Everything you're quoting is at theraputic levels for bipolar disorder, way above those added to water. It occurs naturally in some waters at low levels.
Apparently "low-dose" lithium is not without side-effects either [1]:
"In general, the only significant problems with low-dose lithium are tolerability and thyroid issues. About 1 person in 10 to 15 gets dull, flat, and “blah” (the “lithium made me a zombie” effect, overrepresented in online testimonials). I explain to my patients in advance that if this happens, we’ll give up on it. This adverse effect does not diminish with time and generally persists even if the dose is reduced. Then there’s weight gain: is it dose-related? To my knowledge, this has not been established. I nurture some hope this is so.
That leaves the thyroid issue. Thyroid-stimulating hormone (TSH) levels must be monitored even with low-dose lithium. In women, induction of hypothyroidism is extremely common—and almost predictable in women with a family history of thyroid problems. The latter may be an uncovering of an autoimmune disorder. If your patient has a high-normal TSH value before lithium (eg, 2.5 mIU/L or above, and certainly above 3 mIU/L), she is at even higher risk for lithium-induced hypothyroidism.1
So monitor closely, and even more closely in those at greater risk: for example, every 6 weeks until a trend (up, or flat) is established. Once you have established that the TSH level is not rising, the probability of later hypothyroidism due to lithium is much diminished and you can back off to getting a TSH level with your 6- to 12-month check of creatinine.2"
A therapeutic low dosage would still be considerably higher compared to the levels that has been suggested to add in drinking water.
Normal therapeutic dosage is around 300mg and 500mg lithium per day, and blood levels should be around 0,5-1,2 mEq/L. A concentration at 0,7 mEq/L as quoted in the article is within normal values and dosage, and not really considered low.
The real dangers is NSAIDS or ACE inhibitors which can push your concentration up quite rapidly, but that's easy to avoid, and still not very relevant until you're at around 1,0 mEq/L, give or take. Concentration above 1,6 mEq/L is considered an overdosage and comes with a lot of risks, thyroid being one of them.
Anyone put on a therapeutic dosages of lithium will have their blood checked frequently, often starting with twice a week for an extended period.
But again - in dosages that are 100-1000x times higher than that they want to add in the drinking water.
I hike to a desert oasis in the Mohave Desert of California where a crack in a cliff wall has scalding hot water seeping down the cliff wall, which happens to have a high lithium content. There is a creek the hot water flows into, and people have sand bagged various hot pools to soak. The placed is called "Deep Creek Hot Springs", and it internationally famous. About a decade ago I looked up the lithium content, it is published, and everyone there talks about how calming the hot springs are, lasting for days.
