[slapshot]

Commercial jets in the US run on Jet-A, which is lead-free and kerosene-like. Adding 737 flights will not add any lead.

You are thinking 100LL ("low lead") Avgas, which is gasoline-like and used for small propeller planes (think San Carlos airport, not SFO).

It's a general aviation problem, not a commercial aviation problem.

*(edited to swap San Carlos, not San Mateo)