Report on Air Quality Criteria for
Oxides (AP-50) and Revised Chapter
Air Quality Criteria for Sulfur Ox
Effects of Sulfur Oxides in the At
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Report on Air Quality Criteria for Sulfur Oxides (AP-50)
and Revised Chapter 5 for Air Quality Criteria for Sulfur
Oxides, Effects of Sulfur Oxides in the Atmosphere on
Vegetation (EPA-R3-73-030)
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
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EPA NOTICE
This report has been written as part of the activities of the
Agency Science Advisory Board, a public advisory group providing
extramural scientific information to the Administrator and other
officials of the Environmental Projection Agency. 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
represent the views and policies of the Environmental Protection
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Report on "Air Quality Criteria for Sulfur Oxides" (AP-50) and
Revised Chapter 5, Effects of Sulfur Oxides in the Atmosphere
on Vegetation (EPA-R3-030)
Summary Comments
It is the Committee's considered opinion that the Sulfur Oxides
criteria document is in serious need of revision and that such a revision
is not only desirable, but necessary.
It is vital that sulfur dioxide and particulate matter be dealt with
in a manner which takes full account of their simultaneous presence in
the ambient air. There is ample evidence from atmospheric chemistry,
toxicology, and epidemiology to support this thesis. On the other hand,
certain criteria may apply to particulate matter which are totally
unrelated to interaction with sulfur dioxide. As examples one might cite
the known carcinogenic potential of certain components of Total Suspended
Particulates (TSP) or the fact that formaldehyde and other gaseous
pollutants can also associate with particulate material. It is vital
that these aspects receive proper recognition.
The Committee recommends that the Sulfur Oxides criteria document be
revised and reissued as Air Quality Criteria for Sulfur Oxides and
Associated Particulates and that the criteria document for Particulate
Matter be revised and reissued as such.
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Comments on Specific Chapters
Chapter 1 - Physical and Chemical Properties and the Atmospheric
Reactions of the Oxides of Sulfur
One omission from this chapter is a discussion of the biological
sources of sulfur compounds in the atmosphere and their subsequent
oxidation. The initial portions dealing with the physical and chemical
properties of sulfur dioxide and sulfates seem fairly straightforward.
Our knowledge of the theory of conversion of sulfur dioxide to sulfate
under various conditions is unfortunately still limited, but this
section should be updated.
The conversion of sulfur dioxide to sulfate is obviously of major
importance. The rate at which this takes place in the free atmosphere
cannot be predicted by extrapolations of laboratory measurements. The
reason is that the atmosphere has a vast variety of trace contaminants
that have an influence on the rate of oxidation of sulfur dioxide and
the rate in the gaseous form is slower than the rate when in a solution
with trace metals (i.e., in a droplet). There have been a number of
/
recent elaborate studies in which a downwind network observes the
chemical changes as the polluted air passes through it (for example,
Dana et al, J.G.R., 80, 4119-429, 1975). There have also been studies
related to formation and growth of sulfate particles. There is need
o
to update and summarize the recent findings.
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The recent work of Hansen and Eatough at Brigham Young University
indicating that sulfur dioxide can form stable sulfite complexes with
certain metals such as copper and ferric iron should be mentioned in
connection with the potential atmospheric reactions of sulfur dioxide.
An important point to emphasize is the growing significance of
regional air pollution, and here the continued "aging" of the sulfur
dioxide-sulfate mixture needs to be considered. This is hardly touched
on here, though it is an issue in the entire eastern United States and
in most parts of Europe — in fact, the regional burden may have an
overall practical significance that is as great as the local effects
downwind from major sources, since more people and activities are affected.
The recent SAPRAC (Statewide Air Pollution Research Center, University
of California) Study in the Los Angeles Basin, the EPA St. Louis Study
and others should be discussed.
Because the atmospheric reactions of the sulfur oxides have
considerable bearing on their potential irritant effects, that point
should be indicated here and cross referenced to the later chapter
(Chapter 6) concerned with toxicology. Neither atmospheric chemistry
nor toxicology exists in a vacuum. As far as possible, the point of a
criteria document should be to put it all together and correlate
information from the several disciplines difficult though this may be.
Anyone who reads Chapter 1 should come away with the feeling for how
important these atmospheric reactions are and why they are so important.
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The discussion of effects of sulfur oxides on light transmission
in the atmosphere seems to have more emphasis than is warranted. The
main points could be made more succinctly and the interested reader
referred to the literature for details. There is recent work, such as
that of Charlson ejt ai, which will update the subject.
The alleged good correlation between SC>2 and visibility as determined
by sulfate particles needs clarification. Presumably this would be true
in a given location under similar weather conditions, but as the sample
ages, more and more of the 502 will convert to sulfate, so this cannot be
generalized as is done here (Figure 1-5) without any qualifying remarks.
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Chapter 2 - Sources and Methods of Measurement of Sulfur Oxides in
the Atmosphere
This chapter should be separated into two chapters, one of which
discusses the sources of sulfur pollution and the other of which
discusses the methods of measurement and characterization.
One deficiency here is the virtual absence of any mention of natural
sources of sulfur oxides. One should view the manmade contributions in
the light .of the natural background. Natural sources are currently
about twice as large on a global basis as the anthropogenic ones
(Kellogg et al., Science 175:587-596, 1972). The forms in which the
natural sulfur is added (HoS, CS2, (CH^^S etc.) is also of interest and
there are some interactions between human acitvity and the biological
sources as when sewage enhances the production of sulfurous gases from
rivers, lakes, and estuaries.
Section B - Sources of Atmospheric Sulfur Oxides
Contamination of the atmosphere by sulfur dioxide is a problem common
to many densely populated urban areas. In such cases, low level sources
which are dispersed throughout the area are usually the emitters of
major sources. However, when the concern is secondary products of
sulfur dioxide, in particular, sulfuric acid and acid sulfates, then
emissions by point sources become an important consideration. The role
played by emissions from point sources at elevated heights as precursors
of these particulate pollutants should be discussed in considerable detail.
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Therefore, categorizing sources strictly "from the viewpoint of their
annual production" is misleading when presented without qualification.
Summaries of emissions of sulfur dioxide by source types for major
cities such as New York and Chicago would be informative. There should
also be included a discussion of the effect of control laws on sulfur
dioxide emissions since the data presented in Table 2-1. Again,
a breakout of data for urban areas should prove interesting.
With respect to measurement methods, many new advances have been
made since the publication of the criteria document. A 1973 paper by
Hollowell e_t al., (Anal. Chem. 45:63A-72A) summarizes current instrumentation
for continuous monitoring of S02- A more recent Analytical Chemistry
update may be available. The 1974 NIOSH criteria document on SC^ has a
brief summary of environmental monitoring methods. Lodgson and Carter
(Env. Sci. Technol. j):1172-1174, 1975) have compared manual and automated
methods for SCv in manually impinged 24 hour-ambient air samples. The
activities of ASTM's Project Threshold in collaboratively testing ASTM
Method D2914 for SC>2 also deserve mention. This study established the
sensitivity, accuracy, and precision of the method. (Foster and Beatty,
Report to ASTM from Battelle, Columbus Lab., September 21, 1973).
Section C - Measurement of Gaseous Sulfur Dioxide Concentrations
1. Sampling Techniques
This section needs expansion. More specific criteria should be
presented for the design and operation of sampling probes and manifolds.
The statement in the last sentence that continuous monitoring is
necessary to show diurnal changes is not exactly correct. Even when data
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from continuous monitors are used to show diurnal variations, they
are most often converted to hourly averages. The same data can be
obtained by intermittent sampling over 1-hour periods.
2. Colorimetric Method
Probably the most important addition to this Chapter will be
a discussion about the stability of West-Gaeke samples on standing
at different temperatures. For field monitoring use of the West-Gaeke
method leaves much to be desired when the operation involves, as it
often does, transporting or mailing of solutions to a central laboratory
for analysis. A detailed analysis and discussion of these problems must
be added to the criteria document's treatment of the official reference
method.
3. Conductometric Methods
These methods are non-specific and not very useful at low
concentrations whenever any other potentially ionic species are present.
The caveat that "one must take special precautions to eliminate other
pollutants which could affect the conductivity of the solution" is
misleading because there often is no feasible manner in which this can
be accomplished without also removing the sulfur dioxide.
4. Acid Titration Method: Hydrogen Peroxide
This method is safer to use without a filter because filters can
remove some of the sulfur dioxide. Where possibilities of interference
can be discounted or neglected the peroxide method has very desirable
features.
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5. Spectroscopic Methods
An instrument based upon second derivative spectroscopy can
detect 10 ppb of sulfur dioxide. One model can monitor S0£, NO, N02 and
03 sequentially. In principle, this procedure is very attractive and
the sensitivity for sulfur dioxide is satisfactory.
6. Other Methods
Fluorescence
A method has been developed which uses the fluorescence
excited in sulfur dioxide by zinc 213.8 nm or cadmium 228.8 nm (Okabe
e_t al. 1973) . The intensity of fluorescence is linearly dependent on
the sulfur dioxide concentration. Water, carbon disulfide, nitric
oxide and ethylene are interferences.
Flame Photometry
Sulfur-containing compounds burned in a hydrogen-rich flame
produce a luminescence in the near ultraviolet which can be correlated
to the atmospheric concentration of the compounds. If other sulfur
compounds are present in small enough concentrations, this method
can be used for a very effective sulfur dioxide monitor.
Gas Chromatography - Flame Photometry
The lack of selectivity of the flame photometric detector
can be circumvented by preliminary gas chromatographic separation of
such compounds as hydrogen sulfide and methyl mercaptan. This can be
effected and still maintain satisfactory sensitivity for sulfur-dioxide.
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Ampetrometry
One method involves absorption of sulfur dioxide in an
acidified bromide solution in which bromine is electrolytically
generated. The reaction between bromine and sulfur dioxide is kept at
an endpoint condition by automatic means. The current required to
produce the bromine is measured and used as the indication of the
concentration of sulfur dioxide.
Electrochemical Analyzers
The sulfur dioxide diffuses through a membrane into an
electrochemical cell at a rate proportional to the concentration of the
gas. The instrument measures the current generated in the electrochemical
cell as a result of the introduction of sulfur dioxide.
7. Use and Comparison of Methods
Since the criteria document was written, considerable
experience in the field has been obtained by EPA and many local agencies
in monitoring sulfur dioxide. If the revised document is to have any
value as a guide.to measuring sulfur dioxide then a thorough review of
this experience should be summarized. The proper use of the West-Gaeke
method and its relationship to other methods should be given primary
attention.
Section E - Other Methods of Measuring Pollution by Sulfur
Oxide
1. Sulfation Rates of Lead Peroxide Candles
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could be considerably shortened. For the sake of scientific accuracy
the fact that lead peroxide is not a peroxide and is more properly lead
dioxide should be mentioned.
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Chapter 3 - Atmospheric Concentrations of Sulfur Oxides
Since the most recent data in this section are ten years old,
it is obviously in need of updating. This would be especially
necessary in the area of sulfuric acid and sulfates in relation to
sulfur dioxide.
The vast amounts of data which' have accumulated since the criteria
document was written should be reviewed and summarized in this chapter.
Important items which should be featured are:
(1) Trends showing decrease in ambient concentrations as control
programs were instituted in various cities and states.
(2) Discussion of tall stack point source impacts versus area
source impact.
(3) Validity of various monitoring data sets in view of present
knowledge about measurement problems.
(4) Comparison of trends shown by ambient sulfur dioxide and
sulfates at locations where both measurements were made.
The subject of regional air pollution and acidity of rainwater is
one on which much data has accumulated since the publication of the
initial document. It is certainly a subject of importance and it should
be dealt with in a separate chapter on transport and deposition of
pollutants over large distances. This should include a discussion of
the potential effects on ecosystems.
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Chapter 4 - Effects of Sulfur Oxides in the Atmosphere on Materials
In general, the evidence cited in this chapter pertains to S02
levels in the atmosphere which far exceed current levels. On this
basis, the chapter may tend to overestimate the existing situation.
The material in this chapter must be used with caution and
requires additional information in order to draw inferences about the
economic effects of pollutants on materials.
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Chapter 5 -' Effects of Sulfur Oxides in the Atmosphere on Vegetation
The Revised Chapter 5 on "Effects of Sulfur Oxides in the
Atmosphere on Vegetation" in the Air Quality Criteria for Sulfur Oxides
(EPA-23-73-030, dated September 1973) has been carefully reviewed.
In general: (a) the document drew together a mass of information
available in several hundred publications through 1972 and, for the
most part, the interpretations are soundly conceived; (b) there have been
significant advances during the intervening years giving more depth in
several areas and leading to other interpretations, so we feel a revised
issue would be justified: and (c) the composition and presentation of
ideas are extremely awkward at many points and sometimes very difficult
to interpret so a complete rewriting of the document is recommended.
One may gather perspective for this idea by carefully examining the fine
review by I. Ziegler (1975), The effect of S02 pollution on plant
metabolism. Residue Reviews 56: 79-105. This reveals the tremendous
strides made in our knowledge on the mechanisms of action of different
sulfur compounds and the biochemical effects on different plants.
There is a significant growing body of knowledge on the sensitivity
of different cultivars and native plants, on the interaction to mixtures
of air pollutants, the effect of ecological conditions on the biochemical
and physical response of plants to exposure, upon the secondary effects
such as winter hardiness, effects of acid rains on ecosystems and
response to plant pathogens and insect pests. Each of these subjects
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ought to be brought down to date. The tabulation of sensitive species
should be carefully examined with an idea of adding new data and the
stages of maximum sensitivity and showing the cultivars used.
Specific sections and suggestions for editing at crucial points:
Page 1, A. General. The review by Ziegler 1975 probably should be
included. Either here or later, reference should be made to the significant
new developments such as effects on lichens, beneficial and harmful
effects from acid rains, the potential for long range ecological changes
and impact on ecosystems, biochemical mechanisms and interaction of
pollutant mixtures. Delete (in paragraph 3) such trite and meaningless
statements as "based on both professional and scientific judgments."
Can you have one without the other?
B. Paragraph 1. "pigmented foliar patterns" might be changed to
"visible effects appear as necrotic zones or changes in color either
by chlorosis or unusual pigment development." The subtle effects are
defined redundantly. Why not say "Subtle effects are biochemical or
physiological changes that do not lead to tissue destruction or visible
changes but may adversely affect orderly development"?
B. 1 - Paragraph 1. It says "Acute injury is severe injury that
occurs within a few hours etc." The real meaning is that "Acute
injury is visible damage in the form of necrosis or pigment changes
that occur after brief exposure to the toxicant."
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B. 1 last sentence. Visual SC>2 symptoms or visible? Why not say,
"The outstanding acute symptoms have been accurately illustrated in
three colored pictorial atlases (12-14) for the more susceptible
species"? Likewise, B. 1, a paragraph 2 is a miserable statement. The
bleached and necrotic areas occur on both monocotyledonous and dicotyledonous
plants but are frequently restrained to the interveinal areas so they may
appear as streaks on the former and irregular blotches on the latter.
On both there can be marginal or tip necrosis distributed according to
the stage of development of the foliage at the time of exposure.
On page 2 under 2 - Subtle effects, there is equally poor, almost
meaningless composition. "Processes are molecular or microscopic in
nature." Why not say: ''By definition the subtle effects are changes
in one or more biochemical mechanisms essential to the plants' welfare
without visible mechanical changes in the outward appearance of the
plant during the period of exposure. If the subtle effect persists long
enough so food manufacture, storage and conversion into energy and
cellular structures are impaired, there may be an eventual reduction in
growth and productivity."
Page 3. Katz (9) would be improved by specifying duration of
exposure. The reference to Arndt 35 likewise has a time-dosage frame.
Page 4, paragraph 2. Does extreme sensitivity of Bel W tobacco
pertain to photochemical oxidants especially ozone rather than to SC^?
This point should be checked. Omit discussion in same paragraph on
radish roots or rewrite it, "Observation that root production was
suppressed in radish by exposure to 131 to 160 g/M^ (0.05 to 0.06 ppm)
for 40 hours in each of five weeks could not be confirmed according to
Tingey et al. (30)."
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Page 4, mechanism of action. More recent information is
available on oxidation of S02 to SO^ (see Ziegler,,89).
Page 5, first sentence. Should not reference be made to the
alleged increase in susceptibility to winter injury in conifers from
exposure to SC>2?
Page 5, last paragraph. Brandt and Heck also pointed out that others
had recommended withholding water during periods of exposure to SC>2,
but that they did not necessarily endorse the idea.
Page 6, f. This entire section should be rewritten to incorporate
various reports released in the past three years. There are different
kinds of effects described from use of SO^ and combinations with 02, F, etc.
Page 6, (2). Genetic plasticity? The various cultivars of crop
plants and naturally occurring biotypes differ appreciably in their
reaction to SOo. Sometimes these differences may be as great as the
difference in reaction of different species of plants..." (broaden
examples). There have been several recent publications in this subject
matter area (Shapiro and Brownman, 1972; Hayston and Miller, 1972;
Brandle and Ericman, 1973).
Page 8, F. There are many new references available on reaction
of lower organisms to S02 and the possible inference for ecosystems.
The reaction of roses to Diplocarpon was reported by James before
Saunders.
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Page 9, G. There have been more recent publications and more
comprehensive interpretations in this area than almost any other
pertaining to SC^ and NOX. They cast more light on the SC>2 problem
than almost anything else so they should be reviewed in detail and
interpreted.
Page 10, H,.1. There are some beneficial effects from SQ2 presence
so this aspect might be balanced against the damage for other species
or in other soil conditions.
Page 12, column 2, paragraph 2. The relation of chlorotic dwarf
to conifer development in the presence of S02 is very vague as presented.
In paragraph 4 it is proper to point out that radish has been injured
by extremely high exposure in well conceived experiments, but is there
any evidence even in poorly conceived experiments that a reduction in
yield may occur (see Ringley and Hecht, Beasley). A critical review
is in order.
Page 18, Alfalfa. Is there a typographical error in that injury
of 5 and 19% is reported from identical treatments?
Page 19, Table 5-6. Should "injury" be defined more precisely as
"causing visible lesions and color changes on foliage"? Do the examples
apply to minimum rather than maximum dose for symptom expression? The
trouble arises from the heading. Suggest: "Table 5-6. Concentration of
SOo in air capable of causing visible lesions on species of agricultural
and forest plants after exposure for periods of one to eight hours."
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Page 24. What is a "threshold injury"? Suggest as a heading:
"Table 5-8. Calculated threshold for S02 to injure plants with different
degrees of resistance after exposure for periods in the range of 0.5 to
8.0 hours."
Page 25, Table 5-9. This table should be checked carefully to see
if data have become available on additional species or if any of the
species now listed should be transferred to a new classification.
Page 32, Summary. The following is suggested as the introductory
paragraphs.
There are numerous conflicting reports on the damage to vegetation
by sulfur oxides. This was inevitable because species, cultivars and
wild biotypes differ in their degrees of resistance, in their susceptibility
during different stages of their development and to the interaction
between the sulfur oxides and other pollutants and the ameliorating
effects of environmental conditions. In addition, the sulfur oxides
appear in different states of oxidation, as gases and aerosol acids
and differ in the rate at which they accumulate in the foliage and
become detoxified by conversion to relatively harmless sulfate ions.
In general, the environmental conditions that regulate stomatal movement
or expedite differentiation of tissues and cuticularization of exposed
surfaces will modify the severity of symptoms in a plant at a given state
of physiological susceptibility.
The response of plants may be based upon subtle physiological changes
by interference with the orderly biochemical processes of the cell.
Brief impact on these biochemical processes may not have an enduring or
harmful effect on the growth and productivity of the plant. However,
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if necessary intermediates are blocked or a vital process such as
photosynthesis, respiration or enzyme production is suppressed indefinitely,
there may be harmful effects that reduce the value of the plant to
mankind's needs, increase the plant's liability to damage by pest
attack or adverse environmental effects or intercede in the orderly
development and maturation of ecosystems.
These nonvisible effects may be classified as "subtle" because even
their presence or damage may not be detected much less measured. They
usually fall into a classification of chronic exposure rather than
acute or visible injury.
The visible injury may express itself as a marginal necrosis in
dicotyledonous plants and as tip burn in the monocotyledonous plants and
conifers. Intracostal burning and blotches may appear complicated by
other forms of injury such as nutritional disorders and drought injury.
Very frequently the leaf injury occurs in the palisade and mesophyll cells
between major veins so the symptom may appear as streaks on partially
resistant foliage of monocotyledonous plants and irregular blotches
on others. A frequent prelude to necrosis is a change in a color such
as chlorotic flecking and general chlorosis or the inciting of various
shades of brown or red tints in dying tissue. Other visible symptoms
are suppression of elongation in stems and branches and suppresion of
bud growth.
The severity of damage from either subtle or visible effects depends
upon the stage of development in different species. Enlargement of
vegetative organs may be suppressed in early stages of growth, and the set
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of seed and fruit and their orderly expansion may be damaged most
at the time of anthesis or pollination.
(Proceed to mechanism of action, detoxication and details of
susceptibility, time-dose relations, etc.)
The material in this chapter must be used with caution and requires
additional information in order to draw inferences about the economic
effects of pollutants on plants.
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Chapter 6 - lexicological Effects of Sulfur Oxides on Animals
Since the chapter was written in 1968, almost ten years ago, it is
in obvious need of updating. This is especially true in the area of
sulfuric acid and sulfates. Data available on these compounds will
emphasize the importance of particle, size and the fact that "particulate
sulfate" as such has no toxicological meaning. The implications of this
should be discussed.
The finding of importance from studies of pathology is that sulfur
dioxide can cause alterations in mucus production which resemble chronic
bronchitis. Additional work on this has appeared since the document was
written (Mawdsley-Thomas et al. Inhaled Particles and Vapors III) . This
one important point was somehow left out of the summary of the current
document.
The effects of sulfur dioxide on ciliary action per se is of
minimal importance. What is important is the overall possible effect
on clearance mechanisms. There have been several studies on the
effect of sulfur dioxide on clearance of particles which have appeared
since the document as well as the effect of sulfuric acid on bacterial
clearance done by Fairchild- at EPA. These should be discussed in a
section which is retitled "Effects on Clearance Mechanisms" rather
than "...on Ciliary Action."
The extensive work on two year exposure of monkeys and guinea
pigs done at Hazelton Labs should be included in a section which is
retitled "Chronic Exposure" rather than "Lifetime Exposure".
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The present document discusses the only work done on absorption
of sulfur dioxide at air pollution type concentrations which indicates
that at these low levels, it is not absorbed by the upper respiratory
tract. When the summary is reached, for some incomprehensible reason,
the only fact related to air pollution concentration is ignored and the
usual statement is made that "sulfur dioxide is almost entirely absorbed
in the upper respiratory tract". This should be rectified in the revision.
The biochemical section needs updating. The work of Gunnison and
Palmes on the occurrence of sulfonates in plasma should be included.
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Chapter 7 -. Toxicological Effects of Sulfur Oxides on Man
Tn this area there has not heon a vast amount of work done since
the criteria document was published. The main thing that needs
discussion here over and above the chapter as it stands is the work
of Bates and Hazuka and of Hackney and Bell on the combined effects
of sulfur dioxide and ozone. This is extremely important. There is
currently work under way to clarify whether or not particles play a
role in this interaction, so information relevant to that point should
be available.
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Chapter 8 - Combined Effects of Experimental Exposures to Sulfur
Oxides and Particulate matter on Man and Animals
This chapter needs to be updated. Tt should take note of the
fact that sulfuric acid and sulfur dioxide are additive at low concentrations
not more than additive as they are at high concentrations. It should take
note of the work of Rylander on the effects on clearance mechanisms of
combinations of sulfur dioxide and coal dust or manganese dioxide. It
should note the fact that copper is a potent potentiator of sulfur dioxide
and relate this to the studies of Eatough on the binding of sulfur
dioxide as sulfite to copper containing aerosols. It should take note
of the Hazletdn Laboratories studies of long term exposure of monkeys to
sulfur dioxide and fly ash. It should take note of the New York
University studies indicating that a background exposure to sulfur
dioxide with intermittent exposure to benzo(a)pyrene will produce
squamous cell carcinoma of the lung in rats whereas inhalation of just
the carcinogen will not do so. It should take note of recent studies
from the Hazelton Laboratories indicating that nitrogen dioxide and
sulfuric acid are more than additive in their pathological effects on
monkeys.
What is needed is a summary which takes the toxicology data from
Chapters 6, 7 and 8 and interprets it and puts it together. It should
be made plain how the material in Chapter 8 relates to atmospheric
chemistry and the forms in which the sulfur occurs in the atmosphere.
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Toxicology is one of the basic inputs to a criteria document. The numbers
cannot usually be directly extrapolated; the concepts can be extrapolated
to serve a useful purpose. There has been enough research done in the
area of the sulfur oxides to yield such useful information. The
summary of this section should not be just a recap of the findings; it
should be more akin to the "Discussion" section of a paper in which the
author tells you what the findings presented have to do with the problem
at hand.
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Chapter 9 Epidemiological Appraisal of Sulfur Oxides
This chapter, which is generally assumed to be the most important
chapter in the document, discusses attempts to relate observed health
effects to observed levels of pollution, It is in this chapter that it
is particularly critical that sulfur oxides and particulates be treated
as a unit. The chapter has been reviewed till it is threadbare. The
best balanced critiques of tha epidemiology in the sulfur oxides-
par£iculate area are those of Ian Higgins in the Rail Report don© for
the Office of Management and Budget (A Review of the Health Effects of
Sulfur Oxides, dated October 9, 197,3, submitted by David P. Rail,
Institute of Environmental Health Seienees, in r%§p©ns% t© a
fer such a review frem tht Offies ©f Management and Budget t©
0f Health, Idueitien, and Waif art) and by Htgftn® ani
is £ht Freeeedings ef thi Genlerinet en Health ifftet§ ©f Ai¥
Aeadetny ef Seiineti, Oe£§be? 3=S, 1973 (e@mmtttfe% ©n
, U.S. Senate Commie toe ?rint, Serial No, 93=13> N©v
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