It is not really common knowledge, but even though we stopped using leaded gasoline in cars back in the 1970s, the use of 100-octane leaded gasoline (aka 100LL) is still widely used for propeller-driven piston-engine general aviation airplanes. While these airplanes are complex machines and the consequences of an airplane engine stalling or not running properly are much greater than in a car, leaded gasoline does have a negative health risk. This risk is pronounced in areas within one-half mile of a general aviation airport.
Credit: Wikimedia
We have historically seen, and are still dealing with the remediation of, aerially-deposited lead in surface soils due to the use of leaded gasoline in cars along major highways. Even in residential neighborhoods. I would expect to see the California Environmental Protection Agency (EPA) Department of Toxic Substances Control (DTSC) expand their existing soil management plan for CalTrans sites to include general aviation sites.
In October, 2023 the U.S. EPA announced its final determination that emissions of lead from aircraft that operate on leaded fuel cause or contribute to air pollution and aerially-deposited lead in surface soils which may reasonably be anticipated to endanger public health and welfare under the Clean Air Act. 
Here at McAlister GeoScience, we have incorporated this risk due to proximity to general aviation airports using 100LL gasoline into our Phase I Environmental Site Assessments (ESAs) and we are the only firm doing so at this time. If you have any questions or comments on this, please feel free to Contact Us Today!