Lead from petrol persists in London’s air despite it being banned in 1999, research suggests.
Experts found levels in London’s atmosphere have dropped drastically since lead additives in petrol were phased out, and currently meet UK air quality targets.
However, despite this drop, airborne particles in the city are still highly lead-enriched compared to natural background levels.
Up to 40% of lead in airborne particles today comes from the legacy of leaded petrol, the researchers found.
They say this highlights the long-term persistence of contaminants introduced by human activities in the environment.
“Despite the leaded petrol ban, historically combusted lead is still present in London’s air more than 20 years later.”
Scientists compared the composition of particulate matter in the air with samples of road dust and urban soil, which confirmed the role of the resuspension of dust contaminated from leaded petrol in lead’s persistence in London today.
They said lead from leaded petrol once settled in the environment is steadily resuspended into the air through wind and vehicle movement.
This provides a constant background level and remobilisation mechanism.
The findings also highlight the potential hazard that warrants further investigation into its effects on Londoners’ health as, despite air quality targets, there is no “safe” threshold for lead in humans.
Dr Resongles added: “Long-term low-level exposure to lead can adversely affect health and, while we don’t yet know the health implications of our findings, they suggest that leaded petrol might still be providing low level exposure which can have detrimental effects on health.”
Historically lead has been used in a variety of ways, from petrol, batteries, alloys and solders to piping and paint in homes and buildings.
Until 1999, leaded petrol remained the primary source of lead emissions in the UK atmosphere.
But the use of lead in petrol has ceased in most countries worldwide because of evidence that exposure to lead causes neurodevelopmental problems in children and cardiovascular, kidney, and reproductive problems in adults.
The study, included researchers from French National Research Institute for Sustainable Development and Princeton University in collaboration with University of Birmingham, German Meteorological Service, and King Abdulaziz University.
They measured the concentrations of lead and its isotopic composition in two London locations between 2014 and 2018, before comparing them with previous data from the 1960s, 70s, 90s, and 2010.
The researchers took 18 samples of airborne particles at street level in Marylebone in the summer of 2018, and 20 samples on a 24-metre-high rooftop at Imperial’s South Kensington campus between 2014 and 2018.
When comparing the historical data of the isotopic composition of air particles in London, they found lead sources have remained unchanged over the past decade.
They also found the composition of the air particles was similar to the signature of soils and road dust, leading them to suggest that resuspension of lead-containing dust, perhaps with wind and vehicle movement, is now an important source of lead.
In the 1980s, the annual average airborne lead concentrations in central London dropped from 500-600 nanograms per cubic metre of air to around 300 nanograms per cubic metre.
It dropped further to around 20 nanograms per cubic metre in 2000.
In the study, researchers measured lead concentrations of eight nanograms per cubic metre of air on average during the summer 2018 at Marylebone.
They say if these current levels prove harmful, measures should be taken to target the sources of the lead in soil and on roads, including covering contaminated urban soils with fresh soil, which has been effective in reducing children’s blood lead levels in New Orleans.
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.”
The research, published in PNAS, was funded by the European Union’s Horizon 2020 grant, Imperial College London, and the European Commission.