More than 20 years after lead was banned from petrol in 1999, its polluting effects are still being felt in London.
Airborne particles remain highly lead-enriched compared to natural background levels, Imperial College London said in the scientific journal PNAS, published on Tuesday.
Up to 40 per cent of lead in airborne particles derives from previous use of leaded petrol, the study found.
Researchers said the work highlighted the long-term existence of air contaminants introduced by human activity.
The city, which has long had a pollution problem, was one of the first to introduce a congestion charge to reduce the volume of traffic in the centre and last year set up an ultra-low emissions zone for Greater London.
“Petrol-derived lead deposited decades ago remains an important pollutant in London,” said lead author of the study Dr Eleonore Resongles, from ICL’s department of Earth science and engineering.
“Despite the leaded petrol ban, historically combusted lead is still present in London’s air more than 20 years later.”
The study found that although lead levels had dropped dramatically, what remains is “persistent”.
Dr Resongles said further investigation was needed into the health effects on people in London because despite air quality targets there is no safe threshold for lead in humans.
“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,” Dr Resongles said.
Scientists compared the composition of particulate matter in the air with samples of road samples and urban soil, which confirmed the presence of dust contaminated by leaded petrol in London.
They said that once settled in the environment the lead particles were steadily recirculated by wind and vehicle movement.
The researchers took 18 samples of airborne particles at street level in Marylebone in summer 2018 and 20 samples from a 24-metre-high rooftop at ICL’s South Kensington campus between 2014 and 2018.
They found lead sources had remained unchanged over the past decade. 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 the metal’s emissions in the UK.
But the use of lead in petrol has ceased in most countries worldwide due to evidence that exposure can cause neurodevelopmental problems in children and cardiovascular, kidney and reproductive problems in adults.
The study was in collaboration with the French National Research Institute for Sustainable Development, Princeton University in the US, the University of Birmingham, the German Meteorological Service and King Abdulaziz University in Jeddah, Saudi Arabia.
