Registration Dossier

Diss Factsheets

Administrative data

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:
no hazard identified

Marine water

Hazard assessment conclusion:
no hazard identified

STP

Hazard assessment conclusion:
no hazard identified

Sediment (freshwater)

Hazard assessment conclusion:
no hazard identified

Sediment (marine water)

Hazard assessment conclusion:
no hazard identified

Hazard for air

Air

Hazard assessment conclusion:
no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:
no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:
no potential for bioaccumulation

Additional information

Conclusion on classification

Aquatic toxicity classification of inorganic metals and metal compounds is conducted by comparing transformation/dissolution (T/D) data for the substance, generated using the standard protocol (UN GHS, 2007 Annex 10) [see Table 3 in Section 1.3 for results] with toxicity data for the most soluble metal substance as described in the CLP technical guidance (section IV. 5 Application of classification criteria to metals and metal compounds) (EU, 2008). In the case of tungsten carbide (WC), T/D data for WC are compared to the aquatic toxicity reference values derived from read across to sodium tungstate. The T/D data is ideally tested at the pH at which the highest dissolution is expected, within the range defined by the test protocol (pH 5.5-8.5). Inorganic W substances have been demonstrated to have a higher T/D rate at pH 8.5 than pH 6. Tungsten carbide was tested at pH 6 and pH 8.5 for 24 hours, but only pH 6 for the full test transformation/dissolution test (7 and 28-day testing) (CANMET-MMSL, 2010). In order to conservatively estimate the 7 and 28-day WC dissolution at pH 8.5, a factor of 10 was applied to the pH 6 values. This factor is based on the difference between pH 6 and 8.5 results in the 24-hour, 7-day, and 28-day tests for W metal powder, which has a similar solubility as WC and was tested at both pHs for tests. For tungsten metal, the pH 8.5 dissolution was a maximum of 5.5 times higher than pH 6 dissolution, so the applied factor of 10 is supported as a conservative factor to be used for extrapolation from pH 6 to pH 8.5 dissolution for tungsten carbide. Therefore, the T/D values with the applied factor of 10 were compared to the corresponding acute (31000 μg W/L, based on the ErC50) and chronic (3380 μg W/L, based on the ErC10) aquatic toxicity reference values derived from sodium tungstate testing of algae, as the most sensitive aquatic species. The results of this comparison demonstrate that tungsten carbide does not classify for aquatic toxicity. 

 

The dissolution of tungsten from tungsten carbide of 1% obtained from transformation/dissolution studies was used to estimate the equivalent tungsten concentration contributed from tungsten carbide and to determine if a PNEC needs to be estimated. A PNEC was developed when the tungsten equivalent dose was lower than the recommended limit dose (on a tungsten basis) of the respective study. 

 

The details of how this classification is derived are described in Table 7.12 below.

 

Table 7.12. Classification of tungsten carbide using T/D data comparison to toxicity data according to CLP

 

Test type/ duration

T/D loading amount as WC (mg/L)

T/D results (μg W/L) with applied factor of 10 for conversion from pH 6 to pH 8

Toxicity reference value*

(μg W/L)

Comparison of T/D and toxicity values (μg W/L)

Aquatic toxicity classification result

Screening test/ 24 hour

100

1037**

Acute= 31000

1037<31000

Refer to full T/D test for classification

Acute full test/ 7 days

1

97

Acute= 31000

97<31000

No Acute 1 classification

Acute full test/ 7 days

10

1190

Acute= 31000

1190<31000

No Acute 2 classification

Acute full test/ 7 days

100

8770

Acute= 31000

8770<31000

No Acute 3 classification

Chronic full test/ 28 days

1

230

Chronic=3380

230<3380

No Chronic 4 classification

CLASSIFICATION CONCLUSION

No aquatic toxicity classification

 

 

 

 * Reference values were derived from algae as the most sensitive species, with the acute value being the EC50 for growth and the chronic value being the ErC10. 

 

 ** This test was performed at pH 8.5 so the conversion factor of 10 was not applied. 

 

Categories Display