EPA-600/3-77-113
October 1977
Ecological Research Series
INTERNATIONAL CONFERENCE ON OXIDANTS,
1976 • ANALYSIS OF EVIDENCE
AND VIEWPOINTS
Part I. Definition of Key Issues
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal spe-
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This document is available to the public through the National Technical Informa-
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EPA-600/3-77-113
October 1977
INTERNATIONAL CONFERENCE ON OXIDAHTS, 1976
ANALYSIS OF EVJDENCE AND VIEWPOINTS
Part I. Definition of Key Issues
Basil Dimitriades and A. Paul Altshuller
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
- OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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DISCLAIMER
This report has been reviewed by the Environmental Sciences Research
Laboratory, U.S. Environmental Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily reflect the views and
policies of the U.S. Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorsement or recommendation
for use.
In general, the texts of papers included in this report have been repro-
duced in the form submitted by the authors.
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ABSTRACT
In recognition of the important and somewhat controversial nature of the
oxidant control problem, the U.S. Environmental Protection Agency (EPA)
organized and conducted a 5-day International Conference in September 1976.
The more than one hundred presentations and discussions at the Conference
revealed the existence of several issues and prompted the EPA to sponsor a
follow-up review/analysis effort. The follow-up effort was designed to review
carefully and impartially, to analyze relevant evidence and viewpoints reported
at the International Conference (and elsewhere), and to attempt to resolve
some of the oxidant-related scientific issues. The review/analysis was con-
ducted by experts (who did not work for the EPA or for industry) of widely
recognized competence and experience in the area of photochemical pollution
occurrence and control.
Part I of the overall effort is an explanatory analysis of the problem
and definition of key issues, as viewed within the research component of the
EPA. Parts II through VIII are written by expert reviewers offering either
resolutions of issues or recommendations for additional research needed to
achieve such resolution.
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CONTENTS
ABSTRACT iii
INTRODUCTION 1
THE ISSUES 3
Introduction 3
The Issue of Reactivity 5
The Issue of Stratospheric Ozone Intrusion 6
The Issue of Natural Organic Emissions 8
The Issue of Oxidant Transport 11
The Issue of Current Air Quality Simulation Model (AQSM)
Utility 15
The Issue Regarding the Evaluation of a Smog Chamber
Method as a Replacement for the Appendix-J Method 18
The Issue of Oxidant/Ozone Measurement 18
The Issue of Optimum Oxidant Control Strategy 22
REFERENCES 29
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INTRODUCTION
Basil Dimitriades and A. Paul Altshuller
The photochemical oxidant pollution problem in the U.S. has been recog-
nized for several decades. While some control of oxidant precursor emissions
was first enforced in the early 1960s, it was not until 1971 that an official
oxidant control strategy was formulated and legislated into use (1). Despite
the preceding long years of research and development effort addressed to
understanding the problem and conceiving solutions, this first strategy has
had all the usual uncertainty problems that accompany any first effort or
result.
In the years since the inception of this first strategy, several develop-
ments have taken place. First, experiences by enforcement agencies brought to
surface several enforcement or implementation problems heretofore unsuspected.
Second, considerable new research was conducted and reported with strong
implications relevant to the oxidant control problem. Third, the problem, now
recognized in other countries, has acquired international dimensions because
of the possibility of intercountry pollution transport and because of the
impact of emission control regulations upon international trade. These
developments raised the question of the need to reexamine the oxidant control
policies and their underlying scientific bases, and eventually instigated the
International Conference on Photochemical Oxidant Pollution and Its Control,
held in Raleigh, N.C., September 12-17, 1976, under the auspices of USEPA and
the Organization for Economic Cooperation and Development (OECD) (2).
This paper was originally published as "International Conference on Oxidant
Problems: Analysis of The Evidence/Viewpoints Presented. Part I. Definition
of Key Issues." APCA Journal, Vol. 27, No. 4, April 1977. Reprinted with the
permission of the APCA Journal.
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Some one hundred reports on new evidence and/or viewpoints were presented
at the International Conference by researchers and air pollution specialists
representing the entire spectrum of scientific community, and, as expected,
brought into focus some important and controversial issues. Because of the
wealth of new information presented on these issues, and because of the often
conflicting nature of this information, and finally, because of the great
importance of these issues, it was felt that it would be extremely useful to
carefully scrutinize and analyze all presented information on each issue, to
attempt to reconcile any conflicting evidence and/or viewpoints, and finally
to arrive at a judgment that would either pronounce the issue essentially
resolved or declare the differences in evidence/viewpoint irreconcilable, and
to define needs for additional specific research. Perhaps it should be re-
stated that the subjects of this effort are existing issues, that is, ques-
tions that have been given concrete but conflicting answers. Needless to say,
there are innumerable relevant questions that have not been given any answers
or not even studied yet; this effort clearly is not intended to seek answers
to these latter questions.
The first step of this analysis effort was completed in October 1976 and
is reported here. In this first step, the entire problem of oxidant pollution
and its control has been rethought and, drawing upon our experiences and
judgment and upon information reported at the International Conference and
elsewhere, we have defined certain issues, specifically, those we feel per-
tained to the key components of an optimum oxidant control strategy.
The second step of this analysis — to be conducted by review panels —
consists of a careful review of all Conference papers (and other reported
information) directly or even peripherally dealing with a given issue. Each
review panel member has been requested to prepare a review, the purpose of
which is (a) to examine the reported evidence and viewpoints for conflicts;
(b) to make judgments on strengths and weaknesses of opposing viewpoints or
evidence and, based on such judgments, attempt to reconcile conflicting view-
points and evidence; and (c) to derive a factual or judgmental conclusion
regarding resolution or the status of the issue and offer recommendations for
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additonal research. Such reviews have been solicited from several experts who
do not work for EPA.
In the third step of this analysis, the reviews to be obtained for each
issue will be combined into a single report that will include (a) the individ-
ual reviews intact, and (b) a digest of all reviewers' conclusions with a
discussion of their implications regarding the oxidant control problem. It
was planned that these reports be published either as journal articles or as
EPA reports. If and when review panel meetings are called for, such meetings
will be organized and funded by EPA.
THE ISSUES
INTRODUCTION
Questions that must be answered, or, alternatively, distinct components
of the problem of oxidant pollution and its control involve the following:
o Nature, extent, and magnitude of the problem.
o Controllable and uncontrollable sources of the problem and relation-
ship between source area and receptor (problem) area.
o Air quality goal that must be achieved, that is, the National Air
Quality Standard for Oxidant/Ozone (NAQS-O ).
X
o Achievability of the NAQS-O .
X
o Methods for calculating emission control requirements.
o Methods for controlling emissions from sources.
o Methods for reducing sources/emissions in an area.
These questions or problems must be resolved if oxidant control measures
are to be developed and applied. Since application of such measures is dic-
tated by law in the U.S. (3), it follows that these questions must be given
answers, some of which may be based on sound and complete evidence and some
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based by necessity on incomplete evidence or merely reasonable speculation.
This dictates that the review effort requested here should not be preoccupied
with whether there are answers that meet a prescribed set of validity criteria
or not. Rather, the objective should be to offer answers, based either on a
consensus of viewpoints and evidence or on a "referee" judgment when existing
viewpoints and/or evidence are in conflict.
The scope of this review also must be by necessity limited. For reasons
mainly of effort manageability and practicality, the scope of this review must
be limited to include only some of the questions at issue, obviously those
that are relatively more important and were given extensive coverage at the
International Conference and elsewhere. Such a piecemeal examination of the
oxidant problem often presents difficulties, the most serious of which is the
apparent reluctance of the average reviewer to judge the various components of
a problem independently of each other. This problem is well recognized but no
solution is offered here other than to appeal to the reviewer's better judg-
ment. The success or failure of this effort clearly will depend on the
degree to which the reviewer's reasoning adheres to the relevant scientific
evidence available and remains unbiased by forseeable consequences or implica-
tions of the conclusion.
Based on our own appreciation of the various aspects of the oxidant
problem and the coverage these aspects received at the International Confer-
ence and elsewhere, we have defined and offer the following issues to be
included in this review effort. In the hope of providing some review guide-
lines of assistance, we have attempted, in each case, to briefly analyze the
issue, explain its position and relevance within the oxidant problem picture,
and raise the specific questions that constitute the issue, and the answers to
which are the very objective of this effort. We have also identified and made
available to the reviewers copies of those Conference papers that in the
authors' judgment are relevant to each issue. Needless to say, the reviewers
may request and will be provided with copies of any additional Conference
papers or of any other available reports.
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THE ISSUE OF REACTIVITY
In regard to reactivity, the questions most urgent and directly related
to the oxidant control problem pertain (a) to the effectiveness of "substitu-
tion" (of less reactive for more reactive organic emissions) as an approach to
oxidant control and (b) to the identification of those organics that are
essentially of no concern insofar as the oxidant problem is concerned. The
more specific questions that need to be answered follow.
• Does the scientific evidence alone justify formulation and enforce-
ment of interim substitution rules more stringent than Rule 66?
• Considering all relevant factors, e.g., impact upon urban air qual-
ity, impact upon rural air quality, cost, technological feasibility,
etc., would it be preferable to abandon altogether the idea of devel-
oping interim improved substitution rules and devote instead and
immediately all attention and resources to development of methods and
practices for "nearly indiscriminate" control of organics?
• Are there any organics so little reactive that they would neither
cause nor contribute significantly to oxidant buildup at problem
levels under any circumstances?
There are also the relatively less important questions regarding definition of
reactivity and validity of the data and procedure used to classify organics
based on their relative abilities to contribute to the urban oxidant problem.
Of these questions, the one on the merits of substitution has been dis-
cussed both internally in EPA and informally at an open meeting (EPA's Forum
on Solvent Substitution, Chicago, 111., Oct 13-14, 1976); there was a consen-
sus that substitution will have a small but possibly significant benefit upon
urban air quality — more precisely, the air quality in the vicinity of the
source area — but will have less or no benefit upon distant downwind areas.
Although not quantitatively answered, the question was nevertheless treated
adequately so that further discussion here is not warranted. Also, the ques-
tion on merits of "nearly indiscriminate" control is outside the scope of this
review, since it calls for judgments on cost, technological feasibility, etc.
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The question that is offered as the specific subject of this review is
the one regarding the possible existence and identities of organics incapable
of causing oxidant problems. This question was discussed at the International
Conference and drew conflicting answers. The specific issue here is centered
around the method used for reactivity-rating the various organics and for
defining the borderline separating the reactive ones from those of virtually
no concern with respect to the oxidant problem. In general, two distinctly
different approaches were proposed: The smog chamber approach applicable to
all organics (4), and the mathematical modeling approach (5) applicable, at
present, to certain organics only, namely, paraffinic and olefinic hydrocar-
bons and aliphatic aldehydes. To facilitate the process of judging these two
and/or any other approaches, it would perhaps be useful to break the issue
down to two parts: One pertaining to the reactivity-rating of the organics,
especially of those of low reactivity, and one pertaining to the positioning
of the borderline separating the almost totally unreactive ones from the
reactives. Judgments that must be made are on:
• whether the two proposed approaches agree or disagree in results and
to what extent,
• whether one or the other or the two approaches combined in some way
or any other approach yields the most reliable results, and
• the specific additional research needed to substantiate or refute
these first judgments.
THE ISSUE OF STRATOSPHERIC OZONE INTRUSION
In a broad sense, the question at issue here is whether ozone of strato-
spheric origin contributes significantly to the ozone problems observed in
urban and rural areas. Aside from the possibility that stratospheric-tropo-
spheric exchange contributes directly and significantly to ground-level ozone
buildup, stratospheric ozone has also been proposed to have a "reaction-
trigger" function that accelerates and enhances photochemical oxidant for-
mation from hydrocarbon-NO precursors. The stratospheric ozone intrusion
2C
question is part of the broader question regarding the magnitude and extent of
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the ozone problem caused by natural causes, which in turn is a part of the
issue of achievability of the National Air Quality Standard for Oxidants
(NAQS-O ). To further explain the interest in the stratospheric ozone ques-
X
tion, it should be clarified and stressed here that this question, in fact the
entire issue of achievability of the NAQS-O , has no "bearing whatever upon the
X
justification of the NAQS-O ; such justification is based strictly on health
effects considerations. The stratospheric ozone question needs to be answered
only for the purpose of more accurately estimating the benefits to be derived
from anthropogenic emission reduction.
Evidence interpreted to show accumulation of stratospheric ozone within
the troposphere varies widely in type and degree of directness. Thus, high
levels of ozone were measured in the upper troposphere near tropopause discon-
tinuity points (6), evidence that attests to stratospheric origin most directly.
On the other extreme, ground-level oxidant buildup in some instances was
attributed by investigators to stratospheric intrusion only because these
investigators did not have or would not accept any other explanations (7).
Overall, direct, unequivocal evidence on the impact of stratospheric ozone
intrusion upon tropospheric air quality is lacking, and for this reason it may
be expected that the viewpoints and interpretations of evidence expressed to
date reflect to some — perhaps substantial — degree a subjective judgment.
At present, a realistic assessment would suggest that the extent (by
area), intensity (by concentration), and frequency of occurrence of strato-
spheric ozone buildup at ground level all vary widely so that single answers
and answers to all of the questions that constitute the issue cannot be given.
It would, therefore, be more productive to define and offer as the subject of
this review only those that are most relevant to the oxidant control strategy
issue and receive substantial research attention. These questions are pro-
posed here to be as follows:
1. Accepting that intensive stratosphere-troposphere exchanges do occur
at tropopause discontinuity points, what is the extent, frequency,
duration, and spatial/temporal predictability of such occurrences?
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The terms "extent" and "spatial" here refer to areas at high altitudes,
that is, near the tropopause, not at ground level. While quantitative answers
are not expected, at least, a judgment should be made whether such exchanges
are sporadic, unpredictable incidents causing local ozone accumulations or are
significantly extensive and predictable. Main interest, of course, is in
occurrences within the U.S.
2. Accepting that localized high concentrations of stratospheric ozone
can occur in the upper troposphere, what fraction of such ozone is
expected to reach ground level
(a) under meteorological conditions most conducive to downward
transport, and
(b) under meteorological conditions most conducive to photochemical
oxidant formation?
The questions asked here, in essence, are again whether or not strato-
spheric ozone excursions to ground level are sporadic, unpredictable incidents
causing only local, short-lived (e.g., a few hours) ozone accumulations, and
whether or not such excursions are likely to occur during smog episode periods.
The question concerning the possible "reaction-trigger" function of
stratospheric ozone is not raised here because, thus far at least, it has been
a subject of speculation only; no relevant evidence apparently exists, except
for a few as yet unreported smog chamber experiments. Nevertheless, comments
from the reviewers on this question are welcome.
THE ISSUE OF NATURAL ORGANIC EMISSIONS
This issue was originally raised as a result of an early report that, on
a global basis, rates of organic emissions from vegetation are considerably
higher than those from man-made sources (8). Although such natural emissions
and the anthropogenic emissions are for the most part geographically segre-
gated, it is nevertheless reasonable to suspect that natural organics, either
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emitted within the urban or nonurban area or brought in through transport,
could contribute to the ambient oxidant problem to an important degree. These
suspicions became considerably stronger — and for obvious reasons — as a
result of two recent findings: The occurrence of a pervasive rural oxidant
problem (9), and the high reactivity of terpenes (10', 11). In either case, the
finding could be interpreted to mean that natural organics may constitute a
significant source of oxidant. As in the case of stratospheric ozone, the
question regarding the importance of natural emissions as an oxidant source
needs to be answered only for the purpose of more accurately estimating the
benefits from man-made emission control.
From a first glance examination of the evidence relevant to this issue,
it becomes immediately apparent that certain components of the issue have
obvious answers or have been resolved based on scientific evidence, whereas
other components remain uncertain or unresolved. For example, it is unques-
tionable that vegetation does emit organic vapors and that some of these
vapors (terpenes) play the dual role of oxidant precursor and oxidant destruc-
tion agent. What is in question is (a) the nature (other than terpenic) and
emission rates of such vapors, and (b) the net effect upon oxidant of the
atmospheric reactions of natural organics. Some evidence relevant to these
questions does exist but does not necessarily provide answers. Researchers
are, in general, less familiar with the natural organic emissions, and this
lack of familiarity naturally casts doubts over all types of evidence avail-
able, from data on chemical identity and ambient concentrations to information
on atmospheric photochemistry and on emission and sink processes. It is be-
cause of this general lack of confidence that the specific questions offered
here as the questions at issue, include some of relatively basic nature.
These questions are:
1. Given the fact that terpenes are emitted by vegetation, does it
automatically follow, or is there evidence to show, that terpenes are
present in ambient air at levels commensurate with their emission
rates? Are such levels significant?
While it is almost certain that these questions can be answered one way or
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another, based on evidence available, the judgments needed here are not only
on the interpretation of such evidence but also on the reliability or overall
quality and conclusiveness of the evidence available.
2. Accepting the possibility that terpenes are present in ambient air at
significant levels, does the available evidence — from either direct
or indirect data or theoretical inferences — support a predominantly
ozone-producing or ozone-destruction role or both roles for such
terpenes?
In deliberating such a question, the distinction should be made and recognized
between urban and rural atmospheres. It should be clarified and stressed here
that the fact that the current concern is mainly about the urban problem does
not justify overlooking the rural situation. One reason for this is that
oxidant formed in rural areas could contribute importantly to the urban problem.
It is precisely this possibility that should be explored in deliberating this
question. To further explain, it is conceivable that in rural areas, that is,
in forested and thinly, but nevertheless significantly, populated areas, the
terpene and anthropogenic emissions could yield mixtures with organic composi-
tion and organic-to-NO ratios conducive to oxidant formation. This is one
theory that could explain the "oxidant/ozone blanket" phenonmenon — of uniform
variation of oxidant/ozone levels over large areas — observed in parts of the
country (12). Since this "blanket oxidant/ozone phenomenon" could be explained
by several theories, namely,
(a) photochemistry of terpenes mixed with anthropogenic emissions in
rural areas,
(b) photochemistry of anthropogenic emissions (alone) in rural areas,
(c) pollutant transport from large urban centers, and
(d) stratospheric ozone intrusion,
the judgment called for here is for the relative credibilities of the four
theories, and specifically, for the credibility of the terpene theory.
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3. The third question is essentially a solicitation of evidence and/or
viewpoint — reported or unreported — on the existence and photochemi-
cal pollution role of natural organic emissions other than terpenes.
THE ISSUE OF OXIDANT TRANSPORT
It is to be remembered that this review-analysis effort is concerned only
with existing issues, that is with questions that have been answered but
conflictingly. If such a definition of issues is to be observed strictly,
then while there are numerous unanswered questions there may be no issue
related to oxidant transport, at least, none other than those already defined
and discussed in connection with the stratospheric ozone and the natural
emissions. To explain, one major question relevant to the oxidant problem is
on the relative strengths of the natural and the anthropogenic sources in a
given region or area. This question has not been answered unequivocally and
quantitatively because anthropogenic pollutant transport makes it difficult to
assess the strength of the natural sources. The question has been answered
qualitatively, a consensus being that pollutant transport does occur and
contributes to oxidant buildup in areas far from the sources (13-15). Quanti-
tative answers, however, have not been agreed upon, and this disagreement
constitutes the issues already presented in the preceding two sections of this
analysis.
Aside from its connection to the natural vs anthropogenic sources ques-
tion, the phenomenon of oxidant transport is of interest for yet another
extremely important reason. This reason is the strong possibility — a fact,
to some investigators — that oxidant and/or oxidant precursors transported
from upwind sources obscure the role and impact of local emissions to a degree
that local control requirements cannot be estimated with confidence. In fact,
this obscuring effect is a problem of much broader nature, affecting both main
components of the oxidant control strategy, namely:
(a) the source-receptor relationship, that is, the geographical defini-
tion of the area within which emission control must be applied in
order to reduce the oxidant levels observed in a (given) locality,
and
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(b) the quantitative relationship between oxidant-related air quality and
precursor emission rates.
This connection between oxidant transport and oxidant control strategy is
a conclusion arrived at as a result of numerous recent field studies (13-15).
Specifically, these studies established that the emission-dispersion and
photochemical reaction processes do not have a simple and "local" nature as
was assumed in the designing of the first — and current — oxidant control
strategy. The phenomena of urban oxidant plume formation and movement, rural
oxidant occurrence (at problem levels), "Sunday-weekday effect," and nighttime
oxidant occurrence, previously either unnoticed or thought to be "odd," are
now believed to be manifestations of an extremely complex emission/pollutant
dispersion process. Such complexities, for example, are introduced by hori-
zontal and/or vertical transport of oxidants and/or of precursor mixtures to
long distances without excessive dilution.
It is this connection between oxidant control strategy and oxidant trans-
port, and, within this context, the specific areas of nature, extent of, and
consequences from pollutant transport, in which several questions exist and
need to be answered. Some of these questions have been given conflicting
answers, but the supporting evidence was in almost every case either scant or
none. For this latter reason, these questions should perhaps be considered as
"unanswered" questions rather than as questions at issue. Nevertheless, for
important and urgent reasons these questions will be included in this review/
analysis with the understanding that the need here is either for answers or
for specific recommendations for research that would provide answers. These
questions and related explanations/discussion are as follows:
1. What is the maximum range of ozone transport?
The question pertains specifically to ozone, and is concerned with the maximum
distance downwind that ozone can travel without excessive destruction or
dilution (e.g., no destruction or dilution more than 80 percent). Answers
have been offered, but are nonspecific and vary by several tens of kilometers.
Thus, from direct observations upon an urban oxidant plume it cannot always be
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ascertained whether the transported oxidant constitutes a fraction of the
concentration at the point of origin or is fresh oxidant formed during trans-
port. Most likely, both types of oxidant exist but in unknown, and not easy
to determine, proportions. The question involves considerations of chemistry
and meteorology (dispersion) and could perhaps be answered in parts. For
example, it would be relevant and useful to answer the following questions:
(a) What is the photochemistry-related lifetime of ozone?
Answers have been calculated for an ideal atmospheric system containing no HC
and NO pollutants, except for methane (and CO) at their global back-ground
X
levels (16). It is conceivable, however, that in the presence of trace-levels
of HC and NO — levels such that their potential for O_ formation is either
x 3
negligible or predictable — that the lifetime of O may be quite different.
(b) What is the range of ozone lifetimes related to atmospheric (at
ground level) on surface destruction processes?
(c) For an inert pollutant, what is the longest lifetime related to
the atmospheric dilution process?
2. What is the maximum range of oxidant-precursor transport?
The question pertains to HC and NO pollutants as a mixture — not to the
individual precursors — and is concerned with the maximum distance '.ownwind
that a HC-NO mixture can travel without excessive loss of its potential for
oxidant formation, (e.g., no loss of oxidant potential more than 80 percent).
The question is far more complex than the preceding one on ozone; nevertheless,
answers have been offered, although again nonspecific and diverse. For example,
analysis of aerometric data provides evidence suggestive of "long-range"
transport but does not identify corresponding source and receptor areas.
Also, based on meteorological modeling techniques, it has been calculated that
the residence time of air parcels — and their pollutants — in high pressure
systems can be as long as several days (17); but this does not necessarily
mean that the resident pollutants preserved a significant potential for oxidant
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2. Smog Chamber Approach. The approach entails deriving cause-effect
relationships between oxidant and precursors through laboratory
testing. This approach could be characterized as semi-empirical
because the relationships are derived from laboratory observations
alone; they are not product of theoretical derivations. Further, as
in the preceding case, this approach is intended to predict only
changes in air quality resulting from changes in emission rates.
3. Mathematical Modeling (or AQSM) Approach. The approach entails
deriving the requisite air quality-emission relationships entirely
from theory. Its intended use is to predict both absolute levels of
and changes in air quality from given emission rate and meteorological
data.
To be usable, all methods of relating air quality to emissions, regardless
of approach, must be validated and evaluated for accuracy. The distinction
between "validation" and "accuracy-evaluation" follows. Validation refers to
the agreement between model-predictions and observations when the input infor-
mation fed into the model is perfectly accurate; thus, validation is the
process of checking the validity of the principle underlying the method.
Accuracy-evaluation refers to the agreement between model-predictions and
observations for a model based on a perfectly sound principle; thus, accuracy-
evaluation is an assessment of the error introduced by inaccuracies of the
input information. Another term often used in connection with model evaluation
is "verification," referring to the agreement between predictions and observa-
tions for the specific case in which the observations used for verification
were taken from the same pool of data used to develop the model. This is the
case, for example, of development and verification of AQSMs from the St. Louis
RAPS data. In the discussion here, verification will be considered to be a
limited form of validation.
Between validation and accuracy-evaluation, the latter appears to be
relatively simpler, especially for the empirical and semi-empirical methods
and for the relatively simple AQSM methods. Thus, useful accuracy evaluations
can be made from estimates of the errors associated with the input information
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and from numerical sensitivity tests to determine the impacts of such errors
upon model-predictions. Unlike accuracy-evaluation, complete and direct
validation of a model is extremely difficult — if at all possible — to accom-
plish for the main reason that the requisite "real world" data — on quality
and emissions — are either not available or not easy to obtain. Thus, for the
empirical and semi-empirical models relating emission changes to air quality
changes, data on such changes either do not exist, or, if they do exist, as
for the Los Angeles basin, they are useful only for verification of a "local-
use" model. For the AQSM methods, intended to relate absolute levels of air
quality to emission rates, validation hinges upon solution of several problems,
one of which is the definition of absolute air quality in terms of commonly
obtained air quality monitoring data. At the present time, these problems in
validating models are considered to be prohibitive by some investigators, but
not insurmountable by others. It is this latter disagreement among investiga-
tors that constitutes the issue to be examined here.
More specifically, the question at issue here is:
• At the present time, are there any air quality simulation models
sufficiently validated/evaluated and appropriate for use in designing
urban oxidant control strategies?
The Environmental Protection Agency has not issued nor does it have plans
for immediate issuance of strategy design guidelines (for oxidant control)
involving use of AQSMs. Furthermore, EPA is conducting an extensive study
(RAPS project) to first verify and subsequently further validate and evaluate
several of the presently available AQSMs. Obviously, therefore, EPA does not
feel that at this time there are AQSMs ready for use. Contrary to this EPA
viewpoint, some investigators have suggested that there is one sufficiently
validated air quality simulation model (Bell Lab). The Bell Lab model was
discussed at the International Conference; however, the more detailed descrip-
tion of the model and justification of the Bell Lab viewpoint are to be found
in a subsequently published journal article (18).
17
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There have been numerous reports, presented at the International Confer-
ence and elsewhere, on the principle, status of validation, and intended
utility of several AQSMs. It is important, however, to make the distinction
between true model applications and model exercises that merely demonstrate
the intended utility of a model. The judgment called for here is whether
there can be true model applications, that is, whether there are models
presently available that can and should be used immediately in designing urban
oxidant control strategies.
THE ISSUE REGARDING THE EVALUATION OF A SMOG CHAMBER METHOD AS A REPLACEMENT
FOR THE APPENDIX-J METHOD.
The subject smog chamber method has been described and discussed in
detail at the International Conference and elsewhere. Questions at issue here
pertain to the merits claimed for the smog chamber method both relative to the
Appendix-J method and in an absolute sense. For urgent reasons, examination
of this issue has already begun in the form of Task Group activity conducted
by EPA and non-EPA experts. Therefore, this issue will not be included in the
analysis effort contemplated here.
THE ISSUE OF OXIDANT/OZONE MEASUREMENT
Recent studies have resulted in some disconcerting evidence regarding the
performances of the various oxidant/ozone measurement methods in existence
(1922). All KI procedures for either measuring ambient pxidant/ozone or for
calibrating oxidant/ozone measurements methods were found to disagree with
each other; the disagreement varied in degree depending on study or analyst.
There was also disagreement between certain KI procedures and the more ozone-
specific chemiluminescence and UV photometry methods. It is, generally,
agreed that part of the disagreement is caused by the usual precision and
accuracy errors associated with the various procedural steps, and part with
the difference in response specificity among the various methods. Thus, all
KI methods show response to ozone as well as to all vapors capable of oxidizing
iodide ions or reducing iodine. Since these vapors and 0 do not all cause
equivalent responses, it follows that the KI measurement reflects not only the
18
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concentrations but also the composition — to the extent that such composition
varies — of the responding vapor mixture. Further, the expected differences
in response specificity are larger between the KI methods and the chemilumi-
nescence and UV methods.
In the face of these differences in precision, accuracy, and response-
specificity among the various oxidant/ozone measurement methods, the obvious
question relevant to this analysis is whether these imperfections in the
analytical method invalidate any component of the oxidant control strategy.
To explore this question, the functional relationship between the analytical
method for oxidant/ozone and the oxidant control strategy, first, needs to be
clarified.
Of the various components of the current oxidant control strategy the
only one linked to the analytical method for oxidant/ozone is the one related
to the calculation of emission control requirements. Such calculation requires
that the following three entities be defined:
• Present air quality (PAQ), i.e., second highest 1-hour oxidant/ozone
in the reference year,
• desired air quality (DAQ), i.e., the NAAQS for oxidant/ozone (0.08
ppm 0 ), and
• a quantitative relationship between air quality and emission rates.
Of these, PAQ and DAQ are obviously the entities specifically linked to
the oxidant/ozone measurement method. The preceding question, therefore, is
now reduced to whether the analytical method imperfections invalidate (a) the
PAQ data, and (b) the NAAQS for oxidant/ozone. Each of these two cases is
examined separately.
To explore the impact of the analytical method imperfections upon the PAQ
data, it might be useful" to break down the impact of such imperfections into
two parts: the impact arising from the usual precision and accuracy errors of
the methods, and the impact arising from the nonspecificity of response. The
19
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precision/accuracy errors vary depending on (a) the method (e.g., KI methods,
chemiluminescence, or UV photometry) and (b) the entity to be measured. To
explain the latter, the magnitude of the precision/accuracy error is greater
when the entity to be measured (i.e., PAQ) is expressed in terms of a single
datum (e.g., second highest value) out of a population of data, than when it
is the population average. Note, however, that the criterion for selecting
the "second highest concentration" or the "average concentration" (or any
other concentration) as the entity to be measured, is not the magnitude of the
analytical error; rather, it is the health effects of oxidant/ozone. EPA has
interpreted the health effects evidence available to mean that oxidant-related
air quality should be defined in terms of a "highest" or "second highest"
rather than "average" oxidant/ozone concentration. Whether this interpretation
of the health effects of oxidants/ozone is correct is outside the scope of
this analysis. Thus, in the light of this discussion, the first specific
question that needs to be answered is:
1. Do the precision/accuracy errors invalidate the Federal reference
method for oxidant/ozone? If yes, what method should be chosen
instead?
The impact upon PAQ data of errors related to the specificity of response
is far more complex than that of the precision/accuracy errors. The main
complication arises from the rational requirement that the method measure that
or those chemical species that have been found to have adverse health effects.
However, since an important part of the health effects evidence is of an
epidemiological nature, those species could not have been specified unequiv-
ocally. This problem was circumvented by devising and using the concept of
"surrogate" species, that is, species believed to represent those with the
adverse effects. EPA initially proposed to promulgate that "oxidants," as
measured by a specified KI method, be used as the surrogate species; in the
final promulgation, "oxidants" measured by a (more ozone-specific) chemilumi-
nescence method was pronounced the surrogate species. Rationally, measurement
of PAQ by the chemiluminescence method should give lower results than by any
KI method. However, there have been reports to the contrary. In the light of
this latter dispute, and of the fact that the intended use of all methods is
20
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to measure surrogate species, the relevant question that must be answered next
is:
2. Do the response-specificity errors invalidate the Federal Reference
Method for oxidant/ozone? If yes, what method should be chosen
instead?
The preceding two paragraphs dealt with the impact of the analytical
method imperfections upon the PAQ data. The remaining discussion will deal
with the impact upon the NAAQS for oxidant/ozone. The first obvious, and
direct question to be asked here is:
3. Do the imperfections of the analytical methods for oxidant/ozone
invalidate the air quality standard for oxidant/ozone?
Following is a proposed answer to this question, and the reviewer judgment
called for is on the correctness or incorrectness of this proposed answer.
The answer to this question, to a large degree, depends on the evidence
and reasoning underlying the development of the air quality standard for
oxidant/ozone. The underlying evidence is known to consist of associations
between adverse effects and concentrations of "oxidants" measured by a variety
of analytical methods. It should be noted that a major part of this associ-
ative evidence is not of a cause-effect nature. This means that the oxidant
species responsible for the adverse effects could not have been unequivocally
specified, which in turn means that the air quality standard did not have to
be defined in terms of one or more specified oxidant species. Thus, the
standard could be defined in terms of surrogate species, that is, in terms of
a "response" given by any "oxidant" measurement method. In conclusion then,
the validity of the qualitative definition of the NAAQS for oxidant/ozone
should not be questioned.
The quantitative part of the (air quality) standard (i.e., the "0.08
ppm") can only be a result of analysis and interpretation of the health
evidence available. Apparently the judgments made by the EPA experts with
21
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respect to the severity of the health effects and to the safety margin required
were such that they justified use of the 0.08-ppm limit as measured by a
specified analytical method (Federal Reference Method). These judgments may
or may not be sound. However, this clearly pertains to another issue, namely
the issue of health justification of the NAAQS-oxidant/ozone, and not to the
issue of oxidant/ozone measurement. In conclusion, again, the imperfections
of the analytical methods do not invalidate the 0.08-ppm part of the oxidant/
ozone standard, or, to put it differently, cannot have much different impact
on the validity of a higher or lower standard.
THE ISSUE OF THE OPTIMUM OXIDANT CONTROL STRATEGY
As discussed in the introduction paragraphs preceding the first six issue
sections, there are several questions or problems that must be resolved if
oxidant control measures are to be developed and applied. Some of these
questions, by virtue of their importance and basic nature, and the considerable
contradictory attention paid to them, have attained an issue status and have
been treated individually in the preceding sections. Resolution of those
issues will definitely and considerably advance the understanding of the
oxidant problem, but will still leave the primary issue of optimum oxidant
control strategy somewhat open. There are still several questions more direct-
ly and specifically addressed to the subject of oxidant control strategy that
need to be given definitive answers. These questions are to be dealt with in
this section.
Departure points in this discussion/analysis will be two facts: The
existence of an oxidant control strategy since 1971, and the generation, since
1971, of considerable new scientific evidence pertaining to the oxidant con-
trol problem. The immediate and obvious question that arises from these facts
is whether the new evidence supports or invalidates, partly or wholly, the
first, existing oxidant control strategy. If the strategy is shown to be
invalidated in some respects, then the next obvious question is what strategy
revisions are dictated or can be justified by the new evidence. To explore
these questions or possibilities, it is necessary that the new scientific
22
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evidence, or, more directly, the changes in understanding brought about by the
new evidence be specified.
The most important change in understanding that has been brought about by
the new evidence concerns the source-receptor relationship, that is, the
geographical or spatial relationship between areas in which emissions are
discharged and the areas where the air quality is impacted by these emissions.
Much of the discussion needed here about this relationship has already been
presented as part of the discussion on the Oxidant Transport issue. The
control strategy implications, however, of the source-receptor relationships,
as now understood, need to be further expanded.
The first implication is that long-range pollutant transport introduces
a link between the urban oxidant problem and the rural oxidant problem. This
means that in many areas, urban emissions and oxidant significantly affect
rural air quality and, conversely, oxidant-carrying rural air upwind from a
city significantly affects the city's air quality. Thus, from a control
standpoint, the urban and rural problems are not entirely disassociated, and
therefore, respective optimum control strategies should not be pursued entire-
ly independent of each other.
A second implication is the one arising from the vertical mixing patterns
observed and associated with radiation and subsidence inversion phenomena.
Such mixing patterns suggest that local emissions may have significant carry-
over effects upon next day's local air quality. This and the previous impli-
cation depict a new picture of the photochemical processes responsibile for a
city's oxidant problem. According to this picture, the local oxidant problem
is the composite of contributions originating from:
(a) local, fresh emissions,
(b) local but previous day's emissions,
(c) extraneous emissions (probably from previous days), and
(d) natural sources.
23
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The third implication relates to the relative roles of the HC and NO
x
emissions in the oxidant problem. The existing oxidant control strategy
formally recognizes only a HC role; no oxidant-related controls are imposed
upon NO emissions. Such roles of the precursors, however, are now thought to
be incorrect quantitatively and, perhaps, qualitatively also. Thus, the
oxidant-to-HC dependence is not independent of the NO factor. Also, and more
importantly, the effects of local HC and NO emission controls on oxidant are
X
expected to vary depending on whether the oxidant results from local fresh
emissions or from previous day's local emissions or from extraneous emissions.
In the light of these implications of the recent scientific findings, the
specific questions that need to be answered here are as follows.
1. Is the qualitative basis of the existing oxidant control strategy
still sound? That is, is hydrocarbon emission control an optimum
approach to urban oxidant reduction?
Because of the link between the urban and the rural oxidant problem, the
answer must be based on considerations of both types of problem. Considera-
tion must also be given to the situation in which local emissions have multi-
day carryover effects upon local oxidant. Finally, consideration should be
given to the relative importances of the anthropogenic and the natural sources.
In essence then, the first question asked here can be reworded as follows:
Considering the four origins of urban oxidant [cases (a) - (d) described
in preceding paragraphs], is control of local (urban) HC emissions
expected to be an effective means to local oxidant reduction?
Relevant evidence consisting of both laboratory and field data has been
reported at the International Conference and elsewhere, and is conflicting.
Thus some field studies showed HC control to have a strong beneficial effect,
others did not show a detectable effect, and others showed effects varying
with attendant NO emission change. Smog chamber studies showed that for the
portion of oxidant formed from the day's local emissions, control of HC is
beneficial except for atmospheres with extremely high — ordinarily not observed
24
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— hydrocarbon-to-NO ratios; for such atmospheres HC control, unless drastic,
will have very little effect. For the portion of oxidant formed through
multiday irradiation of emissions, the evidence is scant and inconclusive by
some investigators but conclusive by others. Those who, feel that the evidence
is conclusive claim that HC control will have small effects upon multiday,
irradiated air masses, relative to the effect upon single-day, irradiated air.
Control of HC emissions upwind, again, has little effect by some investigators,
undetermined effect by others. While it is certain that the effectiveness of
the HC control approach is different for different localities, the judgment
called for here is whether this approach should be retained or be replaced by
another approach.
2. Insofar as the urban oxidant problem is concerned, is NO emission
control imperative? desirable? tolerable? undesirable? intolerable?
Again, for the questions to be answered properly, consideration must be
given to the various sources of urban oxidant, namely, pollutant transport,
local/fresh emissions, local/aged emissions, and natural sources. Evidence
from field studies is conflicting in that it shows higher NO emission rates
to be associated with lower oxidant concentrations in some cases, and no such
association in others. Smog chamber data exist only for the situation in
which the urban oxidant forms from the day's local emissions. For this
situation, NO control has varying effects depending on the hydrocarbon-to-NO
X X
ratio of the reacting emissions. The effect of control of the upwind emissions
of NO also may be in dispute. Again, as with the preceding question, the
judgment called for here is whether the NO emission factor should continue to
be nearly ignored — as is the case with the existing strategy — or should be
considered, and how.
The preceding paragraphs dealt with the qualitative bases of an optimum
oxidant control strategy, that is, with the questions pertaining to the direc-
tional impacts of the HC and NO emission controls. The questions that need
to be defined next deal with the quantitative bases of an optimum strategy,
that is, with the quantitative impacts of controls. Such quantitative bases
consist of the following two components:
25
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• The quantitative relationship between ambient oxidant concentrations
and emission rates, and
• The definitive relationship between source area and receptor area,
meaning the definition of the geographical area where the required
control — as calculated from the oxidant-emission relationship —
must be applied to solve the oxidant problem observed in a given
locality.
The quantitative relationship between oxidant and emissions is the
subject of the issue on the replacement of the Appendix-J method, and will not
be treated here. Nevertheless, it might be helpful to mention here that the
smog chamber method, proposed as a replacement of the Appendix-J method,
provides a cause-effect relationship between oxidant and precursors and,
unlike the Appendix-J method, does not take any specific source-receptor
relationship for granted. Thus the smog chamber method does not prescribe, as
the Appendix-J method does, that control be confined within the urban area
where the oxidant problem was observed.
Assuming that the replacement of the Appendix-J method will be a method
based on a cause-effect relationship between oxidant and emissions, it will be
necessary that "cause" and "effect" be identified, respectively, with a "source
area" and a corresponding "receptor area," the latter being the area where the
air quality is impacted by the source area.
Defining the source-receptor relationship consistent with the cause-
effect nature can be approached, in theory at least, in several different
ways. By one, first approach, "effect" is identified with the maximum oxidant
observed in the "receptor" area, and "cause" is identified with the emissions
from all sources — local and upwind — that impact the receptor area. This
approach requires that all source areas impacting the receptor area be identi-
fied, a requirement which is extremely difficult — if at all possible — to
fulfill.
By the second approach, "effect" is identified with the fraction of the
26
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observed maximum oxidant concentration attributable to the local emissions,
and "cause" is identified with the local emissions. This approach has at
least two problems:
• The determination of the oxidant fraction associated with the local
emissions, and
• The requirement that another source-receptor relationship be defined
for the fraction of oxidant associated with the extraneous, upwind
emissions.
The first problem is not an insolvable one: e.g., a rough estimate of the
oxidant fractions associated with the local and the extraneous emissions could
be obtained from oxidant measurements upwind and downwind from the receptor
area. The second problem, however, is extremely difficult — if at all possi-
ble — to solve.
A third approach could- be conceived as a simplified compromise between
the two preceding ones. By this third approach, "effect'1 is identified with
the maximum oxidant concentration observed in the receptor area, and "cause"
is identified with the local emissions. The assumption is made here that the
local emissions are the sole and whole cause of the oxidant problem. This
assumption, it is well recognized, is not valid in oxidant transport situations
in which the local emissions cause only part of the problem. Nevertheless,
the assumption is justified on grounds that in the very same (oxidant trans-
port) situations, the local emissions almost surely contribute to or cause
additional problems to downwind area. It might appear at first glance that
application of controls calculated by this approach upon the receptor area as
well as upon the upwind areas will result in over-control. In actuality,
however, this will not necessarily be the case because the sum total of the
"local" and "transported-in" contributions to oxidant may exceed the 0.08-ppm
standard even though the individual contributions are each less than 0.08 ppm.
Finally, a fourth approach could be conceived as a more-stringent-control
version of the second approach. By the fourth approach, "effect" is identified
27
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with the fraction of the maximum oxidant concentrations attributable to the
local emissions. However, calculating control requirements so as to reduce a
fraction of the oxidant down to 0.08 ppm, obviously, will not solve the oxidant
problem. To solve the problem, control requirements should be calculated so
as to reduce the "local" oxidant fraction below 0.08 ppm, that is, to a level
such that the total oxidant will be, if possible, at or below 0.08 ppm. Thus,
by the fourth approach, the oxidant contribution from the extraneous (upwind)
sources is partly or wholly offset by imposing increased control of local
emissions.
The preceding analysis identifies four conceivable approaches to formula-
ting an optimum strategy for oxidant control. Obviously, there may be others.
The question to be asked here is:
Which of these four, or any other, approaches is the one to be recommended?
28
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REFERENCES
1. Federal Register, 36 (158):15489, August 14, 1971.
2. International Conference on Photochemical Oxidant Pollution and Its
Control, Proceedings. EPA-600/3-77-001 a & b. Environmental Protection
Agency, Research Triangle Park, North Carolina, 1977. 2 Volumes.
3. Clean Air Act (42 U.S.C. 1857 et seq.) including "Clean Air Amendments of
1970"-P.L. 91-604 (Dec. 31, 1970).
4. Dimitriades, B., and S.B. Joshi. Application of Reactivity Criteria in
Oxidant-Related Emission Control in the USA. International Conference on
Photochemical Oxidant Pollution and Its Control, Proceedings. 2:705-711.
EPA-600/3-77-001b. Environmental Protection Agency, Research Triangle
Park, North Carolina, 1977.
5. Chang, T.Y., and B. Weinstock. Net Ozone Formation in Rural Atmospheres.
International Conference on Photochemical Oxidant Pollution and Its
Control, Proceedings. 1:451-465. EPA-600/3-77-001a. Environmental
Protection Agency, Research Triangle Park, North Carolina, 1977.
6. Holderman, J.D., and E.A. Lezberg. NASA Global Atmospheric Sampling Pro-
gram (GASP). Data Report for Tape VL 0001. NASA Technical Memorandum
NASA TM x-71905, NASA, Lewis Research Center, Cleveland, Ohio, 1976.
7. Hathorn, J.W., III, and H.M. Walker. A "Texas Size" Ozone Episode Tracked
to Its Source. International Conference on Photochemical Oxidant Pollu-
tion and Its Control, Proceedings. 1:353-380. EPA-600/3-77-001a.
Environmental Protection Agency, Research Triangle Park, North Carolina,
1977.
29
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8. Rasmussen, R.A. What Do the Hydrocarbons from Trees Contribute to Air
Pollution? J. Air Poll. Control Assoc., 22:537-543, 1972.
9. Martinez, E.L., and E.L. Meyer, Jr. Urban-Nonurban Ozone Gradients and
Their Significance. Ozone/Oxidants — Interactions with the Total Environ-
ment. APCA Specialty Conference (Southwest Section), Proceedings.
p. 221-233. Air Pollution Control Association, Pittsburgh, Pennsylvania,
1976.
10. Rasmussen, R. Progress Report from Washington State University to
Environmental Protection Agency on Research Grant No. 800670, "Aerosol
Formation from Naturally Emitted Hydrocarbons." 1974.
11. Grimsrud, E.P., H.H. Westberg, and R.A. Rasmussen. Atmospheric Reac-
tivity of Monoterpene Hydrocarbons, NO Photooxidation and Ozonolysis.
X
Proceedings of the Symposium on Chemical Kinetics Data for the Upper and
Lower Atmosphere. Int. J. Chem. Kinet. Symp. No. 1. p. 183-195. John
Wiley & Sons, New York, 1975.
12. Coffey, P.E., and W.N. Stasiuk. Evidence of Atmospheric Transport of
Ozone into Urban Areas. Environ. Sci. Technol. 9(1):59-62, 1975.
13. Research Triangle Institute. Investigation of Rural Oxidant Levels as
Related to Urban Hydrocarbon Control Strategies. EPA-450/3-75-036.
Environmental Protection Agency, Research Triangle Park, North Carolina,
1975.
14. Cleveland, W.S., B. Kleiner, J.E. McRae, and R.E. Pasceri. The Analysis
of Ground-Level Ozone from New Jersey, New York, Connecticut, and Massa-
chusetts: Data Quality Assessment and Temporal and Geographical Proper-
ties. International Conference on Photochemical Oxidant Pollution and
Its Control, Proceedings. 1:185-196. EPA-600/3-77-001a. Environmental
Protection Agency, Research Triangle Park, North Carolina, 1977.
30
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15. Research Triangle Institute. Ambient Monitoring Aloft of Ozone and Pre-
cursors in the Vicinity and Downwind of a Major City. Interim Report to
U.S. EPA. RTI Project No. 43U-1272. Research Triangle Institute,
Research Triangle Park, North Carolina, 1976.
16. Bufalini, J.J., T.A. Walter, and M.M. Bufalini. Ozone Formation Poten-
tials of Organic Compounds. Environ. Sci. Technol., 10(9):908-912, 1976.
17. Vukovich, P.M., W.D. Bach, Jr., B.W. Crissman, and W.J. King. On the
Relationship Between High Ozone in the Rural Boundary Layer and High
Pressure Systems. (accepted for publication in Environ. Sci. Technol.)
1977.
18. Graedel, T.E., L.A. Farrow, and T.A. Weber. Kinetic Studies of the
Photochemistry of the Urban Troposphere. Atmospheric Environment.
10(12): 1095-1116, 1976.
19. California Air Resources Board. Comparison of Oxidant Calibration Proce-
dures; a Report of the Ad Hoc Oxidant Measurement Committee of the Cali-
fornia Air Resources Board, 75-4-4. Sacramento, California, 1974.
20. Hodgeson, J.A. Ozone: Sampling, Analysis, and Method Evaluation. 15th
Conference on Methods in Air Pollution Studies. January 14-15, 1976.
Long Beach State University, Long Beach, California.
21. Neal, R., R. Severs, L. Wenzel, and K. MacKenzie. Simultaneous Chemi-
luminescent Ozone and KI Oxidant Measurements in Houston, Texas, 1975.
Ozone/Oxidants — Interactions with the Total Environment. APCA Speciality
Conference (Southwest Section), Proceedings, p. 180-188. Air Pollution
Control Association, Pittsburgh, Pennsylvania, 1976.
22. Paur, R.J., R.E. Baumgardner, W.A. McClenney, R.K. Stevens. Status of
Method for the Calibration of Ozone Monitors. Extended Abstracts,
p. 185-188. 171st National ACS Meeting, Division of Environmental Chem-
istry, April, 1976. American Chemical Society, 1976.
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EPA-600/3-77-113 j
I'"'. •'»•.,.J SIJ3T' "'.r "~
INTERNATIONAL CONFERENCE ON OXIDANTS, 1976 -
ANALYSIS OF EVIDENCE AND VIEWPOINTS
_?a-EL_I. Def.initi.on of_Key Issues.
•" -L r"ORiJ' " """ "" "
B. Dimitriades and A.P. Altshuller
TECHNICAL REPORT DATA
i; 'i.i^n -to, • 111 the .'•. ,/ i-hi-iurv i,-'Hf>tctini;!
3. RECIPIENT'S ACCESSIOONO.
5. REPORT DATE
October 1977
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
9. RERFORVlNij ORGANISATION MAME AND ADDRESS
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
12 SPONSORING AiVENCY NAME AND ADDRESS
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
- RTF, NC
10. PROGRAM ELEMENT NO.
1AA603 AJ-13 (FY-76)
11. CONTRACT/GRANT NO.
13. TYPE OF REPORT AND PERIOD COVERED
In-house
14. SPONSORING AGENCY CODE
EPA/600/09
15. SUPPLEMENTARY NOTES
This is Part I of an eight part series.
16. ABSTRACT
In recognition of the important and somewhat controversial nature of the
oxidant control problem, the U.S. Environmental Protection Agency (EPA)
organized and conducted a 5-day International Conference in September 1976.
The more than one hundred presentations and discussions at the Conference
revealed the existence of several issues and prompted the EPA to sponsor a
follow-up review/analysis effort. The follow-up effort was designed to review
carefully and impartially, to analyze relevant evidence and viewpoints reported
at the International Conference (and elsewhere), and to attempt to resolve
some of the oxidant-related scientific issues. The review/analysis was con-
ducted by experts (who did not work for the EPA or for industry) of widely
recognized competence and experience in the area of photochemical pollution
occurrence and control.
Part I of the overall effort is an explanatory analysis of the problem
and definition of key issues, as viewed within the research component of the
EPA. Parts II through VIII are written by expert reviewers offering either
resolutions of issues or recommendations for additional research needed to
achieve such resolution.
17.
a.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
* Air pollution
* Ozone
b. IDENTIFIERS/OPEN ENDED TERMS C. COSATI Held/Group
13B
07B
loT^'P'i' ON ~>r : FEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report!
UNCLASSIFIED
20. S!.:CURrrY CLASS TTiii!paje)
UNCLASSIFIED
21. NO. OF PAGES
_ .^B.
22 PRICE
E?,
32
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