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Air Pollution
Elements and Compounds

Why is CO poisonous but carbon dioxide is less toxic?


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September 03, 2007 11:14PM

CO displaces oxygen in the blood stream and once it bonds with the blood cells, it is hard to dislodge. A person with an overdose of CO will die sometimes even if they are given pure oxygen because the pure oxygen has nothing to bond to and be carried to the body cells. The blood cells accept CO more readily than oxygen and hang on to it longer.

CO2 is also dangerous, but in a different way. CO2 does not react with the body as does CO, but if the concentration of CO2 is too high, then that means that not enough oxygen is available. This can also kill you -- but the effect is more like holding your breath than breathing a toxic chemical. Too much CO2 isn't bad by itself, it's just that it usually goes along with not enough O2, which is bad. This commonly affects underwater swimmers for instance who build up too much CO2 in their bloodstream as they swim underwater, causing them to pass out under water and drown. You should NEVER hyperventilate before swimming a long distance under water -- my father nearly drowned this way!