Why is carbon monoxide classified as a pollutant?

Carbon monoxide is classified as a pollutant primarily because it reacts with hemoglobin, the molecule in red blood cells responsible for transporting oxygen throughout the body. This reaction forms carboxyhemoglobin, which reduces the blood's ability to carry oxygen to vital organs and tissues. As a result, exposure to carbon monoxide can lead to serious health effects, including impaired oxygen delivery, neurological damage, and in severe cases, death. This toxicity is particularly dangerous in enclosed spaces where carbon monoxide can accumulate, posing significant health risks to humans and animals alike.

While the other factors mentioned play a role in understanding environmental issues, they do not directly address the immediate harmful effects of carbon monoxide on human health, which is a key reason this gas is classified as a pollutant.