Carbon
Monoxide
From:
Health Problems Caused By Other Combustion
Products
(Stoves, Space Heaters,
Furnaces, Fireplaces)
Co-sponsored by:
The American Lung Association (ALA),
The Environmental Protection Agency (EPA),
The Consumer Product Safety Commission (CPSC), and
The American Medical Association (AMA)
U.S. Gov't Printing Office Publication No. 1994-523-217/81322
1994
Carbon monoxide is an
asphyxiant. An accumulation of this odorless, colorless gas may result in
a varied constellation of symptoms deriving from the compound's affinity
for and combination with hemoglobin, forming carboxyhemoglobin (COHb) and
disrupting oxygen transport. The elderly, the fetus, and persons with
cardiovascular and pulmonary diseases are particularly sensitive to
elevated CO levels. Methylene chloride, found in some common household
products, such as paint strippers, can be metabolized to form carbon
monoxide which combines with hemoglobin to form COHb. The following chart
shows the relationship between CO concentrations and COHb levels in blood.
Tissues with the highest oxygen needs -- myocardium,
brain, and exercising muscle -- are the first affected. Symptoms may mimic
influenza and include fatigue, headache, dizziness, nausea and vomiting,
cognitive impairment, and tachycardia. Retinal hemorrhage on funduscopic
examination is an important diagnostic sign, but COHb must be
present before this finding can be made, and the diagnosis is not
exclusive. Studies involving controlled exposure have also shown that CO
exposure shortens time to the onset of angina in exercising individuals
with ischemic heart disease and decreases exercise tolerance in those with
chronic obstructive pulmonary disease (COPD).
Note: Since CO poisoning can mimic influenza, the health
care provider should be suspicious when an entire family exhibits such
symptoms at the start of the heating season and symptoms persist with
medical treatment and time.
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Relationship between
carbon monoxide (CO) concentrations
and carboxyhemoglobin (COHb)
levels in blood
Predicted COHb levels resulting from 1- and 8-hour exposures
to carbon monoxide at rest (10 l/min) and with light exercise (20
l/min) are based on the Coburn-Foster-Kane equation using the
following assumed parameters for nonsmoking adults: altitude = 0
ft; initial COHb level = 0.5%; Haldane constant = 218; blood
volume = 5.5 l; hemoglobin level = 15 g/100ml; lung diffusivity =
30 ml/torr/min; endogenous rate = 0.007 ml/min.
Source: Raub, J.A. and Grant, L.D. 1989. "Critical health
issues associated with review of the scientific criteria for
carbon monoxide." Presented at the 82nd Annual Meeting of the
Air Waste Management Association. June 25-30. Anaheim, CA. Paper
No. 89.54.1, Used with permission. |
Carboxyhemoglobin levels and related health effects
| % COHb in blood |
Effects Assocated with this COHb
Level |
| 80 |
Deatha |
| 60 |
Loss of consciousness; death if
exposure continuesa |
| 40 |
Confusion; collapse on exercisea |
| 30 |
Headache; fatigue; impaired judgementa |
| 7-20 |
Statistically significant decreased
maximal oxygen consumption during strenuous exercise in healthy
young menb |
| 5-17 |
Statistically significant diminution
of visual perception, manual dexterity, ability to learn, or
performance in complex sensorimotor tasks (such as driving)b |
| 5-5.5 |
Statistically significant decreased
maximal oxygen consumption and exercise time during strenuous
exercise in young healthy menb |
| Below 5 |
No statistically significant vigilance
decrements after exposure to COb |
| 2.9-4.5 |
Statistically significant decreased
exercise capacity (i.e., shortened duration of exercise before
onset of pain) in patients with angina pectoris and increased
duration of angina attacksb |
| 2.3-4.3 |
Statistically significant decreased
(about 3-7%) work time to exhaustion in exercising healthy menb |
SOURCE: aU.S. EPA (1979); bU.S. EPA
(1985)
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