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Fish:

The acute toxicity studies on fish indicate that rainbow trout is more sensitive towards the chemical in comparison to fathead minnow. The EC50 values for Pimephalis promelas were above the highest nominal test concentration in both cases >1000 mg/L (and thus far above the solubility of the test substance), while the EC50 value for Salmo gairdneri was determined at 27 mg/L. Additionally, there is a long-term fish on fish larvae (Pimephales promelas) is available. Three endpoints were evaluated: embryo survival at hatch, growth (weight and length after 30d) and larval survival (for 30 d) of which survival of the larvae was the most sensitive endpoint displayed (NOEC = 37 µg/l). These results indicate that there is a large difference between the acute and chronic toxicity towards this substance for fish.

Invertebrates:

The acute toxicity assays on invertebrates indicate that the crustaceans are more or less equally sensitive, while the insecta are clearly less sensitive. Additionally, the test results indicate that there is a clear difference in toxicity depending on the composition of the chemical. Comparing the toxicity of the individual terphenyls, p-terphenyl is not toxic in the tested range (EC50 48h > 5500µg/L), while the other two (ortho and para) 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. 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.

These short-term toxicity results could be compared to the results from a long-term toxicity in Daphnia magna (Therminol 75). The assessed endpoints were survival and reproducation after 21 days of exposure. The NOECs for those endpoints were 0.007 and 0.0048 mg/L respectively. These results indicate that the difference in toxicity between the acute and chronic toxicity tests is not that different for invertebrates such as Daphnia magna.

Algae:

Several tests describing the toxicity towards algae are available and all indicate that the substance is rather toxic towards algae. The two studies which are most recently performed (Santowax R) tested up to 24.8 µg/l test substance. No effects on growth rate were seen at this test concentration, thus the NOEC based on growth rate (72h) was above 24.8 µg/l in one of the tests, the NOEC for biomass in the other test was however 3.22 µg/l (72h). The other tests on Therminol 88 and Therminol 75 reported effect levels in the same range of toxicity, the endpoint however was not growth rate but biomass (and reported 96h instead of 72h) and therfore preference is given to the two studies on Santowax R. In this study the lowest NOEC value of 3.22 µg/l was reported.  

Conclusion:

Based on the acute toxicity data, fish are clearly the least sensitive organisms, invertebrates and algae appear to be in the same toxicity range. The long-term toxicity data however indicate that the substance displays toxicity towards all organims. Although there is a certain decrease in toxicity going from fish to invertebrates and then algae shown by their respective NOECs of 37, 4.8 and 3.22 µg/L.