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Short-term toxicity to aquatic invertebrates

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Reference
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:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Well documented, scientifically sound study that was conducted in accordance to GLP and OECD guideline 202 with no deviation to the protocol. The reliability of this study for the substance tested is a K1, but in application of read-across to a different substance ECHA’s guidance specifies that the score can be a maximum of K2. Due to similar or lower transformation/dissolution results for tungsten blue oxide (the target substance) than sodium tungstate (the source substance), the resulting toxicity potential would also be expected to be similar or lower, so read-across is appropriate. In addition, read-across is justified because the classification and labeling is the same or less severe for the target substance PBT/vPvB profile is the same. Finally, the dose descriptors are, or are expected to be, sufficiently similar or higher 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 blue oxide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 1 in CSR
4. DATA MATRIX: See Annex 1 in CSR
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: 10 mL from each control and treatment at 0 and 48 h and transferred to a culture tube.
- 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 (e.g. precipitate, surface film, etc): 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 (mean and range, SD): <24h
- 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, suplemented by artificial diet.
- Feeding frequency: Daily
- Health during acclimation (any mortality observed): 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 degrees C
pH:
8.3-8.5 SU
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 Calculated- < MQL, 11.9, 21.5, 41.5, 90.8, and 163 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: Glass 250 mL 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 uS
- Culture medium different from test medium: No
- Intervals of water quality measurement: Daily

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: 16 hr light, 8hr 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 degrees C in a temperature-controlled water bath.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Immobility and mortality, 24 hr.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2x
- 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
Key result
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
> 163 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
other: sodium tungstate concentration
Basis for effect:
other: immobilization
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 163 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
other: sodium tungstate concentration
Basis for effect:
other: immobilization
Key result
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
90.8 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
other: sodium tungstate concentration
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 163 mg /L, the highest level 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 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 aquatic invertebrate short-term toxicity data of sufficient quality are available for tungsten oxide (target substance). However, aquatic invertebrate short-term toxicity 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 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

No data were available for tungsten blue oxide for invertebrate toxicity; therefore, read-across to sodium tungstate was used for this endpoint. In a test using Daphnia and testing sodium tungstate the EC50 observed was found to be greater than the highest concentration tested (>163 mg sodium tungstate/L or approximately 96 mg W/L).

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
96 mg/L

Additional information

Due to similar or lower transformation/dissolution results for tungsten blue oxide (the target substance) than sodium tungstate (the source substance), the resulting toxicity potential would also be expected to be similar or lower, so read-across is appropriate. In addition, read-across is justified because the classification and labelling is the same or less severe for the target substance, and the PBT/vPvB profile is the same. Finally, the dose descriptors are, or are expected to be, sufficiently similar or higher 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.