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In a guideline algal growth inhibition study, the substance tungstosilicic acid was found to have a 72hr EC50 value of 14mg/L based on growth rate. Results were based on the geometric mean of the measured concentrations at the beginning and end of the study due to apparent and early loss of material potentially due to complexation with the salts of the test medium. At concentrations above 35mg/L, no intact cells were seen at the end of the study.

In a guideline study, daphnia magna were exposed to tungstosilicic acid for a period of 48hrs. An EC50 value of 120mg/L was established.

In a limit test, a nominal concentration of 20mg/L (determined as the EC50 in algae) of tungstosilicic acid at the start of the study had no adverse effects on rainbow trout during the 96 hours of the study. The measured analytical concentrations were found to decline substantially over the course of the study such that the geometric mean concentration was calculated at 5.8mg/L. Due to the differences in test media between this study and the Algal Growth Inhibition test performed on this test item (see chapter 6.1.3) the geometric mean measured test concentration of 5.8 mg/L obtained in dechlorinated tap water was considered to be equivalent to a concentration of 20 mg/L in algal culture medium. This study therefore showed that rainbow trout were not any more sensitive to the test item than algae.

In a guideline study to assess the toxicity to activated sludge, the EC50 value was in excess of the maximum tested concentration of 1000mg/L. The EC10 value was in the range 10 -100mg/L, which suggests that the dose response curve that is quite shallow and that the EC10 figure should be used as a conservative basis for establishing the PNEC.