EPA-800/1-77-032
June 1977
Environmental Health Effects Research Series
EFFECTS OF LOW LEVEL CARBON
MONOXIDE EXPOSURE
Blood Lipids and
Coagulation Parameters
Health Effects Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
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3 Ecological Research
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This report has been assigned to the ENVIRONMENTAL HEALTH EFFECTS RE-
SEARCH series. This series describes projects and studies relating to the toler-
ances of man for unhealthful substances or conditions. This work is generally
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studies. In addition to toxicology and other medical specialities, study areas in-
clude biomedical instrumentation and health research techniques utilizing ani-
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This document is available to the public through the National Technical Informa-
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EPA-600/1-77-032
June 1977
EFFECTS OF LOW LEVEL CARBON MONOXIDE EXPOSURE
Blood Lipids and Coagulation Parameters
K. M. Brinkhous, M.D.
Department of Pathology
University of North Carolina
Chapel Hill, North Carolina 27514
Contract No. 68-02-1281
Project Officer
Edward D. Haak, Jr.
Clinical Studies Division
Health Effects Research Laboratory
Research Triangle Park, N.C. 27711
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
HEALTH EFFECTS RESEARCH LABORATORY
RESEARCH TRIANGLE PARK, N.C. 27711
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DISCLAIMER
This report has been reviewed by the Health Effects Research
Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection
Agency, nor does mention of trade names or commercial products
constitute endorsement or recommendation for use.
ti
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FOREWORD
The many benefits of our modern, developing, industrial society are
accompanied by certain hazards. Careful assessment of the relative risk
of existing and new man-made environmental hazards is necessary for the
establishment of sound regulatory policy. These regulations serve to
enhance the quality of our environment in order to promote the public
health and welfare and the productive capacity of our Nation's population.
The Health Effects Research Laboratory, Research Triangle Park,
conducts a coordinated environmental health research program in toxicology,
epidemiology, and clinical studies using human volunteer subjects. These
studies address problems in air pollution, non-ionizing radiation,
environmental carcinogenesis and the toxicology of pesticides as well as
other chemical pollutants. The Laboratory develops and revises air quality
criteria documents on pollutants for which national ambient air quality
standards exist or are proposed, provides the data for registration of new
pesticides or proposed suspension of those already in use, conducts research
on hazardous and toxic materials, and is preparing the health basis for
non-ionizing radiation standards. Direct support to the regulatory function
of the Agency is provided in the form of expert testimony and preparation of
affidavits as well as expert advice to the Administrator to assure the
adequacy of health care and surveillance of persons having suffered imminent
and substantial endangerment of their health.
The report that follows is part of the Laboratory's research to
refine health information on exposure effects to pollutants for which
ambient air quality standards have been developed.
JoFm H. Knelson, M.D.
Director,
Health Effects Research Laboratory
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ABSTRACT
This study examined the effects of carbon monoxide (CO) in 50 and TOO
ppm doses on response to treadmill exercise, blood coagulation and blood
lipids in normal men. Twenty-three men were exposed to CO or to air in a
double-blind protocol. After exposure, each underwent a graded exercise
treadmill test which was terminated at 85% maximal heart rate. Blood for
measurement of carboxyhemoglobin (COHb), hematocrit, platelet count, prothrombin
time, partial thromboplastin time, thrombin time, fibrin split products, factor
VIII, platelet aggregation, serum cholesterol and triglycerides was drawn at
baseline, preexercise and postexercise. COHb did not change on air days but
reached a mean of 2.17% on 50 ppm days and 4.15% on 100 ppm days. The mean
duration of exercise was 19 sec shorter on CO days than on air days (f = 4.93).
The greatest effect was on 100 ppm days (f = 8.00). Coagulation parameters
and cholesterol and triglyceride measurements were not significantly affected
by CO exposure. Over the week of testing the cholesterol and triglyceride
levels fell significantly and exercise was regularly associated with increased
factor VIII activity. CO levels of 50 and 100 ppm significantly reduced the
duration of exercise to attainment of a target heart rate in normal men. No
effect of CO at these levels on coagulation parameters or on serum cholesterol
and triglycerides was detected.
IV
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INTRODUCTION
The goal of this study was to detect the effects of carbon monoxide
in 50 ppm and 100 ppm doses on response to treadmill exercise in normal young
men on certain parameters of blood coagulation and on blood lipids.
METHODS
Patient selection: Informed consent was obtained from all subjects.
Twnety-three men less than 38 years of age were included in the study. Each
was given a physical examination, and chest x-ray and electrocardiograms were
performed on every subject. Men with evidence of organic heart disease of
any kind were excluded from the study. Additionally, all subjects were asked
to refrain from cigarette smoking during the 12 hours before the beginning
of each exposure period. Each subject was shown to have normal hematocrit,
platelet count, prothrombin time, partial thromboplastin time, thrombin clotting
time and factor VIII levels.
Experimental protocol: (Fig. 1) Each subject was studied on weekday
mornings. Each fasted except for water during the 8 hours before the test
was performed. At the beginning of the day, blood was drawn for baseline
coagulation and lipid determinations. The subject then was exposed to air
with or without carbon monoxide via a closed system which included a tank of
gas with pressure regulators, a Douglas bag reservoir, and a tightly fitting
mask. The exposure period was 4 hours. On Monday and Friday mornings the
subjects were exposed to air only. Tuesday through Thursday the gas was air,
air with carbon monoxide (CO) at 50 ppm or air with CO at 100 ppm as determined
by one of the investigators. The physician, the technicians and the subject
were unaware of the content of the gas while the experiment was progressing
and when the electrocardiograms were analyzed.
-------
At the end of the 4 hours of exposure, blood was again drawn for
carboxyhemoglobin (COHb), coagulation factor and lipid analyses. The subject
was then asked to walk on a treadmill until 85% maximal heart rate had been
achieved. The treadmill was a programmed instrument set to advance at 3-minute
intervals from a speed of 2 mph to 10 mph and from no incline to an incline
of 16°. Heart rate was monitored by a Hewlett-Packard three-channel monitor
which recorded 12 leads of ECG at 1-minute intervals and by a telemetered
rate counter which computed the rate from the R-R interval. When the latter
instrument indicated that 85% maximal heart rate as determined by the standard
tables was reached, the time and stage of exercise were recorded and the
treadmill was stopped. The subject again donated blood for analysis and the
ECG was continued until the baseline heart rate was achieved. The ECG was
analyzed for heart rate and time. Each subject was used as his own control
from day to day and the Monday and Friday tests were included to document
any training effect.
Coagulation factor assays: Baseline blood samples were drawn at 8:00 a.m.
from both smokers and non-smokers prior to CO exposure. Samples were drawn
into heparin for COHb levels and into a si 1 iconized vacuum tube for blood
lipids and delivered immediately to the respective laboratories. The samples
for blood coagulation studies were handled as follows: blood was drawn into
3.2% sodium citrate at a ratio of 1:9 and immediately transported on ice to
the laboratory. Hematocrit tubes and red cell pipettes were prepared with
whole fresh blood. The hematocrit tubes were heparinized capillary tubes.
The hematocrit was immediately centrifuged on a microhematocrit centrifuge
for 5 minutes. Values were obtained by the scale method and recorded in
duplicate. One percent ammonium oxalate was used as platelet diluting fluid.
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Red cell pipettes containing the diluted blood sample were returned to the
coagulation laboratory and platelet counts were made by the method of Brecher,
et al (Am. J. Clin. Path., 23: 15-26, 1953).
The anticoagulated blood for coagulation analyses was spun in plastic
disposable tubes (17 x 100 mm) at 150 x g in an Adams Dynac centrifuge for
10 minutes at room temperature, and sufficient platelet-rich plasma (PRP) was
aspirated for platelet aggregation studies. This sample remained at room
temperature and the platelet aggregating assay was performed immediately.
The remaining plasma sample was re-mixed and re-centrifuged at 1500 x g in
the Adams Dynac centrifuge. The plasma was immediately aspirated, aliquoted,
labelled and frozen in a -70° refrigerator for other coagulation studies to
be performed at a later time.
Platelet aggregating assays were performed using a Payton Dual Channel
Aggregation Module and a Bausch & Lomb VO-5 Recorder. The PRP was added to
the cuvette (0.45 ml) and allowed to mix for 1 minute before serial dilutions
of 0.05 M epinephrine (Parke Davis Adrenalin Chloride Solution) were added.
Results were tabulated, charted and recorded.
The coagulation factor assays were done on the fresh frozen samples
several days later. The tests were performed using usual laboratory reagents
and Hyland Reference Plasma (Hyland Laboratories, Costa Mesa, California) as
a normal control.
For the prothrombin time (PT) plasma samples were removed from the -70°
refrigerator and thawed in a waterbath at 37°. Simplastin (General Diagnostics,
Morris Plains, N.J.) was placed in a test tube and into the waterbath. After
thawing, the plasma was removed and placed at room temperature. One tenth ml
of the plasma was added to a 10 x 75 mm disposable culture tube and incubated
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at 37° for 30 sec. At the end of this period, 0.2 ml of Simplastin was
added and the stopwatch started. The sample was immediately removed from
the waterbath and tilted until fibrin strands began to form. The test and
control samples were done in duplicate and recorded. The normal control
PT fell between 12 and 14 sec.
For the partial thromboplastin time (PTT), plasma samples were thawed
in the 37° waterbath. Test tubes of undiluted Thrombofax (Ortho Pharmaceutical,
Raritan, N.H.) and 0.02 M CaCl were placed in the waterbath. After thawing,
the plasma samples were held at room temperature. One tenth ml of plasma was
added to a 10 x 75 mm disposable culture tube and incubated for 60 sec at
37°. At the end of 60 sec, 0.1 ml of Thrombofax and 0.1 ml of 0.02 M CaCl
were added and the stopwatch started. The sample remained in the waterbath
for 45 sec before being removed and tilted. The test samples and reference
normals were done in duplicate and recorded. The normal clotting times fell
between 40 and 60 sec.
The thrombin clotting time (TCT) was performed at room temperature with
plasma which had been thawed-in a 37° waterbath. Two tenths ml of plasma was
added to a 10 x 75 mm disposable culture tube followed immediately by addition
of 0.2 ml of thrombin (10 units/ml) (Parke, Davis, and Co., Detroit, Michigan),
and the stopwatch was immediately started. This test along with the
reference normal was done in duplicate. The normal TCT ranged from 12 to
14 sec.
The plasma factor VIII (antihemophilic factor) assay was based upon
the observation that the PTT of hemophilic plasma is prolonged and the degree
of correction of this prolonged time is proportional to the factor VIII
concentration of the plasma sample added as test material. Hemophilic blood
-------
(substrate) was drawn from a patient with severe classic hemophilia Into
'•'£
3.2% sodium citrate at a ratio of 1:9. The plasma was prepared by spinning
the whole blood at 1500 x g for 10 minutes, RT. Hemophilia plasma samples
were aliquoted and frozen at -70°.
For the factor VIII assay, Thrombofax diluted 1:10 with normal saline
was used as the partial thromboplastin. Citrated saline was used as a
buffered diluting fluid and referred to as the human diluent. It was composed
of one part 0.2% normal saline, one part imidazole buffer (pH 7.2) and 0.4
part 3.2% trisodium citrate. Calcium was added to the system by means of
calcium-imidazole-saline (C-I-S) [1.4 parts of 1.2% CaCl and one part of 0.9%
saline were added to 1.2 parts imidazole buffer (pH 7.2)]. The plasma samples •
were activated with kaolin (Fisher Scientific Co., Fair Lawn, N.H.).
Test and hemophilic plasmas were thawed at 37°. Hyland reference plasma
was prepared following container directions. Serial dilutions of 10%, 5%,
2,.5% and 1.25% were made with both test and control plasmas. The plasmas
were mixed with 10 mg/ml kaolin, capped and incubated at room temperature
for 15 minutes, tilting every 2 minutes to keep the kaolin suspended. The
C-I-S mixture and the diluted Thrombofax were placed in test tubes, labelled
and incubated in the 37° waterbath. After a 15-minute waiting period, the
activated plasmas were placed on ice and left for at least 5 minutes before
starting the test. Determinations of the PTT's of the plasma samples began
with the 10% dilution of control followed by the 10% dilution of the test, etc.
All testing was done in duplicate.
Two tenths ml of plasma mixture was placed in a 37° waterbath in a 10 x 75 mm
tube and incubated for 30 sec. Upon completion of the 30 sec, 0.1 Thrombofax
and 0.1 ml C-I-S mixture were added and a stopwatch started. The tubes remained
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in the waterbath for 60 sec but were tilted after the first 30 sec. At
the end of 60 sec the tubes were removed and tilted until the fibrin formation
began. The stopwatch was stopped and times recorded when fibrin strands
were noted. The duplicate PTT's were averaged. Using semi logarithmic
paper, the plasma concentrations were plotted on the logarithmic scale against
the PTT's on the arithmetic scale. The control points were connected forming
a straight line. Factor VIII activity was calculated by comparing the
relative concentrations of normal and test plasmas at time points on the
parallel graphic lines.
Fibrin split products were assayed by a latex particle agglutination
method. Five ml of whole blood was drawn at baseline, preexercise and
postexercise and allowed to clot. EACA was present in the tube to prevent
fibrinolysis. The serum was allowed to» incubate at room temperature for
24 hours. At the. end of this period the sample was centrifuged and the
serum aspirated, aliquoted and frozen. At the time of testing the samples
were thawed and diluted with glycine saline buffer in serial dilutions from
1:1 - 1:64. Special glass slides obtained from Burroughs-Well come Co.,
Research Triangle Park, N.C., were for checking agglutination. One drop of
patient serum was placed on a glass slide and one drop of latex suspension
(Burroughs-Wellcome Co., Research Triangle Park, N.C.) added. The glass
slide was tilted back and forth checking for agglutinating particles.
Agglutination in samples diluted more than 1:8 was considered positive and
reported as the highest dilution at which agglutination occurred.
RESULTS
A total of 23 normal young men were studied. There were 15 men who
denied use of more than five cigarettes per day. This group will be referred
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to as nonsmokers. Eight subjects were smokers. These two groups of subjects
will for the most part be considered separately. In the group of nonsmokers
the mean age was 26.2 years with a median of 25 years and a range from 20 to
38 years. The smokers had a mean age of 24.25 years with a median of 26
years and a range of 20 to 33 years.
Carbon monoxide levels: Nonsmokers had baseline carboxyhemoglobin levels
which ranged from zero to 1.55% with a mean of 0.52%. The baseline levels
were not significantly different from day to day (Table 1).
On days when the nonsmoking subjects were exposed to air containing no
CO the COHb levels did not significantly change during the exposure period.
Immediately after the period of exposure to CO at 50 ppm the mean COHb level
in the nonsmokers.was 2.75 ± 0.90%. After exposure to 100 ppm the level in
nonsmokers was 4.72. ± 1.49%. The levels in nonsmokers after exercise on days
when exposure was.to air only were not significantly changed. Postexercise
levels on days when the subjects were exposed to 50 and 100 ppm had decreased
from preexercise values slightly to 2.53 ± 0.74% and 4.27 ± 1.21% respectively.
This slight decrease was statistically significant.
Smokers had a mean COHb at the baseline that was 1.06 units higher than
that of nonsmokers on the average (Table 2). After exposure to 50 ppm the
mean COHb level was 3.42 ± 0.94% and after 100 ppm it was 5.32 ± 1.23%. These
levels dropped slightly to 3.07 ± 0.79% and 5.04 ± 1.26% after exercise.
Table 3 shows the combined data on smokers and nonsmokers and indicates
the significantly increased levels of COHb on the CO exposure days. The
average increase in COHb from baseline to preexercise for the two CO days
was 3.16% more than for the three air days. On the 50 ppm day this increase
was 2.17% while on the 100 ppm day it was 4.15%. The 1.98% increase on the
100 ppm day over the 50 ppm day was significant.
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Exercise tolerance: Figure 4 shows the exercise tolerance in seconds
on the 5 days of the study for nonsmokers. The data concerning exercise
tolerance in smokers is shown in Figure 5. There was no significant difference
between smokers and nonsmokers with respect to time required to reach 85%
of predicted maximal heart rate.
Comparison of exercise tolerance on days when subjects were exposed to
CO with that on days when the exposure was to air only shows a significantly
shorter duration of exercise to achievement of 85% maximal heart rate on CO
days. On CO days the mean exercise time was 488 sec as compared with 507 sec
on air days. The difference between exercise times on air days and on days
with exposure to 50 ppm was not significant while that between air days and
CO days with 100 ppm was significant.
• Blood lipids: No differences in cholesterol levels"were noted to be
related to CO exposure (Table 6). There was, however, a significantly lower
level on Friday than on Monday. This difference was an average of 9 mg %.
The triglyceride level also fell by an average 17 mg % across the 5-day
period. No change in triglyceride levels could be related to CO exposure
(Table 7).
Blood coagulation parameters: Prothrombin times, partial thromboplastin
times, thrombin clotting times and fibrin split product titers were never
outside the range of normal and daily variation in our tests made it
impossible to correlate changes with exercise or presence or absence of carbon
monoxide in the inspired air.
Factor VIII; The factor VIII levels increased significantly from
preexercise to postexercise values (Table 8). There was, however, no
significantly greater increase on CO days than on air days. Although not
significant (p = 0.157) the difference between smokers and nonsmokers was
8
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rather large. The mean for smokers was 85.7% and the mean for nonsmokers
was 100.6%. This apparent difference deserves further study.
Hematocrvt: On the three air days, the mean hematocrit increased 0.8%
from preexercise to postexercise (Table 9). This increase was significant.
On the CO days, this increase was 0.9% which again was significant. There
was an increase of 1.3% on the 50 ppm day which makes it unlikely that an
effect of CO exposure on the differences in hematocrit levels before and
after exercise can be implied.
Platelet count: There was a large but not significant (p = 0.075)
difference between the platelet counts of smokers and nonsmokers. The
3 3
mean count for nonsmokers was 225,000/mm , that for smokers was 253,000/mm .
Additionally, there was significant increase in platelet counts in all groups
between the preexercise and postexercise sampling periods (Table 10). The
mean increase on the three air days was 15,300/mm , the increase on the 50
3
ppm day was an average of 37,000/mm and the increase on 100 ppm days was
3
19.300/mm . The difference between the increase on air days and the increase
3
on, the 50 ppm day, 22,500/mm , was significant.
Platelet aggregation studies were performed on 5 subjects. These
studies showed no effect of exercise or carbon monoxide on platelet aggre-
gation to ADP or epinephrine in our system.
DISCUSSION
The validity of this study is dependent to a great extent upon the
comparability of the study subjects and, therefore, is potentially threatened
by the presence among the study group of both smokers and nonsmokers.
Smokers, for instance, had an average baseline COHb level that was 1.06%
higher than that of the nonsmokers. Subsequent measurements were proportionally
-------
different between the smokers and nonsmokers. This problem has been signifi-
cantly abated, however, by the use of paired t analysis allowing comparison
of each variant in a single subject. Even though variability between subjects
prevented the description of an effect of smoking on the parameters measured,
within each subject there was measured an effect of carbon monoxide exposure
over and above that attributable to the smoking.
Carbon monoxide exposure primarily influenced exercise tolerance. A
significantly decreased time to attainment of 85% of maximal heart rate was
demonstrated on days when the subjects had been exposed to carbon monoxide.
The carboxyhemoglobin level at which this effect was noted was 4.93%. These
results are similar to those reported by others and imply that carbon monoxide
even in relatively small doses will decrease the peak work production of
normal young men. Of special note is a demonstrable effect of added CO in
smokers similar to that of nonsmokers.
These findings show a physiologic effect of carboxyhemoglobin at very
low levels. The effect is possibly related to an increased requirement for
peripheral blood, flow because of a decreased availability of oxygen for
respiration. The exact mechanism by which increased heart rate precipitated
by carbon monoxide exposure at a certain level of exertion is mediated is,
of course, unknown. The fact that such an effect can be measured at submaximal
exertion, however, implies that the workload to be met by the cardiovascular
system can be significantly augmented by even very small doses of carbon
monoxide.
To further characterize the physiologic effects of carbon monoxide,
blood lipids and coagulation measures were determined. The serum cholesterol
and triglyceride levels were not affected by exposure to carbon monoxide or
by sutanaximal exercise following carbon monoxide exposure.
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Previous studies on animals have shown increased serum cholesterol
levels after weeks of exposure to carbon monoxide. It has also been shown
that cigarette smokers have slightly higher cholesterol levels than do
nonsmokers. The fact that no change was observed in our subjects may mean
that CO has no hyperlipidemic effect in humans. More likely is the possibility
that such an effect cannot be demonstrated after an exposure period of only
4 hours and at levels as low as those used in this study.
To study the effects of carbon monoxide on the coagulation system we
chose to examine the routinely used clotting "screening tests" which include
prothrombin time, partial thromboplastin time, thrombin clotting time and
fibrin split products. Additionally, we examined the phase reactant and
"consumable" factor VIII because of its known variability in response to a
number of interventions. Specifically we wished to determine if the known
increase in plasma factor VIII levels caused by exercise would be augmented
by the. presence of carboxyhemoglobin. The screening tests showed no change
with either CO exposure or exercise. This result was related to the poor
sensitivity of the test procedure. It should be remembered for instance
that more than a 20% fall in a clotting factor is required before it can be
detected by the screening tests. Finally the use of screening tests to
measure "hypercoagulability" is unacceptable because of the known variability
among laboratories and the absence of consensus as to the definition of the
term "hypercoagulability". Therefore, there is no major alteration in the
clotting system attributable to short-term, low-dose carbon monoxide exposure.
Factor VIII assays, unlike screening assays, are relatively sensitive to
small changes in the plasma level of this factor. Additionally, the plasma
factor VIII is known to decrease rapidly in the face of intravascular coagulation
11
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and to increase with exercise, catacholanrine infusions or infection. This
study shows that chronic smoking is associated with a slight but not statisti-
cally significant decrease in factor VIII levels below the normal level. This
difference between smokers and nonsmokers has not been previously described
and deserves further study. There was a significant increase in factor VIII
levels between the preexercise period and the postexercise period as expected.
However, no difference was noted between the increases recorded on air days
and those which occurred on CO days. These studies do not rule out the
possibility that at higher doses of CO some effect on factor VIII might be
noted. They do indicate that no demonstrable effect occurs at levels which
are of interest to environmental planners.
Finally, an attempt was made to measure the effects of carbon monoxide
exposure and exercise on platelet function. Platelet counts were made on
each blood sample. There was a large but not statistically significant
difference between smokers and nonsmokers with the mean level among the smokers
being 28,000 platelets/mm higher. This difference has not been noted in the
past. There was a singificant increase in platelet counts between the
preexercise and postexercise measurements, but no reproducible effect of
carbon monoxide was noted. The low-dose and short-term of exposure to
carbon monoxide may have allowed potential effects on platelet concentration
to go undetected. There was, however, no marked effect demonstrated by this
study.
Platelet aggregometry was attempted on the first several study subjects.
The blood sample size, the need for collection of simultaneous control studies
and the long period of uninterrupted testing necessary to do these studies
prohibited the assay of this variable in all subjects. No effect on platelet
aggregation of either exercise or CO was detected.
12
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Study of patients with coronary heart disease was begun during the first
half of 1976. At that time two studies were completed. The second patient
suffered an episode of prolonged chest pain which required admission to the
coronary care unit. Because of this occurrence, the study was suspended
until the Protection of the Rights of Human Subjects authorization could be
reviewed and reevaluated. This review is presently in process.
In summary, these studies have demonstrated a dose-related increase
in heart rate with standardized exercise in normal young men. This effect
was noted at carboxyhemoglobin levels of 4% on the average which was accumu-
lated over a 4-hour period. The study was sound in that double-blind admini-
stration of air and air containing carbon monoxide prohibited the prejudicial
performance of subjects and the prior knowledge of investigators. Additionally,
the study was conducted over a 5-day period which allowed for the evaluation
of training effect. Simultaneous studies of blood lipids and coagulation-
screening tests as well as more sensitive measures of coagulation failed to
link changes in these parameters to the presence in the inspired air of
carbon monoxide. These results indicate that levels of carbon monoxide in
the atmosphere as low as 50 to 100 ppm limit the ability to perform submaximal
activity. There is, however, no detectable effect of carbon monoxide at
these levels on blood lipids or coagulation parameters. The possibility
that effects may exist after exposure to higher doses of carbon monoxide
for longer periods cannot be ruled out by our study.
13
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Figure 1. PROTOCOL
Gas Exposure: 4-hour exposure via closed face mask with subject sitting in a chair.
Day
Type
of
Exposure
Mon.
Tues.
clean
air
Wed.
clean
air
-Test for-
Training
Effect
Thurs,
Fri.
Randomized between
50 ppm in clean air &
100 ppm in clean air
clean
air
Typical Day:
8:00 a.m.--Basel
ine I—
4-Hour
Gas Exposure
EKG monitoring
EKG recordings
BP monitoring
Heart rate monitoring
Exercise time
•-- 12:00 Noon--Preexer,cise
Exercise
Test
Postexercise
Blood sample for:
1), COHb level
2) Blood lipids:
a. cholesterol
b. triglycerides
3) Blood clotting studies:
a. platelet function
b. Factor VIII level,
etc.
14
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Table 1
COHb (Nonsmokers)
Baseline
S.D.
Preexercise
S.D.
Postexercise
S.D.
Monday
0.47
0.54
0.31
0.36
0.48
0.29
X
0.64
0.47
0.70
0.42
0.61
0.41
Friday
0.52
0.30
0.51
0.32
0.62
0.31
50 ppm
0.54
0.47
2.75
0.90
2.53
0.74
100 ppi
0.52
0.46
4.72
1.49
4.27
1.21
15
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COHb (Smokers)
Table 2
Baseline
S.D.
Preexercise
S.D.
Postexercise
S.D.
Monday
2.06
1.50
1.51
0.88
1.38
0.95
2.18
0.87
1.65
0.59
1.47
0.72
Friday
2.28
0.97
1,70
0.90
1.51
0.65
50 ppm 100 ppm
1.88
1.13
3.42
0.94
3.07
0.79
1.82
0.80
5.32
1.23
5.04
1.26
16
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COHb (Combined)
Table 3
Baseline
Preexercise
Mean
S.D.
Mean
S.D.
Postexercise Mean
S.D.
Monday
1.02
1.22
0.72
0.82
0.79
0.73
1.17
0.97
1.03
0.66
0.91
0.67
Friday
1.07
0.99
0.93
0.81
0.93
0.62
50 ppm 100 ppm
1.00
0.99
2.98
0.95
2.72
0.78
0.97
0.86
4.93
1.40
4.54
1.25
17
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Table 4
Nonsmokers
iubject
J.W.
J.L.
G.W.
S.G.
N.W.
T.H.
S.R.
A.D.
B.Y.
M.P.
I.E.
I.E.
W.R.
C.S.
T.M.
Mean
Median
Age
31
29
38
24
22
29
20
23
24
20
30
22
25
26
30
26.2
25
Peak
H.R.
165
165
160
170
175
175
180
175
170
180
165
180
170
170
165
Mean
S.D.
Exercise Time (sec)
Mon
410
615
590
434
515
533
510
501
339
590
394
690
410
447
395
492
99
X
315
615
610
470
535
523
501
469
327
554
495
750
614
470
410
511
113
Fri
330
590
580
576
510
543
503
465
360
467
405
750
672
520
430
513
112
50 ppm
305
560
600
511
500
575
501
492
300
513
431
720
499
405
420
489
108
100 ppm
305
625
590
350
500
493
472
495
285
538
385
605
616
424
397
472
112
18
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Table 5
Smokers
Exercise Time (sec)
Subject
H.R.
J.H.
C.S.
VI. N.
D.F.
D.P.
C.K.
B.F.
Mean
Median
Age
33
22,
24- -
25
26
22
20
22
24.25
24
Peak
H.R.
165
180
170
(159-149)
170
180
180
180
Mean
S.D.
Air Days
Mon
470
—
315
529
577
594
617
517
112
X
505
435
310
405
531
544
760
499
141
Fri
512
435
300
480
558
605
780
524
149
CO Exposure Days
50 ppm
485
433
317
515
499
615
786
521
147
100 ppm
480
440
265
462
516
533
699
485
129
19
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Cholesterol
Table 6
Monday
Friday
50 ppm 100 ppm
Baseline
Preexercise
Postexercise Mean
Mean
S.D.
Mean
S.D.
Mean
S.D.
196
39
206
45
210
41
198
32
203
36
206
45
192
28
194
32
199
24
205
33
200
31
206
29
197
37
205
42
198
33
20
-------
Triglycerides
Table 7
Monday
Friday
50 ppm 100 ppm
Baseline
Preexercise
Postexercise Mean
Mean
S.D.
Mean
S.D.
Mean
S.D.
115
52
118
61
124
64
128
59
106
56
107
49
109
45
97
44
99
46
117
50
100
50
103
47
125
65
in
62
115
56
21
-------
Factor VIII
Table 8
Baseline
Preexercise
Mean
S.D.
Mean
S.D.
Postexercise Mean
S.D.
Monday
93
33
89
34
m
36
87
23
82
32
106
34
Friday
91
29
85
33
110
34
50 ppm 100 ppm
89
24
29
109
29
90
34
84
25
114
31
22
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Hematocrit
Table 9
Baseline
Preexerci.se
Mean
S.D.
Mean
S.D.
Postexercise Mean
S.D.
Monday
45.5
3.2
46.3
3.3
47.7
3.2
44.5
2.6
44.8
3.3
45.3
2.9
Friday
42.9
2.3
43.0
2.5
43.5
3.2
50 ppm 100 ppm
44.5
3.3
44.0
3.4
45.3
3.6
45.0
3.5
45.1
3.2
45.5
3.1
23
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Table 10
Platelet Count
3
(per mm in thousands)
Monday
Friday
50 ppm 100 ppm
Baseline
Preexercise
Postexercise Mean
Mean
S.D.
Mean
S.D.
Mean
S.D.
233
54
231
52
238
46
225
41
231
43
240
40
236
53
228
41
258
55
235
47
217
39
255
55
235
39
227
41
246
39
24
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT-NO.
'EPA3600/T*77-:032
3. RECIPIENT'S ACCESSIONTMO.
4.iT..ITL€ AND SUBTITLE
EFFECTS OF LOW LEVEL CARBON MONOXIDE EXPOSURE
Blood Li pids and Coagulation Parameters
5. REPORT DATE
June 1977
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
.K.' M?"Brinkhouse, M.D.
8. PERFORMING ORGANIZATION REPORT NO.
9. RERFORMINQ1ORGANIZATION NAME AND ADDRESS
cDepartment of Pathology
'.University ,of North Carol ina
iChapel••Hll.,1, N.C. 27514
10. PROGRAM ELEMENT NO.
1AA6Q1
11. CONTRACT/GRANT NO.
68-02-1281
1:2i:SPONSORING AGENCY NAME AND ADDRESS
.Healith" Effects Research Laboratory
fO'ff,ice 'ofyResearch and Development
.B.SJ! .Environmental Protection Agency
.:ResearcHi--Tp.iangle Park. N.C. 27711
13. TYPE OF REPORT AND PERIOD COVERED
RTP, NC
14. SPONSORING AGENCY CODE
EPA 600/11
15. SUPPLEMENTARY NOTES
16KABST\RACT
Thlhists'tudy examined the effects of carbon monoxide (CO) in 50 and 100 ppm doses
^orrar,esponse to. treadmill exercise, blood coagulation and blood lipids in normal men.
'Twentyrthree men were exposed to CO or to air in a double-blind protocol. After
^exposure?fieach underwent a graded exercise treadmill test which was terminated at
:i85feGma»iiiial- heart rate. Blood for measurement of carboxyhemoglobin (COHb), hematocrit
plateletccount, prothrombin time, partial thromboplastin time, thrombin time, fibrin
csp tit-products, factor VIII, platelet aggregation, serum cholesterol and triglycerides
:.wasirdrawai:at baseline, preexereise and postexercise. COHb did not change on air days
.teut.reached a-mean of 2:17% on 50 ppm days and 4.15% on 100 ppm days The mean
.duration;vof exercise was 19 sec shorter on CO days than on air days (f = 4 93) The
greatest-e-ffeet was on 100 ppm days (f = 8.00). Coagulation parameters and
xilol;este'r?ol and triglyceride measurements were not significantly affected by CO
f a target heart rate in normal men. No effect of CO at these levels
lonreo.agulation parameters or on serum cholesterol and triglycerides was detected.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
carbon-monoxide
bliood. coagulation
lipids
06, F
06, T
06, S
air.pollution
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