Report on Air Quality Criteria for Hydrocarbons (AP-64)
and Air Quality Criteria for Photochemical Oxidants (AP-63)
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Report on Air Quality Criteria for Hydrocarbons (AP-64)
and Air Quality Criteria for Photochemical Oxidants (AP-63)
A
Report to the
United States
Environmental Protection Agency
by the
National Air Quality Criteria Advisory Committee
of the
Science Advisory Board
Science Advisory Board
U.S. Environmental Protection Agency
June 1976
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EPA NOTICE
This report has been written as a part of the activities of the
Agency Science Advisory Board, a public advisory grouD providing extra-
mural scientifici~formation to the Administrator and other officials
of the Environmental Protection Agencv.
The Board is structured to
provide a balanced expert assessment of scientific matters related to
problems facing the Agency.
This report has not been reviewed for
approval by the Agency and hence its contents do not reDresent the views
and policies of the Environmental Protection Agency.
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Repor_t on "Air Ouality Criteria for Hvdrocarhons". (AP-fi4)
and "Air Quality Criteria for Photochemical Oxidants" (AP-63)
Summary Comments
The criteria documents for photochemical oxidants and for hydro-
carbons should be combined into one, while keeping the nitrogen oxides
criteria document separate.
The material in the variou~ chapters should
be suitably integrated.
However, the toxic effects of hydrocarbons such
as benzene, and some of the oxidized hydrocarbons such as epoxides, and
other aspects of the hydrocarbon effects which are not directly related
to their role in photochemical oxidant production should be addressed in
a separate section in the combined document.
The updated and combined document should reflect the significant
increase in our knowledge of the importance of atmospheric gas to particle
conversion processes in ambient air.
Jluring the last five to six years an increasing body of data has been
accumulated on secondary trace contaminants associated with photochemical
oxidants.
\
Recently it. has been more widely realized that some of these
might cause adverse health effects.
Consequently, this area should be
given significant attention in the new comhined document.
In the combined document a broader definition of organics should be
used and "hydrocarbons" treated as a subset of the total organic
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atmospheric in~entory.
Oth'.'1: clar-:: ,.~
f compound,s \'!uuld include
oxygenated organics such a', .,ldehy,.!e.;;
halngcna te,,:
'-'yg3.nics,
etc.
In reviewing the experiment ~ '",ork dealing with the "Toxicological
Appraisal of PhotQchemical Oxidants," over 100 publications have
appeared since 197Q that are directly related to ozone.
Mos t of the
investigations are additional animal experiments that are relatively
short-term, and thus a gap remains in our knowledge of the effectS of
long term, low level exposures.
Another area of intensive research
which must be cited and evaluated is that concerned witll the biochemical
assessment of changes in organelles and macromolecules subjected to
oxidant exposure.
Very important and significant has been the great
emphasis on the pulmonary alveolar macrophage which is critical to
pulmonary defense against inhaled contaminants.
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Report on "Air Quality Criteria for Hydrocarbons (AP-fi4)
Com~ents on Specific Chapters
Chapter 1
Introduction
This chapter will have to be updated in line with the rest of the
document.
Chapter 2
Nature, Sources~ and Principles of Control of Atmospheric
Hydrocarbon
The section on expected photooxidation products should be updated
with respect to current knowledge of concentrations and distribution of
organics in the atmoaphere and with respect to current knowledge of
atmospheric photochemistry.
Emphasis must be not only on aldehydes and
PANS as is done but also on peroxides, organic acids, epoxides, organic
aerosols, and products of halocarbon and solvent photooxidations, etc.
Smog chamber data of the past seven years should be incorporated,
as should the results of major atmospheric studies such as LARPP, ACHEX,
RAPS, etc.*
Thus, Table 2-1 (ambient hydrocarbons) and_Table 2-2
(exhaus~ and irradiation data) should be replaced by more re~ent data.
'~LARPP
ACHEX
RAMS
RAPS
- Los Angeles Reactive Pollutants Program
- Aerosol Characterization Experiments
- Regional Air Monitoring Study
- Regional Air Pollution Study
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Hydrocarbon emissions from natural sources should be updated' in
terms of appropriate studies of the past five years.
Tables 2-6
(Estimates of Hydrocarbon F.missions by Source Category) and 2-7 (Summary
of Hydrocarbon Emissions) should be updated.
Recent data concerning hydrocarbon emissions from catalyst-equipped
vs. pre-catalyst automobiles should be incorporated.
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Chapter 3
Atmospheric Levels of Hydrocarbons and Their Related Products
Conunents on Chapter 2 ,(Nature, Source, and Principles of Control)
apply here also.
Tables 3-1 (Some Hydrocarbons Identified in Ambient Air),
3-2 (Average Atmospheric Light Hydrocarbon Concentrations), and 3-3 (Mean
of Daily Maximum Hourly Average Total Hydrocarbon Concentrations) should'
be expanded to include current knowledge of ambient organics.
Data from the LARPP, ACHEX, RAMS, and RAPS studies on diurnal and
seasonal variatio~s in pollutant concentrations should be incorporated.
The section on secondary contaminants must be greatly expanded to
include classes of products cited above and the greatly expanded 'body of
data concerning organic aerosois (Section 3.C.2.).
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Chapter 4
General Standardization and Analysis Methods
Sections on calibration techniques and methods of analysis should be
expanded where necessary and brought up-to-date.
For example Section
4.D.3. on spectrometric methods for hydrocarbons should discuss both
routine air monitoring analysis and specialized laboratory experiments.
This section should also discuss UV methods of analysis for hydrocarbons
which are totally omitted from the document.
Section 4.E on analysis of gaseous aldehydes and ketones should be
extended to organic acids, esters, epoxides, etc.
Section 4.6 on aerosol measurements must be extensively expanded and
updated in light of advances of the past seven years.
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Chapter 5
Relationship of Atmospheric Hydrocarbons to Photochemical
Air Pollution Levels
The data base, premises and conclusions in this chapter should be
completely re-examined within the context of the extensive smog chamber,
atmospheric and modeling studies of the past seven years which deal with
the relationshi~ of oxidants and oxidant precursors.
Chapter 6
Effects of Hydrocarbons and Certain Aldehydes on Vegetation
Additional literature concerning the effects of ethylene and related
hydrocarbons on vegetation has accumulated since 1969 and should be
incorporated.
A complete review of synergistic, antagonistic and additive effects
on vegetation of oxidant and hydrocarbon air pollutants with other con-
taminants in the atmosphere should be incorporated in the combined
criteria document for photochemical oxidants and hydrocarbons.
For other
points concerning plant effects see the detailed comments on the Air
Quality Criteria for Photochemical Oxidants (AP-63).
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Chapter 7
Toxicological Appraisal of Hydrocarbons and Aldehydes
Whereas this chapter of the criteria document for hydrocarbons was
confined to a toxicological appraisal of hydrocarbons and aldehydes, the
revised document should treat the toxicity of minor but potentially
harmful trace contaminants such as organic acids, epoxides, amines.
Chapter 8
Summary and Conclusions
Based on updated, expanded and thoroughly documented revisions of
the preceeding chapters, a more detailed, specific, and rigorous summary
and conclusions chapter should emerge.
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Report on "Air Quality Criteria for Photochemical Oxidants (AP-63)
Comments on Speciffc Chapters
Chapter 1
Introduction
This will have to be updated in line with the rest of the document.
Chapter 2
Physical and Chemical Nature of Photochemical Oxidants
The role of aldehydes and nitrous acid in photochemical smog should
be discussed.
Values of
uv and
IR should be included in Table 2-1 (Physical
Properties of Ozone) for specified slit widths.
The discussion of the chemistry of hydrocarbon photooxidation should
be substantially updated to include the key role played by the hydroxyl
radical (OH) and the hydroperoxyl radical (H02).
I
The hydrocarbon reactivity section should be expanded and updated to
include recent research and actions taken by control agencies in this
important area.
The substantial body of new and better defined smog chamber data
should be presented in detail.
Nitrogen and carbon material balances should be discussed in light of
the application of more recent and powerful analytical techniques.
The future research areas given in the original documents should be
updated with respect to the current state-of-the-art, since they provide
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a useful guide. to the researcher.
For example, comments in the ortginal
document were very much "on the mark" when they pointed to the necessity
of obtaining rate constant data for OH reactions with various hydrocarbons.
It appears that there is a gap in coverage between the contents of
Chapter 2 and 3.
Chapter 2 deals with the physical and chemical nature of
photochemical oxidants, while Chapter 3 deals with atmospheric photochemical
oxidant concentrations.
Either Chapter 2 should have its title changed to
reflect chemical and physical transformations, or a new, chapter should be
created to address this point.
In either case, a section should be
devoted to the role of computer modeling in understanding the chemistry of
photochemical smog formation.
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Chapter 3
Atmospheric Photochemical Oxidant Concentrations
Again, this chapter needs complete rewriting in terms of knowledge
gained from recent 3-dimensional measurements of pollutant profiles and
the LARPP* data for the L. A. Basin.
It could also be useful to include
a discussion of computer models for transport of air parcels.
Results should be presented which show the trends in air quality data
for a number of years based on standardized measurement techniques.
The impor~anc~ of factoring out meteorology from the above mentioned
air quality trends should be specifically addressed.
*LARPP - Los Angeles Reactive Pollutants Program
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Chapter 4
Natural Sources of Ozone
This chapter will also require a complete rewriting, and the various
types of geographical location affected by elevated ozone levels should
be addressed, e~g., metropolitan, suburban, rural, wilderness, etc.
. The role of natural hydrocarbons in generating "elevated" ozone con-
cent rat ions should be described in detail.
Evidence for the injection of
stratospheric ozone into specific areas should be discussed.
Chapter 5
Measurement of Oxidants, Ozone, and Peroxyacetyl Nitrate
in Ambient Air
This chapter is a critical one in discussing control of photochemical.
oxidants and needs complete rewriting.
A detailed discussion should be
given of the various techniques for ozone measurement and all the precautions
which need to be taken into account to get accurate and reproducible data.
Chapter 6
Effects of Photochemical Oxidants on Vegetation and
Certain Microorganisms
Separate treatment should be given to the effects on plants and on
microorganisms.
This chapter is particularly important in view of the reduction in
crop yields by air pollutants.
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First, the information on acute and chronic dose responses of agri-
cultural plants to specific pollutants was poorly developed; the response
function most desired is something like seed or fruit yield, but mostly
only percent leaf .area injured or some similar index was used.
It is
usually not possible to relate such indexes to economic equivalents.
Since 1970, a substantial amount of new data on dose response has appeared
in the literature or will soon be published.
Some of these data are from
field studies with open top chambers and response units are related to
growth or yield.
This new information is in the new National Academy of
Sciences (NAS) document on photochemical oxidants, and it will be
possible to do a better job of presenting more appropriate dose-injury
models in the new criteria document.
The second kind of deficiency which the NAS panel on photochemical
oxidants recognized was a need for information on the effects of chronic
pollutant (ozone) injury to ecosystems.
The important point here is that
an extension beyond economics immediately becomes apparent.
For example,
what is the value of limiting damage to forest ecosystems where other
than immediate economic gains are used as value criteria?
What benefits
to the health and welfare of this generation (and succeeding generations)
can be gained by conserving the most attractive features of the conifer
fOFest ecosystems of the San Bernardino Mountains?
Can the expected cost
of controlling oxidant precursors be justified because the high quality
of a recreation area visited by 6-7 million people per year is being
diminished for this generation and perhaps denied to future generations?
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Chapter 7
"The Effect of Ozone on Materials
Again, this chapter should be updated.
Chapter 8
Toxicological Appraisal of Yhotochemical Oxidants
This req~ires substantial updat~ng to include the data accumulated
in the last five to six years.
Among those issues Hhich should be
addressed are the synergistic effects of 03 and S02.
The effect of
standardizati6n "in ozone calibration procedures should be treated.
The effects of the producis of photooxidation of NOx' HC, S02 (e.g.,
organic aerosols, HN03' HONO, N03' HCOOH, epoxides, etc.) should be
described in depth.
Chapt~r 9
Epidemiological Appaisal of Photochemical Oxidants
This chapter should be updated and should reflect results in recent
studies such as CHESS (Community Health and Environmental Surveillance
System).
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Significant Uncertainties and Information Needs
Some of the areas related to photochemical oxidants in which there
is a significant lack of information are, briefly, as follows.
More data should be accumulated on the health effects of both
gaseous and particulate trace pollutants.
Tests should be
~onducted concerning the mutagenic and carcinogenic properties
of these compounds.
More work needs to be carried out to try to quantify the
health effects of continued exposure to levels of ozone in the
O.1-O.Z5ppm range, NOZ, nitrates and sulfates.
A contiriued search for trace pollutants in real and simulated
atmospheres using the most recent and powerful techniques.
This
search should cover both gaseous and particulate pollutants.
Much better emission inventorieg for pollutants, particularly
HC and NOx should be obtained.
Atmospheric measurements of
aldehydes are particularly urgently required.
~-Jork should
continue on the elucidation of the photooxidation of SOZ in
the presence of HC in real and simulated atmospheres.
~ile much has been accomplished in understanding of ozone-olefin
reactions, substantial research is still required to further
elucidate the mechanisms under varying conditions and in the
presence of SOZ'
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Thephotooxidation of aromat1c compounds is poorly understood
and a detailed study of the kinetics and mechanism of these
systems should be carried out in smog chamber studies.
This
should include a study of particulate organics from these
reactions, particularly important for areas of peripheral to
urban centers.
While much kinetic data has been accumulated on OH in the last
six years, little information is available on the products of
OH reactions, particularly with olefins and aromatics.
While H02 is expected to be present in polluted atmospheres at
significant concentrations, little is known about the kinetics
or mechanisms of its reactions with organic compounds.
The
situation is even poorer in the case of R02.
The atmospheric conversion of gaseous pollutants to particulates
has not yet been well simulated in the laboratory.
Until it is,
the understanding of this process will not be complete.
Investigation of the relative importance of different hydrocarbon
classes (olefins, paraffins, aromatics) as organic aerosol
precursors.
More data on gas to aerosol conversion rates (in ambient atmospheres)
for
HC ..).
Particulate organics
S02 -}.S04 =
NOx ~ N03 - (how is NH3 involved?)
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More work on inorganic aerosol formation (S04=, N03-) as a
result of HON02 formation and S02 oxidation in photochemical
HC-NOx~S02 systems.
Two areas requiring further information which have not been
studied since the publication of the photochemical oxidants
document are (a) the possibility that ozone has an influence
on fertility and exerts a transplacental effect, and (b) the
potential for induction of mutations, a subject which should
be studied in detail.
Most important also is the paucity of experiments to determine
whether or not oxidants are actually carcinogenic and/or produce
premature aging and life shortening.
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Some of the areas related to oxidant effects on plants in which
there is a signifjcant lack"of information include the following.
The effect of relative humidity and plant responses to ozone requires
study.
This environmental variable has been cited as the parameter
responsible for the difference in plant injury thresholds observed in
the Eastern and Western regions of the United States.
Substantial effort is needed to determine plant responses to ozone
other than foliar injury.
This is especially true of chronic effects
over long time periods.
Economic assessments of reductions in agri-
cultural productivity due to ozone will never be satisfactory unless
accuracy is improved and methodology standardized.
The current data on the distribution and intensity of ambient PAN con-
,
centrations is quite insufficient.
PAN symptoms have been identified
on plants over much of the nation, yet no network of monitors exists.
It is the second most common phytotoxic oxidant in terms of agricul-
turel yet has the smallest scientific data base and the economic
effects of PAN-related agricultural losses currently cannot be esti-
mated.
The phytotoxicity of combinations of PAN and other common gaseous
pollutants should be explored in depth.
Aside from a few laboratory
fumigations with ozone, there are practically no data concerning the
phytotoxic responses of combinations of Pfu~-SOz, PAN-NOZ or PAN-
ethylene.
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