O,O,O',O'-tetraoctyl-(branched and linear) S,S'-{methylenebis[imino(3-oxopropane-3,1-diyl)]} bis(phosphorothioate)

Endpoint summary

Additional information

Acute

Fish

In a key study performed to assess the acute toxicity of the test material to rainbow trout (Onchorhynchus mykiss), the method followed that described in the OECD Guidelines for Testing of Chemicals (1992) No. 203, “Fish Acute Toxicity Test” referenced as Method C.1 of Commission Directive 92/69/EEC.

Following a preliminary range finding study, fish were exposed in groups of ten to a Water Accommodated Fraction (WAF) of the test material at a single nominal loading rate of 100 mg/L for a period of 96 hours under semi-static test conditions. The number of mortalities and any sublethal effects of exposure in each test and control vessel were determined 3 and 6 hour after the start of exposure and then daily throughout the test until termination after 96 hours.

The 96 hour LL50 based on nominal loading rates was greater than 100 mg/L WAF and correspondingly the No Observed Effect Loading rate was 100 mg/L. It was considered unnecessary and unrealistic to test at loading rates in excess of 100 mg/L..

In a supporting study, the acute toxicity of the test item was conducted in zebra fish. Based on the results of a preliminary test, the concentration level of 100 mg/L was selected for the limit test. A control group containing DMF was performed in parallel. Three replicates for each group (including the test groups and the control group) were used. The study was performed with a semi-static system. The water was filtered with an activated carbon filter. Dissolved oxygen and pH values were recorded at the beginning of the test and at 24 hour intervals during the 96 hour exposure period. Water hardness and total alkalinity were measured at the beginning of the test in the control solutions. During the 96 hour exposure period, observations were made for potential toxic signs and mortality in fish. The LC50 at 96 hours was above 100 mg/L. 

Daphnia

The key study was performed to assess the acute toxicity of the test material to Daphnia magna. The method followed that described in the OECD Guidelines for Testing of Chemicals (1984) No. 202, referenced as Method C.2 of Commission Directive 92/69/EEC.

 Following a preliminary range-finding test, forty daphnids (4 replicates of 10 animals) were exposed to a Water Accommodated Fraction (WAF) of the test material, at a single nominal loading rate of 100 mg/L for 48 hours under static test conditions. Immobilisation and any adverse reactions to exposure were recorded after 24 and 48 hours.

 The 48 hour EL50 for the test material to Daphna magna was greater than the 100 mg/L loading rate WAF and the No Observed Effect Loading rate was 100 mg/L. It was considered unnecessary and unrealistic to test at loading rates in excess of 100 mg/L.

Algae

The key study was performed to assess the effect of the test material on the growth of the green algaScenedesmus subspicatus. The method followed that described in the OECD Guidelines for Testing of Chemicals (1984) No. 201, “Alga, Growth Inhibition Test” referenced as Method C.3 of Commission Directive 92/69/EEC.

 Following a preliminary range finding study,Scenedesmus subspicatuswas exposed to a Water Accommodated Fraction (WAF) of the test material at a loading rate of 100 mg/L (six replicate flasks) for 72 hours, under constant illumination and shaking at a temperature of 24 + 1 degrees C. Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group using a Coulter Multisizer II Particle Counter.

 Exposure ofScenedesmus subspicatusto the test material gave ELR50 values of greater than 100 mg/L loading rate WAF and correspondingly the No Observed Effect Loading Rate was 100 mg/L loading rate WAF. It was considered unnecessary and unrealistic to test at concentrations in excess of 100 mg/L loading rate WAF. Analysis of the test preparations at 0 hours showed the measured test concentrations to be 0.8% of nominal. Analysis of test preparations at 72 hours showed a decline to below the limit of quantitation of the analytical method. This decline is considered to be due to adsorption to algal cells. Given that the concentration of the test material in the 72 hour test samples was less than the limit of quantitation of the analytical method, and because the test item is a complex substance requiring use of the WAF approach, ELR50 values are based on nominal loading rates.

Sewage sludge micro-organisms

The potential impact of the test item on microbial metabolism, as represented by the consumption of oxygen, was investigated using the “Activated Sludge, Respiration Inhibition Test” as prescribed by OECD 1984 and detailed in OECD 209. The test was performed on March 10, 1994. The test duration was a three hour exposure period to the test material followed by up to ten minutes for the measurement of oxygen consumption. The study design was comprised of five nominal exposure concentrations: 1, 10, 100, 1,000, and 10,000 mg/L; a duplicate control group; and an assessment of the sensitivity of the inoculum used in the test to a reference toxicant 3,5-dichlorophenol. The activated sludge respiration test with the test item passed the quality control criteria for an acceptable test. The EC50 calculated for the reference toxicant was 5.0 mg/L within the acceptable range of 5 to 30 mg/L. The two control replicates produced oxygen consumption rates within the required 15% of each other, 30.0 and 28.2 mg O2/L*hr. The respiration rates of the sludge associated microbes exposed to the five nominal concentrations of the test item were 23.5, 22.5, 23.0, 23.4, and 28.9 mg O2/L*hr respectively. The EC50 was calculated to be greater than 10,000 mg/L.

Chronic

Daphnia

In a key study performed to assess the chronic toxicity of the test item to Daphnia magna, the method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (2008) No 211, "Daphnia magna Reproduction Test" referenced as Method C.20 of Commission Regulation (EC) No. 440/2008 and the US EPA Draft Ecological Effects Test Guidelines OPPTS 850.1300 "Daphnid Chronic Toxicity Test".

Due to the low aqueous solubility and complex nature of the test item, for the purposes of the test, the test item was prepared as a Water Accommodated Fraction (WAF).

Based on the results of a preliminary range finding test, Daphnia magna were exposed (10 replicates of a single daphnid per group) to a Water Accommodated Fraction (WAF) of the test item at a single nominal loading rate of 100 mg/L for a period of 21 days. The test solutions were renewed 3 times per week. The numbers of live and dead adult Daphnia and young daphnids (live and dead) were determined daily. The Daphnia were fed daily with a mixture of algal suspension and Tetramin® flake food suspension.

Chemical analysis of the freshly prepared test preparations showed measured concentrations to range from less than the Limit of Quantification (LOQ) of the analytical method, determined to be 0.010, to 1.11 mg/L. Chemical analysis of the aged preparations showed measured test concentrations to range from less that the LOQ to 0.464 mg/L.

Given that toxicity cannot be attributed to a single component or mixture of components, but to the test item as a whole, the results were based on nominal loading rates only.

The 21-Day EL50 (immobilization) value, based on nominal test concentrations, for the parental Daphnia generation (P1) was estimated to be greater than 100 mg/L loading rate WAF.

The 21-Day EL 50 (reproduction) value based on nominal test concentrations was estimated to be greater than 100 mg/L loading rate WAF.

The "No Observed Effect Loading Rate" was considered to be 100 mg/L loading rate WAF on the basis that at this test concentration there were no significant mortalities (immobilization) observed in the parental generation (P1) and that there were no significant differences (P> =0.05) between the control and the 100 mg/L loading rate WAF test group in terms of numbers of live young produced per adult by Day 21. The "Maximum Acceptable Toxicant Loading Rate" was calculated to be 100 mg/L loading rate WAF. It was considered unnecessary and unrealistic to test loading rates in excess of 100 mg/L.