“Tetraethyl lead” was used in early model cars to help reduce engine knocking, boost octane ratings, and help with wear and tear on valve seats within the motor. Due to concerns over air pollution and health risks, this type of gas was slowly phased out starting in the late 1970’s and banned altogether in all on-road vehicles in the U.S. in 1995.
For a more detailed explanation of why lead used to be added to gasoline, it’s necessary to understand a little bit more about gasoline and what properties make it a good combustion material in car engines. Gasoline itself is a product of crude oil that is made of carbon atoms joined together into carbon chains. The different length of the chains creates different fuels. For example, methane has one carbon atom, propane has three, and octane has eight carbon atoms chained together. These chains have characteristics that behave differently under various circumstances; characteristics like boiling point and ignition temperature, for instance, can vary greatly between them. As fuel is compressed in a motor’s cylinder, it heats up. Should the fuel reach its ignition temperature during compression, it will auto-ignite at the wrong time. This causes loss of power and damage to the engine. Fuels such as heptane (which has 7 carbon atoms chained together) can ignite under very little compression. Octane, however, tends to handle compression extremely well.
The higher the compression in the cylinders a car’s motor can produce, the greater the power it can get out of each stroke of the piston. This makes it necessary to have fuels that can handle higher compression without auto-igniting. The higher the octane rating, the more compression the fuel can handle. An octane rating of 87 means the fuel is a mixture of 87% octane and 13 percent heptane, or any mixture of fuels or additives that have the same performance of 87/13.
In 1919, Dayton Metal Products Co. merged with General Motors. They formed a research division that set out to solve two problems: the need for high compression engines and the insufficient supply of fuel that would run them. On December 9, 1921 chemists led by Charles F. Kettering and his assistants Thomas Midgley and T.A. Boyd added Tetraethyl lead to the fuel in a laboratory engine. The ever present knock, caused by auto-ignition of fuel being compressed past its ignition temperature, was completely silenced. Most all automobiles at the time were subject to this engine knock so the research team was overjoyed. Over time, other manufacturers found that by adding lead to fuel they could significantly improve the octane rating of the gas. This allowed them to produce much cheaper grades of fuel and still maintain the needed octane ratings that a car’s engine required.
Another benefit that became known over time was that Tetraethyl lead kept valve seats from becoming worn down prematurely. Exhaust valves, in early model cars, that were subject to engine knocking tended to get micro-welds that would get pulled apart on opening. This resulted in rough valve seats and premature failure. Lead helped fuel ignite only when appropriate on the power stroke, thus helping eliminate exhaust valve wear and tear.
The problems with Tetraethyl lead were known even before major oil companies began using it. In 1922, while plans for production of leaded gasoline were just getting underway, Thomas Midgley received a letter from Charles Klaus, a German scientist, stating of lead, “it’s a creeping and malicious poison” and warned that it had killed a fellow scientist. This didn’t seem to faze Midley, who himself came down with lead poisoning during the planning phase. While recovering in Miami, Midgley wrote to an oil industry engineer that public poisoning was “almost impossible, as no one will repeatedly get their hands covered in gasoline containing lead…” Other opposition to lead came from a lab director for the Public Health Service (A part of the US Department of Health and Human Services ) who wrote to the assistant surgeon general stating lead was a “serious menace to public health”.
Despite the warnings, production on leaded gasoline began in 1923. It didn’t take long for workers to begin succumbing to lead poisoning. At DuPont’s manufacturing plant in Deepwater New Jersey workers began to fall like dominoes. One worker died in the fall of 1923. Three died in the summer of 1924 and four more in the winter of 1925. Despite this, public controversy didn’t begin until five workers died and forty-four were hospitalized in Oct. of 1924 at Standard Oils plant in Bayway NJ.
The Public Health Service held a conference in 1925 to address the problem of leaded gasoline. As you would expect, Kettering testified for the use of lead, stating that oil companies could produce alcohol fuels that had the benefits that were provided by lead, however the volumes needed to supply a growing fuel hungry society could not be met. Alice Hamilton of Harvard University countered proponents of leaded gasoline and testified that this type of fuel was dangerous to people and the environment. In the end, the Public Health Service allowed leaded gasoline to remain on the market.
In 1974, after environmental hazards began to become overwhelmingly apparent, the EPA (Environmental Protection Agency) announced a scheduled phase out of lead content in gasoline. One way manufacturers met these and other emission standards was to use catalytic converters. Catalytic converters use a chemical reaction to change pollutants, like carbon monoxide and other harmful hydrocarbons, to carbon dioxide, nitrogen and water. Tetraethyl lead would tend to clog up these converters making them inoperable. Thus, unleaded gasoline became the fuel of choice for any car with a catalytic converter.
The requirements by the EPA, emission control mechanisms on cars, and the advent of other octane boosting alternatives spelled the end for widespread leaded gasoline use. Manufacturers soon found that cars could no longer handle such a fuel; public tolerance of the environmental and health hazards would not allow it; and it became cost prohibitive to continue producing it. On January 1, 1996, the Clean Air Act completely banned the use of leaded fuel for any on road vehicle. Should you be found to possess leaded gasoline in your car you can be subject to a $10,000 fine.
This hasn’t completely gotten rid of leaded gasoline. You are still permitted to use it for off road vehicles, aircraft, racing cars, farm equipment, and marine engines, in the United States.
- Since the reduction of leaded gas in the United States, the average level of lead in the blood of Americans has decreased by over 75%.
- In 1985, the EPA estimated that over 5,000 Americans died every year from heart disease caused by lead poisoning.
- In 1988, a report was given to Congress by the Agency for Toxic Substances and Disease Registry on childhood lead poisoning in America. It concluded that every year from 1970-1987, as the EPA’s phase out of lead in gasoline was taking place, 2 million children a year had their blood-lead levels reduced to below toxic levels. The report estimated that, from 1927-1987, a total of 68 million children had a toxic exposure to lead from leaded gasoline.
- Since lead is a naturally occurring heavy metal, unlike carcinogens like pesticides, waste oils and radioactive materials, it will not break down over time. It does not vaporize or disappear.
- Just because you seem healthy does not mean you do not have high levels of lead in your blood. Signs and symptoms usually don’t present themselves until the accumulation of lead has reached dangerous amounts. These signs and symptoms include: High blood pressure, declines in mental functioning, pain, numbness and tingling of the extremities, muscular weakness, headache, abdominal pain, memory loss, mood disorders, reduced sperm count, abnormal sperm, and miscarriage or premature birth in pregnant women.
- Treatment for lead poisoning consists of treatment for symptoms and the use of Dimercaptosuccinic acid, which is an organosulfur compound, or Dimercaprol, also known as British anti-Lewisite.
- On October 27, 2011, the United Nations Environment Program announced that the global use of leaded gasoline would be eradicated by 2013. The use of leaded gasoline is still allowed in 6 nations. These nations are Afghanistan, Algeria, Iraq, North Korea, Myanmar and Yemen. The U.N. is assisting those nations in a phase-out of its use.
Expand for References