Lithium is a naturally occurring element. However it is not readily in the soil so can not reach the ground water by natural means. It requires mining and refining to be used.

In lower doses, lithium is used as a mood stabilizer in individuals with such conditions as bi-polar disorder, depression  and mania. In high doses it has been linked to heart disease, kidney disease and thyroid disease. It is unsafe for pregnant women, and can enter the breast milk and cause unwanted side effects in nursing infants.