Previous Year Question

Carbon Monoxide (CO) is a colourless, odourless, and highly toxic gas produced by the Incomplete Combustion of carbon-containing materials. Its major sources include motor vehicle emissions, industrial fuel combustion, burning coal and wood, and cigarette smoke. After entering the body through inhalation, Carbon Monoxide passes from the lungs into the blood and binds with Haemoglobin in Red Blood Cells. The binding affinity of CO for Haemoglobin is approximately 200–250 times greater than that of Oxygen (O₂).

Haemoglobin normally carries oxygen from the lungs to different tissues of the body. Carbon Monoxide combines with Haemoglobin to form Carboxyhaemoglobin (COHb), reducing the blood's oxygen-carrying capacity. Additionally, the presence of CO interferes with the release of oxygen from the remaining Haemoglobin. Consequently, oxygen deficiency in body tissues (Tissue Hypoxia) may occur. The brain and heart are particularly affected because these organs require a continuous and substantial oxygen supply.

Symptoms of Carbon Monoxide Poisoning include headache, dizziness, weakness, nausea, and confusion. Severe exposure can cause unconsciousness, cardiovascular complications, and even death. The risk depends on the gas concentration and Duration of Exposure. In enclosed spaces, poorly ventilated heaters, generators, and fuel-burning appliances increase the danger of CO accumulation.

Among the other options, Peroxyacetyl Nitrate (PAN) is a component of Photochemical Smog that can cause eye irritation and damage vegetation. Carbon Dioxide (CO₂) is produced through respiration and combustion and is a major Greenhouse Gas. Ozone (O₃) acts as an air pollutant in the Troposphere, affecting the respiratory system, while in the Stratosphere it protects against ultraviolet radiation. Scientifically, the distinguishing property of CO is its much stronger binding affinity for Haemoglobin, not necessarily a faster binding rate than oxygen. The expression 'more rapidly' in the question should therefore be understood in the context of greater binding affinity.