United Nations Environment Programme

Print Version

<<Back>> <<Next>>

Facts on Pollutants:



Carbon Monoxide (CO)

Carbon monoxide is a colourless, odourless and tasteless – but toxic – gas. CO is extremely dangerous if inhaled at high concentrations because it has a greater affinity than oxygen for red blood cells (haemoglobin). This means that CO replaces the oxygen carried in the blood, which quickly impairs functioning of the body’s organs, and can result in death.


Sources of CO:
Carbon monoxide (CO) is formed from incomplete combustion of fuels from motorised vehicles, blast furnaces, and waste incinerators. Tobacco smoking is also a significant indoor source of CO.


Human Health Effects of CO:
The health effects of CO result principally from its ability to attack haemoglobin and displace oxygen. This reduces the oxygen-carrying capacity of the blood because the normal function of haemoglobin is to transport O2 from the lungs to all body organs and tissues. Apart from acute death by choking from inhalation of high concentrations of CO, the long-term effects of exposure to lower CO concentrations in the air include impaired learning ability, drowsiness, disturbed sleep activity, increased risk of heart attacks (including those leading to sudden death), and reduced capacity for exercise and physical work.  


Environmental Effects of CO:
Exposure to very high levels of CO for an extended periods of time (115µg/m3 for 3 - 35 days) harms plant life. 


<<Back>> <<Next>>