Comparative toxicology of borates

Susan A. Hubbard

Inorganic borates, including boric acid, Na, ammonium, K, and Zn borates generally display low acute toxicity orally, dermally, and by inhalation. They are either not irritant or mild skin and eye irritants. Exceptions owing to physiochemical properties do occur. Longer-term toxicological studies have been reported mainly on boric acid or borax where the properties are generally similar on an equivalent boron (B) basis. The critical effects in several species are male reproductive toxicity and developmental toxicity. The doses that cause these effects are far higher than any levels to which the human population could be exposed. Humans would need to consume daily some 3.3 g of boric acid (or 5.0 g borax) to ingest the same dose level as the lowest animal NOAEL. No effects on fertility were seen in a population of workers exposed to borates or to a population exposed to high environmental borate levels. There is remarkable similarity in the toxicological effects of boric acid and borax across different species. Other inorganic borates that simply dissociate to boric acid are expected to display similar toxicity, whereas those that do not dissociate simply to boric acid may display a different toxicological profile.