650978
ENVIRONMENTAL
PROTECTION
AGENCY
DALLAS, fCXAI?
OZONE
ITS EFFECTS AND CONTROL
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF AIR QUALITY PLANNING AND STANDARDS
RESEARCH TRIANGLE PARK, N.C.
SEPTEMBER 1978
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CONTENTS
PREFACE 1 '
I INTRODUCTION 2
II DEFINITIONS, EFFECTS, AND STANDARDS 3
A. What are Photochemical Oxidants 3 ,
B. Are Oxidants Harmful? 3 j
C. How Clean Should the Air Be? r
III THE OZONE PROBLEM 7
A. Where Does Ozone Come From? 7
B. Which Sources Contribute Most to Ozone Problems. ... 7
C. How Does the Weather Affect Ozone Pollution g
D. How Serious is the Ozone Problem in the
United States 8
IV OZONE AND THE LAW .' ]Q
A. What is Required? 10
B. Who is Responsible 10
C. What are the Penalties for Noncompliance 1 |
V APPROACHES TO CONTROL 13
A. What Can Be Done? 13
B. What Measures are Appropriate 14
C. How Much Control Will be.Necessary ,.
D. How Should Controls be Applied? -, -.
l b
E. Who Should be Involved •> ,
I o
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PREFACE
Under provisions of the Federal Clean Air Act, the U.S. Environmental
Protection Agency (EPA) has issued National Ambient Air Quality Standards
(NAAQS). These standards specify the maximum amounts of air pollutants to
which the general public may safely be exposed in the interest of health
and welfare. When the NAAQS are found to be violated in any location, the
Clean Air Act requires that steps be taken to bring the air in that location
into compliance with standards by a specified date. Under the Clean Air
Act Amendments of 1977, local governments are empowered and encouraged to
participate fully in air-quality planning for their areas.
Ozone is an air pollutant for which NAAQS have been issued by the EPA.
Frequent and widespread violations have been recorded and extensive remedial
measures will be required. Current efforts to mobilize the nation to solve
the problem have been hampered by the complexity of the issues and controversy
regarding appropriate solutions.
To summarize and clarify the issues, the EPA Office of Air Quality
Planning and Standards has prepared this document under contract. This
summary attempts to provide the local decisionmaker and other interested
persons with an understanding sufficient for informed consideration of
evolving issues and arguments related to oxidant pollution and its control.
Source material listed in the bibliography should be consulted by
persons desiring a treatment of the issues in greater depth.
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I INTRODUCTION
By the Clean Air Act Amendments of 1970, Congress gave EPA the responsibility
for setting air-quality standards. As an outgrowth of studies relating
photochemical oxidants to health effects and damage to plant and materials,
EPA in 1971 issued a standard for photochemical oxidants. This standard
was set at 0.08 parts of oxidant per million parts of air as a one-hour
average not to be exceeded more than once in any given year. Subsequent
reevaluation led EPA in June of 1978 to propose a revised primary standard
to apply only to the most abundant oxidant, ozone, as a one-hour average
concentration of 0.10 ppm not to be exceeded more than an average of once
per year. The proposed secondary, welfare related standard is 0.08 ppm.
The Clean Air Act Amendments of 1977 require that the states make
steps to achieve the standard by 1987 at the latest, and by 1982 where
feasible. Because ozone pollution is substantial, widespread, and harmful
to both health and welfare, extensive measures will be required to eliminate
violations of the standard. The states are required to hold public hearing
to receive comments on the issues before submitting to EPA their plans to
implement appropriate measures. To further participation in the public
hearing process, this document has been prepared to inform local decisionmakers
and the interested public on the issues related to the nature and control
of ozone pollution in the United States.
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II DEFINITIONS, EFFECTS, AND STANDARDS
A. What are Photochemical Qxidants?
The term "oxidants" describes a complex group of compounds found in
the ambient air. The term "photochemical" indicates that much of these
particular oxidants are formed in the air by chemical reactions requiring
the presence of sunlight. Oxidants in the ambient air were first associated
with undesirable effects on human health and welfare three decades ago,
when they were found to be major constituents of southern California
"smog." Since that time, much more has been learned about the photochemical
oxidants and their effects on public health, vegetation, certain ecosystems.
and materials. Ozone—the most abundant oxidant—has been singled out for
special concern from a public health and welfare standpoint.
B. Are Oxidants Harmful?
Numerous studies have been undertaken over the last three decades to
determine how harmful the oxidants are to public health and welfare. The
results are detailed in the EPA publication Air Quality Criteria for Ozone
and Other Photochemical Oxidants.* It should be noted that with synergistic
effects of ozone and other air contaminants, there has not been a sufficient
study to understand this relationship. The following is a summary of the
most significant effects.
*EPA-600/8-78-004 (April 1978) An earlier edition was published in 1971,
at the time the original NAAQS was adopted.
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Public Health
o The mechanical function of the lung is affected by exposure to
ozone for periods on the order of two hours. The effect is
pronounced at concentrations of 0.37 ppm or more; evident but
less pronounced at concentrations from 0.25 to 0.37 ppm, and
in some subjects this effect occurs at concentrations in the
range of 0.15 to 0.25 ppm.
o Asthma attacks occur more often when ambient concentrations of
ozone reach 0.20 ppm for a one-hour period. For some asthmatics
and other sensitive people, there is a likelihood of effect at
concentrations from 0.15 to 0.20 ppm.
o Ozorie exposures in the range of 0.15 to 0.25 ppm for an hour
or so increase the risk of cough, chest discomfort, headache,
and eye irritation.
o There is evidence of impairment of physical performance (athletic
performance) at ozone concentrations as low as 0.15 ppm.
o Vigorous exercise is likely to increase the risk of health
effects from ozone.
o Existing evidence shows no consistent relationship between
ozone exposures and mortality rates.
o No convincing evidence is yet available relating either short-
term or long-term ozone exposure to chronic health effects.
Public Welfare
o Ozone cause visible injury to a variety of plant species.
o Ozone reduce the yields of citrus, cotton, potatoes, soybeans,
wheat, spinach, and other sensitive crops.
o Concentrations of ozone as low as 0.1 ppm for a one-hour
exposure and 0.04 ppm for a four-hour exposure will affect
some vegetation.
o Ozone affect entire ecosystems, as evidence by damage to
mixed conifer forests in California, reduction in the fruit
and seed diet of small mammals, and alterations in species
composition and wildlife habitat.
o Ozone accelerates the deterioration or rubber, textile dyes
and fibres, and certain paints and coatings.
o Both health and welfare effects have severe economic impacts,
which can be measured in terms of monetary losses totalling
hundreds of millions of dollars each year.
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C. How Clean Should the Air Be?
Under the provisions of the Clean Air Act, EPA is charged with the
establishment of standards for the cleanliness (quality) of the ambient
air. "Ambient air" means the outdoor air to which the general public,
structures, plants, and animals are exposed. A standard is a combination
of the amount of pollutant in the air and the length of exposure permitted
as a maximum in the interest of public health and welfare. Standards are
established by the EPA after consideration of effects and application of an
adequate margin of safety. Separate standards are authorized by the Clean
Air Act for protection of public health (primary standards) and for protection
of public welfare (secondary standards).
On 30 April 1971 the EPA published a primary (and secondary) standard
for photochemical oxidants of 0.08 ppm as a one-hour average not to be
exceeded more than once in any given year. The human health effect category
of most concern is aggravation of chronic lung disease and the basic work
documenting the effect is the Schoettlin and Landau asthma study. This was
a key study in determining the level of the existing standard. Based on a
reevaluation of this study, the current criteria document attributes an
increase in asthmatic attacks to a level of 0.25 ppm and not 0.10 ppm as
presumed when the existing standard was promulgated. On 22 June 1978, the
EPA proposed a new one-hour average primary standard of 0.10 ppm for ozone
alone, not to be exceeded more than one time per year on the average.
The secondary standard remains at 0.08 ppm. This proposed standard anticipates
a few excesses in some years, balanced by years with no excesses at all to
give an average of one excess or less per year. Because ozone consititutes
the bulk or oxidants in the air and has been associated with most of the
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health effects previously ascribed to total oxidant, ozone is proposed to
replace total oxidants as the pollutant of concern. Ozone can also be
measured more reliably than the other oxidants.
Because of the specific importance of ozone, the probability of a
revised standard, and the confusion attending the alternate use of the
terms "oxidant" and "ozone," the term "ozone" is used exclusively throughout
the remainder of this document.
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Ill THE OZONE PROBLEM
A. Where Does Ozone Come From?
Unlike many other pollutants, ozone is not introduced directly to the
air by man or nature, but forms in the air by chemical reaction. The
compounds called "precursors," that eventually react to form ozone may be
natural constituents of the atmosphere (as are oxygen and nitrogen), may
be introduced directly as pollutants, or may be formed (as is ozone itself)
by chemical reaction.
High in the upper atmosphere, large amounts of ozone are produced by
sunlight from the oxygen present in the air. Near the ground, ozone is
produced primarily from man-made compounds. While many different compounds
are involved, two basic precursor classes control the ozone production
process: volatile organic compounds (VOC) and oxides of nitrogen (NO ).
J\
VOC enters the air from a variety of human activities, among them
fossil fuel combustion (primarily in auto exhaust), chemical processing,
fuel storage and handling and solvent usage (such as painting or degreasing).
VOC also enter the air from natural sources, such as biological decay and
the vegetative growth process. Oxides of nitrogen, a component in the
photochemical process, is primarily emitted to the atmosphere from the
burning of fossil fuels.
B. Which Sources Contribute Most to Ozone Problems?
Because the air moves readily from one location to another, the air we
breathe at a given place and time will contain ozone from natural as well
as man-made sources. Measurements have shown, however, that ozone concentrations
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in and near large urban centers where man-made sources predominate, are
frequently far greater than concentrations in remote locations unaffected
by human activity. These measurements; coupled with a variety of theoretical
studies, point to human activity—especially that concentrated in large
urban centers—as the source of primary concern. Control of emissions of
ozone precursors associated with human activity will be instrumental in
achieving the ozone standard throughout the United States.
C. How Does the Weather Affect Ozone Pollution?
Ultraviolet radiation from sunlight is required for the photochemical
process. Ozone episodes therefore occur typically on sunny days in spring,
summer, and fall, when the sun is high enough to provide sufficient ultraviolet
radiation. On cloudy days and during the winter months, ozone levels
rarely exceed the federal standard. Sluggish air movement aids in ozone
production by allowing air parcels to remain longer over the source areas
and permitting large amounts of precursors to accumulate and ozone to form.
Temperature inversions (i.e., layers of warm air several hundred meters
above the cooler air nearer the ground) frequently trap the pollutants near
the ground. Warm temperatures have always been associated with ozone
episodes, although the precise role of temperature in ozone production has
not been adequately defined.
D. How Serious is the Ozone Problem in the United States?
Measurements indicate that ozone levels in violation of the standard
occur in virtually every part of the United States. Ozone problems have
been found in rural as well as urban areas. The highest concentrations of
ozone are usually found a few miles downwind from large urban centers,
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which are the principal source areas. The ozone standard is exceeded
frequently in and near these urban centers, as often as 100 or more days
per year in some locations. Concentrations exceeding 0.2 ppm are not
uncommon and concentrations as high as 0.5 ppm have occurred at times
in a few communities. The seriousness of the problem is highlighted by
the fact that violations of the ozone standard have been detected in
virtually every area where measurements have been taken, with the exception
of a few predominantly rural locations.
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IV OZONE AND THE LAW
A. What is Required?
Under the Clean Air Act, states must submit to EPA State Implementation
Plans (SIPs), detailing approaches toward attainment and maintenance of all
air-quality standards. In areas where the ozone standard has not yet been
attained (nonattainment areas), SIPs must be revised to include control
strategies which provides for attainment of standards by December 31, 1982.
In areas where the attainment of standards cannot be demonstrated by implementing
reasonably available control measures the deadline can be extended (up to 5
years) until 1987. Implementation planning for nonattainment areas must be
completed in time for submittal of SIP revisions to EPA by January 1, 1979.
B. Who is Responsible?
While the EPA bears ultimate responsibility for enforcing requirements
of the Clean Air Act, the law provides for maximum participation of state
and local governments in the formulation and implementation of plans and
strategies aimed at achieving the air-quality standard for ozone. Each
state must provide for implementation, maintenance, and enforcement of
primary and secondary air-quality standards in designated areas. Since
many control measures for ozone reduction will strongly affect local jurisdictions,
the Act provides that attainment plans be prepared, where possible, by an
organization of elected officials of local governments in the affected
areas certified by the state for this purpose. Otherwise, a state agency
must prepare the plans. The plan must demonstrate that necessary requirements,
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timetables, and compliance schedules have been adopted through submitta.l of
a legally enforceable document and that the agency or organization identified
in the plan as being responsible for carrying out the plan are committed to
the implementation and enforcement of appropriate plan elements. Attainment
plans must be developed with the continuing cooperative, and comprehensive
transportation planning process mandated by federal law and with the general
air-quality maintenance planning process of the SIP. Attainment planning
requires a coordinated effort and includes local agencies responsible for
transportation and maintenance planning. In carrying out any requirements
of the Act that bear upon the perogatives of local government, the states
must provide a satisfactory process of consultation with general-purpose
local governments and designated organizations of their elected officials.
C. What are the Penalties for Noncompliance?
One of the principal penalties attached to inadequate planning for
nonattainment areas has to do with the construction or modification of
major stationary sources, such as industrial facilities. After June 30,
1979, no such construction or modification that contributes to violations
of NAAQS may take place in a nonattainment area unless an adequate plan for
attainment exists. In addition, inadequate implementation planning in
nonattainment areas precludes the approval of projects and grants for
transportation or air quality authorized under the United States Code,
other than for safety, mass transit, or transportation improvement related
to air-quality improvement or maintenance.
EPA is required to enforce any requirement of a State Implementation
Plan when it is determined that the state has failed to enforce the plan
effectively. Enforcement against a source may take the form of an order to
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comply or a civil action. Persons violating or refusing to comply with any
order of the EPA Administrator or violating requirements of an applicable
implementation plan during a period of federally assumed enforcement can be
subject to a civil penalty of not more than $25,000 per day of violation,
or to permanent or temporary injunction, or both.
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APPROACHES TO CONTROL
A. What Can Be Done?
As discussed earlier, the ozone problem results primarily from chemical
reaction of man-made VOC and NO . It is logical, that the control of ozone
A
precursors generated by human activity, particularly in large urban centers,
is necessary to achieve reductions in ambient ozone levels.
Laboratory studies suggest that control of VOC is an effective approach
to lowering ozone levels in urban areas and their immediate environs.
Significant downtrends in ozone pollution have been recorded in the Los
Angeles Basin and the San Francisco Bay Area, where VOC control programs
have been underway for some time. Studies suggest that control of NO may
A
not be as effective in reducing ozone in urban areas. Because of the
demonstrated effectiveness of VOC control, the current EPA strategy for
reducing of the oxidant problem in urban areas is focused primarily on VOC
control, however programs such as the FMVCP reduce emission of both VOC and
NO . Recent research, has indicated that rural areas may also suffer from
A
ozone pollution and that urban pollutants—ozone as well as its precursors-
can travel considerable distances at relatively high concentrations.
Because the chemical composition of rural air differs from that of urban
areas, NO control may be more effective in controlling rural ozone problems.
A
For this reason, NO control has received greater attention in recent years
A
both for rural areas and for urban areas affecting rural areas through
transport.
On the whole, studies indicate that a more effective program for
reducing urban ozone concentrations should emphasize the control of VOC.
Current strategy favors a vigorous control program for VOC but a cautious
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approach to control of NO beyond that required to attain the ambient air
X
quality standard for nitrogen dioxide. Additional emphasis on NO control
may be required, however, at a later date.
B. What Measures are Appropriate?
State Implementation Plans for areas which have not attained the NAAQS
for ozone, must contain limitations on the amount of ozone precursors that
enter the air and timetables for compliance with such limitations. Other
measures must be contained, as necessary, including (as a minimum) transportation
controls, inspection and maintenance plans for autos for cities greater
than 200,000 population when a state has requested an extension beyond 1982,
and preconstruction review of direct sources of air pollution. State
Implementation Plans may (but are not required to) contain provisions for
land use controls, preconstruction review of indirect* sources of air
pollutants, and other such measures as may be appropriate.
c. How Much Control Will be Necessary?
Maximum ozone levels in and around major urban centers are typically
two to three times the federal ambient standard. Assuming a direct proportion
between VOC and ozone reductions, VOC emissions in these areas will have to
be reduced to one-half to one-third of their current values. This represents
a conservative estimate, since studies have indicated that reductions in
VOC yield less than proportional reductions in ozone concentration. When
*An indirect source is a facility such as a parking lot that tends to
increase air pollution from mobile sources (e.g., cars).
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ozone contribution from natural sources (including vegetation and particularly
upper atmospheric ozone intrusion) is considered, which amounts to approximately
0.04 ppm, an even greater reduction in the contribution from man-made
activities may be required.
Methods for estimating required degree of control have been and are
continuing to be developed. Although no single currently available model
is satisfactory in every respect, evidence from a variety of modeling
techniques indicates a substantial control requirement in many areas.
Research is continuing at EPA to develop improved models to aid in determining
the most effective approaches to ozone control.
D. How Should Controls be Applied?
Most urban and many rural areas now have ozone concentrations greater
than the national standard. Since attainment of the ozone standard will be
costly, there is an obvious and justifiable interest in achieving the most
equitable distribution of the burden and the most efficient application of
the control program. One of the most sensitive issues at present concerns
the division of responsibility for control when a portion of a local ozone
problem results from pollutants transported from nonlocal source areas.
This is especially sensitive in those parts of the United States where
transported pollutants from urban centers in close proximity accumulate
under stagnant weather conditions to form a regional "blanket" of bexkground
ozone.
At present it is difficult to partition responsibility for ozone
control. Considering, however, the degree of control that will be required
to attain the standard, it is reasonable, until more information is at
hand, for everyone to exert maximum effort toward local control of VOC
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emissions. Cooperative efforts in implementation planning among the States
should minimize any gross inequities.
E. Who Should be Involved?
The ozone problem is one that affects every citizen: Very few urban
locations are free of ozone pollution and none are free of sources of
pollution which cause ozone and virtually everyone is subject to the
health and welfare effects. Because ozone is a regionwide problem with a
full spectrum of sources and causes, everyone will bear some portion the
great cost for ozone control. For these reasons, everyone should involve
themselves in the solution of the ozone problem by keeping well informed
and cooperating fully in the planning and implementation phases of the
solution process.
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