Experimental Methods for Assessing Environmental Benefits Volume III Estimating Benefits of Reducing Community Low-level Ozone Exposure: a Feasibility Study


Volume III

Estimating Benefits of Reducing
Community Low-Level Ozone Exposure:
A Feasibility Study

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EXPERIMENTAL METHODS FOR ASSESSING ENVIRONMENTAL BENEFITS

Volume 111

Estimating Benefits of Reducing Community
Low-Level Ozone Exposure; A Feasibility Study

bv

Shelby Gerking
Anne Coulson

William Schulze
Donald Tashkin
Donald Anderson
Mark Dickie
David Brnokshire

USEPA Contract #CR-8i1077-01-0

Project Officer

Dx. Alan Carl in
Office of Policy Analysis
Office of Policy, Planning and Evaluation
U.S. Environmental Protection Agency
Washington, D. C. 20460

OFFICE OF POLICY ANALYSIS
OFFICE OF POLICY, PLANNING AND EVALUATION
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460

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ESTIMATING BENEFITS OF REDUCING COMMUNITY
LOW—LEVEL OZONE EXPOSURE: A FEASIBILITY STUDY



Shelby Gerking*
Anne Coulson**
V. i J liam Schul 7.e***
Donald Tashkint
Donald Anderson+t

Mark Dickie*
David Brookshire*

Department of Economics, University of Wyoming, Laramie

*

SchonJ of Public Health, University of California, Los Angeles

it

Department of Economics, University of Colorado, Boulder

^School of Medicine, Univers j ty of California, Lob Angeles

"f"

Department of Statistics, University of Wyoming, Laramie

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ACKNOWLEDGEMENT

We thank, without implicating, Professor Rodney Beard, M.D. , Stanford
University; Professor Virginia Clark, Ph.D., University of California, Los
Angeles; Professor Timothy Crocker, M, D. , University of California, Irvine;
Professor Carroll Cross, M.D., University of California, Davis; Dean Roger
Detels, M.D., University of California, Los Angeles; Professor Henry Gong,
M.D., University «1 California, Los Angeles; Professor Steven Horvarh,
M.D., University of California, Santa Barbara; Professor Mohammad Mustafa,
Ph.D., University of California, Los Angeles; Stanley Rokav, M.D., American
Lung Association, Los Angeles; and Cerschcn Schaeffer, M.D. , Riverside,
California for their perceptive suggestions concerning the design of the
proposed study described in this report. This feasibility study was
financially supported by the USEPA under its cooperative agreement
#CR-S11077-01-0 with the University of Wyoming. We thank Alan Carlin, Ann
Fisher, George Provcnzaro, and Ralph Luken of USEPA for their patience and
encouragement throughout the duration of this project.

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TABLE OF CONTENTS

Page

Acknowledgement 		iv

list of Figures		vii

List of Tables		vii

1.	Introduction and Executive Summary 		1

2.	Symptoms and Health Effects of Ozone Exposure . 		6

2. 1 Overview			6

2.2 The Ozone and Health Relationship		7

3.	Geographic Distribution of Benefits from

Ozone Reduction		IS

3.1	The Geography of the U.S. Ozone Problem	18

3.2	Implications of Past Ozone Benefits Research . . . .	23

4.	Theoretic?,] Basis for the Benefit Estimation Methods

to be Applied .....................	31

4.1	Averting Behavior tiethod (ABM)		31

4.2	Contingent Valuation Method (CVM) 		35

4.3	Direct Cost Method		3?

5.	Data Collection and Sampling Strategies 		40

5.1	Source of Subjects		40

5.2	Selection of Community				41

5.3	Sampling		42

5.4	Recruitment		44

5.5	Payment of Subjects		45

5.6	CORD Measures		45

5.7	Baseline		46

5.8	Follow-up		47

5.9	Hot-line		48

5.10	Air Pollution Measures	 48

5.11	Data Collection Instruments 	 50

Data Management	 50

5.12	Analysis	 51

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Page

6. Tiine Line of Performance ai»d !V liveranee .........	53

Bibliography 		55

Appendices

A.	Background Questionnaire 		61

B.	Fa]lnw-Up Questionnaire 		96

C.	Environments 1 Effects Evaluation Program Questionnaire , .	130
P, Transcript of Ozone and Health Telephone Conference ....	151

E.	Further Notes on the Telephone Conference .........	181

F.	Power Analysis -'n the Determination of Sample Sizes for

the Proposed Ozone-Health Study 		184

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LIST OF FIGURES

Figure	Page

3.	1		24

3.	2		27

3.	3		27

3.	4		29

4.1 Example Adapted from Schulze et al, (1983)		39

LIST OF TABLES

Table	Page

- 1 Summary of Selected Ozone (0^) Studies Performed in

Environmental Chambers	12

3.1	Ozone Violation Days and Populations by Census

Division, State and County	19

3.2	Distribution of Person Standard Violation Days by Census

Division			22

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SECTION 1

INTRODUCTION AND EXECUTIVE SUKMAHY

Frevious. research efforts aimed at estimating the dollar health
benefits of reducing ozcr.e levels h;>ve focused raainlv on measures of
illness. For example, Gerkir.g, Stanley, and Keirick (27) examined the
connection between Che health of St, louis residents, the ozone levels they
face, and their consumption of medical care. Additionally, Portney and
Mullahy (59) analysed the impact of ozone on health measures such as
restricted activity days, bed disability days, and work loss days among
respondents in the 1979 national Health Interview Survey, Studies in this
vein, however, do riot explicitly consider the health benefits arising from
reductions in subclinical or minor syr.pt orati c discomforts of ozone,
Reducing these discomforts, which include chest pain, headache, and general-
malaise, is a potentially large source of dollar benefits for three
interrelated reasons. First, as discussed more fully in section 2, minor
symptomatic discoraforts can occur even in healthy adults at ambient ozone
levels below the present federal standard of .12 ppra. Second, even though
these discomforts are less serious than illnesses such as asthma,
emphysema, and chronic bronchitis, they do cause individuals to limit
activities. Third, these discomforts and associated activity limitations
p re experienced by a large share of the exposed population. As a
consequence, willingness to pay to avoid then cay be substantial and should
be taken into account in the regulatory impact assessment process.

The purpose of this feasibility study is to shew how to effectively
pursue research Into measuring the benefits of reduced minor symptomatic
discomforts associated with ozone exposure. Few benefit estimates are not
provided here, although some existing estimates are applied. Instead,
attention is directed to showing how an appropriate research methodology
can be implemented using a sample drawn frora participants in previous
studies of chronic obstructive respiratory disease (CORD) conducted in the
Los Angeles area. As a consequence, this feasibility study may be viewed
as a proposal to implement Component 1-Phase 2 and Component 2 of the
cooperative egreemeTit application entitled, "Inproving Accuracy and
Reducing Costs of LnvironrentnJ Benefit Assessments." These components
call for new research in the area of valuing morbidity benefits and focus
on the health effects of ozone. If supported, the resulting research
project would be conducted jointly by economists, medical scientists, and
epidemiologists, at the Universities of Colorado, Wyoming, and California
(Los Angeles). Members of the medical science and epidemiology segments of
the research group have been extensively involved in the various COED
studies conducted over the past ten years. Their vitee, together with
chose of the principal economists included, may be found in above mentioned
cooperative agreement application.

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The ultinr.tc ob i ec l J ves of this propound p ro j ec t are Co: H) measure

the association between prevalence and intensity of minor symptomatic
discomforts and ozone exposure and (2) estimate dollar values for the*
discomforts identified. The research would be conducted over the period 1
Feb 35 - 31 War 86, although all dats would be collected and analyzed prior
to 31 Dec 85. ley deliverables from the project include draft reports
summarizing all findings to be forwarded to US EPA during the 1985 calendar
year. The 1 af• t three months of the pro/'L period would he devoted to
final report preparation. Additional information concerning the time
phasing of the project may be found in section 6 and a detailed budget for
the project can be found in the cooperative agreement application.

As indicated above, investigators for this project would be drawn from
the fields of medical science, epidemiology, and economics. From the
viewpoints of ircilicai science and epidemiology, the proposed research will

address two broad questions concerning the relationship between symptoms
and ozone exposure levels. These are: (1) what are the effects of ozone
exposure on sensitive, vulnerable, and normal individuals that might be
expected at low levels of ozone exposure? and {2} at what levels of ozone
exposure are these effects likely to occur? Unfortunately, comparatively
few answers are currently available on either of these questions. As
discussed in section 2, most previous research on the health effects of
ozone has focused on exposure levels that are between two and seven times
the present national standard. In a sense, this situation parallels the
previously noted tendency of economists to base benefit estimates for ozone
control on reductions in illness. Yet, evidence of minor symptomatic
discomforts appearing at much lower levels of exposure in health adults is
not unknown even though the discomforts may be subtle and not readily
apparent in usual clinical testing procedures. For example, Goldsmith (29)
showed an increase in airways resistance in 2 of 4 persons studied at .10
ppm and Vcn Nieding (55) showed an increase in airways resistance at this
level along with a change in blood P02 levels. Moreover, in a recent
telephone conference conducted to support the feasibility study (see
transcript in Appendix D) , acknowledged experts on the health effects of
ozone stated that individual responses to thai pollutant are highly
variable, depending on factors such as extent of exercise, acclimatization,
immediate history of exposure, and severity of existing respiratory or
cardiovascular disease. This situation suggests that the levels of ozone
exposure associated with the onset of .symptoms r.ay vary greatly across
individuals as well.

These questions conceruiup; the onset ut symptom? are of immediate

policy relevance. As explained in section 3, the exposure levels at which
synptores first btgin to appear is a critical deterir.ir.ant of the magnitude
of economic benefits. For example, suppose that for the "average"
individual, the threshold ozone level at which symptoms first appear is .07
ppm. In this case, using estimates drawn from Schulze et al. together with
soire simplifying assumptions regarding the distribution of daily ozone
le-vt-Js, the benefits associated with meeting a .1? ppm standard would he
roughly $170 per household per year. On the other hand, if the threshold
level for health effects is instead .12 ppm, then the corresponding benefit
calculation yields a much smaller figure of approximately $15 per household

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per year. Using the lower of the two figures, section 3 alsc reports a
conservative "guess" that the total national benefit of meeting the present
ozone standard is $750 nillion annually. Given the disproportionately high
ozone levels experienced in California, approximately 70 percent of those
benefits would accrue to residents of that st?te. The remaining 30
percent, or about $200 million in benefits, would be principally
distributed to residents of states in the New England, Middle Atlantic, and
Vest South Central regions of the S. Consequently, although ozone
pollution is concentrated in California, it remains an important national
problem.

In the proposed research project, the improved knowledge of how and
when low level ozone exposure contributes to minor symptomatic discomforts
will become an important input to no re precise calculation? of the dollar
benefits of ozone control. These benefit calculations, which are explained
more fully ir. section 4, will be undertaken using three approaches: (1)
the averting behavior method (ABM}, (2) the ccr.t ingent valuation method
(CVM), and (3) the direct cost method (DCM)» The particular ABM approach
proposed is a generalization of the household production function framework
used by Gerking, Stanley, and Weirick (27) in their study of ozone
exposures in St, Louis, More specifically, sec ti or L. I presents a model in
which individuals engage in averting activities in order to avoid ozone
exposures and, thus, minor symptomatic discomforts. These activities,
which include spending more time indoors and/or traveling to a Jess
afflicted location, forr, the basis for splitting out the benefits of
reduced minor symptomatic discomforts from benefits of reduced illness.
Thus, the relative size of these two components of the total health bid to
avoid ozone exposure can be compared. The benefit neasure derived
indicates that at constant utility levels, an individual's willingness to
pay for a small, reduction jn ozone level.s is determined by three frotors:
(1) the extent to which symptoms are reduced directly, (2) the efficiency
with which averting activities can reduce symptoms, and (3) the cost of
engaging in averting activities. Even though the nethod relies on a model
in which utility is maximized, no utility terms appear in the benefit
measure derived making the Treasure straightforward to implement,
empirically.

Second, the CVM approach to be applied is similar tc the research
design used by Ioehman et a 1. (50), However, the proposed research will
differ from the Loehman et al. study in three important respects: (1)
pollutant concentrations will be measured using data on episodes which are
fresh in the minds of respondents, rather than as annual averages, (2)
separate benefit estimates will be obtained for reductions in specific
minor symptomatic discomforts such as cough, chest pain, headache, throat
irritation, depression, and sensitivity to bright light* and (3) separate
dose-reaponse estimates will connect the prevalence and severity of these
discomforts to ambient o?one levels for the members of each of three
subsanples. (The composition of each of these subsaraples will be described
¦momentarily.) Thus, individuals will be valuing only the symptoms which
have been reported by members of their group at varying exposure levels.

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Finally, although not a major focus of this study, some effort will be
devoted to the direct costing of symptoms of ozone exposure. Once
dose-response functions have been formulated by medical scientists costs of
relieving the symptoms identified will be explored. Additionally, direct
costs ot restricted activity days and work loss days will be examined using
procedures similar to the dose-response analyses of Portray and Kullahy
(59).

These three benefit estimation methods will be applied to new data
obtained from approximately 200 participants in prior CORD studies
conducted by UCLA, This sample will be drawn from two CORD eomrr.ur 1 ties;
Burbank and Glendora. The foraer community has moderate ozone levels while
ozone pollution in Glendora is more severe. Additionally, the sample will
be stratified into the following three groups (mentioned in the discussion
of CVMl: (1} 60 individuals with physician diagnosed respiratory diseases
including asthma, chronic bronchitis, and emphysema, (2) 80 individuals who
regularly engage in heavy recreation.? 1 or occupational exercise, and (3) 80
"normal" individuals, In order to reduce confounding influences, all
sample members will be nonsmoking adult (aged 25-59 years), full-time
workers. The new data will he collected on the 200 respondents in two
phases. First, extensive baseline data will be collected by home visit
(see questionnaire in Appendix A), Second, each sample member will be
telephoned about once per month according to a protocol determined so as to
maximize days with ozone exposure and to balance weekday and weekend
reports. These follow-up interviews will gather Information concerning the
day of the call and the two previous days {see questionnaire in Appendix
B), This data collection method is expected to be superior to the diary
approach. With the telephone follow-up interviews, the recall period is
short and the time period ef interest can easily be targeted.
Additionally, entries in the diaries used in previous health studies often
are completed on an irregular basis, thus turning theia into de_ facto
retrospective data collection instruments.

In summary, the proposed study will focus on how ozone exposure
affects minor symptomatic discomforts including chest pain, headache, and
general malaise. This focus is warranted because these discomforts Unit
activities and are experienced by a large share of the exposed population.
Thus, willingness to pay to avoid their, may be substantial and should be
taken into account in the regulatory Impact assessment process. The
research will be undertaken jointly by a team of economists, medical
scientists, and epidemiologists from the Universities of Colorado, Wyoming,
and California (Los Angeles). They will pursue two closely interconnected
objectives to: (i) measure the association between prevalence and
Intensity of minor -symptomatic discomforts ?nd ozone exposure and (2)
estimate dollar values for the discomforts identified. Special emphasis
will be placed on identifying the levels of ozone exposure at which
particular symptoms begin to appear. Little medical or epidemiological
research has been done in this area and the exact exposure levels that

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trigger symptoms are a critical determinant cf the magnitude of economic
benefits. These estimates of economic benefit;;, in turn, will be obtained
on the basis of extensive research in applying three approaches: (J) the
averting behavior nethod, (2) the contingent valuation method, and (3) the
direct cost method, Consideration of the case of ozone pollution,
therefore, will advance the strte of the art in developing benefit
estimates, permit the cost-effectiveness of alternative methods to be
compared, in addition to producing policy relevant benefit estimates.

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SECTION 2

SYMPTOMS AHD HEALTH EFFECTS OF OZONE EXPOSURE

2.1 Overvi ew

The relationship between ozone and health has been studied by a number
of means including clinical and epidemiologic studies. In the clinical
studies, (see Table 2,1 and the corresponding references in the list of
reference?) (1-4, 12, 20, 22-24, 28, 29, 31-35, 39, 43, 44, 47-49, 52, 55,
62, 64, 71), individuals are exposed to known cnnctntrationc cf ozone and,
on a separate occasion, to "clean" air, for specified periods of time,
while at rest and/or engaging in intermittent light exercise or in moderate
to severe exercise. The responses of the individual in terms of symptoms,
physical signs and changes in lung function parameters, such as FEV,, other
forced expiratory flow rates, airway resistance, subdivisions of " lure
volume, dynamics of lung compliance, etc., ore assessed during and
following the exposure. In the epidemiologic studies (13-15, 37, 45, 60,
68, 69), groups of individuals exposed and unexposed to ambient levels of
pollution are studied and compared, or groups of individuals intermittently
naturally exposed to high and low levels of air pollutants are studied at
those periods and compared across time.

Both clinical and epidemiologic studies have advantages arid
disadvantages and are better considered as ccirpl cn.entary ways of addressing
an extremely complex problem than as adversarial approaches. Clinical
studies have the advantage that level and duration of exposure (and dose to
the respiratory tract, if minute ventilation Is measured), are known and
that appropriate measurements can be r.ade during and following the exposure
according to predetermined protocol, In addition, clinical studies are
likely to be performed on sensitive or vulnerable individuals, ro that
worst case response can be studied. The major disadvantage is that chamber
exposure is, necessarily, a simplified model of that faced by free living
populations, Epidemiologic studies deal with the naturally occurring
exposure of free living individuals, but lack the precise characterization
of personal exposure and the opportunity for timely observations and
measurements available in the clinical study.

The research prupoped falls into the epidemiologic category in that

the response to ozone exposure among free living individuals will be
studied. This section briefly summarizes what has been learned from
clinical .studies about the ozone and health relationship. The focus on
clinical studies here is warranted because they provide a useful, though
imperfect, guide to the symptoms that sensitive, vulnerable, and normal
Individuals might experience at particular exposure levels. Moreover,
these results, together with previous field experience, lie behind the

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construction of instruments for the present study that are designed to
collect information on symptomatology. These, instruments are described
r.ere iully in section 5 and draft version? of then are presented in
Appendices A and 8,

2,2, The Ozone and Health Relationship

Ozone is one of the major components of photochemical smog due Co
hutran activities and is usually present in ambient concentrations of about
0,05 ppm at sea level. In certain geographic regions, such as the Los
Angeles area, hourly average concentrations of 0,£~-0.35 ppm are
occasJonally reached during community air pollution episodes and peak
concentrations 0,6-0.8 ppm have been recorded. As indicated previously,
the federal air quality standard for ozone presently is set at .12 ppm.
Durlrg episodes of photochemical pollution, respiratory symptoms are widely
experienced. These are related to irritant effects of ozone and ether
components in the photochemical complex on r.ucous membranes of the ro?e,
throat and lower airways, producing in some individuals cough, wheezing,
and a sensation of chest constriction or burning. Effects on the lower
airways are believed to be enhanced by physical activity because of the
increased ventilation and tendency towards mouth breathing during the
hyperpn^a of exercise.

Toxic effects of ozone itself on the respiratory system have been
investigated in a number of animal and human studies involving controlled
exposure to ozone at levels that can be experienced in community air.
Chronic continuous;; or intermi r tenu exposure of experimental anime 1 k,

including primates, to ozone concentrations in the range of 0.35 to 1 ppm
have produced morphologic changes indicating toxic injury to the epithelium
of proximal and peripheral airvays and to type one alveolar epithelial
cellf <6, 9, 10, 12, 16, 17, 26, 40, 53, 57, 65-67, 70). Susceptibility to
the toxic effects of ozone varies with species, age, and prior exposure,
effects of chronic exposure being modulated by adaptive and repair
mechanisms. Most hunan studies of ozone effects have involved only
short-term challenges (5 min-6 h).

Selected studies of human exposures to ozone in environmental chambers
are summarized in Table 2.1. Whereas scute exposures to ozone
concentrations of less than 0,37 ppm have produced variable changes ir, lung
function (5, 20, 24, 29, 31, 32, 34, 35, 47, 55, 84), human challenges with
higher concentrations have generally led to definite deererients in to feed
expiratory volumes and flow (1 2, 20, 21 , 33, 36, 41, 45, 64), and
functional changes due to expc.sure to any given level of ozone have been
accentuated by exercise (12, 20, 21, 23, 34, 35, 40, 45, 55, 64). Upon
exposure to ozone concentrations cf 0.37 or 0.5 ppm, normal volunteers have
experienced cough, substernal pain, wheezing, and malaise not reported
durinp control exposures (31, 32). The limited data available concerning
effects in mar of repeated intermittent exposure over a few days to sever.-1!
weeks suggested that tolerance to the effects of ozone on lung function can
occur after only limited exposure (5, 24, 34, 35, 58).

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The possibility of persistent changes due to longer term iintermittent
exposures has not been adequately investigated, however, there is some
evidence that damage may be cumulative. Damage may be cumulative. Chamber
studies (24, 33-35, 64, &9) indicate an acclimatizaticn or habituation
affect of higher levels of ozone exposure over the short term. Betels et
al. [see reference attached here] report that a cohort exposed over five
years to higher connumi ty 1 eveIs of oxidant pollution {primarily) have
greater decrement in lung function than a cohort exposed to much lower
level*,, indicating a cumulative effect of the exposure in the long terra.

To assist in planning the proposed study, of the health effects of low
level ozone exposures, a telephone conference was arranged. The invited
participants are among the acknowledged experts and represented
epidemiology, clinical medic in e, experimental clinical medicine, and
environmental sciences. Participants were:

Professor Rodney Heard, M,D,

Stanford University

Professor Timothy Crocker, K.D.

University of California, Irvine

Professor Carroll Cross, l!,D.

University of California, Davis

Dean Roger Detels, H.D.

University of Caliiornic, lcs Angeles

Professor Steven Hcrvath, H.D.

University of California, Santa Barbara

Professor Mohammad Mustafa, Ph.D.

University of California, Los Angeles

Stanley P.okaw, H.D.

American Lung Association, Los Angeles

Ccrshen Schaeffer, K.D.

Riverside, Call form a

Ar.r.e. Coulson, Research Epidemiologist and Professor Donald P, Tashkin,
M.D. , both of UCLA planned and rr.oderated the conference. The transcript of
the conference is included as Appendix C. Symptoms which the panel agreed
were most likely in response to ozone exposure were:

1)	Cough, which was regarded as the most common ryirptom

2)	Pain on deep inhalation

3)	Kausea

4)	Headache

5)	Threat irritation

b)	Moodiness

7) Distractabi]ity

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8)	Lethargy

9)	Decrease in work capacity

10)	Depression

11)	Happening effect on iroti vation

12)	Irritability

13)	Susceptibility to infection

14)	Sensitivity to bright light

Eye irritation was mentioned as a common response to oxidant air pollution
exposure. Technically, it is not due to ozone but to the presence of PAN
in the total oxidant mix. However, it is a useful measure of oxidants,
approximately 95 percent of which is ozone.

It was generally agreed that the effect of ozone exposure Is
considerably modified by the activity of the subject. Several of the
••ypcrt panel reported that eypesure of normal individuals in a quiet state
of levels of ,3 and .4 did not produce symptoms, whereas active individuals
developed symptoms at levels of ,14 - ,18, Additionally, there is sore
inti icii t ion in work currently underway (private cermuni eati on from Henry
Gong and Donald Tashkin) that trained athletes performing at high levels of
exercise my be adversely affected at .12 ppm. Bates suggests that
sensitive individuals may respond at O.J I!, the Federal Air Quality
Standard,

Lower levels at or below the federal standard nay also have adverse
effects. As previously noted, of the studies reported in Table 2,1, few
reported any health measurements nade r.t ozone levels below .12 ppi^..
Moreover, adverse health effects in this range of exposure tnav be subtle
and not readily apparent in usual testing procedures. On the other hand
I«tb 11' 2,1 indicates that effects at .10 ppr. are not completely unknown,
for example, Ooldftr.ith (25) shoved an increase in airways resistance in 2
of 4 persons studied at .1 ppm and Vcn f*itdirg (55) shcvi-d an increase in
aitv-ays resistance at this level along with a change in blood PC2 levels.

The acute effects at the lot- exposure levels may be indicated by
subtle changes in behavior, possibly triggered in part by the odor,
detectable at .04 pptu, and the appearance of air containing photochenica]
oxidants, 95 percent of which, as indicated above, is ozone. The
individual r.ay not be avsre that the behavioral changes are associated with
the ozone exposure levels. But if the changes are so associated, days with
low levels of exposure should be rore like the higher exposure days than
the high air quality days in terms of outdoor activ icy-

Since adverse effects of exposure to even low levels of ozone are
likely to exist, there raay be substantial numbers of people in and outside
California modifying their behavior, lifestyle, and activities in response.
If these r.inor effects are compiled with idiosyncratic sensitivities of the
individual such that, n recognizable effect usually occurs when the two
exposures occur together, the effect deriving from the ozone exposure may
go unnoticed in the hay fever associated with, say, golden rod or roses.

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A precise deteripination of the exposure levels at which particular
synptoms appear, however, is complicated considerably by the tremendous
variability in rerrrr.se across individuals. For example, at - 4p-pm,
decrement ir FCV , ranges from 5 percent to ^5 percent. There is also
variability depending on acc.I iciatization: individuals from areas with very
low or no orrcre pollution are significantly more sensitive to lower levels
ct ozone thar. individuals who live in an r re a with continuing moderate
exposure (18, 20). Similarly, there arc di f f erencer, in response to a given
exposure depending en the immediate history ci exposure. Response is
cininal nn the first day, rising on the second ant third and then falling
away, or disappearing completely on days 4 and 5 {18, 25, 58), If the
initial day oi a sr.eg, episode is folio-wed by & single clear day, the
response on the next day (if siroggy) is like the second day of the
continuous smog^y days.

Sensitive individuals certainly react, on the average, at the same
levels ,-i5 normals. There, is core d; ?afreement as to whether they react at
lower levels. The panel generally agreed that individuals with ccitpromised
respiratory systems with sensitive airway:; > fasthma, bronchitis, emphysema)
voo id, on the average, be wore sensitive to given levels of ozcre exposure.

Short-term exposure to oxidant pollution can increase the sensitivity
of the airways to non-specific brorchoconstricter substances, such as
histamines (28, 42, 56). Therefore, individuals with persistently
hyper-reactive airways, namely asthmatics, wight be expected to be*, it ere
vulnerable to asthmatic attacks after exposure to elevated concentrations
of ozone; in some subjects, this increased vulnerability cay persist for up
to several days folltwing the exposure.

Individuals with breathing problems caused by other diseases;, such as
shortue^s of breath associated with congestive heart failure, might be
expected to respond at 1over levels thar normal.

Another group which would be expected to respond at lower levels or
more strongly et the same level, is comprised of those who exercise
heavily, The deep breathing of athletes and tie resulting high minute
ventilaticr exposes there individuals to more of the ambient ozone
pollution than those vith lower minute ventilation and the same exposure.

The possibility that children may be particularly vulnerable to ozone
effects, in terras of symptom-tic response, has not been studied. There may-
be serious problem- of pulmonary growth and development associated vith
exposure, based on animal studies, but this night not be observable in
overt fyirpters. Children, however, may be especially exposed because of
outdoor play and, like athletes, high levels of e>;ert:ion and minute
ventilation. The panel recommended that reports on children from the
adults interviewed be obtained. However, no special sensitivity was
remarked air.eng the elderly. Persons over 70 have been exposed to levels cf
.4 ppim for one to two hours without the appearance of svr.pt oms.

The levels of ozone exposure at which symptoms begin to appear turns
out to be of critical importance in est iv>ating benefits. That point Is

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(lemnrFt rated in section 3 to follow, which also presents some preliminary
nnd necessarily approximate benefit estimates of ozone control.

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TABLE 2,1

SUMMARY OF SELECTED OZONE (O-j) STUDIES PERFORMED IN ENVIRONMENTAL CHAMBERS

V I i c Aucfru i
< S-\ li'tivct)

l

]t'<. I r, | Vtivf ty

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(continued)

-------
Tabic 2.1 (continued)

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