United States Office of A
Environmental Protection Plannim afti|;Sl»ridards ' Ju|y 1SN85
Agency . '
Air
«>EPA Regulatory
Analysis of
National Ambient
Air Quality
Standards for
Carbon Monoxide
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EPA-45Q/5-85-007
Regulatory Impact Analysis of the
National Ambient Air Quality Standards for
Carbon Monoxide
U.S. ENVIRONMENTAL PROTECTION AGENCY
Strategies and Air Standards Division
Office of Air Quality Planning and Standards
Research Triangle Park, NC 27711
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ACKNOWLEDGEMENTS AND DISCLAIMER
This final regulatory impact analysis (RIA) was reviewed within the
U.S. Environmental Protection Agency (EPA) and by the Office of Management
and Budget (OMB) and is being published in conjunction with publication
of EPA's final decision on the carbon monoxide national ambient air
quality standards.
This RIA was prepared by the Strategies and Air Standards Division
of the Office of Air Quality Planning and Standards (OAQPS'). The principal
authors include: Thomas McCurdy, Harvey Richmond, and Dave McLamb.
Questions regarding this report should be addressed to Thomas McCurdy
at MD-12, U.S. EPA, Research Triangle Park, N.C. 27711; (919) 541-5655
(FTS 629-5655).
This report has been reviewed by OAQPS, U.S. EPA and approved for
publication. Menion of trade names or commercial products is not intended
to constitute endorsement or recommendation for use.
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TABLE OF CONTENTS
page
I. INTRODUCTION 1
II. STATEMENT OF NEEDS AND CONSEQUENCES 3
A. Legislative Requirements Affecting Development
and Revision of NAAQS 3
B. Nature of the Carbon Monoxide Problem 4
C. Need for Regulatory Action 6
III. ALTERNATIVES EXAMINED 9
A. No Regulation 9
B. Other Regulatory Approaches 10
C. Market-Oriented Alternatives 11
D. Regulatory Alternatives within the Scope of
Present Legislation 13
IV. ASSESSING BENEFITS 15
A. Assessing Benefits of Air Pollution Control 15
B. Estimating Benefits Associated with Alternative
CO NAAQS 19
1. Mechanisms of CO Toxicity 20
2. Nature of CO Health Effects and Reported
Effects Levels 22
3. Sensitive Population Groups 27
4. Sensitive Population Exposure Estimates for
Alternative Standards 30
V. COST ANALYSIS 41
A. Introduction 41
B. RACM Control Costs 43
C. Alternative Control Strategies and Their Costs 48
D. Transaction Costs (Secondary Costs) 51
1. Governmental Regulatory Costs 51
2. Adjustment Costs for Unemployed Resources 53
3. Adverse Effects on Market Structure 54
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Page
VI. EVALUATING BENEFITS AND COSTS 55
A. Introduction , 55
B. Incremental Cost Analysis 55
C. Incremental Cost Analysis 58
D. Benefits Not Valued 61
E. Findings and Conclusions .,,, 62
VII. SUMMARY OF RATIONALE FOR SELECTION OF STANDARDS 63
VIII. STATUTORY AUTHORITY 71
REFERENCES 72
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I. INTRODUCTION
This final Regulatory Impact Analysis (RIA) of the carbon monoxide
(CO) national ambient air quality standards (NAAQS) has been prepared in
accordance with Executive Order 12291, which requires that an RIA be done
for every "major rule." As discussed below, the Environmental Protection
Agency (EPA) has decided to retain the current primary NAAQS for CO and
to revoke the existing secondary NAAQS for CO. Because full compliance
with the current primary standards could result in an annual impact of
$100 million or more on the economy, EPA has determined that this retention
is a major action.
As provided for in sections 108 and 109 of the Clean Air Act as amended,
EPA has reviewed and revised the criteria upon which the existing primary
(to protect public health) and secondary (to protect public welfare)
standards are based to determine if revisions are appropriate. The
existing primary and secondary standards for CO are both currently set at
10 mg/m^ (9 ppm), 8-hour average and 40 mg/m^ (35 ppm), 1-hour average
neither to be exceeded more than once per year. On August 18, 1980, EPA
proposed certain changes in the standards based on the scientific knowledge
reported in the revised criteria document for CO (45 FR 55066). Based on
developments subsequent to proposal and the Agency's review of public
comments, EPA's final decision, announced separately in the Federal
Register, is to retain the existing primary standards at this time
and to revoke the secondary (welfare) NAAQS for CO. Since there are no
welfare effects associated with exposure to CO levels at or near ambient
levels, this RIA focuses on the review of the primary standards.
The Clean Air Act specifically requires that primary and secondary
NAAQS be based on scientific criteria relating to the level that should
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be attained to protect public health and welfare adequately. The courts
have endorsed a reading of the Act that excludes reliance on Lie cost or
feasibility of achieving such standards in determining the level of the
primary standards. Accordingly, EPA has not considered the results of this
RIA in selecting the proposed standards or in its final decision to retain
the primary standards and revoke the existing secondary standards.
This RIA examines the benefits, costs, and other economic impacts of
alternative primary CO standards on both the public and private sectors.
In specifying the alternatives to be analyzed, EPA took account of the
legislative requirements affecting the development and revision of primary
and secondary NAAQS and relied heavily on the document Review of the NAAQS
for Carbon Monoxide: Reassessment of Scientific and Technical Information
(Staff Reassessment, EPA, 1984a). The Staff Reassessment interprets the most
relevant scientific and technical informations reviewed in the revised
Air Quality Criteria for Carbon Monoxide (Criteria Document, EPA, 1979b)
and the Revised Evaluation of Health Effects Associated with Carbon
Monoxide Exposure: An Addendum to the 1979 Air Quality Criteria Document
for Carbon Monoxide (Addendum, EPA, 1984b). The Staff Reassessment, which
has undergone careful review by the Clean Air Scientific Advisory Committee
(an independent advisory group), serves to identify those conclusions and
uncertainties in the available scientific literature that should be considered
in determining the form, and level for both the primary and secondary
standards.
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II. STATEMENT OF NEEDS AND CONSEQUENCES
This chapter of the RIA summarizes the statutory requir-ients affecting
the development and revision of NAAQS and briefly describes the nature of
the ambient carbon monoxide (CO) problem. The need for regulatory action
and the consequences of the regulation in terms of improving the functioning
of the market are also discussed.
A. Legislative Requirements Affecting Development and Revision of NAAQS
Two sections of the Clean Air Act govern the establishment and revision
of national ambient air quality standards (NAAQS). First, as a preliminary
step in developing standards, section 108 (42 U.S.C. § 7408) directs the
Administrator to identify all pollutants which may reasonably be anticipated
to endanger public health or welfare and to issue air quality criteria for
such pollutants. Such air quality criteria are to reflect the latest
scientific information useful in indicating the kind and extent of all
identifiable effects on public health or welfare that may be expected from
the presence of the pollutant in the ambient air.
Section 109(d) of the Act (42 U.S.C. § 7409(d)) requires periodic
review and, if appropriate, revision of existing criteria and standards.
If, in the Administrator's judgment, the Agency's review and revision of
criteria make appropriate the proposal of new or revised standards, such
standards are to be revised and promulgated in accordance with section 109(b).
Alternatively, the Administrator may find that revision of the standard is
not appropriate and conclude the review by retaining the existing standard.
Section 109(b)(l) defines the primary standard as that ambient air quality
standard the attainment and maintenance of which in the judgment of the
Administrator, based on the criteria and allowing adequate margin of safety,
is requisite to protect the public health. The secondary standard, as
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defined in section 109(b)(2), must specify a level of air quality the
attainment and maintenance of which in the judgment of the Ad nnistrator,
based on the criteria, is requisite to protect the public welfare from any known
or anticipated adverse effects associated with the presence of the pollutant
in the ambient air. Welfare effects are defined in section 302(h) (42
U.S.C. § 7602(b)) and include effects on soils, water, crops, vegetation,
man-made materials, animals, weather, visibility, hazards to transportation,
economic values, personal comfort and well-being, and similar factors.
The Act, its legislative history, and recent judicial decisions
(Lead Industries Association. Inc. v. EPA, 1980; American Petroleum Institute
v. EPA, 1981) appear to preclude reliance on the costs and technological
feasibility of attainment in setting primary NAAQS. Such factors can be
considered to a limited degree in the development of state plans to implement
such standards. Under section 110 of the Act, the States are to submit to
EPA for approval State Implementation Plans (SIPs) that provide for the
attainment and maintenance of NAAQS by certain deadlines.
Finally, section 109(d) of the Act directs the Administrator to review
all existing criteria and NAAQS at 5-year intervals. When warranted by
such review, the Administrator is to revise NAAQS.
B. Nature of the Carbon Monoxide Problem
Carbon monoxide is a colorless, odorless gas that is toxic to
mammals because of its strong tendency to combine with hemoglobin to form
carboxyhemoglobin (COHb). Thus, the oxygen-carrying capacity of the blood
is reduced since hemoglobin that has combined with CO in this manner is not
available to transport oxygen. The resultant hypoxemia (deficient oxygenation
of the blood) can have detrimental effects on the cardiovascular, central
nervous, pulmonary, and other body systems. Low-level CO exposures (producing
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group mean COHb levels in the range of 2.9 to 4.5 percent) have ieen shown
to cause aggravation of cardiovascular disease. This aggrava:.ion consists
of decreased time to onset of pain and increased duration of pain in persons
with angina (Anderson et a!., 1973). The Clean Air Scientific Advisory
Committee (CASAC) CO Subcommittee has concluded following a review of the
peer-reviewed scientific literature (not including the Aronow studies) that
the critical effects level for NAAQS-setting purposes is approximately 3
percent COHb (not including a margin of safety) (Lippmann, 1984).
Carbon monoxide is a normal constituent of the plant environment.
Plants can both metabolize and produce CO. This fact may explain the
relatively high levels of CO necessary to damage vegetation. The lowest
level for which significant effects in vegetation has been reported is
100 ppm for 3 to 34 days (EPA, 1979b). The effect observed in this study
was an inhibition of nitrogen fixation in legumes. Since CO concentrations
of this magnitude and duration are not observed in the ambient air, it is
very unlikely that any damage to vegetation will occur from CO air pollution.
No other effects on welfare have been associated with CO exposures at or near
ambient levels. Because no standard appears to be needed to protect the
public welfare from any known or anticipated adverse effects from ambient
CO exposures, EPA is revoking the existing secondary standard. Consequently
this RIA focuses on the primary standards only.
Carbon monoxide air pollution is a problem affecting most urban areas
in the United States. In 1983, man-made sources accounted for about 67.6
million metric tons of CO emissions in the United States. About 71% of
the total CO emissions were from mobile sources and most high CO monitor
readings occurred in areas with heavy traffic concentration. Thus, control
strategies for attaining the CO NAAQS have focused primarily on reducing
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emissions from motor vehicles. Additional information concerning sources
of CO emissions is contained in the Cost and Economic Assessment of Alternative
National Ambient Air Quality Standards for Carbon Monoxide (EPA, 1985).
The primary control strategy for CO emissions has been the implementation
and enforcement of increasingly stringent CO exhaust emission standards
in accordance with the federal motor vehicle control program (FMVCP) pro-
visions of the Clean Air Act Amendments of 1977. For example, the CO
emission standard for non-California, light duty vehicles is 3.4 grams
per mile (gpm) for model years 1981 and beyond. This is approximately a
90% reduction in emissions when compared to light duty vehicles manufactured
prior to 1970. Two other basic control strategies exist for reducing
mobile source emissions of CO including inspection and maintenance (I&M)
programs for light-duty vehicles and transportation control measures
(TCM) which reduce emissions by reducing travel and improving traffic
flow. Additional information describing the FMVCP, I&M, and TCM programs
and their costs and effectiveness are contained in the Cost and Economic
Assessment (EPA, 1985) and in the Control Techniques Document (EPA, 1979c).
The cost and effectiveness of control techniques for stationary sources are
also discussed in these documents.
C. Need for Regulatory Action
In the absence of government regulation, market systems have failed
to deal effectively with air pollution, because airsheds have been
treated as public goods and because most air polluters do not internalize
the full damage caused by their emissions. For an individual firm,
pollution is usually an unusable by-product which can be disposed of at
no cost by venting it to the atmosphere. However, in the atmosphere,
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pollution causes real costs to be incurred by others. This is janerally
referred to as a negative externality in economic theory.
The fact that the producer, or consumer, whose activity results in
air pollution, does not bear the full costs of his action leads to a
divergence between private costs and social costs. This is referred to
as "market failure" because it causes a misallocation of society's
resources, with more resources being devoted to the polluting activity
than would be if the polluter had to bear the full cost.
There are a variety of market and nonmarket mechanisms available to
correct this situation. Some of the principal market mechanisms are
briefly described in Chapter III of this RIA ("Alternatives Examined").
Other than regulation, nonmarket approaches would include negotiations
or litigation under tort law and general common law. In theory, these
latter approaches might result in payments to individuals to compensate
them for the damages they incur.
Such resolutions might not occur, however, in the absence of government
intervention. Two major impediments block the correction of pollution
inefficiencies and inequities by the private market. The first is high
transaction costs when millions of individuals are affected by thousands
of polluters. The transaction costs of compensating individuals adversely
impacted by air pollution include contacting the individuals affected,
apportioning injury to each from each pollution source, and executing the
appropriate damage suits or negotiations. If left to the private market,
each polluter and each affected individual would have to litigate or negotiate
on their own or organize into groups for these purposes. The transaction
costs involved would be so high as probably to exceed the benefits of the
pollution reduction.
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The second factor discouraging private sector resolution c the CO
pollution problem is that pollution abatement tends to be a pjolic good.
That is, after CO pollution has been abated, benefits of the abatement can
be enjoyed by additional people at no additional cost. This constitutes
the classic "free rider" problem. Any particular individual is reluctant
to contribute time or money to reduce CO emissions knowing that his actions
will have little impact on how clean the air he breathes actually is.
In view of the clear legal requirements placed on EPA by the Clean Air
Act, the Agency is planning to retain the primary NAAQS for CO to provide
adequate protection of public health. As this regulatory analysis shows,
there are resource costs associated with this governmental intervention
(see Chapter V, "Cost Analysis"). However, in view of the scientific data
on CO health effects this action is required by the Clean Air Act. In
addition, EPA believes that the cost of this abatement through government
action is less expensive than with any reasonably available private sector
alternatives. Finally, these standards will mitigate the negative externalities
which would otherwise occur due to the failure of the marketplace.
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III. ALTERNATIVES EXAMINED
This chapter briefly presents potential alternatives to one 1980 proposed
revisions of NAAQS for CO. The outline for the chapter is adopted from
Executive Order 12291 which requires that at a minimum the following
alternatives be examined:
a) No regulation
b) Regulations beyond the scope of present legislation
c) Market oriented alternatives
d) Alternative stringency levels and implementation schedules.
Although Executive Order 12291 requires that all alternatives be examined,
only the most promising ones need be analyzed in detail.
A. No Regulation
Abandoning current regulatory requirements for CO would result in a
reliance on private efforts to reduce emissions and on the absorptive
capacity of the atmosphere. The most likely avenues for private efforts
would be either negotiation or litigation under tort and general common
law. Generally speaking there is no incentive for a single company to
enter into negotiations with individuals to reduce CO emissions. For an
individual firm, the cost of reducing emissions would leave that firm at
a competitive disadvantage. Litigation by those damaged could be pursued
either to obtain a reduction in emissions or to obtain payment for damages
incurred (or both). The costs of such litigation would likely be very
high since the individual or classes of individuals bringing suit would
have to prove damages. Moreover, there is little incentive for all those
affected by air pollution to join together in such a suit since everyone
would enjoy the benefits of a successful suit to reduce emissions regardless
of the extent of their participation.
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Because the Clean Air Act requires the Administrator to prescribe
standards for pollutants, such as CO, which have adverse effects on public
health or welfare and because of the impracticality of private efforts, the
option of no regulation has not been analyzed in any further detail.
B. Other Regulatory Approaches
Other regulatory approaches include such options as performance and
technology standards and regional or State air quality standards. Performance
and technology standards are required by the present law in a variety of
forms (e.g., new source performance standards (NSPS) for new and modified
sources, motor vehicle standards, lowest achievable emission rate (LAER)
and reasonably available control technology (RACT) in non-attainment
areas, etc.). They are not based solely on health and welfare criteria
but are designed, in part, to augment control strategies for attainment
of the air quality standards. These standards generally specify allowable
emission rates for specific source categories. The LAER and RACT requirements
are intended to allow growth in non-attainment areas while promoting
progress towards eventual attainment. NSPS and motor vehicle standards
help to reduce the likelihood of future pollution problems by controlling
new sources. EPA is required to consider technology and cost in setting
NSPS and RACT requirements.
Performance and technology based standards serve as useful adjuncts
to ambient standards. However, they cannot serve as substitutes for
ambient standards since even perfect compliance with them may not produce
acceptable air quality levels. Despite the application of such standards,
local meteorology, the interaction of multiple sources, and the level of
the standard itself (the standards are set on the basis of technology and
cost) could produce air quality levels that do not protect public health
and we!fare.
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Regional or State differences in terrain and meteorology us well as
valuations of clean air have been cited as reasons for adopt" ig regional
or State air quality standards. Variations in terrain and meteorology
are considered in setting SIP emission limits to achieve a NAAQS. Such
variations do not generally change the effect of particular levels of
pollution on public health and welfare. Moreover, transport of pollutants
across boundaries would make a system of regional or State air quality
standards difficult to enforce. The Clean Air Act requires national not
regional standards.
In summary, the regulatory alternatives outlined above have not been
analyzed in detail in this RIA because of the Clean Air Act requirements
for setting and revising NAAQS. However, the performance and technology
based standards are helpful in augmenting control strategies for meeting
ambient standards.
C. Market-Oriented Alternatives
There are several market-oriented approaches which can be considered
as means for achieving the NAAQS for CO, but not as a substitute for NAAQS
These approaches include pollution charges, marketable permits, and
subsidies and are briefly discussed below.
Charges. This policy would involve a charge (or tax) being set on
each unit of a pollutant emitted. Firms would then choose the amount of
abatement that minimizes their total cost, including the pollution charge.
Pollution is abated until the marginal cost of abatement is equal to the
pollution charge. The regulatory agency would have to set the level of
the charge or charges in a manner that would result in the desired air
quality. This could be quite difficult and might require continued
adjustments to account for inflation and growth.
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Permits. A permit system would allow a pollution source to purchase
a permit in order to emit a specified amount of a pollutant over a specified
period of time at a specified location. A fixed number of permits could
be issued and auctioned off to the highest bidders. Alternatively, the
permits can be distributed among the sources, who could then trade these
permits as they see fit. If the number of permits and emission allowances are
correctly fixed in advance, then the desired ambient standard would be
achieved. Again, this may be difficult in areas with numerous and diverse
sources.
Subsidies. A subsidy system pays sources for each unit of pollution
that they do not emit. This can take the form of direct payments or tax
credits. Subsidies and charges are similar in that both increase the
opportunity cost of polluting, the former by causing each unit of pollution
to entail forgoing the subsidy which could be received if it were not
emitted. Thus, the subsidy is similar to a charge, except in two
respects:
(a) Administratively, there is the problem of determining the
actual abatement of each source. There must be a determination
of what its pollution would have been in the absence of the
subsidy, and this determination must be adjusted as conditions
change. These determinations are difficult and may depend upon
information from the polluters, who could have the incentive
to strategically misrepresent their intended emissions.
(b) The long-run effects of subsidies may be quite different than
for permits or charges, since the former increase profit
levels or incomes for polluting industries and the latter
decrease them. Thus, in the long-run, subsidies will result
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in firms entering the polluting industry, but permits or
charges will cause firms to leave it. Consequently, a fixed
subsidy rate will yield greater pollution levels than equivalent
permits or charges, although each individual firm will behave
identically under the two systems. Also subsidies would likely
increase dependence on capital intensive solutions.
Summary. Although the Clean Air Act does not contemplate consideration
of these market-oriented alternatives in setting the NAAQS, it does not
prevent States from using such approaches in attaining air quality standards.
Thus, to the extent they are permitted by EPA's regulations for development
of SIPs, the States may consider such market-oriented approaches as
described above in the implementation of the NAAQS.
D. Regulatory Alternatives within the Scope of Present Legislation
The Clean Air Act requires that primary NAAQS be set at levels which
protect the public health, including that of sensitive individuals, with
an adequate margin of safety. The secondary NAAQS must be adequate to
protect public welfare from any known or anticipated adverse effects.
The assessment of the available quantitative and qualitative health
effects data presented in the Criteria Document, Addendum, and Staff
Reassessment, together with recommendations of CASAC and other public
commenters, suggested several alternatives. For a comprehensive discussion
of the scientific data that served as the basis for these alternatives as
well as the rationale for the Administrator's approach to this decision,
the reader is referred to the Criteria Document, the Addendum Staff
Reassessment, and the preamble to the final action.
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Since August 18, 1980, when the revised CO standards were proposed,
a number of alternative 8-hour standards have been considered. The
alternatives being analyzed in this final RIA for the 8-hour primary standard
are shown in Table 1. The 1-hour standard is not being addressed in this
analysis because all areas expected to attain the various 8-hour standard
alternatives are also expected to attain any 1-hour standard under
consideration, and the amount of control needed is higher for 8-hour
standards than for their equivalent 1-hour standards.
Table 1: Alternative Levels of NAAQS for CO
Current Standard
Alternative A
Alternative B
Alternative C
Averaging Time
(hours)
8
8
8
8
Level (ppm)
9
9
12
15
Exceedances Allowed
per year
1 observed
1 expected
1 expected
1 expected
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IV. ASSESSING BENEFITS
A. Assessing Benefits of Air Pollution Control
Air pollution has adverse effects on human health and welfare.
Controlling pollution means reducing these adverse effects. The benefits
of air pollution control are the values (both known and unknown) to society
brought about by reduction in adverse health and welfare effects.
A proper economic benefits analysis is based on appropriate economic
theories and analytical tools to measure all values to all individuals in
dollar or other appropriate units for all expected impacts. The translation
of impacts into dollar values, where possible, allows the summation of
impacts and direct comparison with the costs of pollution control. Estimating
the benefits of air pollution control requires an understanding of how
changes in pollution emissions affect atmospheric conditions and thereby
affect people's health and welfare, and how these effects are valued.
These links are illustrated in Figure 1.
Step 1
Step 2
Step 3
Step 4
Changes in
Emissions
r->
Changes in
Ambient Ai r
Quality
V
•/
1
Changes in
Health and
Welfare
\
/
r
Economic
Valuation
(changes in
well-being)
Figure 1
STEPS IN MEASURING BENEFITS
A complete benefits analysis will examine all effects of changes in
air pollution in Steps 3 and 4 of Figure 1, or in some cases will go straight
from Step 2 to Step 4.
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The Clean Air Act is designed to prevent adverse effects, such as:
1. Health
adverse impacts to human health—acute or chronic effects
that result in increased mortality or morbidity.
2. Welfare
a. adverse impacts to materials—corrosion, soiling and
other damage to building materials, metals, fabrics,
equipment, etc.
b. adverse impacts to vegetation—reduction in productivity
or aesthetic appeal of domestic crops, ornamental plants
and native vegetation.
c. adverse impacts to animals—effects on health and pro-
ductivity of livestock, pets, and wildlife.
d. adverse impacts on climate—changes in temperatures
and/or precipitation.
e. adverse aesthetic impacts—reduced visibility or visual
discoloration of the air and objects viewed through it
and other aesthetic effects such as unpleasant odors.
It is the effects of these impacts on well-being, including the risks of
incurring them and the costs of avoiding or ameliorating them, that determine
the economic valuation of the changes in air quality. This valuation can
be positive or negative depending on whether air quality improves or
deteriorates. For improvements, the valuation is positive, representing
benefits of the pollution reduction, and for deterioration, the valuation
will represent damages of the additional pollution. In order to avoid
confusion, the term costs will be reserved for reference to the costs of
pollution control while damages will refer to the adverse effects of
pollution.
The appropriate benefit measure of pollution control will reflect the
value of the reduction in the need to prevent or ameliorate adverse effects,
the value of reduced risks of incurring adverse effects, and the value of
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reductions in adverse effects actually incurred. These benefits are often
classified into three categories—user, option, and existence values. User
values are the benefits of improved air quality that the individual expects
to enjoy directly. Option values result from uncertainty concerning
future demand for air quality. For example, an individual may wish to know
that he will be able to obtain a particular level of air quality in the
future due to uncertainty about changes in his susceptibility to the adverse
health impacts of air pollution. This may be a particularly important
value when changes in air quality are difficult to reverse. People may
also want to preserve a particular level of air quality across the country
simply to know that it exists, although they never expect to experience it
directly in all locations. This is called existence value.
The approach used in benefits estimation is derived from economic
welfare theory. The benefits of a change in air quality are said to be
equal to the change in well-being, or utility, that results. Such a change
in utility is difficult to quantify, but the standard dollar measure is how
much of other goods and services the individual is willing to give up in
order to obtain or prevent the change. The rational consumer will only be
willing to make the exchange if his utility is enhanced or unchanged. The
individual's maximum willingness to pay (WTP) in order to obtain a desirable
change or prevent an undesirable change is that amount that would keep his
utility constant at either the initial utility level or at the utility
level that would be obtained if the change were to occur. Dollars are used
to represent how much of other things he is giving up.
For market goods, the marginal WTP for an additional unit of a good
service is typically represented by the market price of the good or
service. WTP for different quantities can therefore be taken from the
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market demand curve for the good or service (see Harberger, 197L). For non-
market goods, such as air resources, market prices do not exist and other
methods must be employed to estimate measures of WTP (see Rowe and Chestnut,
1981, for a review). WTP for air pollution control will depend on income,
tastes and preferences, and the prices of alternatives and other goods.
For example, if all the effects of air pollution could be ameliorated with
air conditioning, an individual may not be willing to pay more for air
pollution control than it would cost him for air conditioning. Since the
individual will not be sure whether he will actually incur the potential
effects of air pollution, he may also be willing to pay an additional amount
in order to reduce the risk of suffering undesirable impacts.
A slightly different measure than WTP for the benefits of a change in
air pollution is the willingness to accept compensation (WTA) in return for
incurring an increase in air pollution or foregoing a decrease in air
pollution. The difference between WTA and WTP is whether the point of
reference is the more preferred or less preferred level of air quality.
The WTP measure presumes that an individual does not have a predetermined
right to any particular level of air quality, in which case the point of
reference is the lower level of air quality. The WTA measure presumes that
the appropriate point of reference is the improved level of air quality.
The Clean Air Act states that the public has a right to be protected from
adverse health effects of air pollution. It might be argued, therefore,
that the appropriate benefit measure is the amount the consumer is willing
to accept in compensation for incurring adverse health effects or foregoing
reductions in adverse health effects.
It has been demonstrated theoretically that under typical conditions
WTP and WTA measures would not be expected to differ greatly, but several
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empirical studies concerning air pollution control benefits hav-e found
significant differences between the two, with empirical WTA measures
exceeding WTP measures (see Rowe and Chestnut, 1981).
Changes in air quality will affect many people across many time periods
so that a total benefits measure must be some combination of benefits for
all affected individuals through all relevant time periods. The standard
procedure, which meets the economic efficiency criterion (Harberger, 1971),
is to simply sum WTP or WTA for all individuals and discount them through
time. This ignores interpersonal differences in income and other factors.
Distribution impacts of a change in air quality across different regions,
people, and time periods may be of concern and can be considered separately
(see Rowe and Chestnut, 1981a).
B. Estimating Benefits Associated with Alternative CO NAAQS
To perform a comprehensive benefits analysis for CO that is fully
consistent with economic welfare theory and available scientific evidence
would require a number of complex research tasks that have not yet been
undertaken for CO. Existing scientific knowledge concerning the effects of
CO suggests that only health related impacts are of serious concern at or
near ambient levels. Current medical research, however, is inadequate for
benefits analysis because it does not provide a comprehensive understanding
of exactly how low-level CO exposures adversely affect the body. At present,
experimental evidence only demonstrates that cardiovascular patients
experience early onset of angina when exposed to low levels of CO while
exercising. Considerable additional research would be required to provide
a better assessment of these and other CO-related health effects.
Because of the uncertainties described above involving CO health
effects, EPA's approach to estimating benefits focuses on the number of
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20
people and the number of occurrences of carboxyhemoglobin (COHb) levels of
2.1% or higher that are expected upon attainment of each alternative standard.
Given the current state of knowledge, EPA believes that this measure is the
most appropriate surrogate for estimating benefits associated with alternative
CO standards.
The remainder of this section provides information in summary fashion
on: (1) the mechanism of CO toxicity, (2) the nature of CO health effects
and reported effects levels, (3) the population groups believed to be most
sensitive to CO exposures and estimates of their size, and (4) the number
of sensitive people and occurrences at or above 2.1% COHb upon attainment
of alternative CO standards.
1. Mechanisms of CO Toxicity
The two principal sources of CO that contribute to levels of CO in the
human body are: (1) endogenous CO production from the normal breakdown of
hemoglobin constituents in the body and (2) inhalation of exogenous CO from
ambient exposures.* Endogenous CO production contributes roughly 0.3 to 0.7
percent in the form of carboxyhemoglobin (COHb).
Presently, the most important mechanism of CO toxicity at low-level CO
exposures is thought to be CO hypoxia. This mechanism generally involves
diffusion of exogenous CO through the lungs into the blood with resultant
formation of COHb. Such an increase in COHb levels disrupts normal delivery
of oxygen to the tissues in two ways. First, CO displaces oxygen on the
hemoglobin carrier so that the hemoglobin has a reduced capacity to carry
oxygen through the blood to the tissues. Second, CO makes it more difficult
for the oxygen that is still transported by hemoglobin to be released at the
*The contribution of direct smoking to levels of CO in the body is not being
considered as part of this rulemaking.
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21
tissue. Under these conditions, the tissues must operate at lc, -er than normal
levels of oxygen, a condition known as hypoxia, and this amount of oxygen
may be inadequate to meet the energy needs of the tissues. The effects of CO
on the cardiovascular system, central nervous system, and other systems are
thought to be directly related to this reduction in the ability of the blood
to deliver oxygen to these systems and the resultant oxygen deficiency in
the tissues themselves.
Other possible mechanisms of toxicity have been discussed (Coburn, 1979;
EPA, 1984b). These alternative mechanisms involve binding of CO to such
intracellular hemoproteins as cytochrome oxidase, myoglobin, tryptophan
deoxygenase, and tryptophan catalase. Because the affinity constants for CO
with these proteins are much less than that for hemoglobin, it is unlikely
that they play a major role in CO hypoxia. However, in tissues with a high
oxygen gradient between blood and tissue, it is reasonable to assume that the
interaction of CO with these proteins (particularly with myoglobin in heart
muscle) may play a role in CO toxicity. Myoglobin appears to facilitate the
movement of oxygen through muscle cells and, as a short-term oxygen reservoir
in muscle, it releases oxygen during sudden increased metabolic activity.
The affinity of CO for myoglobin is about 40 times greater than the affinity
of oxygen for myoglobin. The ratio of CO content in heart muscle to CO
content in blood is approximately three. Therefore, given human exposure to
CO, substantial amounts of CO may be stored in heart muscle. In situations
of sudden, severe stress or exertion, the heart muscle's immediate oxygen
supply may be inadequate, even in healthy persons and particuarly in persons
with a history of disease. This alternative mechanism could provide theoretical
support for experimental evidence of myocardial ischemia, such as electro-
cardiographic irregularities and decrements in work capacity discussed later
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22
in this notice. However, it is not known whether binding of CO to myoglobin
could cause health effects observed at COHb levels as low as 4-5 percent.
In summary, disruption of the normal transport of oxygen by formation of
COHb in the blood appears to be the primary mechanism of CO toxicity. In
addition, EPA concludes that regardless of the mechanism of toxicity, COHb
levels provide a meaningful and useful physiological marker of CO toxicity
and for estimating endogenous production of CO and exposure to exogenous
sources of CO (EPA, 1984b).
2. Nature of CO Health Effects and Reported Effects Levels
Table 1 is a summary of key clinical studies reporting human health
effects associated with low-level exposures to CO. This table is based
on evidence discussed in the 1979 Criteria Document (EPA, 1979a) and in the
Addendum (EPA, 1984b) but excludes a series of studies by Dr. Aronow for reasons
given below. The table is included primarily as an aid for the following
discussion and should be used only in conjunction with qualifying statements
regarding the technical merits of each study made in the 1979 Criteria Document,
in the Addendum, in the Staff Reassessment, or in the Federal Register
notice for the final rule.
Cardiovascular Effects. In reviewing the primary standards, a principal
area of concern to the Administrator has been evidence linking aggravation of
angina and other cardiovascular diseases to CO exposures. Angina patients
who have been exposed to low levels of CO while resting have subsequently
exhibited, during exercise, reduced time to onset of angina (Anderson et
al., 1973). In proposing to revise the CO standards, EPA viewed aggravation
of angina, as reported above, to be an adverse health effect (45 FR 55066)
and CASAC concurred with EPA's judgment on this matter.
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TABLE 2.
Lowest Observed
Associated With
23
Effect Levels For Human Health Effects
Low Level Carbon Monoxide Exposure
Effects
Statistically significant decreased
(^3-7%) work time to exhaustion
in exercising young healthy men
Statistically significant decreased
exercise capacity (i.e.,
shortened duration of exercise
before onset of pain) in patients
with angina pectoris
Statistically significant decreased
maximal oxygen consumption and
exercise time during strenuous
exercise in young healthy men
No statistically significant
vigilance decrements after
exposure to CO
Statistically significant impair-
ment of vigilance tasks in
healthy experimental subjects
Statistically significant diminu-
tion of visual perception, manual
dexterity, ability to learn, or
performance in complex sensorimotor
tasks (such as driving)
COHb concen-
tration (percent)a
2.3-4.3
Statistically significant
decreased maximal oxygen
consumption during strenuous
exercise in young healthy men
2.9-4.5
5-5.5
Below
5
5-7.6
5-17
7-20
References
Horvath et al., 1975
Drinkwater et al., 1974
Raven et al., 1974
Anderson et al., 1973
Klein et al., 1980
Stewart et al., 1978
Weiser et al., 1978
Haider et al., 1976
Winneke, 1974
Christensen et al., 1977
Benignus et al., 1977
Putz et al., 1976
Horvath et al., 1971
Groll-Knapp et al., 1972
Fodor and Winneke, 1972
Putz et al., 1976
Bender et al., 1971
Schulte, 1973
O'Donnell et al., 1971
McFarland et al., 1944
McFarland, 1973
Putz et al., 1976
Salvatore, 1974
Wright et al., 1973
Rockwell and Weir, 1975
Rummo and Sarlanis, 1974
Putz et al., 1979
Putz, 1979
Ekblom and Huot, 1972
Pi may et al. 1971
Vogel and Gleser, 1972
«The physiologic norm (i.e., COHb levels resulting from the normal breakdown
of hemoglobin and other heme-containing materials) has been estimated to be
in the range of 0.3 to 0.7 percent (Coburn et al., 1963).
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24
One controlled human exposure study (Anderson et al. 1973) Deported that
experimental subjects with angina exhibited statistically significant reduced
time to onset of exercise-induced angina after exposure to low levels of CO
resulting in mean COHb levels of 2.9 (range 1.3-3.8 percent) and 4.5 percent
(range 2.8-5.4 percent). There remain some concerns about the study findings
due to ambiguities regarding the design and conduct of the study and the
small number of subjects (N=10) examined. However, as discussed in the
Addendum, a revaluation of the Anderson et al. (1973) study addressing
major points of concern, found that the study provides reasonably good
evidence for the hastening of angina occurring in angina patients at COHb
levels of 2.9 to 4.5 percent.
Another cardiovascular effect of concern is the possible detrimental
effect of increased blood flow that occurs as a compensatory response to
CO exposure (Ayres et al., 1969; Ayres et al., 1970; and Ayres et al., 1979).
This effect may be related to coronary damage or cerebrovascular effects at
very high blood flow rates due to the added stress on the cardiovascular
system. However, community epidemiological studies have been inconclusive.
In particular, based on EPA's evaluation of the Goldsmith and Landau (1968),
Kurt et al. (1978), and Kurt et al. (1979) epidemiological studies, the
relationship between CO exposures and effects such as mortality from myocardial
infarction (heart attack), sudden death due to arteriosclerotic heart disease,
and cardiorespiratory complaints remains in question.
Maximum aerobic capacity and exercise capacity are indirect measures
of cardiovascular capacity which have been reported to be reduced in
several carefully conducted studies involving normal healthy adults exposed
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25
to CO. A linear decline in maximum aerobic capacity for health individuals
was reported for COHb levels ranging from 5-20 percent in a series of studies
(Stewart et al., 1978; Weiser et al.t 1978; and Ekblom and Huot, 1972).
Horvath et al. (1975) found decreases in maximum aerobic capacity when COHb
levels were 4.3 percent and that COHb levels of 3.3 and 4.3 percent reduced
work time to exhaustion by 4.9 and 7.0 percent, respectively. The effects of
lower CO exposure levels in healthy individuals have also been investigated
under conditions of short-term, maximum exercise duration. In a series of
studies involving different CO exposure levels, two alternative ambient
temperatures (25°C and 35°C), and two different healthy adult populations
(young and middle-aged), no statistically significant reduction in maximum
aerobic capacity was observed for either group when CO exposures were compared
with the clean air control. However, small (less than or equal to 5 percent)
decreases in absolute exercise time were consistently observed in the non-smoking
subjects whose COHb levels reached 2.3 and 2.5 percent (Drinkwater et al.,
1974; Raven et al., 1974). These effects, while not as serious as aggravation
of angina, are still a matter of concern since they have been found to occur
in healthy individuals and such effects might impair the normal activity of
more sensitive populations. Therefore, these effects have been considered in
judging which CO standards provide an adequate margin of safety.
Central Nervous System Effects. Numerous studies (Putz et al., 1976;
Bender et al., 1971; Schulte, 1973; O'Donnel et al., 1971; McFarland et al.,
1944; McFarland, 1973; Salvatore, 1974; Wright et al., 1973; Rockwell and
Weir, 1975; and Rummo and Sarlanis, 1974) have reported effects on the central
nervous system for CO exposures resulting in COHb levels in the range 5-17
percent. The range of effects reported included impairment of vigilance, visual
perception, manual dexterity, learning ability, and performance of complex
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26
tasks. While one study (Beard and Grandstaff, 1975) has suggested that
vigilance effects may occur at levels as low as 1.8 percent COHb, several
other studies (Haider et al., 1976; Winneke, 1976; Christensen et al., 1977;
Benignus et al., 1977; and Putz et al., 1976) have not found any vigilance
decrements below 5 percent COHb. Measurement methods used to detect effects
may have been too insensitive to detect changes in the latter vigilance
studies. Based on the assessment of the above mentioned studies, the Addendum,
concluded that, at least under some conditions, small decrements in vigilance
occur at 5 percent COHb. A series of studies (Putz et al., 1976; Putz et
al., 1979; and Putz 1979) has also found that 5 percent COHb produced decrements
in compensatory tracking, a hand-eye coordination task. EPA considers hand-eye
coordination effects as well as decrements in vigilance to be important
since these functions are components of more complex tasks, such as driving,
and reduced alertness or visual sensitivity could lead to increased vehicular
accidents.
Fetal Effects. Based on the limited animal toxicology data, the 1979
Criteria Document (EPA, 1979) and the Addendum (EPA, 1984b) suggest that CO
may produce effects on the fetus or newborn. Long-term exposures to CO may
result in a slower elimination of CO by the fetus and may lead to interference
with fetal tissue oxygenation during development. Because the fetus may be
developing at or near critical tissue oxygenation levels, even exposures to
moderate levels of CO may produce deleterious effects on the fetus such as
reduced birth weight and increased newborn mortality (Longo, 1977), although
this remains to be demonstrated alone with pertinent dose-response relationships
(EPA, 1984b). Evidence from smoking mothers is suggestive of similar fetal
and newborn effects due to CO exposures (Peterson, 1981). While the fact
that cigarette smoke contains substances other than CO prevents a direct
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27
quantitative application of the results of these studies in setting the CO
primary standards, these studies do suggest the need for caution in protecting
unborn children from such potentially deleterious effects of CO exposures.
As discussed in the Addendum and Staff Reassessment, research on
sudden infant death syndrome (SIDS) recently has suggested a possible link
between ambient CO levels and increased incidence of SIDS (Hoppenbrowers et
al., 1981). It has been pointed out by Goldstein (1982) that indoor sources
of CO, as well as other pollutants (e.g., nitrogen dioxide, lead), may be
at least as important as ambient CO in causing SIDS and that the relationship
between SIDS and ambient pollution levels may be only coincidental. Because
the number of potentially confounding factors makes finding an association
between CO and SIDS extremely difficult, further confirmation is needed
before any causal relationship can be inferred (EPA, 1984a; EPA, 1984b).
3. Sensitive Population Groups
In EPA's judgment, the available health effects data identify persons
with angina or other types of cardiovascular disease (e.g., history of heart
attack) as the groups at greatest risk from low-level, ambient exposures
to CO. Based on 1980 census data (DOC, 1980) and earlier U.S. National
Health Examination Survey data (DHEW, 1975), this group is estimated to
number approximately 8.7 million individuals or approximately 5.0 percent
of the adult population. As discussed previously, the concern for persons
with cardiovascular disease results from the fact that their condition is
due to an insufficient oxygen supply to cardiac tissue, so that persons
with this condition have an inadequate oxygen reserve capacity and an
impaired ability to compensate for the effects of excess CO.
The Addendum and Staff Reassessment also identify several other groups
as likely to be particularly sensitive to low-level CO exposures based on
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28
EPA's review of the health effects evidence. These groups inc'-.ide: (1)
persons with chronic respiratory disease (e.g., bronchitis, emphysema, and
asthma), (2) elderly individuals, especially those with reduced cardiopulmonary
function, (3) fetuses and young infants, and (4) individuals suffering from
anemia and/or those with abnormal hemoglobin types that affect oxygen carrying
capacity or transport in the blood. In addition, individuals taking certain
medications or drinking alcoholic beverages may be at greater risk for CO-induced
effects based on some limited evidence suggesting interactive effects between
CO and some drugs. Visitors to high altitude locations are also expected to
be more vulnerable to CO health effects due to reduced levels of oxygen in
the air they breathe. Finally, individuals with some combination of the
disease states or conditions listed above (e.g., individuals with angina
visiting a high altitude location) may be particularly sensitive to
low-level CO exposures, although there is no experimental evidence to
confirm this hypothesis.
Table 3 briefly summarizes the rationale for the judgments that these
groups are more likely to be affected by low-level CO exposures and presents
population estimates for each group. For most of the groups listed in Table 2
there is little specific experimental evidence to clearly demonstrate that
they are indeed at increased risk for CO-induced health effects. However,
it is reasonable to expect that individuals with preexisting illnesses or
physiological conditions which limit oxygen absorption into blood or its
transport to body tissues would be more susceptible to the hypoxic (i.e.,
oxygen starvation) effects of CO.
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29
Table 3. Summary of Potentially Sensitive Population Groups3
Group
Coronary Heart
Disease
Rationale
Anderson et al . (1973) suggests
reduced time until onset of
exercise-induced angina in
2.9-4.5% COHb range.
Population
Estimates
8.7 million (in 1980)
Percent of
Population
5.0 (of the adult
population)
Reference
DHEW, 1975
DOC, 1980
Angina Pectoris
7.0 million (in 1980)
4.0 (of the adult
population)
Chronic Obstructive Reduced reserve capacities for
Pulmonary Diseases
Bronchitis
Emphysema
Asthma
dealing with cardiovascular
stresses and already reduced
oxygen supply in blood likely
to hasten onset of health effects
associated with CD-induced
hypoxia.
6.5 million (1970) 3.3
1.5 million (1970) 0.7
6.0 million (1970) 3.0
Anemia
Pernicious and
Deficiency Anemias
Oxygen carrying capacity of blood
is already reduced increasing
likelihood of CD-induced hypoxia
effects at lower CO exposure
levels than for non-anemic
individuals.
3.0 nillion (1973) 1.4
.15 million (1973) 0.07
DHEW, 1973
Fetuses and
Young Infants
Several animal studies (Longo,
1977) report deleterious effects
in offspring (e.g., reduced
birth weight, increased newborn
mortality, and lower behavioral
activity levels).
3.1 million live
births/year (1975)
DHEW, 1978
DHEW, 1977
Peripheral
Vascular Disease
Reduced oxygen-carrying capacity
to limbs likely to hasten onset
of health effects associated with
CO-induced hypoxia.
0.75 million (in 1979) 0.3
DHEW, 1974
Elderly
CO exposures may increase
susceptibility of elderly
individuals to other
cardiovascular stresses due
to already reduced reserve
capacities to maintain
adequate oxygen supply to
body tissues.
24.7 million (in 1979)
> 65 years old
DOC, 1980
subgroups listed are not necessarily sensitive to CO exposure at low levels.
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3. Sensitive Population Exposure Estimates for Alternative
Standards
Objective. An important element in assessing alternative air quality
standards is an assessment of the population exposure to pollutant
concentrations that would result if a given standard were just attained.
Particularly important is an assessment of exposures for the most sensitive
people. EPA's revised exposure analysis report and addendum, "The NAAQS
Exposure Model (NEM) Applied to Carbon Monoxide," (Johnson and Paul, 1983;
Paul and Johnson, 1985) contain estimates of the numbers and percentage of urban
American adults with cardiovascular disease that would be exposed to various
ambient CO levels if alternative 8-hour CO standards were just attained.
In addition, estimates have been made of the percentage of this population
that would exceed selected COHb levels each year. These latter estimates
were derived by applying the Coburn model, which relates patterns of CO
exposure to resultant COHb levels, to the exposure model outputs using a
typical set of physiological parameters for adult men and a separate set of
physiological parameters for adult women.
Both CO exposure estimates and COHb level estimates have been made
for four urban study areas. Both types of estimates have also been made
for the total urban United States population, by extrapolating the four
urban study area estimates.
A brief description of (1) the exposure model used to make the exposure
estimates, (2) the model used to calculate COHb levels from patterns of CO
exposure, and (3) the method of extrapolating these estimates to the whole
urban U.S. sensitive population are presented in the following paragraphs.
Description of Exposure Model. The exposure of an individual to an
air pollutant may be quantitatively expressed by giving the duration of the
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31
exposure and the average concentration of the pollutant in the immediate
vicinity of the individual during the exposure period. The t:,ne periods
of exposure that are of interest for CO are one and eight hours. The
exposure of a population to CO can be described by giving the total
number of one hour exposures to concentrations at or above given values
for a range of concentrations from zero to the highest exposure concentrati on
observed. This is the cumulative distribution of one hour exposures. A
similar distribution can be given for eight hour exposures. For either one
or eight hour exposures the total number of possible exposures in one year
is the product of the population and the total number of hours in one year.
Another measure of exposure is provided by counting the number of
people who experience a given one or eight hour average concentration or
higher at least once during the year. A third measure is the number of
people for whom a given one or eight hour average concentration is the
highest concentration experienced in a one year period. The first two
measures are in the form of cumulative distributions. The third measure is
in the form of a density function.
The exposure model is used to estimate all three exposure distributions
for a given geographical area, either for an existing situation or under
hypothetical conditions in which the area is just in compliance with a
given NAAQS. To estimate exposure when an area is just in compliance with
a given NAAQS, the exposure model proportionally adjusts CO concentrations
observed at each of several selected monitors. Air quality indicators are
derived from the data base of ambient CO concentrations for each hour
throughout a given year. The CO concentrations are proportionally adjusted
so that the adjusted air quality indicator for the monitor with the highest
CO concentrations would be just in compliance with the given NAAQS. Hence,
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32
the concentrations at other monitors are adjusted to levels that are
generally lower.
The exposure model apportions the population of a given area among a
number of cohorts (up to 300 in this application). Twelve age/occupation
categories are each subdivided into several smaller subcategories. A single
cohort represents all individuals of a given subcategory living in the same
type of neighborhood. Each hour of the calendar year a given cohort is
located in a particular neighborhood type and microenvironment and engaged
in some level of exercise. Assignment of individual cohorts to neighborhood
type, microenvironment, and exercise level for each hour is made by using
general data on human activity patterns and transportation data for the
area under study. The manner in which this is done is discussed in detail
elsewhere (Biller et al., 1981; Johnson and Paul, 1983).
An important feature of the exposure model is the way it partitions
concentrations, people, place, and time into discrete groupings or segments.
Microenvironments are an important example of this feature (Duan, 1981).
The infinite number of possible places contained within a geographical
area where people are exposed to air pollutants is represented by a finite
number of types of environments where pollutant concentrations tend to be
relatively homogenous. The microenvironments are defined such that an
individual is always assigned to one of five microenvironment types:
(1) work-school, (2) home and other indoor, (3) inside transportation
vehicle, (4) roadside, and (5) other outdoor. Transformations are made of
base concentrations derived from the fixed monitoring system in order to
estimate concentrations to which people would actually be exposed in the
microenvironments. Values for the multiplicative transformation factors
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33
that would give the best exposure estimates are uncertain. The values used
for these factors were estimated making use of the available literature on
(1) indoor and inside-motor-vehicle air pollution and (2) statistical
analyses of monitoring data (e.g., how ambient values change with height
and distance from a monitor). These estimates are made for conditions
under which the monitoring system is indicating compliance with various
standards. For example, the transformed value of the concentration inside
a vehicle is higher than the base value derived from the monitoring system
because studies have shown that in general this is the case; the transformed
value in the other outdoor (away from roads) microenvironment is lower, as
has also been found in exposure research.
Obviously, the division of the day into a set of twenty-four one-hour
periods is an abstraction which only approximates actual human activity.
For example, if a person is driving a vehicle ten minutes and is indoors
fifty minutes between 2:00 p.m. and 3:00 p.m. the model would have him
indoors the whole hour. Thus, the assumptions made are reasonable modeling
assumptions, not a perfect depiction of reality.
An air monitoring station is associated with each neighborhood type to
estimate exposure concentrations for each neighborhood type-microenvironment
combination. The hourly average CO concentration observed at the monitor
each hour of the year is the concentration associated with the neighborhood
type each hour of the year. This concentration is further transformed to
take into account the microenvironment, additional contributions from indoor
sources, and the particular NAAQS specification. The result is the exposure
concentration that is associated with each neighborhood type-microenvironment
combination each hour of the year.
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34
By accounting for the whereabouts of each cohort each ho-;^ of the year
in terms of the neighborhood type-microenvironment and making appropriate
use of air monitoring data it is possible to follow the hour by hour exposure
of each cohort throughout the year. The model performs the needed
transformations of the concentration for each NAAQS designation and calculates
the three exposure distributions described earlier (total exposures, people
exposed, peak exposures) for one hour exposures and for running eight hour
exposures over the calendar year.
Since the model accounts for the hour by hour exposure of each
cohort, it is possible to compute the COHb level at the end of each hour
for each cohort by applying the Coburn model (Coburn, 1965) to the exposure
model outputs. The Coburn model relates CO exposure to COHb levels, given
appropriate physiological parameters for each cohort of the sensitive
population. Physiological parameters are estimated for each sex and for the
age/occupation category of each cohort on the basis of literature data.
Extrapolation to U.S. Urban Population. The exposure model described
in the preceding paragraphs is directly applicable to a particular urbanized
area. To apply it to the total urban population area of the U.S. would
require that the model be run for each urbanized area in the U.S. and the
exposures in each applicable pollutant concentration range be added together.
Since such a procedure would have required a major effort, an estimate of
the sensitive urban adult population exposures to CO and resulting COHb
levels was made by extrapolation. The extrapolation was based on exposures
estimated by application of the model to four urbanized areas: Chicago,
Los Angeles, Philadelphia, and St. Louis. The extrapolation procedure
was as follows: Each urbanized area within the U.S. with population greater
than 200,000 was associated with one of the above mentioned four urbanized
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35
areas. The association was made on the basis of proximity, average wind
speed, peak CO concentrations, observed climate, and general character of
the area. By summing the populations of each of the areas associated with
a given base area, including the population of the base area, it was possible
to estimate the sensitive urban population associated with each of the four
base areas.
To apply the population exposure estimates associated with each of the
four base areas to the nation, it was first necessary to normalize the CO
exposure and COHb distributions obtained for the sensitive group in each
base area by converting the distributions to a per person basis. These
distributions were each multiplied by their respective associated, sensitive,
U.S.-wide, urban population values and summed over the four cities to obtain
the extrapolated distributions.
Results. Selected results are presented in Tables 4 and 5. Estimates
of the number of sensitive people in the urban U.S. whose COHb levels
would exceed various selected concentrations upon attainment of four alterna-
tive NAAQS are presented in Table 4. The four situations assume that the
alternative standards are just met in each urban area of the U.S. It is
anticipated that air quality in a number of urban areas will be superior
to that required to meet the standards given in the tables due to nation-
wide control programs such as the FMVCP.
Table 4 provides estimates for 1987 of the percentage of the adult
population living in urban areas who would exceed various COHb levels upon
attainment of three alternative 8-hour standards. For example, less than 0.01
percent of the adult population in urban areas is estimated to exceed 2.1
percent COHb due to CO exposures associated with attainment of the current
(deterministic) 9 ppm standard, and approximately 20 percent of the adult
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36
Table 4. Cumulative Percentage of Cardiovascular Adult
Population in Urban Areas Whose COHb Levels Would Exceed Specified
COHb Values Upon Attainment of Alternative 8-Hour Standards3''3*0
9 ppm
I Observed
Exceedance
8-Hour Standards
9 ppm
1 Expected
Exceedance
12 ppm
I Expected
Exceedance
15 ppm
1 Expected
Exceedance
COHb Level
Exceeded (Percent)
3.0
2.9
2.7
2.5
2.3 0.01
2.1 <.01 0.1
.01
.02
0.1
0.8
4.1
8.6
1.1
2.5
5.9
9.7
14
20
Projected cardiovascular disease population in all urbanized areas in the
United States for 1987 is 5,240,000 adults.
DThese exposure estimates are based on air quality distributions which
have been adjusted to just attain the given standards.
GThese exposure estimates are based on best judgments of microenvironment
transformation factors. Projections for one urban area based on lower
and upper estimates of the microenvironment transformation factors are
provided in the Exposure Analysis report (Johnson and Paul, 1983).
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37
Table 5. Estimates of Number of Occurrences Among Cardiovascular
Adults in Urban U.S. of Carboxyhemoglobin Levels Exceeding
Selected Concentrations Upon Attainment of Alternative 8-hour Standards9
8-Hour Standards
COHb Level
Exceeded (Percent)
3.0
2.7
2.5
2.3
2.1
9 ppm 9 ppm
1 Observed 1 Expected
Exceedance Exceedance
-
-
-
570
12,000
12 ppm
1 Expected
Exceedance
570
14,800
76,700
473,000
1,580,000
15 ppm
1 Expected
Exceedance
106,000
810,000
1,880,000
4,100,000
8,580,000
alt is estimated that the total number of occurrences for the sensitive population
in urban areas in 1987 will be 45,900,000,000 (approximately 5,240,000 sensitive
people times 8,760 8-hour periods per year)
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38
population is estimated to exceed 2.1 percent COHb upon attainment of a 15
ppm standard with 1 expected exceedance allowed per year. It should be noted
that the estimates given in Table 4 are based on air quality distributions
which have been adjusted to just attain the given standards.
The urban population of the United States consists of people living in
urbanized areas of the country. Urbanized areas consist of all cities of
50,000 population or more and their contiguous incorporated places.
It is estimated that this population will be 142 million in 1987 (based
on a 1% annual growth rate). It is further estimated that approximately
110 million of these individuals will be adults (over age 18). Approximately
5.8% of the adult male population and approximately 4.2% of the adult
female population have angina or other coronary heart disease (DREW, 1975).
It is estimated that approximately 52% of the adult population will be
female. Consequently, it is estimated that the size of the most sensitive
population residing in urban areas will be approximately 5.2 iTiillion in
1987.
Estimates of the percentage of the urban U.S. sensitive population
whose COHb levels would exceed various selected concentrations are presented
in Table 4. For example, it is estimated that the percentage of the sensitive
population that would experience a COHb concentration exceeding 2.1% at
least once due to exposure to CO if the 9 ppm, 1 observed exceedance standard
were just met throughout the urban United States in 1987 is less than
0.01%.
The estimated number of COHb concentration occurrences in 1987 exceeding
various COHb levels is presented in Table 5. The number of occurrences
differs from the number of people in that if the same person exceeds a
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39
given COHb level N times it counts as N occurrences. One occurrence occurs
every time a person's COHb level exceeds the given concentration at the end
of an hour. For example, if a 9 ppm, 1 expected exceedance standard is
just attained, the number of occurrences where COHb levels exceed 2.1% is
estimated to be 12,000 while the number of people exceeding 2.1% COHb is
approximately 5,200. Thus, the number of occurrences is more than twice
the number of people due to multiple occurrences.
Uncertainty. Several factors make the accuracy of the nationwide
exposure estimates uncertain. They include: (1) the paucity of
information on several of the needed inputs (e.g., some of the microenvironment
multiplicative transformation factors) and (2) the fact that nationwide
estimates were extrapolated from only four urbanized areas.
Ideally, the uncertainty in each significant uncertain factor would
be addressed formally (probabilistically) within the exposure model so
that a formal (probabilistic) representation of the uncertainty in each
exposure estimate would be part of the output of the model. In the future
the NAAQS Exposure Model (NEM) will be developed further into a probabilistic
model (Biller et a!., 1981). Due to limitations of time and resources a
less extensive approach designed to obtain a rough estimate of the degree
of uncertainty has been used in the present study.
In this application of a NEM a limited analysis has been done of the
sensitivity of the exposure estimates to variations in some of the most
uncertain inputs. Lower and upper estimates were made of the quantities
whose uncertainty had the largest impact on the estimates, namely, the
factors used to transform monitored CO concentrations to estimates of CO
concentrations to which people are actually exposed in the various micro-
environments. NEM was applied to one city (Chicago) for one standard
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40
(12 ppm, 1 Ex Ex) using the lower and upper estimates. The results of this
application are presented in Tables 7-40 through Table 7-44 o- the more
detailed report of the CO exposure analysis (Johnson and Paul, 1983). It
is clear from the large disparity between the lower and upper estimates
presented in these tables that the uncertainty about the best values for
these transformation factors alone leads to significant uncertainty about
the accuracy of the exposure estimates.
Two of the physiological parameters which determine COHb levels in
the blood resulting from given patterns of CO exposure are another source
of uncertainty investigated via a limited sensitivity analysis. The
results of a limited variation in the values assigned the Haldane constant
and the low exercise level ventilation rate are presented in Table 7-45
of the exposure report. These variations have a significant effect, but
not as large an effect as the variation in estimated microenvironment factors,
Obviously, sensitivity analysis runs in which microenvironment
transformation factors and physiological parameters were varied together
would result in even more widely divergent estimates. Also, other uncertain
factors and the uncertainty introduced in the nationwide extrapolation have
not been addressed in these limited analyses. In sum, the exposure estimates
are as good as can be made given the state of the art, but their accuracy
is quite uncertain.
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V. COST ANALYSIS
A. Introduction
This chapter emphasizes the direct principal, or real-resource, costs
associated with controlling emission sources of carbon monoxide (CO) air
pollution in order to attain alternative national ambient air quality
standards. These costs were estimated for 3 years—1987, 1990, and 1995.
Only the 1995 results are discussed here. The costs are in constant 1984
dollars unless otherwise noted. Cost estimates are derived from an EPA
report entitled Cost and Economic Assessment of Alternative National Ambient
Air Quality Standards for Carbon Monoxide (Revised) (EPA, 1985).
The above report contains a number of detailed cost and economic
analyses that are not reproduced here. These include an investigation of
the impacts of setting alternative CO standards on specific population
income groups (all income categories), industrial sectors, local governments,
and small businesses. Major findings from these specialized studies are:
1. no particular segment of the population is forced to pay a
disproportionate amount of the total cost of mobile source control.
Therefore, there are no significant adverse income distribution
impacts associated with any of the alternative CO standards.
2. while "distressed cities" are definitely affected by various CO
control programs, the probable overall impact on local government
finances is considered to be negligible. The prime reason for
this conclusion is that most of the direct costs of CO control
programs are borne by motor vehicle owners and users, not by local
governments. Inspection and maintenance programs are self-
supporting, paid by for user fees; transportation control measures
are partly paid for by the federal government under a U.S.
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42
Department of Transportation progran intended to reduce energy
consumption associated with motor vehicle use.
3. small businesses are not affected directly by CO capital and
operating expenditures, because no small business as defined by Small
Business Administration criteria will be required to install air
pollution controls to attain the ambient CO standards investigated.
4. financial capital is generally available for those few large
industrial sources that need to install CO pollution control.
Major shifts in the firms' opportunity cost of capital are not
anticipated. For all but 2 or 3 firms in the country, CO capital
expenditures are less than 5% of projected capital expenditures.
In no case are CO capital expenditures larger than 8% of projected
capital expenditures.
5. for affected industries and plants, controls associated with the
alternative standards are judged to be economically affordable.
No significant product output adjustments are anticipated in
response to product price changes, which should be quite small for
all alternative standards (less than 0.5% in most cases).
The interested reader is referred to EPA (1985) for more information on the
items discussed above.
As discussed in the above reference, the methodology used to estimate
regulatory impacts associated with alternative CO standards is highly
sensitive to the value used to represent air quality in the base year (the
so-called design value). A small change in this value can substantially
alter non-attainment area projections and the amount of control theoretically
needed in a particular location. Similarly, other assumptions such as the
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43
form of the standard (i.e., statistical or discrete) growth rates, and base
year of the emissions inventory can affect predicted attainmen: and cost
projections.
Cost projections also are affected by the nature and timing of the
control strategy program assumed for an area. Numerical criteria were
developed based on the percent of emission reductions needed in an area to
determine what mix of CO strategies were assumed in that area. These
strategies, such as inspection and maintenance programs and transportation
control measures, were applied and costed out to determine national CO
costs. It should be recognized that the devised programs are hypothetical.
Actual control programs are developed by state and local air quality
management agencies in the state implementation planning process. Actual
national costs of CO control programs will be the sum of many individual
state decisions, not the hypothetical program developed for this regulatory
impact analysis.
For purposes of this regulatory analysis, no fuel savings benefit is
claimed for factory installed automobile carbon monoxide control equipment.*
B. RACM Control Costs
CO control equipment and strategies are divided into two major types.
1. reasonably available control measures (RACM).
2. best available control measures (BACM).
Reasonably available control measures and technologies are the principal
mechanisms in state implementation plans which are developed to attain and
maintain a national ambient air quality standard. For this reason, RACM
control costs are the main focus of interest in this Regulatory Impact
*However, fuel economy savings are claimed for some of the control measures
that go beyond automotive hardware. See below.
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Analysis. However, as will be discussed in more detail later, some areas
may require more control, or more stringently enforced control, than RACM
to attain a particular standard.
RACM control strategies include "normally operated" inspection and
maintenance programs for automobiles (I&M), transportation control measures
(TCM) oriented toward increasing mass transit ridership and improving
traffic movement, and point source-oriented technologies. (See EPA, 1979
and its backup material for more information on specific RACM strategies
that were investigated.) Total national annualized costs associated with
these RACM strategies for 1995 are depicted in Table 6. All estimates are
in constant 1984 dollars. The geographic unit of interest for the most
part is a Standard Metropolitan Statistical Area (SMSA) as defined by the
U.S. Census Bureau.
Table 6 also includes an estimate of the number of SMSAs that cannot
attain the alternative standards in 1995 with the use of RACM control strategies.
As can be seen, all SMSAs can attain the 12 and 15 ppm standards in 1995 but
that is not true for the other alternatives.
Automobile and other mobile source emissions controls are required by
Title II of the Clean Air Act (42 U.S.C. 7501, et_ se£.), and are not affected
by alternative ambient air quality standards. (Title II is also called the
federal motor vehicle control program, or FMVCP.) Thus, for any particular
emission standard, FMVCP costs are identical in any single year for the
four ambient CO standards invest!gated--9 ppm, second-high 8-hour average
observed value (9/2; this is also called the one observed exceedance
standard, but to avoid a wordy nomenclature, it is designated as the 9/2
standard); 9 ppm, one expected exceedance of the daily maximum standard
(9/1); 12 ppm, daily maximum one expected exceedance standard (12/1); and
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45
Table 6. Annualized 1995 RACM Control Costs
for Four Alternative CO NAAQSa
(1984 $106)
Control
Item
FMVCP
Additional Mobileb
I&M
TCM
Stationary Sources0
Total RACM Costs
Residual Non-Attaining
Areas
4,742
Alternative NAAQS Standard
(ppm/expected exceedances)
9 ppm
2nd-High
4,430
232
53
27
9/1
4,430
198
27
27
12/1
4,430
48
4
31
15/1
4,430
32
-2
16
4,682
4,513
4,476
Notes:aFor the "primary case;" see EPA 1985. There are no fuel savings (benefits)
assumed for the FMVCP program.
^Additional mobile source controls include fuel savings credits.
cStationary sources controls include fuel savings credits; the modeling
approach used cannot distinguish between "forms" of alternative
standards, which accounts for the same number being used for the two
9 ppm standards.
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15 ppm, one expected exceedance of the daily maximum standard (15/1). This
is shown in Table 6. The FMVCP standard assumed throughout tin's report is
3.4 grams per mile.
FMVCP costs are not directly associated with a CO ambient air quality
standard. Incremental costs associated with changing air standards are those
relating to different levels of I£M, TCM, and stationary source programs
hypothetically needed in areas which require more control to attain a given
NAAQS than can be achieved through FMVCP alone.* Even though the FMVCP cost
is not directly attributable to the CO ambient standards investigated, its
cost is shown in Table 6. All subsequent discussions concerning total costs
to attain the CO ambient standard include that portion of the FMVCP program
associated with CO emission standards.
Control costs associated with industrial stationary sources of CO emissions
are relatively minor. For the 9 ppm standards, both the 2nd-high and one
expected exceedances, these costs are estimated to be $27 million in 1995.
(This estimate includes fuel savings from the use of CO boilers or incinerators
with primary and secondary heat recovery), two heat-producing, readily
available CO control techniques.) For the 12 ppm, 1 exceedance standard,
control costs increase to $31 million, reflecting less fuel savings in those
industries with negative annualized costs of controlling CO.** CO control
*Likewise, costs of new source performance standards (NSPS) should not be
attributed to the CO NAAQS since that program is required by another section
(111) of Title I of the Clean Air Act (42 U.S.C. 7409). The NSPS program
is small for CO. Only two process categories are affected by a CO NSPS:
catalytic cracker and submerged arc furnace. Neither category incurs a
negative cost due to fuel savings associated with the CO NSPS (EPA, 1985).
**0f the seven industrial categories that have plants theoretically needing
CO controls to attain alternative ambient standards, four have negative
annualized costs due to fuel savings potential. The categories are maleic
anhydride, carbon black, steel, and automobile manufacturing. Industrial
categories incurring positive costs include gray iron, primary aluminum,
and incineration. It is estimated that, at most, only 29 plants in the
country may be required to install air pollution controls to meet the
alternative CO NAAQS investigated. See EPA (1985) for more information.
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costs drop for stationary sources in 1995 for the 15/1 standard because
many fewer plants hypothetically have to install controls in the first
place.
The remainder of the costs shown in Table 6 refer to area-specific
mobile source programs designed to reduce CO emissions from in-use vehicles.
Two general types of programs are depicted: inspection and maintenance
(I&M) programs focused on so-called light-duty vehicles (passenger automobiles
and small trucks) and transportation control measures (TCM). In the
theoretical cost analysis, the type and timing of these programs varied
widely throughout the country, depending upon:
1. location of the urbanized area being analyzed. California areas
were treated differently than the rest of the country, because
they have different base-year emission factors and different I&M
effectiveness ratios. The same is true for high altitude areas.
2. status of current I&M programs and status of I&M legislation in
the state containing the urbanized area being studied. These
considerations affected the hypothetical start date used in the
cost analysis.
3. the number of vehicles failing an I&M program. This is called the
"stringency factor."
4. the particular mix of local and area TCM's used, and whether or
not these were sufficient to attain the CO standard without an I&M
program.
Because of these variables, it is difficult to generalize and discuss
what sets of I&M/TCM programs were used in the cost analysis. The interested
reader is referred to the Cost and Economic Analysis (EPA, 1985) and its
backup report (Siddiqee, 1979) for more information.
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C. Alternative Control Strategies and Their Costs
The cost data presented in Table 6 are for a "primary case" scenario
and RACM control strategies. As can be seen, not all areas can attain the
9/2nd-high and 9/1 ExEx alternative NAAQS in that case. It is theoretically
possible to attain all but the 9/2nd-high standard in 1995 by using additional
hypothetical control strategies or by making different analytic assumptions.
Four alternative cases were investigated. They are:
1. 40% I&M Stringency. This case differs from the primary case only
in increasing the stringency factor, or rejection rate of the I&M program
from a previous arbitrary maximum of 30% to a new maximum of 40%. (This
does not mean that all SMSAs used a 40% rejection rate. Only those areas
that could not hypothetically attain with a 30% program and had more than
5% in residual overall emissions reductions left to go, were assigned a 40%
stringent I&M program.) Effectiveness of this technique varied by the length
of time an I&M program was assumed to be operating* and whether an area was
in California, in a high altitude area, or in the rest of the country. The
extra emissions reductions obtained via this increase in rejection rate
varied between 4% and 5%, depending upon the factors noted above (SRI
International, 1979).
2. 100% I&M Effectiveness. This case assumed that I&M would be 100%
as effective in reducing emissions from post-repaired vehicles in cold
weather areas as it is in warm weather areas. The primary case assumed I&M
was 50% effective in areas with a November-January temperature of 20°F or
below, and 100% at said temperature of 70°F or above. (Inbetween temperatures
*I&M programs were assumed to start in 1984, 1985, or 1986 depending upon
the legal status of I&M legislation in a state and local progress toward
implementing such a program, see Siddiqee, et al. (1979).
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were interpolated from a straight-line relationship between the two end
points.) Costs associated with this control strategy are negligible, as it
mostly involves changing operating procedures; a 10% increase in the inspection
fee was assumed to be associated with this strategy. The strategy provided
extra emission reductions between 20% and 50% in the various SMSAs, depending
upon their November-January temperature value.
3. 1 ppm CO Background. The primary case assumes a CO ambient
background concentration of 0 ppm (i.e., no CO present). This assumption
is open to question, and an analysis was undertaken using a 1 ppm CO background.
The net effect of doing this is to increase the amount of emissions reductions
that must be obtained from mobile sources. This, of course, raises costs
and results in more residual non-attainment areas.
4. 1984 Base Year. The base year used in the primary case is 1982.
Since the air quality data come from the 1981-1983 time period, and are
supposed to represent air quality as of January 1, 1984, a case can be made
for using 1984 as the base year. Doing so allows less time for the FMVCP
program to operate, resulting in fewer emission reductions from motor
vehicles. Thus, additional mobile source control measures are needed,
increasing costs and the number of areas that cannot attain in 1995.
Using the four cases results in the range of costs and residual non-
attainment areas depicted in Table 7. Also shown in the Table are the
incremental costs -- and their range -- of going from one alternative NAAQS
to the next less stringent standard. Please remember that the costs and
areas estimates are based entirely upon hypothetical control programs, and
may not represent reality very well.
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Table 7. Range in Armualized 1995 Control
Costs for Four Alternative CO NAAQS
(1984 $106)
Alternative NAAQS Standard
(ppm/expected exceedances)
Case 1. 40% I&M Stringency
Additional Mobile
Stationary Sources
total Variable Costs
Residual Non-Attain. Areas
Case 2, 100% I&M Effectiveness
Additional Mobile
Stationary Sources
Total Variable Costs
Residual Non-Attain. Areas
Case 3. 1 ppm Background
Additional Mobile
Stationary Sources
Total Variable Costs
Residual Non-Attain. Areas
Case 4. 1984 Base Year
Additional Mobile
Stationary Sources
Total Variable Costs
Residual Non-Attain. Areas
9 ppm
2nd-High
311
27
$338
3
261
27
$288
1
297
27
$324
7
338
27
$365
10
9/1
219
27
$246
2
221
27
$248
0
239
27
$266
4
263
27
$290
6
12/1
53
31
$84
0
43
31
$74
0
43
31
$74
0
73
31
$104
0
15/1
33
16
$49
0
33
16
$49
0
28
16
$44
0
42
16
$58
0
Costs (x 106)
Incremental Costs Range for Alternative NAAQS
9/2 to 9/1 9/1 to 12/1 12/1 to 15/1
$40-$75 $174-$192 $30-$46
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D. Transaction Costs (Secondary Costs)
According to guidance on performing regulatory impact analyses, a
complete cost analysis of major governmental actions contains an evaluation
of certain secondary costs associated with that action. These include
governmental regulatory costs, adjustment costs for unemployed resources,
and costs associated with adverse effects on market structure, innovation,
and productivity. Most of these items were not specifically investigated
in the cost and economic assessment (EPA, 1985) underlying this Regulatory
Impact Analysis. Consequently, what follows is a general qualitative
discussion of the secondary costs enumerated above.
1. Governmental Regulatory Costs
Costs incurred by governments related to the CO NAAQS depend upon
the role each governmental agency plays in the federal-state system air
resource management established by the Clean Air Act. As regards a NAAQS,
EPA provides scientific and technical analyses in developing, reviewing,
and setting air standards. It also provides technical support in developing
and maintaining computerized national data systems that store ambient air
quality and emissions data. Finally, EPA provides technical guidance to
the states in operating and reporting ambient monitoring networks, developing
state implementation plans, and undertaking enforcement actions against certain
violators of the state's own rules and regulations.
It is extremely difficult to separate out that part of the total costs
for these functions attributable to carbon monoxide, since it is only one
of seven NAAQS and numerous other pollutants that are more or less handled
simultaneously by EPA in performing the functions noted above. However,
EPA's costs to review the CO NAAQS and promulgate a revised standard can be
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estimated. The items covered include: (1) scientific review of health
literature and development of the CO criteria document, (2) r-view of
existing ambient data to determine potential problem areas, (3) development
of a set of control strategies, which are then costed out, (4) analysis of
the economic impacts associated with these costs, (5) analysis of exposures
to alternative CO standards, (6) development of the regulatory package for
proposal and promulgation, (7) analysis of public comments, and (8) internal
review of the various regulatory documents. EPA's estimated total costs
for CO for these items are:
1. 14 person years of staff time.
2. $1,160,000 of contract funds.
3. $60,000 of computer time.
This comes to a total of approximately $2.5 million (in 1984 dollars). It
is a one-time cost* that occurred over 6 fiscal years. This estimate does
not include any costs of maintaining CO air quality or emissions inventory
data. It also does not include any guidance activities costs. The
problem of costing these activities is difficult as data do not exist to
exactly apportion total costs of these activities to CO. However, they are
estimated to be an order-of-magnitude lower than the cost incurred to review
and set the standard.
States, and, if they so delegate, local governments, actually implement
Clean Air Act provisions directed toward attaining and maintaining NAAQS.
Their major implementing functions include operating air monitors and
reporting ambient air quality data (required under Sections 110 and 317 of
the Act), developing state implementation plans (required under Section
*Since section 109 of the Clean Air Act requies that all NAAQS be reviewed
every five years, it will be a repetitive one-time cost.
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110), and enforcing these plans. For the most part, these are "abor-
intensive activities; hence, they are costly. The Economic Inpact Assessment
of the lead NAAQS (EPA, 1978b) provides data that can be used to roughly
estimate the costs to state and local governments in implementing the
promulgated CO NAAQS. That report suggests that these annual costs would
be on the order of 50 person-years of effort plus $1.4 million in monitoring
equipment and other capital costs. State/local control costs, then, would
be around $6.9 million (in 1984 dollars) annually.
Total annual governmental CO control costs are derived simply by adding
the annualized one-time standard-setting costs with other miscellaneous
federal costs (assumed to be $0.4 million) and adding this sum to the $6.9
million state/local estimate. Total annual costs obtained in this manner
for a five-year review cycle are approximately $7.7 million (in 1984 dollars).
2. Adjustment Costs for Unemployed Resources
Three types of costs occur if a regulatory action results in
unemployment of labor or underuse of other productive resources. These
are: loss of value in the resources required to produce lost output,
resource real location costs (such as moving costs), and unemployment transfer
payments. All three should be identified and costed out in a Regulatory
Impact Analysis.
EPA does not believe any significant unemployment impacts are associated
with the CO NAAQS. While there is no direct data on the point, there is
indirect evidence for the conclusion contained in the economic analysis
done on affected industries theoretically needing to install CO pollution
control to meet alternative CO NAAQS. This analysis indicated that the
economic impacts of doing so were small (EPA, 1985). Capital availability,
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54
product price, and import substitution effects were minor; in -aJdition, no
plant closings were predicted due to the installation of CO controls.
3. Adverse Effects on Market Structure
As discussed earlier, the CO NAAQS has little impact on product
price, capital availability, or import substitution. It also has marginal
impact on increase in corporate debt or the debt/equity ratio (EPA, 1985).
Thus, there will probably be little or no impact on market structure in the
seven industrial categories affected by CO emission control needed to attain
alternative CO NAAQS.
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VI. EVALUATING BENEFITS AND COSTS
A. Introduction
Since it was felt that a credible attempt could not be made to estimate
the benefits of various CO ambient standards within project constraints,
and therefore a quantitative benefit-cost assessment could not be done,
analyses of the incremental costs to reduce potentially adverse exposures
to CO (hereafter referred to as ICAs) were performed instead. Costs
associated with four alternative standards were analyzed along with changes
in the number of sensitive people with COHb levels exceeding 2.1% and 2.5%
and reductions in the total number of such exposures.
While this information does not reveal which standard would be preferred
in an economic sense -- only the cost, and not the benefit, of reducing
adverse exposures to CO has been estimated — it does provide a partial
measure of the relative impacts of the alternative CO standards.
B. Exposure and Cost Analyses
The incremental cost analysis relies on the results of the cost model
discussed in Chapter V and the exposure analysis discussed in Chapter IV.
The cost model uses a constrained least cost algorithm to determine the
approximate order of imposition of control measures to achieve specific
standards. This algorithm is considered reasonable for aggregated nationwide
estimates, but it is not necessarily valid for specific nonattainment
areas. Future control technologies are difficult to predict and, hence,
the associated control costs cannot be estimated with precision. Also,
human behavior patterns may change in ways that alter costs. For example,
changes in the real cost of energy in the 1970's caused significant
changes in the purchasing and driving habits of individuals in the U.S.
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Consequently, predictions based on projected human behavior patterns
should be viewed with caution.
The human exposure estimates are based on the exposure model described
in Chapter IV. The exposure analysis was conducted in detail for four sample
cities. To obtain nationwide estimates, the populations of other cities
were assigned to one of the four cities based on geographic region, climate,
peak CO concentrations, etc. Exposure estimates were extrapolated to the
population assigned to each of the four cities. The sum of these values,
adjusted for population growth and for other urban sites not accounted for
in the city assignment, represent the nationwide estimates in 1987.* There
is considerable uncertainty in these nationwide exposure estimates because
(1) there is limited data available on a number of inputs required for the
exposure analysis and (2) the estimates are extrapolated from only four
cities.
In addition, the results of the cost and exposure analyses used in
the incremental cost analysis are not derived in a consistent manner
because they were originally conducted for different purposes with
different underlying assumptions. These inconsistencies may bias the
results when the analyses are used together.
The first such concern is with the estimated ambient CO concentrations
that are the base case levels from which projected changes are calculated.
Although the estimated concentrations chosen are appropriate for the
purposes and requirements of each individual analysis, they are different.
The estimated concentrations for the cost analysis were derived
from a review of ambient air quality data (EPA's SAROAD data base). Because
*The exposure analysis 1987 results were extrapolated to 1995 by applying
population growth rates.
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the allowable exceedances are expected to be calculated as avenges over
three years, the fourth highest occurrence in the three year aata set for
each urbanized area was selected as the base case ambient CO concentrations
for the one expected exceedances form of the standard. The second-highest
daily maximum 8-hour average in a year was used for the 2nd-high (deterministic)
form of the standard.
The exposure analysis used air quality indicators derived from a
data base of ambient CO concentrations from monitoring stations for each
hour throughout a given year. The year chosen depended upon the complete-
ness of data. The stations were chosen as most representative of the
different types of urban neighborhoods used in the exposure model. To
estimate exposures when an area was just in compliance with a given
alternative NAAQS, the exposure model proportionally adjusted the CO
concentrations observed at each of the selected monitors so that the
adjusted air quality indicator for the monitor with the highest CO concen-
trations would be just in compliance with the given NAAQS. The direction
of bias resulting from the use of these different approaches is unclear.
A second area of concern is the different use of assumptions regarding
attainment of the standards. The exposure analysis assumes that the highest
monitor in each urban area will just attain the standard. The monitor
station with the highest baseline reading is brought into compliance
and the others in the area are adjusted in proportion to the change at the
worst station. The cost analysis, however, is based on projections of
baseline emissions given the nationwide FMVCP. The expected reductions in
tailpipe emissions will result in some areas having ambient CO concentrations
below those required by the standard. When full attainment cannot be reached,
cost estimates will be low relative to the exposure estimates since the
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exposure analysis assumes attainment. Consequently, the ICA results will
be biased downward.
C. Incremental Cost Analysis
The results of the incremental cost analysis (ICA) are presented in
Table 8 for increasing levels of control. Cost and exposure information
from which the ICA results were derived are shown in Table 9. The ICA
was performed for 1995 instead of 1987 because fewer residual non-attainment
areas were obtained and comparisons should be made at full attainment.
However, since full attainment was not obtained in 1995, there are inconsistencies
between the exposure and cost analyses. In those areas that do attain,
increased stringency in the standard will result in reduced exposures to
potentially harmful COHb levels over what would otherwise occur.
Based on its reassessment of scientific evidence discussed previously
in this RIA, EPA concludes that adverse health effects clearly occur, even
in healthy individuals, at COHb levels in the range of 5 to 20 percent.
EPA also remains concerned that adverse health effects may be experienced
by large numbers of sensitive individuals with COHb levels in the range 3.0
to 5.0 percent. On this point, the CASAC similarly concluded after reviewing
the scientific literature (not including the Aronow studies), "that the
critical effects level for NAAQS-setting purposes is approximately 3 percent
COHb (no including a margin of safety)" (Lippmann, 1984). In addition to
concurring with EPA that cardiovascular effects are likely to occur at
approximately 3 percent COHb, the CASAC also indicated that several studies
(Drinkwater et al., 1974; Raven et al., 1974; and Davies and Smith, 1980)
reporting physiological effects in the range 2.3-2.8 percent COHb lend
support to concerns about low level CO exposures and should be considered
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Table 8. Incremental Costs Per Exposure Reduction
1995
Incremental Cost Per Exposure Reduction
Reductions in the Number
Reductions in the Number of Occurrences Among
of Cardiovasular Adults Cardiovascular Adults
Exceeding 2.1% COHb Exceeding 2.1% COHb
(S/Person Reduction) ($/Exposure Reduction)
15/1 to 12/1 47-72 4-6
12/1 to 9/1 372-407 106-116
9/1 to 9/2 7,980-14,500 3,140-5,850
indicated standards are in expected exceedances except for 9/2 which is based
on second high observations.
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61
in determining whether a given standard provides an adequate margin of
safety. As discussed previously, the Administrator has excluded Dr. Aronow's
studies from consideration in his decision on the CO primary standards.
Given the uncertainties regarding the lowest levels of COHb at which adverse
health effects may occur, the results of the ICA, which used a 2.1% COHb
cutpoint, should be viewed with caution.
D. Benefits Not Valued
Although the ambient CO standard focuses upon protecting the sensitive
population from adverse health effects, benefits for other populations also
may result from required pollution reductions. These benefits are not
reflected in the ICA and bias the results in an upward manner. According
to evidence evaluated in the Criteria Document (EPA, 1979b) and Addendum
(EPA, 1984b), the general population may begin to experience central nervous
system effects such as impaired vigilance, visual function, manual dexterity
and ability to learn at COHb levels of 4-5%. This implies an increase in
risks of accidents and reduced productivity or activity. Economic values
on these vigilance and other unquantified effects (impaired fetal development,
health effects for elderly individuals, etc.) are unknown, but they could
add to the total benefits of lowered CO concentrations.
Other unquantified benefits accruing to the general population include
certain option and existence values. The former result from uncertainties
regarding the future demand for cleaner air. An example of such uncertainties
would be not knowing whether an individual becomes part of the sensitive
population. Existence values result from altruistic motivations by individuals
to improve air quality even though they may never directly experience the
change. An example might be an individual's willingness to pay to improve
the air quality in the nation's major cities even though that person never
visits major cities.
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E. Findings and Conclusions
The chapter focused on estimation of the incremental costs associated
with alternative CO NAAQS. The degree of uncertainty in making such
estimates was identified by indicating limitations in the methodologies
employed. Despite this uncertainty, deterministic estimates of incremental
costs were developed for illustrative purposes.
ICA, in general, embodies the same methodology as cost effectiveness
analysis (CEA). The usefulness of such tools can allow one to identify the
least cost way to achieve a given goal. In addition, the methods can
eliminate inefficient ways of achieving given goals. The techniques used
above can in no way help identify the optimal goal in an economic efficiency
sense. Hence, the ICA can only be used to identify the opportunity costs
of implementing more stringent standards and cannot identify the socially
desired CO NAAQS from an economic point of view.
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VII. SUMMARY OF THE RATIONALE FOR SELECTING THE FINAL CARBON MCrlOXIDE STANDARDS
This chapter summarizes the Agency's rationale for selection of the
final CO ambient standards. A more complete discussion of the rationale
is contained in the Federal Register preamble for the final rule.
The Staff Reassessment (EPA, 1984a) and 1984 CASAC findings and
recommendations (Lippmann, 1984) set forth a framework for considering
whether revision of the primary CO standards is appropriate at this time.
The discussion that follows relies heavily on that framework and on
applicable supporting material in the Criteria Document (EPA, 1979b),
Addendum (EPA, 1984b), Staff Paper (EPA, 1979a), and earlier CASAC closure
letters (Hovey, 1979; Friedlander, 1982).
Based on its assessment of scientific evidence discussed in the
Criteria Document and Addendum, EPA concludes that adverse health effects
clearly occur, even in healthy individuals, at COHb levels in the range
of 5 to 20 percent. EPA also remains concerned that adverse health
effects may be experienced by large numbers of sensitive individuals with
COHb levels in the range 3.0 to 5.0 percent. On this point, the CASAC
similarly concluded after reviewing the scientific literature (not including
the Aronow studies), "that the critical effects level for NAAQS-setting
purposes is approximately 3 percent COHb (not including a margin of
safety)" (Lippmann, 1984).
In addition to concurring with EPA that cardiovascular effects are
likely to occur at approximately 3 percent COHb (Anderson et al., 1973), the
CASAC also indicated that several studies (Drinkwater et al., 1974; Raven
et al., 1974; and Davies and Smith, 1980) reporting physiological effects in
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the range 2.3-2.8 percent COHb lend support to concerns about 1 :-,v level CO
exposures and should be considered in determining whether a :-yen standard
provides an adequate margin of safety. The Administrator has excluded
Dr. Aronow's studies from consideration in his decision on the CO primary
standards.
Based on the exposure analysis results summarized previously in
Chapter IV (Tables 4 and 5), 8-hour single exceedance CO standards in the
range 9 to 12 ppm are estimated to keep more than 99 percent of the
non-smoking cardiovascular population below 3.0 percent COHb. Different
standards within this range would, of course, provide different levels of
protection. For example, the current 9 ppm, 8-hour average standard is
estimated to keep more than 99.9 percent of the adult cardiovascular
population below 2.1 percent COHb. A 12 ppm, 8-hour standard is estimated
to keep more than 99 percent of the population below 2.5 percent COHb.
The 2.5 percent COHb level is in the range where physiological effects of
concern to EPA and CASAC have been reported.
In considering whether revision of the existing primary CO standards is
appropriate at this time, the Administrator has considered uncertainties
regarding the lowest levels of COHb at which adverse health effects may
occur, as well as uncertainties about the levels of COHb likely to result
from CO exposure at the levels associated with attainment of alternative
standards. More specifically, the Administrator considered the following
factors and sources of uncertainty, discussed in the Staff Reassessment (EPA,
1984a), in his decision:
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1. Human susceptibility to health effects and the levels a; which
these effects occur vary considerably among individuals, and £?A cannot
be certain that experimental evidence has accounted for the full range of
susceptibility. In addition, for ethical reasons, clinical investigators
have generally excluded from their studies individuals who may be especially
sensitive to CO exposure, such as those with a history of myocardial infarction
or multiple disease states (e.g., both angina and anemia). Another factor is
that, once the Aronow et al. studies are excluded there are no human exposure
studies investigating effects on individuals with angina at COHb levels below
the 2.9 percent level reported by Anderson et al. (1973).
2. There is some animal study evidence indicating that there may
be detrimental effects on fetal development (e.g., reduced birth weight,
increased newborn mortality, and behavioral effects) associated with CO
exposure. Similar types of effects have also been found in studies examining
effects of maternal smoking on human fetuses. However, it is not possible
at this time to sort out the confounding influence of other components of
tobacco smoke in causing the effects observed in the human studies. While
human exposure-response relationships for fetal effects remain to be
determined, these findings denote a need for caution in evaluating the
margin of safety provided by alternative CO standards.
3. Other groups that may be affected by ambient CO exposures but for
which there is little or no experimental evidence include: anemic individuals
(over 3 million individuals), persons with chronic respiratory diseases
(about 14 million individuals), elderly individuals (over 24.7 million
individuals over 65 years old), visitors to high altitude locations, and
individuals on certain medications. The levels of COHb that might produce
adverse effects for each of these groups is uncertain. However, elevated
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COHb levels in even a small percentage of this very large potentially
sensitive population would translate to a significant number of individuals.
The large size of the potentially sensitive population, then, argues for
standards providing a greater margin of safety.
4. There are several uncertainties regarding the uptake of CO, including
those related to the accuracy of the Coburn equation, in assessing variations
in the population due to differing physiological parameters and exposure to
varying air quality patterns.
5. Several factors contribute to uncertainties about the exposure
estimates of the expected number of individuals achieving various COHb
levels upon attainment of alternative standards. These factors include:
the paucity of information on several of the needed inputs, the fact that
nationwide estimates were extrapolated from only four urbanized areas, and
the use of two representative sets (one for men and one for women) of physio-
logical parameters (e.g., blood volume) rather than distributions of
physiological parameters in applying the Coburn model to derive COHb estimates
in the exposure analysis. As indicated in the Staff Reassessment (pp. 18-21),
some individuals with physiological parameters that maximize uptake of COHb,
if exposed to certain patterns of air quality attaining a 12 ppm, 8-hour
standard, would likely exceed 3.0 percent COHb. Consequently, the Agency
is concerned that a 12 ppm, 8-hour standard may not provide an adequate
margin of safety. EPA is continuing its CO exposure research efforts,
which should lead to future improvements in its exposure analysis and a
better capability to assess the accuracy of the exposure estimates (Johnson,
1984; Hartwell et al., 1984).
6. There is uncertainty regarding adverse health effects that may
result from very short duration, high-level CO exposures (the bolus effect).
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As discussed in the proposal notice (45 FR 55077), existing air quality
data indicate that attainment of a 9 ppm, 8-hour averaging time standard
should limit the magnitude of short-term peak concentrations.
7. There is some concern about possible interactions between CO and
other pollutants, although there is little experimental evidence to document
such interactions at this time.
8. Given the unsettled nature of the scientific information bearing on
the level of the standard, EPA believes that there is much to be said for a
policy that would maintain the status quo until the data become more
adequate. That is particularly so given the absence of the information
indicating with some assurance that the present standard is set at an
incorrect level. For the reasons stated in the preamble, the available
information falls short of supporting such a finding.
While the CASAC concurred that the ranges of 9 to 12 ppm for the 8-hour
and 25 to 35 ppm for the 1-hour primary standards recommended in the Staff
Reassessment are scientifically defensible, they recommended that the
Administrator consider choosing standards that maintain approximately the
same level of protection as that afforded by the current standards (Lippman,
1984). In making its recommendation the CASAC cited the uncertainties associated
with the scientific data base, margin of safety concerns, and its belief
"... that where the scientific data, as in this case are subject to large
uncertainties, it is desirable for the Administrator to consider a greater
margin of safety than the numerical values of COHb generated by the Coburn
equation might otherwise suggest" (Lippmann 1984).
Several ongoing human health effect studies are being conducted by EPA
and other groups to investigate the effect of CO on aggravation of angina.
Subjects in these studies are being exposed to CO levels that result in
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68
blood COHb levels in the range 2.0 to 4.0 percent. One study is being
conducted by EPA, several are being conducted at the request of EPA by
the Health Effects Institute (HEI), and another study is being sponsored
by the California Air Resources Board (CARB). The Health Effects Institute
is an independent organization which sponsors research on automotive pollutants
and is jointly funded by EPA and automobile manufacturers. The peer-reviewed
results of the these studies are expected over the next 2 to 3 years. EPA
will be initiating development of a new criteria document for CO in Fiscal
Year 1986. Thus, the Agency should be in a good position to expeditiously
assess the results from the above health studies, as well as other scientific
evidence published since completion of the Addendum.
Given the uncertainty in the current data base and the fact that new
studies are in progress, the Administrator considered deferring a final
decision on the CO standards until these new studies have been completed.
While this might allow the Administrator to base the decision on better
information, the Clean Air Act appears to require periodic decisions on
NAAQS notwithstanding any uncertainty in the data base. Deferring this
decision would imply that the Agency has inadequate evidence to select an
appropriate course of action at this time. However, both EPA and the CASAC
have concluded that, even without the Aronow studies, a sufficient scientific
data base exists upon which to base a decision. Given these findings, and
the concern that a deferral of the decision could be perceived as a signal
to relax or delay ongoing control programs, the Administrator has concluded
that final action now on the CO standards is warranted and justified.
In reaching a final decision, the Administrator has focused primarily
on the level of protection the CO standards should provide. As previously
noted, after reassessing the available scientific data and EPA staff
recommendations, the CASAC has recommended that the CO standards provide
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69
protection approximately equal to the current standards. Based on EPA's
assessment of the scientific data, the Administrator concurs w:ch this
recommendation. Retention of the current standards would, of course, satisfy
this objective.
As discussed above, the standards proposed in August 1980 would also
provide approximately the same level of protection as that afforded by the
current standards. In addition, these standards would provide some technical
changes that the Agency believes would be advantageous. However, the
proposed changes would require some modification in the way attainment of
the standards is determined. Given the uncertainties in the existing data
base and the possibility that the results of the new studies in progress might
warrant further revisions within a few years, the Administrator has concluded
that it would not be prudent to promulgate the proposed revisions at this
time, particularly when they would alter the manner in which attainment is
determined.
In short, the Administrator has concluded that it would not be prudent
to defer a decision on the CO standards pending the results of the new research
mentioned above, that the standards should provide approximately the same
level of protection as that afforded by the current standards, and that
disruption of ongoing control programs should be minimized. Given these
considerations, the Administrator has concluded that the best course of
action is not to revise the CO primary standards at this time. Together
with the Administrator's decision to rescind the secondary standards
(discussed below), this decision completes the current review of the NAAQS
for CO under section 109(d). The ongoing studies conducted by the Agency, by
the HEI, and by the CARB (all discussed above) will, of course, be considered
in the next 5-year review of the CO criteria and standards. Upon completion
of this series of studies, the Agency plans to review the results with the
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CASAC and assess the need for any revisions in the primary stan-u^ds. If
revisions in the standards seem appropriate, the Agency will act expeditiously
to revise the standards.
WELFARE EFFECTS AND THE SECONDARY STANDARDS
Carbon monoxide is a normal constituent of the plant environment.
Plants can both metabolize and produce CO. This may explain the fact that
relatively high levels of CO are necessary before damage occurs to vegetation.
The lowest level for which significant effects on vegetation have been reported
is 100 ppm for 3 to 35 days. The effect observed in this study was an inhibition
of nitrogen fixation in legumes. Since CO concentrations of this magnitude
are rarely if ever observed in the ambient air, it is very unlikely that any
damage to vegetation will occur from CO air pollution. No other effects on
welfare have been associated with CO exposures at or near ambient levels.
Because no standards appear to be requisite to protect the public welfare
from any known or anticipated adverse effects from ambient CO exposures, EPA
is rescinding the existing secondary standards.
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VIII. STATUTORY AUTHORITY
The statutory authority for the retention of the CO pri.iary NAAQS
and revocation of the CO secondary NAAQS is contained in the Clean Air
Act. Two sections of the Act govern the establishment and revision of
NAAQS. Section 108 (42 U.S.C. 7408) requires EPA to document the most
recent scientific information (criteria) on the health and welfare effects
of certain air pollutants. Section 109 provides authority for reviewing
the criteria and, as appropriate, for establishing and revising primary
(health based) and secondary (welfare based) NAAQS. A more complete
discussion of the legal authority for this final regulation is contained
in the Federal Register preamble and in Chapter II of this RIA.
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Haider, M., E. Groll-Knapp, H. Hoeller, M. Neuberger, and H. S:idl (1976).
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing/
1 REPORT NO.
EPA-450/5-85-007
2.
4. TITLE AND SUBTITLE
Regulatory Impact Analysis of the National Ambient
Air Quality Standards for Carbon Monoxide
6. PERFORMING ORGANIZATION CODE
3. RECIPIE'; "3 ACCESSION NO.
5. REPO" ' OATS
July 1985
7. AUTHOR(S)
Staff
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
Ambient Standards Branch and Economic Analysis Branch
Strategies anH Air Standards Division
Office of Air Quality Planning and Standards
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Office of Air Quality Planning and Standards
Office of Air and Radiation
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report examines the cost, changes in exposures seen by the public, and
economic impacts associated with setting alternative carbon monoxide NAAQS. Four
alternative 8-hour NAAQS were analyzed: 9 ppm, one observed exceedance, and 9,
12, and 15 ppm one expected exceedance of daily maxima. Three time periods of
analyses are used: 1987, 1990, and 1995.
Also discussed is the health evidence supporting the carbon monoxide (CO)
standard and the reduction in exposures associated with different CO standards.
The report is intended to fulfill the requirements of E.O. 12291, which
requires that a regulatory analysis be undertaken for every rule resulting in an
annual impact of $100 million or more.
17.
KEY WORDS AND DOCUMENT ANALYSIS
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Air Pollution
Carbon Monoxide
Air Quality Standards
Regulatory Impacts
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83
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