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Environmental Sources
Carbon monoxide, or CO, is a colourless, odourless gas that is formed
when carbon in fuel is not burned completely. Petrol and diesel
vehicles emit Carbon Monoxide. Peak CO concentrations typically
occur during colder months of the year when CO from motor
vehicle emissions are greater and night inversion conditions
(where air pollutants are trapped near the ground beneath
a layer of warm air) are frequent. Other large sources of
CO emissions include industrial processes (such as petroleum
refining and paper manufacturing).
Human Health effects
High levels of CO are poisonous even to healthy people. It can affect
people with heart disease and can affect the central nervous system. Carbon
monoxide can cause harmful health effects by reducing oxygen delivery
to the body's organs (like the heart and brain) and tissues. The health
threat from lower levels of CO is most serious for those who suffer from
heart disease, like angina, clogged arteries, or congestive heart failure.
For a person with heart disease, a single exposure to CO at low levels
may cause chest pain and reduce that person's ability to exercise; repeated
exposures may contribute to other cardiovascular effects. People who breathe
high levels of CO can develop vision problems, reduced ability to work
or learn, reduced manual dexterity, and difficulty performing complex
tasks. At extremely high levels, CO is poisonous and can cause death.
Exposure limits
- The United States EPA’s National Ambient
Air Quality Standards (US NAAQS) has set an air quality standard of 35
ppb for a 1-hour (short term) average carbon monoxide concentration and
9 ppb for a short term 8 hour average.
- The WHO has a short term guideline limit
of 87328 ppb (15 minute average) & 52397 (30 minute average), 26198
ppb 1 hour average and 8733 ppb 8 hour average.
- The US Occupational Safety and Health
Administration (OSHA) has set a permissible exposure limit of 55 milligrams
of carbon monoxide per cubic meter of air (55 mg/m3) or 50
ppm for an 8-hour workday in a 40-hour workweek.
- The US National Institute for Occupational
Safety and Health (NIOSH) recommends a threshold limit value (TLV), 8-hour
time weighted average (TWA), of 35 ppm or 40 mg/m3 for CO.
Sources & Links:
www.epa.gov/air/urbanair/co/what1.html
www.epa.gov/oar/aqtrnd99/chapter2.pdf
www.epa.gov/air/urbanair/co/chf.html
www.who.int/environmental_information/Air/Guidelines/Chapter3.htm#3.1
www.epa.gov/children/
www.modcon.co.il/exposure.htm
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