Excessive release of the pollutant carbon monoxide (CO) into the air may produce a condition in which oxygen supply in the human body decreases. What causes this condition?

Excess carbon monoxide (CO) reduces oxygen supply because CO binds to hemoglobin (Hb) to form carboxyhemoglobin (COHb), preventing oxygen from occupying those binding sites and effectively reducing the blood’s oxygen-carrying capacity [1]. CO’s affinity for hemoglobin is far greater than oxygen’s—on the order of hundreds of times higher—so even low CO exposures produce significant COHb levels [2]. In addition, COHb formation increases the remaining hemoglobin’s affinity for oxygen (a leftward shift of the oxyhemoglobin dissociation curve), impairing oxygen release to tissues and causing cellular hypoxia. Thus the dominant mechanism is competitive high-affinity binding of CO to hemoglobin, not conversion to CO2, structural destruction of Hb, or primary depression of the respiratory center [1].

Sources

1. [1] https://en.wikipedia.org/wiki/Carboxyhemoglobin
2. [2] https://www.ncbi.nlm.nih.gov/books/NBK430740/