Diboron trioxide

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vivo

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: see 'Remark'

Remarks:

GLP guideline study. 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. 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:

study report

Title:

Unnamed

Year:

1982

Report Date:

1982

Materials and methods

Test guideline

Qualifier:

according to

Guideline:

other: FIFRA (40 CFR 163)

Deviations:

no

GLP compliance:

no

Remarks:

Study pre-dates GLP

Test material

Reference

Name:

Unnamed

Type:

Constituent

Details on test material:

- Name of test material: Boric acid
- Molecular formula: H3BO3
- Molecular weight: 61.8
- Smiles notation: B(OH)3
- Substance type: Inorganic
- Physical state: Solid
- Analytical purity: >99.0 % w/w
- Lot/batch No.: OA 107-3
- Stability under test conditions: Stable
- Other: White powder and odourless

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan F Plummer
- Weight at study initiation: 1623 - 2922 g

Test system

Type of coverage:

occlusive

Preparation of test site:

abraded

Vehicle:

physiological saline

Controls:

no

Amount / concentration applied:

TEST MATERIAL
- Amount applied: 0.5 g
- Concentration: Moistened with physiological saline.

Duration of treatment / exposure:

24 h

Observation period:

72 h

Number of animals:

10

Details on study design:

TEST SITE
- Area of exposure: Saddle area
- Type of wrap if used: Occlusive


REMOVAL OF TEST SUBSTANCE
- Washing: Moistened towel
- Time after start of exposure: 24 h


SCORING SYSTEM: Draize

Results and discussion

In vivo

Results

Irritation parameter:

primary dermal irritation index (PDII)

Basis:

mean

Time point:

other: 72 h

Score:

0.1

Max. score:

4

Reversibility:

fully reversible within: 72 h

Irritant / corrosive response data:

No irritancy was observed

Other effects:

No data

Any other information on results incl. tables

Results for skin irritation:

Site	Time	Erythema	Edema
Intact	24 h	0	0
	72 h	0.25	0
Abraded	24 h	0	0
	72 h	0.17	0
Average score	24 h, 72 h	0.105	0

Applicant's summary and conclusion

Interpretation of results:

other: Not classifiable in the EU

Remarks:

Criteria used for interpretation of results: other: Classified in US Toxicity Category IV (slight or no irritation)

Conclusions:

The study was performed according to FIFRA (40 CFR 163). No irritancy was observed and it is therefore not classifiable in the EU.
Classified in US in Toxicity Category IV (slight or no irritation).
Data from other studies confirm the results. Further testing not warranted in the interests of animal welfare.
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.