CTO

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:

August 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

exposure-related information

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

2004

Deviations:

yes

Remarks:

One deviation reported. Considered uncritical.

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Version / remarks:

2008

Deviations:

yes

Remarks:

One deviation reported. Considered uncritical

Qualifier:

according to guideline

Guideline:

other: OECD Guidance Document 23 (Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures)

Version / remarks:

2000

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch No.: B0345
Purity: >99%
Homogeneity: Homogeneous

Analytical monitoring:

yes

Details on sampling:

- Concentrations: calibration was performed in the range of 10 – 2000 µg/L Tungsten (W) and 0.5 – 10 mg/L Cesium (Cs) in Daphnia test medium

Vehicle:

no

Details on test solutions:

The water-accommodated fraction was prepared for the test. This was done by weighing the nominal load 100.0 mg/L adding the corresponding amount of dilution water and shaking vigorously for 24 hours. The resulting solution was filtrated through 0.45 µm Nylon filters.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Strain/clone: Straus, Berlin strain
- Source: LAUS GmbH
- Feeding during test: No
- Food type: green algae (Desmodesmus subspicatus)

ACCLIMATION
- Acclimation period: 18.5 hours before the start of the test, the adult animals were separated from the young. 0.5 hours before test start, the adults were caught with the help of a glass tube, and the newborn Daphnia, aged between 0 and 18 hours, were sieved from the medium and immediately placed into a beaker containing dilution water.
- Health during acclimation (any mortality observed): After the settling-in period, animals which showed no apparent damage were used for the test.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Remarks on exposure duration:

Observation times: 24 and 48 hours

Hardness:

250 CaCO3/L

Test temperature:

21.5 – 22.2 °C

pH:

7.6-7.8

Dissolved oxygen:

8.7-8.9 mg/L

Nominal and measured concentrations:

Nominal: 100 mg/L
Geometric Mean of calculated concentrations (test item); based on W-determination: 5.30 mg/L
At both test times (t= 0h, 48h) the measured concentrations of Cs were below the LOQ (2.537 mg/L).

Details on test conditions:

TEST SYSTEM
- Test vessel: glass beakers, nominal volume 50 mL, tall shape
- No. of organisms per vessel: 5 daphnia
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Biomass loading rate: each vessel containing 20 ± 5 mL test solution (or control) and 5 daphnia

Reference substance (positive control):

yes

Remarks:

Potassium dichromate (CASRN 7778-50-9)

Duration:

24 h

Dose descriptor:

EC50

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.:

> 5.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element (total fraction)

Remarks:

The test item consists of 66.68% Tungsten (W)

Basis for effect:

mobility

Remarks on result:

other: based on W-determination

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:

EC50

Effect conc.:

> 5.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element (total fraction)

Remarks:

The test item consists of 66.68% Tungsten (W)

Basis for effect:

mobility

Remarks on result:

other: based on W-determination

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 5.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element (total fraction)

Remarks:

The test item consists of 66.68% Tungsten (W)

Basis for effect:

mobility

Remarks on result:

other: based on W-determination

Duration:

48 h

Dose descriptor:

LOEC

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

LOEC

Effect conc.:

> 5.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element (total fraction)

Remarks:

The test item consists of 66.68% Tungsten (W)

Basis for effect:

mobility

Remarks on result:

other: based on W-determination

Details on results:

At the start and at the end of the test, the content of Cesium (Cs) and Tungsten (W) in the test solutions was determined using an ICP-OES-method. The concentration of the dissolved test item was calculated from the measured concentrations of these values and the total formula (Cs0.33WO3) provided by the sponsor. The test item consists of 15.92% Cs and 66.68% W.

The solubility behaviour of the both metals were observed to be different. At both test times (t= 0h, 48h) the measured concentrations of Cs were below the LOQ (2.537 mg/L). This is due to the fact that the Cs measurement is generally very inaccurate and fluctuating.

The test item concentration was calculated from the measured concentrations of W. Because of the poor solubility, the calculated concentration was 5 % of the nominal concentrations at the beginning and the end of the test. Since the values deviate more than ± 20 % of the nominal values, the geometric mean was calculated.

The biological results were therefore based on the values determined via W determination and compared additionally to the nominal values.

Results with reference substance (positive control):

- Results with reference substance valid? Yes

Reported statistics and error estimates:

Since no toxicity occurred no statistical evaluation was conducted and biological results are given as a range.

No observations were made which might cause doubts concerning the validity of the study outcome. All validity criteria were met. The result of the test is considered valid.

One deviation from the study plan and the guideline was noted. The temperature for the study ranged from 21.5 to 22.2 °C and was therefore 0.2°C higher than stated in the guideline and in the study plan.This deviation was considered uncritical.

 

An additional deviation from the study plan was mentioned. Although the recovery rate for Cs determination differs by more than +15%, no recalibration was performed. The Cs determination is generally very inaccurate and fluctuating. In addition, at the end of the test, even if the QC was taken into account, the value would be lower than LOQ. Therefore, this deviation was classified as uncritical.

Validity criteria fulfilled:

yes

Conclusions:

One valid experiment was performed. The 48-hr EC50 > 100 mg/L, based on nominal values. The 48-hr EC50 > 5.30 mg/L, based on tungsten (W) determinations.

Executive summary:

One valid experiment was performed. The study was performed as a limit test using a concentration at 100 mg/L (nominal). For each test concentration and the blank control, 20 Daphnia were exposed to the test item for 48 hours in a static test system. After 24 and 48 hours, the immobilised Daphnia were counted. No toxicity was observed in the treatment and none of the animals were immobilised in the blank control. Thus, the 48-hr EC50 > 100 mg/L, based on nominal values. The 48-hr EC50 > 5.30 mg/L, based on tungsten (W) determinations.

The results do not meet the CLP classification for aquatic toxicity. This conclusion is based on the nominal loading rate of the test item (100 mg/L) reported in the study. According to Annex IV of ECHA's CLP guidance version 5.0, it is the loading level which yields the level of metal ion equivalent to the available LC50 or NOEC/EC10 that can then be used to determine the acute or long-term hazard category appropriate for classification. For this daphnid study, the 48-hr EC50 reported was >100 mg/L (nominal) which is greater than the CLP cut-off limit (100 mg/L) for both the acute and chronic aquatic hazard classifications.

In addition, a full transformation/dissolution (T/D) study was conducted for the test item, Cesium Tungsten Oxide, under separate cover (Study No. 17100406G989). From that 7-day study, a concentration of 0.307 mg/L W was measured from a 1 mg/L (nominal) loading rate. The Cs values lay above the LOQ in flasks 9 – 11 on days 4 and 7 only, therefore the determination of kinetic was not possible for Cs. According to Annex IV of ECHA's CLP Guidance (ver. 5.0), if the concentration at 1 mg/L loading rate is less than or equal to the acute ecological reference value (EC50) of the dissolved metal ion form, then the substance is not classified for acute hazard. Given that the measured concentration of W (0.307 mg/L) was less than its corresponding 48-hr EC50 (growth rate) measured value of >5.3 mg/L, this would further support the conclusion that this test item does not meet the Regulation (EC) 1272/2008 as amended criteria as Hazardous To The Aquatic Environment.

Description of key information

One valid experiment was performed. The study was performed as a limit test using a concentration at 100 mg/L (nominal). For each test concentration and the blank control, 20 Daphnia were exposed to the test item for 48 hours in a static test system. After 24 and 48 hours, the immobilised Daphnia were counted. No toxicity was observed in the treatment and none of the animals were immobilised in the blank control. Thus, the 48-hr EC50 > 100 mg/L, based on nominal values. The 48-hr EC50 > 5.30 mg/L, based on tungsten (W) determinations.

The results do not meet the CLP classification for aquatic toxicity. This conclusion is based on the nominal loading rate of the test item (100 mg/L) reported in the study. According to Annex IV of ECHA's CLP guidance version 5.0, it is the loading level which yields the level of metal ion equivalent to the available LC50 or NOEC/EC10 that can then be used to determine the acute or long-term hazard category appropriate for classification. For this daphnid study, the 48-hr EC50 reported was >100 mg/L (nominal) which is greater than the CLP cut-off limit (100 mg/L) for both the acute and chronic aquatic hazard classifications.

In addition, a full transformation/dissolution (T/D) study was conducted for the test item, Cesium Tungsten Oxide, under separate cover (Study No. 17100406G989). From that 7-day study, a concentration of 0.307 mg/L W was measured from a 1 mg/L (nominal) loading rate. The Cs values lay above the LOQ in flasks 9 – 11 on days 4 and 7 only, therefore the determination of kinetic was not possible for Cs. According to Annex IV of ECHA's CLP Guidance (ver. 5.0), if the concentration at 1 mg/L loading rate is less than or equal to the acute ecological reference value (EC50) of the dissolved metal ion form, then the substance is not classified for acute hazard. Given that the measured concentration of W (0.307 mg/L) was less than its corresponding 48-hr EC50 (growth rate) measured value of >5.3 mg/L, this would further support the conclusion that this test item does not meet the Regulation (EC) 1272/2008 as amended criteria as Hazardous To The Aquatic Environment.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

100 mg/L