Dierbium trioxide

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:

7 August 2012 - 9 October 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted to GLP in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Water samples were taken from the control and the 100 % v/v saturated solution test group (replicates R1 - R4 pooled) at 0 and 48 hours for quantitative analysis. Samples were stored at approximately -20 °C prior to analysis.
Duplicate samples were taken and stored at approximately -20 °C for further analysis if necessary.

Vehicle:

no

Details on test solutions:

Due to the poor solubility of the test material, a modification of the standard method for the preparation of aqueous media was performed, exposing organisms to a saturated solution.
550 mg of test material was added to 11 litres of reconstituted water and stirred using a propeller stirrer at approximately 1500 rpm for 24 hours. After stirring, any undissolved test material was removed by filtration through a 0.2 µm Gelman Acrocap filter (initial 500 mL discarded) to give a 100 % v/v saturated solution.
50 mg/L was shown to be a high enough concentration to create an excess of the test material in the saturated solution.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
The test was carried out using 1st instar Daphnia magna derived from in-house laboratory cultures.
Adult Daphnia were maintained in 150 mL glass beakers containing Elendt M7 medium in a temperature controlled room at approximately 20 °C. The lighting cycle was controlled to give a cycle consisting of 16 hours light and 8 hours darkness with 20 minute dawn and dusk transition periods. Each culture was fed daily with a mixture of algal suspension (Desmodesmus subspicatus) and flake food suspension.
Culture conditions ensured that reproduction was by parthenogenesis. Gravid adults were isolated the day before initiation of the test, such that the young daphnids produced overnight were less than 24 hours old. These young were removed from the cultures and used for testing. The young used for testing were progeny of second brood or later. The diet and diluent water are considered not to contain any contaminant that would affect the integrity or outcome of the study.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

Approximate theoretical total hardness of 250 mg/L as CaCO3

Test temperature:

20 - 21 °C

pH:

7.8 - 8.1

Dissolved oxygen:

8.5 - 9.1 mg O2/L

Nominal and measured concentrations:

Nominal concentration: 100 % v/v saturated solution.
Measured concentration 0.241 - 0.277 mg test material/L

Details on test conditions:

EXPERIMENTAL PREPARATION
The test material was dispersed in reconstituted water. This was prepared by adding 25 mL of the following stock solutions to each litre (final volume) of deionised water with a conductivity of <5 µS cm^-1.
The stock solutions were CaCl2.2H2O (11.76 g/L); MgSO4.7H2O (4.93 g/L); NaHCO3 (2.59 g/L) and KCl (0.23 g/L).
The reconstituted water had a pH of 7.8 ± 0.2 adjusted (if necessary) with NaOH or HCl and was aerated until the dissolved oxygen concentration was approximately air-saturation value.

EXPOSURE CONDITIONS
250 mL glass jars containing approximately 200 mL of test preparation were used. At the start of the test 5 daphnids were placed in each test and control vessel at random, in the test preparations. Four replicate test and control vessels were prepared. The test vessels were then covered to reduce evaporation and maintained in a temperature controlled room at approximately 21 °C with a photoperiod of 16 hours light and 8 hours darkness with 20 minute dawn and dusk transition periods with a light intensity ranging from 631 to 642 lux. The daphnids were not individually identified, received no food during exposure and the test vessels were not aerated.
The control group was maintained under identical conditions but not exposed to the test material.

The test preparations were not renewed during the exposure period. Any immobilisation or adverse reactions to exposure were recorded at 24 and 48 hours after the start of exposure. The criterion of effect used was that Daphnia were considered to be immobilised if they were unable to swim for approximately 15 seconds after gentle agitation.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 other: % v/v saturated solution

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 other: % v/v saturated solution

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

DEFINITIVE TEST
There was no significant immobilisation in the daphnids; two immobilised daphnids were observed in one replicate of the 100% v/v saturated solution test group, however these are considered to be due to natural causes as no more than 10 % immobilisation occurred.

- Observations on Test Material Solubility
Throughout the test, the test preparations were observed to be clear colourless solutions.

- Physico-Chemical Measurements
Temperature was maintained at approximately 21 °C throughout the test and there were no treatment related differences for oxygen concentration or pH.

- Verification of Test Concentrations
Analysis of the test preparations at 0 and 48 hours showed measured test concentrations to range from 0.242 to 0.211 mg/L as erbium (equivalent to 0.277 and 0.241 mg/L test material) and so it was considered justifiable to estimate the EC50 values in terms of the nominal test concentrations only.

Differences in measured concentrations were observed between the range finding and the definitive test. Examination of the data could show no cause for these differences; however, it was considered to have had no adverse effect on the outcome of the test as no test material-related immobilisation was observed at the highest concentration.

Results with reference substance (positive control):

The reference material was potassium dichromate at concentrations of 0.32, 0.56, 1.0, 1.8 and 3.2 mg/L.
Analysis of the immobilisation data by the geometric mean method at 24 hours and the trimmed Spearman-Karber method (Hamilton et al 1977) at 48 hours based on the nominal test concentrations gave the following results:
24 h EC50 0.75 mg/L (95 % confidence limits 0.56 - 1.0 mg/L)
48 h EC50 0.45 mg/L (95 % confidence limits 0.42 - 0.48 mg/L)

The No Observed Effect Concentrations after 24 and 48 hours were 0.56 and 0.32 mg/L respectively (based upon zero immobilisation).

Table 1 Cumulative Immobilisation Data in the Definitive Test

Nominal Concentration (% v/v Saturated Solution)		Cumulative Immobilised Daphnia (Initial Population: 5 Per Replicate)
		24 Hours			48 Hours
		No. Per Replicate	Total	%	No. Per Replicate	Total	%
Control	R1	0	0	0	0	0	0
	R2	0			0
	R3	0			0
	R4	0			0
100	R1	0	0	0	0	2	10
	R2	0			2*
	R3	0			0
	R4	0			0

R1 - R4 = Replicates 1 to 4

*Immobilisation of Daphnia considered to be due to natural causes as only 10 % immobilisation occurred.

Validity criteria fulfilled:

yes

Conclusions:

The 48 hour EC50 based on nominal test concentrations was greater than 100 % v/v saturated solution. The No Observed Effect Concentration was ≥100 % v/v saturated solution.

Executive summary:

The acute toxicity potential of the test material to Daphnia magna was assessed in a study conducted in accordance with the standardised guidelines OECD 202 and EU Method C.2.

In a limit test, twenty daphnids (4 replicates of 5 animals) were exposed to an aqueous solution of the test material at a concentration of 100 % v/v saturated solution for 48 hours at a temperature of approximately 21 °C under static test conditions. Immobilisation and any adverse reactions to exposure were recorded after 24 and 48 hours.

The study showed that there were no toxic effects at saturation as no immobilisation was seen.

Therefore the 48 hour EC50 based on nominal test concentrations was greater than 100 % v/v saturated solution. The No Observed Effect Concentration was ≥100 % v/v saturated solution.

Description of key information

The 48 hour EC50 based on nominal test concentrations was greater than 100 % v/v saturated solution. The No Observed Effect Concentration was ≥100 % v/v saturated solution.

Additional information

The acute toxicity of the test material to Daphnia magna was assessed in a study conducted in accordance with the standardised guidelines OECD 202 and EU Method C.2 under GLP conditions. It was assigned a reliability score of 1 in accordance with the criteria set forth in Klimisch (1997).

In a limit test, twenty daphnids (4 replicates of 5 animals) were exposed to an aqueous solution of the test material at a concentration of 100 % v/v saturated solution for 48 hours at a temperature of approximately 21 °C under static test conditions. Immobilisation and any adverse reactions to exposure were recorded after 24 and 48 hours.

The study showed that there were no toxic effects at saturation as no immobilisation was seen.

Therefore the 48 hour EC50 based on nominal test concentrations was greater than 100 % v/v saturated solution. The No Observed Effect Concentration was ≥100 % v/v saturated solution.