1
UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
CERTIFIED
MAIL
Dear
Registrants:

This
is
to
inform
you
that
the
Environmental
Protection
Agency
(
hereafter
referred
to
as
EPA
or
the
Agency)
has
completed
its
revised
Atrazine
Interim
Reregistration
Eligibility
Decision
(
IRED),
consistent
with
the
Consent
Decree,
as
amended,
entered
in
Natural
Resources
Defense
Council
v.
Whitman,
Case
Number
C
­
99­
3701
CAL,
N.
D.
California
(
2002)).
It
does
not
alter
the
conclusions
of
the
January
31,
2003
IRED
document
except
as
described
below.
There
will
be
a
90­
day
public
comment
period
for
this
document.
At
a
later
date,
the
Agency
will
publish
a
comprehensive
atrazine
IRED
incorporating
changes,
if
any,
resulting
from
public
comment
and
combining
the
January
and
October
documents
into
one
document.

In
August
2002,
the
court
supervising
the
implementation
of
the
Consent
Decree
granted
a
request
from
EPA
and
Natural
Resources
Defense
Council
(
NRDC)
that
the
Decree's
deadline
for
the
atrazine
IRED
be
extended.
The
new
schedule
included
the
completion
of
an
IRED
by
January
31,
2003,
and
a
revised
IRED
by
October
31,
2003.
The
amended
Consent
Decree
states
that
the
revised
Interim
RED
for
atrazine
must
address
the
following:
(
1)
data
received
by
EPA
prior
to
February
28,
2003,
relating
to
the
potential
effects
of
atrazine
on
amphibian
species;
and
(
2)
to
the
extent
not
addressed
in
the
January
31,
2003
Interim
RED,
data,
received
prior
to
February
28,
2003,
relating
to
the
association
between
atrazine
exposure
and
the
incidence
of
prostate
or
other
cancer
in
humans.
The
amended
Consent
Decree
also
specifies
that
EPA
is
to
hold
FIFRA
Science
Advisory
Panel
(
SAP)
meetings
on
these
two
issues.

Ecological
monitoring
of
watersheds
was
required
in
the
January
IRED
due
to
the
potential
for
community­
level
and
population­
level
risk
to
aquatic
ecosystems
from
atrazine.
The
January
IRED
states
that
to
mitigate
these
ecological
risks
to
aquatic
communities,
the
Agency
is
requiring
that
atrazine
registrants,
in
consultation
with
EPA,
develop
a
program
under
which
the
registrants
monitor
for
atrazine
concentrations
and
mitigate
environmental
exposures
if
EPA
determines
that
mitigation
is
necessary.
The
program
will
focus
on
watershed
impacts
of
atrazine
use.
2
This
revision
to
the
January
31,
2003
IRED
consists
of
three
sections:
1)
potential
association
between
atrazine
exposure
and
the
incidence
of
prostate
cancer
and
other
cancers
in
humans;
2)
potential
effects
of
atrazine
on
amphibian
endocrinology
and
development;
and
3)
ecological
monitoring
and
mitigation
of
atrazine
in
watersheds.
In
each
section,
this
document
summarizes
the
conclusions
in
the
January
IRED
pertaining
to
the
section,
developments
since
the
IRED,
and
next
steps,
as
appropriate.
The
technical
documents
supporting
these
revisions
are
listed
below
and
appended
to
this
IRED.

A.
Review
of
Atrazine
Cancer
Epidemiology,
B.
Potential
Effects
of
Atrazine
on
Amphibian
Gonadal
Development,
C.
Final
Reports
of
the
Atrazine
Ecological
and
Monitoring
Subgroups,
D.
Atrazine
Ecological
Subgroup
Final
Report:
Recommendations
for
aquatic
community
Level
of
Concern
(
LOC)
and
method
to
apply
LOC(
s)
to
monitoring
data,
E.
Microcosm
and
Mesocosm
Data,
F.
Atrazine
Toxicity
Data
for
CASM
Simulations,
G.
CASM
Results:
Steinhaus
Similarity
Toxicity
Scenario,
H.
Comparison
of
Annual
Average
CASM
Steinhaus
Similarity
for
a
Series
of
Chemographs
Calculated
with
the
Logistic
Regression
vs.
Actual
CASM
Simulations,
I.
Comparison
of
Simulated
Change
in
Annual
Production
for
Phytoplankton,
Periphyton,
Macrophytes,
Zooplankton,
Benthic
Invertebrates,
and
Fish
for
CASM
Parameterizations,
J.
Decrease
in
Annual
Total
Production,
K.
Atrazine
Ecological
Monitoring
Program
Subgroup:
Recommendations
for
Monitoring
Design,
and
L.
Assessment
of
Potential
Mitigation
Measures
for
Atrazine,
February
13,
2003.

Potential
Association
Between
Atrazine
Exposure
and
Prostate
Cancer
and
Other
Cancers
in
Humans
January
31,
2003
IRED
The
Agency's
human
health
risk
assessment
for
the
January
31,
2003,
IRED
did
not
include
a
quantitative
risk
assessment
for
cancer
due
to
a
determination
by
the
EPA,
consistent
with
conclusions
reached
by
the
SAP
(
June
2000),
that
it
is
unlikely
that
atrazine's
cancer
mode
of
action
in
the
Sprague­
Dawley
rat
is
operative
in
humans.
EPA's
Cancer
Assessment
Review
Committee
(
CARC),
in
accordance
with
the
1999
Draft
Guidelines
for
Carcinogen
Risk
Assessment,
classified
atrazine
as
"
not
likely
to
be
carcinogenic
to
humans."

The
review
of
the
cancer
epidemiology
study
for
the
January
31,
2003,
IRED
did,
however,
include
epidemiological
data
on
workers
at
the
Syngenta
St.
Gabriel
Louisiana
plant
where
atrazine
is
manufactured.
The
study
reported
a
statistically
significant
increase
in
the
3
incidence
of
prostate
cancer
among
plant
workers.
The
Agency,
upon
review
of
this
study,
requested
additional
information
on
the
exposure
profile
of
the
employees
diagnosed
with
prostate
cancer
and
this
information
was
provided
and
reviewed.
Based
on
this
review,
it
appeared
that
most
of
the
increase
in
prostate
cancer
incidence
at
the
St.
Gabriel
plant
was
likely
due
to
intensive
prostate
specific
antigen
(
PSA)
screening
of
employees.
The
study
was
insufficiently
large
and
had
limitations
that
prevent
ruling
out
atrazine
as
a
potential
contributor
to
the
increase
observed.
On
balance,
however,
a
role
for
atrazine
seemed
unlikely
because
prostate
cancer
was
found
primarily
in
current
employees
who
received
intensive
PSA
screening;
there
was
no
increase
in
advanced
tumors
or
mortality;
and
proximity
to
atrazine
manufacturing
did
not
appear
to
be
correlated
with
risk.

Other
cancers
besides
prostate
were
found
to
have
an
elevated,
though
not
statistically
significant,
increase
in
risk
at
the
St.
Gabriel
plant.
Other
studies
have
suggested
an
increased
risk
for
ovarian,
breast,
and
other
cancers,
including
non­
Hodgkin's
lymphoma
(
NHL).
However,
EPA
had
previously
concluded
that
these
studies
were
at
best
preliminary
and
should
not
serve
as
a
basis
for
implicating
atrazine
as
a
human
carcinogen
due
to
their
methodological
limitations.

July
17,
2003
SAP
To
further
analyze
the
question
of
exposure
to
atrazine
and
prostate
cancer,
an
SAP
meeting
was
held
on
July
17,
2003
(
http://
www.
epa.
gov/
scipoly/
sap/
index.
htm).
Given
the
limited
nature
of
the
new
cancer
data
that
stimulated
the
request
for
a
second
SAP
meeting,
EPA's
submission
to
the
SAP
focused
primarily
on
the
new
prostate
cancer
data
rather
than
the
epidemiological
data
that
the
SAP
in
2000
had
judged
inconclusive
or
later
studies
received
since
2000
that
EPA
found
to
be
inconclusive.
EPA
asked
the
Panel
to
comment
on
the
Agency's
conclusion
regarding
prostate
cancer
and
particularly
the
preliminary
results
from
a
nested
casecontrol
study
of
the
St.
Gabriel
manufacturing
plant
in
Louisiana.
In
addition
to
this
study,
the
SAP
was
provided
with
other
epidemiological
studies
on
atrazine
exposure
and
prostate
cancer,
a
review
by
the
Agency
discussing
the
St.
Gabriel
data
and
epidemiological
data
bearing
on
prostate
cancers,
comments
from
four
external
peer
reviewers,
a
Syngenta­
sponsored
expert
panel
review,
and
comments
by
the
Natural
Resources
Defense
Council.
As
stated
in
the
January
IRED,
EPA's
view
of
the
study
was
that
the
increase
in
PSA
screening
for
the
St.
Gabriel
workers
could
explain
the
increase
in
prostate
cancer
observed
in
these
workers
and
therefore
a
role
for
atrazine
seemed
unlikely.
EPA
acknowledged,
however,
that
due
to
limitations
in
the
St.
Gabriel
study,
atrazine
could
not
be
ruled
out
as
a
potential
causal
factor.

The
SAP's
analysis
of
the
St.
Gabriel
study
differed
to
a
degree
from
the
Agency's
conclusion.
The
SAP
did
conclude
that
"
the
increase
in
Prostate
Specific
Antigen
(
PSA)
screening
at
the
St.
Gabriel
plant
likely
led
to
an
increase
in
the
detection
of
cases
of
prostate
cancer."
Further,
the
Panel
noted
that
"[
s]
ubstantive
and
persuasive
arguments
have
been
made
to
support
the
EPA's
conclusion
that
PSA
screening
could
explain
the
observed
increase
in
prostate
cancer
incidence
in
the
workers."
Nonetheless,
the
Panel
did
not
believe
there
was
sufficient
evidence
to
conclude
that
it
was
"
unlikely"
that
atrazine
had
a
role
in
the
increased
prostate
cancer
cases
seen
4
in
the
St.
Gabriel
study
"
given
the
severe
limitations
of
the
St.
Gabriel
study,
particularly
those
pertaining
to
small
sample
size,
questionable
exposure
assessment
and
lack
of
an
appropriate
comparison
group."
According
to
the
SAP,
PSA
screening
may
be
only
a
"
partial
explanation"
for
the
increase
in
prostate
cancer
seen
in
the
St.
Gabriel
study
and
that
"
atrazine
cannot
be
ruled
out
as
a
potential
cause."

The
Agency
agrees
with
the
SAP's
analysis
and
has
rewritten
its
conclusion
as
follows:

The
increase
in
prostate
cancer
incidence
at
the
St.
Gabriel
plant
in
Louisiana
is
consistent
with
the
intensive
PSA
screening.
This
is
because
prostate
cancer
was
found
primarily
in
active
employees
who
received
intensive
PSA
screening,
there
was
no
increase
in
advanced
tumors
or
mortality,
and
proximity
to
atrazine
manufacturing
did
not
appear
to
be
correlated
with
risk.
No
evidence
was
identified,
such
as
dose­
response
evidence,
that
permit
a
determination
that
some
of
the
increase
was
likely
due
to
exposure
to
atrazine
although
atrazine
exposure
cannot
be
ruled
out
at
this
time
as
a
cause.
However,
the
study
was
insufficiently
large
and
suffered
from
other
limitations
that
prevent
a
determination
that
all
of
the
increase
in
prostate
cancer
was
probably
due
to
the
intensive
screening
program.
Therefore,
EPA
concludes
that
the
St.
Gabriel
study
does
not
contribute
any
evidence
supporting
atrazine
as
a
likely
human
carcinogen.
(
see
Appendix
A)

The
SAP
suggested
that
the
Agency
consider
additional
analysis
of
the
St.
Gabriel
cohort.
However,
the
resulting
sample
size
would
still
limit
the
opportunity
to
draw
further
conclusions.
The
Agency
questions
whether
additional
analysis
is
warranted
for
other
potential
risk
factors
(
such
as
smoking,
diet
and
previous
work
history,
and
non­
occupational
or
pre­
employment
exposure
to
triazine
herbicides).
Because
of
the
way
the
study
was
designed,
this
information
is
not
available
to
investigators
and
it
may
not
be
feasible
to
obtain
such
information
for
the
St.
Gabriel
workers.

The
other
epidemiologic
studies
investigating
the
relationship
between
atrazine
exposure
and
prostate
cancer
did
not
alter
the
Panel's
opinion
that
the
evidence
presented
is
inadequate
to
support
the
Agency's
conclusion
of
atrazine
as
an
"
unlikely"
cause
of
prostate
cancer
seen
in
the
St.
Gabriel
study.
One
study
by
Mills
(
1998)
found
a
borderline
statistically
significant
positive
association
between
atrazine
use
by
county
with
prostate
cancer
incidence
rates
in
African
American
males.
A
second
study
by
Alavanja
et
al.
(
2003)
showed
no
association
of
self­
reported
atrazine
exposure
with
prostate
cancer
in
cohort
analysis
of
pesticide
applicators.

Epidemiological
Data
on
Other
Cancers
EPA
has
re­
reviewed
the
epidemiological
data
regarding
atrazine
and
cancer
that
were
examined
for
the
SAP
meetings
on
atrazine
in
2000
and
2003.
EPA
has
also
reviewed
data
that
have
become
available
since
the
latest
meeting
of
the
SAP
in
2003.
The
results
of
those
reviews
are
also
summarized
in
Appendix
A
to
this
document.
In
brief,
the
Agency
does
not
find
any
5
results
among
the
available
studies
that
would
lead
us
to
conclude
that
a
potential
cancer
risk
is
likely
from
exposure
to
atrazine.

Even
though
the
epidemiological
evidence
and
animal
data,
when
viewed
separately,
do
not
support
a
positive
cancer
finding
for
atrazine,
EPA
examined
the
totality
of
animal
and
human
data
to
determine
if
that
approach
showed
that
atrazine
was
likely
to
cause
a
carcinogenic
response
in
humans.
Specifically,
EPA
reviewed
the
available
animal
data
to
determine
if
a
mechanism
could
be
identified
which
supports
the
biological
plausibility
of
atrazine
as
a
human
carcinogen
taking
into
account
the
tumors
that
were
identified
in
the
epidemiological
data.
This
review
showed
that
(
1)
lymphomas,
including
NHL,
were
generally
not
seen
in
atrazine
animal
bioassays;
(
2)
a
mechanistic
role
for
atrazine
contributing
to
NHL
has
not
been
identified
in
laboratory
studies;
(
3)
tumors
at
any
endocrine
site
other
than
mammary
gland
tumors
in
female
SD
rats
(
e.
g.,
prostate,
ovarian
tumors)
have
not
been
identified
in
atrazine
bioassays;
(
4)
the
SAP
concluded
in
2000
that
the
mammary
gland
tumors
in
rats
caused
by
atrazine
are
produced
via
a
mechanism
not
relevant
to
humans;
and
(
5)
the
endocrine
tumors
that
have
been
raised
in
epidemiological
studies
(
other
than
mammary
gland
tumors)
can
not
be
biologically
tied
to
atrazine's
mode
of
action
(
i.
e.,
decrease
prolactin,
decrease
luteinizing
hormone
(
LH)
and
suppression
of
ovulation).
Thus,
at
this
time,
joint
consideration
of
the
available
animal
cancer
and
mode
of
action
data
and
epidemiological
studies,
does
not
indicate
that
atrazine
is
likely
to
cause
cancer
in
humans.

Conclusion
In
the
January
31,
2003
IRED,
EPA
concluded
that,
considering
the
animal
data
and
the
human
epidemiological
data,
atrazine
is
"
not
likely
to
be
carcinogenic
in
humans".
That
conclusion
allowed
EPA
to
find
that
there
is
a
reasonable
certainty
of
no
harm
from
exposure
to
atrazine
so
far
as
cancer
risk
is
concerned.
Results
in
the
St.
Gabriel
study
and
other
recent
epidemiological
studies
regarding
atrazine's
potential
link
to
cancer
do
not
alter
that
conclusion.
Further,
any
weight
attributable
to
these
data
is
weakened
by
the
data
in
animals
that
fail
to
reveal
any
mechanism
of
action
for
atrazine
consistent
with
the
cancers
observed
in
the
studies.
Accordingly,
EPA
concludes
that
atrazine
is
not
likely
to
be
a
human
carcinogen."

Next
Steps
Since
the
July
2003
SAP
meeting,
EPA
has
received
two
new
pieces
of
information:
(
1)
a
report
from
the
National
Cancer
Institute
(
NCI)
re­
analyzing
previous
epidemiologic
studies
of
atrazine
and
non­
Hodgkin=
s
lymphoma
using
hierarchical
techniques
to
adjust
for
the
effects
of
multiple
exposures;
and
(
2)
a
nested
case­
control
study
conducted
for
Syngenta
of
workers
at
the
St.
Gabriel
plant
using
more
detailed
job
histories
to
evaluate
exposure
indices.
The
Agency
plans
to
conduct
a
comprehensive
review
of
both
studies.
EPA's
preliminary
view
of
these
studies
is
discussed
in
Appendix
A.
EPA
is
also
expecting
to
receive
additional
epidemiological
studies
and
analyses
concerning
atrazine
and
cancer
from
the
NCI's
Agricultural
Health
Study
in
the
next
one
to
two
years.
These
studies
and
analyses
include
the
following:
an
update
of
the
Agricultural
6
Health
Study
on
prostate
cancer
capturing
additional
prostate
cancer
cases;
an
analysis
of
all
the
non­
Hodgkin's
lymphoma
cases
reported
in
the
Agricultural
Health
Study;
and
a
special
analysis
of
all
cancers
related
to
atrazine
exposure
in
the
same
Agricultural
Health
Study
cohort.
The
latest
projection
is
that
the
NCI
will
complete
these
studies
and
analyses
in
mid­
2005.

After
all
of
the
information
has
been
submitted
and
reviewed,
the
Agency
plans
to
convene
another
SAP
meeting
concerning
atrazine
and
its
possible
association
with
carcinogenic
effects.
At
that
meeting,
EPA
intends
to
present
the
SAP
with
all
of
the
data
bearing
on
atrazine
and
cancer,
including
the
old
and
new
epidemiology
studies.
In
the
meantime,
EPA
will
continue
its
review
of
all
new
data
submissions.
If
at
any
time,
results
from
any
of
the
new
data
submissions
raise
significant
questions
that
would
benefit
substantially
from
SAP
review
prior
to
submission
of
all
of
the
data,
the
Agency
will
hold
a
SAP
meeting
before
all
aspects
of
the
Agricultural
Health
Study
are
completed.

EPA
intends
to
thoroughly
review
any
SAP
report
from
any
future
meeting,
once
issued,
and
to
revise
its
determinations
regarding
the
cancer
potential
of
atrazine,
as
necessary.
Any
revisions
will
be
included
in
either
a
revision
to
the
October
31,
2003
IRED
or
the
final
reregistration
decision
for
atrazine
depending
on
the
timing
of
the
future
SAP
meeting
relative
to
issuance
of
the
final
atrazine
reregistration
decision.

Potential
Effects
of
Atrazine
on
Amphibian
Endocrinology
and
Development
January
31,
2003
IRED
In
the
ecological
risk
assessment
for
the
January
31,
2003
IRED,
the
Agency
did
not
suggest
that
endocrine
disruption,
or
potential
effects
on
endocrine­
mediated
pathways,
was
regarded
as
a
regulatory
endpoint
for
ecological
effects.
Nor
did
the
Agency
have
reliable
evidence
at
that
time
to
state
that
atrazine
caused
endocrine
effects
in
the
environment.
The
IRED
stated
that
based
on
the
existing
uncertainties
in
the
available
database,
atrazine
should
be
subject
to
more
definitive
testing
once
the
appropriate
testing
protocols
have
been
established.
The
Agency
was
aware
that
several
pertinent
studies
were
being
performed
by
researchers
that
may
reduce
some
of
the
uncertainties
in
understanding
potential
atrazine
effects
on
amphibian
endocrinology
and
reproductive
and
developmental
responses.

June
17­
20,
2003
SAP
Since
the
January
IRED,
the
Agency
has
conducted
a
comprehensive
evaluation
of
the
available
data
regarding
the
potential
effects
of
atrazine
on
amphibian
gonadal
development
and
presented
its
assessment
for
external
peer
review
to
a
SAP
in
June
2003.
In
a
May
29,
2003
white
paper,
the
Agency
summarized
seventeen
studies
consisting
of
both
open
literature
and
registrant­
submitted
laboratory
and
field
studies
involving
both
native
and
non­
native
species
of
frogs
(
see
Appendix
B).
In
its
white
paper
the
Agency
concluded
that
none
of
the
studies
fully
accounted
for
environmental
and
animal
husbandry
factors
capable
of
influencing
endpoints
that
7
the
studies
were
attempting
to
measure.
The
Agency
also
concluded
that
the
current
lines­
ofevidence
did
not
show
that
atrazine
produced
consistent
effects
across
a
range
of
exposure
concentrations
and
amphibian
species
tested.

Based
upon
this
assessment,
the
Agency
concluded
and
the
SAP
agreed
that
there
is
sufficient
evidence
to
formulate
a
hypothesis
that
atrazine
exposure
may
impact
gonadal
development
in
amphibians,
but
there
are
currently
insufficient
data
to
confirm
or
refute
the
hypothesis
(
http://
www.
epa.
gov/
oscpmont/
sap/
2003/
June/
junemeetingreport.
pdf).
Because
of
the
inconsistency
and
lack
of
reproducibility
across
studies
and
an
absence
of
a
dose­
response
relationship
in
the
currently
available
data,
the
Agency
has
determined
that
it
does
not
change
the
conclusions
reached
in
the
January
31,
2003
IRED
regarding
atrazine's
effects
on
amphibians.

Next
Steps
Based
on
the
conclusions
from
the
Agency's
white
paper
and
recommendations
of
the
SAP,
the
Agency
will
seek
additional
data
to
reduce
uncertainty
regarding
the
potential
risk
to
amphibians
(
http://
www.
epa.
gov/
oscpmont/
sap/
2003/
june/
dataevaluationreports.
htm).
This
data
collection
will
follow
the
multi­
tiered
process
outlined
in
the
Agency's
white
paper.
This
approach
to
collecting
additional
information
through
further
studies,
which
was
endorsed
by
the
SAP,
can
be
used
to
address
uncertainties
associated
with
the
potential
causal
relationships
between
atrazine
exposure
and
gonadal
development
and
characterize
the
nature
of
any
concentration­
response
relationship.

Ecological
Monitoring
and
Mitigation
of
Atrazine
in
Watersheds
January
31,
2003
IRED
The
ecological
risk
assessment
for
the
January
IRED
stated
that
the
Agency
has
ecological
risk
concerns
from
the
use
of
atrazine
and
identified
the
potential
for
community­
level
and
population­
level
risk
to
aquatic
ecosystems
at
prolonged
concentrations
of
atrazine
from
10
to
20
ppb.
To
mitigate
these
ecological
risks
to
aquatic
communities
and
to
determine
that
atrazine
is
eligible
for
reregistration,
the
Agency
required
that
atrazine
registrants,
in
consultation
with
EPA,
develop
a
program
under
which
the
registrants
monitor
for
atrazine
concentrations
and
mitigate
environmental
exposures
if
EPA
determined
that
mitigation
is
necessary.
This
program
would
focus
on
watershed
impacts
of
atrazine
use.

The
January
IRED
further
stated
that
the
program
will
include
an
appropriate
ecological
level
of
concern
(
LOC),
identified
by
EPA;
development
of
a
protocol
for
a
monitoring
program
that
specifies
the
frequency,
location,
and
timing
of
sampling,
as
well
as
an
appropriate
coordination
with
Total
Maximum
Daily
Load
(
TMDL)
programs;
triggers
for
mitigation
measures;
and
description
of
mitigation
measures
that
will
be
taken
if
triggers
are
exceeded.
This
monitoring
and
mitigation
program
would
be
designed,
conducted
and
implemented
on
a
tiered
watershed
level
and
must
be
consistent
with
existing
state
and
federal
water
quality
programs.
8
Follow­
up
to
January
31,
2003
IRED
The
following
description
highlights
how
EPA
developed
the
specifics
of
the
ecological
monitoring
and
mitigation
program
consistent
with
the
January
2003
IRED.
The
Office
of
Pesticide
Programs,
the
Office
of
Research
and
Development,
and
the
Office
of
Water
collaborated
to
integrate
and
develop
this
program.

Level
of
Concern
(
LOC)

The
sensitive
endpoint
in
the
ecological
assessment
for
atrazine
is
a
change
in
the
structure
and
function
of
primary
producers
in
the
aquatic
community.
Concentrations
of
atrazine
that
affect
plant
productivity
and
community
structure
typically
occur
at
levels
lower
than
those
that
directly
intoxicate
fish
and
aquatic
invertebrates.
By
focusing
on
aquatic
plant
community
structural
changes,
the
most
sensitive
endpoint,
the
Agency
intends
to
protect
fish
and
invertebrates
from
the
direct
effects
of
atrazine
as
well
as
the
effects
that
atrazine
could
have
on
the
habitat
and
food
sources
of
aquatic
animals
(
see
Appendices
C­
K).

The
Level
of
Concern
(
LOC)
was
derived
to
ensure
that
the
atrazine
concentrations
in
watersheds
will
not
cause
significant
changes
in
aquatic
plant
community
structure.
The
LOC
is
based
on
an
analysis
of
25
microcosm
and
mesocosm
studies
cited
in
the
Final
Report
of
a
report
provided
in
Appendix
D.
To
establish
the
LOC,
it
was
necessary
to
quantify
the
results
of
the
mesocosm
and
microcosm
studies
by
rating
their
reported
results
based
on
the
significance
of
the
effects
on
aquatic
plant
productivity
and
community
structure.
Each
study
was
analyzed
to
establish
the
reported
effect(
s)
and
the
atrazine
exposure
profile,
which
reflects
the
magnitude,
frequency
and
duration
of
atrazine
concentrations
in
the
study.
This
analysis
revealed
a
wide
range
of
study
designs
and
quality
and
also
indicated
that
a
wide
range
of
atrazine
exposure
profiles
could
result
in
significant
change
in
aquatic
community
productivity
and
structure.
A
method
was
developed
to
separate
the
reported
results
on
plant
community
productivity
and
structure
observed
in
these
studies
into
those
that
were
significant
versus
those
with
slight
to
noeffects

Since
atrazine
exposure
profiles
in
natural
systems,
in
this
case
streams,
will
typically
be
complex,
it
was
necessary
to
develop
a
method
to
analyze
monitoring
data
to
determine
when
monitored
exposure
profiles
are
functionally­
equivalent
to
those
profiles
observed
in
mesocosm
and
microcosm
studies
showing
significant
changes
when
the
monitored
profiles
are
functionallyequivalent
to
those
studies
that
showed
no
significant
effects.

Using
a
range
of
atrazine
exposure
profiles
representative
of
those
that
caused
significant
effects
in
the
microcosm
and
mesocosm
studies,
as
well
as
those
that
did
not
result
in
significant
effects,
an
ecological
food
chain
model
that
predicts
changes
in
aquatic
communities
in
streams
(
in
this
case,
Comprehensive
Aquatic
Systems
Model,
CASM),
was
used
to
develop
the
means
of
interpreting
whether
or
not
any
atrazine
exposure
profile
observed
in
the
monitoring
study
would
likely
be
associated
with
a
significant
effect
on
aquatic
communities.
These
analyses
determined
9
that
a
community
similarity
index
(
CSI)
that
quantifies
the
average
changes
in
biomass
for
plant
species
of
the
modeled
aquatic
community,
is
the
most
useful
model
parameter
to
segregate
those
mesocosm
and
microcosm
studies
that
exhibited
significant
effects
from
those
that
did
not.
Conceptually,
this
index
is
consistent
with
the
observed
effects
of
atrazine
on
primary
producers
in
aquatic
ecosystems.
More
specifically,
through
this
analysis
it
was
determined
that
an
average
CSI
change
of
5%
or
greater
over
the
course
of
a
study
reasonably
discriminated
micro­
and
mesocosm
exposure
profiles
associated
with
significant
effects
(
i.
e.,
irreparable
changes
to
ecosystems)
from
those
that
did
not
show
significant
effects.

Consequently,
these
analyses
establish
the
LOC
as
any
measured
atrazine
exposure
profile
obtained
through
a
monitoring
study
that
would
result
in
a
predicted
5%
or
greater
average
change
in
the
CSI
through
the
use
of
CASM.
Additional
analyses
over
the
duration
of
the
three
year
monitoring
study
will
evaluate
the
use
of
additional
aquatic
community
models
(
e.
g.,
Aquatox),
and
comparable
modeled
indices,
to
provide
additional
model
options
for
States,
Tribes
or
other
parties
to
evaluate
data
that
may
be
collected
in
other
monitoring
programs.

Monitoring
Program
Protocol
The
monitoring
protocol
is
initially
focused
on
flowing
water
bodies
(
i.
e.,
streams)
associated
with
corn
and
sorghum
production
(
see
Appendix
K).
Future
efforts
(
see
below)
will
address
the
need
to
monitor
estuaries
and
water
bodies
associated
with
sugarcane
production.
In
addition,
results
of
raw
water
monitoring
from
the
on­
going
atrazine
monitoring
program
for
drinking
water,
as
described
in
the
January
31,
2003
IRED,
will
be
analyzed
to
determine
its
potential
utility
in
evaluating
potential
ecological
effects
in
static
water
bodies.

The
purpose
of
the
monitoring
program
in
flowing
waters
is
to
estimate
the
magnitude
and
extent
to
which
water
bodies
with
the
greatest
potential
vulnerability
to
atrazine
exposure
(
primarily
based
on
atrazine
use
and
runoff
potential)
are
exceeding
the
level
of
concern
consistent
with
the
atrazine
ecological
risk
assessment,
which
was
described
above.
The
initial
analyses
identified
three
tiers
of
watersheds
relevant
to
atrazine
use
in
corn
and
sorghum.
The
first
tier
of
approximately
10,000
watersheds
had
some
level
of
atrazine
use
on
corn
and
sorghum.
The
watersheds
identified
in
this
assessment
were
primarily
at
the
5th,
or
Hydrologic
Unit
Code
(
HUC)­
10/
11,
level
of
a
hierarchal
system
of
mapping
watersheds
established
by
the
United
States
Geological
Survey
(
USGS).
At
this
level,
watersheds
are
typically
40,000
to
250,000
acres
in
size.
From
this
first
tier,
a
second
tier
of
5,860
HUC­
10/
11
watersheds
was
identified
based
on
use
intensities
of
0.25
lb
active
ingredient
(
ai)/
county
acre
or
higher.
From
this
second
tier
of
watersheds,
a
third
tier
of
1,172
watersheds
was
identified
based
on
their
predicted
potential
to
be
among
the
most
vulnerable
to
atrazine
surface
water
loading
from
use
on
corn
and
sorghum.
Through
the
development
of
a
statistically­
based
survey
design,
EPA
then
selected
40
HUC­
10/
11
watersheds
which
will
give
a
statistical
representation
of
the
third
tier
of
1,172
such
watersheds
predicted
to
be
most
potentially
vulnerable.
These
40
monitored
watersheds
are
located
in
10
states:
Ohio,
Indiana,
Kentucky,
Illinois,
Iowa,
Missouri,
Nebraska,
Minnesota,
Tennessee,
and
Louisiana.
The
selected
watersheds
averaged
129
square
miles
in
size,
with
a
median
size
of
121
10
square
miles.
Monitoring
sites
(
index
sites)
will
be
located
in
flowing
water
bodies
within
the
40
watersheds.
Two
years
of
monitoring
results
from
these
sites
will
be
compared
to
the
LOC
values.
The
registrant
shall
collect
monitoring
samples
every
4
days
prior
to,
during,
and
following
the
growing
season.
In
addition,
the
registrant
is
required
to
monitor
10
watershed
sites
daily
following
flow
events
to
better
estimate
temporal
variability
for
the
data
collected
in
the
remaining
30
watersheds.
Based
on
the
results
from
the
two­
year
monitoring
study
in
each
watershed,
as
interpreted
by
the
LOC,
the
Agency
will
evaluate
the
need
for
more
monitoring
and/
or
mitigation
actions
in
the
40
HUC­
10/
11
watersheds
and
the
implications,
if
any,
for
the
larger
set
of
1,172
most
potentially
vulnerable
watersheds.

Future
Monitoring
Decisions
for
Other
Water
Bodies
Estuaries
will
not
be
monitored
in
2004.
Discussions
will
be
conducted
with
the
Oceans
and
Coastal
Protection
Division
in
the
Office
of
Wetlands,
Oceans,
and
Watersheds
(
OWOW)
to
review
all
relevant
data
to
determine
whether
and
to
what
extent
monitoring
for
levels
of
atrazine
should
be
undertaken
for
estuaries.
The
role
of
dilution
and
transport
in
estuaries
must
be
determined.
It
may
be
possible
to
gather
some
information
on
these
parameters
by
looking
at
nitrate
concentrations
or
other
chemical
as
a
marker
to
ascertain
how
to
approach
an
estuary
monitoring
program.
This
analysis
will
be
completed
by
March
2004.
If
it
is
determined
a
monitoring
study
is
required,
it
is
recognized
additional
efforts
will
be
necessary
to
develop
a
monitoring
program.

To
evaluate
the
potential
for
ecological
concerns
in
static
water
bodies
(
i.
e.,
lakes
and
reservoirs),
raw
water
data
on
atrazine
concentrations
collected
from
the
approximately
140
Community
Water
Systems
that
are
being
monitored
for
human
health
concerns
will
initially
be
used.
In
addition,
the
registrant
will
provide
historical
data
from
the
Voluntary
Monitoring
Program
(
VMP)
sites.
The
methods
used
to
determine
the
LOC
for
flowing
water
bodies
are
amenable
for
use
in
static
water
bodies.
The
EPA
must
determine
on
a
statistical
and
ecosystem
basis
to
what
extent
the
monitoring
data
from
the
drinking
water
monitoring
program
should
be
interpreted
for
a
given
water
body
and
how
statistical
inferences
from
the
results
of
this
set
of
static
water
bodies
can
be
made
to
a
larger
population
of
potentially
vulnerable
static
water
bodies.
This
information
will
provide
the
basis
for
developing
a
monitoring
strategy
for
static
water
bodies.

A
strategy
will
be
developed
to
select
the
most
appropriate
locations
and
number
of
sites
for
monitoring
atrazine
in
sugarcane
growing
areas.
The
sugarcane
use
area
is
a
unique
situation
which
has
clear
freshwater
and
estuarine
issues.
As
a
pilot,
the
registrant
has
offered
to
monitor
four
additional
sites
distributed
between
Louisiana
and
Florida
with
one
being
the
Iberville
Community
Water
System
already
designated
for
increased
monitoring
in
the
drinking
water
program.
The
selection
of
these
pilot
sites
for
evaluating
potential
ecological
effects
and
the
protocol
for
monitoring
will
be
completed
by
March
2004.

Triggers
for
Mitigation
Measures
in
Flowing
Water
Bodies
11
For
the
40
watersheds,
the
registrant
shall
monitor
an
index
site
within
the
watershed
for
two
years,
regardless
if
a
decision
to
initiate
remediation
occurs
in
the
first
year.
If
monitoring
within
a
watershed
indicates
exceedences
of
the
5%
average
CSI
threshold,
based
on
CASM
model
results,
in
each
of
the
two
years,
the
registrant
will
initiate
and
conduct
a
TMDL
or
comparable
watershed
management
program
within
the
particular
watershed
where
the
exceedence
occurred,
consistent
with
the
state's
ongoing
TMDL
or
watershed
program.
If
a
TMDL
or
comparable
watershed
management
program
is
already
in
place
by
USDA,
state,
or
other
entity
in
a
given
watershed,
the
registrant
will
then
work
with
these
existing
programs
to
address
the
atrazine
exceedence.
If
an
exceedence
occurred
in
the
first
year
of
sampling
within
a
watershed,
the
registrant
will,
at
a
minimum
initiate
stewardship
outreach,
preferably
through
an
existing
USDA
or
state­
sponsored
watershed
management
program
if
one
exists.

If
an
index
site
in
a
watershed
has
exceeded
the
similarity
threshold
over
a
two
year
period,
the
registrant
shall
initiate
and
conduct
a
TMDL
(
or
similar)
program
to
reduce
atrazine
concentrations
associated
with
the
stream
reach
at
the
index
site
by
additional
monitoring
and
managing
atrazine
uses
in
those
portions
of
the
watershed
that
feed
into
the
index
site
and
result
in
the
exceedences.
At
the
same
time,
the
registrant
shall
conduct
additional
monitoring
at
other
sites
in
the
watershed
suspected
to
be
similar
to
the
index
site
in
order
to
determine
if
other
water
bodies
in
the
watershed
also
exceed
the
5%
similarity
threshold.
If
these
areas
are
determined
to
exceed
the
similarity
threshold,
then
the
registrant
shall
initiate
and
conduct
TMDL
(
or
similar)
mitigation
in
those
areas.

The
registrant
must
also
initiate
and
conduct
remediation
immediately
in
any
watershed
which
shows
an
exceedence
of

15%
of
the
CSI
rather
than
wait
for
a
second
year
of
data.
However,
monitoring
will
still
continue
at
the
original
index
site
in
the
second
year.

If
monitoring
results
indicate
an
exceedence
in
one
of
the
two
years
for
a
given
index
site
within
a
watershed,
a
decision
regarding
additional
monitoring
or
other
watershed
management
activities
will
be
based
on
the
specific
data
for
the
location
and
the
results
of
the
overall
study.
The
data
derived
from
all
of
the
40
watersheds
will
provide
information
needed
to
better
quantify
and
interpret
sampling
variability
in
the
context
of
the
exceedence
threshold.
These
future
analyses
will
inform
decision
criteria
for
those
cases
where
variability
in
monitoring
data
overlaps
uncertainties
in
the
LOC
derivation.

For
an
index
site
within
a
watershed,
if
monitoring
results
indicate
no
exceedences
of
the
5%
average
similarity
threshold
index
based
on
CASM
model
results
in
each
of
the
two
years,
then
no
further
action
will
be
required
in
the
watershed.

For
all
of
the
data
collected
in
the
40
watersheds,
interpretation
of
monitoring
data
after
two
years
would
include
an
assessment
as
to
whether
or
not
unusual
meterological
conditions
(
e.
g.,
high
or
low
rainfall)
existed
during
the
monitoring
period.
This
could
require
a
third
year
of
sampling
to
make
an
informed
decision
on
a
watershed's
condition.
12
In
addition,
if
States
or
Tribes
use
the
same
or
comparable
LOC
and
monitoring
protocols
(
e.
g.,
comparable
sampling
frequencies
and
analytical
techniques)
at
a
selected
stream
reach
outside
of
the
40
watersheds,
as
described
in
the
ecological
and
atrazine
monitoring
subgroup
reports
(
Appendix
C­
J),
as
well
as,
employ
decision
criteria
comparable
to
those
described
above,
the
registrant
will
initiate
and
conduct
a
TMDL
or
comparable
watershed
management
program
within
that
watershed
if
the
State
or
Tribal
data
shows
an
exceedence
of
the
LOC
for
two
years,
consistent
with
the
state's
ongoing
TMDL
or
watershed
program.

After
the
Agency
receives
the
data
from
the
40
watersheds,
it
will
be
analyzed
to
interpret
the
status
of
the
1,172
Tier
2
watersheds.
Due
to
the
nature
of
this
monitoring
design
it
will
be
possible
to
make
statistical
inferences
with
the
data
collected
from
the
40
watersheds
as
to
the
magnitude
and
extent
to
which
LOC
exceedences
could
be
occurring
in
the
remaining
tier
of
1,172
watersheds
considered
to
be
the
most
potentially
vulnerable.
After
these
statistical
inferences
are
completed,
a
decision
about
monitoring
in
the
remaining
1,172
vulnerable
watersheds
will
be
made,
with
the
understanding
it
is
possible
that
further
monitoring
and/
or
mitigation
may
be
required
of
the
registrant
in
these
other
watersheds.

Description
of
Mitigation
Measures
The
specific
techniques
to
be
employed
by
the
registrant
to
reduce
atrazine
loads
in
a
watershed
that
has
atrazine
concentrations
that
exceed
the
LOC
will
be
watershed
specific
and
undertaken
in
partnership
with
any
existing
watershed
management
programs.
The
registrant
will
follow
steps
that
are
typically
employed
in
the
Clean
Water
Act
TMDL
program
or
similar
management
programs
as
follows:

1.
Problem
Identification
­
Identify
pollutant
causing
impairment
and
impaired
water
body
and
determine
the
pollutant
reductions
needed
to
achieve
water
quality
standards
(
note
that
in
this
specific
situation
exceedence
of
the
atrazine
LOC
will
have
already
established
an
impairment
and
a
cause,
with
the
understanding
that
for
a
given
water
body
additional
pollutants
could
also
be
contributing
to
biological
impairment).

2.
Current
Situation
and
Desired
Objective
­
Indicate
desired
outcome
of
TMDL
process.

3.
Source
Assessment
­
Identify
pollution
source
and
contribution
to
impairment.

4.
Allocation
of
loads
­
Allocate
the
pollutant
loadings
among
the
various
pollutant
sources.

5.
Implementation
­
Describe
actions
to
mitigate
the
sources
of
pollution
(
e.
g.,
best
management
13
practices).

6.
Follow­
up
Monitoring
­
Determine
effectiveness
of
implemented
mitigation
measures.

7.
Feedback
Mechanism
­
Review
of
mitigation
measures
during
implementation
period
to
determine
if
adjustments
are
needed.

The
Clean
Water
Act
requires
that
States
identify
waters
that
fail
to
attain
water
quality
standards
and
establish
TMDLs
at
levels
that
attain
or
maintain
their
water
quality
standards.
EPA
is
required
to
review
and
approve
or
disapprove
the
list
of
impaired
waters
and
TMDLs.
If
EPA
disapproves
the
State's
list
or
the
TMDL,
EPA
is
required
to
identify
the
impaired
waters
or
establish
TMDLs.
The
States
and
EPA
establish
TMDLs
in
a
particular
watershed
by
determining
pollutant
loads
that
will
allow
the
attainment
of
water
quality
standards,
analyzing
existing
pollutant
loads
and
sources,
and
specifying
the
pollutant
load
reductions
necessary
to
attain
water
quality
standards.
TMDLs
are
implemented
through
existing
Federal,
State
or
local
requirements
and
programs.
EPA
encourages
TMDLs
that
are
established
and
implemented
as
part
of
an
overall
watershed
strategy
for
improving
water
quality.

The
Agency
expects
that
the
TMDL
process
(
or
similar
watershed
management
program)
will
result
in
mitigation
measures
that,
when
implemented,
will
effectively
lower
the
level
of
atrazine
to
below
the
level
of
concern.
These
mitigation
measures
could
include:
buffer
zones,
different
application
or
incorporation
methods,
restrictions
on
the
timing
of
application
due
to
rain,
and
lower
application
rates.
Implementation
of
these
controls
also
will
include
confirmatory
follow
up
monitoring
to
insure
that
the
atrazine
levels
are
below
the
LOC.
Given
the
rapid
progress
the
States
have
made
by
incorporating
TMDL
approaches
in
watershed
management
programs,
EPA
is
confident
that
management
activities
undertaken
by
the
registrant
consistent
with
meeting
the
loading
reductions
identified
in
a
TMDL
are
expected
to
be
successful
in
reducing
loadings
of
atrazine.
Since
1996,
more
than
9000
TMDLs
have
been
established
and
approved,
leading
to
activities
that
have
improved
water
quality.
Pollutant
loadings
have
been
reduced
and
water
quality
improved
as
reported
by
the
Office
of
Water's
Office
of
Wetlands,
Oceans
and
Watersheds
(
see
http://
www.
epa.
gov/
owow/
tmdl/).
In
the
unlikely
event
that
implementation
of
loading
reductions
identified
in
TMDLs
is
not
effective,
the
Agency
reserves
the
right
to
take
further
action
under
FIFRA
to
mitigate
this
risk
from
atrazine
and
will
consider,
as
appropriate,
the
benefits
of
atrazine
use
in
the
particular
watershed.

Benefits
of
Atrazine
Use
The
total
or
national
economic
impact
resulting
from
the
loss
of
atrazine
to
control
grass
and
broadleafed
weeds
in
corn,
sorghum
and
sugarcane
would
be
in
excess
of
2.0
billion
dollars
per
year
if
atrazine
were
unavailable
to
growers
(
Appendix
L,
"
Assessment
of
Potential
Mitigation
Measures
for
Atrazine",
February
13,
2003).
14
A
watershed­
specific
analysis
has
not
been
factored
into
this
assessment
because
of
the
uncertainty
surrounding
potentially
impacted
watersheds
and
any
required
mitigation.
However,
economic
impacts
could
be
expected
to
parallel
those
for
drinking
water
as
described
below.

Specifically,
EPA
analyzed
what
would
be
the
impact
to
the
corn
industry
in
areas
in
watersheds
contributing
to
Community
Water
Systems
which
find
atrazine
concentrations
exceeding
the
Agency's
level
of
concern,
and
found
that
growers
would
incur
an
average
loss
of
9
bushels
per
acre
(
nationwide
corn
yield
averaged
138
bushels
per
acre
in
2001),
as
well
as
an
increased
cost
for
a
replacement
herbicide.
This
yield
loss
plus
increased
herbicide
cost
may
result
in
an
average
estimated
loss
of
$
28
per
acre.
This
translates
to
a
yearly
loss
of
1.6
billion
dollars
of
lost
revenue
annually
nationwide.

Likewise,
the
impact
to
the
sugarcane
industry
would
also
be
substantial.
If
growers
in
the
watersheds
contributing
to
the
Community
Water
Systems
which
find
atrazine
concentrations
exceeding
the
Agency's
level
of
concern,
no
longer
had
atrazine
available
to
them,
a
10
to
40
percent
crop
loss
would
be
incurred
along
with
an
increase
in
alternative
herbicide
cost.
This
translates
to
a
yearly
loss
of
$
89.5
million
but
could
be
as
much
as
$
343.6
million
if
a
40
percent
loss
were
realized.

Finally,
if
atrazine
were
eliminated
from
the
market,
the
most
likely
chemical
broadleaf
weed
control
options
would
be
post­
emergence
applied
herbicides
(
dicamba,
2,4­
D,
bromoxynil,
and
prosulfuron).
Post­
emergence
application
of
herbicides
carries
certain
risks.
These
include:
1)
greater
competition
of
the
weeds
with
the
crop
early
in
the
season
as
weed
control
is
delayed
into
the
growing
season;
2)
crop
injury
from
herbicides
applied
directly
to
the
emerged
crop
and
weeds;
and
3)
if
the
opportunity
to
apply
the
herbicide
is
missed
due
to
weather
or
some
other
factor,
there
are
fewer
or
no
emergency
remedies
for
weed
control.
Thus,
there
are
non­
monetary
costs
that
would
be
associated
with
the
loss
of
atrazine
as
well
as
the
substantial
financial
impacts.

Determination
of
Interim
Reregistration
Eligibility
The
Agency
has
determined
that
atrazine
products
are
eligible
for
reregistration
provided
that:
(
i)
the
circumstances
described
in
this
document
(
including
implementation
of
any
ecological
risk
mitigation
measures
identified
through
the
monitoring
program)
are
realized;
(
ii)
any
current
data
gaps
and
additional
data
needs
are
addressed;
and,
(
iii)
the
consideration
of
the
cumulative
risk
for
the
triazines
supports
a
final
reregistration
eligibility
decision.
Further
we
have
concluded
that
during
the
period
of
data
collection
and
risk
mitigation
measures
called
for
in
this
document,
the
benefits
of
continued
use
of
atrazine
will
outweigh
any
potential
ecological
risk.

Although
the
Agency
has
not
considered
the
cumulative
risk
for
all
the
triazines,
the
Agency
is
issuing
this
amendment
to
the
interim
reregistration
eligibility
decision
now
in
order
to
identify
risk
reduction
measures
that
are
necessary
to
support
the
continued
use
of
atrazine.
Based
on
the
current
evaluation
of
atrazine,
the
Agency
has
determined
that
atrazine
products,
15
unless
used
in
accordance
with
the
conditions
of
this
document,
would
present
risks
inconsistent
with
FIFRA.
Accordingly,
should
a
registrant
fail
to
implement
any
of
the
risk
mitigation
measures
identified
in
this
document,
the
Agency
may
take
further
regulatory
action
to
address
the
risk
concerns
from
the
use
of
atrazine
products.

Because
the
Agency
has
not
yet
considered
cumulative
risk
for
all
of
the
triazines,
this
reregistration
eligibility
decision
does
not
fully
satisfy
the
reassessment
of
the
existing
atrazine
food
residue
tolerances
as
called
for
by
the
Food
Quality
Protection
Act
(
FQPA).
When
the
Agency
has
completed
the
cumulative
assessment,
atrazine
tolerances
will
be
reassessed
in
that
light.
At
that
time,
the
Agency
will
reassess
atrazine
along
with
the
other
triazine
pesticides
to
complete
the
FQPA
requirements
and
make
a
final
reregistration
eligibility
determination.
By
publishing
this
interim
decision
on
reregistration
eligibility
and
requesting
mitigation
measures
now
for
the
individual
chemical
atrazine,
the
Agency
is
not
deferring
or
postponing
FQPA
requirements;
rather,
EPA
is
taking
steps
to
assure
that
uses
which
exceed
FIFRA's
unreasonable
risk
standard
do
not
remain
on
the
label
indefinitely,
pending
completion
of
assessment
required
under
the
FQPA.
This
decision
does
not
preclude
the
Agency
from
making
further
FQPA
determinations
or
tolerance­
related
rulemakings
that
may
be
required
on
this
pesticide
or
any
other
in
the
future.

What
Registrants
Need
to
Do
In
order
to
be
eligible
for
reregistration,
registrants
need
to
implement
the
risk
mitigation
measures
outlined
above,
which
include,
among
other
things,
development
and
submission
of
the
following:

Potential
Effects
of
Atrazine
on
Amphibian
Endocrinology
and
Development
Phase
I:
Response
of
larval
Xenopus
laevis
to
estradiol:
assessment
of
development
and
gonadal
morphology.
Response
of
larval
Xenopus
laevis
to
atrazine:
assessment
of
development
and
gonadal
morphology.

Phase
II:*
Response
of
larval
Xenopus
laevis
to
atrazine:
assessment
of
gonadal
and
plasma
sex
steroid
concentrations.

Phase
III:*
Response
of
larval
Xenopus
laevis
to
atrazine:
assessment
of
gonadal
aromatase
activity.

Phase
IV:*
Response
of
larval
Xenopus
laevis
to
atrazine
and
an
aromatase
inhibitor:
assessment
of
development,
gonadal
morphology,
sex
steroid
concentrations
and
aromatase
activity.

Phase
V:*
Response
of
Rana
pipiens
to
atrazine:
assessment
of
reproductive
fitness.
16
*
Conducting
the
studies
in
phases
II
through
V
are
conditional
on
the
results
from
the
previous
phase
indicating
an
effect.
For
example,
if
morphological
abnormalities
are
observed
in
the
gonads
of
larval
Xenopus
laevis
after
exposure
to
atrazine
(
Phase
I)
then
the
Phase
II
studies
on
gonadal
and
plasma
sex
steroid
concentrations
would
be
conducted.
However,
if
the
Phase
I
studies
show
negative
results
then
the
registrant
does
not
need
to
proceed
with
the
subsequent
study.
EPA
requests
to
review
all
of
the
protocols
before
the
studies
are
initiated.

Ecological
Monitoring
and
Mitigation
of
Atrazine
in
Watersheds
Atrazine
Monitoring
For
Potential
Ecological
Effects
on
Aquatic
Communities:
Part
1.
Flowing
Water
Bodies
in
Corn
and
Sorghum
Use
Areas.

Atrazine
Monitoring
For
Potential
Ecological
Effects
on
Aquatic
Communities:
Part
2.
Water
Bodies
in
Sugarcane
Use
Areas.

Atrazine
Monitoring
For
Potential
Ecological
Effects
on
Aquatic
Communities:
Part
3.
Static
Water
Bodies.

Atrazine
Monitoring
For
Potential
Ecological
Effects
on
Aquatic
Communities:
Part
4.
Estuarine
Water
Bodies.

Data
Call­
In
data
for
the
ecological
monitoring
of
watersheds
will
be
sent
to
Office
of
Pesticide
Programs
(
OPP)
and
Office
of
Water
(
OW),
as
well
as
the
State
or
Tribe
where
the
data
are
collected.
Once
the
monitoring
data
has
been
quality
controlled
it
will
be
posted
in
OW's
publically
available
STORET
database.

If
you
have
questions
on
this
document,
please
contact
the
Chemical
Review
Manager,
Eric
R.
Olson
at
(
703)
308­
8067.

Sincerely,

Betty
Shackleford,
Acting
Director
Special
Review
and
Reregistration
Division
12
Attachments
