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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Study was conducted according to OECD guideline 201, data are reliable without restrictions. 

Key value for chemical safety assessment

EC50/LC50 for freshwater algae:
11.7 mg/L

Additional information

The toxicity of Tellurium dioxide on the growth of the uni-cellular fresh water green alga Pseudokirchneriella subcapitata was tested in a study according to OECD guideline 201.

Alga were exposed to various dilutions of a water accommodated fraction of the test item (WAF) obtained with a loading rate of 100 mg/L.

For the relevant measurement parameter growth rate, a slight inhibition of 18.5 % was observed at the highest test concentration. There was a concentration-dependent effect on the cell number increase (yield) of P. subcapitata starting at the second highest concentration of 4.17 mg TeO2/L.

Growth rate:

EC50: > 14.7 mg tellurium dioxide/L (> 11.7 mg tellurium /L)

NOEC: 4.17 mg tellurium dioxide/L (3.34 mg tellurium/L)  

Yield:

EC50: 10.3mg tellurium dioxide/L (8.19 mg tellurium/L)

EC10: 3.40 mg tellurium dioxide/L (2.72 mg tellurium/L)

NOEC: 1.42 mg tellurium dioxide/L (1.13 mg tellurium/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.