Boron carbide

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

09 MAR 2010 - 21 APR 2010

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.1 (Acute Toxicity for Fish)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

GLP according to German Chemikaliengesetz and directive 2004/9/EC

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Same substance as used for phys. chem. testing

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

Test solution was prepared by stirring 100 mg test item per litre water under aeration for 48 hours to achieve a saturated concentration. The insoluble particles of the test item were separated from the liquid phase by filtration with 1 bar through a filter with 0.45 pm mean pore size.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

Species: Oncorhynchus mykiss (Walbaum)

Size: 4-6cm

Producer: Fischzucht Wagenhausen, D-88348 Bad Saulgau/Wagenhausen, Germany

Acclimatisation:
Fish for the main test were obtained from the supplier on the 29/12/2009 (acclimatisation > 12 days) and held under testing conditions in 300 l containers with continuous renewal of water (5 - 10 % per day) and permanent aeration of water. The fish were held under identical conditions for the entire pre-experimental period. 24h before initiation of the test feeding was stopped.

Holding water:
Water composed of dechlorinated drinking water and deionised water. The pH value of the aerated water was between 6.0 and 8.5. The dissolved oxygen was above 60 % saturation and the total hardness was between 140 - 250 mg/L (as CaCO3), corresponding to 7.8 - 14°dH.

Light:
12 to 16 hours photoperiod daily.

Temperature:
The water temperature was 15 to 17 °C.

Oxygen:
The concentration of oxygen was controlled 3 times a week. The air saturation value was not below 60 %.

Feeding:
The fish were fed each day with granular rearing food (size 0) with approx. 2 % of their body-weight. The food was obtained from the fish supplier.

Mortality:
Following a 48-hour settling-in period, mortality was recorded. No mortality above 5 % was observed throughout the acclimatisation period.

Test type:

static

Water media type:

freshwater

Total exposure duration:

96 h

Hardness:

11° dH

Test temperature:

15.7-16.6°C

pH:

8.08-8.25

Dissolved oxygen:

>87° of air saturation

Nominal and measured concentrations:

The nominal concentration was 100mg/l, no effective concentration has been determined due to insolubility of boron carbide

Details on test conditions:

The test medium: Water composed of dechlorinated drinking water and deionised water with a conductivity of 461 µS/cm.
Exposure to light: 16 hours daily.
Feeding: No feeding of fish during the test.
Test vessels: 25 L stainless steel tanks, filled with 10 L.
Loading: Max. loading of 1 g fish/L.
Aeration: Continuous aeration of the test tanks with a membrane pump using a Pasteur pipette.
Number of animals: 7 per concentration, no replicates.
Test condition control: Measurements of temperature, pH-value and dissolved oxygen concentration were performed in 24 h intervals from the test solutions. Water hardness of the untreated control was determined at the beginning of the test.

EFFECT PARAMETERS MEASURED:
Fish were observed at 3, 6, 24, 48, 72 and 96 hours after test start.

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

No clinical signs have been observed (see table 1). No fish died during the test. (see table 2).

Reported statistics and error estimates:

Since no mortality occurred during the test the estimation of the LC50 value did not require the evaluation with statistical methods.

Sublethal observations / clinical signs:

Table 1: Observation of clinical signs of fish during the test 

Test item conc. [mg/l]	Control					100
Time [h]	0	°	*	#	+	0	°	*	#	+
0	7				0	7				0
3	7				0	7				0
6	7				0	7				0
24	7				0	7				0
48	7				0	7				0
72	7				0	7				0
96	7				0	7				0

0 :      no clinical signs

o :      Unusual behaviour (reduced activity and or orientation to bottom or surface of the test vessels, dark pigmentation)

* :      difficulties with maintenance of equilibrium

#:       fish upside down with loss of equilibrium,showing only movement of gills

           as a sign of life

+:        no sign of life

 

 

Table 2  % mortality of fish in the test

 

	control	Nominal concentration of  Boron Carbide B4C 100 mg/L
Time [h]	Mortality [%]
3	0	0
6	0	0
24	0	0
48	0	0
72	0	0
96	0	0

 

 

 

Validity criteria fulfilled:

yes

Remarks:

The mortality in the control did not exceed one fish at the end of the test. The dissolved oxygen concentration was at least 60 % of the air saturation value throughout the test.

Conclusions:

According to the results of the test, the LC50 (96 h) of the test item was determined to be > 100 mg/L. The LC0 (96 h) and the NOEC (96 h) were observed at > 100 mg/L.

Executive summary:

The aim of the study was the assessment of the LC50 (96 h) of the test item in fish within the framework of laws for registration according to OECD 203 and EC method C.1 (92/69/EEC). Test species was Oncorhynchus mykiss (Walbaum), size between 4 and 6 cm. Seven organisms per test concentration were used. The duration of the test was 96 hours. The test item was tested in a static test at a concentration of 100 mg/L. Test solution was prepared by stirring 100 mg test item (Boron Carbide B4C, technical grade powder, purity 97 wt%) 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. Temperature, pH-value and % oxygen saturation of the test solutions have been measured after 0, 24, 48, 72 and 96 hours, and comply with OECD 203. .Assessments on effects and mortality after 3, 6, 24, 48, 72 and 96 hours were conducted. A negative control using untreated water has been conducted with the same test conditions. No visible abnormalities as: loss of equilibrium, swimming behaviour, respiratory function, pigmentation and other events could be observed. No body weight No intercurrent deaths could be observed. The LC50 (96 h) of the test item was determined to be > 100 mg/L. The LC0 (96 h) and the NOEC (96 h) were observed at >= 100 mg/L.

Description of key information

The short term toxicity to fish was determined in a 96-h acute limit test on Oncorhynchus mykiss (OECD 203). 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).