Boron is a naturally-occurring metal-like element whose compounds are mined commercially for use in fiberglass, ceramics, borosilicate glass, detergents, flame retardants, and insecticides. Though it is present all over the world in tiny amounts, it is concentrated in ancient evaporated seabeds. The biggest mines in the US are in the Great Basin states of California and Oregon. Turkey is the largest producer worldwide.
Borax Lake, Oregon, once mined for borax, is now a protected site for rare, boron-loving chubb. (photo: Wikipedia)
Boron is an essential plant nutrient. It is not yet established if it is an essential nutrient for humans. It is relatively non-toxic to humans, and after a 2008 review for possible inclusion as an element subject to Safe Drinking Water Act regulation, the EPA opted leave it off the list of regulated impurities.
MEL clients most often ask for boron testing as part of the slate of tests required by the State of Maine for the agronomic re-use of residual wastes such as paper pulps, food wastes, wood ash, and lime mud.
Total or Soluble Boron?
The total boron test is for aqueous samples and solid samples, and it is the test required in Maine for Chapter 405.6 compliance. The soluble boron test is the test used in Massachusetts for the same purpose (screening residual waste before land application).
References
EPA Drinking Water Health Advisory for Boron (2008)