Boron carbide

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

May 31–June 11, 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Principles of Good Laboratory Practice (GLP), (Chemikaliengesetz, attachment 1, Federal Republic of Germany). The OECD Principles of Good Laboratory Practice.

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

Test Medium
The test medium was water composed of dechlorinated drinking water and deionised water.

Test ltem Solutions
100 mg Boron Carbide was weighed on weighing scoops and transferred to a volumetric flask. 1 L test medium was added up to the mark and the solution was stirred for 48 hours. Afterwards the insoluble particles of the test item were separated from the liquid phase by filtration through a filter with 0.45 µm mean pore size. Defined volumes of the prepared solution were transferred to each glass beaker to get the assigned nominal test concentrations for the test vessels. The test solution volume was 50 mL per test vessel.

Test organisms (species):

Daphnia magna

Details on test organisms:

As test organism, Daphnia magna Straus, Clone V, was used. The animals are continuously bred in the laboratory and were originally purchased in a healthy condition from the Umweltbundesamt in Berlin, Germany. Daphnia magna was bred as single culture (one daphnid per 100 mL) in water composed of dechlorinated drinking water and deionised water. The pH-value of the aerated water was within a range of 6.0–9.0. The dissolved oxygen was above 60 % saturation and the total hardness 140–268 mg/L (as CaCO3), corresponding to 7.8–14 °dH. About 20 adults were kept in 1 L. The animals were fed on single cell green algae (Desmodesmus subspicatus, formerly Scenedesmus subspicatus) at least three times a week. The daphnids were reared at a temperature of 20 ± 2 °C in a climatic chamber with 16 h of illumination and 8 h of darkness. The medium was changed three times per week. A pipette was used to separate the young daphnids from the adults. Freshly hatched daphnids of an age between 6–24 hours were used for the test.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

9 °dH (160.63 mg/L as CaCO3).

Test temperature:

21.4 ± 0.3 °C

pH:

8.4 ± 0.03

Dissolved oxygen:

99.3 ± 0.8 % O2 saturation

Nominal and measured concentrations:

100 mg/L nominal concentration

Details on test conditions:

Test procedure: static test
Duration: 48 hours
Temperature: 20.9–21.7 °C
Oxygen concentration: > 99 % of air saturation (approx. 9.9 mgO2/L)
pH-value: 8.41–8.47
Lighting: approx. 707 lux
Exposure to light: 16 hours photoperiod daily
Feeding: none
Test vessels: four 100 mL glass beakers per concentration, each filled with 50 mL
Loading: 10 mL for each animal
Aeration: none
Number of animals: 20 per concentration in 4 replicates of 5 animals
Nominal concentration of positive control: 1 and 2 mg/L

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

24 h

Dose descriptor:

EC0

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC0

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC100

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

24 h

Dose descriptor:

EC100

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Results with reference substance (positive control):

- Results with reference substance valid? yes
- EC50 (48h) > 1 mg/l < 2 mg/l

Reported statistics and error estimates:

Due to Limit test statistics not relevant

Validity criteria fulfilled:

yes

Remarks:

In the control not more than 10 % of animals were immobilised, the dissolved oxygen concentration was > 30 % of saturation at test temperature.

Conclusions:

The EC50 (48 h) of the test item was determined to be > 100 mg/L nominal). The corresponding EC0 (48 h) was 100 mg/L (nominal).

Executive summary:

The toxicity of Boron Carbide on Daphnia magna was tested in a 48-hour acute immobilisation test. The test was performed according to OECD guideline 202. Test species was Daphnia magna Straus, Clone V, age between 6 and 24 hours. 20 organisms per test concentration (4 replicates of 5 animals each) were used. The duration of the test was 48 hours. The test item was tested in a static test at a nominal concentration of 100 mg/L. Test solution was prepared by stirring 100 mg test item (Boron Carbide B4C, technical grade powder, purity 97 % w/w) per litre water for 48 hours to achieve a saturated concentration. The insoluble particles of the test item were separated from the liquid phase by filtration through a filter with 0.45 µm mean pore size. Endpoints reported are the EC50, EC100 and the EC0 after 24 and 48 hours. Temperature, pH-value and oxygen concentration [% saturation] of the test solutions measured after 0, 24 and 48 hours are reported. Hardness of the test water was measured on the day of application. A negative control using untreated water has been conducted under the same test conditions. The test was performed within the water solubility limit of the test item. Since no immobilisation occurred during the test the estimation of the EC50 value did not require statistical methods. The total hardness (as CaCO3) of the untreated control was determined to be 9 °dH; the mean pH-value of the untreated control was determined to be 8.44 ± 0.03 (SD), the mean temperature was 21.4 ± 0.3 °C (SD) and the mean oxygen saturation was 99 ± 0.9 % (SD). The EC50 (48 h) of the test item was determined to be > 100 mg/L (nominal). The corresponding EC0 (48 h) was 100 mg/L (nominal).

Description of key information

The short term toxicity to aquatic invertebrates has been determined in a 48-h acute immobilisation test on Daphnia magna (OECD 202). As the test substance boron carbide shows very low water solubility of < 1 mg/L, the extracts of a nominal concentration of 100 mg/L have been chosen as test medium in a limit test. No effects were observed at 100 mg/L (nominal).