vvEPA
United States
Environmental Protection
Agency
Health Effects Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S1-82-012 Sept. 1 982
Project Summary
Pulmonary Function and
Bronchial Reactivity in Human
Subjects with Exposure to
Ozone and Respirable
Sulfuric Acid Aerosol: An
Environmental Chamber Study
Thomas J. Kulle, H. David Kerr, Bernard P. Farrell, Larry R. Sauder, and David
L. Swift
A three-year chamber study of
human subjects is presented in two
phases: investigation of the effects of
sulfuric acid aerosol on pulmonary
function and a study of pulmonary
function and bronchial activity after
exposure to ozone and respirable
sulfuric acid aerosol.
In Phase I, sulfuric acid aerosol was
used to determine the respiratory
effects of low levels of sulfuric acid
aerosol such as those anticipated in
ambient air in the near future. Twenty-
eight normal subjects were exposed
for 4 hours to 98 /ug/m3, 0.14 //m Hb
SCh aerosol in an environmentally-
controlled exposure chamber. Of the
28 subjects, equal numbers were
nonsmokers and cigarette smokers.
None of the subjects complained of
symptoms attributable to the expo-
sure. Measurements of pulmonary
function were obtained 2 hours into
the exposure, immediately following
exposure, and 2 and 24 hours post-
exposure. These measurements were
compared with control values obtained
at comparable hours on the previous
day when the subjects breathed
filtered clean air. No significant
differences in pulmonary function
were observed during the exposure,
immediately after exposure, or 2 and
24 hours post-exposure.
Phase II used ozone and sulfuric
acid aerosol. Studies of recent air
pollution episodes in the U.S. and
Southern England have shown atmos-
pheric co-existence of ozone (Os) and
H2SO4 aerosol. Previous exposure of
human subjects to low levels of these
pollutants (0.3 ppm Oa and 98/^g/m3,
0.14 fjm H2SO4 aerosol), as separate
exposures, produced no significant
changes in pulmonary function. Single
Os exposures to slightly higher levels
(0.4-0.5 ppm) have produced decre-
ments in pulmonary function. Repeat-
ing this ozone exposure on the follow-
ing day results in a greater decrement
in function occurring on the second
day, suggesting an effect of the
previous exposure on a subsequent
exposure. To determine if an Os pre-
exposure around "threshold" would
produce a significant decrement in
function with this H2SO
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SO* aerosol for 4 hours. Separate
exposures to O3 and H2SO4 were also
done. Three consecutive weeks were
employed, one each for Os, HaSO-t,
and O3 with H2SO4. In each week
three consecutive days represented
control, exposure, and post-exposure
days. Pulmonary function (body plethy-
smography and spirometry) and bron-
chial reactivity to methacholine were
measured following exposure and 24
hours post-exposure, and compared
to control clean-air values. No signifi-
cant changes in pulmonary function or
bronchial reactivity were observed
with the ozone, the sulfuric acid
aerosol or the sequential ozone-
sulf uric acid aerosol exposures. Ozone
pre-exposure does not appear to
enhance the response to respirable H2-
SO4 aerosol at or near environmen-
tally-observed levels.
This Project Summary was developed
by EPA's Health Effects Research
Laboratory, Research Triangle Park,
NC, to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
This report presents the research
results associated with a study funded by
the Environmental Protection Agency
under Grant Number R803804. The
three-year work effort using the Univer-
sity of Maryland Environmental Cham-
ber, consisted of two phases Phase I
investigated the "Effects of Sulfuric
Acid Aerosol on Pulmonary Function in
Human Subjects " Phase II studied
"Pulmonary Function and Bronchial
Reactivity in Human Subjects with
Exposure to Ozone and Respirable
Sulfuric Acid Aerosol."
Sulfuric Acid Aerosol —
Phases I and II
Atmospheric sulfur dioxide (S02) is
oxidized to sulfur trioxide (SOa) which
combines immediately with water vapor
to form H2S04 in the form of droplets.
Cox and Penkett have shown in labora-
tory experiments that when the photo-
chemical smog reaction, involving
unsaturated hydrocarbons (RH) and
oxides of nitrogen (NOX), takes place in
the presence of SO2, oxidation of the
S02 to H2SO4 occurs at a significant
rate, even when the concentrations of
RH and NO* were typical of the levels (~
0.1 ppm) during moderate pollution
episodes.
Sulfuric acid mist has been suggested
as one of the irritants contributing to the
increased mortality and morbidity
resulting from the prolonged polluted
fogs of Donora, London, and the Meuse
Valley. Catalytic converters presently
installed on automobiles to control
pollution may become a source of
increased sulfates and sulfuric acid
mist in the breathing zone of pedestrians
and motorists in urban areas. Sulfuric
acid has been shown to be more toxic
than sulfur dioxide in animal and
human studies, with the acid particle
size and relative humidity affecting
toxicity.
Past measurements (1961) of urban
atmospheric levels of sulfuric acid mist
in the United States (Los Angeles) show
levels up to 50 /ug/m3 for a 3-hour
period With the increased use of high
sulfur fuels for combustion and the
more widespread use of catalytic-
converter equipped automobiles, the
peak urban atmospheric burden of H2-
SO4 aerosol of 20 fjg/m3, estimated by
EPA in 1976, could possibly increase to
60-80 /jg/m3. EPA air quality data
reported 24-hour sulfate levels of 1 62
/ug/m3m South Charles, West Virginia in
1973. Air quality data on 2-4 hour
sulfate measurements as well as H2S04
aerosol determinations have not been
made. Independent researchers have
made limited measurements of both the
24-hour sulfate and peak 2-hour sulfate
levels Based on Cass's measurements
in the Los Angeles area of peak 2-hour
levels being approximately 175% higher
than the 24-hour averages, the above
24-hour sulfate level could have 2-hour
peak levels of 280 /jg/m3.
Animal studies have revealed adverse
pulmonary function effects to various
levels of H2S04 aerosol Previous
studies showed this effect at concentra-
tions ^2000 fjg/m3. Recently, Amdur
exposed guinea pigs for one hour to
concentrations from 100 to 1000/ug/m3
at particle sizes of 0.3 and 1 0/um All
exposures produced a significant increase
in pulmonary flow resistance, which
was dose-related. Pulmonary compliance
decreased for all exposures, but was not
significant for the 100 and 400 /ug/m3,
1.0 fjm exposures.
Amdur et al. reported adverse effects
(decreased flow rates) in human subjects
exposed by face mask to relatively high
concentrations of H2S04 mist (350-500
/ug/m3 of 1 fjm particle size for 5-15
minutes). Sim and Pattle reported
symptoms of respiratory tract irritation
and increased airway resistance in
human subjects exposed to high con-
centrations of H2SO4 acid mist (^3000
/ug/m3, 1 /urn for 10 minutes) in high
humidity (90% RH).
More recently, Gardner et al. exposed
healthy nonsmoking human subjects
for 2 hours to 66, 100, or 195 /jg/m3,
0055 A/m MMD H2SO4 aerosol. The
subjects exposed to the lowest concen-
tration seemed to be the most sensitive,
with significant decreases in FEV2 and
Raw and an increase in FRC. The group
exposed to 100 /ug/m3 showed signifi-
cant changes in FEV2 and Raw, with no
significant changes in pulmonary
function associated with the subjects
exposed to the highest concentration.
No significant changes in respiratory
rate or tidal volume were observed in
this latter group
Avol et al reported no effects on
pulmonary function in healthy, normal
humans and subjects with asthma
following exposure to 100 /ug/m3 H2-
S0
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chemical pollution described as the
worst Southern California smog seige
m 25 years, with one-hour average
concentrations of ozone exceeding 0 4
ppm and eight consecutive days with
Stage II ozone (^ 0.35 ppm) episodes in
the South Coast air Basin
Ozone, the major oxidant in photo-
chemical smog, is a respiratory irritant
that has been shown to produce
decrements in pulmonary function
following low level exposure (0 4-0 5
ppm) Kerr et al. found significant
reductions in forced vital capacity (FVC)
and specif ic airway conductance (SGaw),
and increased total pulmonary resistance
(Ri_) following exposure to 0 5 ppm for 6
to 10 hours. Farrell et al found
significant reductions in FVC and SGaw
following exposure to 0.4 ppm ozone for
3 hours Animal studies had previously
revealed the phenomenon of tolerance
to the respiratory effects of ozone with
repeated exposure More recently this
phenomenon of adaptation was demon-
strated in human subjects In a study by
Hackney et al 5 to 6 subjects, exposed
to 0 5 ppm for 2 hours per day for 4
consecutive days, showed decreases in
pulmonary function on days 1, 2, and 3
that were largely reversed by the fourth
day Farrell et al demonstrated that
when nonsmoking human subjects
were exposed to 0 4 ppm ozone for 3
hours per day for 5 consecutive days,
decrements in FVC and SGaw occurred
on the first two days, which returned to
baseline levels by the fifth day despite
continued exposure. Folmsbee and co-
workers showed that repeated 2-hour
exposures to ozone at 0.20 ppm produced
no acute effects in pulmonary function,
whereas, 2-hour exposures to 0 35 and
0.50 ppm repeated over 3 days produced
significant changes in FVC, FEVi, FEF2s-
75%. In all these human studies, the
maximum decrement in function occurred
on the second day of ozone exposure,
indicating that there may be some
enhancement of sensitivity from the
initial ozone exposure. Symptoms
generally correlated with decrements in
pulmonary function
Increased bronchial reactivity, as
measured by the response to histamme
inhalation, has been demonstrated
following exposure of normal nonsmok-
ing subjects to 0 6 ppm Oa for 2 hours,
this exposure produced no significant
changes in baseline airway resistance
(Raw), suggesting that bronchial reac-
tivity may be a more sensitive indicator
than pulmonary function of changes in
the airways following O3 exposure The
reactivity increase occurred immediately
following Oa exposure, becoming non-
significant by 24 hours post-exposure
In another study performed in their
laboratory, nonatopic and atopic non-
smokers were also exposed to 0.6 ppm
Os for 2 hours. In the nonatopic group,
the increase in specific airway resistance
(SRaw) produced by either histamme or
methacholme aerosol after Oa exposure
was significantly greater than after the
sham (air) exposure. For the atopic
group inhaling histamme aerosol only,
the SRaw increase following Os expo-
sure was also significantly greater In
each group, bronchial response was
measured one hour after Os exposure,
the observed increase returning to
control 24 hours post-exposure. Baseline
SRaw did not change significantly with
Oa exposure In both studies subjects
were exposed while wearing nose clips,
restricting 03 exposure to oral inhalation
only. Although these studies did not
showa significant change in pulmonary
function (Raw, SRaw), other studies
have demonstrated significant decre-
ments m pulmonary function with
exposures to 04-05 ppm Os for 2-3
hours.
Sulfuric Acid Aerosol with
Ozone Pre-Exposure — Phase
II
Recent air pollution episode studies
performed from 1975 through 1977 in
the eastern half of the U S from the
Great Lakes through the TVA region
showed the co-existence of elevated
ground-level concentrations of partic-
ulate sulfate and ozone as a regional
and interstate phenomenon Maximum
concentrations were >0 14 ppm ozone
and 40 /7g/m3 sulfate.
During July 1971, over Southern
England significantly higher than
normal concentrations of ozone as well
as oxidized sulfur dioxide in the form of
sulfunc acid and sulfates were measured
at ground levels Total sulfate reached
levels of 70 fjg/m3, with the hydrogen
ion concentrations expressed as H2SO4
aerosol peaking at 55 yug/m3 Maximum
Oa levels were 010 ppm A close
correspondence in concentration pattern
and peaking occurred with the Oa and
H2S04 levels, the H2SO4 aerosol also
peaked at a lower level earlier m the day
when the 03 concentration was building
up
Previous investigators have studied
the combined exposure to ozone and
sulfunc acid aerosol, sulfur dioxide or
ambient total suspended particulate
Using a mobile laboratory m Los
Angeles County during the summer of
1978, Linn et al. demonstrated signifi-
cant but very small losses in forced
expiratory volumes and flows and total
lung capacity with very mild clinical
symptoms m "allergic" normal and
asthmatic subjects exposed to ambient
LA air of 022 ppm ozone and 200
/ug/m3 total suspended particulate The
H2S04 concentration was not deter-
mined Bedi et al. exposed nine young
adult males to 0 40 ppm SOa, 0 40 ppm
Oa, and their combination, each for a 2-
hour duration When exposed to SO2
alone, no significant changes occurred
in pulmonary function, whereas expo-
sure to 03 or Oa plus SOa produced
significant decreases in forced expira-
tory volumes and maximum expiratory
flows Responses between Oa alone
and Oa plus SO2 were not significantly
different, thus a synergistic effect was
not demonstrated
Klemman et al exposed normal
human subjects for 2 hours to 0 37 ppm
03, 0 37 ppm SO2, and 100jug/m3,0.5^m
H2S04 aerosol The combined exposure
showed small statistically significant
decrements in forced expiratory function
(volumes and flows) The increase in
reported symptoms with exposure
approached statistical significance The
authors stated that the results did not
support the hypothesis that H2SO4
aerosol markedly enhances respiratory
irritance of other pollutants (Oa, S02),
although, a modest degree of enhance-
ment may have occurred compared to
previous ozone exposure data
Last and Cross exposed normal ratsto
04-0 5 ppm 03, llOO/jg/m^Ob/jmHz-
S04 aerosol, and their combination for 3
and 14 days. Exposure effects were
evaluated on conducting airway metab-
olism as rate of secretion of mucus
glycoprotems by tracheal explants and
on biochemical parameters in lung
homogenates The authors stated that
true synergism was observed m that the
responses to the mixture of Ojand H2SO4
aerosol exceeded the sum of the effects
observed with the same concentration
of Oa and H2S04 presented separately
Gardner et al. exposed female mice to
900fjg/m3, 0 23 /urn H2 S04 aerosol and
0 1 ppm ozone for 2 and 3 hours
respectively, using an mfectivity model
for evaluating exposure effects Neither
pollutant alone caused a significant
increase in mortality with the infectious
microorganism challenge as compared
to filtered air controls With sequential
exposures to the two pollutants, only
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when the exposure to the oxidant gas
immediately preceded that of the acid
(not the acid preceding the ozone) was
there a significant increase in respiratory
infections, with the observed increased
mortality equal to the additive effect of
the individual pollutants A significant
decrease in tracheal ciliary activity of
hamsters was observed with the same
sequential exposure to 63 followed by
H2SO4 as compared to the decrease
(significant) observed with the H2SO4
exposure alone, the Oa exposure alone
resulted in no significant difference
from air controls An additional experi-
ment was conducted using 0.1 ppm Oa
and 500 jjg/m3 H2SO4 aerosol admin-
istered simultaneously for a period of 3
hours to female mice, also employing
the infectivity model A significant
increase in mortality over air controls
was observed, with the acid alone
showing no increase and the ozone, a
nonsignificant increase in mortality.
As noted in the previous section,
ozone appears to have the capability of
producing a further decrease in pulmo-
nary function with a second exposure A
pre-exposure to this pollutant might
have the potential of magnifying the
response to respirable sulfuric acid
aerosol exposure Both sulfuric acid
aerosol and ozone are pulmonary
irritants
The purpose of the Phase II investiga-
tion was to determine if pre-exposure to
ozone at a level seen in the urban
environment would produce a signifi-
cant decrement in pulmonary function
with an H2SC>4 aerosol exposure previously
shown not to decrease function Con-
centrations used were 0 3 ppm ozone
and 100 /jg/m3, 0 13 Aim sulfuric acid
aerosol for 2 and 4 hours, respectively
In addition, bronchial reactivity to
inhaled methacholine was determined;
these measurements appear notto have
been made in any published studies
Conclusions
Phase I — Sulfuric Acid
Aerosol
Single short-term (4-hour) exposure
to low levels of respirable sulfuric acid
aerosol (98 /ug/m3 of particle size 0.14
/urn) with two 15-mmute light-to-
moderate exercise periods appears to
have no adverse effects on pulmonary
function in normal human subjects.
Phase II — Ozone and
Sulfuric Acid Aerosol
Single short-term exposure to 0 3
ppm ozone for 2 hours with one 15-
mmute light-to-moderate exercise
period showed no significant changes
in pulmonary function or bronchial
reactivity to methacholine in normal,
nonsmoking human subjects Exposure
to respirable sulfuric acid aerosol (100
jug/m3, 0.13^m H2S04 for 4 hours) with
the same light-to-moderate exercise
also demonstrated no significant changes
in pulmonary function or bronchial
reactivity When the H2SO4 aerosol
exposure was preceded by the Os
exposure, no significant changes were
seen in pulmonary function or bronchial
reactivity We conclude that there are
no readily apparent risks from sequential
exposures of nonsmokers to these low
levels of ozone and sulfuric acid aerosol
at this exercise level.
Recommendations
Phase I — Sulfuric Acid
Aerosol
No significant changes in pulmonary
function were evident with this study,
but longer or repeated exposures may
produce function decrements. Exacer-
bations of chronic bronchitis are known
to occur with exposure to high ambient
levels of S02 and particulates, of which
HaSCU aerosol is a constituent.
Further studies should be undertaken
to 1) evaluate the effects of longer or
repeated exposures to H2S04 aerosol;
2) evaluate the effects of H2SC>4 aerosol
on subjects with allergy, asthma and/or
chronic bronchitis; 3) evaluate the
effects of combinations of H2S04 and
other constituents of the S02/particulate
complex on both normal subjects and
subjects with allergy, asthma and/or
chronic bronchitis. Investigation of the
effects to higher H2SC>4 concentrations
would appear to have little relevance to
the effects of air pollution, unless
ambient levels increase markedly in the
future
Phase II — Ozone and
Sulfuric Acid Aerosol
In normal, nonsmoking human sub-
jects, no significant changes in pul-
monary function were observed with
individual or sequential exposures to
0.3 ppm 03 for 2 hours and 100/ug/m3,
013 /jm H2S04 aerosol for 4 hours
employing light-to-moderate exercise
loads Bronchial reactivity to metha-
choline did not show a significant
increase with any exposure; although, a
substantial, nearly significant decrease
occurred following the 4-hour exposure
to respirable sulfuric acid aerosol.
Additional studies should be under-
taken to: 1 (evaluate the effects of ozone
and respirable H2SO4 aerosol on subjects
with allergy, asthma and/or chronic
bronchitis; 2) further evaluate the
decrease in bronchial reactivity to
methacholine following exposure to
respirable H2SO4 aerosol, i.e. expose
additional subjects to 4 hours of 100
fjg/m3, 0.1 -0 3 /urn H2S04 aerosol; and
3) evaluate the effects of these two air
pollutants employing moderate-to-
heavy exercise loads.
Thomas J. Kulle, H. David Kerr, Bernard P. Farrell, and Larry R. Sauder are with
the University of Maryland School of Medicine, Baltimore, MD 21201; David L.
Swift is with Johns Hopkins University, Baltimore, MD 21205.
Edward D. Haak. Jr., was the EPA Protect Officer (for current contact, see
below).
The complete report, entitled "Pulmonary Function and Bronchial Reactivity in
Human Subjects with Exposure to Ozone and Respirable Sulfuric Acid
A erosol: An Environmental Chamber Study, "(Order No. PB 82-255 126; Cost:
$15.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA contact, W. F. McDonnell, can be contacted at:
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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Environmental Protection
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