Man, that's fascinating, full study here [1].
I wonder how the Lithium is entering the food chain? Given they've tested drinking water, food, and air.
Dust from processing? occupational exposure? unscrupulous recycling operations? but Lithium isn't a heavy metal so exposure would have to be ongoing.
Definitely need to test some additional cities and try and understand what's going on here. While concerning these blood levels are at 3% of the doses typically studied in psychiatric conditions. There's some potential public health benefits to low level lithium exposure actually [2] but at the same time you don't want to be unintentionally exposing pregnant folks.