"
Grahame,
Thomas"
<
Thomas.
Grahame@
HQ.
DOE.
GOV>

07/
06/
2006
02:
34
PM
T
o
"
Flynn,
Amy
E."
<
Amy_
E._
Flynn@
omb.
eop.
gov>,
"
Fraas,
Arthur
G."
<
Arthur_
G._
Fraas@
omb.
eop.
gov>,
Jason
Burnett/
DC/
USEPA/
US@
EPA,
"
Fredriksen,
Kathy"
<
Kathy.
Fredriksen@
hq.
doe.
gov>
c
c
"
Difiglio,
Carmen"
<
Carmen.
Difiglio@
hq.
doe.
gov>,
"
Daniels,
Jarad"
<
Jarad.
Daniels@
hq.
doe.
gov>
S
u
b
j
e
c
t
quote
from
Delfino
et
al
(
1998)
showing
necessity
to
use
multi­
pollutant
models
Everyone,
it
struck
me
that
not
everyone
on
the
call
at
3
PM
would
necessarily
understand
why
multi­
pollutant
modeling
is
more
robust
than
single
pollutant
models.
Long
story
short,
pollutants
(
and
other
independent
variables)
are
often
highly
correlated,
so
several
could
be
significant
in
single
pollutant
models.
For
example,
NO2
and
CO
and
often
PM2.5
are
usually
highly
correlated
in
central
monitor
studies,
so
in
single
pollutant
models,
they
might
all
be
significant.
Modelers
often
start
with
preliminary
single
pollutant
models
to
get
a
feel
for
which
variables
are
most
important.
But
they
then
go
to
multi­
pollutant
models
to
discern
which
pollutants
or
other
variables
have
the
strongest
associations,
the
greatest
explanatory
power.

This
is
why
we
underline
the
importance
of
using
results
from
multi­
pollutant
models.
For
instance,
a
Delfino
et
al
(
1998)
study,
which
in
the
end
found
robust
associations
between
ozone
and
emergency
room
visits
for
respiratory
illnesses
for
the
elderly,
contains
the
following
quotation:
"
Although
there
were
adverse
effects
of
estimated
PM2.5
on
ER
visits
for
respiratory
illnesses
among
the
elderly
[
note:
in
a
single
pollutant
model],
the
association
was
unstable
and
completely
confounded
by
both
temperature
and
O3...
it
is
reasonable
to
accept
only
the
most
robust
findings
as
meaningful
to
community
health 
therefore
the
present
discussion
will
focus
on
the
most
notable
finding
of
adverse
affects
of
O3
among
the
elderly "
(
italics
ours)

Hope
this
is
useful,

Tom
Thomas
J.
Grahame
U.
S.
Department
of
Energy
1000
Independence
Ave.,
SW
Washington,
DC
20585
202
586
7149
(
voice)

202
586
7085
(
fax)
