A102 in evening rush hour
The Blackwall Tunnel approach – seen with a jam heading towards Kent – has been a pollution hotspot for decades

Lead from petrol remains in London’s air 23 years after it was banned, researchers from Imperial College have found.

Tetraethyl lead was added to petrol to improve cars’ performance, but it was phased out in the 1980s and 1990s after studies found that it could cause brain damage in children – with those living near motorways more vulnerable – as well as heart, kidney and reproductive problems for adults.

Levels of lead in London’s air have dropped dramatically since it was banned in 1999, but academics found that 40 per cent of lead in airborne particles today comes from the legacy of leaded petrol.

Lead from leaded petrol which has settled in the environment circulates in the air through wind and vehicle movement, providing a constant background level of the pollutant. There is no safe level of lead in air, despite air quality targets.

The findings from the research team – who studied the air on Marylebone Road in central London as well as at Imperial’s campus in South Kensington – will cause concern for those who live near historically congested areas such as the Blackwall Tunnel approaches, the A2 – including its former route along Rochester Way in Eltham – and the South Circular Road.

Dr Eléonore Resongles, who led the team carrying out the study, said: “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.”

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 about 20 ng/m3 in 2000. The researchers in this study measured lead concentrations of 8 ng/m3 of air on average during the summer of 2018 at Marylebone Road.

Senior author Professor Dominik Weiss said: “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. 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.”

The researchers said that if the levels of lead prove to be harmful, then measures should be taken such as covering contaminated soil with fresh soil, which has been effective in reducing children’s blood lead levels in New Orleans.

Dr Resongles said: “Atmospheric lead has reached a baseline in London which is difficult to push down further with present policy measures. 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.”

The research is published in the PNAS academic journal.

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