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EC number: 946-103-2 | CAS number: -
Nominal Test Item Loading
Cell Density [cells/mL]
Evaluation after 72 hours
Statistically significant differences of growth rates and yield compared to
control values are marked (+), not significant differences are marked (-).
Growth Rate Inhibition
100 neutralized (pH-control)
Section-by-Section and Average Specific Growth Rates of the Control Group (0 – 72 hours)
Specific Growth Rate [d-1]
(0 - 72 h)
Mean CV [%]
0 - 24 hours
24 - 48 hours
48 - 72 hours
The toxicity of celitement to the unicellular freshwater green alga Desmodesmus subspicatuswas determined according to the principles of OECD 201 (2011) at Dr.U.Noack-Laboratorien in 31157 Sarstedt, Germany from2014-03-31 to 2014-04-04 with the definitive exposure phase from 2014-04-01 to 2014-04-04. The aim of the study was to assess the effects on growth rate and yield over a period of 72 hours.
The test item is a mixture, solid and insoluble in water. In view of the difficulties associated with the evaluation of aquatic toxicity of complex mixture test items, a modification of the standard method for the preparation of aqueous media was performed. An approach endorsed by several important regulatory authorities in the EU and elsewhere (ECETOC 1996 and OECD 2000), is to expose the organisms to a Water Accommodated Fraction (WAF*) of the test item in cases where the test item is a complex mixture. Exposures are expressed in terms of the original concentration of the test item in water at the start of the mixing period (loading rate) irrespective of the actual concentration of the test item in the WAF.
The study was conducted under static conditions with an initial cell density of 4998 cells/mL. One limit loading of 100 mg/L of the test item was prepared. The test item was applied onto a glass slide. The glass slide with the test item was inserted in a brown glass flask with an appropriate amount of dilution water. This dispersion was shaken for 24 hours with 20 rpm at room temperature.After a separation phase of 1 hour,the aqueous phase or WAF was removed by siphoning (from the approximate centre of the glass flask) to give the 100 mg/L loading rate WAF. The water soluble fraction was clear. Six replicates were tested for the limit loading, the pH - neutralized limit loading (pH – control) and for the control. Environmental conditions were within the acceptable limits.
The concentrations of the test item celitement were analytically evaluated via photometric analysis of silicon at the start of the exposure (0 h) and at the end of the exposure (72 h) of the limit loading level, the pH-control and the control.
The measured silicon concentration at the start of the exposure (0 h) was 7.45 mg/L in the limit loading level and 7.65 mg/L in the pH-control. At the end of the exposure the measured silicon concentrations gave recoveries of 98 and 102 % of the initially measured values of the limit loading and the pH-control indicating the stability of the test item in the WAF during the exposure phase.All effect values given are based on the nominal test item loading of celitement.
* Water accommodated fractions (WAF): The aqueous medium containing only the fraction of a multi-component test item that is dissolved and / or present as a stable dispersion/emulsion under test conditions in the test medium, acc. to OECD Guidance Document, No. 23.
Short-term toxicity testing with the freshwater green alga Desmodesmus subspicatus was carried out according to the OECD 201 guidance taking into account GLP and thus resulting in a Klimish 1 score. No acute toxicity was observed.
The NOEC-value of the test item for both, inhibition of growth rate and inhibition of yield, after 72 hours was < 100 mg/L. The EC50-values of the test item for inhibition of growth rate (ErC50) and yield (EyC50) after 72 hours were both > 100 mg/L, respectively.
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