Tungsten carbide

Long-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

fish early-life stage toxicity

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

2008-12-30 to 2010-02-12

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

GLP and Guideline study, well documented. 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 lower transformation/dissolution results for tungsten carbide (the target substance) than sodium tungstate (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. In addition, read-across is justified because the classification and labelling is less severe for the target substance and the PBT/vPvB profile is the same. Finally, the dose descriptor for the target substance is expected to be sufficiently lower than the source chemical, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read across approach on Annex 3 of the CSR.

Justification for type of information:

1. HYPOTHESIS FOR THE CATEGORY 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 Carbide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

OECD Guideline 210 (Fish, Early-Life Stage Toxicity Test)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: All concentrations
- Sampling method: The water concentration of the test substance was measured in test solution samples collected prior to initiation (Day –N) and on Days 0, 7, 14, 21, 28, 35, and 38 of the definitive test and used to calculate the concentration of sodium tungstate in the samples. A volume of 10 mL was collected from each control and test substance replicate at each sample point and transferred to a culture tube. Each 10-mL sample was diluted as necessary with 2% HNO3 to provide final sample concentrations within the analytical standard concentration range. The samples were then capped and shaken to mix prior to analysis by ICP-MS.
- Sample storage conditions before analysis: All samples were directly analyzed using a inductively coupled mass spectrometry (ICP-MS).

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Diluter stock solutions were prepared at a target nominal concentration of 975 mg/L. Diluter stock solutions were prepared approximately every two days by adding target weights of 3.9039 g of sodium tungstate to 20-mL glass scintillation vials. The contents of the vials were quantitatively transferred with reagent water into approximately 5.5-L glass carboys containing approximately 3 L of reagent water. The solution was brought to a 4 L volume with additional ABC reagent water. The solutions were vigorously swirled and then sonicated for approximately 10 minutes. The carboy was periodically removed and swirled during sonication until the solution appeared clear and colorless. The FMI, Micro IIpetter, metering pump introduced 40-mL volumes of the diluter stock solution to the diluter system where the solution was diluted with approximately 3,860 mL of dilution water.
- Controls: yes- dlution water
- Evidence of undissolved material (e.g. precipitate, surface film, etc): All test solutions were clear and colorless with no visible particulate material, surface film, undissolved test substance, or precipitate throughout the test.

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

TEST ORGANISM
- Common name: Zebra fish
- Strain: N/A
- Source: In-house culture


METHOD FOR PREPARATION AND COLLECTION OF FERTILIZED EGGS
- Numbers of parental fish (ie of females used to provide required number of eggs): No data
- Method of collection of fertilised eggs: No data
- Subsequent handling of eggs: distributed into egg cups for testing


POST-HATCH FEEDING
- Start date: Test day 4
- Type/source of feed: larval fish food supplement, live rotifers, and live brine shrimp nauplii. Larval food and rotifers to day 16, brine shrimp added on day 7, rotifers discontinued at day 17. Food quantity increased during testing based on fish size.
- Amount given: ad libitum(larval fish food)
- Frequency of feeding: 3 times daily

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

38 d

Remarks on exposure duration:

32 days post-hatch

Post exposure observation period:

none

Hardness:

136-148 mg CaCO3/L

Test temperature:

24.3-25.0 °C

pH:

8.2-8.3

Dissolved oxygen:

6.7-8.2 mg/L (85-104% saturation)

Salinity:

N/A

Nominal and measured concentrations:

Nominal- Control, 0.63, 1.3, 2.5, 5.0, and 10 mg/L.
Mean measured- Control, 0.623, 1.2, 2.58, 4.74, and 9.82 mg/L.

Details on test conditions:

TEST SYSTEM
- Emybro cups (if used, type/material, size, fill volume): glass, 9 cm diameter, Nitex screen bottoms, suspended and oscillated vertically in the aquaria. On day 7, all live fry and unhatched embryos were transferred from the egg cup to a basket made of a Petri dish base with a Nitex screen collar that extended above the water line. Incurrent of test solution was directed into the basket. Fry were left in the basket 6 days, then transferred via pipet to the test chamber.
- Test vessel:
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: 5 L glass aquaria
- Aeration: no
- Type of flow-through (eg peristaltic or proportional diluter): 2 L Mount and Brungs type proportional diluter
- Renewal rate of test solution (frequency/flow rate): 5.3 volume additions/24 hours
- No. of fertilized eggs/embryos per vessel: 20
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per vehicle control (replicates): N/A
- Biomass loading rate: 0.0188 g/L/day


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: blend of naturally hard well water with RO well water
- Total organic carbon: No data
- Particulate matter: No data
- Metals: <0.010 mg/L
- Pesticides: <0.040 mg/L
- Chlorine: No data
- Alkalinity: No data
- Ca/mg ratio: No data
- Conductivity: No data
- Salinity: N/A
- Culture medium different from test medium: no
- Intervals of water quality measurement:


OTHER TEST CONDITIONS
- Adjustment of pH: no data
- Photoperiod: 16-hr light/ 8- hr dark
- Light intensity:471 to 546 lux


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : time to hatch, overall hatching success, post hatch survival, growth


VEHICLE CONTROL PERFORMED: no


RANGE-FINDING STUDY
- Test concentrations: nominal concentrations of 0 (control), 1.0, 2.0, 4.0, 8.0, and 16 mg sodium tungstate/L.
- Results used to determine the conditions for the definitive study: Egg hatchability was 95, 98, 98, 95, 98, and 98% in the 0 (control), 1.0, 2.0, 4.0, 8.0, and 16 mg /L, respectively. Fry mortality at the end of the 21 day exposure was 31, 18, 41, 20, 38, and 7% in the 0 (control), 11.0, 2.0, 4.0, 8.0, and 16 mg/L, respectively.

Reference substance (positive control):

no

Duration:

38 d

Dose descriptor:

NOEC

Effect conc.:

>= 9.8 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Remarks:

sodium tungstate concentration

Basis for effect:

other: hatching success, time to hatch, post hatch survival, growth, mortality, morphology, and behavior

Duration:

38 d

Dose descriptor:

NOEC

Effect conc.:

>= 10 mg/L

Nominal / measured:

nominal

Conc. based on:

other: sodium tungstate (calculated)

Basis for effect:

other: hatching success, time to hatch, post hatch survival, growth, mortality, morphology, and behavior

Remarks on result:

other: The mean calculated concentrations in the test solutions represented recoveries of 92 to 103% of the nominal concentratiions.

Duration:

38 d

Dose descriptor:

LOEC

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

other: sodium tungstate (calculated)

Basis for effect:

other: hatching success, time to hatch, post hatch survival, growth, mortality, morphology, and behavior

Remarks on result:

other: The mean calculated concentrations in the test solutions represented recoveries of 92 to 103% of the nominal concentratiions.

Details on results:

- Mortality/survival at embryo and larval stages: no mortality
- Overall mortality/survival: 88-95% survival in treatments. No statistical difference from control.
- Days to hatch and numbers hatched: 95% hatch by day 6
- Data for length and weight of surviving fish: There was no statistically significant reduction in standard length or mean blotted wet weights observed as compared to the control.
- Type of and number with morphological abnormalities: none by test termination
- Type of and number with behavioural abnormalities: none by test termination
- Other biological observations: none
- Effect concentrations exceeding solubility of substance in test medium: none
- Incidents in the course of the test which might have influenced the results: none

Reported statistics and error estimates:

The NOEC and LOEC for egg hatchability and survival were calculated with Fisher's exact test. The NOEC and LOEC for length and weight were calculated with ANOVA and one-tailed Dunnett's procedure. Shapiro-Wilk's and Levene's tests were used as appropriate. All statistical analyses were performed using SAS software.

Validity criteria fulfilled:

yes

Conclusions:

In a flow-through, early-life stage test using zebrafish and testing sodium tungstate, the NOEC was found to be greater than or equal to the highest concentration tested (≥9.8 mg sodium tungstate/L or approximately 5.74 mg W ion/L). The mean calculated concentrations in the test solutions represented recoveries of 92 to 103% of the nominal concentrations. The MATC could not be calculated due to a lack of statistically significant responses.

Executive summary:

No long-term toxicity to fish data of sufficient quality are available for tungsten carbide (target substance). However, long-term toxicity to fish data are available for sodium tungstate (source substance), which will be used for read-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 on Annex 3 in the CSR.

Description of key information

Tungsten carbide was not tested for chronic toxicity to fish, and read-across to sodium tungstate was used for this endpoint. In a flow-through, early-life stage test using zebrafish and testing sodium tungstate, the NOEC was found to be greater than or equal to the highest concentration tested (≥9.8 mg sodium tungstate/L or approximately 5.74 mg W/L). The mean calculated concentrations in the test solutions represented recoveries of 92 to 103% of the nominal concentrations.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

5.74 mg/L

Additional information

Due to lower transformation/dissolution results for tungsten carbide (the target substance) than sodium tungstate (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. In addition, read-across is justified because the classification and labelling is less severe for the target substance and the PBT/vPvB profile is the same. Finally, the dose descriptor for the target substance is expected to be sufficiently lower than the source chemical, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach or see Annex 3 of the CSR.