NAAA this week submitted comments to the EPA on ethylene dibromide (EDB) and its use in AvGas/100LL. The EPA included EDB on its list of the first 20 “high-priority” chemicals for risk evaluation. The EPA is required by law to designate 20 chemicals as high priority and 20 chemicals as low priority by December 2019. Those chemicals designated as high priority are required by law to receive a completed risk evaluation within 3.5 years. If the evaluation finds an unreasonable risk for EDB then EPA must develop risk management requirements, which could include limitations on the use of EDB or a ban.

NAAA’s comments explained EDB is almost exclusively used in tetraethyl lead (TEL). TEL in turn is used in AvGas, or 100LL, the only available fuel for piston-engine aircraft. TEL is the only effective octane-booster for “high-performance piston-powered aircraft.”  To date, there is no known substitute for TEL in this use.  EDB in the TEL functions as a lead “scavenger” to avoid a buildup of lead deposits within the engine. A buildup of lead deposits can affect the performance and reliability of the engine. The lead is required in AvGas to prevent engine knock which can cause sudden engine failure, a catastrophic and likely fatal occurrence for an aircraft.

The comments went on to explain that while aviation gasoline comprises a small percentage of the fuel market, all piston aircraft engines will run on (leaded) aviation gasoline (100LL or AvGas); 100LL remains a “single fuel” solution for piston-engine aircraft. While AvGas is the only remaining transportation fuel that contains lead, the FAA and aviation industry are working extensively to find a suitable alternative for the 167,000 piston-engine aircraft in the U.S. that can only be fueled with AvGas. This is primarily being done through the FAA-established Unleaded Avgas Transition Aviation Rulemaking Committee, which in turn recommended creating the Piston Aviation Fuels Initiative (PAFI).

If AvGas were not available, aircraft that require TEL would be left without any approved fuel, resulting in those aircraft being grounded until such time as an alternative fuel could be developed or the engine manufacturers develop a procedure for de-rating the engines (operating them at reduced power). This is not an option for the nearly 20 percent of the agricultural aviation fleet that needs this fuel to perform its necessary role for agricultural production.

The comments concluded by summarizing that EDB is not a good chemical for an EPA risk assessment because there is currently no alternative and the FAA and aviation industry are working vigorously to find a solution.