End of an era: why was leaded petrol so harmful?

With Algeria ending the use of the harmful fuel, we take a look at why it was used in the first place

Lead has been banned from petrol in Britain since 1999 but it is still being found in the air in London. Getty

Algeria became the last country to use leaded petrol, a highly toxic crude product that seems to be no longer relevant in a world transitioning towards carbon neutrality.

The UN has hailed the end of a toxic era, which it called a "catastrophe for the environment and public health". We take a look at what leaded petrol is and why it was so harmful.

What is leaded petrol?

It is petrol that contains tetraethyl lead, an additive present in most of the fuel sold throughout much of the 20th century.

Why was it used?

Tetraethyl lead was added to petrol as an anti-knocking agent – a product used to prevent petrol in high-compression internal combustion engines from igniting early before the correctly timed spark occurs.

Why was it phased out?

Tetraethyl lead was flagged by scientists early on for its toxic properties. In 1922, German scientist Charles Klaus called it a "creeping and malicious poison" and said it had killed one of his fellow scientists. After several assessments of its toxicity and harmful effects on people, the compound began to be phased out in 1974 by the US Environmental Protection Agency.

So, what is used in its place to prevent knocking?

Vehicles now use different types of anti-knocking agents to prevent sudden detonation during engine combustion. Oxygenates such as ethanol are very popular and are blended with petrol to reduce knocking. Other compounds such as aromatics are also used but continue to pose a threat to human life due to the presence of carcinogens.

How can we eliminate poisonous emissions?

Several countries around the world are phasing out conventional combustion engines and encouraging the use of engines that run on electricity to curb harmful emissions. With subsidies and state policies guiding industries towards a carbon-neutral world, the internal combustion engine as we know is set to change for good.