It's always been a real estate issue with KRHV.
The nearby busy highways emit vastly more emissions than trainers, likely including lead.
What city councils refuse to acknowledge is that once you close a city airport, you can never build another one. This is especially an issue in an earthquake zone.
Is that a bad thing? A substantial fraction of the population uses the local highway on a daily basis, whereas very very few people use small local airports with any similar frequency
100LL by comparison contains 550mg per gallon by intent.
* Sorry for the crazy mixed units; I didn’t write the regulations.
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.