Potassium fluoroborates and potassium fluorohydroxyborates, exothermic reaction products of boron and potassium hydroxides and fluorohydroxides

Additional toxicological data

Administrative data

Endpoint:

additional toxicological information

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

No data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Meets generally accepted scientific standards with acceptable restrictions. This study is conducted on an analogue substance. Read-across is justified on the following basis: In aqueous solutions at physiological and acidic pH, low concentrations of simple inorganic borates such as boric acid, disodium tetraborate decahydrate, disodium tetraborate pentahydrate, boric oxide and disodium octaborate tetrahydrate will predominantly exist as undissociated boric acid. At about pH 10 the metaborate anion (B(OH)4-) becomes the main species in solution (WHO, 1998). This leads to the conclusion that the main species in the plasma of mammals and in the environment is un-dissociated boric acid. Since other borates dissociate to form boric acid in aqueous solutions, they too can be considered to exist as un-dissociated boric acid under the same conditions. For comparative purposes, exposures to borates are often expressed in terms of boron (B) equivalents based on the fraction of boron in the source substance on a molecular weight basis. Some studies express dose in terms of B, whereas other studies express the dose in units of boric acid. Since the systemic effects and some of the local effects can be traced back to boric acid, results from one substance can be transferred to also evaluate the another substance on the basis of boron equivalents. Therefore data obtained from studies with these borates can be read across in the human health assessment for each individual substance. Conversion factors are given in the table below. Conversion factor for equivalent dose of B Boric acid H3BO3 0.175 Boric Oxide B2O3 0.311 Disodium tetraborate anhydrous Na2B4O7 0.215 Disodium tetraborate pentahydrate Na2B4O7•5H2O 0.148 Disodium tetraborate decahydrate Na2B4O7•10H2O 0.113 Disodium octaborate tetrahydrate Na2B8O13•4H2O 0.210 Sodium metaborate (anhydrous) NaBO2 0.1643 Sodium metaborate (dihydrate) NaBO2•2H2O 0.1062 Sodium metaborate (tetrahydrate) NaBO2•4H2O 0.0784 Sodium pentaborate (anhydrous) NaB5O8 0.2636 Sodium pentaborate (pentahydrate) NaB5O8∙5H2O 0.1832 References: WHO. Guidelines for drinking-water quality, Addendum to Volume 1, 1998.

Data source

Reference

Reference Type:

publication

Title:

Effects of single and repeated exposure to biocidal active substances on the barrier function of the skin in vitro.

Author:

Buist HE, van de Sandt JJM, van Burgsteden JA & de Heer C

Year:

2005

Bibliographic source:

Regulatory Toxicology and Pharmacology 43: 76 – 84.

Materials and methods

Type of study / information:

The influence of repeated and single exposure to boric acid on the skin barrier was investigated in vitro using static diffusion cells from cryopreserved human abdominal skin from 7 female donors.

Test guideline

Qualifier:

according to guideline

Guideline:

other: No data

Deviations:

not specified

Principles of method if other than guideline:

The influence of repeated and single exposure to boric acid on the skin barrier was investigated in vitro using static diffusion cells from cryopreserved human abdominal skin from 7 female donors. The dermis was partially removed using forceps and scissors and the average skin thickness was 0.702 ± 0.062 mm. The skin preparations were exposed to 10 μL/cm2 of a solution of boric acid for 4 h (single exposure) starting 4 h after the onset of the experiment or for 3 times 4 h (repeated exposure, starting at 0, 24 and 48 h respectively). The test material was tested at 3 concentrations, representing the range of concentration in which it may be present in products. Each exposure period was finished by washing off the test substance using 4 cotton swabs humidified with 3 % Teepol solution and subsequently drying the skin preparations using 2 dry cotton swabs. The same procedure was applied ot the control skin. All skins were washed three times in order to control fora a possible effect of the washing procedure on skin permeability. For each concentration the single and multiple dosing experiments were always performed with skin from the same donor wiht controls performed in parallel. The integrity of the skin preparations were assessed prior to the start of the experiment by determining the permeability coefficient (Kp) of tritiated water. In addition [14C]propoxur was used as a marker of skin permeability by applying at the end of the exposure period. During the following 3 h samples of receptor fluid were collected for every hour and assayed for tritated water and 14C-radioactivity by liquid scintillation counting. Fluid was replaced by adding fresh receptor fluid after each sampling and the amound of radiolabelled marker molecules that had penetrated the skin was plotted against time.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Boric acid

EC Number:

233-139-2

EC Name:

Boric acid

Cas Number:

10043-35-3

Molecular formula:

H3BO3

IUPAC Name:

Boric acid

Details on test material:

- Name of test material: Boric acid
- Analytical purity: > 99 %

Results and discussion

Any other information on results incl. tables

No clear and constant effect was noted on skin barrier function following boric acid application.

Applicant's summary and conclusion

Conclusions:

The influence of repeated and single exposure to boric acid on the skin barrier was investigated in vitro using static diffusion cells from cryopreserved human abdominal skin from 7 female donors. No clear and constant effect was noted on skin barrier function following boric acid application.
Read-across is justified on the basis detailed in the rationale for reliability above. This study is therefore considered to be of sufficient adequacy and reliability to be used as a supporting study and no further testing is justified.