Despite the ban implemented in the 90s, London’s atmosphere still contains lead, according to a study published in PNAS (1). The levels have decreased dramatically and now meet air quality targets, but the researchers found that airborne particles in this city still contain a certain amount of this chemical.
Lead can be used in a variety of ways, including in petrol. For many years, leaded petrol was, in fact, the primary source of lead emissions into the atmosphere in the UK. After several studies demonstrating how lead can cause reproductive and cardiovascular problems in adults, as well as neurodevelopmental problems in children, the use of this chemical in petrol was finally banned in 1999.
Testing the long-term effects of this ban after 20 years, a team from Imperial College London, UK, measured the levels of lead in airborne particles collected from two locations in London between 2014 and 2018. These samples were then compared with results from the 60s, 70s, 90s and 2010.
Analysis showed that lead levels were extremely high before the ban, reaching values around 300-500 ng/m3. The ban implemented in 1999 was very successful, with measurements dropping down to around 20 ng/m3 in 2000, but researchers continued to measure levels around 8ng/m3 in 2018. These values seem to have remained unchanged over the past decade.
Curiously, the isotope composition of the air particles was similar to the measurements obtained from soil and dust, suggesting that lead is continually resuspended by wind and vehicle movement. The team also estimated that around 40% of all lead found in air particles today comes from leaded petrol used before the ban, highlighting the devastating long-term effects caused by human activity. “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”, said the main author of the study, Dr Eléonore Resongles.
For the team, further research looking at lead levels in the blood is needed to assess the effects on Londoners’ health. “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”, explained Dr Resongles.
If even these low levels prove dangerous for people, further measures to target the sources of lead may be needed in the future. For example, covering contaminated soil with fresh soil was enough to reduce the level of lead in the blood of children living in New Orleans. “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”, concluded Dr Resongles.
(1) Resongles E, Dietze V, Green D, Harrison R, Ochoa-Gonzalez R, Tremper A, and Weiss D (2021) Strong evidence for the continued contribution of lead deposited during the 20th century to the atmospheric environment in London of today. PNAS, 118 (26) e2102791118 https://doi.org/10.1073/pnas.2102791118