EPA Proposes 100LL Endangerment Finding


Weeks after the FAA approved an STC on GAMI’s G100UL unleaded 100-octane avgas for virtually all piston gasoline engines, the EPA has formally proposed a finding of endangerment on 100LL, a pivotal step toward banning the blue fuel. EPA Administrator Michael Regan signed the proposal on Oct. 7 and is submitting it for publication in the Federal Register. The EPA published an initial version of the proposed endangerment finding on its website. The final Federal Register version of the proposal will replace it when it is finally published. Until it hits the Federal Register, comments are not being accepted.

There are no apparent surprises in the proposal, which has undoubtedly existed in draft form for decades as the EPA wrestled with the dilemma of grounding thousands of 100LL-dependent aircraft and the undeniable health hazards created by lead emissions. In the end, the issue was summed up this way. “In this action, the Administrator is proposing to find that lead air pollution may reasonably be anticipated to endanger the public health and welfare within the meaning of section 231(a) of the Clean Air Act,” the opening paragraph of the proposal says. “The Administrator is also proposing to find that engine emissions of lead from certain aircraft cause or contribute to the lead air pollution that may reasonably be anticipated to endanger public health and welfare under section 231(a) of the Clean Air Act.”

Although it will likely take years before the Finding of Endangerment finally results in the end of 100LL, environmental groups are taking a victory lap. Earthjustice, an environmental legal group, represented a host of community groups and political entities that most recently petitioned EPA to get on with it. “We’ve known for decades that lead exposure is responsible for the death of nearly half a million adults annually from cardiovascular disease—and causes irreversible damage to children. EPA must finalize its endangerment finding as soon as possible, and work with the Federal Aviation Administration to quickly phase out leaded avgas,” said Eve Gartner, Earthjustice managing attorney, in a news release. “Banning leaded avgas cannot wait. Every day that goes by without a ban means communities across the country, including hundreds of thousands of children, are breathing lead causing lifelong harm.”

Russ Niles
Russ Niles is Editor-in-Chief of AVweb. He has been a pilot for 30 years and joined AVweb 22 years ago. He and his wife Marni live in southern British Columbia where they also operate a small winery.

Other AVwebflash Articles


  1. “is proposing to find that lead air pollution may reasonably be anticipated to endanger the public health”

    And yet it’s not reasonable.
    Reasonable would involve at least studies on long term pilots, people living in airport communities, and having actual air sampling. Reasonable would also embody a sence of context and without preconceived biases and agendas.

    Eve Gartner with Earthjustice is not reasonable.

    • If only we had decades of knowledge to back up the revolutionary idea that lead exposure is bad for humans! Then it might be reasonable.

      • Reason has been out the window for deacades since most GA airplanes don’t need lead nor 100 octane fuel.

        • According to GAMI, AOPA, EAA, Continental, Lycoming, and the rest of the alphabet soup, ~75% of the GA fleet needs 100 octane fuel.
          The TEL (tetraethyl lead) is the octane booster that gives us 100 octane fuel.

          • They built a lot more 172’s, PA-28’s, 150’s, Cub’s, and planes with O-320’s and O-360s and O-200’s and Rotax and other non-100 octane engines that dwarf the number of of other GA planes.

            100UL is another “take it or leave it” for the bulk of GA that neither needed lead nor 100 octane. Not sure how I can rejoice in paying more while still being summarily ignored.

          • That is a convoluted statement. 75% of the avfuel usage is 100 Octane not 75% of the fleet. They high powered planes fly more and use more fuel.

      • I don’t think anyone is denying that lead shouldn’t be sprinkled on toast with breakfast. However, the reasonable part comes with the risk versus reward equation. GA is the “largest source of lead emissions” because it is the only one left. And, as has been pointed out repeatedly in the 100UL debate, that market is tiny. So, logically, the “largest remaining source of lead emissions” is also probably the smallest statistically-significant source there ever was. So, it is entirely reasonable to question whether the risk associated with those emissions is really so great as to warrant yet another nail in what is increasingly looking like the regulatory coffin of general aviation. Or, is this another case of special-interest-manufactured paranoia driving unwarranted concern in the public? (I hereby refer you to the cases of numerous sweeteners and food additives that are banned in the US but not elsewhere and vice versa as examples.)

        Point being, I (and many others I’m sure) are all for unleaded fuel. But, if the risk is as low as I suspect it actually is, I’d rather we get the right solution, not the chosen-by-committee, engineered-by-elected-lawyers, right-now solution.

      • Wrong again! We don’t have decades of knowledge.

        Since even the Romans knew lead water pipes were bad for their health, we actually have MILLENIA of knowledge! (they often made them out of lead anyway cuz they were cheaper, showing again that nothing changes)

        • Jeffrey, quick question risk factors:
          Would you rather have lived the last 50 years on a small GA airport using 100LL or the last 10 years in Flint Michigan?

          They didn’t. Just like now. Everything is profit driven. You can believe what you want to believe but people live in garbage dumps in Brazil their whole lives and still are happy with what they’ve got. Humans are a bunch of whiners.. Go fly your airplanes!! 100 years ago, it wasn’t about what we could do for our future, it was survival. Everything is in God’s hands.

  2. Hopefully this will be the necessary push for the FAA to grant fleetwide drop-in approval for unleaded 100 avgas. GAMI’s G100UL is leading the way, but maybe this will streamline the process for Swift’s 100 octane unleaded fuel. Whether it’s “reasonable” to assume leaded avgas emissions measurably contribute to health issues, it is an indisputable fact that lead is not good for aircraft engines, aside from the octane boost it provides.

    • It is an indisputable fact that I don’t need 100 octane for my aircraft engine.
      It is an indisputable fact that no-lead alternatives were doable for the last 40 years.
      Only conclusion I can draw is that there was no money in making better fuel at lower cost that would benefit the better bulk of GA aircraft. Think again, it’s not about health of engines nor people; never was.

    • The GAMI G100UL IS a drop-in replacement for all piston aircraft engines as per the FAA STC issued about a month ago.
      The entire fleet, Every one of them. 100% compatible with 100LL.
      George Braly said in an interview right after the list at that time was 34 pages long in 10 point font.

      • I should have been more clear. I meant a true drop-in replacement that doesn’t require an STC, like G100UL will.

  3. People can say, claim, or more often by a wide margin, FOLLOW whatever they want. I still have serious doubts that 100L is a significant health threat when used to the miniscule degree that is general aviation. You want to tell me that there is no political component to this, pushed by people who have no formal education in the issue and, frankly, probably wouldn’t be smart enough to comprehend actual science if their life depended on it? Political correctness and expediency, but when you reduce it to the most basic human level, jealousy that a small component of society is allowed to use anything with lead is driving the bus here. I’ll be fine with buying G100UL, or whatever it’s called, but the premise behind producing it instead of 100LL is one of the most overblown, contrived, crusades in modern history. Whatever. I’m sick of hearing this drum.

    • The same argument can be made for all the brew ha ha about global warming er climate change. So far, all the nonsense about more and more intense hurricanes and similar weather is just that according to all the records. The avoided and unmentioned benefits of increases in atmospheric carbon dioxide include increased vegetation, forest, and crop growth and production. Yes there is a drought in the west, not the first or the longest according to the data, and not the last, but resulting fires are not the result climate change, but of decades of the same ignorant special interest groups that have dictated forest management policies that stopped logging, locked up forests, etc. Removing lead from aviation fuel is probably going to be good for engines but will have no effect on the environment or the populous.

  4. “EPA Proposes Endangerment Finding”
    What: After all these years 100LL is suddenly found dangerous?
    George Braly and Tim Roehl busted buns developing and proving G100UL. Our FAA jerked a knot in GAMI’s string by moving the goalpost at every turn. Health and Tetraethyllead supply concerns aside: Lead fouled plugs and stuck valves are a long neglected safety concern. The FAA needs to become the safety related force moving this transition forward. Sooner rather than later!

    • If I understand correctly, the EPA wanted to make an engagement finding on 100LL when auto gas went unleaded, but there was an exception made that it would pose a safety issue because no suitable alternative was available. It’s no coincidence that they’re now making the engagement finding with a true replacement for 100LL now (or rather, soon to be) available.

  5. What I find disheartening about the comments so far is how little attention people are paying to the recent events in the process, or what has actually been happening with the unleaded fuels.
    I assume these are also from pilots that will be directly affected by the outcome but don’t care enough about it to stay well-informed.
    Then there are those that just make crap up form their own confirmation bias and disregard reality.

  6. Another “The sky is falling” lie from Government and environmentalists. “It’s killing the children”!!! Right out of the Democrat playbook. If they are that concerned, let them subsidize and help speed up production of G100UL. You think this leaded conversation is bad? Wait until they tell us all we have to go electric….Think in November!!

  7. Californians accept $7/gallon auto fuel with only mild grumbling, so $14/gallon avgas shouldn’t mark the end of everything.

    So, what’s next on the green agenda?

  8. This is another example of wanting 100% regardless of the logic. The lead put out by GA planes is miniscule and if an honest study was done the harm it causes is non existant. But we live in a world where people want absolutes anymore and are often worked into hysterics to get it. There is a woman who lives near GAI and she is in constant hysterics writing the county council about the lead fuel. Never mind the airport has been there for 60+ years and that she moved under the flight path.

    • It doesn’t actually matter how much or little of an actual health impact 100LL poses. What does matter is that lead is well known to be toxic to humans, and that there are enough people who live near an airport who are using the leaded fuel as a reason to shut down the airport that they knew was there. The approval of an unleaded fuel removes one more “tool” the anti-GA people have to use against us.

  9. I just did a search of the National Library of Medicine using the search term, “lead toxicity.” The search revealed 48,751 articles published since the year 1899 (yes, 123 years ago). As others have noted above, lead is among (if not the) most well studied toxin in all of history.

    The idea that the small amount of tetraethyl lead in aviation fuel can’t harm anybody is an exercise in false reductionism. Lead isn’t the only neurotoxin floating around in our modern world. The effect of each added bit of neurotoxin is, at least, additive to the effect of all the other neurotoxins out there (if not, as occurs with other toxicants, multiplicative with their effects). Our scientific knowledge of the adverse effect of lead now shows, pretty clearly, that any measurable amount of lead in the blood of children is harmful to their nervous systems.

    It isn’t like we didn’t saw this coming. Physicians and industrial toxicologists opposed the addition of TEL to motor fuel in the 1920s because, even then, it was clear that an epidemic of lead toxicity would result (they were right). It was removed from other motor fuels some 50 or so years ago.

    And, for what it’s worth, I am a pilot with 1400 hours, I currently own and fly an airplane I built, I own four motorcycles and an antique car (not including my daily driver). I am not opposed to motorsports, obviously.

    Also, I would suggest that as an environmental epidemiologist and occupational medicine physician for 30 years, I do have a formal eduction on the topic and I believe I am smart enough to understand the science and to have an informed opinion about it.

    So, everyone is entitled to their own opinions. But, denigrating those who think removing lead from avgas isn’t the worst thing in the world as politically motivated, uneducated, unintelligent, and jealous, just isn’t helpful.

    • Im not sure which is more deliterious to a society, a lack of context or plain old fashioned autocracy.
      I was first in line 40 years ago with my O-320 to not run lead nor 100 octane.
      I was tacitly forced to run leaded gas and high octane and endure the associated service costs.
      Once again I’ll be forced to use the wrong octane and pay more.
      Thank you sir may I have another.

  10. Isn’t it time for the FAA to allow pilots to choose their fuel? Seriously, what pilot is going to put fuel into their EXPENSIVE AND BELOVED aircraft to damage it? Do they really think pilots are so stupid that they WANT to fall out of the sky?

    Most people follow mfr. recommendations for what fuel to put in their car. The NTSB doesn’t get involved in that. Enough time has been wasted on this nothing burger. If a particular engine needs hoses changed to properly use a particular fuel, that should be easy to do. STC’s are another form of tax. We don’t need more taxes.

    On another note, as many above have already observed, the EPA has NOT proven leaded fuel is an environmental danger. They “allow” certain ppm limits of lead and far more dangerous chemicals in water supplies, foods, cosmetics, etc. Where is the proof of extensive lead contamination?

  11. Regardless of the EPA findings, lead needs to be phased out. There is ONE manufacture of tetraethyl lead.. If that one supplier shutdowns/experiences issues, then the entire GA fleet and industry is in immediate danger. Might as well be sure we have a large quantity if replacement fuel, when we have the opportunity.

  12. As a physician I have little concern that the lead in our Avgas poses a measurable public health threat but I’d be open to evidence to the contrary. Much of the anti-100LL/anti-GA/anti-small airport sentiment is financially and politically motivated.

    With the current political climate I doubt that evidence will be forthcoming. Science is not followed.

    With that said I know my airplane would be better without lead, however my wallet will likely be further violated.

  13. One MAJOR benefit for GA specifically, and the country in general is to STOP the mandate to contaminate our fuel with alcohol, and starting right away we could encourage the distribution of Mogas on airports.

    It would not solve the lead (presumed) problem but would mitigate it, and our motors and wallets would be better off.

    • Mogas–absolutely agree. At the airport I manage in Minnesota, we installed a self-serve Mogas (with assistance of Minnesota Dept. of Aeronautics) pump when the STCs first came out. We control the quality–we buy ONLY from a local refinery, because we receive a “birth certificate” with every load–octane (minimum 94) batch number (for traceability), Reid Vapor pressure (to assure no vapor lock), and handled by a transport company that dedicates transports to aviation auto ONLY.

      It pays off, not only for aircraft owners, but for us–A few years ago, we had a BT-13 coming back from Oshkosh–the pilot filled with auto gas. A few days later, I received a letter–the pilot was an attorney, and claimed “we must have got some bad gas.” I replied “You picked the wrong people to tell THAT FAIRY TALE TO!”–and sent him a copy of the fuel specifics. Never heard from him again.

      HOWEVER–despite all of the precautions and documentation, we still only sell 1/4 of the gallons of autogas than we do of 100 octane–and our auto gas is $5.35 a gallon compared to $6.65 for 100 octane–people just don’t make the change–we still hear “I’ve HEARD that auto gas is bad for your engine!”

      Your point is well taken–we should be promoting auto gas–and the industry should do a better job of educating pilots and eliminating their fears about auto gas–and with the passage of time and gained experience, leaded aviation fuel will eventually die of its own. Without government interference, “the market will always prevail.”

      • Wow! That would be perfect for my engine, wish I had access to it instead of the 100LL I’m forced to use.

  14. Close tie between the EPA and Dept of Ed as to which is the most useless. If I could be King for a day I’d abolish both and stop all tax with holding making folks mail the gov a check to pay taxes each month. Just as the issue was making progress here comes the fools in DC to erase any gain and make matters much worse.