PB 199 903
GUIDES FOR SHORT-TERM EXPOSURES OF THE PUBLIC TO AIR POLLUTANTS.
1. GUIDE FOR OXIDES OF NITROGEN
National Academy of Sciences - National Research Council
1 April 1971
NATIONAL rECHNICAL INFORMATION SERVICE
Distributed , . ,'to foster, serve and promote the
nation's economic development
and technological advancement.'
U.S. DEPARTMENT OF COMMERCE
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Guides for Short-Term Exposures of the Public to Air Pollutants
1. Guide for Oxides of Nitrogen
Prepared under Contract No. CPA 70-57 between the
National Academy of Sciences, Advisory Center on
Toxicology and the Air Pollution Control Office of the
Environmental Protection Agency.
by
The Committee on Toxicology
of the
National Academy of Sciences - National Research Council
Washington, D. C.
Contract Monitor:
Dr. Vaun A. Newill, Director
Division of Health Effects Research
Air Pollution Control Office
Environmental Protection Agency
Durham, North Carolina
The information contained In this
letter Is intended only as guirlanci
for your professional and technical
staff and contractors. It is not for
public distribution or attribution
to the Natioral Academy of Sciences
without prior written approval.
1 April 1971
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INTRODUCTION
The Air Pollution Control Office (APCO) ha a focused its initial
concern on long-term exposures of the public to air pollutants. It is also
concerned with occasional circumstances in which the public may be
exposed briefly to relatively high concentrations of air pollutants. For
example, steam boilers usually have short bursts of high emissions when
the tubes are blown or when the fires are started up. Similarly, batch
processes in the metallurgical industry produce pulses of effluent. The
testing and launching of rockets result in intermittent releases of exhaust
products. Rapidly changing meteorological conditions may result in
short periods of high concentration of stack effluents in localized areas.
Accidental release of chemicals sometimes occur'in industry or during
transport, and may lead to public exposure.
Recognizing these occasional peak additions to the ambient
exposure of the public, APCO has requested the assistance of the
Committee on Toxicology of the National Academy of Sciences-National
Research Council in providing Guides for Short-Term Exposure Limits
for Air Pollutants.
In preparing these guides, the Committee utilized the principles
described in the NAS-NRC document entitled ''Basis for Establishing
Short-Term Inhalation Exposure Limits of the Public to Atmospheric
Pollutants. "
In studying the literature sources for this document, primary
consideration was given to material dealing with brief, intermittent
exposure to the nitrogen oxides.
In this Guide the effects of oxides of nitrogen on domestic animals,
fish and wildlife, vegetation, and materials are not included. Analytical
and air-monitoring procedures are also excluded. These subjects are
discussed thoroughly in "Air Quality Criteria for Nitrogen Oxides,"
to be published early in 1971 by APCO.
Nitrogen Oxides
The nitrogen oxides of possible concern for air pollution purposes
are nitric oxide (NO), nitrogen dioxide (NOj), and nitrogen pentoxide
(N2Os). Other oxides are known to exist but are of no concern because of
their relatively low toxicity or absence from ambient air.
I.
Nitric Oxide
Nitric oxide is found to be of little concern as an air pollutant
since it is not an irritant gas (69) and is one-fifth as acutely toxic as
NO2 (5). In the presence of oxygen, NO is converted to NO2 at a rate
described by the equation:
d[NO2]/dt = k(O2] [NO]2
where [NO2], [O2], and [NO] represent the concentrations of the various
gases in molcs/cc, t is time, and k is a rate constant for temperature
having a value at 20° C of 14. 8 x 10-3 m6 moles'2 sec"1 (69).
Westberg, et ai.(78) have reported that the conversion of NO to
NO2 is influenced by the presence of other pollutants, such as carbon
monoxide and ozone, which might also be present in the air.
II.
Nitrogen Pentoxide
Conflicting reports on the toxicity of NjOs are present in the
literature (3). Diggle and Gage (1-2) report the toxic effects of N2O5
to be qualitatively similar to those of ozone (03) although N2Oj is about
three times as active as a pulmonary irritant as the latter. They
classify N^O^ as a lung irritant with a potency of the same order as that
of phosgene, and claim that the increase in the toxicity of an 03
atmosphere brought about by the presence of oxides of nitrogen can be
attributed to N£Os present.
On the other hand, Byers and Saltzman, as reported in Stern (5),
found N2Oj to possess an 1X50 for albino mice of approximately 75 ppm
(~ 10X that of 03). No time of exposure was given. Stokinger (6) in
preliminary studies showed that no deaths occurred in rodents upon
exposure to at least 42 ppm of N2Os. Stokinger expresses the opinion
that the claims of Diggle and Gage are not supported by their data.
Byers and Saltzman (in 5) attribute the greater apparent toxicity found
by Diggle and Gage to their method of administering N2Oj as a solution
in chloroform.
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The kinetics of the decomposition as well as the synthesis of
have been extensively studied under various conditions of tempera-
ture, pressure, radiant energy, concentration, precursors, and co-
contaminants (72-76). It becomes evident that ^Oj as well aa NO react
in air to form a variety of products, the principal one being NO2-
Because of its relative prevalence, stability, and toxicity, NC>2 is the
oxide of nitrogen of primary concern as an air pollutant.
III.
Nitrogen Dioxide
From the available scientific literature on the physiologic and
toxicologic effects of gaseous nitrogen dioxide (NC>2). it is apparent that
NC>2 as a freely diffusible gas has the potential of causing adverse effects
on human health and well-being. These are summarized in Table C -
Appendix II. It should be noted that the data in the literature from which
Table C was derived were based on exposures of "normal" healthy human
volunteers. Similarly, most of the ancillary information on animals given
in the Summary, and in Tables A and B of Appendix I, is from healthy
animals. The population to which this Guide is to be applied has a wide
range of states of health and well-being.
Factors Affecting Human Response to NO2
Among the most critical items to be recognized in deriving
limiting exposure values for the Guides are the factors and conditions
that can modify and significantly alter human response to NO2- The
five most important (temperature, predisposing disease, heredity, age,
and interactions with other environmental pollutants) are discussed below.
Temperature
A commonly overlooked and disregarded condition that greatly
modifies the response to NC>2 is temperature. Experimental animals
exposed to the additional stress of a hot or cold environment were more
susceptible to the effects of NO2- A minimum toxic effect was observed
at 15° C, with an increased effect above and below this temperature
(11) and (12).
Predisposing Disease
Individuals who have asthma, chronic bronchitis,emphysema, and
other forms of chronic obstructive pulmonary disease form the groups
which will be most severely affected by short-term exposure to high
levels of nitrogen oxides. Current evidence indicates that normal healthy
individuals will not be adversely affected by short-term exposures that
produce effects among these more susceptible groups (62)
Hereditary Predisposition
In addition to the well-known hypersueceptibility of the hereditary
asthmatic, a recently discovered association between the hereditary
defect, serum antitrypsin deficiency, and familial pulmonary emphysema
indicates the presence of another group of individuals with increased
susceptibility to the irritant gas NO£ (59). Individuals hemizygous for the
defect get along without respiratory difficulties until coming in contact
with respiratory irritants. Excessive exposures of those persons could
initiate early pulmonary emphysema. Although the frequency of hemizygotes
is not known nationwide in the U.S.A. , pedigrees obtained on small groups
in a few states indicate a hemizygote frequency between 2. 3 and 5 percent,
a not insignificant frequency (59).
It is a recognized medical fact that responses to environmental
influences among the very young and the very old are frequently different
from those in the in-between age groups - both in degree of sensitivity
and in the character of the response. Moreover, the bases for these
differing responses among the very young are not the same as those among
the very old. In the very young, increased susceptibility results from
either as yet undeveloped metabolizing enzyme systems or from
incompletely developed cellular structures. The age-susceptibility factor
for the young might be estimated to be between 5 and 10, on the basis of
increased neonatal deaths in mice exposed to ozone (37) (66).
Factors associated with old age, such as differences in physical
activity and pre-existing cardio- respiratory disabilities, will tend to
modify the susceptibility of various age groups to pollutants such as NO^.
Extremely little information exists from which to estimate these factors.
Interactions Affecting Response to Exposure
The information on NO^ interactions is incomplete and therefore
must be considered only suggestive for the purposes of Short-Term Guide
development. Each instance must be evaluated individually in this
respect, as to whether extrapolation of interactions to ambient pollutant
levels is scientifically sound.
a) Physicochemical Interaction. It would appear from two
independently derived sets of data that the acute toxic response to NO;
may be considerably reduced when NC>2 is inhaled for short periods (20
minutes to an hour), either concomitantly with or subsequent to, solid
or liquid particulates (65)(66). It proved to be immaterial whether the
concomitant aerosol was a solid or liquid participate (clays, siliceous
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materials, or oils); the mice survived longer when exposed to the NC>2-
particulate mixture than to NO2 alone, indicating an interaction with
reduced toxic effect. Similarly, oil mists of respirable particle size
greatly reduced the toxicity of NC>2 inhaled by rats, provided exposure
to the oils preceded exposure to NO^ by a few hours (66).
On the other hand, Boren (77) has reported that inhalation of carbon
particles followed by intermittent NO2 exposure resulted in lung destruc-
tion not observed with NO2 exposure alone. Exposure to NO2 followed
by inhalation of carbon particles resulted in a decreased macrophage
response contrary to the response normally observed after exposure to
carbon particles alone.
b) Physiologic Interactions. Almost complete protection from the
lethal effects of inhaled NOj was afforded mice exposed to mixtures of
NO2 and either hydrogen sulfide or mercaptans in four-hour exposures (5).
Although the level at which the different sulfur compounds negated the
effects of NO2 varied with the compound, some of them, including hydrogen
sulfide, counteracted the NO2 effects at molar ratios far below equivalency
(1.5 ppm H2S present with 82 ppm NO2>- This suggests that relatively
minute concentrations of these sulfur compocrxHs, if coexisting in the air,
can negate the physiologic effects of relatively much higher concentrations
of
Microbial Interactions
In contrast to the beneficial physicochemical and physiologic inter-
actions to be expected from certain air pollutants coexisting with NO2,
bacterial infection of the lung after NO2 exposure would appear to have
a distinctly adverse effect (23)(27)(68). A two-hour exposure to NO2 at
3. 5 ppm increased the mortality of mice infected with Klebsiella
pneumoniae. Daily exposures for two months was required to produce
the same increase in mortality at 0. 5 ppm. In considering the relevance
of these results to human responses, it is important to note that both the
exposed and control mice had overwhelming bacterial exposures. Forty-
seven percent of the infected controls not exposed to N©2 died in the first
instance, the 3. 5 ppm level, and 68 percent of the controls in the second
instance, the 0. 5 ppm level. It is difficult to reconcile the preceding
work of Ehrlich and Coffin with the observations of Wagner and his co-
workers (21). The latter exposed rats from a colony having spontaneous
pulmonary infections for 18 months at 5 ppm NOj. They found no
difference between the exposed and control groups in degree of pulmonary
infection, body weight gain, or oxygen consumption.
Summary of NO2 Toxicity
Nitrogen dioxide has been reported to produce the following
physiological actions:
1) It acts as a deep-lung irritant at high concentrations (several
hundred ppm for a few minutes), which may result in pulmonary edema
or lead to bronchiolitis fibrosa obliterans (53).
2) At levels of 10 ppm or more, the acute effects of N©2 are
additive with the effects of 03. At levels below 10 ppm, NO2 mixed
exposures with ozone had less than additive effects (6). The effects of
NO2 with other gaseous irritants (SO2, aldehydes, etc. ) are reported to
be additive (39) (38).
3) Lipoperoxidation was observed in rats exposed to NO2 at 1 ppm
for four hours. The maximum effect was observed 24-48 hours post-
exposure (22).
4) Alterations in mast-cell morphology were observed in rat lung
tissue after exposure at 1 ppm for one hour or 0. 5 ppm for four hours.
These alterations were reversible within 24-27 hours (47).
5) NO2 may increase the retention of particulates including
microbials by its ciliostatic effect. A concentration of 100 ppm inhibited
mucociliary activity within five minutes (16).
6) Chronic exposure of experimental animals to NO2 at a concen-
tration of 0. 5 ppm followed by a pulmonary challenge with high levels of
infectious organisms (K. pneumoniae) resulted in an increased mortality
(24). However, no such interaction of NO2 and bacteria was observed in
"naturally" infected rat lungs, suggesting synergism only at extreme
levels of bacterial challenge (21).
7) It was observed that the rate of tumor induction in mice having
spontaneous pulmonary tumors might have been accelerated from daily
exposures to NO2 at 5 ppm. Final tumor sire and mortality were not
affected (5).
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Concluding Remarks
From knowledge of the irritant action of NO2 on the respiratory tract
it is predictable that the individuals most susceptible to NO^ action are
not the healthy, hut those predisposed by age, heredity, and preexisting
respiratory disease. These are the persons that predictably will respond
most sensitively at concentrations to which healthy indiTiduals would be
unresponsive.
The effects of NC>2 are, within limits, reversible. The extent of
recovery seems to be a function of a) the degree of exposure, b) the
length of the interval between exposures, and c) the health and/or age of
the exposed individual.
As a consequence of the lack of this critical information, this Guide,
which has been developed for the protection of human health and well-being
from short-term exposure to oxides of nitrogen, is only a "best-judgment"
estimate. Hence, the following limiting values proposed should be regarded
as highly tentative and subject to revision as more appropriate and
pertinent information is developed.
Guide Values for Short-Term Exposure of the
Public to Oxides of Nitrogen
Short-Term Public Limits (STPL's)
10 min
30 min
60 min
5 hr/day,
3-4 days/mo
1 hr/day/yr
1 ppm
1 ppm
1 ppm
. 5 ppm
I ppm
Short-term Public Limits of 1 ppm for 10 min or less, 30 min or
60 min represent "ceiling" values not to be exceeded. Any fluctuations
in concentration must not exceed a maximum allowable concentration of
1 ppm. The limit of 0. 5 ppm for 5 hr/day, 3-4 days/mo represent an average
value for the 5-hr period as long as the "ceiling" limit of 1 ppm is not
exceeded.
These limits are suggested in order to protect asthmatics, believed
to be the most susceptible segment of the population.
It has been demonstrated that persons with chronic bronchitis ( a
condition believed to render those so afflicted particularly susceptible
to the effects of air pollutants) did not exhibit any significant pulmonary
effect when exposed to NC>2 at concentrations of 1. 5 ppm for 15 minutes.
Public Emergency Limits (PEL'S)
10 min
30 min
60 min
5 ppm
3 ppm
2 ppm
Although under optimal conditions the short-term public limits
require that there be no adverse health effects, public emergency limits
envision the possibility of some temporary discomfort, provided the
effect is reversible, and that no injury results from it. With respect to
NO^ exposure, it should be acceptable for an asthmatic to develop some
reversible and temporary bronchial constriction provided this does not
exceed the degree or duration that might occur as the result of moderate
exercise, deep breathing, exposure to inert particles, or exposure to
other gases or dusts normally present in the air. Such attacks do not
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produce residual damage. They often are induced as a part of diagnostic
procedures aimed at testing the reactivity of the tracheobronchial tree to
common respiratory irritants to which the individual normally may be
exposed (70). For this reason, short-term limit values of 5 ppm NC"2-
10 min or less, 3 ppm - 30 minf and 2 ppm - 60 min are recommended
as Public Emergency Limits (PEL's). These levels are less than
threshold limit values in industry, approximately 1/5 the Emergency
Exposure Limits (EEL's) (79) for an industrial population, in keeping
with the concept that an asthmatic might react with slight discomfort to
1/5 the concentration tolerated with slight discomfort by a normal person.
The limitation is designed to avoid enhancing susceptibility of the lungs to
K. pneumoniae rather than to completely avoid temporary, reversible
bronchial constriction in asthmatics. As further evidence, one asthmatic,
and a pilocarpinized normal volunteer, exposed at 5 ppm NO2 for five
min, were stated to have shown no effect (Table C of Appendix II).
Appendix I
Exposure of Experimental Animals to Nitrogen Dioxide
Mortality studies dealing with the toxic effects of inhalation of
NC>2 have indicated that the primary cause of death in acute exposure is
pulmonary edema (7) (8). In studies dealing with pulmonary changes in
animals exposed to NC>2, Hine et al.have demonstrated that sub-lethal
exposure to this gas may result in pulmonary edema, bronchiolitis, and
bronchial pneumonia. Using a variety of experimental animals and
exposing them at 5 to 250 ppm for 5 to 1,440 minutes, they observed
responses ranging from recovery with permanent lung changes to acute
asphyxia (9) (71). Methemoglobin is frequently seen in the blood of
exposed animals; however, it rapidly disappears from the blood after
exposure and may be absent 1-2 hours after exposure (7).
Several factors may influence the mortality due to NO;> exposure.
Hine et al.(9) and Gray et al, (11) found that exposures to relatively high
concentrations of NO2 for short periods of time had a greater lethal effect
than longer exposures to lower concentrations. (Higher concentrations
were more lethal than lower concentrations at an equivalent dose as
expressed by multiplying the concentration by the time, CT).
Tolerance to subsequent exposures of NO2 after previous exposure
to low levels of ozone or NC>2 has been reported (13) (14). It has been
found that exposure of animals at low levels of one irritant gas will produce
tolerance to a subsequent higher exposure of another irritant. This is
referred to as cross tolerance. Gases that are relatively insoluble in
tissue fluids more readily reach the bronchioli and alveoli, which seem
to be the site of action causing cross tolerance. Several gases besides
NO2 produce tolerance to themselves and cross tolerance with each other.
This tolerance, however, is evidently not acquired without adverse effects.
Dillman (15) reports that animals that had become tolerant to NO2 had
a 50 percent increase in the thickness of the "air-blood barrier" (all
tissue elements situated between an alveolus and its capillary bed).
Physiological, Biochemical, and Morphological Changes
Depression of mucociliary activity in excised rabbit trachea was
noted after exposure to NO2, 100 ppm for 5 minutes or 60 ppm for 10
minutes (16). Changes in mucus velocity in the guinea pig respiratory
tree (17) and bronchial mucus hypersecretion (18) have also been reported
in acute and sub-acute exposure of experimental animals.
Murphy et^L(19) exposed guinea pigs at 5. 2 to 13. 0 ppm NC>2 for
two or four hours and measured the respiratory function before, daring.
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Appendix I (cont'd)
and after exposure. In these animals the tidal volume decreased while
the respiratory rate increased, the net effect being the maintenance of a
nearly constant minute ventilation. In the same experiment, mice exposed
at 3. 7 to 7. 7 ppm NO^ for six hours exhibited a depressed running activity.
Biochemical studies by Buckley and Balchum (20) were carried
out on guinea pigs at two exposure levels, a repeated acute exposure
to 40 ppm NC>2 for a total of four hours, and a chronic exposure at 15 ppm
continuously for 10 weeks. The animals were sacrificed at the end of the
exposure periods and the lactate dehydrogenase (LDH) and aldolase
activity in organ homogenates were measured. In the continuous exposure
aldolase was elevated in all tissues and LDH was elevated in lung, liver,
and kidney. In the short-term exposure the LDH was elevated in serum,
liver, and kidney and aldolaae was elevated in serum, liver, kidney, and
spleen.
Wagner et al.(21) exposed dogs, rabbits, guinea pigs, rats,
hamsters, and mice for 5 hours/day, 5 days/week for periods up to
18 months at 1, 5, and 25 ppm NO2- The authors found no statistically
significant differences in body weight, hematology, and biochemistry
(alkaline phosphatase and Mg-activtated phosphatase) between control and
experimental animals. They did find, uu«ever, a possible tumorigenic
accelerating capacity for NOj in a strain of mice susceptible to
spontaneous tumors.
Thomas ^t al_.(22) exposed a group of rats to 1 ppm NO^ for four
hours and observed an absorption spectrum indicative of peroxidized
polyenolic fatty acids in the lung lipids of these animals. These
peroxidative changes were at a maximum between 24 and 48 hours post-
exposure.
Other rats were exposed at the same concentration (1 ppm for
four hours) but for six consecutive days. Analysis of lung lipids "suggests
that the longer exposure to NO^ produced more extensive and probably
cumulative oxidative changes than the single four-hour exposure did. "
In another series of experiments Thomas _et^ al. (47) exposed rats
briefly to low levels (0. 5-1.0 ppm) of NO2 and examined these animals
for changes in the lung mast cells. In animals exposed to 0. 5 ppm NC>2
for four hours or I. 0 ppm NC>2 for one hour and immediately sacrificed,
there was a reduction in the number of mast cells and those remaining
showed "evidence of loss of cytoplasmic granules, disorientation and
rupture." Histological examination of animals sacrificed 24 or 27 hours
post-exposure revealed no evidence of ruptured cells, indicating that
these observed effects were reversible.
10
(Appendix I cont'd)
The nature of "healing" in the rat-lung post-exposure to NOi was
examined in some detail by Freeman^t aL (48). They exposed rats for
1,4,10,16, or 20 weeks continuously to 15 ± 2 ppm NC>2. After exposure
animals from each group were allowed to recover for 0, 8, 20, and 52
weeks. Control rats of the same age were maintained. Lung weights
increased relative to those of the control animals at two different times.
The first increase was shortly after exposure and was believed to be
associated with hypertrophy of bronchiolar and adjacent alveolar
epithelium. After several weeks the lung weights of the exposed animals
tended toward normal, but a second increase in lung weight occurred in
aging, exposed animals. This second increase over normal was consistent
with an increase of collagen and elastic tissue in the alveolar parenchyma.
Freeman et al. observed that, in the longer-exposed animals, the
morphology of the lung tissue never did return to "normal. "
In a series of several experiments Freeman e^ al. and Haydon,
£t aL (49-54) exposed rats continuously to NO2 at concentrations ranging
from 0. 8 ppm to 100 ppm. The exposure times ranged from several days
up to three years (or the "natural" lifespan of the rats).
Exposure to 100 ppm and 50 ppm continuously caused relatively
rapid pulmonary damage in the rats; those exposed at 100 ppm began to
die within 24 hours (symptoms and pathology were pulmonary edema,
vascular congestion and focal hemorrhage), while those exposed at
50 ppm exhibited similar symptoms but not until several weeks after the
exposure was initiated. Table A summarizes the exposures and findings
of several of Freeman's experiments.
The emphasis of this work done by Freeman and his colleagues
is on morphological changes in the lung tissue, and unfortunately almost
no biochemical parameters were measured in the control and experi-
mental animals.
Kleinerman and Cowdrey (55) exposed 48 hamsters nearly continuous-
ly (20-23 hr/day) for 10 weeks to concentrations of NC>2 ranging from 45
to 55 ppm. Over one-third (approximately 16) of the exposed animals died
within three days of initiation of the exposure but only two additional deaths
were observed during the final eight weeks of exposure.
After the 10-week exposure, several of the surviving animals were
sacrificed immediately while the remainder were sacrificed four weeks
later.
Those animals immediately sacrificed displayed "extensive
epithelial hyperplasia and hypertrophy" in the region of the terminal
and respiratory bronchioles and proximal alveolar ducts. Ciliated cells
were rare. Inflammatory cells (neutrophils and macrophageslwere found in the
11
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respiratory bronchioles and alveolar ducts as well as in the peri
connective tissue. "A mild degree of pulmonary edema was obsi
the alveolar structures throughout the lung. "
[bronchial
observed in
In those animals sacrificed four weeks post-exposure, the authors
observed a regression of inflammatory and hyperplastic components of
the lesion as well as a lack of edema and tissue destruction. Lung volumes,
significantly greater in the exposed animals immediately after exposure,
tended to decrease, but had not returned to normal four weeks post-
exposure. Right ventricular weight appeared significantly heavier than that
of the control groups immediately after exposure, but there was no signi-
ficant difference four weeks later.
An interesting statement made by the authors is that the animals
were not observed to eat or drink to a significant degree during the 20-22
hours of exposure per day, yet there was no significant difference in
body weight between the control and exposed groups at the end of the 10
weeks of exposure.
Kleinerman and Wright (56) exposed rats (150 ppm, 75-80 ppm, or
15-20 ppm), rabbits (200 ppm, 100 ppm, or 25 ppm), and guinea pigs
(75-80 ppm or 15-20 ppm) to N©2 for one two-hour period. They observed
various responses ranging from death due to pulmonary edema to inflamma-
tion in animals exposed to a low dose. "Healing appeared to be practically
complete by two weeks after the insult" in those animals surviving the
initial challenge.
In a series of studies involving the "resistance of NOj-exposed
animals to Klebsiella pneumoniae, "Ehrlich (23-25) has reported an
increased susceptibility to this bacterial infection in animals exposed to
3. 5 ppm or higher NO2 for two hours as well as animals exposed to 0. 5
ppm NO2 for 6 or 18 hr/day for six months.
Mice exposed to 0. 5 ppm NO^ 6 hr/day for 3-12 months are
reported as exhibiting indications of early bronchial inflammation with
reduction of distal airway size and expansion of alveoli with signs of
early focal emphysema (26). Under similar exposure conditions, a delay
in bacterial clearance from the lungs was noted.
Henry_e£al. (57) used squirrel monkeys to demonstrate the
decrease in resistance to bacterial and viral infection during chronic
NO;> exposure. Animals were exposed continuously to NO2 at 5 ppm for
two months and at 10 ppm for one month. The exposures to NO^ were
followed by challenge with K_. pneumoniae (estimated dose = 4-9 x
10 organisms). Bacterial clearance was reduced in the NOj-exposed
animals and 3/11 of the exposed animals died after the bacterial
challenge while none of the controls (9 animals) died.
Appendix I (cont'd)
A total of 14 monkeys were challenged with influenza virus and six
of these animals were then exposed to 10 ppm NG>2- Within three days all
six of the animals had died while the eight controls all survived the
challenge. One of three animals died five days after viral challenge and
subsequent exposure to 5 ppm NO2-
Balchum_e£ al_. (26) have observed a circulating substance or
"antibody" in the serum of guinea pigs exposed to 5 ppm and 15 ppm NC>2
daily for up to 5-1/2 months. This "antibody" reacted in vitro with
protein extracted from normal lung tissue. Tilers of this antibody increased
with increasing duration of exposure and increasing concentrations of NC>2.
It was assumed that this substance was formed from the interaction of
NO2 and lung tissue in the exposed animals. No reports of human respira-
tory allergic responses to NOz exposure have been reported.
13
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Appendix I (cont'd)
Table A
Table B
Appendix I (cont'd)
Cont'.r-:-.is NOz Exposure
(From References 48-54)
0. 8 ± 0. 2 ppm NO2 to
21 rats for 2-3 years
2 ± 1 ppm NO2 to rats for
2-3 years
4 ppm NO2 to rats for 16 weeks
10 ± 1 ppm NOz (rats)
25 ppm NO2 (rats)
50 ppm NO2 (rats)
100 ppm NO2
Sustained tachypnea. 20 percent over
normal. Death was natural; histology
unremarkable.
Bronchial cells enlarged, few cilia
remaining. Indicative of "relative
dormancy or restrained activity."
Terminal bronchiolar epithelium was
hypertrophic.
Animals began to die of respiratory
failure after 16 months. Rats grew less,
developed "air-containing" thoraces,
and lungs were large and did not collapse
under atmospheric pressure. Increased
activity of goblet cells with much mucus,
aggregates of macrophages with bits
of proteinaceous debris. Alveolar ducts
distended.
All survived acute phase. Failed to
gain weight normally. Deaths occurred
about five months after exposure began.
Rats allowed to die (not sacrificed)
gained weight initially but lost up to
25 percent of their weight subsequently.
Lungs were heavier and larger than
those of controls. Hyperplasia and hyper-
trophy of epithelial cells with prolifera-
tion of connective tissue were observed.
Vascular congestion and focal hemorrhage
along with aggregates of macrophages
were common. Respiratory rate up
2-3 fold.
Two-thirds dead within two months.
Remarks similar to 25 ppm.
Deaths (rats) began within 24 hours,
pulmonary edema, vascular congestion
with focal hemorrhage.
Exposure
0. 5 ppm NO2 6 hr/day
for 3-12 mo
0. 5 ppm NO2 for 6-1
hr /day for 6 mo
1 ppm NO2 for 4 hr
1 ppm NO2 for 4 hr/day
for 6 days
3. 5 ppm NOz for 2 hr
5. 2 - 13 ppm for 2-4 hr
10 ppm NOz iOT 2 hr
1 ppm, 5 ppm, 25 ppm
NOz for & hr/day,
5 days/week for up to
IS mo
5 ppm and 10 ppm NO2
'Low" Level NOz Exposures
Results Observed Reference
Early bronchial inflammation (26)
with reduction of distal airway
size and expansion of alveoli
with indications of early focal
emphysema (mice).
Increased susceptibility to (23)
K. pneumoniae (mice).
Peroxidized polyenolic fatty (22)
acids in lung lipida. Max. at
24-48 hr post-exposure (rats).
Indication of cumulative changes (22)
as above (rats).
Increased susceptibility to (24)
K, pneumoniae (mice).
Increased respiratory rate, (19)
decreased tidal volume
(guinea pigs).
Increased retention of (27)
K. pneumoniae; decreased
minute volume (squirrel
monkeys).
No effect different from controls (21)
with possible increase in lung
tumors with 5 ppm and 25 ppm
groups (rats, rabbits, dogs,
guinea pigs, mice, and hamsters).
No difference between control and
experimental animals in spontaneous
pulmonary disease.
Increased susceptibility to (57)
K. penumoniae and influenza
virus (squirrel monkeysl.
14
15
-------
Appendix I (cont'dt
Summary of Experimental Animal Exposures
It appears that there is some discrepancy relative to the chronic
levels of NC>2 necessary to cause morphological as well as biochemical
changes in the lungs of exposed animals. This discrepancy is probably
due in part to 1) species and age variation in the experimental animals,
2) the biochemical parameters being measured as well as the relative
importance placed on these parameters, 3) a certain degree of "tolerance"
being exhibited by the animals. This tolerance, however, may be due to
undesirable changes in the morphology of the lung, such as thickening of
the alveolar walls and reduction of the rate of oxygen transfer, 4) other
substances present in the atmosphere, 5) the duration of exposure as
well as the time intervals between exposures.
Continuous 24-hour exposure, even to relatively low levels of
NC>2, leads to greater toxicological effects than exposure at similar or
even greater levels of NO2 interrupted by inhalation of clean air. Even
relatively brief interruptions of exposure seem to be beneficial in the
prevention of mortality and/or morbidity.
NC>2 can increase the susceptibility of the exposed animal to other
pulmonary problems, such as bacterial or viral infections and retention
of inhaled particulates, either by its mucociliary effects or its deeper
pulmonary effects. This synergistic effect with the viral or bacterial
diseases has been seen at relatively low exposure levels and would seem
to indicate the need for further investigation of NO2 synergism with other
chemical or bacterial pollutants.
16
Appendix II
Humans Exposed to Nitrogen Dioxide
The available experimental data on humans exposed to NO2 are
certainly not as extensive as data obtained on laboratory animals, but
some work has been done with human volunteers.
Cooper and Tabershaw (10) have summarized some of the litera-
ture reports of effects of NO2 on man, as shown in Table C. Tabershaw
et_al_. (29) comment that, in spite of species differences, the qualitative
responses of mammalian lung tissues are essentially similar and there-
fore many of the experimental findings with the lower animals are
applicable to humans. They report the major site of action of NO2 to be
on the lower respiratory tract, the effects in the upper respiratory tract
other than mild irritation being negligible.
The odor threshold to NO2 is between 1 and 3 ppm, although nasal
and eye irritation is not evident at this level. At 13 ppm, three out of
eight volunteers complained of eye irritation, and seven out of eight
complained of nasal irritation (10).
Reports of accidental exposures of humans to NO2 are numerous,
but the magnitude of exposure in most of these cases is not well docu-
mented and usually only estimated.
The clinical symptoms of acute inhalation of NO2 by humans have
been classified into three types (30): 1) Acute pulmonary edema developing
after a latent period of up to 30 hours. 2) Acute symptoms (dyspnea.
pulmonary edema, sweating) followed by a latent period sometimes lasting
up to a month. These effects followed by progressive dyspnea, with severe
cough and cyanosis. 3) Development of a chemical pneumonitis.
A classic example of human exposure to NO2 is the Cleveland
Clinic Disaster (31). Some of those exposed died almost immediately,
possibly from the additive effects of several combustion gases (HCN.CO,
NO2> etc. ). Other patients, who were practically free from any symptoms
upon going into fresh air, later (6-48 hours) succumbed to acute attacks
of dyspnea and cyanosis. Still others died days and even weeks later of
pneumonia. These delayed responses were attributed to the heavy exposure
of NO2 arising from the combustion of cellulose nitrate x-ray film.
Norwood e_t al. (32) report a case of NOj poisoning in a welder
exposed to about 90 ppm NO2 for 40 minutes (total oxides of N was greater
than 300 ppm). The welder experienced some shortness of breath and
mild chest discomfort during the welding operation, which took place in
17
-------
(Appendix II (cont'd)
a confined space. The symptoms cleared up somewhat upon his returning
to fresh air. Approximately eight hours later he experienced a gradual
increase in difficulty in breathing, and 18 hours later a physical examina-
tion indicated a respiratory rate of 22-24, a vital capacity of 42 percent
of predicted, and moist rales. A chest x-ray revealed pulmonary congestion
and edema. The patient was hospitalized for seven days and was diagnosed
as normal 21 days later.
Milne (30) describes a case of NC>2 poisoning in a chemist who
displayed the typical delayed response (12 hours post-exposure) after
being exposed to an unknown level of NO£. He was hospitalized with
pulmonary edema and discharged from the hospital seven days later as
"an apparent cure. " Thirteen days later (20 days after the original
exposure) the patient was rehospitalized with essentially the same
symptoms, despite the fact that no further exposure of NO2 took place.
The second recovery was much slower and a transient diabetic state was
observed and treated with insulin.
Kleinfeld (33) reports an exposure in which a chemist was exposed
to an unknown level of N©2 for four minutes. An 11-hour latent period was
followed by the development of pulmonary edema and pneumonitia.
Hospital treatment resulted in "recovery" within 15 days.
Seven men exposed to NO^ in a mining accident were observed
ovc-. ;. 11 month period (34). Two of these men had immediate symptoms
with no latent period while the other five did not exhibit symptoms until
14 hours to four weeks later. Five patients recovered 7 to 14 months after
the accident. Two of the men had previous histories of bronchitis. Their
symptoms reportedly became worse after the NO2 exposure and they are
now " handicapped. "
The fermentation of fresh silage can liberate NC>2 and exposure
to this gas in silos produces an ailment commonly referred to as "silo-
fillers disease." Lowry and Schuman (36) and Grayson (35) describe
several cases, the symptoms of which are typical for acute NO, inhala-
tion, i.e. , initial irritation, variable latent period, and finally dyspnea,
progressive weakness, etc.
Lowry estimates the following symptoms would be observed in
humans exposed to varying concentrations of NC>2 for 30 minutes to an
hour:
a) 500 or more ppm - acute pulmonary edema with death in less
than two days.
days.
b) 300-400 ppm - edema and bronchopneumonia fatal before 10
18
Appendix [I (cont'd)
c) 150-200 ppm - bronchiolitis obliterana with death in 3-5 weeks.
d) 50-100 ppm - bronchiolitis and focal pneumonitis with
spontaneous recovery.
e) 10-40 ppm with prolonged exposure might cause pulmonary
fibrosis and emphysema.
In a 24-week study involving the effects of community exposure
to NO2, Shy et al. (60-61) reported a lower three-quarter-second forced
expiratory volume among second-grade children in an area defined as a
"Mgh-NC>2 area," as compared with a ventilatory performance of children
in an area chosen as a "control area. " However, neither the gradient
of pollutant exposure nor the NC>2 concentrations on the day of ventilatory
testing were related to the ventilatory performance.
As part of the same study. Shy et_a^. recorded an excess in
respiratory-illness rate as reports! by the subjects of the study in the
"high-NC>2 area." The severity of illness, however, did not differ
between the "high-NO2" and the "control" areas, nor could a dose-
response relationship be established for NC>2 exposure. Any effect
attributed to NO;> exposure in this study could be related only to long-
term data since no correlation with short-term exposures could be
demonstrated.
The acute effects of NO2 on lung function and circulation of
healthy subjects, as well as subjects with chronic bronchitis, were studied
by von Nieding et^aL (62). The concentrations of NOj ranged from 0. 5
to 5. 0 ppm and the length of exposure was 15 minutes. The parameters
that were measured included the arterial O2 and COj partial pressures,
arterial pH, end expiratory O^ and CO2 gas pressures, cardiac
output, heart rate, stroke volume, systolic pressure in the pulmonary
artery, mixed-venous O2 and CO;> partial pressures, and mixed venous
pH. The parameters were measured before exposure, after 10 minutes
of NO2 inhalation, and 10 minutes after cessation of the 15-minute
exposure.
Healthy subjects as well as those with chronic bronchitis reacted
with a reduction in arterial O2 partial pressure upon inhalation of NO2
concentrations of 5 and 4 ppm. This was not observed when the subjects
were exposed at 2 ppm or less.
Airway resistance, measured by means of a body plethysmograph,
was determined in 63 subjects with chronic bronchitis who breathed air
containing 0.5-5.0 ppm NC>2 for 15 minutes. A significant increase in
19
-------
Appendix II (cont'd)
airway resistance was observed immediately after inhalation of NC>2 at
concentrations greater than 1. 5 ppm, but no significant effect was
observed at exposure levels below this concentration.
The authors report that any effects which they observed to be due
to the NO2 exposure were reversed within 10 minutes after cessation of
exposure in both the healtiysubjects and those with chronic bronchitis.
Appendix II (cont'd)
Table C
ppi"
0.05 (0.1 mg/cu m)
0.15 (0.3 mg/cu m)
0. 2
0.5
1 to 3
2.0
Effects of NO2 on Man (10)
Comment
10
10
10
13
20
USSR: Maximum allowable concentrations -
average during 24 hours
USSR: Maximum allowable concentrations -
single exposure
Calculated limit for space travel
Submarine maximum for 90-day dive
Odor threshold
Maximum allowable concentration for
industry (USSR) as of 1959
Ceiling threshold limit value for occupa-
tional exposures (average for 8-hour day,
5 days per week)
Exposure of one asthmatic and one pilocar-
pinized volunteer for 5 minutes, no effects
noted
60-minute emergency exposure level for
occupational exposure
Maximum permitted for one hour in
submarine
Normal volunteer exposed for 60 minutes
interpreted as not showing impairment of
pulmonary function
8 volunteers; 3/8 had eye irritation; 7/8
nasal irritation; 4/8 pulmonary discomfort;
6/8 olfactory cognition; 2/8 CNS effects;
all predominantly slight
Workers in HNOj recovery plants reputedly
exposed to levels averaging up to 20 ppm
for up to 18 months showed no ill effects
21
-------
ppm
zo
25
25
3-35
35
50
64
80
Appendix II (cont'd)
Comment
Emergency exposure limit for 30-minute
exposure
Emergency exposure limit for 15-minute
exposure
Human volunteers exposed for 5 minutes.
Slight or moderate nasal discomfort in 5/7,
pulmonary discomfort in 3/7, odor detected
by 6/7. No consistent changes in expiratory
reserve, vital capacity, or MBC
Workers exposed at 30-35 ppm to nitrous
fumes over several years; had no ill effects
Emergency exposure limit for 5 minutes
7 human volunteers exposed for 1 minute;
3/7 had pulmonary discomfort and nasal
irritation
Moderate irritation of larynx and increase
in respiratory rate in volunteers
In 3 to 5 minutes volunteers got tightness
of chest
100
300-400
500
Produced rapid, marked irritation of larynx
and cough in volunteers
Few minutes' exposure will cause broncho-
pneumonia and death
Few minutes' ejcposure will cause pulmonary
edema
On the basis of these kinds of data. Cooper and Tabershaw
recommend that "brief exposures of a general population should not
exceed 3 ppm over a period of \ hour. " This is based on the possible
potentiation of infections and on the odor thresholds.
22
Appendix III
NC>2 and Other Chemical Contaminants
Since NOj seldom is found as the single contaminant in the
atmosphere, it is desirable to study the combined effects of several
pollutants simultaneously. Bils and Romanovsky (37) exposed mice for
three hours to a synthetic smog produced by illuminating a mixture of
8 ppm propylene, 2.8 ppm nitric oxide, and approximately 25 ppm carbon
monoxide with ultraviolet lamps. The animals were sacrificed at intervals
up to 24 hours post-exposure. The animals were ages 6 months, 8 months,
15 months, and 20 months (average life span <2 years). It was reported
that no significant change was found in the six-month-old exposed group.
The eight-month-old animals sacrificed immediately after exposure
exhibited a slight swelling of the epithelium and endothelium of the lungs.
Delaying sacrifice for 18 hours "allowed" these changes to return to
normal.
Some permanent changes seemed to take place in the 15-month-
old exposed mice as well as in the ZO-month-old mice. Delaying
sacrifice in the older animals allowed further damage and revealed cell
debris in the alveoli.
Buchberg e^ a^. (38) produced a synthetic smog in order to study
statistical relationships between various exhaust components, certain
atmospheric reaction products, solar irradiation, and the eye-irritating
quality of the polluted air. They conclude that:
1) Eye-irritants are produced by the photochemical oxidation of
hydrocarbons - primarily the unsaturated ones.
2) Sunlight and nitrogen oxides are also necessary for the production
of eye irritation.
These interactions are discussed in detail in "Air Quality Criteria
for Hydrocarbons" and"Air Quality Criteria for Photochemical Oxidants,"
published by the National Air Pollution Control Administration as AP-64
and AP-63, respectively, in March 1970.
Abe et al. (39) studied the effects of NO2 and a mixture of NO2-SO2
on the pulmonary function of five human volunteers. Each subject was
exposed on separate occasions to 4-5 ppm NO2, 5 ppm SO2- or a mixture
of 2. 5 ppm NOj and 2. 5 ppm SO2, each for 10 minutes. In all subjects,
inhalation of NO2 caused an increase in both respiratory and expiratory
flow resistance, with the maximum occurring at 30 minutes post-exposure.
The author suggests that the net effect of the NO2-SO2 mixture is a simple
additive response.
23
-------
References
2.
3.
4.
5.
6.
7.
Diggle, W. M. and Cage, J. C. Toxicity of nitrogen pentoxide.
Brit. J. Ind. Med. 11:140-144 April 1954.
Diggle, W. M. and Cage, J.C. The toxicity of ozone in the presence
of oxides of nitrogen. Brit. J. Ind. Med. 12:60-64 January 1955.
Cray, E. LeB. Oxides of nitrogen: Their occurrence, toxicity, hazard.
AMA Arch. Ind. Health 19:479-486 May 1959.
Mikhatlovskaya, M. I. , Yakovleva, E. A. , and Klark, G. B. Chemical
analysis of air for corrosion-causing impurities. Trudy. 1st. Fiz. -
Khhn.,Akad.Nauk SSSR p. 56-68, 1960. Chem.Abstrs. 55:No. 26972h,
1961.
Stokinger, H. E. "Effects of air pollution on animals. " In: Air
Pollution. Arthur C. Stern, Editor. Vol. 1. Academic Press,
1962. p. 282-334.
N. Y.
Stokinger, H. E. Evaluation of the hazards of ozone and oxides of
nitrogen. Factors modifying toxicity. AMA Arch. Ind. Health 15:
181-190, 1957.
LaTowsky, L. W. , MacQuiddy, E. L. , and Tollman, J. P. Toxicology
of oxides of nitrogen. I. Toxic concentrations. J. Ind. Hyg. and
Toxicol. 23:129-133 April 1941.
8. Cray, E. LeB. , MacNamee, J. K. , and Goldberg, S. B. Summary
report on the toxicity of the oxides from red fuming nitric acid.
Med. uiv. Res. Report 52, Dept. of the Army, Chem. Corps. , Med.
Lab. Army Chem. Center, April 1951.
9. Hine, C. H. , Meyers, F. H. , Wright, R. W. , and Dewey, M. L.
Pulmonary changes in animals exposed to NOj. Western Pharmacol.
Soc. 7:19-22, 1964.
10. Cooper, W. C. and Tabershaw, I. R. Biological effects of nitrogen
dioxide in relation to air quality standards. Arch. Environ. Health
12:522-530, April 1966.
11. Gray, E. LeB. , Patton, F. M. , Goldberg, S.B., and Kaplan, E.
Toxicity of the oxides of nitrogen. II. Acute inhalation toxicity
of nitrogen dioxide, red fuming nitric acid, and white fuming
nitric acid. Arch. Ind. Hyg. Occup. Med. 10:418-422, 1954.
12. Paribok, V. P. and Ivanova, F. A. Air temperatures and the toxic
effects of nitrogen oxides. Cigiena Truda i Prof. Zabolevaniya
(Moscow) 9:22-24, 1965. Fed. Proc. (Translation Suppl. ) 25,
Pt. III. T851-T853 1966.
13. Fairchild, E. J. II. Tolerance mechanisms: Determinants of lung
responses to injurious agents. Arch. Environ. Health 14:111-126
January 1967.
14. Stokinger, H. E. and Scheel, L. D. Ozone toxicity. Arch. Environ.
Health 4:327-334, 1962.
15. Dillmann, G. , Henschler, D. , and Thoenes, W. [Effects of NC>2 on
lung alveoli of mice; morphometric electron microscopic studies.]
Archiv. fllr Toxikol. 23:55-65, 1967.
16. Cralley, L. V. , The effect of irritant gases upon the rate of ciliary
activity. J. Ind. Hyg. Toxicol. 24:193-198 1942.
17. Carson, S. and Coldhamer, R. E. Biochemical defense mechanisms
against pulmonary irritants. Food and Drug Research Labs. , Inc,
Maspeth, N. Y. October 1968. Proj. AF 7163
18. Ventura, J. C. and Domaradski, M. Pulmonary effects of nitrous
dioxide on the hypersensitive guinea pig. Ann. Allergy 27:100-107
March 1969.
19. Murphy, S. D. , Ulrich, C. E. , Frankowitz, S.H., and Xintaras, C.
Altered function in animals inhaling low concentrations of ozone
and NO2. Am. Ind. Hyg. Assoc. J. 25:246-253 May-June 1964.
20. Buckley, R. D. and Balchum, O. J. Acute and chronic exposures to
NO2, effects on oxygen consumption and enzyme activity on guinea
pig tissues. Arch. Environ. Health 10:220-223 1965.
21. Wagner, W. D. , Duncan, B. R. , Wright, P. C. , and Stokinger, H. E.
Experimental study of threshold limit of NO£. Arch. Environ.
Health 10:455-466 March 1965.
22. Thomas, H. V. , Mueller, P. K. , and Lyman, R. L. Lipoperoxidation
of lung lipids in rats exposed to nitrogen dioxide.Sclence:159-532-
534 Feb 2, 1968.
23. Ehrlich, R. and Henry, M. C. Chronic toxicity of nitrogen dioxide.
I. Effect on resistance to bacterial pneumonia. Arch. Environ.
Health 17:860-865 Dec 1968.
-------
24. Ehrlich, R. NO^ lowers resistance. Am. Med. Assoc. J. 198:43
Oct 24, 1966.
25. Ehrlich, R. Effect of NO, on resistance to respiratory infection.
Bacteriol. Rev. 30:604-614 Sept. 1966. Air Poll. Control Assoc. ,
Abstracts 13: No. 8205, May 1967.
26. Blair, N. H. , Henry. M. C. , and Ehrlich, R. Chronic toxicity of
nitrogen dioxide II. Effect on histopathology of lung tissue. Arch.
Environ. Health 18:186-192 Feb. 1969.
27. Henry, M. C. , Ehrlich, R. , and Blair, W. H. Effect of nitrogen
dioxide on resistance of squirrel monkeys to Klebsiella pneumoniae
infection. Arch. Environ. Health 18:580-587 April 1969.
28. Balchum, O. J. , Buckley, R. D. , Sherwin, R. , and Gardner, M.
Nitrogen dioxide inhalation and lung antibodies. Arch. Environ.
Health 10:274-277 Feb. 1965.
29. Tabershaw, I. R. , Ottoboni, F. , and Cooper, W. C. Oxidants: Air
quality criteria based on health effects. J.Occup. Med. 10:464-
484 Sept. 1968.
30. Milne, J. E. H. Nitrogen dioxide inhalation and bronchiolitis
obliterans. A review of the literature and a report of a case.
J.Occup. Med. 11:538-547 Oct. 1969.
31. Muntwyler, E. , Ray, C.B. , Myers, V. C. , and Sollmann, T.
Blood changes in victims of the Cleveland Clinic film disaster.
Am. Med. Assoc. J. 93:512-513 Aug. 17, 1929.
32. Norwood, W. D. , W'isehart, D. E. , Earl, C. A. , Adley, F. E. , and
Anderson, D. E. NOj poisoning due to metal-cutting with oxyacetylene
torch. J.Occup. Med. 8:301-306 June 1966.
33. Klein/eld, M. Acute pulmonary edema of chemical origin. Arch.
Environ. Health 10:942-946 June 1965.
34. Mliller, B. Nitrogen dioxide intoxication after a mining accident.
Respiration 26: 249-261 1969.
35. Crayson, R. R. Silage gas poisoning: NOj pneumonia, a new disease
in agricultural workers. Ann. Int. Med. 45:393-408 Sept. 1956.
36. Lowry, J. and Schuman, L. M. Silo-filler's disease: a newly
recognized syndrome caused by NOj inhalation with a report of
six cases. Univ. Minn. Med. Bull. 27:234-238 May 1, 1956.
37. Bils, R. F. and Romanovsky, J. C. Ultrastructural alterations of
alveolar tissue of mice. II. Synthetic photochemical smog. Arch.
Environ. Health 14:844-858 June 1967.
38. Buchberg, H. , Wilson, K. W. , Jones, M. H. , and Lindh, K.G.
Studies of interacting atmospheric variables and eye irritation
thresholds. Internal. J. Air and Water Pollution 7:257-280 June
1963.
39. Abe, M. Effects of mixed NO2-SO2 gas on human pulmonary
functions. Bull. Tokyo Med. Dental University 14:415-433 1967.
40. Emergency Exposure Limits recommended by the National Academy
of Sciences-National Academy of Engineering/National Research
Council Committee on Toxicology, for exposure of military and
space personnel. 1969.
41. Threshold Limit Values of Airborne Contaminants. Adopted by
ACGIH for 1969.
42. Elkine, H. B. Maximum acceptable concentrations; a comparison
in Russia and the United States. Arch. Environ. Health 2:45-49,
1961.
43. Maximum allowable concentration of NO^. American Standards
Assoc. 1962.
44. Short Term Limits for Airborne Contaminants. A Documentation.
Pennsylvania State Health Dept.
45. Report of working group meeting, enclosure: Limits for atmospheric
constituents in nuclear submarines. Working group for submarine
atmosphere requirements. Naval Ship Engineering Center.
March 8, 1967.
46. DRAFT - Recommended Ambient Air Quality Standards (Statewide
Standards Applicable to All California Air Basins) California
State Dept. of Public Health, March. 1969.
47. Thomas, H. V. , Mueller, P. K. and Wright, R. : Response of rat
lung mast cells to nitrogen dioxide inhalation. Air Poll. Cont.
Assoc., J. 17:33-35 Jan. 1967.
48. Freeman, C. , Crane, S. C. , and Furlosi, N. J. : Healing in rat lung
after subacute exposure to nitrogen dioxide. Am. Rev. of Resp.
Disease 100:662-676, 1969.
-------
49. Freeman, G. and Haydon, G. B. : Emphysema after low-level
exposure to NO2- Arch. Environ. Health 8:125-1Z8 Jan. 1964.
50. Haydon, G. B., Freeman, G. , and Furiosi, N.J.: Covert
pathogenesis of NO2 induced emphysema in the rat. Arch.
Environ. Health 11:776-783 Dec. 1965.
51. Freeman, G. , Furiosi, N.J., and Haydon, G. B. Effects of
continuous exposure of 0. 8 ppm NO2 on respiration of rats.
Arch. Environ. Health 13:454-456 Oct. 1966.
52. Freeman, G. , Stephens, R. J. , Crane, S.C., and Furiosi, N.J.:
L«SM>B of the lung in rats continuously exposed to two parts per
million of nitrogen dioxide. Arch. Environ. Health 17:181-192 Aug. 1968.
53. Freeman, G. , Crane, S.C., Stephens, R.J. , and Furiosi, N. J. :
The subacute nitrogen dioxide-induced lesion of the rat lung.
Arch. Environ. Health 18:609-612 April 1969.
54. Freeman, G. , Crane. S. C. , Stephens, R. J. , and Furioai, N. J. :
Environmental factors in emphysema and a model system with
NO2. Yale J. Biol. and Med. 40:566-575 April-June 1968.
55. Kleinerman, J. and Cowdrey, C. R. : The effects of continuous high
level nitrogen dioxide on hamsters. Yale J. Biol. and Med. 40:
579-585 April-June 1968.
56. Kleinerman, J. and Wright, G. W. : The reparative capacity of
animal lungs after exposure to various single and multiple doses
of nitrite. Am. Rev. Respiratory Dis. 83:423-424 March 1961.
57. Henry, M. C. , Findlay, J. , Spanker, J. , and Ehrlich, R. :Chronic
toxicity of NO2 in squirrel monkeys. UI. Effect on resistance to
bacterial and viral infection. Arch. Environ. Health 20:566-570
May 1970.
58. Lowrey, T. and Schuman, L. M. , "Silo-filler's disease" - A
syndrome caused by nitrogen dioxide. Am. Med. Assoc. J. 162:
153-160, Sept. 15, 1956.
59. Stokinger, H. E. , Mountain, J.T. , Scheel, L. D. Pharmacogenetics
in the detection of the worker hypersusceptible to industrial
chemicals. Ann. N. Y. Acad. Sci. 151:968-976 July 31, 1968.
60. Shy, C.M., Creason, J. P. , Pearlman, M. E. , McClatn, K. E. ,
Benson, F. B. , and Young, M. M. The Chattanooga school
children study: Effects of community exposure to nitrogen dioxide.
I. Methods, description of pollutant exposure, and results of
ventilatory function testing. Air Poll. Control Assoc. , J. 20:
539-545, Aug. 1970.
61. Shy, C.M. , Creason, J. P. , Pearlman, M. E. , McClain, K. E. ,
Benson, F. B. , and Young, M. M. The Chattanooga school
children study: Effects of community exposure to nitrogen dioxide.
II. Incidence of acute respiratory illness. Air Poll. Control
Assoc. J. 20:582-588, Sept. 1970.
62. von Nieding, G. , Wagner, M. , Krekeler, H. , Smidt, U. , and
Muysers, K. Absorption of NO2 in low concentrations in the
respiratory tract and its acute effects on lung function and circu-
lation. Presented at the Second International Clean Air Congress,
December 6-11, 1970, Washington. D. C.
63. Veninga, T. S. , Toxicity of Oj in comparison with ionizing radia-
tion, Strahlentherap. 134, 469 (1967).
64. Pflesser, G. , Die Bedentung des Stickstoffmonoxyds bei der
Vergiftung durch Nitrose Case, Arch. Exptl. Path. Pharmakol. ,
179, 545 (1935).
65. LaBell, C. W. , Long, J. E. , Christofano, E. E. Synergistic
effects of aerosols - particulars as carriers of toxic vapors.
Arch. Ind. Health 11:297 (1955).
66. Wagner, W. D. , Dobrogorski, O. J. , Stokinger, H. E. Antagonistic
action of oil mists on air pollutants. Arch. Environ. Health
2: 523 (1961).
67. Spicer, W.S. , Kerr, H. D. Effects of environment on respiratory
function. III. Weekly studies on young male adults.
Arch. Environ. Health 21:. 635 (1970).
68. Coffin, D. L. , Blommer, E. J. , Gardner, D. E. , Holzman, R. ,
Effect of air pollution on alteration of susceptibility to pulmonary
infection, Proc. 3rd Ann. Conf. on Atmospheric Contamination
in Confined Spaces, Dayton, Ohio, May 1967.
69. Elkins, H. B. , Nitrogen dioxide - rate of oxidation of nitric oxide
and its bearing on the nitrogen dioxide content of electric arc
fumes, J.Ind. Hyg. and Toxicol. 28: 37-39 1946.
-------
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Culdea for Short-Term Exposures of the Public to Air April 1. 1971
Pollutants I. Guide for Oxide* of Nitrogen *• fJGKitVtiaiJIm Coo.
'• (*u"1™"1
I. P«*ram« Or|»nliitlon Repl. No.
S. "iitiiniiln t1i||iioiti unit No.
The Committee on Toxicology of the National Academy of
Sciences - National 8«»e«rch Council rf. Cw&i&Gufil* '
2101 Constitution Avenue
Washington, D. C., 20416 • CPA 70-S7
1}. Sponwrlni Acnoy KM* •*:*••*>» .
Division of Health Effect* Research
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Durham, North Carolina 27701
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Guides for brief, intermittent exposure to nitrogen oxides have been com-
piled and presented. The oxides of greatest concern are nitric oxide,
nitrogen dioxide and nitrogen pentoxide. Toxicological data is presented
on these. Factors and conditions that can, modify and significantly alter
human response to nitrogen dioxide are discussed. The most "important ones
are; temperature, predisposing disease, heredity, age and, interactions to
other environmental pollutants. Values for short term exposure to N0_
are tabulated. Experimental data on humans and laboratory animals ex-
posed to NO" are Included in the appendices. ^
I
A1 '
H. fey lorti led tlnrpMa Anlytte. . Oualpton
Air pollution
Nitrogen dioxide
Nitrogen oxide
Nitrogen pentoxide
Toxl cology
Exposure
I7o. IOOTltfltn/Op«»eaMd Ttnm
Air pollution effects (humans)
Short-term Public Limits
Public Emergency Limits
It. Dlrtfculhxi SutMM
Unlimited
Public health
Standards
Laboratory animals
. «.J«u»>CI>u(Thi. Rwcrt 11. Ho. o) Patti
L UHCLAJSIFIEO 3A
f Jfl.UeuHtyBU»»,rrWiFi») II. Prlct
1 UNCLASSIFIED
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DISCLAIM*
This report *ss famished to the Air Poll'utlon
Control Office by
The CoaBlttee on Toxicology
of the
national Acsdeay of Sciences
National Resesrch Council
2101 Constitution Avenue
Washington, D. C. 20418
In fulfillment of Contract CPA 70-5? ' '
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