Diboron calcium tetraoxide

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Numerous studies have demonstrated the toxicokinetics of boric acid and borate salts in humans and experimental animals. At physiological pHs in the aqueous layer of mucosal surfaces, prior to absorption, simple inorganic borated salts are hydrolysed to undissociated boric acid, which are readily absorbed via oral and inhalation exposure. Boric acid is not expected to hydrolyse/react further due to the high energy required to break the B – O bond. Therefore, it is expected that there will be negligible parent compound, calcium metaborate, available systemically and boric acid will be the dominant and common compound in humans and experimental animals. Therefore, a read-across approach using boric acid data is considered appropriate to use, refer to Section 13.

In an in vitro bacterial reverse mutation assay (comparable to OECD test guideline 471), the source substance, boric acid, was not mutagenic in S. typhimurium TA 1538, TA 1535, TA 1537, TA 98 and TA 100 strains tested with or without metabolic activation.

In an in vitro gene mutation study in mouse lymphoma L5178Y cells (comparable to OECD test guideline 476), the source substance, boric acid, was not mutagenic with and without metabolic activation.

In an in vitro chromosome aberration assay, conducted in general compliance with OECD guidelines, the source substance, boric acid, was not genotoxic in Chinese hamster ovary cells with and without metabolic activation.

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to justification attached in section 13.

Reason / purpose for cross-reference:

read-across source

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Species / strain:

S. typhimurium TA 1538

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Conclusions:

Interpretation of results (migrated information):
negative

The study was performed according to Guideline 84-2 and is comparable to OECD 471. The test substance was not mutagenic in any of the strains tested with or without metabolic activation.

Reference 2

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14-05-91 to 12-08-91

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

yes

Remarks:

There is a failure to justify the maximum concentration of 2500 ug/plate

Qualifier:

according to guideline

Guideline:

other: US EPA 40 CFR Part 158; FIFRA, Section 158.340

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

EPA OPP 84-2

Deviations:

not specified

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Target gene:

Histidine

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Details on mammalian cell type (if applicable):

Not applicable

Additional strain / cell type characteristics:

not specified

Species / strain / cell type:

S. typhimurium TA 1538

Details on mammalian cell type (if applicable):

Not applicable

Additional strain / cell type characteristics:

not specified

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254 induced rat liver S9 at 4 % and 10 %

Test concentrations with justification for top dose:

10; 50; 100; 1000; 2500 µg/plate

Vehicle / solvent:

Water

Positive controls:

yes

Positive control substance:

sodium azide

Positive controls:

yes

Positive control substance:

9-aminoacridine

Positive controls:

yes

Positive control substance:

2-nitrofluorene

Positive controls:

yes

Positive control substance:

other: 2-Anthramine

Details on test system and experimental conditions:

METHOD OF APPLICATION: In water

DURATION
- Preincubation period: None

Evaluation criteria:

No data

Statistics:

No data

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Species / strain:

S. typhimurium TA 1538

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Additional information on results:

No data

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Conclusions:

Interpretation of results (migrated information):
negative

The study was performed according to Guideline 84-2 and is comparable to OECD 471. The test substance was not mutagenic in any of the strains tested with or without metabolic activation.

Reference 3

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to justification attached in section 13.

Reason / purpose for cross-reference:

read-across source

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Concentration related cytotoxicity (60 % reduction over controls at 5 mg/mL)

Conclusions:

Interpretation of results (migrated information):
negative

The test substance was not mutagenic but cytotoxicity observed at 5 mg/mL (maximum dose level).

Reference 4

Endpoint:

in vitro gene mutation study in mammalian cells

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

No data

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: 40 CFR Part 158 US-EPA-FIFRA, Section 156.340

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)

Deviations:

not specified

GLP compliance:

yes

Type of assay:

mammalian cell gene mutation assay

Target gene:

Thymidine kinase, TK locus of the L5178Y mouse lymphoma cell line

Species / strain / cell type:

mouse lymphoma L5178Y cells

Details on mammalian cell type (if applicable):

No data

Additional strain / cell type characteristics:

not specified

Metabolic activation:

with and without

Metabolic activation system:

S9 mix or other (Aroclor 1254 induced rat (Fischer 344) liver S9 fraction used at 1 %).

Test concentrations with justification for top dose:

0, 1.2, 1.7, 2.45, 3.5 and 5.0 mg/mL boric acid.

Vehicle / solvent:

No data

Positive controls:

yes

Positive control substance:

3-methylcholanthrene

Positive controls:

yes

Positive control substance:

other: Hycanthone methylsulphonate

Details on test system and experimental conditions:

METHOD OF APPLICATION: ROP plus 5 % heat treated horse serum

NUMBER OF CELLS EVALUATED: Approximately 600/dose

Evaluation criteria:

Mutations at the TK locus

Statistics:

No data

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Concentration related cytotoxicity (60 % reduction over controls at 5 mg/mL)

Additional information on results:

Concentration related cytotoxicity (60 % reduction over controls at 5 mg/mL).
Increase in ouabain resistance seen (not significant).

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Gene mutation assay results:

Concentration mg/mL	Number of mutant cells per 10^6cells ± SD				Comments give information on cytotoxicity or other
	Exp 1	Exp 2	Exp 1	Exp 2
	-S9	-S9	+S9	+S9
0	54 ± 10	42 ± 1	29 ± 10	36 ± 7
1.2	46 ± 28	38 ± 15	34 ± 0	36 ± 7
1.7	39 ± 17	31 ± 9	41 ± 7	49 ± 4
2.45	27 ± 3	32 ± 9	40 ± 16	36 ± 6	Minor cytotoxicity seen
3.5	31 ± 18	46 ± 1	41 ± 13	41 ± 6	Cytotoxicity seen
5	50 ± 22	41 ± 5	53 ± 2	47 ± 3	Cytotoxicity seen. Increase in + S9 in first study not reproduced.

Conclusions:

Interpretation of results (migrated information):
negative

The test substance was not mutagenic but cytotoxicity observed at 5 mg/mL (maximum dose level).

Reference 5

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to justification attached in section 13.

Reason / purpose for cross-reference:

read-across source

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Conclusions:

Test substance is not genotoxic with and without metabolic activation.

Reference 6

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

No data

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted to GLP and in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not effect the quality of the relevent results.

Qualifier:

equivalent or similar to guideline

Guideline:

other: Carried out to an internal NTP protocol, which generally complies with OECD guidelines.

Deviations:

not applicable

Principles of method if other than guideline:

Although this was carried out to an internal NTP protocol, it generally complies with OECD guidelines. Other literature data confirm the results. Also based on Galloway et al; 1985.

GLP compliance:

yes

Type of assay:

in vitro mammalian chromosome aberration test

Target gene:

Not applicable

Species / strain / cell type:

Chinese hamster Ovary (CHO)

Additional strain / cell type characteristics:

not specified

Metabolic activation:

with and without

Metabolic activation system:

S9 mix - Aroclor 1254 induced rat (Sprague-Dawley) liver S9 fraction

Test concentrations with justification for top dose:

With S-9: 500, 1000, 1500 and 2000 µg/mL.
Without S-9: 1000, 1600, 2000 and 2500 µg.

Vehicle / solvent:

Water

Positive controls:

yes

Positive control substance:

mitomycin C

Positive controls:

yes

Positive control substance:

cyclophosphamide

Details on test system and experimental conditions:

METHOD OF APPLICATION: In water
NUMBER OF CELLS EVALUATED: Not stated

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Conclusions:

Test substance is non genotoxic.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

In an in vivo micronucleus assay (comparable to the OECD Guideline 474) the source substance, boric acid, was not mutagenic.

Link to relevant study records

Reference

Reference 1

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to justification attached in section 13.

Reason / purpose for cross-reference:

read-across source

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

not specified

Negative controls validity:

not specified

Positive controls validity:

not specified

Conclusions:

Interpretation of results (migrated information): negative
The test substance was not genotoxic.

Reference 2

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

No data

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

other: US-EPA-FIFRA section 158.340 Guideline 84-2

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Deviations:

not specified

GLP compliance:

yes

Type of assay:

micronucleus assay

Species:

mouse

Strain:

Swiss Webster

Sex:

male/female

Route of administration:

oral: gavage

Vehicle:

Distilled water.

Details on exposure:

Mice given two doses (in 10 mL distilled water) by gavage.

Duration of treatment / exposure:

2 days

Frequency of treatment:

Animals dosed once per day.

Post exposure period:

No data

Remarks:

Doses / Concentrations:
0, 225, 450, 900, 1800, 3500 mg/kg bw/day
Basis:
actual ingested

No. of animals per sex per dose:

No data

Control animals:

not specified

Tissues and cell types examined:

No data

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

not specified

Negative controls validity:

not specified

Positive controls validity:

not specified

Additional information on results:

Clinical signs included rough fur and haunched position.

Conclusions:

Interpretation of results (migrated information): negative
The test substance was not genotoxic.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Justification for classification or non-classification

No adverse effects on the read-across substance, boric acid, were observed in an in vitro bacterial reverse mutation assay, in vitro gene mutation study in mouse lymphoma L5178Y cells, in vitro chromosome aberration assay in Chinese hamster ovary cells and in an in vivo micronucleus assay; therefore, in accordance to Regulation (EC) No. 1272/2008 no classification for genotoxicity is required.