Which air pollutant binds with hemoglobin to form carboxyhemoglobin?
Carbon monoxide binds the haem iron of haemoglobin with roughly 200 to 250 times the affinity of oxygen, producing carboxyhaemoglobin. This both occupies oxygen-binding sites and shifts the remaining haemoglobin toward tighter oxygen retention, reducing oxygen delivery to tissues. Carbon dioxide is transported mainly as bicarbonate and carbamino compounds and does not create carboxyhaemoglobin. At organismal level, respiratory surfaces are especially exposed because large volumes of air contact thin, moist epithelia designed for rapid gas exchange. Sound classification links the source, atmospheric fate, exposure route, and mechanism of toxicity rather than relying only on the pollutant's name. Effective management combines cleaner fuels, emission standards, monitoring, urban planning, and protection of populations with high exposure or physiological vulnerability. The distinction is ecologically important because emission control must target either the directly released precursor or the product formed after atmospheric transport and reaction. Exposure depends on concentration, duration, ventilation, weather, and individual susceptibility, so a pollutant's presence alone does not fully predict biological harm.
Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology