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EC number: 234-522-7
CAS number: 12007-92-0
A number of in vitro mutagenicity
studies, including bacterial mutation assays in Salmonella
typhimurium and Escherichia coli, gene mutation in mammalian
cells (L5178Y mouse lymphoma, V79 Chinese hamster cells, C3H/10T1/2
cells), bacterial DNA-damage assay, unscheduled DNA synthesis
(hepatocytes), chromosomal aberration and sister chromatid exchange in
mammalian cells (Chinese hamster ovary, CHO cells) have been carried out
on boric acid and one study on disodium tetraborate decahydrate. No
evidence of mutagenic activity was observed.
All the in vitro data indicate no
mutagenic activity. In addition the single in vivo study on boric
acid also indicated no mutagenic activity.
These studies were 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
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
under CSR section 5.1.3, which corresponds to IUCLID section 7.1
(toxicokinetics, metabolism and distribution endpoint summary).
WHO. Guidelines for drinking-water quality,
Addendum to Volume 1, 1998
Short description of key information:
In vitro gene mutation studies in bacteria (Stewart, 1991) in vitro gene mutation studies in mammalian cells (Rudd, 1991) and in vitro cytogenicity studies (NTP, 1987) concluded that boric acid is not genotoxic under the conditions of the studies. In addition the results of an in vivo bone marrow cytogenetic assay (chromosome aberration assay, O’Loughlin 1991) also showed boric acid to be non genotoxic.
Cytotoxicity observed at 5 mg/mL in the in vitro gene mutation studies in mammalian cells (Rudd, 1991).
Endpoint Conclusion: No adverse effect observed (negative)
No classification is required for sodium
pentaborate regarding genotoxicity as all results were negative in the
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