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EC number: 485-270-1
CAS number: -
Verification of Test ConcentrationsThe test item is a complex mixture from the reaction of 3-octanoylthiopropyltriethoxysilane, 3-mercaptopropyltriethoxysilane and 2-methyl-1,3-propanediol and was known to rapidly hydrolyze. Despite extensive analytical investigations using both GC-MS and LC-MS/MS methods, it was not possible to develop a method of analysis which could accurately quantify the concentration of the hydrolysis product formed. Furthermore, it was considered likely that the hydrolysis product itself was also unstable.The test item was known to contain 6.01% silicon and, as such, the determination of concentrations of silicon in test media was considered a suitable alternative to compound specific analytical determinations. In an attempt to minimize the background count of silicon due to the use of standard laboratory glassware, all equipment used for the biological phase of the definitive test was a plastic alternative.Chemical analysis of the control and all loading rate WAF preparations on Days 0, 5, 12 and 19 (fresh media), and Days 3, 7, 14 and 21 (old media) showed no measured concentrations above the LOQ of the analytical method employed, determined to be 0.32 mg Si/L, were obtained. On Days 7, 12, 14, 19 and 21, all measured concentrations were below the LOD, determined to be 0.10 mg Si/L. In an attempt to demonstrate a dose response, on Days 12 and 19 a sample of the freshly prepared 3.2 mg/L loading rate WAF from which dilutions were made to give the required test concentrations was taken for analysis. On both occasions measured concentrations below the LOD were observed.Due to a technical oversight a sample of the 0.0032 mg/L loading rate WAF was not provided for analysis on Day 19. This was considered to have had no adverse effect on the outcome of the test given that at this concentration, no measurable levels of silicon were detected over the 21-Day period.Given that the toxicity cannot be attributed to a single component (silicon) or a mixture of components, but to the test item as a whole, the results were based on nominal loading rates only.
Validation CriteriaThe following validation criteria were achieved during the test:
6 to 9
7.0 to 8.5
Lethal Effects on the Parental Generation (P1)
Mortality (immobilization) occurred in the 0.10 and 0.32 mg/L loading rate WAF test groups only (10% and 20%, respectively). Statistical analysis of the mortality data by Fisher’s Exact Binomial Test with Bonferroni Correction incorporating Qualitative Trend Analysis by Contrasts showed that the observed mortalities in the 0.10 and 0.32 mg/L loading rate WAF test groups were not significantly different (P≥0.05) when compared to the control group. However, when compared to the pattern of immobilization observed in the second range-finding test where 40% immobilization occurred at 1.0 mg/L loading rate WAF, it was considered that the effects seen at 0.10 and 0.32 mg/L loading rate WAF were the start of a dose response. As such, the immobilization seen was attributed to exposure of the Daphnia to the test item rather than being considered to have been an incidental response.
Sub-lethal Effects on the Parental Generation (P1)
There was no significant effect on the size and color of the daphnids in the control, 0.0032, 0.010 and 0.032 mg/L loading rate WAF test groups.A single adult in the 0.10 mg/L loading rate WAF test group was observed to be pale on Days 13 and 14 but appeared normal between Days 15 and 21. A single adult in the 0.32 mg/L loading rate WAF test group was observed to be pale on Days 10, 11, 13 but appeared normal between Days 14 and 21.
Inspection of the body length data showed that was no significant difference in body length in any of the test groups when compared to the control.
Effects on Reproduction
After 21 days there were no statistically significant differences (P≥0.05) between the control and the 0.0032, 0.010, 0.032 and 0.10 mg/L loading rate WAF test groups in terms of the number of live young produced per adult. However, a significant difference (P<0.05) was determined between the control and the 0.32 mg/L loading rate WAF test group in terms of number of live young produced per adult after 21 days exposure to the test item (approximately a 23% reduction in number of live young produced at 0.32 mg/L loading rate WAF compared to the control group).
Effects on the Filial Generation (F1)
Information on the effects of the test item on the F1 generation is limited, since, by study design, the young are removed soon after liberation from the brood pouch. However, an assessment made at each media renewal showed the "filial" daphnids produced by the 0.0032, 0.010, 0.032 and 0.10 mg/L loading rate WAF test groups to be in the same general conditions as the young produced in the control group over the duration of the test. Five broods produced on Day 19 and one brood on Day 20 in the 0.32 mg/L loading rate WAF test group were observed to be small and/or pale in comparison to those produced in the control group.Young were first produced in the control test group on Day 8 of the test.On Day 20, three out of the eight control replicates which produced young were observed to contain dead neonates. These amounted to 46 out of the 236 in total produced by the control group on this day (19%). It was not evident from the data as to the cause of the deaths but the 14% loss was considered to have had no adverse effect on the outcome of the test.There were no unhatched eggs or dead young in any of the treatment groups surviving to maturation.
Vortex Depth Measurements
The vortex depth was recorded at the start and end of the mixing period and was observed to have formed a dimple at the media surface.
Observations on Test Item Solubility
Observations on the test media were carried out during the mixing and testing of the WAF.At both the start and end of the mixing period and following a 1-hour standing period the 3.2 mg/L loading rate was observed to be a clear colorless water column with test item adhered to the plastic slide suspended under the water surface. Microscopic examination of the WAF showed there to be no micro-dispersions of test item present.At the start and throughout the test all control solutions were observed to be clear colorless solutions.
The toxicity of the test item to the freshwater invertebrate Daphnia magna was investigated following OECD/EC guidelines and gave a 21-day (semi-static) NOELR of 0.1 mg/L loading rate WAF for reproduction and 0.032 mg/L loading rate WAF for immobilisation.
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