Environmental Issues with Leaded Aviation Fuel Use in Arid Southwestern U.S.

Abstract: Despite advancements towards reducing lead in air emissions nationwide, leaded aviation gasoline (avgas) use in piston-engine aircraft remains a significant source of lead in the environment. In particular, lead emissions associated with general aviation (GA) airports in the Southwestern U.S. present unique challenges to airport owners, fixed based operators (FBOs), and municipalities as well as transportation and environmental regulatory agencies. Infrastructure upgrades necessary for transitioning to unleaded fuels can be costly for airports and FBOs, and compatible fuels may be more expensive or not consistently available from suppliers. Safety and compatibility concerns exist regarding switching to unleaded fuel for aircraft currently using 100LL fuel, which is widely available.
However, the environmental and public health ramifications associated with leaded avgas are appreciable, and these often can disproportionately affect lower income and environmental justice (EJ) communities, which are frequently located near airports. Transitioning to unleaded avgas would significantly alleviate the health burdens borne by these communities. In October 2023, the U.S. Environmental Protection Agency (USEPA) took action by issuing the "Finding That Lead Emissions From Aircraft Engines That Operate on Leaded Fuel Cause or Contribute to Air Pollution That May Reasonably Be Anticipated To Endanger Public Health and Welfare" (88 FR 72372), which provides the legal framework for the USEPA and the Federal Aviation Administration (FAA) to promulgate regulations to compel the aviation industry to cease leaded avgas use.
This presentation will cover how the unique climatic conditions in semi-arid and arid regions, such as in the Southwestern U.S., affect the source pathways, spatial distribution, and environmental persistence of lead contamination from aviation sources. For example, lead accumulation in soils may be greater than other regions where more precipitation is distributed more evenly throughout the year due to reduced soil infiltration depths and shortened biogeochemical processing timeframes. Stormwater runoff directed to arroyos or dry riverbeds, or windblown fines and particulate accumulation in these low-lying areas, may concentrate lead over shallower soils margins; thereby reducing the infiltration distance to underlying groundwater. Engineered structures that facilitate groundwater recharge or promote infiltration commonly used in arid climates may also provide an exposure pathway to groundwater.
After reviewing the environmental pathways for lead migration in the environment unique to arid climates, the direct implications to GA operations from regulatory changes will be discussed. The presentation will then review options for mitigating lead exposure to environmental media near airports as well as strategies transitioning to low-lead or unleaded options, and will then examine the feasibility, benefits, and challenges of adopting alternative fuels, like unleaded aviation gasoline (UL94) or jet fuel suitable for certain aircraft conversions.