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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:
Cellular changes in boric acid-treated DU-14S prostate cancer cells.
Author:
Barranco WT & Eckert CD
Year:
2006
Bibliographic source:
British Journal of Cancer 92: 884 - 890.

Materials and methods

Type of study / information:
Boron-induced changes in human prostate cancer cell lines were assessed.
Test guideline
Qualifier:
according to
Guideline:
other: No data
Deviations:
not specified
Principles of method if other than guideline:
Boron-induced changes in human prostate cancer cell lines were assessed.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material: Boric acid

Results and discussion

Any other information on results incl. tables

Pharmacologically relevent levels of boric acid induce the following morphological changes in cells: Increases in granularity and intracellular vesicle content, enhanced cell spreading and decreased cell volume. Increases in β-galactosidase activity were also noted. Boric acid also caused a dose-dependent reduction in cyclines A-E as well as MAPK proteins. Treated cells displayed reduced adhesion, migration and invasion potential, along with F-actin changes indicative of reduced metastatic potential. Media acidosis in treated cells corrleated with an accumulation of lysosome-associated membrane protein type 2 (LAMP-2)-negative acid compartments.

Applicant's summary and conclusion

Conclusions:
Pharmacologically relevent levels of boric acid induce the following morphological changes in cells: Increases in granularity and intracellular vesicle content, enhanced cell spreading and decreased cell volume. Increases in β-galactosidase activity were also noted. Boric acid also caused a dose-dependent reduction in cyclines A-E as well as MAPK proteins. Treated cells displayed reduced adhesion, migration and invasion potential, along with F-actin changes indicative of reduced metastatic potential. Media acidosis in treated cells corrleated with an accumulation of lysosome-associated membrane protein type 2 (LAMP-2)-negative acid compartments.
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.