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EC number: 293-927-7 | CAS number: 91648-65-6
Daphnia magna_OECD 202: EL50(48h): 41 mg/L WAF RA_1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol (No CAS, no EC)_Daphnia magna_EU Method C.2: available results are not suitable to calculate the EL50, so it is estimated by the geometric mean EL0/EL100 = 50mg/L WAF RA_1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol (No CAS, no EC)_Daphnia magna_OECD 202/ISO 6341 15: EL50(48h): 10 - 50 mg/L WAF, approx. 36 mg/L WAFRA_1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol (No CAS, no EC)_Daphnia magna_OECD 202: an exact calculation of the EL50 cannot be done; EL50(48h) < 100 mg/L WAF
The acute toxicity of 1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-nonanethiol (CAS 91648-65-6) towards Daphnia magna was investigated according to OECD 202 / EU Method C.2 under certificated GLP compliance (Vryenhoef, 2012). Daphnia magna is a freshwater representative of a wide variety of natural habitats and can therefore be considered as an important non-target organism in freshwater ecosystems. Based on the poor water solubility of the test substance (< 0.1 mg/L, Fox, 2012), a modification of the standard method for the preparation of aqueous media was performed. Using the approach of Water Accommodated Fractions (WAFs), based upon an approach by several important regulatory authorities in the EU and elsewhere, aqueous media are prepared by mixing the test substance with water for a prolonged period. Pre-study work showed that a preparation period of 24 hours was sufficient to ensure equilibration between the test substance and the water phase. After a 1-hour settlement period, the test substance is phase separated by siphon and the test organisms exposed to the aqueous phase or WAF. Following a preliminary range-finding test, twenty daphnids (4 replicates of 5 animals) were exposed to the WAFs over a range of nominal loading rates of 10, 18, 32, 56 and 100 mg/L for 48 h at a temperature of 21 - 22 °C under static test conditions. The number of immobilized Daphnia and any adverse reactions to exposure were recorded after 24 and 48 hours. The water temperature was recorded daily, dissolved oxygen concentration and pH were recorded at the start and termination of the experiment. Immobilization of daphnids was observed after 24 h and 48 h. After an exposure period of 24 h 50 % of daphnids were immobilized at 56 mg/L WAF. Therefore, the EL50(24h) is reported as 56 mg/L. After 48 h, all daphnids were immobilized at 56 mg/L WAF. Based on statistical interpolation, the EL50(48h) is determined as 41 mg/L with 95 % confidence limits of 39 - 43 mg/L WAF. The LOELR(48h) was considered to be 56 mg/L WAF and the NOELR(48h) is 32 mg/L WAF.
Daphnia magna was also used test organisms in experiments with the read-across substance 1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol (No CAS, no EC). Caspers (1999) exposed young daphnids for a duration of 48 hours to the substance under static conditions. The photoperiod was chosen as 16 h light and 8 h dark. Considering the heterogenous composition of the test substance, Water Accommodated Fractions (WAFs) were prepared. No analysis was included. Physico-chemical parameters were measured after 24 and 48 hours. The EC0 and EC100 values were determined directly from the study, while the EC50 was calculated from the dose-response curve obtained. Based on this, the test material can not be classified distinctly due to the studies conduction as limit test and unavailability of measured test concentrations. However, the experiment is reliable with restrictions and satisfies the guideline requirements for an acute toxicity study with freshwater invertebrates.
The same test principles were applied by Bouillon (2006). In this experiment, daphnids were exposed to control and test chemical at nominal concentration of 12.5, 48.6, 171 and 1486 mg/L WAF for 48h. Immobilization was observed daily. The 48h-EL50 was determined to be 10-50 mg/L WAF, thus approx. 36mg/L WAF. The report available is only a short summary of the study and the real concentrations of the test substance are unknown since no analytical analysis was included. Hence, the reliability of the test is limited. Thus the EL50 value can not be relied on.
In another study, the toxicity towards the aquatic invertebrates was investigated in a static limit test conducted in accordance to OECD 202 (Weyandt and Lebertz, 2005). The nominal test concentration was 100 mg/L, whereby the solution was prepared as Water Accommodated Fraction (WAF), although not explicit mentioned in the study report. Immobilization was observed daily. Physico-chemical parameters were recorded at the beginning and the end of the experiment. The percentage of immoblized daphnids was 75 % after 24 h and 100 % after 48 h, respectively. Therefore, the EC0(48h) as well as the EC50(48h) is < 100 mg/L WAF, whereas the EC100(48h) is > 100 mg/L WAF. No analytical measurements were performed. Based on this study, the test material can not be classified distinctly due to the studies conduction as limit test and unavailability of measured test concentrations.
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