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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Administrative data

Link to relevant study record(s)

Description of key information

Absorption: 100% oral absorbtion, 0% absorption via inhalation and dermal route
Distribution: evenly trhoughout the body
Metabolism: no metabolism of the decomposition product boric acid
Excretion: within 24 h mainly via renal clearance

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential
Absorption rate - oral (%):
100

Additional information

General

No studies on the toxicokinetic properties of Sodium triacetoxyborohydride were available. However, it was shown that Sodium triacetoxyborohydrate decomposes with a half-life of 38 - 85 seconds upon contact with water (Widmer, 2005). The resulting reaction products are Acetic acid, Sodium acetate, Boric acid and Hydrogen gas, respectively (Gribble, 1979). Under physiological conditions, Acetic acid is usually fully ionized to acetate which represents a fundamental anion in physiological molecules, e.g. as part of the Acetyl coenzyme A. Thus, all results of the available toxicological studies could be seen as driven by the boric acid.

A number of detailed hazard assessments and reviews of the toxicology of boric acid and borates have been published by several authorities and regulatory bodies including WHO 1998, US EPA 2004, UK EVM 2003, EFSA 2004, HERA 2005 and ECHA 2008.

Basically, the overall outcome was that the toxicokinetic of boric acid and borates are similar in rats and humans with respect to absorption, distribution, and metabolism.

For comparative purposes, dose levels of boric acid and borates generally have been expressed in terms of boron (B) equivalents based on the fraction of boron on a molecular weight basis.

 

Absorption

In case of an uptake via oral, inhalation or dermal route, Sodium triacetoxyborohydride comes into contact with wet mucosa in the mouth, respiratory tract or sweat on the skin, and consequently decomposes to final products hydrogen and boric acid.

Oral absorption was evaluated in a study where Sodium triacetoxyborohydride was given repeatedly for 28 day at concentrations of 30, 100 and 300 mg/kg bw/d. No systemic effects were noted in –any of the tested animals, thus giving a NOAEL of 300 mg/kg bw/d (Braun, 2005). However, in an acute oral toxicity study where Sodium triacetoxyborohydride was given to female Wistar rats, the resulting LD50 was found to be >300 and <2000 mg/kg bw based on noted mortality and clinical signs (Arcelin, 2004). Thus, a clear oral absorption of substance as decomposition product boric acid was obvious. This conclusion is in line with the data from a chronic study with boric acid showing adverse toxic effects, e.g. testicular atrophy, so that the NOEL was determined to be 100 mg/kg bw for boric acid (Weir and Fisher, 1972).

In case of any dermal absorption, toxic effects similar to the effects noted in the acute oral study might be expected. However, even the concentration of 2000 mg/kg bw applied to skin of Wistar rats in an acute dermal toxicity study did not lead to any systemic effects (Bertl, 2005). Therefore, adsorption of Sodium triacetoxyborohydride via dermal route can be regarded as low or even as negligible.

 

Absorption via inhalation of Sodium triacetoxyborohydride is not expected to occur based on the low vapour pressure of <0.00001 Pa at 25°C.

In summary, human uptake of Sodium triacetoxyborohydride would be mainly via oral route with 100% absorption while absorption via dermal route and inhalation can be neglected.

  

 

Distribution

It is generally accepted that the main boron species in the plasma of mammals is un-dissociated boric acid since most of the inorganic borates exist predominantly as boric acid in dilute aqueous solution at physiological pH. This conclusion is supported by data from animal and human studies which demonstrated that absorbed boric acid rapidly distributes throughout the body water in humans and animals (ECHA, 2008). In both humans and animals, boron levels in soft tissue are comparable to plasma levels, while a greater concentration of boron in bone is observed relative to other tissues (2 - 3 times plasma levels).

 

Metabolism

After uptake, the decomposition product boric acid is not metabolised in either animals or humans, since the required energy would be very high with 523kJ/mol to break the B – O bond. In addition, boric acid is a very weak and exclusively monobasic acid that is believed to act as a Lewis acid, i.e., it accepts OH-.

Excretion

In both humans and animals, boron is excreted in the urine regardless of the route of administration within 24 h (ECHA, 2008). Rats and mice generally have faster rates of renal clearance than humans since the glomerular filtration rates as a function of body mass are generally higher in rats and mice than in humans (3 - 4 times slower).

 

Summary

Sodium triacetoxyborohydrate decomposes with a half-life of 38 - 85 seconds upon contact with water by liberating hydrogen and boric acid as final products. The uptake of Sodium triacetoxyborohydride as its – toxicological relevant decomposition product boric acid would be mainly via oral route with 100% absorption while absorption via dermal route and inhalation can be neglected. The absorbed boric acid is rapidly distributed throughout the body water and blood and is - excreted within 24 h mainly via renal clearance.

As a consequence of the -all data, Sodium triacetoxyborohydrate has low potential for accumulation.

 

References

European Chemicals Agency (ECHA) 2008: Annex XV transitional reports. Boric acid

Gribble G.W., Sodium borohydride in carboxylic acid media – New synthetic methology; Eastman Organic Chemical Bulletin, 51(1), 1979