3.4 - Air Pollution

Incomplete combustion - Carbon monoxide and particulates

When a fuel burns without enough oxygen, incomplete combustion releases carbon monoxide and particulates.

Carbon monoxide

• A toxic gas produced by incomplete combustion.
• It's colourless and odourless, so it isn't easily detected.
• Once breathed in, it reduces the blood's ability to carry oxygen around the body.
• This can cause tiredness, breathing difficulties and, in severe cases, death.

Particulates

• Fine particles of carbon (soot) and unburnt fuel.
• Breathing them in can damage the lungs - worsening respiratory problems and increasing the risk of cancer - and reduces air quality generally.
• In the atmosphere, particulates reflect sunlight back into space, reducing the light reaching Earth's surface (global dimming).

Acid rain

• Sulfur impurities in a fuel burn to release sulfur dioxide into the atmosphere.
• Breathing sulfur dioxide in can cause respiratory problems, and it's the main cause of acid rain.
• Sulfur dioxide dissolves in water droplets in clouds, forming a dilute acid that falls as acid rain.

Effects of acid rain

• Acidifies lakes and rivers, killing fish and other aquatic life.
• Damages trees and other plants.
• Damages buildings and statues made from limestone.
• Corrodes metal.

Reducing air pollution

• Catalytic converter - Fitted to a vehicle's exhaust system, it changes harmful gases produced by the engine into less harmful ones before they leave the exhaust.
• Low-sulfur fuel - Using fuel with a lower sulfur content reduces the sulfur dioxide produced when it's burned.
• Flue-gas desulfurisation (sulfur scrubbing) - At a power station, sulfur dioxide is removed from waste gases before release, often by reacting them with calcium oxide.
• Treating acidified land and water - Soil and lakes affected by acid rain can be treated with a base, such as powdered limestone or lime, to neutralise the acidity.