Sodium (CASRN 7440-23-5) is used frequently in a variety of compounds in industrial settings. The pure alkali metal is used in several small-scale and industrial-scale chemical reactions and as a coolant in certain types of reactors; it is also present in specific types of lamps and light bulbs. Although sodium is ubiquitous in the environment in its ionic form, pure sodium does not exist in nature and must be produced industrially. It is extremely water reactive, forming hydrogen gas and lye (NaOH). While sodium compounds are numerous and vary greatly in their chemical and toxicological profiles, it is generally sodium's counterion in these compounds that determines any toxic effects; this is largely due to the ubiquity of sodium ions in the environment, foods, and drinking water, as well as the biological demand for sodium ions for a large array of cellular processes. Dermal contact and inhalation are the primary routes of exposure to pure sodium, and the secondary formation of hydroxide ion at the site of exposure gives rise to the primary acute toxicological effects of the material.
Gad, S. C. (2014). Sodium. In Encyclopedia of Toxicology: Third Edition (pp. 325–326). Elsevier. https://doi.org/10.1016/B978-0-12-386454-3.00928-3