United States
Environmental Protection
Agency
Health Effects Research
Laboratory
Research Triangle Park NC 2771 1
v°/EPA
Research and Development
EPA-600/S1-81-044 July 1981
Project Summary
Effects of Sulfuric Acid
Mist Exposure on
Pulmonary Function
Steven M. Horvath, Lawrence J Folmsbee, and John F. Bedi
The effects of sulfuric acid particle
concentration (mass/volume), particle
size, and ambient temperatures on
pulmonary function of young male
nonsmokers were examined. Subjects
repeated three times a sequence of 20-
minute exercise (ventilation of approxi-
mately 30 l/min) and 20-minute sitting
rest. Pre- and post-exposure pulmonary
functions (forced vital capacity ma-
neuvers, lung volumes, maximum
voluntary ventilation, Raw TQV and
helium-oxygen FVC) were measured.
During the exposure and at the 5th
minute after cessation of each exercise
period, forced vital capacity tests (air
and helium-oxygen) were performed.
Each subject was exposed in random
order to filtered air or 233, 418 or 939
jug/m3 particulate sulfuric acid. Particle
sizes were MMD, 0.91 -0.93 fjm. geo-
metric SD, 1.66-1.73. Two subject
groups were studied in two different
ambient conditions, i.e. approximately
22°C dry bulb, 55% relative humidity,
and 35°C dry bulb, 85% relative hu-
midity. Sulfuric acid concentrations
were slightly higher during the hot
environmental exposures. No signifi-
cant changes in pulmonary functions
related to sulfate were observed in
subjects intermittently exercising in
the cool environment. Metabolic mea-
surements during exercise indicated a
trend towards increased ventilation
and oxygen uptake with duration of
exposure. The only significant differ-
ence which was related to sulfate
exposure was a higher respiratory rate
compared to filtered air. Heart rates
were similar under all conditions. In
the hot humid environment, forced
vital capacity decreased with time of
exposure but was not related to pol-
lutant exposure. The only significant
interaction for pollutants across time
was seen for FEF75%, where the post-
exposure values were greater than the
pre-exposure values under filtered air
conditions but not during sulfate
exposure. This observation was not
corroborated by changes in FEF75-
85%, which increased post-exposure
under all conditions. Three subjects
were studied during exposure to 14OO
fjg/m3. No changes were observed.
Predictable increases in heart rate,
rectal temperature, ventilation and
oxygen uptake were found but were
not related to sulfate exposure, being
simply the influence of the altered
ambient conditions. Exposure to sul-
furic acid mist in the 1 fjm particle size
range and in concentrations up to
1200 yug/m3 had relatively minor
effects on the cardiopulmonary system.
This report was submitted in ful-
fillment of Grant No. R804853 by the
Institute of Environmental Stress,
University of California, Santa Barbara,
under the sponsorship of the U.S.
Environmental Protection Agency.
This report covers a period from April
1, 1977 to August 31, 1980, and
work was completed as of August 31,
1980.
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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 fsee Project Report ordering
information at back).
Introduction
The increasing use of coal and petro-
leum products with high sulfur content
has raised concern about the potential
health effects of sulfur-containing air
pollutants. Early studies found that
humans exposed briefly (10-16 min) to
sulfuric acid concentrations of 0.35 to 5
mg/m3 and 4 to 40 mg/m3 (particle size
1 fjm) respectively, exhibited increased
coughing, altered respiratory patterns
and bronchoconstriction. However,
more recent studies again exposed
subjects briefly to 10, 100, and 1000
/jg/m3 to either sodium chloride or
sulf uric acid aerosols (0.1 to 0.2 fjm).
These 10-minute exposures of either
normal or asthmatic individuals did not
induce any alterations in pulmonary
functions. The effects on pulmonary
functions of intermittently exercising
subjects breathing sulfuric acid (75
jug/m3, particle size 0.48-0.81 /urn) were
investigated. No convincing adverse
short-term health effects were observed.
Ten subjects inhaled via nasal mask 0.5
/urn H2SO4 at 0, 100, 300 and 1000
fjg/m3 for one hour. Although no sig-
nificant changes in respiratory dynamics
were observed, bronchial mucociliary
clearance was altered. Respiratory
effects of sulfuric acid aerosol in normal
subjects exposed for four hours to 100
A/g/m3 H2SO4 of particle size 0.1 to 0.3
(jrr\ were evaluated. The subjects per-
formed two 15-minute bouts of exercise
during the exposure period. No signifi-
cant differences in pulmonary function
were observed during or after the expo-
sure. The conflicting results reported
could have been related to the size of the
aerosol particles utilized in the different
experimental situations.
We examined the effects of sulfuric
acid particle concentration (mass/vol-
ume) at an ambient temperature of
22°C and 55% relative humidity on
pulmonary function of young male
nonsmokers. All exposures were con-
ducted in an environmental chamber.
Eleven subjects thrice repeated a se-
quence of 20-minute exercise (ventila-
tion approximately 30 liters/min) and
20-minute sitting rest during the 2-hour
exposure. Pre- and post-exposure
pulmonary function tests (forced vital
capacity maneuvers, lung volumes,
maximum voluntary ventilation, Raw,
TGV, and helium-oxygen FVC) were
measured. During the exposure and at 2
minutes after cessation of each exercise
period, forced vital capacity tests (air
and helium-oxygen) were performed.
Each subject was exposed in random
order to filtered air or 233, 418, or 939
jug/m3 particulate sulfuric acid. Mass
median diameter (MMD) was 0.90-0.93
/jm, and geometric SD was 1.66-1.73.
Results
No major changes in pulmonaryfunc-
tion related to sulfate were observed in
these subjects (Tables 1 and 2). The only
measurement to show a significant
interaction across time (pre - post) and
sulfate concentration was FEVt o, which
was significantly decreased with expo-
sure to 939 fjg/m3 sulfate. The magni-
tude of the decrease was not considered
to be of physiological significance.
These results indicate that, even with
the added stress of the increased depth
and volume of ventilation associated
with exercise, exposure to as much as 1
mg/m3 of 1 /ym sulfuric acid aerosol for
2 hours has little if any effect on standard
tests of lung function. Many subjects
noticed a dry or metallic taste in the air.
At the highest concentration, throat
irritation or dryne'ss and cough were
frequently noted. Eye irritation was
reported by two subjects at 939 //g/m3
of sulfate. Several individuals reported
dizziness, fatigue, or headache, which
were usually associated with exercise
and had no relationship with sulfate
levels in the ambient air.
Discussion
These data indicate that there was no
significant effect of sulfuric acid aerosol
in the 1 -micron (0.9 fjm) size range and
in concentrations between 200 and
1000//g/m3 on the pulmonary function
of young male nonsmokers. The results
of the present study support previous
studies of human exposure to sulfuric
acid aerosols in the 0.3 to 0.5 fjm size
range at similar concentrations (100-
1000 fjg/m3). However, they do not con-
firm studies in which subjects were
exposed to larger aerosols. Subjects in
the study described herein were not
only exposed for longer periods; the
quantity of inhaled aerosol was inten-
tionally increased by having the subjects
exercise so that their ventilatory volumes
were intermittently increased up to 30
liters/ min. The increased prevalence of
symptoms such as cough, dry throat, or
throat irritation suggests that the sulfu-
ric acid may have caused some irritation
to the tracheal mucosa although not to a
sufficient degree to induce functional
changes. These symptoms were usually
noted only when the subject took a deep
or rapid inspiration and generally only at
the beginning of the exposure period.
Conclusions
It is apparent that additional investi-
gations involving long-term exposures
(rest and exercise combinations), small
and large particles, and various ambient
humidities need to be conducted. Some
attention must also be given to the mode
of administration. Chamber studies
which more closely simulate natural
environments are preferred, but the
interrelationship between such expo-
sures and those utilizing oral or a
combination of oral-nasal inhalation
require clarification.
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able 1 . Pulmonary Function
Exposures; Mean ±
Forced vital Pre
capacity (L) Post"
f£Vi o (U Pre
Post"
FEV3o(L) Pre
Posta
Inspiratory Pre
capacity (L) Post"
Expiratory Pre
res. vol. (L) Post
Funct. res. Pre
capacity (L) Post
FEF25-75% Pre
'L/s) Post
Max. volunt. Pre
vent. (L/min) Post
Airway res. Pre
'Us/cm HZ0) Post
FEF50% Pre
'L/s) Post
FEF75% Pre
'L/s) Post
FEF75-85% Pre
'L/s) Post
Measurements in Subjects Exposed to Various Concentrations of H2SOt (Pre & Post 2-Hour
SDJ
0 ug/m3
5.64 (±0.58)
5.58 (±0.56)
4.47 (±0.46)
4.7 9 (±0.48)
5. 58 (±0.59 )
5.55 (±0.57)
3.62 (±0.48)
3.48 (±0.45)
2.02 (±0.45)
2. JO (±0.45)
3.66 (±0.74)
3.73 (±0.72)
4.97 (±0.69)
5.06 (±0.81)
202 (±34)
205 (±33)
1.67 (±0.39)
J. 76 (±0.58)
5.57 (±0.77)
5. 63 (±1.03)
2.80 (±0.65)
2.93 (±0.80)
2. 12 (±0.59)
2. 22 (±1.02)
223 ug/m3
5. 65 (±0.55)
5. 54 (±0.63)
4. 83 (±0.54)
4.80 (±0.57)
5.61 (±0.57)
5.51 (±0.64)
3. 58 (±0.49)
3.49 (±0.58)
2. 02 (±0.36 )
2.05 (±0.38)
3. 68 (±0.73)
3.76 (±0.70)
5. 14 (±0.89)
5.36 (±1.11)
206 (±35)
202 (±41)
1.7 3 (±0.35)
1.77 (±0.57)
5.85 (±1.01)
6. 12 (±0.98)
2. 83 (±0.57)
3.05 (±0.90)
2. 20 (±0.54)
2. 32 (±0.7 2)
418 ug/m3
5.66 (±0.61)
5. 59 (±0.63)
4. 72 (±0.55)
4.76 (±0.55)
5.61 (±0.62)
5. 54 (±0.63)
3.61 (±0.55)
3. 49 (±0.46)
2.05 (±0.47)
2. 12 (±0.45)
3.72 (±0.69)
3. 80 (±0.7 6)
4.97 (±0.74)
5. 05 (±0.80)
199 (±35)
204 (±39)
1.75 (±0.52)
1.64 (±0.46)
5.97 (±0.85)
5. 84 (±0.96)
2. 83 (±0.68)
2. 88 (±0.77)
2.29 (±0.61)
2. 32 (±0.70)
939 ug/m3
5. 65 (±0.61)
5.47 (±0.60)
4. 82 (±0.57)
4.72 (±0.57)
5. 62 (±0.63)
5.44 (±0.57)
3. 54 (±0.50)
3.40 (±0.46)
2. 12 (±0.39)
2. 06 (±0.40)
3. 74 (±0. 74)
3.76 (±0.73)
5. 1 1 (±0.88)
5. 29 (±1.08 )
211 (±35)
209 (±32)
1.87 (±0.48)
1.69 (±0.41)
5.82 (±0.97)
5.81 (±1.15)
2.76 (±0.61)
2.89 (±0.7 3)
2. 13 (±0.68)
2.28 (±0.71)
"Post < Pre overall - no difference across sulfate concentrations.
Vre (FA, 418)< Pre (223, 939); Pre (939) > Post (939).
able 2. Pulmonary Function
Forced vital Pre
capacity (L) 25
65
105
FEVi o (L) Pre
25
65
JOS
FEV3.0 (L) Pre
25
65
105
Inspiratory Pre
capacity (L) 25
65
105
FEF25-75% Pre
(L/s) 25
65
JOS
Measurements During 2-Hour
0 ug/m3
5. 35 (±0.54)
5.21 (±0.6 1)
5. 24 (±0.62)
5. 16 (±0.62)
4. 65 (±0.49)
4. 48 (±0.54)
4.53(±O.58)
4.52 (±0.52)
5. 33 (±0.56)
5. 18 (±0.6 1)
5. 23 (±0.63)
5. 13 (±0.61)
3. 48 (±0.48)
3. 25 (±0.59)
3. 29 (±0.43)
3. 19 (±0.42)
4. 9 2 (±0.79)
4.7 3 (±0.83)
4.90 (±1.01)
5.05 (±0.83)
Exposure to HiSO*
223 ug/m3
5. 25 (±0.55)
5. 25 (±0.56)
5.21 (±0.56)
5.23 (±0.57)
4.53 (±0.51 )
4. 43 (±0.64)
4. 45 (±0.53)
4. 56 (±0.64)
5. 22 (±0.56)
5. 19 (±0.60)
5. 17 (±0.59)
5.20 (±0.54)
3.39 (±0.57)
3.23 (±0.58)
3. 32 (±0.55)
3. 36 f ±0.60)
4.91 (±0.83)
4.82 (±1.21)
5.1 3 (±1.05)
5.10 (±1.30)
(Mean ± SO)
418 ug/m3
5. 30 (±0.54)
5. 20 (±0.58)
5. 24 (±0.56)
5. 17 (±0.53)
4.51 (±0.57)
4.43 (±0.59)
4. 52 (±0.49)
4.53 (±0.53)
5. 28 (±0.55)
5. 12 (±0.59)
5. 19 (±0.56)
5. 14 (±0.54)
3.43 (±0.43)
3. 34 (±0.49)
3.31 (±0.49)
3.26 (±0.45)
4.75 (±0.97)
4.64 (±0.97)
4.81 (±0.89)
4.90 (±0.89)
939 ug/m3
5.28 (±0.59)
5. 20 (±0.59)
5. 17 (±0.61)
5. 13 (±0.62)
4.55 (±0.57)
4. 49 (±0.55)
4. 44 (±0.55)
4. 48 (±0.57)
5. 26 (±0.59)
5. 16 (±0.59)
5. 15 (±0.62)
5.10 (±0.20)
3. 43 (±0.54)
3. 29 (±0.46)
3.21 (±0.49)
3. 22 (±0.48)
4. 90 (±0.83)
4. 90 (±0.84)
4.84 (±0.95)
5.02 (±0.80)
* US GOVERNMENT PRINTING OFFICE 1901 -757-012/7226
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Table 2. (continued)
0 fjg/m3
223
418 tig/m3
939
FEF50%
(L/s)
FEF75%
(L/s)
Pre
25
65
105
Pre
25
65
105
4. 80 (±0.83)
4.73 (±0.81)
4.88 (±0.98)
5. 05 (±0.80)
2.53 (±0.61)
2.51 (±0.71)
2. 53 (±0.84)
2. 65 (±0.73)
4. 99 (±0.78)
4.76 (±1.1 4)
4. 98 (±0.84)
5. 03 (±1.08)
2. 66 (±0.70)
2. 50 (±0.65)
2. 64 (±0.77)
2.66 (±0.87)
4. 69 (±0.99 )
4. 54 (±0.94)
4. 76 (±0.91)
4. 8 3 (±0.93)
2. 40 (±0.74)
2. 49 (±0.84)
2. 47 (±0.72)
2.63 (±0.78)
4. 92 (±0.85)
5. 00 (±O.86)
4. 92 (±0.89)
5. 00 (±0.9 2)
2. 54 (±0.58)
2. 56 (±0.57)
2. 52 (±0.68)
2. 59 (±0.66)
Steven M. Horvath, Lawrence J. Folinsbee, and John F. Bedi are with the
Institute of Environmental Stress. University of California, Santa Barbara, CA
93106.
Donald H. Horstman is the EPA Project Officer (see below).
The complete report, entitled "Effects of Suit uric A cid Mist Exposure on Pulmon-
ary Function."(Order No. PB 81 -208 977; Cost: $9.50, 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 Project Officer can be contacted at:
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Fees Paid
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Penalty for Private Use $300
PS 0000 4? 9
u s tiW
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