None. Lithium only starts being psychotropic above a few mg per day (typically hundreds of mg per day for therapeutic, but it is suspected by some to be active

None. Lithium only starts being psychotropic above a few mg per day (typically hundreds of mg per day for therapeutic, but it is suspected by some to be active well below that). The intake from the environment would be micrograms/day, if not even less, above natural background. There are water sources with far higher natural concentrations.