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Due to the low water solubility of 2-ethylhexyl 3,5,5-trimethylhexanoate (< 1 µg/L at 20 °C) acute toxicity to aquatic organisms is unlikely to occur as outlined in REACH Annex VII and VIII, column 2. A long term daphnia reproduction study was performed instead showing that up to the maximum water solubility (20 µg/L nominal, 8.6 µg/L measured) no mortality or effects on reproduction occurred. Thus, acute toxicity studies using fish or invertebrates are scientifically not required.

2-Ethylhexyl 3,5,5-trimethylhexanoate had no toxic effect on the growth of the algae (average growth rate and yield of Pseudokirchneriella subcapitata) during the test period of 72 hours up to its solubility limit in the test water under the present test conditions. The test was performed at a loading rate of 100 mg/L. In the range finding test, the analytically determined concentrations of 2-ethylhexyl 3,5,5-trimethylhexanoate in the test media (undiluted filtrate = 100 mg/l loading rate) was found to be below the Limit of Quantification of 10 µg/L in this study. Therefore, during the test period of 72 hours in the main test no analytical investigations were possible and not required. The biological results were related to the loading rate of test item concentrations of the test.

The microscopic examination of the algal cells at the end of the test showed no difference between the algae growing at the undiluted filtrate and the algal cells in the control. The shape and size of the algal cells were obviously not affected by the test item up to at least this concentration.

In the toxicity control of the ready biodegradability study with 2-ethylhexyl 3,5,5-trimethylhexanoate, the run of the curve of the oxygen consumption over the 28-day exposure period correlated very well with the oxygen demand of the two added substances, i.e. test item and reference item. Within 14 days of exposure, biodegradation amounted to 37%. Thus, according to the test guidelines, the test item had no inhibitory effect on activated sludge microorganisms at the tested concentration of 100 mg/L because biodegradation in the toxicity control was >25% within 14 days. The IC0 is reported as > 100 mg/l loading rate.

In summary, the 2-ethylhexyl 3,5,5-trimethylhexanoate did not show any aquatic toxicity at its maximum water solubility in all studies performed.