1
August
23,
2004
FIFRA
SCIENTIFIC
ADVISORY
PANEL
(
SAP)
OPEN
MEETING
AUGUST
26­
27,
2004
FIFRA
SAP
WEB
SITE
http://
www.
epa.
gov/
scipoly/
sap/
OPP
Docket
Telephone:
(
703)
305­
5805
Docket
Number:
OPP­
2004­
0241
Fumigant
Bystander
Exposure
Model
Review:
The
Fumigant
Exposure
Modeling
System
(
FEMS)
Using
Metam
Sodium
as
a
Case
Study
CHARGE/
QUESTIONS
TO
THE
PANEL
Critical
Element
1:
Documentation
Question
1:
The
background
information
presented
to
the
SAP
panel
by
the
FEMS
developers
provides
both
user
guidance
and
a
technical
overview
of
the
system.
Is
this
document
sufficiently
detailed
and
understandable?
Are
the
descriptions
of
the
specific
model
components
scientifically
sound?
Do
the
algorithms
in
the
annotated
code
perform
the
functions
as
defined
in
this
document?
Were
the
panel
members
able
to
load
the
software
and
evaluate
the
system
including
the
presented
case
study?

Critical
Element
2:
System
Design/
Inputs
Question
2:
In
Section
2.1:
Overview
of
Conceptual
Model
of
the
background
document,
a
series
of
flowcharts
(
Figures
2,
3,
and
4)
are
presented
that
detail
the
individual
processes
and
components
that
are
included
in
FEMS.
The
key
processes
include
(
1)
emissions
processing,
(
2)
200
year
weather
inputs
and
how
they
are
used
for
longer­
term
Monte­
Carlo
sampling;
and
(
3)
TOXST
analysis.
What
can
the
panel
say
about
these
proposed
processes,
the
nature
of
the
components
included
in
FEMS
and
the
data
needed
to
generate
an
analysis
using
FEMS?
Are
there
any
other
potential
critical
sources
of
data
or
methodologies
that
should
be
considered?

Question
3:
The
determination
of
appropriate
flux/
emission
rates
is
critical
to
the
proper
use
of
the
FEMS
model
as
these
values
define
the
source
of
fumigants
in
the
air
that
can
lead
to
exposures.
There
are
different
methods
of
determining
flux/
emission
rates
from
empirical
data
including
direct
measurements
and
what
is
referred
to
as
the
"
indirect"
or
"
back­
calculation"
method.
Direct
measurement
of
flux
is
not
that
common
in
the
available
data
because
of
the
difficulties
and
expense
associated
with
generating
these
types
of
data.
The
"
indirect"
method
is
most
commonly
used
and
involves
fitting
monitoring
data
with
ISC
to
determine
flux/
emission
rates.
Upon
its
review
of
how
flux
rates
can
be
calculated,
the
Agency
has
identified
a
number
of
questions
it
would
like
the
panel
to
consider.
The
emission
fitting
procedures
used
in
FEMS
are
based
on
least
squares
analyses
of
log­
transformed,
dispersion
modeling
and
field
monitoring
data.
What,
if
any
refinements
are
needed
for
this
process?
Is
it
appropriate
to
log
transform
2
these
types
of
data
for
back­
calculation
purposes
and
to
use
a
least­
squares
regression
analysis
which
implicitly
assumes
that
the
fitted
line
passes
through
the
origin?
How
appropriate
is
it
to
use
a
flux/
emission
factor
from
a
single
monitoring
study
(
or
small
number
of
studies)
and
apply
it
to
different
situations
such
as
for
the
same
crop
in
a
different
region
of
the
country?
Does
the
panel
believe
that
FEMS
could
adequately
consider
multiple,
linked
application
events
as
well
as
single
source
scenarios?
Does
FEMS
appropriately
address
situations
where
data
are
missing
(
i.
e.,
is
the
data
filling
procedure
appropriate)?
Should
there
be
a
threshold
r2
value
below
which
a
regression
of
measured
versus
modeled
air
concentrations
should
not
be
used
in
flux
rate
determinations?
What
are
possible
alternative
approaches?

Question
4:
The
integration
of
actual
time­
base
meteorological
data
into
ISCST3
is
one
of
the
key
components
that
separates
the
FEMS
methodology
from
that
being
employed
by
the
Agency
in
its
current
assessment.
The
Agency
has
identified
several
potential
sources
of
these
data
including
the
National
Weather
Service,
Federal
Aviation
Administration,
California
Irrigation
Management
Information
System
(
CIMIS),
and
the
Florida
Automated
Weather
Network
(
FAWN).
The
Agency
is
also
aware
that
there
are
several
approaches
that
can
be
used
to
process
meteorological
data
and
acknowledges
that
FEMS
used
PCRAMMET
which
is
a
standard
Agency
tool
for
this
purpose.
Upon
its
review
of
what
meteorological
data
are
available
and
how
it
can
be
processed
for
use
in
an
assessment
such
as
this,
the
Agency
has
identified
a
number
of
questions
it
would
like
the
panel
to
consider.
The
test
case
example
in
FEMS
is
based
on
the
National
Weather
Service
ASOS
meteorological
monitoring
station
in
Fresno,
California.
What
are
the
SAP's
thoughts
on
the
use
of
National
Weather
Service
/
Federal
Aviation
Administration
meteorological
data
sets
in
comparison
with
either
CIMIS
or
FAWN
for
this
type
of
application?
What
criteria
should
be
used
to
identify
meteorological
regions
for
analysis
and
how
should
specific
monitoring
data
be
selected
from
within
each
region?
Anemometer
sampling
height
has
been
identified
as
a
concern
by
the
Agency
in
preparation
for
this
meeting.
For
example,
some
data
are
collected
at
2
meters
while
others
are
collected
at
a
height
of
10
meters.
What
are
the
potential
impacts
of
using
either
type
of
data
in
an
analysis
of
this
nature?
FEMS
uses
"
assumed
distributions"
to
account
for
uncertainty
in
the
meteorological
data
based
on
Hanna,
1998
[
as
referenced
in
the
FEMS
background
paper].
Is
this
an
appropriate
technique?
Does
FEMS
treat
stability
class
inputs
appropriately,
especially
the
quantitative
manipulations
of
these
data
that
have
been
completed?
Is
the
concurrent
use
of
emissions
and
meteorological
conditions
in
FEMS
useful
in
identifying
concurrent
upper­
end
conditions
that
could
lead
to
peak
exposures
for
bounding
exposure
events?

Question
5:
The
Agency
model,
ISCST3
is
the
basis
for
the
FEMS
approach.
This
model
has
been
peer
reviewed
and
is
commonly
used
for
regulatory
purposes
by
the
Agency.
FEMS
also
uses
other
Agency
systems
such
as
PCRAMMET
and
TOXST.
Are
there
specific
recommendations
that
the
panel
can
make
with
regard
to
any
parameter
that
should
be
altered
to
optimize
the
manner
that
they
are
used
in
FEMS?
ISCST3
can
treat
"
calm"
(
i.
e.,
periods
where
the
windspeed
in
essentially
0)
in
one
of
two
ways
including
the
concentration
is
set
to
(
0)
and
an
approach
that
uses
the
last
non­
calm
wind
direction/
concentration.
FEMS
uses
the
first
approach.
Does
the
panel
concur?
In
3
Section
2.2
Specific
Technical
Considerations
With
Regard
To
The
Design
Of
FEMS
of
the
background
document,
there
is
a
section
entitled
Computing
Endpoint
Distances.
Please
comment
on
the
procedures
included
in
this
section?
The
FEMS
analysis
is
based
on
a
single
field
being
treated
once
per
year.
On
this
basis,
ISCST3
files
include
200
full
years
of
hour­
by­
hour
sequential
data.
Application
start
times
are
randomly
selected
to
match
the
user­
supplied
application
frequency.
For
example,
if
a
model
user
entered
10,000
simulations,
there
will
be
approximately
10,000
randomly
selected
start
times
with
batch
modeling
treatment
of
4
days
duration
for
each
application.
In
addition,
FEMS
allows
for
more
than
one
application
per
year
to
be
modeled.
Does
the
panel
view
this
as
an
appropriate
process?
If
not
can
it
make
suggest
recommendations
or
modifications
that
may
improve
this
process?
Can
the
panel
comment
on
the
source
geometry
used
in
FEMS
and
the
implications
of
this
choice?

Critical
Element
3:
Results
Question
6:
Soil
fumigants
can
be
used
in
different
regions
of
country
under
different
conditions
and
they
can
be
applied
with
a
variety
of
equipment.
Does
the
SAP
believe
that
the
methodologies
in
FEMS
can
be
applied
generically
in
order
to
assess
a
wide
variety
of
fumigant
uses?
What
considerations
with
regard
to
data
needs
and
model
inputs
should
be
considered
for
such
an
effort?

Question
7:
Does
FEMS
adequately
identify
and
quantify
airborne
concentrations
of
soil
fumigants
that
have
migrated
from
treated
fields
to
sensitive
receptors?
The
Agency
is
particularly
concerned
about
air
concentrations
in
the
upper
ends
of
the
distribution.
Are
these
results
presented
in
a
clear
and
concise
manner
that
would
allow
for
appropriate
characterization
of
exposures
that
could
occur
at
such
levels?

Question
8:
A
sensitivity
analysis
has
been
conducted
and
is
described
in
the
FEMS
background
document.
What
types,
if
any,
of
additional
contribution/
sensitivity
analyses
are
recommended
by
the
panel
to
be
the
most
useful
in
making
scientifically
sound,
regulatory
decisions?
What
should
be
routinely
reported
as
part
of
a
FEMS
assessment
with
respect
to
inputs
and
outputs?
Are
there
certain
tables
and
graphs
that
should
be
reported?
What
types
of
further
evaluation
steps
does
the
panel
recommend
for
FEMS?
