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Aviation Gasoline

Environment and Airports

Environmental Information

Is TEL Toxic?

All forms of lead are toxic if inhaled or ingested. Lead can affect human health in several ways, including effects on the nervous system, red blood cells and cardiovascular and immune systems. Infants and young children are especially sensitive to even low levels of lead, which may contribute to behavioral problems, learning difficulties, and lower IQ due to their developing nervous systems.

How are aircraft emissions regulated?

At present, there are no regulations that apply to emissions from piston engine aircraft that use leaded fuel. However, there are two US environmental programs that could potentially limit or prohibit the use of leaded avgas and an EU environmental program that could potentially ban production of the only remaining source of the additive TEL for leaded avgas. The FAA and industry have been communicating with the EPA and the EU on the continued need for 100LL avgas for the safe operation of piston engine aircraft, potential impacts that these regulations may have on piston aircraft operations, and the effort to find unleaded alternatives to 100LL under the PAFI program and other venues. The following is a summary of these environmental programs:

1. Regulation of Lead Emissions Under the Clean Air Act:

Under section 231 of the CAA, the EPA determines if pollutant emissions from aircraft engines cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare. The EPA has commonly referred to these determinations as "endangerment and cause or contribute findings." The EPA has recently conducted studies to evaluate the impacts on air quality from lead emissions from piston engine aircraft. The EPA endangerment and cause or contribute findings are a long term action.

If the EPA makes a positive endangerment and cause or contribute findings regarding piston engine aircraft lead emissions, the EPA would then, in consultation with the FAA, develop proposed standards addressing lead emissions from piston-engine aircraft which would be finalized after a notice and comment period. The CAA specifies that in setting aircraft engine emission standards, the EPA must consider the time needed to develop and apply required technology and cost of compliance. Moreover, aircraft emission standards must not adversely affect aircraft safety or significantly increase noise. The Secretary of Transportation is directed by the Clean Air Act, in consultation with the EPA, to prescribe regulations to insure compliance with the EPA's emissions standards. Finally, if the EPA issues positive endangerment and cause or contribute findings regarding aircraft lead emissions, the FAA would also be authorized to specify fuel compositions that could reduce or eliminate lead emissions.

The EPA provides additional information about its lead endangerment studies and the Federal Action Plan to Reduce Childhood Lead Exposure related to TEL on its Regulations for Lead Emissions from Aircraft page.

2. Regulation of Ethylene Dibromide Under the Toxic Substances Control Act (TSCA)

Ethylene dibromide (EDB) is added in combination with TEL to 100LL avgas to prevent the buildup of lead deposits within piston aircraft engines. Under the Toxic Substances Control Act (TSCA), EPA designated EDB as a "high-priority substance" for risk evaluation in December 2019 and is currently evaluating the potential risks of EDB on human health and the environment. If the use of EDB as an additive for 100LL avgas presents unreasonable risks, then EPA has the authority to impose restrictions on the production and use of EDB. EPA is generally required to publish final risk evaluations no later than three to three and a half years after identifying a chemical as a high priority for risk evaluation. Any regulatory action to reduce unreasonable risks would come thereafter.

The EPA has released a draft scope of the risk evaluation for EDB and other information about TSCA (PDF).

3. Regulation of the Production of TEL Under European Union's (EU) Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH)

Regulations under the EU REACH program have the potential to prohibit the production of TEL in the EU. The European Commission (EC) has received recommendation from its European Chemicals Agency (ECHA) to include TEL as an "Annex XIV" substance and the EC has anticipated that it may be able to resume assessment of TEL for Annex XIV listing later in the summer or fall. If TEL is included as an Annex XIV substance after the assessment, it would be subject to a sunset date that would ban TEL production in about three years thereafter unless an authorization is granted for its production and use in avgas. A ban on the production of TEL by the EU would eliminate the only remaining source of aviation grade TEL from Innospec, Inc., which is located in the United Kingdom (UK). Banning the production of TEL from Innospec, Inc. could potentially end the worldwide production of 100LL specification avgas.

It is not yet known how the UK will address EU REACH regulations with the UK's withdrawal from the EU in January 2020 and the end of the Brexit transit period in December 2020.

The EU's REACH regulations are further explained by the European Chemicals Agency – Understanding REACH.

Airport Mitigation

What is FAA doing in the short term to reduce lead emissions?

The long-term goal for 100LL avgas is to identify and approve existing aircraft to operate safely with an unleaded replacement to 100LL. In the short term, there are some operational measures that can be implemented at airports to reduce or minimize potential exposure to aircraft lead emissions. It should be noted that some of these initiatives are airport specific, and that airport operators themselves should be taking these initiatives, rather than FAA, which may not have the authority to implement these initiatives at airports.

Increasing the distance between run-up areas and public areas may reduce potential exposures to aircraft lead emissions. Therefore, the FAA encourages airports with significant general aviation activity (especially piston-powered aircraft) to work with their designated Airports District Office (ADO) on the size, location and orientation of run-up and maintenance areas.

  • If existing run-up areas typically cause propeller wash to be directed off-airport property or into areas where the public can be exposed, the airport operator should consider shifting either the location or orientation of run-up activities to locations where the emissions can be better contained to non-public areas on the airport.
  • In cases where it is not immediately feasible to reduce lead emissions, consider minimizing the public's outdoor air exposure to lead emissions by either shifting fences (to increase the distance between run-up areas and public observation areas) and/or posting signs to discourage loitering by the public in those areas where there may be potential and unnecessary exposure to lead from piston engine aircraft emissions.

Airport operators are encouraged to evaluate these suggested measures while taking into account the specific operational and safety needs unique to their airport. Any change in operation that relocates a lead emission source must also be evaluated so as not to exacerbate exposure to lead emissions.

There are already unleaded fuel alternatives available for use by a significant segment of the existing aircraft fleet. At the FAA's Supplemental Type Certificate database, search for "UL94", "UL91", or "ASTM 4814" for a listing of available supplemental type certificates (STCs). The FAA encourages airport operators and fuel suppliers to look into the business case to provide these unleaded fuels as an alternative to 100LL avgas.

What other studies are being conducted related to leaded avgas?

Under Section 177 of the 2018 FAA Reauthorization Act (Public Law 115-254), the FAA has entered into an agreement with the National Academies of Sciences, Engineering and Medicine under which the National Research Council (NRC) will study aviation gasoline. This study shall include an assessment of:

  • Existing, non-leaded fuel alternatives to the aviation gasoline used by piston-powered general aviation aircraft;
  • Ambient lead concentrations at and around airports where piston-powered general aviation aircraft are used; and
  • Mitigation measures to reduce ambient lead concentrations, including increasing the size of run-up areas, relocating run-up areas, imposing restrictions on aircraft using aviation gasoline, and increasing the use of motor gasoline in piston-powered general aviation aircraft.

It is expected that this study will be completed and issued to Congress by December 31, 2020.

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