Rajan Wilcox
Tetraethyl lead, also known as TEL, is a highly toxic compound that was widely used as a fuel additive for much of the 20th century. TEL was added to gasoline to reduce engine noise and increase vehicle performance and fuel economy. However, due to its toxicity and the health hazards it posed, there was a global effort to phase out TEL from automotive fuel, which was achieved in July 2021. While leaded gasoline for cars and trucks has been phased out, leaded fuels are still used in aviation, motor sports, and other off-road purposes. This has shifted the focus towards addressing the environmental and health concerns associated with diesel fuel, which is now more widely used.
| Characteristics | Values |
|---|---|
| Common name | TEL (tetraethyl lead) |
| Formula | Pb(C2H5)4 |
| Use | Fuel additive |
| Toxicity | Highly toxic, causes lead poisoning |
| Ban status | Banned in cars since 2021 |
| Ban enforcement | EPA, UNEP |
| Aviation use | Still used in aviation fuel |
| Diesel specifications | Allow 20 parts per million lead |
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What You'll Learn
TEL is a highly toxic central nervous system toxin
TEL, or tetraethyllead, is a highly toxic central nervous system toxin. It was widely used as a fuel additive for much of the 20th century, first being mixed with gasoline in the 1920s. TEL was added to gasoline to reduce engine knocking and raise the fuel's combustibility or octane levels.
TEL is a colourless liquid with a sweet odour. Its toxicity arises from its ability to easily cross the blood-brain barrier and accumulate in the limbic forebrain, frontal cortex, and hippocampus. This results in acute toxic psychosis, with symptoms such as hallucinations, delirium, and convulsions. There is no cure for direct poisoning by TEL.
The dangers of TEL were recognised early on, with concerns being raised as early as 1924 when 15 refinery workers died of suspected lead poisoning. However, it was not until the 1960s and 1970s that evidence of health issues related to lead poisoning was acknowledged nationally. By the 1970s, the United States and many other countries began phasing out the use of TEL in automotive fuel.
The phase-out of TEL was completed in the United States on January 1st, 1996, with most countries banning TEL in gasoline by the early 2000s. In July 2021, the sale of leaded gasoline for cars was completely phased out worldwide, marking the end of TEL use in vehicles.
The hazardous effects of TEL exposure include acute symptoms such as irritation of the eyes and skin, sneezing, fever, vomiting, and a metallic taste in the mouth. Chronic exposure can lead to long-term issues like memory loss, neurological problems, insomnia, and a decrease in IQ and cognitive function. TEL has also been linked to behavioural issues and learning disorders in children, who are more sensitive to the toxic effects of lead.
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Leaded gasoline has been phased out worldwide
Leaded gasoline, or tetraethyl lead (TEL), was invented in the 1920s by General Motors engineer Thomas Midgley Jr. TEL was added to gasoline to reduce engine knock and raise the fuel's combustibility or octane levels. This resulted in improved vehicle performance and fuel economy. However, TEL was soon found to be highly toxic, causing lead poisoning and neurotoxicity, especially in children. Despite this knowledge, it took several decades for scientists to establish the full extent of the damage caused by leaded gasoline, and for it to be phased out worldwide.
In the United States, the phase-out of leaded gasoline began in the 1970s, with the Environmental Protection Agency's (EPA) efforts to reduce its use. By the 1980s, most gasoline used in the U.S. was unleaded, and by 1996, leaded gasoline was completely banned in the country. The European Union also banned leaded gasoline in 2000, and by the early 2000s, most countries had followed suit. However, leaded gasoline continued to be used in many developing countries at the turn of the millennium.
The United Nations Environment Program (UNEP) played a crucial role in the global phase-out of leaded gasoline. In 2002, they launched the Partnership for Clean Fuels and Vehicles (PCFV) to work with governments and industries to eliminate leaded fuel. This initiative faced challenges due to the higher cost of unleaded fuels and the resistance from some countries, particularly those facing wars or corruption issues. Nonetheless, the efforts persisted, and in July 2021, Algeria, the last country to produce and use leaded gasoline, terminated its production and sales. This milestone was officially declared by the UN on August 30, 2021, marking the end of leaded gasoline use in vehicles worldwide.
The successful phase-out of leaded gasoline is a significant achievement for global health and the environment. It is expected to prevent more than 1.2 million premature deaths annually and improve air pollution levels worldwide. Additionally, the reduction in lead exposure has already led to lower violent crime rates and improved overall intelligence in children. With leaded fuel no longer used in vehicles, the focus now shifts towards phasing out fossil fuels and promoting the use of cleaner alternatives.
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Lead in fuel is primarily an anti-knock agent
An anti-knock agent is a gasoline additive used to reduce engine knocking and increase the fuel's octane rating by raising the temperature and pressure at which auto-ignition occurs. Engine knocking, also called "pinging" or "pinking", refers to the tendency of the fuel mixture to ignite early before the correctly timed spark occurs. This premature ignition can damage the engine. TEL, or tetraethyllead, was found to be an effective anti-knock agent, as it could raise the fuel's combustibility or octane levels, reducing engine noise.
However, TEL was also highly toxic. As early as 1924, concerns were raised about the potential health impacts of fine particles of lead in the atmosphere. In 1924, 15 refinery workers in Ohio and New Jersey died of suspected lead poisoning. Despite this, it was not until the 1960s and 1970s that mounting evidence of health issues related to lead poisoning was acknowledged at a national level.
Due to the toxicity of TEL, many countries began phasing out its use in automotive fuel in the 1970s. The United States achieved the total elimination of sales of leaded gasoline for on-road vehicles on January 1, 1996. By July 2021, the sale of leaded gasoline for cars was completely phased out worldwide. Today, ethanol has replaced TEL as a safer gasoline additive to achieve the same purpose.
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Aviation fuel still contains lead
Tetraethyllead (TEL), a colourless liquid with a sweet odour, was widely used as a fuel additive for much of the 20th century. TEL was added to gasoline to raise its combustibility or octane levels, thereby reducing engine knocking. However, TEL was also extremely toxic, causing lead poisoning and neurotoxicity in humans, especially children.
Despite the dangers of TEL, it was used in automotive fuel until it was phased out in the 1970s and 1980s, and completely banned in 1996. However, TEL is still present in aviation fuel, also known as avgas. Avgas is used in aircraft with spark-ignited internal combustion engines, particularly those with piston engines. It is a complex mixture of hydrocarbons that vary widely in their physical and chemical properties.
The continued use of leaded fuel in aviation is due to the complexity of finding a safe alternative that meets the specific requirements of aviation engines. While there are ongoing efforts to reduce or eliminate the use of lead in aviation gasoline, it is a challenging process. In 2012, the Federal Aviation Administration (FAA) sponsored an Aviation Rulemaking Committee (ARC) to develop a process and timeline to replace leaded aviation fuels with unleaded solutions. The committee's final report, known as the Unleaded Avgas Transition (UAT) Committee Final Report, made several recommendations to facilitate the development and deployment of unleaded aviation gasoline.
The FAA has also established performance metrics and initiated short-term initiatives to reduce lead emissions. Additionally, some aircraft engines have been converted to run on automotive fuel or jet fuel. However, the alloys used in aviation engine construction are chosen for their synergy with lead, and engine wear can be a problem when using unleaded fuel. As a result, aviation fuel still contains lead, but efforts are ongoing to find a safe and suitable alternative.
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Diesel fuel standards and regulations
In the US, the Environmental Protection Agency (EPA) has played a significant role in regulating diesel fuel. Beginning in 1993, the EPA started regulating sulfur levels in diesel fuel, which previously contained as much as 5,000 parts per million (ppm) of sulfur. In 2006, the EPA began phasing in more stringent regulations to lower the sulfur content in diesel fuel to 15 ppm, known as ultra-low sulfur diesel (ULSD). These regulations targeted emissions from on-road and non-road diesel sources, collectively reducing harmful emissions by more than 90%.
EPA's diesel standards also address nonroad engines and equipment, requiring the use of ULSD for certain applications. As of 2014, EPA's diesel standards mandate that all nonroad, locomotive, and marine (NRLM) diesel fuel and engines must use ULSD, with some exceptions for older locomotive and marine engines. The EPA is also proposing regulatory changes to accommodate the global marine fuel market by allowing the distribution and sale of distillate diesel fuel that complies with the 0.50 percent (5000 ppm) global sulfur standard.
In addition to federal regulations, US states like California have implemented their own fuel standards. California's Low Carbon Fuel Standard (LCFS) places requirements on the renewable content of diesel fuel that differ from federal standards. California also regulates additional fuel properties such as API gravity, lubricity, polycyclic aromatics, nitrogen, and cetane number.
The shift away from leaded gasoline to cleaner diesel and unleaded fuels has been a significant development in the history of fuel standards. Leaded gasoline, which contained tetraethyl lead (TEL), was widely used for much of the 20th century due to its ability to improve engine performance and fuel economy. However, TEL was found to be highly toxic, causing lead poisoning and neurotoxic effects, especially in children. By the 1970s, many countries began phasing out the use of TEL, and in 1996, the US achieved the total elimination of sales of leaded gasoline for on-road vehicles. In July 2021, the sale of leaded gasoline for cars was completely phased out worldwide, marking a significant milestone for global health and the environment.
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Frequently asked questions
Yes, TEL leaded diesel fuel is prohibited.
The United States banned the use of TEL in automotive fuel in 1996. Most other high-income countries followed suit. By 2021, the use of TEL leaded gasoline in cars was phased out worldwide.
TEL was prohibited because it was toxic and caused lead poisoning. It was also linked to behavioral issues and learning disorders in children.
TEL leaded diesel fuel has been replaced with unleaded fuel or diesel fuel.
