Tungsten oxide

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

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

Adequacy of study:

key study

Study period:

2002-07-01 to: 2002-07-12

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 with GLP and generally accepted guidelines. 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 oxide (the target substance) than tungsten trioxide (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 on Annex 3 in 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: Tungsten trioxide
Target: Tungsten oxide
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:

other: Commission Directive 88/302/EEC

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

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:

no

Details on sampling:

no data

Vehicle:

no

Details on test solutions:

The test substance was added to about 130 mL of deionized water and stirred overnight before testing (equilibration phase)

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

no data

Test type:

not specified

Water media type:

not specified

Limit test:

no

Total exposure duration:

3 h

Remarks on exposure duration:

permanent aeration

Post exposure observation period:

no data

Hardness:

no data

Test temperature:

20+2 °C

pH:

pH of the suspension before application : 6.1
pH of the various test substance concentratoins: 7.2 - 7.4

Dissolved oxygen:

no data

Salinity:

N/A

Nominal and measured concentrations:

Nominal test concentrations (mg/L): 1000, 1800, 3200, 5600, 10000

Details on test conditions:

TEST SYSTEM
- Test vessel: aeration tank of waste water treatment plant treating predominately domestic sewage (Wupper area water authority)
- Test concentration of the activated sludge : 480 mg/L suspended solids

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol (purity of 97%)

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 10 000 mg/L

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

- Tungsten trioxide showed 3.1 % respiration inhibition of activated sludge at a test substance concentration of 10,000 mg/L.

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: EC50 = 6.1 mg/L

Reported statistics and error estimates:

- The EC values were determined by statistical methods (probit analysis)

Test concentration: 1000 mg/L - Inhibition: 0.0% Test Concentration: 1800 mg/L - Inhibition: 15.4% Test Concentration: 3200 mg/L - Inhibition: 7.7% Test Concentration: 5600 mg/L - Inhibition: 7.7% Test Concentration: 10000 mg/L - Inhibition: 3.1% Physical-Chemical oxygen consumption was 0 mg/L-h for all test concentrations. The Respiratory rate-phsical-chemical oxygen consumption ranged from 22.0 mg/L-h to 27.0 mg/L-h

Validity criteria fulfilled:

yes

Conclusions:

Tungsten trioxide showed 3.1% respiration inhibition of activated sludge at the test substance concentration of 10,000 mg/L. The EC50 was > 10,000 mg/L

Executive summary:

No microorganism toxicity data of sufficient quality are available for tungsten oxide (target substance). However, microorganism toxicity data are available for tungsten trioxide (source substance), which are 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 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 description in the Category section of this IUCLID submission or Annex 3 of the CSR.

Description of key information

Tungsten oxide was not tested for toxicity to aquatic micro-organisms, and read-across to tungsten trioxide was used for this endpoint. An EC50 of >10,000 mg/L was found in a 3-hr activated sludge respiration inhibition test conducted with tungsten trioxide.

Key value for chemical safety assessment

EC50 for microorganisms:

10 000 mg/L

Additional information

Due to similar or lower transformation/dissolution results for tungsten oxide (the target substance) than tungsten trioxide (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 substance is adequately protective. For more details, refer to the read-across category approach description in the Category section of this IUCLID submission or Annex 3 of the CSR.