Airport authorities in the most populous U.S. county are expediting the transition from leaded to unleaded aviation gasoline.

The Los Angeles County Board of Supervisors late last year directed that UL94 unleaded avgas be made available at Whiteman Airport in Pacoima, California, which is facing calls for its closure due to lead emissions from piston-engine aircraft. The transition plan has been expanded to make UL94 available by June at four other county-owned airports.

Plans also call for supplying unleaded avgas at Brackett Field, Compton/Woodley, Gen. William J. Fox and San Gabriel Valley airports, according to the county’s Department of Public Works (DPW).

“The county will encourage the use of UL94 by helping aircraft operators obtain FAA certification, which enables certain airplanes to use the fuel, offsetting the higher cost of UL94,” a DPW spokesperson said in response to an inquiry. “The ultimate goal is to discontinue the storage and sale of leaded aviation gasoline at these airports once an unleaded option is widely available for all piston-engine aircraft.”

The transition by Los Angeles County follows that of one of its major cities—Long Beach—where the City Council approved a plan to reduce lead emissions from piston aircraft in late 2022. Last August, fixed-base operator Signature Aviation received the first delivery of UL94 at city-owned Long Beach Airport (LGB).

Since its initial approval, the City Council has taken a series of steps to incentivize both the delivery and use of unleaded avgas, which is offered at LGB in addition to the 100 Low Lead (100LL) avgas required by high-performance piston aircraft.

The council voted in December 2022 to waive fuel-flowage fees per gallon of unleaded avgas pumped at LGB for three years. In November 2023, it approved reimbursements of up to $300 for owners of LGB-based aircraft who obtain the necessary supplemental-type certificate to burn unleaded fuel.

On Jan. 23, the City Council voted 9-0 to approve a subsidy program to offset the cost differential between unleaded fuel and 100LL. Councilors appropriated $200,000 to implement the Unleaded Aviation Fuel Subsidy Program, which will be covered by airport revenue.

The sale price of UL94, the only unleaded avgas available at LGB, can be $2-4 more per gallon than 100LL, presenting a barrier to its widespread adoption, the city said.

“By subsidizing the transition to unleaded fuel, Long Beach Airport is leading the way on this pressing national issue,” said Mayor Rex Richardson. “We began down this path in October 2022 and we are proud to take this next step. We know this environmental issue is of great concern to our community, and we’re proud to play a leading role in enacting change in the aviation industry.”

The State of California in general appears to be leading the U.S. transition to unleaded avgas. In addition to LGB, Oxnard, Santa Monica and Van Nuys airports supply UL94 in Southern California, as well as Hayward Executive, Reid-Hillview, San Carlos and San Martin airports farther north. Last December, the Livermore City Council approved a resolution requiring unleaded fuel be made available at city-owned Livermore Municipal Airport near Oakland within two years.

Supervisors in Santa Clara County ignited the transition to unleaded avgas in late 2021, when they moved to fully replace 100LL with UL94 at county-owned airports as of January 2022. The supervisors took that step in contravention of FAA grant commitments after a study revealed elevated blood-lead levels in children living near Reid-Hillview Airport in San Jose.

In addition to requiring that unleaded avgas be made available at Whiteman Airport, Los Angeles County Supervisors have proposed the county’s Public Health Department “determine if the data on blood-lead levels in children living in proximity of the airport have any statistical correlations to the airport,” according to county Aviation Commission meeting minutes.