Toxic lead from petrol that was banned 20 years ago still lingers in the air in London, a study has shown, with researchers saying the legacy of leaded fuels is likely to hang over most cities.
While levels are much lower than at their peak in the 1980s, they remain far above natural background levels. Lead is extremely poisonous and there is no safe amount of exposure. It is of particular concern for children, as it damages their developing brains and ability to learn.
Lead was added to fuels in the UK from the 1930s and phased out in the decade up to 1999. The metal was deposited on urban surfaces and soils over many decades and is thought to be repeatedly thrown back up into the air by winds, traffic and building works, and levels are no longer declining.
The researchers said the work illustrated how pollutants could remain in the environment for many years after being outlawed. Other problems include persistent organic pollutants such as the long-banned pesticide DDT.
“The key message from [our study] is that lead from gasoline is here to stay, and it is making an impact today,” said Prof Dominik Weiss, of Imperial College London. “For over 30 years, the same pollutant has been recycled.”
Lead from long-banned fuels has also been identified in Shanghai, China, and São Paolo, Brazil, and Weiss said it was likely to be contaminating many cities. One in three children around the world have blood levels of lead likely to cause significant long-term health damage, according to a Unicef study.
The new study, published in the journal Proceedings of the National Academy of Sciences, found that 32-43% of the lead in the London air was originally from leaded fuels. Lead atoms can have different numbers of neutrons and the ratio of these isotopes is very distinctive in leaded fuels.
This allows the source of the metal to be distinguished from other sources, such as coal burning, industry, brake and tyre dust, and old paint. The researchers found similar lead levels in both roadside and rooftop samples between 2014 and 2018, indicating the pollution remained in the air across the city.
Levels of lead in the air are now just 2% of the peak in the 80s, but this is still 100 times higher than natural levels, says Weiss. Research in the US has shown that people’s blood lead levels are linked to atmospheric levels of the pollutant, suggesting they ingest lead from the air.
Land contaminated with lead can be made safer by placing clean soil on top, which also prevents children from ingesting lead when they play. This approach has reduced children’s blood lead levels in New Orleans, US.
“Soil remediation can be a great solution, focusing on places where children get exposed such as playgrounds and gardens,” said Eléonore Resongles, of the University of Montpellier, France, and part of the research team. “With a map of the contamination, you can identify the hotspots.”
Prof David Phillips, at the University of Southampton, who was not involved in the study, said: “The key message is that pollutants such as lead don’t go away when they have ceased to be in the spotlight. Lead is still a problem in many old industrial sites and associated with historical mining, as well as from home sources such as lead pipes and old paint.
“The main worry is exposure of young children – there is good evidence for adverse neurodevelopmental effects at low doses. The extent of the problem is difficult to assess but is clearly likely to affect families living near roads with historical heavy traffic volumes.”
A government spokesperson said: “At a national level, air pollution levels have reduced significantly since 2010 but we know there is more to do to tackle harmful emissions given their legacy impact.
“That is why we are setting new legally binding targets on particulate matter pollution through our environment bill and building on our clean air strategy to accelerate action to clean up our air.”