“Unleaded” fuel is permitted to contain up to 50mg per gallon*; though this is a limit, none is permitted to be intentionally added.

100LL by comparison contains 550mg per gallon by intent.

* Sorry for the crazy mixed units; I didn’t write the regulations.

From car paints and tire balance weights.

There's likely trace elements in fuel. In the case of that area, the Capitol Expressway is a very busy highway system.

If RHV air quality is monitored, then so should some locations around the highway. In fact, there's enough cars surrounding the airport that it would influence air quality measurements inside the airport perimeter.

I mentioned the quake issue because I have seen documentation that RHV is part of the emergency response plan for transporting relief cargo.