April
4,
1996
EPA­
SAB­
CASAC­
LTR­
96­
006
Honorable
Carol
M.
Browner
Administrator
U.
S.
Environmental
Protection
Agency
401
M.
Street
SW
Washington,
DC
20460
RE:
Closure
by
the
Clean
Air
Scientific
Advisory
Committee
(
CASAC)
on
the
Secondary
Standard
Portion
of
the
Staff
Paper
for
Ozone
Dear
Ms.
Browner:

A
Panel
of
the
Clean
Air
Scientific
Advisory
Committee
(
CASAC)
of
EPA's
Science
Advisory
Board
(
SAB)
met
on
March
22,
1995,
to
review
a
draft
of
the
primary
standard
portion
of
the
document
entitled
Review
of
National
Ambient
Air
Quality
Standards
for
Ozone
Assessment
of
Scientific
and
Technical
Information
­
OAQPS
Staff
Paper.
At
that
time,
a
draft
of
the
secondary
standard
portion
of
the
document
was
not
completed.
In
August,
1995,
a
revised
Staff
Paper,
which
included
a
first
draft
of
the
secondary
standard
portion
was
sent
to
the
CASAC
panel
members
for
review.
On
September
19
and
20,
1995,
the
Panel
met
to
complete
this
review.
The
Panel
members'
comments
reflect
their
satisfaction
with
the
improvements
made
in
the
scientific
quality
and
completeness
of
the
primary
standard
portion
of
the
Staff
Paper
and
reached
closure
on
that
part
(
see
CASAC
Letter
Report:
EPA­
SAB­
CASAC­
LTR­
96­
002,
November
30,
1995).
However,
the
Panel
could
not
come
to
closure
on
the
secondary
standard
portion
of
the
Staff
Paper
which
was
a
first
draft.
To
facilitate
further
development
of
this
part
of
the
Staff
Paper,
the
Panel
members
provided
detailed
comments
to
your
staff.
The
Panel
felt
that
the
suggested
revisions
were
extensive
enough
to
warrant
a
review
of
the
next
draft.

On
March
21,
1996,
a
subset
of
the
Panel,
consisting
of
all
four
of
the
Panel
members
with
expertise
in
ozone
effects
on
vegetation
plus
three
additional
CASAC
members,
met
in
Research
Triangle
Park,
NC
to
review
a
second
draft
of
the
secondary
2
portion
of
the
Staff
Paper.
In
addition,
a
Panel
member
with
expertise
in
economics
reviewed
the
Staff
Paper
and
provided
written
comments.
Overall,
the
comments
from
the
Panel
members
reflected
their
satisfaction
that
the
Staff
Paper
was
much
improved;
however,
the
verbal
and
written
comments
provided
to
your
staff
indicated
that
important,
additional
modifications
are
still
required.
Nevertheless,
it
was
the
consensus
of
the
Panel
that
an
additional
review
of
the
document
by
the
Panel
was
not
necessary.
Consequently,
the
majority
of
the
Panel
agreed
to
come
to
closure
on
the
Staff
Paper
assuming
that
the
Agency
would
incorporate
the
Panel's
latest
comments.
It
was
the
opinion
of
six
of
the
seven
members
of
the
Panel
who
were
present
that
the
Staff
Paper
will
provide
an
appropriate
scientific
basis
for
making
regulatory
decisions
concerning
a
secondary
ozone
standard
once
the
additional
changes
are
incorporated.
The
additional
modifications
are
summarized
below.

It
should
be
pointed
out
that
the
Panel
members
all
agreed
that
damage
is
occurring
to
vegetation
and
natural
resources
at
concentrations
below
the
present
1­
hour
national
ambient
air
quality
standard
(
NAAQS)
of
0.12
ppm.
The
vegetation
effects
experts
were
in
agreement
that
plants
appear
to
be
more
sensitive
to
ozone
than
humans.
Further,
it
was
agreed
that
a
secondary
NAAQS,
more
stringent
than
the
present
primary
standard,
was
necessary
to
protect
vegetation
from
ozone.
However,
agreement
on
the
level
and
form
of
such
a
standard
is
still
elusive
for
a
number
of
reasons.

The
first
issue
is
the
level
of
uncertainty
associated
with
the
crop
loss
risk
assessment
presented
in
Tables
VII­
5a­
d
through
VII­
7
of
the
Staff
Paper.
While
some
of
the
sources
of
uncertainty
are
addressed
earlier
in
the
Staff
Paper,
other
sources
of
uncertainty
are
not
addressed
at
all.
The
estimates
in
these
Tables
should
only
be
presented
as
rough
estimates
for
a
number
of
reasons.
First,
the
dose­
response
functions
are
based
upon
open­
top
chamber
studies
which
have
the
advantage
of
providing
the
least
amount
of
environmental
modification
of
any
outdoor
chamber,
but,
nevertheless,
they
still
alter
ambient
microclimate
conditions
which
will
introduce
uncertainty.
In
these
studies,
plant
response
to
ozone
has
been
optimized
under
conditions
which
do
not
reflect
the
real­
life
ambient
field
conditions.
Two
of
the
plant
experts
said
that
the
open­
top
chamber
experiments
by
their
very
design
and
execution
produced
results
that
overestimated
the
effects
of
ozone
on
plant
yield.
The
other
two
experts
agreed
that
the
open­
top
chambers
do
alter
the
environment
in
the
chamber
with
respect
to
ambient
field
conditions
but
did
not
agree
with
there
being
a
positive
bias.
Research
has
not
yet
provided
methods
that
clearly
are
better
than
open­
top
chambers
for
establishing
ozone
dose­
response
relationships
for
a
wide
variety
of
3
crops.
Second,
the
estimated
exposures
are
based
on
a
non­
peer­
reviewed,
empirical
model
which
has
not
been
subjected
to
any
performance
evaluation.
In
addition,
insufficient
details
are
given
either
in
the
Staff
Paper
or
the
unpublished
Agency
report
for
anyone
to
perform
an
evaluation.
Third,
the
estimated
exposures
are
then
extrapolated
to
hypothetical
scenarios
where
various
secondary
NAAQS
are
attained.
Details
of
this
extrapolation
procedure
are
also
insufficient
to
judge
the
appropriateness
of
the
procedure.
Fourth,
the
exposure
estimates
are
then
extrapolated
to
the
entire
coterminous
U.
S.
using
a
Geographic
Information
System
(
GIS)
which
is
based
on
an
unpublished,
non­
peer­
reviewed,
internal
EPA
memorandum
that
contains
insufficient
details
to
adequately
evaluate
the
GIS.
The
exposure
estimates
and
the
dose­
response
function
estimates
are
then
input
into
the
economic
models
which
introduce
additional
uncertainties.
Furthermore,
the
losses
are
computed
from
an
assumed
12­
hr.
background
ozone
concentration
of
0.025
ppm
which
is
too
low
and
will
over­
inflate
the
crop
loss
estimates.
A
more
reasonable
12­
hr.
daylight,
summertime
background
is
more
likely
closer
to
the
8­
hr.
background
of
0.03­
0.05
ppm.
As
a
result,
the
Panel
felt
that
the
absolute
values
of
the
numbers
in
Tables
VII­
5a­
VII­
7
are
highly
uncertain
estimates
of
crop
losses
and
are
a
result
of
a
propagation
of
uncertainties.
They
are
rough
estimates,
and
this
should
be
explicitly
stated
in
this
discussion.
The
Panel
believes,
however,
that
these
Tables
can
be
of
some
use
in
identifying
rough
relative
incremental
benefits
associated
with
a
given
NAAQS
as
long
as
it
is
recognized
that
small
differences
in
benefits
may
have
no
significance
because
of
these
uncertainties.

A
related
issue
is
the
estimated
yield
losses
and
seedling
biomass
losses
displayed
on
the
maps
in
Appendix
E
of
the
Staff
Paper.
Since
these
are
also
based
on
the
results
of
open­
top
chamber
experiments
as
well
as
the
results
of
the
GIS
technology
approach,
the
uncertainties
are
large.
The
concern
here
is
that
the
maps
will
be
used
out
of
context
and
the
caveats
ignored.
The
limitations
and
uncertainties
of
the
data
need
to
be
clearly
stated
in
the
legend
of
each
map.

The
SUM06
standard
reflects
a
change
in
thinking
over
the
current
1­
hour
standard
with
respect
to
how
plants
respond
to
ambient
ozone
exposure.
This
proposed
form
of
the
standard
implicitly
recognizes
that
vegetation
response
to
ambient
ozone
is
cumulative.
However,
there
is
disagreement
over
whether
this
is
the
best
form
for
a
cumulative
standard
and
what
the
level
of
the
standard
should
be
to
protect
vegetation
from
damage
by
ozone.
One
of
the
Panel's
ecology
experts
thinks
the
form
and
the
range
of
between
25
to
38
ppm­
hours
proposed
by
the
Agency
is
appropriate.
A
second
expert
thinks
the
form
proposed
by
the
Agency
is
appropriate
4
and
biologically
based,
but
feels
that
a
level
of
20
ppm­
hours
is
necessary
to
adequately
protect
natural
resources.
The
other
two
experts
are
uncomfortable
with
a
SUM06
form
because
they
feel
it
lacks
a
biological
basis.
One
member
stated
that
he
feels
very
uncomfortable
with
SUM06
and
would
not
want
to
defend
it
because
he
feels
there
is
too
much
uncertainty
associated
with
its
derivation.
The
fourth
expert
is
concerned
that
a
SUM06
form
is
unnecessarily
complicated,
and
the
level
proposed
by
the
Agency
would
not
eliminate
ozone
damage.
Instead,
he
proposes
that
the
1­
hour
average
ozone
should
not
exceed
0.05
ppm
for
more
than
one
hour
between
the
hours
of
0700­
1500.
In
his
written
comments,
the
Panel's
economist
noted
that
the
welfare
benefits
of
a
secondary
standard
depend
on
the
decision
regarding
the
primary
standard.
For
example,
he
points
out
that
if
the
primary
standard
remains
at
0.12
ppm
for
1­
hour,
or
is
changed
to
an
8­
hour
standard
of
0.09
ppm
with
one
allowable
exceedence,
Table
VII­
5a
suggests
potentially
significant
incremental
benefits
associated
with
a
secondary
standard
based
on
SUM06.
He
further
states
that
if
the
primary
standard
is
set
at
0.07
or
0.08
ppm
with
one
exceedence,
there
is
little
to
be
gained
by
establishing
a
separate
secondary
standard.

Although
the
three
remaining
CASAC
members
were
neither
biologists
or
economists,
they
offered
their
opinion
on
the
secondary
standard
proposals.
Two
think
the
form
proposed
by
the
Agency
is
appropriate.
One
thinks
that
the
level
proposed
by
the
Agency
is
appropriate,
while
the
other
feels
that
the
Administrator's
discretion
should
be
broader
than
the
range
presented
in
the
Staff
Paper.
One
of
these
members
pointed
out,
however,
that
the
Staff
Paper
does
not
make
it
clear
enough
that
the
SUM06
standard
as
proposed
is
a
practical
choice
being
made
as
to
the
level
of
effects
that
will
be
tolerated
and
not
a
level
that
will
prevent
effects
from
occurring.
The
third
is
uncomfortable
with
SUM06
and
based
on
the
estimates
in
Tables
VII­
5a­
VII­
7,
recommends
an
8­
hour
standard
at
the
same
level
as
the
new
primary
standard.
The
three
members
also
concurred
that
given
the
crudeness
of
the
risk
assessment
estimates,
policy
decisions
cannot
be
based
firmly
on
science.

A
number
of
the
Panelists
offered
their
insights
as
to
why
there
are
such
divergent
opinions
on
the
recommended
form
and
level
of
the
standard.
The
main
issues
are
the
lack
of
sufficient
rural
ozone
data,
and
the
lack
of
relevant
plant
exposure
studies.
There
are
serious
deficiencies
in
terms
of
the
distribution
of
monitoring
sites,
particularly
in
rural
areas
that
prevent
us
from
accurately
assessing
exposure
once
ozone
damage
is
observed.
The
Panel
is
in
agreement
that
plants
are
being
damaged
by
ozone
and
that
the
current
secondary
standard
is
not
sufficiently
protective,
but
there
remain
important
limitations
to
our
understanding
of
the
extent
of
5
the
response
of
vegetation
to
ozone
under
field
conditions.
Five
years
from
now,
if
we
do
not
have
the
results
of
research
coupling
ozone
air
quality
and
plant
biology
under
conditions
more
representative
of
ambient
field
conditions,
to
avoid
the
shortcomings
of
the
open­
top
chamber
experiments,
then
we
will
continue
to
be
hampered
by
our
inability
to
come
to
consensus
on
the
levels
of
air
quality
that
are
protective
of
vegetation
and
ecosystems
at
the
most
reasonable
cost.
In
addition,
a
number
of
Panelists
expressed
the
importance
of
knowing
the
consequences
of
decisions
concerning
National
Ambient
Air
Quality
Standards.
Once
a
decision
is
made
to
change
the
standard
or
to
maintain
the
status
quo,
we
must
be
able
to
determine,
by
appropriate
monitoring
and
research,
what
the
consequences
will
be
in
terms
of
ambient
air
quality
and
effects
on
vegetation
and
ecosystems.

In
summary,
a
majority
of
the
Panel
has
come
to
closure
on
the
secondary
part
of
the
ozone
Staff
Paper
despite
the
desire
of
the
Panel
for
additional
significant
revisions.
These
revisions
have
been
communicated
to
your
staff
by
this
letter
and
in
written
comments
by
individual
Panel
members.
The
Panel
trusts
that
your
staff
will
address
these
concerns.

CASAC
would
appreciate
being
kept
informed
of
progress
on
establishing
a
revised
or
new
ozone
standard,
and
plans
for
research
on
ozone
effects.
Please
do
not
hesitate
to
contact
me
if
CASAC
can
be
of
further
assistance
in
this
matter.
We
look
forward
to
seeing
the
final
version
of
the
secondary
standard
portion
of
the
Staff
Paper.

Sincerely,

Dr.
George
T.
Wolff,
Chair
Clean
Air
Scientific
Advisory
Committee
NOTICE
This
report
has
been
written
as
part
of
the
activities
of
the
Science
Advisory
Board,
a
public
advisory
group
providing
extramural
scientific
information
and
advice
to
the
Administrator
and
other
officials
of
the
Environmental
Protection
Agency.
The
Board
is
structured
to
provide
balanced,
expert
assessment
of
scientific
matters
related
to
problems
facing
the
Agency.
This
report
has
not
been
reviewed
for
approval
by
the
Agency
and,
hence,
the
contents
of
this
report
do
not
necessarily
represent
the
views
and
policies
of
the
Environmental
Protection
Agency,
nor
of
other
agencies
in
the
Executive
Branch
of
the
Federal
government,
nor
does
mention
of
trade
names
or
commercial
products
constitute
a
recommendation
for
use.
SCIENCE
ADVISORY
BOARD
CLEAN
AIR
SCIENTIFIC
ADVISORY
COMMITTEE
OZONE
PANEL
ROSTER
­
MARCH
21,
1996
MEETING
Secondary
Standard
Review
Chair
Dr.
George
T.
Wolff,
General
Motors
Environmental
&
Energy
Staff,
Detroit,
MI
Members
Dr.
Stephen
M.
Ayres,
Office
of
International
Health
Programs,
Virginia
Commonwealth
University,
Medical
College
of
Virginia,
Richmond,
VA
Dr.
Philip
K.
Hopke,
Department
of
Chemistry,
Clark
University,
Potsdam,
NY
Dr.
Jay
S.
Jacobson,
Boyce
Thompson
Institute,
Cornell
University,
Ithaca,
NY
Dr.
Joe
L.
Mauderly,
Inhalation
Toxicology
Research
Institute,
Lovelace
Biomedical
&
Environmental
Research
Institute,
Albuquerque,
NM
Dr.
James
H.
Price,
Jr.,
Research
&
Technology
Section,
Texas
Natural
Resource
Conservation
Commission,
Austin,
TX
Consultants
to
CASAC
Dr.
A.
Myrick
Freeman,
Professor,
Department
of
Economics,
Bowdoin
College,
Brunswick,
ME
Dr.
Allan
Legge,
Biosphere
Solutions,
Calgary,
Alberta,
CANADA
Dr.
William
Manning,
Department
of
Plant
Pathology,
University
of
Massachusetts,
Amherst,
MA
Dr.
George
Taylor,
Biological
Services
Center,
Desert
Research
Institute,
University
of
Nevada,
Reno,
NV
Science
Advisory
Board
Staff
Mr.
A.
Robert
Flaak,
Designated
Federal
Official,
U.
S.
Environmental
Protection
Agency,
Science
Advisory
Board
(
1400F),
Washington,
DC
20460
Mrs.
Dorothy
Clark,
Staff
Secretary,
U.
S.
Environmental
Protection
Agency,
Science
Advisory
Board
(
1400F),
Washington,
DC
20460
DISTRIBUTION
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Assistant
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Director,
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Science
Policy,
ORD
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