Dilithium tetraborate

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Samples for possible analysis were taken from the test concentration and the control

Frequency at t=0 h and t=96 h
Volume 4.8 mL from the approximate centre of the test vessels.
Storage Samples were stored in a freezer (=-15°C) until analysis at the analytical laboratory of the Test Facility.

Additionally, reserve samples of 4.8 mL were taken from all test solutions for possible analysis. If not used, these samples were stored in a freezer (=-15°C) for a maximum of three months after delivery of the draft report, pending on the decision of the sponsor for additional analysis.

Vehicle:

no

Details on test solutions:

The item was completely soluble in test medium at the concentrations tested therefore no correction was made for the purity/composition of the test item. Test solutions were prepared starting with the highest concentration of 100 mg/L. A one-day period of magnetic stirring was applied to accelerate dissolution of the test item in medium. The pH of the stock solution used for the limit test was adjusted with 1 M HCL (Merck, Darmstadt, Germany) from 9.2 to 8.9. Lower test concentrations were prepared by subsequent dilutions of the highest concentration in test medium. All test solutions were clear and colorless at the end of the preparation procedure.

Test organisms (species):

Cyprinus carpio

Details on test organisms:

Species Carp (Cyprinus carpio, Teleostei, Cyprinidae) Linnaeus, 1758
Source Zodiac, proefacc, "De Haar Vissen", Wageningen University and Research Centre, The Netherlands.
Mean length Range-finding test: 3.0 ± 0.3 cm
Limit test: 2.8 ± 0.3 cm
Mean weight Range-finding test: 0.40 ± 0.09 g
Limit test: 0.30 ± 0.14 g
Characteristics F1 from a single parent-pair bred in UV-treated water.
Reason for selection This system has been selected as an internationally accepted species.
Total fish used 26

The fish were held in quarantine for at least 12 days after delivery. In the holding tank, the adjusted ISO medium, formulated using RO-water (tap-water purified by reverse osmosis; GEON Waterbehandeling, Berkel-Enschot, The Netherlands) had the following composition:
CaCl2.2H2O 211.5 mg/L
MgSO4.7H2O 88.8 mg/L
NaHCO3 46.7 mg/L
KCl 4.2 mg/L

The fish were fed daily with pelleted fish food (Essence (300-500 um), Coppens International bv, Helmond, The Netherlands).

For batch to be valid, mortality during the seven days prior to the start of the test had to be less than 5%.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Hardness:

Not stated

Test temperature:

temperature 20-24°C, constant within 2°C

pH:

The pH was 8.6 and 9.0 for the concentrations of 10 and 100 mg/L in the range-finding test, respectively, and 8.9 in the limit test.

Dissolved oxygen:

oxygen > 60% of air saturation

Salinity:

Not stated

Conductivity:

Not stated

Nominal and measured concentrations:

Samples taken from the limit concentration were analysed. The actual concentrations were at the level of 96-98% of nominal during the exposure period. Based on these results, the effect parameters were expressed in terms of analytically confirmed nominal concentrations.

Details on test conditions:

TEST SYSTEM
Test vessels: 6.5 litres, all-glass, containing 5 litres of test solution
Test medium: Adjusted ISO medium with a hardness of 180 mg CaCO3 per litre and a pH of 7.7 ± 0.3.
Number of fish: 7 each in the control and the limit concentration
Loading: 0.42 g fish/Litre, i.e. 7 fish per 5 litres of test medium
Illumination: 16 hours photoperiod daily
Aeration: Aeration was introduced after 56 hours of exposure.
Feeding: No feeding from 24 hours prior to the test and during the total test period
Introduction of fish: Within 7 minutes after preparation of the test media from a holding tank with comparable water quality parameters and pH and temperature differences between test and holding tank media of less than 0.5 unit and 1.0°C.


TEST MEDIUM / WATER PARAMETERS
Adjusted ISO medium, formulated using RO-water (tap-water purified by reverse osmosis; GEON Waterbehandeling, Berkel-Enschot, The Netherlands) with the following composition:
CaCl2.2H2O 211.5 mg/L
MgSO4.7H2O 88.8 mg/L
NaHCO3 46.7 mg/L
KCl 4.2 mg/L


TEST CONCENTRATIONS
- In the range-finding test, three fish per concentration were exposed to a range of 0.10 to 100 mg/L increasing by a factor of 10.
- In the limit test, the test concentration used was 100 mg/L.

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:

RANGE-FINDING TEST
No mortality or clinical effects were observed at any of the test concentrations during the test period. In the two highest concentrations precipitate was observed from the 24 hour of exposure.

Samples taken from nominal 100 mg/L were analysed. The initial concentration measured was 101 mg/L. This concentration remained stable during the test period (98% of initial). Therefore, the expected LC50 was above the nominal concentration of 100 mg/L.

LIMIT TEST
At the start of the limit test, analysis of the highest concentration solution was measured to be 98 mg/L. After 96 hours of exposure, the test item concentration was still the same at 98 mg/L. Based on this analysis, the effect parameters can be expressed in terms of analytically confirmed nominal concentrations.

As in the range-finding test, no mortality or other clinical effects were observed in both the control and the limit concentration throughout the test duration.

The 96h-LC50 for Cyprinus carpio exposed to dilithium tetraborate therefore exceeded the analytically confirmed nominal concentration of 100 mg/L.

Sublethal observations / clinical signs:

Table 1: Incidence of Mortality and Total Mortality During the Range-Finding Test

Dilithium Tetraborate Nominal concentration (mg/L)	Initial number of fish	Cumulative mortality					Total Mortality (%)
		2h	24h	48h	72h	96h
0.10	3	0	0	0	0	0	0
1.0	3	0	0	0	0	0	0
10	3	0	0	0	0	0	0
100	3	0	0	0	0	0	0

Table 2: Incidence of Mortality and Total Mortality During the Limit Test

Dilithium Tetraborate Nominal concentration (mg/L)	Initial Number of fish	Cumulative mortality					Total Mortality (%)
		2½h	24h	48h	72h	96h
Control	7	0	0	0	0	0	0
100	7	0	0	0	0	0	0

Validity criteria fulfilled:

yes

Conclusions:

In conclusion, the 96h-LC50 for Cyprinus carpio exposed to dilithium tetraborate exceeded the analytically confirmed nominal concentration of 100 mg/L.

Executive summary:

The objective of the study was to evaluate dilithium tetraborate for its ability to generate acute toxic effects in Cyprinus carpio during an exposure period of 96 hours and, if possible, to determine the LC₅₀at all observation times. The study was conducted according to OECD guideline No. 203, 1992.

A limit test was performed based on the results of a preceding range-finding test. Seven fish per group were exposed to an untreated control and to a limit concentration of nominal 100 mg/L. The total exposure period was 96 hours and samples for analytical confirmation of exposure concentrations were taken at the start and at the end of the test.

The 96h-LC50 for Cyprinus carpio exposed to dilithium tetraborate exceeded the analytically confirmed nominal concentration of 100 mg/L.

Samples taken from the limit concentration were analysed. The actual concentrations were at the level of 96-98% of nominal during the exposure period. Based on these results, the effect parameters were expressed in terms of analytically confirmed nominal concentrations. 

No mortality or other clinical effects were observed in this study.

The study met the acceptability criteria prescribed by the study plan and was considered valid.

In conclusion,the 96h-LC₅₀for Cyprinus carpio exposed to Dilithium tetraborate >100 mg/L.

Description of key information

A limit test was performed based on the results of a preceding range-finding test. Seven fish per group were exposed to an untreated control and to a limit concentration of nominal 100 mg/L. The total exposure period was 96 hours and samples for analytical confirmation of exposure concentrations were taken at the start and at the end of the test.

Samples taken from the limit concentration were analysed. The actual concentrations were at the level of 96-98% of nominal during the exposure period. Based on these results, the effect parameters were expressed in terms of analytically confirmed nominal concentrations. 

No mortality or other clinical effects were observed in this study.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

100 mg/L