Explain why incomplete combustion of hydrocarbon fuels is harmful to human health and the environment.

Incomplete combustion of hydrocarbon fuels produces carbon monoxide (CO). CO is a colourless, odourless gas that binds to haemoglobin in the blood, forming carboxyhaemoglobin and reducing the blood’s oxygen‑carrying capacity. This causes hypoxia, leading to headaches, dizziness, nausea and, in severe cases, death.

Incomplete combustion also releases carbon particulates (soot). These fine particles can penetrate deep into the lungs, causing respiratory irritation, bronchitis and exacerbating asthma. On a larger scale, soot particles absorb solar radiation, contributing to global dimming and climate change.

Thus, incomplete combustion is harmful because it generates toxic CO and particulate matter that pose serious health risks to humans and damage the environment.