Question: Why can't we get rid of lead in the atmosphere?

Susan Cartwright answered on 20 Jun 2015:

We can and we (largely) have.

As a heavy metal, lead doesn’t naturally wind up in the atmosphere. Atmospheric lead is usually caused by human activity. The major source of atmospheric lead through most of the 20th century was tetraethyl lead (TEL), which was used as a fuel additive: it improves engine performance, and was first introduced into petrol in the 1920s.

Like most heavy metals, lead is poisonous: specifically, it is a neurotoxin (affects the brain and central nervous system). By the 1970s, the high levels of TEL in urban areas from car exhausts were causing serious concern, and most countries started to phase out leaded fuel from the mid-70s and had more or less completed the process by 2000. I couldn’t find the UK numbers, but in the US levels of lead in the air decreased by 94% between 1980 and 1999 (source: EPA website http://www.epa.gov/airquality/lead/). So, in fact, we can and we have got rid of most of the lead in the atmosphere.

In the US, the dominant remaining source of atmospheric lead is aircraft. Ordinary commercial jets use lead-free fuel, but small propeller-driven planes still use leaded fuel. According to the EPA website, in 2011 60% of the remaining lead emission came from aviation fuel. This really ought to be banned: there are alternative antiknock agents that could be used in aviation fuel.

Once you get rid of aviation fuel, the rest of the lead emission sources are harder to eliminate: the next most dominant source is assorted industrial processes, mostly metal refining. There’s also some from coal-fuelled power stations. But dealing with the small planes would already make a significant difference – on the American figures, it would get us down to less than 3% of the lead concentration in 1980.