About CO & COHb
What is Carbon Monoxide & Carboxyhemoglobin?
Carbon monoxide (CO) is a colorless, odorless gas produced through incomplete
combustion. CO is a poison that binds with hemoglobin, the oxygen-carrying molecule in
human blood. Because CO‟s affinity to bind with hemoglobin is 250 times greater than
oxygen, low airborne concentrations and long exposure times can result in substantial
carboxyhemoglobin (COHb) concentrations in the blood. COHb is CO bound to hemoglobin.
As COHb levels increase, less hemoglobin is available for the transport of oxygen. This lack
of oxygen-carrying capability, which is indicated by the increase in COHb, results in the
symptoms we associate with CO poisoning.
What are the Health Impacts
The acute health effects of CO exposure are well established. Mild exposure symptoms may
include headache, dizziness, decreased vigilance, decreased hand-eye coordination,
weakness, confusion, disorientation, lethargy, chest pain (in cardiac patients), nausea, and
visual disturbances. Greater or prolonged exposure can cause unconsciousness and death.
The severity of symptoms depends on the concentration of CO, length of exposure, and
degree of physical activity, as well as the state of health of the exposed individuals. People
who are exposed to high CO concentrations for long periods of time during strenuous
activity will reach the highest COHb levels.
Who are Sensitive Populations?
Age and general health may affect susceptibility to CO. Even low levels of CO can present a
health risk to susceptible individuals, such as persons with heart disease, sickle cell disease,
and anemia. Also, exposure to low levels of CO may harm the developing fetus.
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