peak
Concentration
of
DMH
Duration
of
Peak
Concentration
4
days
36.0
ppb
24
hours
30
days
210
ppb
24
hours
60
days
313
ppb
24
hours
The
model
was
also
used
to
determine
the
percent
of
days
per
year
various
"
concentrations
of
concern"
were
exceeded
for
several
power
plant
scenarios.
Details
of
these
results
are
provided
in
the
Environmental
Modeling
Chapter.

3.
Environmental
Risk
Assessment
a.
Terrestrial
Organisms:

No
model
is
available
to
estimate
exposure
and
risk
to
birds
and
mammals
from
discharge
of
once­
through
cooling
system
effluents
into
surface
waters.
The
low
EECs,
coupled
with
the
generally
low
toxicity
of
DMH
to
birds
and
mammals,
make
risk
to
these
organisms
unlikely.
There
are
no
data
available
to
assess
the
phytotoxicity
of
DMH
at
this
time;
therefore,
the
risk
to
terrestrial/
semi­
aquatic
plants
cannot
currently
be
assessed.

b.
Aquatic
Organisms:

Using
the
worst­
case
scenario
of
a
low­
flow
power
plant
using
Halohydantoins
for
once­
through
cooling
system
treatment,
the
following
risk
quotients
(
RQ)
were
calculated
for
aquatic
organisms:

Table
8:
Aquatic
Organism
Risk
Quotients
for
DMH
Used
in
Once­
Through
Cooling
of
Low­
Flow
Power
Plants
Endpoint
Type
Species
Value
EEC
(
from
Table
7)
RQ
(
EEC/
LC50)

Freshwater
Fish
Acute
Rainbow
trout
(
Oncorhynchus
mykiss)
LC50
>
972
mg/
L
(
MRID
­
423736­
01)
36.0
ppb
(
0.036
mg/
L)
0.000037
Freshwater
Invertebrate
Acute
Daphnia
magna
EC50
>
1070
mg/
L
NOEC
=
1070
mg/
L
(
MRID
423736­
03)
36.0
ppb
(
0.036
mg/
L)
0.000034
Freshwater
Fish
Chronic
Fathead
minnow
(
Pimephales
promelas)
NOEC
=
14
mg/
L
LOEC
=
29
mg/
L
(
MRID
­
427217­
02)
313
ppb
(
0.313
mg/
L)
0.022
Page
17
of
18
Using
the
very
conservative
EECs
provided
by
modeling
the
low­
flow
power
plant,
no
LOCs
are
exceeded.
Expressed
as
number
of
days
exceedance,
using
the
most
sensitive
parameter
of
14.0
mg/
L
(
14000
ppb)
(
freshwater
fish
chronic
NOEC)
as
the
"
concentration
of
concern"
and
the
exceedance
curve
generated
in
the
Environmental
Modeling
chapter,
the
chance
of
this
concentration
being
exceeded
by
any
of
the
power
plant
scenarios
is
extremely
low,
less
than
once
every
two
years.
Other
uses
of
Halohydantoin
products
are
indoor
or
contained
(
e.
g.,
swimming
pool)
uses,
and
should
not
result
in
appreciable
environmental
exposure
when
products
are
used
as
labeled.
Risk
to
freshwater
fish
and
aquatic
invertebrates
is
not
anticipated
from
the
use
of
Halohydantoins
in
once­
through
cooling
systems.
Marine/
estuarine
fish
are
generally
less
sensitive
than
freshwater
fish
to
Halohydantoins,
and
marine/
estuarine
invertebrates
are
comparably
as
sensitive
to
DMH
as
freshwater
invertebrates,
so
the
freshwater
RQ
are
presumed
to
be
protective
of
marine/
estuarine
species.
Risk
to
aquatic
plants
cannot
be
assessed
due
to
the
lack
of
phytotoxicity
data.

4.
Endangered
Species
Considerations
The
Agency
has
developed
the
Endangered
Species
Protection
Program
to
identify
pesticides
whose
use
may
cause
adverse
impacts
on
endangered
and
threatened
species,
and
to
implement
mitigation
measures
that
address
these
impacts.
The
Endangered
Species
Act
requires
federal
agencies
to
ensure
that
their
actions
are
not
likely
to
jeopardize
listed
species
or
adversely
modify
designated
critical
habitat.
To
analyze
the
potential
of
registered
pesticide
uses
to
affect
any
particular
species,
EPA
puts
basic
toxicity
and
exposure
data
developed
for
risk
assessments
into
context
for
individual
listed
species
and
their
locations
by
evaluating
important
ecological
parameters,
pesticide
use
information,
the
geographic
relationship
between
specific
pesticide
uses
and
species
locations,
and
biological
requirements
and
behavioral
aspects
of
the
particular
species.
A
determination
that
there
is
a
likelihood
of
potential
impact
to
a
listed
species
may
result
in
limitations
on
use
of
the
pesticide,
other
measures
to
mitigate
any
potential
impact,
or
consultations
with
the
Fish
and
Wildlife
Service
and/
or
the
National
Marine
Fisheries
Service
as
necessary.

Risk
to
Endangered
birds
and
mammals
is
not
anticipated
from
the
use
of
Halohydantoin
products
due
to
low
exposure
and
low
toxicity.
Calculated
RQs
for
fish
and
aquatic
invertebrates
from
the
once­
through
cooling
use
are
well
below
LOCs
for
Endangered
species;
other
uses
of
Halohydantoin
products
are
indoor
or
contained
(
e.
g.,
swimming
pool)
uses,
and
should
not
result
in
appreciable
environmental
exposure
when
products
are
used
as
labeled.
Therefore,
risk
to
Endangered
fish
and
aquatic
invertebrate
species
is
not
anticipated
from
the
use
of
Halohydantoin
products.
Risk
to
Endangered
plants
cannot
be
addressed
due
to
the
lack
of
phytotoxicity
data.
Page
18
of
18
REFERENCES
B.
R.
Helsten
(
1994).
14­
Day
Acute
Oral
LD
50
Study
with
DMH
in
Bobwhite
Quail.
Bio­
Life
Associates,
Ltd.
(
Neillsville,
WI).
Laboratory
Study
No.
126­
004­
03,
June
17,
1994.
MRID#
432899­
05.

Holmes,
C.
and
G.
Smith.
1992.
DMH:
A
48­
Hour
Static
Acute
Toxicity
Test
with
the
Cladoceran
(
Daphnia
magna)
­
Final
Report.
Wildlife
International
Ltd.
(
Easton,
MD).
Project
No.
298A­
101,
March
24,
1992.
MRID
No.
423736­
03.

Murphy,
D.
and
G.
Smith.
1992.
DMH:
A
96­
Hour
Static
Acute
Toxicity
Test
with
the
Bluegill
(
Lepomis
macrochirus)
­
Final
Report.
Wildlife
International
Ltd.
(
Easton,
MD).
Project
No.
298A­
105,
June
17,
1992.
MRID
No.
423685­
01.

U.
S.
Environmental
Protection
Agency
(
EPA).
2002.
ECOTOX
User
Guide:
ECOTOXicology
Database
System.
Version
3.0.
Available:
http://
www.
epa.
gov/
ecotox/
