Sodium metaborate, anhydrous

Endpoint summary

Description of key information

Acute oral studies have been performed with sodium metaborate (tetrahydrate and dihydrate), disodium tetraborate, sodium tetraborate pentahydrate, sodium tetraborate decahydrate and boric acid. Acute dermal and inhalation studies have been performed with disodium tetraborate pentahydrate, disodium tetraborate decahydrate and boric acid.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

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: Comparable to guideline study with acceptable restrictions.

Qualifier:

according to guideline

Guideline:

other: Regulations to the Federal Hazardous Substances Labelling Act.

Deviations:

not specified

GLP compliance:

no

Remarks:

Substance pre-dates GLP

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Dublin Laboratory Animals.
- Weight at study initiation: 210 to 258 g males
- Fasting period before study: 18 h
- Housing: Housed in groups in ire mesh cages suspended above te droppings.
- Diet: Ad libitum
- Water: Ad libitum

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

No data

Doses:

Actual dose levels of 0.213, 0.459, 0.990, 2.13, 4.59 and 9.90 g/kg of bw.
On a corrected basis these doses are equivalent to 0.215, 1.0, 2.15, 4.64 and 10 g/kg respectively.

No. of animals per sex per dose:

5 males

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Necropsy of survivors performed: Yes
- Other examinations performed: Clinical signs

Statistics:

Statistical analysis of the mortality data was by the moving average method.

Sex:

male

Dose descriptor:

LD50

Effect level:

2.33 other: g/kg

Based on:

test mat.

95% CL:

1.6 - 3.39

Remarks on result:

other: Corrected basis

Mortality:

Deaths occurred at 2.15, 4.64 and 10.0 g/kg dose groups.

Clinical signs:

other: see Remark

Gross pathology:

Gross autopsies performed on the rats which died showed congested lungs, kidneys and adrenals and severe irritation of the gastrointestinal tract. Additional findings noted consistently among the rats at the 10.0 mg/kg dosage level included small haemorrhagic areas present in the mucosal layer of the pyloric portion of the stomach and in the intestinal tract.
Gross autopsies performed on the surviving rats at termination showed all organs to be within normal limits.

Other findings:

The average body weight gain for each group was within the normal range of values for rats of the sex, age and strain used in this study.

Mortality results during the 14-day observation period are presented below. Values are numbers of animals dead/number of animals tested, cumulative.

Dose (g/kg)	Time of death
	Hours				Days
	1	2	4	24	2	3	4	5	6	7
0.215	0/5	0/5	0/5	0/5	0/5	0/5	0/5	0/5	0/5	0/5
0.464	0/5	0/5	0/5	0/5	0/5	0/5	0/5	0/5	0/5	0/5
1.00	0/5	0/5	0/5	0/5	0/5	0/5	0/5	0/5	0/5	0/5
2.15	0/5	0/5	0/5	2/5	2/5	2/5	2/5	2/5	2/5	2/5
4.64	0/5	2/5	2/5	5/5
10.0	0/5	2/5	4/5	5/5

Interpretation of results:

other: EU GHS criteria not met

Conclusions:

The acute oral toxicity of 8 mol sodium metaborate was evaluated in male albino rats in accordance with the technique specified in the Regulations to the Federal Hazardous Substances Labelling Act. The acute oral LD50 was found to be 2.33 g/kg bw with 95 % confidence limits from 1.60 to 3.39 g/kg. On the basis of these result, 8 mol sodium metaborate was classed as toxic by ingestion.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 330 mg/kg bw

Quality of whole database:

High quality (there are a lot of reliable studies for different boron species available).

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: inhalation

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: GLP guideline study

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. 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.

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

no

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

not specified

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Hilltop Lab Animals, Scottdale, PA
- Age at study initiation: Young adult
- Weight at study initiation: Males 245 - 296 g; females 232 - 251 g
- Housing: singly in suspended stainless steel cages with mesh floors which conform to the size recommendations in the Guide for the Care and use of Laboratory Animals DHEW (NIH) No. 86.23. Litter paper was placed beneath the cage and was changed at least 3 times per week.
- Water: Ad libitum by rack-top carboy except during exposure.
- Acclimation period: 22 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 69 - 71 ºF
- Photoperiod (hrs dark / hrs light): 12 h light/dark

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

whole body

Vehicle:

other: no data

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Rectangular whole body perspex chamber operated under slight negative pressure
- Exposure chamber volume: 100 L

TEST ATMOSPHERE
- Particle size distribution: An eight-stage Andersen cascade impactor was used to assess the particle size distribution of the test atmosphere. Samples were withdrawn from the breathing zone of the animals on 2 occassions. The filter paper collection stages were weighed before and after sampling to determine the mass collected at each stage. The aerodynamic mass median diamaeter and geometric standard deviation were determined graphically using two-cycle logarithmic probit axes.

Analytical verification of test atmosphere concentrations:

not specified

Duration of exposure:

4 h

Remarks on duration:

The exposure period was extended to 4 h and 9 min to provide for the chamber to reach equilibrium (T99). The times for 90 and 99 % equilibrium of the chamber atmosphere were 4.6 and 9.1 min respectively.

Concentrations:

Top dose ~ 2 mg/L, to prevent undue discomfort to the animals.

No. of animals per sex per dose:

5/sex/dose

Control animals:

not specified

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Animals were observed for signs of gross toxicity, behavioural changes and mortality to exposure and every 15 min during the first 30 min of exposure. Additional in chamber animal observations were limited due to the accumulation of the test substance on the walls of the exposure chamber. Upon chamber removal, the animals were examined at least once daily for 14 days. Observations included gross evaluation of of skin and fur, eyes and mucous membranes, respiratory, circulatory, autonomic and central nervous systems, somatomotor activity and behaviour pattern. Particular attention was directed to observations of tremors, convulsions, salivation, diarrhoea, sleep and coma.
- Necropsy of survivors performed: yes on all animals. Tissues and organs of the thoracic and abdominal cavities were examined.
- Other examinations performed: Clinical signs, body weight, organ weights and histopathology.

Statistics:

No data

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 2.03 mg/L air

Based on:

test mat.

Exp. duration:

5 h

Mortality:

No deaths occured.

Clinical signs:

other: see other findings

Other findings:

The gravimetric and nominal chamber concentrations were 2.03 and 110.40 mg/L respectively. The mass median aerodynamic diameter was estimated to be 3.7 microns based on graphic analysis of the particle size distribution as measured with an Andersen Cascade Impactor.

Clinical Signs
Animal observations were limited due to the accumulation of test material on the walls of the exposure chamber. During the first 30 minutes of exposure, ocular discharge, hypoactivity and haunched posture were noted. Ocular discharge and or nasal discharge persisted in most animals after removal from the chamber. All animals recovered by day seven.

Pre-test trial

Trial No.	Compressed Air Pressure (psi)	Compressed Air Volume (Lpm)	Room Air Volume (Lpm)	Total Air Volume (Lpm)	Motor Setting	Chamber Conc. (mg/L)	Particle Size Sampled
1^1	27	30	20.4	50.4	6.00	1.94	Yes
2^2	27	30	20.6	50.6	6.00	1.64	No
3^2	27	30	20.5	50.5	6.25	2.00	Yes
4^3	27	30	20.4	50.4	6.00	2.40	No
5^3	27	30	20.3	50.3	5.75	1.98	Yes
6^4	27	30	20.2	50.2	4.50	^5	-
7^4	27	30	20.1	50.1	4.00	^5	-
8^4	27	30	20.2	50.2	4.00	^5	-

¹Test substance used as received, unground

²Test substance used after grinding for 1 h in a ball mill

³Test substance used after grinding for 3 h in a ball mill

⁴Test substance used after grinding for 24 h in a ball mill

⁵Trial terminated due to the malfunction of the dust generator caused by the test substance

Summary of pre-test exposure trials¹

Trial No.	Chamber Concentration (mg/L)	Mass Median Aerodynamic Diameter (microns)^2
1^3	1.94	5.8
3^4	2.00	5.0
5^5	1.98	3.7

¹ See table above for details of generation sysem

² Figure is an estimation based on graphic analysis of the particle size distribution as measured with an Andersen Cascade Impactor

³ Test substance used as received, unground

⁴ Test substance used after grinding for 1 h in a ball mill

⁵ test substance used after grinding for 3 h in a ball mill

Gravimetric chamber concentrations

Sample No.	Mass Collected (mg)	Airflow Sampled (Lpm)	Collection Time (min)	Chamber concentration (mg/L)
1	11.9	4	2	1.49
2	12.1	4	2	1.52
3	11.8	4	2	1.48
4	8.6	4	2	10.8
5^1	24.8	4	2	3.10
6	17.7	4	2	2.21
7	12.8	4	2	1.60
8	17.5	4	2	2.19
9	19.4	4	2	2.40
10	20.4	4	2	2.55
11	20.3	4	2	2.54
12	16.5	4	2	2.06
13	16.1	4	2	2.01
14	17.2	4	2	2.15
Average ± Standard Deviation				2.03 ± 0.54

¹ due to the extremely low chamber concentrations recorded during samples 1 - 4, diluent air being supplied to the chamber was reduced from 30 to 15 Lpm prior ot sample #5.

Particle size distribution

Stage	Effective cutoff diameter (microns)	% of total particles captured (by weight)	Cumulative (%)^1
Sample 1
0	9.0	5.3	94.7
1	5.8	12.9	81.8
2	4.7	10.1	71.7
3	3.3	31.1	40.7
4	2.1	22.7	17.9
5	1.1	13.6	4.3
6	0.7	3.3	1.0
7	0.4	0.8	0.3
F	0.0	0.3	0.0
Sample 2
0	9.0	9.3	90.7
1	5.8	15.9	74.8
2	4.7	11.0	63.8
3	3.3	24.4	39.4
4	2.1	22.2	17.2
5	1.1	13.8	3.4
6	0.7	2.2	1.1
7	0.4	0.7	0.4
F	0.0	0.4	0.0

¹ percent of particles smaller than corresponding effective cutoff

Summary of particle size distribution

Sample No	Sampling time (min)	MMAD (microns)^1	Geometric Standard Deviation
1	4	3.6	1.82
2	4	6.7	1.87

¹This figure is an estimation based on graphic analysis of the particle size distribution as measured with an Andersen Cascade Impactor

Individual bodyweights

Animal No.	Sex	Bodyweight (g)
		Initial	Day7	Day 14
5399	M	296	361	398
5400	M	257	310	343
5401	M	245	307	349
5402	M	260	316	340
5403	M	262	298	322
5404	F	232	250	261
5405	F	237	258	273
5406	F	236	263	289
5407	F	251	275	260
5408	F	234	267	275

Individual cage-side observations

Animal no.	Finding	Day of occurrence
Males
5399	Ocular discharge	CR^1
	Test substance on fur	CR-0 (20.5 h)
	Nasal discharge	CR-6
	Active and healthy	7-14
5400	Nasal discharge, test substance on fur	CR-0 (20.5 h)
	Active and healthy	2 – 14
5401	Test substance on fur	CR
	Nasal discharge	CR-0 (20.5 h)
	Active and healthy	2-14
5402	Ocular discharge, test substance on fur	CR
	Nasal discharge	CR-0 (20.5 h), 4 - 6
	Piloerection	2 – 3
	Active and healthy	7 - 14
5403	Ocular discharge, test substance on fur	CR
	Nasal discharge	CR-0 (20.5 h)
	Active and healthy	2 – 3, 6 – 14
	Ano-genital staining	4 - 5
Females
5404	Nasal discharge, test substance on fur	CR^1-0 (20.5 h)
	Active and healthy	2 - 14
5405	Test substance on fur	CR-0 (20.5 h)
	Nasal discharge	CR-5
	Active and healthy	6 - 14
5406	Ocular discharge, nasal discharge,  test substance on fur	CR
	Active and healthy	0 (20.5 h)-14
5407	Ocular discharge, test substance on fur	CR
	Nasal discharge	CR-0 (20.5)
	Active and healthy	2 – 14
5408	Test substance on fur	CR
	Active and healthy	0 (20.5 h)-14

Individual necropsy observations

Animal No.	Tissue	Findings
Males
53999 - 5403	Lungs	Moderately red^1
Females
5404 - 5408	Lungs	Moderately red^1

¹customarily seen with CO₂ inhlation euthanasia procedure

Interpretation of results:

other: EU GHS criteria not met

Conclusions:

LC50 > 2.03 mg/L
No deaths occurred. Animal observations were limited due to the accumulation of test material on the walls of the exposure chamber. During the first 30 minutes of exposure, ocular discharge, hypoactivity and haunched posture were noted. Ocular discharge and or nasal discharge persisted in most animals after removal from the chamber. All animals recovered by day seven.

Reference 2

Endpoint:

acute toxicity: inhalation

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: Guideline study with acceptable restrictions.

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

yes

Remarks:

The report lacks detail. Since the data is in line with other data on sodium borates, further testing is not warranted in the interests of animal welfare.

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Hilltop Lab Animals, Scottdale, PS.
- Age at study initiation: Young adults
- Weight at study initiation: Males 253- 278 g; females 218-245 g

Route of administration:

inhalation: dust

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

MMAD: 3.1 µm + GSD .971 µm.
Top dose: ~ 2 mg/L was the highest that was obtainable under the conditions of the test.
Analytical concentration: 2040 + 160 mg/m³.

Analytical verification of test atmosphere concentrations:

not specified

Duration of exposure:

4 h

Concentrations:

2040 + 160 mg/m³

No. of animals per sex per dose:

Five/sex/dose.

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days.
- Other examinations performed: Clinical signs, pathology.

Statistics:

No data - Limit test

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 2.04 mg/L air (nominal)

Exp. duration:

4 h

Remarks on result:

other: No lethal effect at limit dose.

Mortality:

None

Clinical signs:

other: see other findings

Body weight:

No data

Gross pathology:

No specific findings.

Other findings:

Animal observations were limited due to the accumulation of test material on the walls of the exposure chamber. During the first hour of exposure, ocular discharge, hypoactivity and haunched posture were noted. Ocular discharge and a few animals exhibited nasal discharge and/or hunched position. All animals recovered by day six after removal from chamber.

Interpretation of results:

other: EU GHS criteria not met

Conclusions:

Acute inhalation toxicity limit on disodium tetraborate pentahydrate gave a LC50 > 2.04 mg/L (2g/m3).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LC50

Value:

2 030 mg/m³ air

Quality of whole database:

High quality (there are a lot of reliable studies for different boron species available).

Acute toxicity: via dermal route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

No data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Meets generally accepted scientific standards with acceptable restrictions.

Qualifier:

according to guideline

Guideline:

other: This study was carried out to comply with US EPA-FIFRA guidelines at the time and carried out by the US Food and Drug Laboratories to GLP.

Deviations:

not specified

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: LaCrosse Industries Inc., Schenectady , New York.
- Weight at study initiation: Males: 2.19 +/- 0.27kg; females: 2.29 +/- 0.28kg

Type of coverage:

occlusive

Vehicle:

not specified

Details on dermal exposure:

TEST SITE
- Area of exposure: Area not specified. The back of each rabbit was clipped free of fur prior to treatment.
- Type of wrap if used: Not specified


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


TEST MATERIAL
- Amount applied: Dosage to 2 g/kg bw

Duration of exposure:

24 h

Doses:

Dosage to 2 g/kg bw

No. of animals per sex per dose:

Five/sex/dose

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Other examinations performed: Clinical signs, pathlogy

Statistics:

Not relevant – Limit test.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Mortality:

None

Clinical signs:

other: Clinical changes included anorexia and decreased activity in four rabbits, diarrhoea and soft stools in 3 rabbits and nasal discharge in three rabbits.

Gross pathology:

The only finding in one rabbit was abdominal cavity filled with fluid.

Other findings:

No data

Interpretation of results:

other: EU GHS criteria not met

Conclusions:

Acute dermal limit study carried out to comply with US EPA-FIFRA guidelines at the time and carried out by the US Food and Drug Laboratories to GLP. The LD50 was > 2000 mg/kg bw indicating no acute dermal toxicity.

Reference 2

Endpoint:

acute toxicity: dermal

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: Guideline study

Qualifier:

according to guideline

Guideline:

other: FIFRA (40 CFR 163)

Deviations:

no

GLP compliance:

no

Remarks:

Study pre-dates GLP

Test type:

fixed dose procedure

Limit test:

yes

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Details on test animals or test system and environmental conditions:

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

Type of coverage:

semiocclusive

Vehicle:

physiological saline

Details on dermal exposure:

TEST SITE
- Area of exposure: The skin of all animals was abraded longitudinally every 2 - 3 cm, deep enough to penetrate the stratum corneum, but not cause bleeding.
- % coverage: > 10 % of body surface implied
- Type of wrap if used: Semi occlusive


REMOVAL OF TEST SUBSTANCE
- Washing (if done): Moist towel
- Time after start of exposure: 24 h


TEST MATERIAL
- For solids, paste formed: Yes


VEHICLE
- Amount applied: Substance moistened with 1.5 mL saline

Duration of exposure:

24 h

Doses:

Dosage to 2 g/kg

No. of animals per sex per dose:

5/sex/group

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Necropsy of survivors performed: Yes
- Other examinations performed: Clinical signs, histopathology

Statistics:

Not applicable - limit test.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

No deaths occurred

Clinical signs:

other: Clinical changes were limited to transient diarrhoea in 2 rabbits and some incidences of erythema (9), and oedema (30), atonia (2), desquamation (4), necrosis, and other evidence of irritation at 23 and ~70.5 h after treatment.

Gross pathology:

No gross necrospy findings were observed. Observations included one animal with gas filled intestine, one animal with pale yellow-coloured kidneys and 5 animals with enlarged or swollen fallopian tubes.

Other findings:

No data

Gross necropsy findings in male and female rabbits at the end of the observation period:

Gross Necropsy Findings	Dosage at 2 g/kg
Number of animals necropsied	10
No gross necropsy findings	5
Intestine
Gas-filled	1
Kidneys
Pale yellow coloured	1
Fallopian tubes
Enlarged or swollen	4
Pale	1
External
Diarrhoea stains	1

Interpretation of results:

other: EU GHS criteria not met

Conclusions:

The study was performed according to FIFRA (40 CFR 163). The LD50 > 2000 mg/kg bw indicating no acute dermal toxicity. No deaths occurred. Clinical changes were limited to erythema, oedema, atonia, desquamation, necrosis and some incidences of skin irritation at more than 24 h of treatment.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Quality of whole database:

High quality (there are a lot of reliable studies for different boron species available).

Additional information

LD50 values of >2000 mg/kg was recorded for the oral route for sodium metaborate and for the dermal routes for sodium tetraborate pentahydrate, disodium tetraborate decahydrate and boric acid. An LD50 value > 2 mg/L was recorded for the acute inhalation study with disodium tetraborate decahydrate, disodium tetraborate pentahydrate and boric acid. The inhalation figure represents the highest attainable concentration.

Two acute oral toxicity studies were conduced on sodium metaborate dihydrate in rats. The mortality results from the two studies gave a non-monotonic response, 0/5 male rats died at 1600 mg/kg, 2/5 died at 2000 mg/kg and 1/5 died at 2500 mg/kg. Probit analysis produced a LD50 value of 3251 mg/kg, however the value lay outside the range of experimental doses. Using the dose interval of 1.25, the next higher dose level would expected to be 3125 mg/kg, assuming that one rat would die, the LD50 could be computed to be 7660 mg/kg assuming that complete mortality at 3125 mg/kg the value obtained by extrapolation is 2436 mg/kg. Therefore the acute median lethal oral dose of sodium metaborate dihydrate falls in the range of 2.4 to > 7.5 g/kg (Denton 1995, 1996).

Sodium metaborate is of low acute toxicity. Although some of the acute oral studies were not of modern standards and were performed prior to the introduction of GLP, they are reproducible across a number of studies and species and of acceptable quality. For acute dermal and acute inhalation some studies do meet the modern GLP standard.

The following acute oral data were obtained:

Sodium metaborate (tetrahydrate): 2330 mg (183 mg B)/kg

The following acute inhalation data were obtained:

No acute inhalation studies of sodium metaborates have been conducted. Studies were conducted on analogue substances

Disodium Tetraborate Pentahydrate: >2040 mg (302 mg B) /m³

Disodium Tetraborate Decahydrate: >2030 mg (300 mg B) /m³

Boric acid: > 2000 mg (349 mg B) /m³

The following acute dermal data were obtained:

No acute dermal studies of sodium metaborates have been conducted. Studies were conducted on analogue substances

Disodium Tetraborate Pentahydrate: >2000 mg/kg bw (296 mg B/kg)

Disodium Tetraborate Decahydrate: >2000 mg/kg bw (226 mg B/kg)

Boric acid: >2000 mg (349 mg B) /kg bw

 

Therefore, a low acute toxicity is concluded for Sodium metaborate. Please also refer to the read-across statement attached to section 13.

Justification for classification or non-classification

No classification according to Regulation (EC) No 1272/2008 is required for sodium metaborate regarding acute toxicity as all results (LD50 values) for the oral toxicity as well as for the inhalation and dermal toxicity of the analogues substances exceeded the limit for classification.

Please also refer to the read-across statement attached to section 13.