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Short-term toxicity to aquatic invertebrates

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Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
2002-09-24 to 2002-10-30
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Well documented, scientifically sound study conducted in accordance with GLP and EU method C.2 (Acute Toxicity for Daphnia) with no deviation to the protocol. The reliability of this study for the substance tested is 1, but in application of read-across to a different substance ECHA’s guidance specifies that the score can be a maximum of 2. On the basis of transformation/dissolution results for tungsten dioxide (the target substance) similar as or lower than sodium tungstate (the source substance), the resulting toxicity potential is also expected to be similar or lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently similar or more conservative for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.
Justification for type of information:
REPORTING FORMAT FOR THE CATEGORY APPROACH
1. HYPOTHESIS FOR THE ANALOGUE APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Tungsten Trioxide
Target: Tungsten Dioxide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 1 in CSR
4. DATA MATRIX: See Annex 1 in CSR
Reason / purpose:
read-across: supporting information
Qualifier:
according to
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Water solubility (under test conditions): < 10 mg/L WO3 at 20 °C (according to the data of the sponsor)

Analytical monitoring:
yes
Details on sampling:
no data
Vehicle:
no
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Water Flea
- Source: Bundesgesundheitsamt Berlin
- Feeding during test: No feeding during exposure.

ACCLIMATION
- Acclimation period: maintained in the facility since more than 15 years
- Acclimation conditions: same as in the test
- Type and amount of food: Unicellular green algae (Desmodesmus subspicatus)
- Feeding frequency: ad libitum
- Health during acclimation: Mortalities of parent Daphnia during the culture period are recorded daily in semi-quantitative way. The neonates are separated from their parent Daphnia by filtration prior to the test.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
48 h
Post exposure observation period:
no data
Hardness:
The total hardness of the dilution water, measured at test start was 15.3 dH (=273.1 mg/L CaCO3).
Test temperature:
Mean test temperature ± 1 °C (in the temperature range 18-22 °C).
pH:
no data
Dissolved oxygen:
no data
Salinity:
n/a
Nominal and measured concentrations:
Nominal concentrations: 5 mg/L (WO3)
Measured (WO3): 0-hr and 48-hr (3.3 mg/L)
Measured (W): 0-hr and 48- hr (2.6 mg/L)
Details on test conditions:
TEST SYSTEM
- Test vessel: Glass beakers
- Material, size, headspace, fill volume: 50 mL
- Aeration: None
- Renewal rate of test solution: None
- No. of organisms per vessel: 10 neonates in 20 mL test medium
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- No. of vessels per vehicle control (replicates): 2
- Biomass loading rate: Direct weighing
- Experimental design: 1 test concentration plus 1 control; no feeding during exposure period; static system

TEST MEDIUM/WATER PARAMETERS
- Source/preparation of dilution water: Reconstituted water prepared according to the recommendations of Bundesgesundheitsamt Berlin. This standard dilution water is used for both the maintenance of the test animals and the preparation of test substance stock and test solutions.

OTHER TEST CONDITIONS
- Photoperiod: 16 hours light, 8 hours dark
- Light intensity: < 1000 lux
Reference substance (positive control):
no
Duration:
24 h
Dose descriptor:
EC0
Effect conc.:
>= 5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
WO3
Basis for effect:
mortality
Duration:
48 h
Dose descriptor:
EC0
Effect conc.:
>= 2.6 mg/L
Nominal / measured:
nominal
Conc. based on:
other: W
Basis for effect:
mortality
Details on results:
The results are expressed in terms of nominal concentrations (at 24 h), and in terms of mean measured concentrations (at 48 h). Measured concentrations correspond to 66 % of nominal (tungsten trioxide - WO3) at 0 hours and at 48 hours.
Results with reference substance (positive control):
n/a
Reported statistics and error estimates:
no data
Conclusions:
The 48-hr acute toxicity of tungsten trioxide (WO3) to Daphnia magna was studied according to OECD Guideline 202 (EU method C.2) under static conditions. Daphnids were exposed to WO3 at a measured concentration of 3.3 mg/L, corresponding to 2.6 mg W/L. Observations were made daily. No mortalities were observed. Thus the 48-hour EC50was > 2.6 mg W/L. The 48-hour NOEC based on mortality can be established at 2.6 mg W/L.
24 hour EC0 ≥ 5 mg/L
48 hour EC0 ≥ 2.6 mg/L (W); = 3.3 mg/L (WO3)
Executive summary:

No short-term toxicity to aquatic invertebrates data of sufficient quality are available for tungsten dioxide (target substance). However, short-term to aquatic invertebrates toxicity to data are available for tungsten trioxide (source substance), which will be used for reading across. Due to similar water solubility and toxicity for the target substance compared to the source substance, the resulting read across from the source substance to the target substance is appropriate. In addition, read across is appropriate because the classification and labelling is similar for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the read-across category approach included in the Category section of this IUCLID submission and/or as an Annex in the CSR.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
2008-10-14 to: 2009-03-13
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Well documented, scientifically sound study that was conducted in accordance with GLP and OECD guideline 202 with no deviation to the protocol. The reliability of this study for the substance tested is 1, but in application of read-across to a different substance ECHA’s guidance specifies that the score can be a maximum of 2. On the basis of transformation/dissolution results for tungsten dioxide (the target substance) similar as or lower than sodium tungstate (the source substance), the resulting toxicity potential is also expected to be similar or lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently similar or more conservative for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.
Justification for type of information:
REPORTING FORMAT FOR THE CATEGORY APPROACH
1. HYPOTHESIS FOR THE ANALOGUE APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Sodium Tungstate
Target: Tungsten Dioxide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 1 in CSR
4. DATA MATRIX: See Annex 1 in CSR
The read across approach is based on the occurrence of a common metal ion or anion, in this case tungstate (see Annex 1 in CSR for read across supporting information).
Reason / purpose:
read-across: supporting information
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
no data
Analytical monitoring:
yes
Details on sampling:
- Concentrations: Control and and each treatment level at 0 and 48 h
- Sampling method: 0.05 mL aliquot of each sample was taken, diluted if necessary with 2 % HNO3, capped and shaken to mix and analyzed by ICP-MS.
- Sample storage conditions before analysis: Room temperature
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances):
- Method: 0.4004 g sodium tungstate dihydrate was dissolved in 2 L aged-blended freshwater. Test concentrations were diluted from this solution.
- Controls: Aged-blended freshwater only.
- Evidence of undissolved material: None
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Water flea
- Source: In-house daphnid culture
- Age at study initiation: < 24 h
- Feeding during test
- Frequency: Not fed during test

ACCLIMATION
- Acclimation period: None necessary, as culture conditions are the same as test conditions
- Type and amount of food: Suspension of Pseudokirchneriella subcapitata, supplemented by artificial diet.
- Feeding frequency: Daily
- Health during acclimation: No mortality in adults at least 48 h prior to testing
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Post exposure observation period:
None
Hardness:
144 mg/L CaCO3
Test temperature:
19.3-19.5 °C
pH:
8.3-8.5
Dissolved oxygen:
7.6-7.9 mg/L (85 to 89 % saturation)
Salinity:
n/a
Nominal and measured concentrations:
Nominal: 0, 13, 25, 50, 100 and 200 mg/L
Mean measured: < MQL, 11.9, 21.5, 41.5, 90.8, and 163 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type: closed
- Material, size, headspace, fill volume: 250 mL glass jars, containing 200 mL test solution, covered with a plastic Petri dish
- Aeration: No
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM/WATER PARAMETERS
- Source/preparation of dilution water: ABC well water mixed with well water demineralized by reverse osmosis, then aged in a tank containing aquaticorganisms. Water was then passed through a sediment filter, a UV sterilizer, and aerated prior to use.
- Metals: B (0.415 mg/L), Ca (83.1 mg/L), Mg (33.1 mg/L), K (7.93 mg/L), Na (32.2 mg/L); all others below DL.
- Pesticides: Below DL
- Alkalinity: 142 mg/L CaCO3
- Conductivity: 347 µS/cm
- Culture medium different from test medium: No
- Intervals of water quality measurement: Daily

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: 16 hr light, 8 hr dark
- Light intensity: 448 lux as measured with a LI-COR Model LI-189 light meter equipped with a photometric sensor.
- The jars were maintained at 20 ± 2 °C in a temperature-controlled water bath.

EFFECT PARAMETERS MEASURED : Immobility and mortality, at 24 and 48 hr.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study
- Test concentrations: 0, 0.10, 1.0, 10, and 100 mg/L
- Results used to determine the conditions for the definitive study: Yes
Reference substance (positive control):
no
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
> 163 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Remarks:
sodium tungstate
Basis for effect:
other: immobilization
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 163 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Remarks:
sodium tungstate
Basis for effect:
other: immobilization
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
90.8 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Remarks:
sodium tungstate
Basis for effect:
other: immobilization
Details on results:
Biological results:
After 48 hours of exposure, immobility was 0, 0, 0, 0, 5 and 15 % in the control and 11.9, 21.5, 41.5, 90.8, and 163 mg/L treatments, respectively. There were no sublethal effects noted in any of the control or test substance treatments. Based on mean measured concentrations, the 48 hour EC50 was > 163 mg /L, the highest concentration tested. Immobility was significantly increased at only the highest test concnetration level. The 48-hour no-observed-effect concentration (NOEC) was determined to be 90.8 mg/L, based on the lack of statistically significant (p=0.05) immobility and sublethal effects at this test substance treatment.
Results with reference substance (positive control):
n/a
Reported statistics and error estimates:
All statistical analyses were performed with SAS software. Estimates of LC50 values and their 95 % confidence limits were calculated using the probit method and trimmed Spearman-Karber method. When the p value for goodness of fit was > 0.05 and there was no other evidence of questionable convergence, the probit method was selected for reporting. When this criterion was not achieved, the trimmed Spearman-Karber method was selected for reporting. The no-observed-effect concentration (NOEC) was determined by using a one-tailed Dunnett’s test.
Conclusions:
The 48hr acute toxicity of sodium tungstate to Daphnia magna was studied according to OECD guideline 202 under static conditions.  Daphnids were exposed to mean measured concentrations of sodium tungstate dihydrate of 0 (control), 11.9, 21.5, 41.5, 90.8, and 163 mg/L. Immobilisation was observed daily.  The 48–hour EC50was > 163 mg sodium tungstate dihydrate/L. The 48-hour NOEC based on immobilization was 90.8 mg sodium tungstate/L. The 48 hour EC50 value was estimated to be >163 mg/L. The 48-hour no-observed-effect concentration (NOEC) was 90.8 mg/L based on the lack ofstatistically significant (p=0.05) immobility and sublethal effects at this and lower test substance treatments.

Executive summary:

No short toxicity to aquatic invertebrates data of sufficient quality are available for tungsten dioxide (target substance). However, short toxicity to aquatic invertebrates data are available for sodium tungstate (source substance), which will be used for reading across. Due to lower water solubility and lower toxicity for the target substance compared to the source substance, the resulting read across from the source substance to the target substance is appropriate as a conservative estimate of potential toxicity for this endpoint. In addition, read across is appropriate because the classification and labelling is more protective for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the read-across category approach included in the Category section of this IUCLID submission and/or as an Annex in the CSR.

Description of key information

The acute toxicity to aquatic invertebrates was tested using sodium tungstate and tungsten trioxide. Hence, for tungsten dioxide this endpoint is derived by read-across from sodium tungstate.  No immobilisation was observed at the saturation concentration of tungsten trioxide in an acute toxicity test; therefore, a definitive EC50 could not be determined and read-across from sodium tungstate is used for this endpoint. In a test on Daphnia employing sodium tungstate as test substance the EC50 was found to be greater than the highest concentration tested (> 163 mg sodium tungstate/L, corresponding to 95.5 mg W/L).

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
95.5 mg/L

Additional information

On the basis of transformation/dissolution results for tungsten dioxide (the target substance) similar as or lower than sodium tungstate (the source substance), the resulting toxicity potential is also expected to be similar or lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently similar or more conservative for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.