https://www.readymontereycounty.org/emergency/2025-moss-land...
As with all testing of this sort that I've ever seen, third parties do the testing and analysis.
I mention the air as an example of fear getting out waaaaaay in front of any risks. Testing the air would be pointless, 20 miles upwind. The metallic taste was either from other sources or psychosomatic.
The health risks of battery fires have been mostly evaluated in the context of fire fighting, where, air metals are a concern, but only in confined spaces. Nickel is the primary concern there. After reading about these, my only fears were for the workers for nickel production.
I am very very concerned about air quality, but the real risk there is from car traffic, specifically the tire microplastics and brake dust. There are big and measurable health effects from that, where even reducing traffic near schools by 10% could actually impact lives. However because people drive cars and are used to the bad health effects, nobody is scared of the negative health from cars. Instead the human mind focuses on new things because they are new, not because of the relative risk. For decades there were natural gas smokestacks pouring exhaust over the strawberry fields, the batteries that replaced them (to make use of the big power lines) are a huge improvement to human health, even with the fire.