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Short-term toxicity to aquatic invertebrates

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Description of key information

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
22 µg/L

Marine water invertebrates

Marine water invertebrates
Effect concentration:
28 µg/L

Additional information

In total 6 study reports describing the acute toxic effects of terphenyl mixtures and the individual terphenyls on Daphnia magna are available. In all cases, a solvent was used to increase the water solubility of the test substances (5/6 tests used DMF, 1/6 used acetone) and results are expressed as nominal concentrations. No measurements are available for any of the tests. First of all, from the results it is clear that the toxicity to Daphnia magna for the individual terphenyls is very different; p-terphenyl is not toxic in the tested range (EC50 48h > 5500µg/L), while the other two are toxic in the low µg-range (EC50 48h of 45 and 22 µg/L for the ortho- and meta-isomer respectively). This difference is most probably caused by the difference in water solubility between the different isomers, with the p-isomer having the lowest water solubility. This also suggests that the toxicity of the terphenyl mixtures can be very different according to the composition of the multi-constituent, the higher the amount of ortho- and meta-terphenyl, the higher the expected toxicity.

The results gathered in the tests performed with the mixtures of terphenyls are consequently also not surprising (since the para-isomer concentration is only minor in comparison to the concentrations of the other constituents). The lowest EC50 48h value was reported with MCS-1980 (EC50 48h of 7µg/L). This was however not confirmed by a second test on MCF-1980 -new in which an EC50 48h value in the range of the o-terphenyl was found (EC50 48h of 43µg/L). A test performed with Therminol 88, suggested a lower toxicity than predicted by the isomer toxicity (EC50 48h of 270 µg/L), which is substantially above the water solubility of the substance.

Furthermore, some results on other invertebrate organisms than Daphnia magna are available: Mysidopsys bahia, Gammarus fasciatus and Paratanytarsus parthenogenica. These were all performed with Therminol 75 as test substance. In general these were all in range of the results gathered with Daphnia, except for the EC50 determined for the insect species which was much higher than the values for the crustacean species.

 

As interspecies differences and differences in toxicity according to composition are prominent as a worst case the study on the effect of m-terphenyl to Daphnia is chosen as a key study (EC50 = 22 µg/l). The lowest value was found for MCS-1980, but this was not confirmed by a second test on MCF1980new.