  
REVISING THE AIR QUALITY STANDARDS
A Briefing Paper on the Proposed
National Ambient Air Quality Standards
for Particulate Matter and Ozone
By J.W. Anderson
Introduction
The Case for
Particulate Matter (PM)
How much tighter is
the proposed PM standard than the current one?
What are the sources of
PM, and how can it be reduced?
How reliable are
EPA's estimates of deaths and illnesses caused by PM?
Why choose 2.5 microns
as the crucial dimension?
Why propose an annual
average of 15 micrograms per cubic meter as the standard?
Where did that figure come from?
How does EPA define
attainment for PM?
What are the costs and
benefits of a tighter PM standard?
The Case for Ozone
How much tighter
is the proposed ozone standard than the current one?
What are ozone's
sources?
What are the health
effects of ozone?
Why choose 0.08 parts per
million as the standard?
How does EPA define
attainment for ozone?
What are the costs
and benefits of a tighter ozone standard?
What is EPA's
secondary standard for ozone?
What are ozone's
transport issues?
INTRODUCTION
The U.S. Environmental Protection Agency has proposed
new national air quality standards for two widespread
pollutants, ground-level ozone and particulate matter.
This paper summarizes the proposals and points out some
of the issues that they raise.
The EPA's case for tightening the standard for
particulate matter (PM) is much stronger than its case
for a tighter ozone standard. The primary standard for a
pollutant is explicitly designed to protect human health.
There are questions about the health data for both
particulates and ozone, but the findings on particulates
are much more solid, and point to more serious damage to
health, than those on ozone. Achieving either standard
would be costly. According to the EPA as well as most
other observers, the country would get a much higher
return for its money, in terms of health benefits, from
abatement expenditures on PM than on ozone.
The language of the Clean Air Act, now arguably
obsolete, raises a major issue. The EPA cannot carry out
the letter of the law because the science, as it has
evolved, does not provide clear thresholds for harm. When
the original law was enacted in 1970 its authors in
Congress built it on an assumption that every pollutant
has a threshold---a concentration below which it is too
thinly dispersed to have any effects. Congress told the
EPA to find that threshold and set the standard below it
at a level that would protect public health "with an
adequate margin of safety," as the Act puts it. But
as methods of measurement become more sensitive and these
issues are studied more carefully, the impossibility of
finding zero-risk levels becomes clearer. Some pollutants
have no thresholds and, the EPA says, both PM and ozone
may be among them.
The result is that the EPA is required to make policy
judgments about how far to go in tightening standards,
but these judgments are open to attack in the courts.
Meanwhile the economic costs of compliance rise steeply
as the standards get tighter, although the EPA is not
permitted to take the economic costs into account in
setting them.
Recent epidemiological studies have found adverse
health effects below the present standard for both PM and
ozone. That has opened the EPA to legal attack for
failing to carry out the law. The American Lung
Association sued the EPA over the PM standard, resulting
in a court order setting deadlines last November for the
proposal and next July for the final decision. The EPA is
vulnerable to similar litigation on the ozone.
Ozone in particular has been a subject of rising
concern in the EPA and the environmental organizations,
with deadlines for national compliance repeatedly set by
legislation and never met. It has taken on a large
symbolic importance among the forces on both sides of the
issue. Among those pressing for more rigorous
enforcement, it has become a symbol of reluctance and
foot-dragging on the part of many industries, some state
governments and, perhaps, many motorists as well. But to
those industries and states, and not to them alone, it is
a symbol of a poorly written law that insists on heavy
costs regardless of whether they produce commensurate
benefits to health.
EPA explains that it is handling the two separate
proposals together because ozone and PM have some of the
same precursor gases and some of the same health effects.
The atmospheric chemistry of the two pollutants also have
similarities, and measures to control one will affect the
other. But that can be said of most of the common air
pollutants. To the extent that the two issues, PM and
ozone, can be folded together, the death rates associated
with PM will overshadow the public discussion and
diminish attention to the troubling economic questions
about the ozone standard.
Actually achieving the proposed standards will require
more than a decision in Washington. The EPA shares
responsibility for implementation with state and local
authorities, who have to adopt and carry out specific
control measures. Many of them have been struggling for
years to meet the present ozone standard without great
success. For some cities, meeting even the present ozone
standard may actually be impossible.1 Some cities have
not attained the present PM standard, and many states
have so little data on the small particles that are the
target of the proposed regulation that they do not know
how far they may have to go to comply, or even whether
they are now in violation.
Schedule: EPA has held hearings and is now accepting
public comments on the proposals. Congressional hearings
have been scheduled. The EPA is to announce final
decision on both pollutants by July 19. Congress will
then have 60 days to hold a vote on the new regulations,
if it wishes. The EPA's proposals include detailed
transition rules to move the states' planning processes
from the present standards to the new ones.
A note on process.
The EPA begins the process of setting a standard by
drawing together all of the scientific data into a
compilation known as the Criteria Document. It is, in
effect, a massive textbook on the subject. The Criteria
Document for the proposed PM standards runs to some 2400
pages. In the next step the EPA produces what it calls a
Staff Paper, drawing policy conclusions from the
scientific information in the Criteria Document. Both of
these documents are circulated to its Clean Air
Scientific Advisory Committee (CASAC), a group of
specialists from academia and industry who review them
for technical quality. CASAC may send the documents back
to the EPA staff from revision. When they have come to
agreement, CASAC sends the administrator of the EPA a
letter stating its views. With that, all of these
documents go to the administrator for her decision on the
proposed standards. At the same time, the EPA staff
develops a Regulatory Impact Analysis, estimating the
economic impact. That's where the proposals for new PM
and ozone standards now stand.
When new standards become final, the EPA asks the
states how they propose to meet them. Each state
government then draws up a State Implementation Plan
(SIP), following a format laid down by the EPA. On the
basis of computer models of the relationships between
emissions and ambient pollution, the states calculate how
much pollution reduction to expect from given changes in
emissions controls. The EPA oversees this procedure and
must approve the states' plans. States are threatened
with a loss of federal highway funds if they fail to
comply.
The current primary National Ambient
Air Quality Standard for particulate matter is an annual
average concentration of 50 micrograms per cubic meter of
air of PM10 , which means particles 10 microns in
diameter or less. (A micron is a millionth of a meter.)
The standard also sets a maximum 24-hour concentration
for PM10 of 150 micrograms per cubic meter.
But toxicological research with test
animals and knowledge of human physiology suggests that
it is fine particles, those 2.5 microns in diameter or
less, that do most of the damage to health. For that
reason the EPA now proposes to add a new standard for
PM2.5. It would set a maximum annual average for PM2.5 of
15 micrograms per cubic meter, and a maximum 24-hour
concentration of 50 micrograms per cubic meter.
Health effects: The EPA concludes from
the epidemiological studies that PM is closely associated
with premature deaths. Reviewing many studies, it finds a
statistically significant correlation between
concentrations of PM2.5 and premature deaths, as well as
aggravation of pulmonary and cardiovascular disease. (25)2.
Subpopulations potentially more sensitive to PM than
the general population are children, the elderly,
asthmatics, people with pulmonary or cardiovascular
disease, and people with infectious respiratory disease
like pneumonia.(41-2).
How many deaths? The EPA estimates that carrying out
the proposed PM2.5 standard would avoid 20,000 premature
deaths a year. That is in addition to the deaths avoided
by the present PM10 standard if it were fully achieved
throughout the country.3
This estimate of mortality depends chiefly on one large
study of long-term exposure 4, correlating
concentrations of fine PM in 151 metropolitan areas
throughout the United States over seven years with deaths
among the 550,000 people being studied. Many other
studies have shown a short-term correlation with
mortality---that is, a correlation between the daily ups
and downs of PM concentrations and mortality.
The EPA also provides mortality estimates for two
cities, one with much more heavily polluted air than the
other. If Los Angeles County were to get its PM
concentrations down to the present standard for PM10, the
EPA calculates that the PM2.5 contained in that PM10
would still be associated with 400 to 1000 deaths a year
(74).5 That
represents 2 to 4 per cent of the total deaths in the
county.
Unlike Los Angeles, Philadelphia is already well below
the national standard for PM10. The EPA says that the
mortality in Philadelphia associated with the present
level of PM2.5 is 200 to 500 deaths a year (74-5)6 That's roughly 1 to
2.5 per cent of all deaths in Philadelphia.
The EPA believes that coarser particles, between 2.5
and 10 microns, can cause serious damage at high
concentrations. (64, 92). That's why it wants to retain
the present PM10 rules as well as adding the new ones for
PM2.5.
How much tighter is the proposed PM
standard than the current one?
On average, very broadly, PM2.5
constitutes about half of PM10, although the actual
proportion varies greatly from one locality to another.
The stringency of the proposed regulation can best be
judged by the number of counties that would be in
violation. At present 41 counties are in violation of the
current standard for PM10, according to a list that the
EPA has posted on the Internet. According to the same
list, 167 counties would be in violation of the proposed
standard for PM2.5.
What are the sources of PM, and
how can it be reduced?
The major source is the burning of
fossil fuels, especially coal in large industrial plants
like utilities' power generating stations. But it also
comes from fuel burned on the highway, in both diesel and
gasoline engines, and from burning vegetation and
smelting metals. PM in general includes a lot of
material---dust, for example, and pollen---of natural
origin. But most of the natural PM is larger than 2.5
microns. Much PM is not emitted as particles but is
formed from gases such as sulfur dioxide and nitrogen
oxides. Reducing fine PM means either burning less, or
burning it more cleanly.
How reliable are EPA's
estimates of deaths and illnesses caused by PM?
EPA states clearly that no one has
a definitive explanation of the mechanism---the
physiological cause-and-effect---by which PM damages
people's health. The agency is working from an
accumulation of some 80 epidemiological studies, of which
more than 60 show significant correlations between PM in
the air and health effects among those who breathe it.
(52) The EPA is careful never to say that PM causes
death and illness, but only that PM is associated with
death and illness. But since the EPA's case for tighter
standards is based on its claim of lower death rates, it
appears to assume a causal relationship.
Some scientists believe that in
these studies PM is only a surrogate for a complex mix of
pollutants, among which other components may contribute
to health damage. Some believe that only some of the
particles cause damage. Or that entirely different
pollutants, present with PM, may be responsible. Or they
doubt that PM readings on a few outdoor monitors
accurately reflect the actual exposures to most people in
their daily lives.(45-51)
But the EPA has concluded, on the
basis of its own analysis, that if PM2.5 is not the whole
cause of the trouble, it is sufficiently deeply
implicated to make tighter controls necessary until
clinical evidence can produce a more complete story.
One specific question is the
relationship of diesel engine emissions to health, and
whether tighter controls on PM will affect the use of
diesel trucks and railroad locomotives. Since different
fuels and different industrial processes can produce
different particles, some industries may object to the
costs of meeting the proposed standards before the active
agents have been more precisely identified. Health and
environmental organizations are likely to reply that the
indicated toll of death and illness is sufficient to
require action now, rather than waiting for more
research.
Why choose 2.5 microns as the
crucial dimension?
The EPA notes that 2.5 microns is a
dimension that has been widely used in the health studies
on which the regulators are relying. It has also been
established that very fine particles penetrate most
deeply into people's lungs. But that raises another
question. How do we know that the research a few years
from now won't point to some other dimension, perhaps 1.0
microns or smaller, as the right one?
In his closure letter on the PM
proposal, the chairman of the scientific advisory
committee, CASAC, wrote that about half of the
committee's panel on PM felt that EPA's staff may have
overstated the case for taking PM2.5 as the best
available surrogate for the agent in PM10 that does harm
to health. In addition, he said, it needs to be
acknowledged that larger particles, perhaps around 4
microns in diameter, "may be responsible for acute
respiratory effects, especially in susceptible groups
such as asthmatics."7
Why propose an annual average of 15
micrograms per cubic meter as the standard? Where did
that figure come from?
In the epidemiological studies, the
EPA reports, the evidence of the short-term health
effects of PM2.5 is clearest above concentrations of 16
micrograms per cubic meter. In the studies on which the
EPA is relying for data on long-term health effects, the
average concentration of PM2.5 was 18 micrograms per
cubic meter. The EPA concludes that 15 micrograms per
cubic meter would represent a "margin of
safety." (129-30)
But the EPA does not suggest that
this margin of safety would mean no health effects on
anyone, or even that the new standard would eliminate all
deaths from PM2.5. (76-80) Here the EPA is struggling
with the threshold issue created by the language of the
Clean Air Act.
The EPA acknowledges that it is an
open question whether a threshold exists for PM. (85-6)
Also, there is uncertainty about the background level,
and the extent to which health effects at low
concentrations may be owed to man-made PM versus PM that
occurs naturally from dust and vegetation. (86) The CASAC
letter comments that some studies suggest health effects
at concentrations of PM that approach background levels.
Since science does not provide a
clear cut-off point at which concentrations of PM2.5 no
longer threaten anyone's health, setting the standards is
a matter of judgment----a policy decision, as the EPA
puts it. Similarly, the definition of a margin of safety
is not the simple no-harm zone that Congress originally
intended. EPA is in the difficult position of defending
its proposed standards as providing safety only for most
people most of the time, since it can't say that these
standards would prevent all harm to everyone all the
time. It cannot even say that there would be no deaths
caused by PM under the proposed standard. (74-80). It
only asserts that the number of deaths would be
substantially reduced.
If there is still a risk of deaths
from PM under the proposed standard, why not tighten it
further to eliminate that risk? Because, EPA explains,
"...such standards might result in regulatory
programs that go beyond those that are needed to
effectively reduce risks to public health." (126)
Neither the EPA nor anyone else knows what effects
concentrations of PM2.5 below 15 micrograms per cubic
meter have on health. Any estimates depend on assumptions
about thresholds and background levels. It's possible
that the difficult and costly struggle to push
concentrations lower would have no pay-off in health
benefits.
Here the EPA is making a judgment
that appears, at least by implication, to take into
account a balance of costs with benefits. But it's a
judgment that puts it on thin ice in legal and political
terms. The Clean Air Act, as the EPA and the courts have
always interpreted it, does not permit the government to
take economic costs into account in setting health
standards. Congress, according to this interpretation,
wanted to provide absolute protection. But absolute
protection is not physically possible, and trying to
approach it can be hugely expensive.
The EPA concedes that respectable
cases can be made for alternate standards that are both
higher and lower than its proposal. A policy giving
greater weight to the uncertainties in the epidemiology
and the uncertainties about actual causation, as well as
to the small amount of actual monitoring data available,
could well lead to a looser proposal for an annual
average up to 20 micrograms per cubic meter (instead of
15) and a maximum daily average up to 65 micrograms per
cubic meter (instead of 50). ) (120-22) On the other hand
a policy giving greater weight to the potential
seriousness of the health effects could lead to a much
tighter proposal, an annual average down to 12 micrograms
per cubic meter and a maximum daily average of 20 to 50
micrograms per cubic meter.(124-5) The EPA has asked for
public comments on these alternatives as well as on its
proposal, which lies between them.
How does EPA define
attainment for PM?
It's important to pay attention
to the way the EPA defines attainment of the standard.
These definitions have as much to do with the tightness
or laxity of standards as the permitted concentrations of
pollutants do.
The EPA divides the country into
attainment (or non-attainment) areas. An area is
typically a city and its suburbs, although the area may
not have exactly the same boundaries as the Census
Bureau's CMSA. Within each area a number of monitors will
be set up to measure PM2.5.
An area will have attained the
annual standard for PM2.5 if the average reading for all
the area's monitors over a three-year period does not
exceed 15 micrograms per cubic meter. (2, 107-112,
158-60) Note that all the monitors in the area are
averaged together-- a crucial provision. It means that a
hot spot in the area will not throw it into violation of
the standard if there are offsetting cool spots
elsewhere. The epidemiological studies on which this
proposal is based generally used broad averages of
concentrations across an area. But if there are large
variations in PM concentrations within an area, it will
make a big difference exactly where the state and local
authorities choose to put the monitors. The EPA asks for
comment on rules for siting the monitors. (112) It also
says that it may insist on subdividing some areas. (110)
The 24-hour standard addresses
the hot spots. (110,116) The method here would be to take
the daily readings from each monitor for a year and, for
each monitor separately, identify the reading at the 98th
percentile. That's the reading that is higher than 98 per
cent of all the readings. (225) For each monitor, the
98th percentile reading for each year would be averaged
for three consecutive years. If the three-year average
for any monitor in an area is over 50 micrograms per
cubic meter, the whole area would be declared out of
attainment and would be required by the EPA to take
action to reduce its PM2.5 concentrations. (2, 113-117,
160)
This is a change from EPA's
present method for the 24-hour PM10 standards. At present
the EPA allows three exceedances over three years. It
means that the fourth-highest reading on each monitor is
the one that counts, and if it's over the standard the
area is out of attainment. The EPA has two reasons, one
stated and the other not, for going to the 98th
percentile rule instead. The stated reason is, again,
stability. PM concentrations can be affected by a lot of
flakey circumstances, above all unusual weather. The EPA
wants to measure in ways that won't subject localities to
being bounced in and out of compliance by conditions
beyond their control. Another reason may be that the
three-exceedance rule is a strong disincentive to taking
large numbers of readings. The percentile rule makes the
number of allowed exceedances proportional to the number
of readings taken and does not penalize localities that
read their monitors frequently, as the EPA wants them to
do. The EPA proposes to apply the new 98th percentile
method to the present 24-hour standard for PM10, as well
as to the new standard for PM2.5.
What are the costs and benefits of
a tighter PM standard?
While the Clean Air Act forbids the
EPA to take economic costs into account in setting health
standards, an executive order requires it to offer an
estimate along with its proposal, and to use that
cost-benefit analysis to guide implementation. In this
case the EPA has produced only what it calls partial
estimates, in 1990 dollars, as follows (177):
Monetized annual benefits of partial
attainment -- $58 to 119 billion
Annual costs of partial attainment -- $6 billion
Partial attainment means that the EPA
cannot identify controls that would be sufficient to
reach complete attainment of the standard. Here the EPA
is comparing the costs of those controls it can identify
with the benefits that it believes they would achieve.
The controls identified in this calculation account for
only a small part of the reductions needed to meet the
new standard---in the case of California, according to
the EPA, only 15 per cent. The EPA offers no guarantee
that the cost-benefit ratio would be the same for more
complete controls.
The benefit numbers are based in part
on a calculation of the value that society puts on the
reduced risk of premature death---in this case, according
to the EPA, it works out to $4.8 million per death
avoided8---plus
the costs of the illnesses and other damage that would
also be avoided. In these figures the total benefits
mainly reflect the value of the lower risk of death,
which again emphasizes the importance of understanding
the epidemiology of PM.
This cost-benefit analysis is worth noting here
chiefly in contrast to the very different estimate for
the new ozone standard, which was obtained through the
same methodology. Here the EPA claims that the
cost-benefit ratio will lie somewhere between roughly
10-to-1 and 20-to-1. The estimate for the ozone standard,
noted below in the section on ozone, claims a
cost-benefit ratio that would be at best one-to-one and
possibly even less favorable. (Ozone proposed rule, 188)
Currently the standard for ozone is an
average concentration over the highest hour each day of
no more than 0.12 parts per million (ppm) of air. An area
is permitted three exceedances in three years---that is,
an average of one day a year on which the reading for the
highest hour at any monitor is over 0.12 ppm. (A
metropolitan area has a number of monitors distributed
across it. The Washington metropolitan area, for example,
currently has 16.) The reading that counts is
consequently the fourth highest in three years. If it is
over 0.12 ppm at any monitor, the whole area---typically,
again, a city and its suburbs---is not in attainment and
the state must take action to reduce ozone levels there.
The EPA now proposes to change the
standard to a permitted level of 0.08 ppm averaged over
eight hours. Instead of counting exceedances, it will
take the third highest eight-hour concentration each year
from each monitor, and average it with the third-highest
from that same monitor for each of the past two years. If
that average is over 0.08 ppm at any monitor, the area
would be out of attainment and must take action. (3, 94,
109)9
How much tighter is the proposed
ozone standard than the current one?
The proposed standard is tighter
than the present one. But it is not the 33 per cent
reduction that some reports have suggested. The 33 per
cent figure comes from a simple comparison of the 0.12
ppm standard with the proposed 0.8 ppm. But you can't
compare the two. The 0.12 ppm standard is for one hour,
while the 0.08 standard is an average for eight hours.
The EPA suggests that the eight-hour equivalent of the
present 0.12 ppm standard would be a concentration of
0.09 ppm, with three allowed exceedances a year.(58, 79)
The correct comparison is between 0.09 ppm with three
exceedances and 0.08 ppm with three exceedances.
Another way to state the comparison
is this: Under the present standard for ozone, 105
counties nationwide are not in attainment. Under the
proposed standard, 228 counties would not be in
attainment. These figures are the EPA's, posted by it on
the Internet.
Unlike the proposed standards for
PM, this one for ozone would set only a maximum daily
concentration, not an annual concentration. The reason,
the EPA says, is that there is insufficient research on
long-term effects to support a standard. (72)
What are ozone's sources?
Most atmospheric ozone is in the
stratosphere, 10 to 50 kilometers above the earth's
surface. There it performs the valuable service of
filtering ultraviolet radiation from the sun and
protecting people from skin cancer. But ozone at ground
level affects people's respiration, and that's the ozone
that the EPA is trying to control.
Ozone has become a matter of rising
frustration and exasperation to environmental regulators,
for it has proved the most difficult of all the common
air pollutants to control. Far more American cities are
out of compliance with the present ozone standard than
with any other pollutant. The sources of ozone are
numerous, and some of it is entirely natural in origin.
Like PM's, its chemistry is highly complex.
Ozone is formed from two classes of
precursor gases, volatile organic compounds (VOCs) and
the oxides of nitrogen (NOx), when they come together on
very warm days in bright sunshine. NOx is produced by
burning fossil fuels, and most of it comes from vehicles
on the highway and from big industrial power plants like
those run by the electric utilities. Some but not much is
produced naturally. VOCs are also produced by burning,
including burning gasoline in automobile engines, but
they can come from paints and solvents, and a wide range
of industrial processes as commonplace as baking bread
and dry cleaning clothes. Very large quantities of VOCs
are produced naturally by vegetation. Because it requires
warm weather and sunshine, ozone is a seasonal phenomenon
and levels vary sharply from day to day with the weather.
What are the health effects of
ozone?
Ozone can cause a wide range of
respiratory symptoms including coughing, throat
irritation, chest pain, shortness of breath and increased
susceptibility to respiratory infection. (22, 25) The
effects on people with unusual sensitivities, like
asthmatics, can be severe and result in hospital
admissions. But most if not all of the acute effects are
temporary and reversible. (33, 77) The EPA cites a
"possibility" that repeated inflammation
associated with ozone could do sufficient damage to lungs
to affect people's quality of life as they grow older. It
concedes that these relationships are "highly
uncertain," (36-7) but makes the judgment that
exposures sufficient to cause inflammation of the lungs
will damage people's health if they persist over long
periods of time. (78)
The EPA does not assert that ozone
kills people. Some studies by others have claimed to find
a relationship between ozone concentrations and death
rates, but these claims are controversial and the EPA
does not accept them. (The issues in this controversy
have to do with statistical methodology.) The EPA notes
these studies but concludes that "the data are
limited." (37) This is one important point on which
the ozone data differ from those on PM.
It's uncertain whether there's a
threshold for ozone's health effects. On present
evidence, the EPA says, the risk to health from ozone
goes down to background---that is, naturally
occurring---levels. (102) Among people exercising, acute
effects have been observed even at 0.08 ppm---the
concentration that EPA proposes as the standard.
That raises the threshold issue in a
particularly sharp form. There is no way to provide the
"adequate margin of safety" that the law
requires.
Why choose 0.08 part per million as
the standard?
The EPA says that it chose 0.08 ppm as
the standard because of the numbers of children likely to
suffer health effects at any higher number, and because
of concerns about the nature of health effects at the
lowest concentrations at which they have been found. (83)
It acknowledges that there are great uncertainties about
health effects at the lower concentrations, and says that
they cannot be quantified, but regards them as an
important factor in making this policy choice. (85)
A difference of opinion arises here
between the EPA and its scientific advisory committee,
CASAC's ozone panel. CASAC observes10 that there is no
sharp distinction or, in its phrase, no "bright
line," among the exposures that would result from
the various standards under discussion: 0.09 ppm, 0.08
ppm or 0.07 ppm. Among the three, the differences in
percentages of children affected would be small. The EPA
replies that while the percentages are small they are
important. Whether you regard these differences as small
or important, the EPA continues, depends on whether you
look at the percentages or at the absolute numbers of
children affected. (80n)
But with its observation that there is no sharp
distinction among the exposures resulting from these
various possible standards, CASAC has made it clear that
there is no scientific basis for a decision.
Consequently, it said, the choice of a standard must be a
policy judgment. In that case, one issue is what criteria
the EPA is using in selecting its own proposal, and
whether the administrator ought not state her criteria
explicitly.11
CASAC's ozone panel was split over that choice, with some
favoring a concentration of 0.08 ppm as a standard, some
favoring 0.09 and one favoring a range of 0.09 to 0.10.
The EPA then goes on to say that a substantial case
could be made for either a looser standard, 0.09 ppm, or
a tighter one, 0.07. If you focus on the uncertainty of
the data on health effects and on the reversibility of
the symptoms most clearly established, you are likely to
choose 0.09 ppm. (88-89) If you focus on the many studies
reporting health effects at 0.08 ppm, and agree that even
if reversible they are harmful, and if you feel that the
most sensitive people are entitled to protection even
though there are few of them, you are likely to choose
0.07 ppm. (90-91) Perhaps the crucial fact is that, as
the EPA points out, there are no studies reporting
observed health effects at concentrations lower than 0.08
ppm. (86) The EPA has proposed to put the standard at the
lowest concentration at which there are substantial
studies showing health effects.
But, acknowledging that this is a policy judgment, the
EPA also asks for public comment on standards set at both
0.09 ppm and 0.07 ppm.
How does EPA define attainment for
ozone?
Because ozone requires hot weather and
bright sunshine, concentrations are highly sensitive to
the weather. The EPA is trying to find statistical
measures of compliance that reflect more clearly the
emissions of the precursor gases, NOx and VOCs, rather
than flipping cities in and out of attainment with the
vagaries of summer weather. The present definition counts
exceedances, allowing three over three years. Instead,
the EPA now proposes to take the third highest reading
from each monitor each year, and average those readings
for each monitor over three years. Like the proposal for
PM, it says, this new statistical definition of
attainment will provide more stability than the
exceedance method. It will be less likely to tip an area
in and out of compliance with the weather. (93, 94, 109)
What are the costs and benefits
of a tighter ozone standard?
While the law does not permit the
EPA to take economic costs into account when setting
health standards, here again the agency is required to
provide an estimate when it makes a proposal.
In this case it provides two
estimates. Neither, unfortunately, is for precisely the
proposal that it has offered. One is for a somewhat
looser standard, 0.08 ppm over 8 hours, with four allowed
exceedances a year. The other is for a standard somewhat
tighter than the proposal, 0.08 ppm over 8 hours with
only one allowed exceedance a year. (188)
These numbers raise many questions,
and it would be unwise to place much weight on the
absolute values. As with the PM cost-benefit estimates,
these are only partial and, in this case, for some cities
the controls in the analysis would provide only 10% to
20% of the reductions that the proposed standard would
require. The striking thing about these estimates is that
the EPA is not claiming that the benefits outweigh the
costs. In the similar estimates for the PM standard, the
EPA claimed that the benefits would outweigh costs by 10
to 1 or more. Here the EPA is saying that the benefits of
the new ozone standard would at best only equal the
costs, and at worst would be zero. Since these estimates
include a valuation of the diminished risk of illness,
they offer a startling evaluation of the efficiency of
the proposed ozone standard.
Costs of compliance, incidentally,
are not easy to estimate. They depend on what strategies
the EPA and the states choose, and on technological
developments over time. Administratively, the simplest
way to reduce air pollution is to tighten the emissions
rules for big industrial sources like electric companies'
generators, or to require refineries to produce cleaner
fuel for cars. But those rules are already pretty tight
and further reductions there would be very expensive.
Restrictions on driving and requirements for more
effective vehicle inspections would be cheaper in
out-of-pocket costs but more expensive in inconvenience
and more likely to generate political resistance. Recent
experience suggests that neither the EPA nor Congress is
prepared to stand up to a confrontation with the public
over cars. Cheapest of all are voluntary and episodic
restraints, asking the public to limit driving, for
example, or not to use their power lawn mowers in certain
weather conditions. But voluntary and episodic restraints
are also the most uncertain and hardest to administer.
What is EPA's secondary
standard for ozone?
Crops and trees appear to be more
sensitive to ozone than human health is. The EPA cites
studies showing that about one third of the country
probably has concentrations of ozone that can result in
losses up to 10 per cent of many crops. In some areas,
particularly in California, the losses may well run
higher than 10 per cent. (154) Going to the proposed
primary standard of 0.08 ppm would help substantially.
But the crop studies indicate that much of the harm comes
not from high daily peaks but from prolonged exposure day
after day to relatively low concentrations. It not clear
that the 0.08 ppm daily standard would adequately address
long-term exposure of plants. (156, 168)
The EPA has decided, at this
point, to straddle the issue. It is proposing two
alternatives. One is to do as it has done with PM, making
the primary standard also the secondary standard. The
other proposal is more complex. It would establish a new
standard based on accumulated exposure for the three
months of maximum ozone concentration. Under this concept
a monitor would be read hourly from 8 am to 8 pm, and all
readings over 0.06 ppm would be added up. For example, if
the readings were 0.08 ppm all day long, the excess over
0.06 ppm would be 0.02 ppm each hour times 12 hours, or
0.24 ppm-hours. The allowed limit for the three-month
season would be 25 ppm-hours. (169-71)
The EPA will decide between these
two possible standards after receiving public comment and
holding hearings, when it makes its final decision on the
primary standard.
The secondary standard illustrates
again the dilemmas confronting the EPA because of the
absolutist nature of the Clean Air Act, as the agency
interprets it. As in setting the primary, or human
health, standard, the EPA believes that the Act forbids
it to take economic costs into account in setting the
secondary standard to protect vegetation and property.
(119-120) This is a controversial interpretation of the
law. But the EPA cites Section 109 of the Act, directing
that the secondary standard specify the level of air
quality needed to "protect the public welfare from any
known or anticipated adverse effects associated with the
presence of such air pollutant in the ambient air."
(119) The wordanyis underlined in the text of the
EPA's proposed decision. The EPA also notes analysis
indicating crop damage at a 7-hour seasonal mean ozone
concentration as low as 0.05 ppm, a lower level than the
standard it is proposing. (131) But that gets close to
the natural background level.
What are ozone's transport
issues?
The wind can carry pollution many
miles, crossing state borders. This is true for both
ozone and PM, but the fight over ozone has been going on
longer and that's where the focus of the transport issue
now lies. As ozone control has become more expensive,
states have become more concerned about imported ozone.
The issue first arose along the Eastern seaboard, where
the prevailing wind in summer is from the southwest, and
cities complained about being responsible for reducing
ozone levels that were owed in part to pollution blowing
up the coast from neighboring jurisdictions. More
recently, the eastern cities have accused the Midwest of
contributing to their ozone troubles. Chicago, Milwaukee
and the Lake Michigan region have similar concerns about
imported pollution.
Two years ago the EPA and state
governments jointly established an organization known as
OTAG---the Ozone Transport Assessment Group. It includes
the 37 states east of Colorado, and its assignment is to
find out how much ozone is attributable to cross-border
winds and make recommendations about remedies. OTAG is
scheduled to report its results in the spring of 1997.
OTAG's work is carried forward
mainly by middle-level bureaucrats and technicians from
the EPA and the pollution control offices of the state
governments, with participation by power companies and
some other industries. Much of it has involved highly
complex modeling of the ways in which ozone is generated
and transported. The models try to track the ways in
which emissions interact with natural VOCs and
meteorology to generate and transport ozone.
While this technical work
proceeds, concerns among the elected politicians have
been rising. The findings of the air quality models have
sharp implications for the economic competition among
states. In the upwind states, some governors and
legislators fear that they will be required to curb
economic development not because their jurisdictions
violate federal clean air standards but because their
neighbors and competitors downwind want help. Some of the
downwind states are counting heavily on help from OTAG to
allow them to get into attainment without expensive and
unpopular pollution controls at home. The underlying
issue here is the distribution throughout the eastern
half of the country of the costs and restrictions
necessary to bring the big urban areas into compliance
with the ozone standard.
Federal legislation to deregulate
the electric power industry is very much a part of the
OTAG issue. East Coast states in particular are concerned
by the possibility that deregulation will mean a shift of
power generation to Ohio Valley jurisdictions where,
because they are in attainment of the ozone standards,
the controls on industrial emissions are less restrictive
and less expensive than on the East Cost. Eastern cities
object that pollution from these plants would be carried
by the wind to them, resulting in even tighter
restrictions on their own industry.
The EPA has said that in March, on
the basis of OTAG's modeling, it will propose state by
state figures for emissions reductions to diminish
interstate transport of ozone and its precursor gases. It
looks as though the EPA has decided not to wait for
OTAG's recommendations on policies to calculate these
figures and to achieve them. EPA has said only that it
will consider OTAG's recommendations if and when they
appear. Because OTAG is working with the present ozone
standard, this controversy does not directly affect the
proposal for a new and tighter standard. But it raises
the stakes for the states.
Implementation: As the partial
figures for the cost-benefit analyses indicate, the EPA
is not yet prepared to show how these proposed standards
can actually be met by all cities and states. In 1995,
anticipating these proposals, EPA set up an advisory
Committee for Ozone, Particulate Matter and Regional Haze
Implementation Programs. That committee is now at work,
and will present its recommendations to the EPA by
December, 1997.
Related legislation: In two major
bills on Congress's agenda this year, air quality
standards are likely to be at issue. Congress is
preparing to pursue further the deregulation of the
electric power industry, which will involve OTAG and all
the clean air questions. Because much ozone comes from
automobile and truck emissions, ozone policy is also a
factor in transportation planning. The federal surface
transportation act expires next September and is
scheduled for reauthorization in this session.
One looming question is whether
Congress will choose to reopen the Clean Air Act itself,
and revisit the threshold assumption. The impact of the
ozone and PM proposals increase the pressure to
reconsider the basic law. But so far that doesn't seem to
be on any agenda.
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