There’s still lead in London’s air, 20 years after fuel ban

Despite a huge drop in levels of lead in London’s atmosphere following the ban on leaded fuel in 1999, levels of the toxic metal are still higher than natural background levels.

That’s according to new research from Imperial College London published yesterday in the journal PNAS. The study found that up to 40 per cent of lead in airborne particles today comes from the legacy of leaded petrol – highlighting the long-term persistence of contaminants introduced to the environment. 

“Petrol-derived lead deposited decades ago remains an important pollutant in London. Despite the leaded petrol ban, historically combusted lead is still present in London's air more than 20 years later,” says Dr Eléonore Resongles, who carried out the work at Imperial's Department of Earth Science and Engineering. 

Researchers compared the chemical and isotopic composition of particulate matter in the air with samples of road dust and urban soil, and confirmed that it was the resuspension of dust contaminated by leaded petrol which was causing the problem. Lead settled in the environment decades ago, and is sent back into the air by wind and vehicle movement, creating a constant background level.

"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,” Resongles added.

Historically lead was used in everything from batteries to paint, but until 1999 it was fuel which accounted for most of the lead emissions in the UK atmosphere. That year, following evidence that exposure to lead causes developmental problems in children and a wide range of health problems in adults, leaded fuel was banned.

The study measured lead and its composition at two London locations between 2014 and 2018, and compared it to previous data from the 1960s onwards. In the 1980s, annual average airborne lead concentrations in central London dropped from 500-600 ng/m3 of air to around 300 ng/m3, before dropping further to around 20 ng/m3 in 2000. The researchers in this study measured lead concentrations of 8 ng/m3 of air on average during the summer 2018 at Marylebone Road.

"We used to have a lot of lead circulating in the air, but it dropped dramatically when leaded petrol was phased out at the turn of the millennium,” said senior author Professor Dominik Weiss. “However, the evolution of isotope composition since then suggests that lead in the air, soil and dust persists at background levels, and this could turn out to be a concern for health. Our findings highlight the need for an in depth study of blood lead levels in the population as was done recently in the US. Legacy lead deposited pre-1999 is significantly contributing to the overall lead burden, so we must try to reduce further the amount of lead we are releasing today if we want to offset legacy metals.”

The findings are in line with previous research in Brazil, Weiss says, and raise questions about long-term lead contamination. Potential solutions include covering contaminated urban soil with fresh soil – an approach which has worked well in New Orleans.  "Atmospheric lead has reached a baseline in London which is difficult to push down further with present policy measures,” Resongles says. “More research is needed to identify the effect of present air concentrations – even if they meet data air quality targets – on human health, and to find the best way to rid London of lead's legacy for good."

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