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Short-term toxicity to aquatic invertebrates

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Description of key information

Conclusions are based on read-across from analogue substances of a known category. Acute toxicity to aquatic invertebrates (Daphnia) (EL50) for 2,2-bis[[(2-ethyl-1-oxohexyl)oxy]methyl]propane-1,3-diyl bis(2-ethylhexanoate)(EC# 230-743-8) is expected to be >100 mg/l, i.e. >> water solubility.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
100 mg/L

Additional information

Read across to structural analogue. All members of this category of esters have a hydrophobic nature. Based on structural similarities of the substance of interest and the members of the category it was concluded that it was justified to applyread across for this endpoint.

 

Acute Toxicity Study in Daphnia magna with HATCOL 3331.

All solutions at loading rates of 1.0 mg/l and higher were prepared separately. These supersaturated solutions were magnetically stirred for two days to ensure maximum solubility in test medium. The resulting solution was colourless, but contained a floating layer and test substance particles. Collection of the water phase by siphoning or centrifugation was not an option considering the specific gravity of the test substance. After the stirring period the mixture was therefore filtered through a paper filter (ca. >5 μm). The filtrate was clear and colourless.

 The project was started with a limit test, exposing daphnia to a filtrate (ca. >5 μm) prepared at a loading rate of 100 mg/l and a blank-control. The test was performed in duplicate with 5 daphnids per vessel and samples for analysis were taken at the start and the end of the test.

The analytical results showed that the average exposure concentration was higher than the solubility limit of HATCOL 3331 (i.e. <0.2 mg/l). At the end of the test, 45% of the daphnids exposed to the filtrate were immobilized. Since concentrations were all below 1.0 mg/l, a final test was performed using a range of concentrations nominally spaced by a factor of 10.

A final test was performed exposing daphnia to filtrates (ca. >5 μm) prepared at loading rates of 1.0, 10 and 100 mg/l and a 10-foid dilution of the filtrate at 1.0 mg/l. Samples for analysis taken at the start and the end of the test showed that the average exposure concentration in the 1.0 mg/l filtrate approximated the water solubility (i.e. <0.2 mg/l), while average exposure concentrations in the 10 and 100 mg/l filtrates were maintained above the water solubility of HATCOL 3331.

HATCOL 3331 did not induce acute immobilisation of Daphnia magna at the concentration obtained in a filtered solution prepared at a loading rate of 100 mg/l, corresponding to an average exposure concentration above the water solubility, i.e. 1.1-1.4 mg/l after 48 hours of exposure (NOEC). Also, no immobilisation was observed at concentrations approximating the water solubility.

In conclusion: Due to the very low solubility of HATCOL 3331 in water, concentration levels that might be toxic for daphnia could not be reached. Therefore, the 48h-EC50 exceeded the maximum solubility of HATCOL 3331 in test medium.