Which air pollutant is known to displace oxygen in blood?
Carbon monoxide causes functional oxygen deprivation by competing with oxygen for haemoglobin and forming carboxyhaemoglobin. Its very high binding affinity reduces the number of sites available for oxygen and impairs unloading from the remaining oxyhaemoglobin. The phrase 'displace oxygen' is a physiological shorthand: carbon monoxide does not remove dissolved oxygen directly, but sharply lowers the blood's effective oxygen-carrying and delivery capacity. The distinction is ecologically important because emission control must target either the directly released precursor or the product formed
Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology