Don’t look up! There’s poison in our skies
Don’t look up! There’s poison in our skies
Long banned in road fuels due to its toxicity, lead is still a component of aviation gasoline (avgas). Used by most piston-engined aircraft – from flying-school trainers to crop-sprayers – leaded avgas is a major source of airborne lead exposure. A global phase-out is possible, but the transition is challenging, as JULIA TEW reports.
Odourless, colourless and tasteless, lead is an extremely potent neurotoxin with no safe level of exposure. According to warnings from the World Health Organization, it accumulates in the body, causing damage to the heart, kidneys, reproductive and immune systems and brain.
Children are the most vulnerable. Even low-level exposure is linked to reduced IQ, learning difficulties, behavioural problems, delinquency and later-life aggression and violence. Lead deposited by aircraft can also contaminate soil and water, and crop-spraying aircraft may disperse it directly over farmland and livestock. Despite these risks, leaded avgas remains the standard fuel for light and ultralight piston aircraft in most countries, including South Africa.
Lead is added to avgas to raise its octane rating and prevent engine knocking – essential for high-performance piston engines – and to protect valve seats. The most common grade, Avgas 100LL (100-octane low-lead avgas), still contains up to 0.56g of tetraethyl lead (TEL) per litre. Evaporative emissions during fuel production, handling, refuelling and low-altitude flight are the largest contributors to airborne lead exposure for pilots, airport workers and nearby communities.
The US: leading on lead-free
The United States, with the world’s largest general aviation (GA) fleet of 170,000 piston aircraft, is leading the shift. Researchinitiatives began over 20 years ago under the leadership of the Coordinating Research Council, before the Piston Aviation Fuels Initiative (PAFI) committee was set up in 2011 to develop a detailed roadmap for further testing and implementation of unleaded avgas.
What finally triggered momentum for a national phase-out, however, was an “endangerment finding” issued in 2023 by the Environmental Protection Agency (EPA). It confirmed that lead emissions from piston-engined aircraft pose significant public-health risks, especially for children living near small GA airports. The Eliminate Aviation Gasoline Lead Emissions (EAGLE) initiative was introduced, aimed at transitioning all piston aircraft to unleaded fuel by 2030. Several fuel candidates are now in advanced testing and certification with the Federal Aviation Administration (FAA).
The transition is anything but straightforward, though. Industry groups within the General Aviation Avgas Coalition warn that roughly a third of the US fleet requires high-octane 100LL, and misfuelling could cause catastrophic engine failure, among other consequences. No unleaded fuel yet meets all performance, safety and material-compatibility needs of the entire fleet, though GAMI’s G100UL, Swift Fuel’s 100R and LyondellBasell/VP Racing’s UL100E have made significant progress. Air BP is also marketing a mid-octane unleaded avgas grade, UL91, which is not suitable for all aircraft, but does offer the same high-energy content as traditional 100LL (43.5 MJ/kg minimum).
The transition has seen many charter operators and flying clubs postpone or reduce avgas purchases, due to concerns about future aircraft compatibility or unleaded fuel availability. Additionally, alternative propulsion technologies like turbo-diesel piston or electric engines are capturing some training-fleet share, reducing avgas demand.
Europe: one step forward…
Europe faces similar dilemmas. Although TEL is now classed as a severe reproductive toxin, regulatory delays have allowed continued production of leaded avgas. In 2024, Shell secured approval to keep importing and producing Avgas 100LL until 2032, with the two other EU manufacturers, Warter Fuels and Trafigura (Puma Energy), expected to follow. As in the US, industry groups argue that a premature ban would ground aircraft and disrupt regional economies.
The adoption of unleaded alternatives like G100UL and Puma’s UL94 has been hindered by bureaucratic bottlenecks. Acquiring certification from the European Union Aviation Safety Agency (EASA) for each engine and airframe combination is a slow and resource-intensive process.
Nevertheless, Swedish producer Hjelmco Oil has received EASA approval for its unleaded avgas 91/96 UL, which is certified for use in over 90% of the world’s piston-powered GA fleet, the company reports.
Towards a global transition
While the US and Europe move tentatively towards transition, the rest of the world appears to be weighing up their options or simply continuing with business as usual.
In the United Kingdom, where the vast majority of avgas used in the country’s 107 aerodromes is leaded, Keir Starmer’s government has been urged to phase out TEL production and use. There are over 370,500 residences within 4km of a GA airport at risk from exposure to lead emissions, according to a 2022 study by the University of Kent. The Department of Transport said it was working closely with the industry and the UK Health and Safety Executive to move towards lead-free alternatives as quickly as possible.
In South Africa, local aviation fuel suppliers continue to supply Avgas 100LL to flying schools, charter operators, private pilots, wildlife reserves and agricultural aviation fleets. Other applications include express freight, aerial firefighting and surveillance, search and rescue, medical evacuation and aeromedical transport. It is also used in some helicopters and military aircraft. South Africa has not yet published large-scale epidemiological research similar to US studies, but environmental monitoring around certain airports has raised concerns about cumulative heavy-metal deposition.
Although the local aviation industry is increasingly engaged in sustainability conversations – especially around sustainable aviation fuel (SAF) for turbine engines – these initiatives do not address the lead issue, because SAF is a jet-fuel substitute, not an avgas replacement. That being said, South Africa is a member of the International Civil Aviation Organization (ICAO) and is expected to align with its global standards and recommended practices.
Similar trends are visible in many African and South Asian markets, where training fleets and crop-sprayers operate with little policy attention on unleaded transition. Brazil continues to manufacture leaded avgas despite strong SAF progress. This situation raises the risk of a two-tier transition, where wealthy countries eliminate leaded avgas while lower-income regions become long-term repositories for older engines and lead-based fuels.
Cases of this nature already exist, such as the 2014 conviction of two executives at UK-based Innospec – the only operation in the world still manufacturing TEL (outside of China). The men conspired to bribe Indonesian officials between 2002 and 2008 to smooth TEL sales in the country – one of few still allowing the use of leaded petrol.
What lies ahead
For South Africa and the broader region, opportunities exist among the challenges. Coordinated engagement between aviation authorities, fuel suppliers, flying schools, agricultural operators and public-health experts could accelerate adoption of lead-free alternatives, ensuring the country doesn’t lag behind the global shift. Refineries will need to retool, airports will need to adapt storage systems and operators must be assured that unleaded alternatives will not damage engines or void warranties.
Leaded avgas is aviation’s last major legacy toxin – persistent, harmful and largely avoidable. As the world’s attention turns to decarbonisation, the GA sector cannot afford to continue ignoring this pernicious pollutant. The science is unequivocal and alternatives are emerging. Now the question is whether South Africa – and the rest of the Global South – will begin to act, or wait while others take the lead.
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