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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Description of key information

Study was conducted according to OECD guideline 202, data are reliable without restrictions. 

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
5.79 mg/L

Additional information

The effect of tellurium dioxide on the acute immobilisation of Daphnia magna was investigated. The test item media was prepared from a WAF with the nominal loading of 100 mg tellurium dioxide/l that was diluted to form the remaining concentrations of 50.0, 25.0, 12.5, and 6.25 mg/L. Samples were taken for chemical analysis from fresh and aged media at test start and end, respectively.

At 24 hours , an immobilisation effect of 70% in the highest test concentration was observed . After 48 hours, further concentration dependent effects of tellurium dioxide were apparent. Immobilisation was statistically significant in the three highest test concentrations at 80, 100 , and 100%, respectively . The NOEC is 4.55 mg Te02/L (3.64 mg Te/L). The EC50 is 7.24 mg Te02/L (5.79 mg Te/L).

The test fulfilled the validity criteria.

Conclusion

The EC50 for immobilisation of Daphnia magna by tellurium dioxide is 7.24 mg/L.

The EC50 for immobilisation of Daphnia magna by tellurium is 5.79 mg/L .

Justification for read-across:

This read-across is based on the hypothesis that source and target substances do possess similar ecotoxicological properties.

Since the physico-chemical behaviour of elemental Tellurium and Tellurium dioxide is the same with regard to their metabolic fate (reduction to the Telluride cation) there seems to be good evidence that Tellurium from different moieties will behave very similar with regard to systemic toxicity.

Elemental Tellurium and Tellurium dioxide are relatively poorly water soluble and their systemic uptake by environmental organisms will be directly comparable.

Thus the bioavailability will be an important factor for assessment of ecotoxicity of both substances. The water solubility of both substances is relatively low, with 1.7 and 2.5 mg/L for Tellurium and Tellurium dioxide, respectively.

Data from transformation dissolution tests at different pH values and loadings are available for both substances, indicating Tellurium dioxide to be more soluble at pH 8.

 

Corresponding standard information requirement

Source substance

Tellurium dioxide

Target substance

Tellurium

Water solubility

Transformation dissolution test: OECD guideline 29

 

Target pH 8 at 21.5 °C.

Loadings TeO2: Te concentrations after 7 days:

1 mg/L: 698.9 µg/L

10 mg/L: 6.254 mg/L

100 mg/L: 30.72 mg/L

Transformation dissolution test: OECD guideline 29

 

Target pH 8 at 21.5 °C.

Loadings: Te concentrations after 7 days:

1 mg/L: 20.02 µg/L

10 mg/L: 183.3 µg/L

100 mg/L:1.762 mg/L.

Water solubility:

OECD guideline 105

 

2.5 mg/L at 23 °C

pH 6.4

Water solubility:

OECD guideline 105

 

1.7 mg/L at 20 °C

pH 5.5 – 6.3

 

Underlying the basic assumption that effects caused by the bioavailable metal fraction and the same toxicokinetic behaviour (outlined in detail in the chapter toxicokinetic), ecotoxicity data from the relatively higher soluble Tellurium dioxide were considered appropriate for the ecotoxicity assessment of Tellurium.

In conclusion read-across is considered an appropriate adaptation for ecotoxicological endpoints to meet the standard information requirements according to REACH Regulation.

A detailed justification for read-across describing the toxicokinetic profile, comparing physico-chemical and toxicological properties as well as classification and labelling is outlined in IUCLID chapter 13 in a separate paper.