The US Environmental Protection Agency released its draft risk evaluation of ethylene dibromide on Wednesday. The agency preliminarily concluded that the compound, used to scavenge lead in a type of airplane fuel, poses an unreasonable health risk to people who work with it.
The most common use of ethylene dibromide in the US is as an additive to a leaded aviation fuel called avgas. The brominated compound reacts with lead oxides and sulfides created during combustion. Left untreated, the lead compounds deposit on the engine, causing “knock.”
Avgas is typically used in 2- to 10-passenger planes. Large commercial airplanes don’t use leaded fuel. Other uses of ethylene dibromide include as a reactant in pigment and dye manufacturing, as a fuel additive for petroleum refineries, and as a lab chemical.
The EPA preliminarily found that of the 12 uses of ethylene dibromide, 10 pose an unreasonable risk to human health through skin contact or inhalation by people who work with the compounds in the lab or during airplane refueling. The risks include cancer, harm to the reproductive and gastrointestinal systems, and liver damage.
Ethylene dibromide is one of the “next 20” chemicals that the agency designated in 2019 as a priority for risk evaluation under the Toxic Substances Control Act (TSCA). An earlier EPA program singled out an initial 10 chemicals for evaluation under TSCA, the major US law that covers the manufacture, import, and use of chemicals that may cause harm to humans and the environment.
The EPA risk assessment for ethylene dibromide is open for public comment until Oct. 19. The Federal Aviation Administration is overseeing a separate effort to eliminate lead from all airplane fuels, including avgas, by 2030.
TSCA requires that the EPA consider all reasonably available information and use the best available science to make policy decisions, says Ryan Schmit, former policy adviser at the Office of Pollution Prevention and Toxics and now with the law firm Bergeson & Campbell. “Allowing additional time for public comment is one way for the EPA to support meeting these obligations and also to help avoid any surprises at the end,” he says.
The EPA started the review process for ethylene dibromide in 2019 and was supposed to be finished with the assessment by mid-2023.
Industry has long complained that TSCA reviews became too slow after a 2016 revamp of the law. Republicans and Democrats agree that the process is slow but disagree on how to speed it up. TSCA’s fee authority, which allows the EPA to collect fees from chemical manufacturers and importers that help pay for the reviews, expires Sept. 30. Some legislators see the fee authority renewal as an opportunity to revamp the law, and Republicans in the House and the Senate have created draft bills with changes to TSCA. Both bills are still in progress.
