The US Environmental Protection Agency (EPA) announced its final determination that emissions of lead from aircraft that operate on leaded fuel cause or contribute to air pollution which may reasonably be anticipated to endanger public health and welfare under the Clean Air Act.

This final endangerment finding does not ban or impose restrictions on the use, sale, distribution, dispensing, and general availability of leaded fuel, nor does it establish any new control measures regarding aircraft lead emissions. EPA announced its proposed determination on 7 October 2022, which then underwent public notice and comment. (Earlier post.)

However, with this finding, EPA is now obligated under the Clean Air Act to propose and promulgate regulatory standards for lead emissions from certain aircraft engines. Under its own statutes, the Federal Aviation Administration (FAA) must develop standards that address the composition, chemical, or physical properties of an aircraft fuel or fuel additive to control or eliminate aircraft lead emissions.

Aircraft that operate on leaded aviation gasoline are typically small piston-engine aircraft that carry 2-10 passengers. These aircraft are approximately 45 to 47 years old, on average, depending on the type of aircraft. Jet aircraft used for commercial transport, on the other hand, do not operate on leaded fuel. Levels of airborne lead in the United States have declined 99% since 1980, but emissions from aircraft that operate on leaded fuel may still pose risks to nearby communities, including those with environmental justice concerns.

EPA and FAA have already begun work to consider regulatory options to address lead emissions from aircraft engines and will announce timelines as soon as possible. EPA and FAA will work in partnership and engage all interested stakeholders and the general public as the two agencies develop their separate regulatory actions.

Lead emissions from aircraft are a public health issue. Lead exposure can have harmful effects on cognitive function, including reduced IQ, decreased academic performance, as well as increased risk for additional health concerns. There is no evidence of a threshold below which there are no harmful effects on cognition from lead exposure.

EPA and FAA also understand that piston-engine aircraft play a significant role in transportation in the United States.

Separate from EPA’s endangerment finding, in support of the objective to remove lead from aviation gasoline, in early 2022, the FAA and industry announced the program “Eliminate Aviation Gasoline Lead Emissions” (EAGLE). This program aims to achieve a lead-free aviation system no later than 2030.

The FAA has approved the use of a 100 Octane unleaded fuel—G100UL, developed by General Aviation Modifications, Inc. (GAMI)—that can be widely used by piston-engine fleet, that is not yet commercially available. The FAA has also approved for use a lower octane fuel (UL 94), currently available at approximately 35 airports in the US, and the FAA is working to expand and streamline the process for eligible aircraft to use this fuel.