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Description of key information

The available information on boric acid suggests absorption from the gastro-intestinal tract can occur. Once absorption occurs, boric acid may be systemically distributed. Urine is likely to be the significant route of excretion. Limited bioaccumulation is anticipated basesd on the low partition coefficient and high water solubility. 

Key value for chemical safety assessment

Bioaccumulation potential:
low bioaccumulation potential

Additional information

Toxicokinetic behaviour.

The reference substance (BAGE) is unstable in water and hydrolyses within less than an hour to its hydrolysis products: Boric acid and glycerol.

Boric acid is considered to be the hydrolysis product of main concern, due to its known reproduction/developmental effects so the following assessment is made on boric acid, based on available data.

Boric acid is anticipated to be present under standard physiologically conditions.

Glycerol is not classified for human health according to CLP or DSD and is essentially non-toxic. Further toxicokinetic evaluation of glycerol has not been assessed.

Boric acid:

Absorption:

The molecule size and high water solubility of boric acid suggests that absorption across the gastro-intestinal tract may occur and provide a route of potential absorption following oral administration, potentially facilitating systemic distribution.

Results of the oral feed OECD Guideline 414 Prenatal Developmental Toxicity Study show evidence to support the absorption of boric acid.

Absorption may occur via the inhalation route. Acute inhalation studies showed no mortality but some clinical signs were noted in animals, indicating some absorption may have occurred. However, due to the low volatility of boric acid, inhalation is not considered to be a significant route of exposure.

Limited dermal absorption may potentially occur via the skin due to molecular size and water solubility of boric acid. However, an acute dermal toxicity study showed no mortality and only minor clinical effects, and a skin irritation study showed minimal irritation, indicating that dermal absorption is not significant.

Distribution:

Once absorbed, boric acid may be distributed systemically due to it's high solubility (i.e. in blood plasma). The reproduction/development effects of boric acid support systemic distribution.

The negative result for skin sensitisation suggests boric acid will not bind to carrier proteins in the circulatory systems.

The low octanol/water partition coefficient and high water solubility of boric acid indicates it is not lipophilic and would not accumulate in fatty tissues.

Metabolism:

There is no evidence to indicate boric acid influences hepatic metabolism.

The results of in-vitro genotoxicity studies do not show any evidence that the addition of a metabolising system enhanced or diminished the genotoxic potential of the substance.

Excretion:

As boric acid is highly water soluble it is anticipated that this would facilitate urinary excretion.