Toxicological effects of inorganic boron compounds in animals: A review of the literature

Abstract

Boron is a ubiquitous element found widely distributed in the environment and is a normal component of a healthy diet. It is an essential micronutrient for plants, and there is evidence to suggest that boron is of nutritional importance, if not essential, for humans. The majority of toxicological studies have been reported on boric acid or borax. The inorganic borates display low acute toxicity. They are either not irritant or mild skin and eye irritants. They are not skin sensitisers, nor are they mutagenic or carcinogenic. The most sensitive endpoints of toxicity are considered to be effects on the reproductive organs, fertility in males, and developmental effects. The doses that cause these effects are far higher than any levels to which the human population could be exposed. The NOAELs from a rat developmental study (for a reduction on fetal weight) and from a fertility study considered to be the most appropriate for risk assessment were 9.6 mg B/kg bw/day and 17.5 mg B/kg bw/day, respectively. Man 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. Sodium perborate tetrahydrate did not display the same response as boric acid or borax in that no adverse effects were seen in the testis, and developmental effects were only seen at doses causing maternal toxicity. This indicates the need to consider the toxicity of certain borate salts individually and to assess their risks separately. © 1997 Wiley-Liss, Inc.