I spent 20 minutes trying to find this reference and could not find anything convincingly close enough. It is a sci-fi reference or something that happened in our world? The only thing I could find was FireFly related. My concern in this case would be chronic toxicity, which does as you say occur in some cases at lower than pharmaceutical dosage levels. I would only be campaigning for raising Lithium in towns <25% percentile to a level found in towns in the 75% percentile. This would be relatively simple to communicate to people, and you could point to a road down the street from which people's Grandparents grew up and demonstrate that you would simply be replicating amounts found in that town naturally. I think what is more disturbing is the concept that most people have no idea what is in their water, not that we could arbitrage minerals between different towns and try to come to some kind of optimal mineral content. In the study I reference, the spread between "highest" and "lowest" Lithium content is between ~2000x and ~1000x less than is currently used in the pharmaceutical. So if <10% of Lithium patients have any signs of toxicity (real number, around 10%) and 1% have life threatening toxicity, we could (perhaps not perfect math) assume that only 0.001% of people would experience a similar issue in dosages of 1000x less. My thought is that dosages at that level are akin to living in an area with high Lithium naturally, or eating lots of seafood, and that people would at least consider it, if you could reduce the rate of suicide by 50%. I could be wrong though, lots of opposition to this thesis, including here, including among people who no doubt know far more science than I do.