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Short-term toxicity to fish

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Description of key information

Study was conducted according to Regulation (EC) No 440/2008: test method C. 1

Key value for chemical safety assessment

LC50 for freshwater fish:
37.1 mg/L

Additional information

In a 96-h acute toxicity study, rainbow trout (Oncorhynchus mykiss) were exposed to tellurium dioxide at concentrations of 0, 6.25, 12.5, 25.0, 50.0, and 100.0 mg/L nominal under semic-static conditions. Each treatment consisted of seven fish.

Due to the very low water solubility of tellurium dioxide, a Water Accommodated Fraction (WAF) of the test item was applied.

The arithmetic means of measured concentrations were determined to be 0, 3.00, 6.05, 11.5, 24.2 and 46.4 mg tellurium dioxide/L, by ICP-MS.

Neither clinical signs nor mortality could be observed throughout the study.

The 96-h LC50 was:

> 100 mg tellurium dioxide/L (nominal)

> 46.4 mg tellurium dioxide/L (mean measured)

> 37.1 mg tellurium/L (mean measured)

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


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.