Which one of the following air pollutants combines with the haemoglobin of human blood and reduces its oxygen- carrying capacity, leading to suffocation and may cause even death?

Carbon monoxide (CO) is a highly toxic air pollutant that poses a severe threat to human health. In the human body, the respiratory pigment haemoglobin typically has a high affinity for oxygen [1]. However, carbon monoxide possesses an affinity for haemoglobin that is approximately 200 to 250 times greater than that of oxygen. When inhaled, CO binds preferentially with haemoglobin to form carboxyhaemoglobin. This stable complex prevents haemoglobin from binding with and transporting oxygen to vital tissues and organs. This reduction in oxygen-carrying capacity leads to hypoxia, causing symptoms such as headache and dizziness. In high concentrations, it results in suffocation (asphyxiation) and can lead to death. While other pollutants like chlorofluorocarbons primarily contribute to ozone depletion [3] and greenhouse effects [4], and sulphur dioxide acts as a respiratory irritant, only carbon monoxide directly interferes with blood oxygen transport in this specific manner.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Do You Know? > p. 90
2. [2] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 19: Ozone Depletion > Other substances: > p. 269
3. [3] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 19: Ozone Depletion > The chemical reaction > p. 268
4. [4] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 11: World Climate and Climate Change > Greenhouse Gases(GHGs) > p. 96