Tris(2-ethylhexyl) orthoborate

Endpoint summary

Additional information

Fish

 

Acute toxicity was investigated in a key study conducted on zebra fish (Brachydanio rerio) under semi-static conditions and, based on results from preliminary testing, concentration levels of the test item were selected as 9.70, 14.85, 22.75, 34.83 and 53.35 mg/L (factor of 1.53). A control group was used in parallel and three replicates for each group (including the test groups and the control group) were performed. The water was filtrated with an active carbon filter (PCF-1200, made in Japan). Concentrations of the test item, dissolved oxygen and pH were determined 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. During the 96 hour exposure period, toxic signs and mortality were observed and recorded.

 

The LC50 at 96 h was calculated as 21.17 mg/L and the 95 % confidence limits were 17.50 - 26.63 mg/L based on mortality. Based on this result and the fish toxicity grading criteria in the Guidelines for Hazard Evaluation of New Chemical Substances, Environmental Protection Agency of P.R.C. (HJ/T 154 -2004), the test material is graded as a chemical with middle fish toxicity under the experimental condition of the study.

 

Daphnia

 

A key study was performed on an analogue substance to assess the acute toxicity of the test item toDaphnia magna. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (April 2004) No 202, "Daphnia sp. Acute Immobilisation Test" referenced as Method C.2 of Commission Regulation (EC) No. 440/2008.

 

Due to the low aqueous solubility and pure nature of the test item, for the purposes of the definitive test, the test solutions were prepared from a slow stir saturated solution.

 

Following a preliminary range-finding test, twenty daphnids (4 replicates of 5 animals) were exposed to the test item over a range of nominal concentrations of 1.0, 1.8, 3.2, 5.6 and 10% v/v saturated solution for 48 hours at a temperature of approximately 21 °C under static test conditions. The numbers of immobilized Daphnia and any adverse reactions to exposure were recorded after 24 and 48 hours.

 

Chemical analysis of the 3.2, 5.6 and 10% v/v saturated solutions at 0 and 48 hours showed measured boron concentrations to range from 0.078 to 0.25 mg/L. TOC analysis of the 3.2, 5.6 and 10% v/v saturated solutions at 0 and 48 hours showed measured carbon concentrations to range from 1.4 to 3.7 mg/L (equivalent to test item concentrations of 1.9 to 4.9 mg/L based on a test item carbon content of 75.78%). It was considered appropriate to calculate the results based on the equivalent test item concentrations obtained from TOC analysis as these results give an estimate of the total dissolved test item concentrations present.

 

Exposure of the test item to the freshwater invertebrate Daphnia magna gave a 48-Hour E C50 value of 2.6 mg/L (95% CI = 2.3 - 2.8 mg/L). The No Effect Concentration was 1.9 mg/L and the LOEC was considered to be 2.7 mg/L.

 

Algae

 

A key study was performed to assess the effect an analogue substance on the growth of the green alga Pseudokirchneriella subcapitata. The method followed that described in the OECD Guidelines for Testing of Chemicals (2006) No 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test" referenced as Method C.3 of Commission Regulation (EC) No 761/2009.

 

Due to the low aqueous solubility and pure nature of the test item, for the purposes of the definitive test, the test medium was prepared as a slow stir saturated solution. Following preliminary range-finding tests, Pseudokirchneriella subcapitata was exposed to solutions of the test item at nominal concentrations of 1.0, 3.2, 10, 32 and 100% v/v saturated solution (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1 °C. The test item solutions were prepared by stirring an excess (100 mg/L) of test item in culture medium using a magnetic stirrer at a rate such that a dimple was formed at the water surface for 23 hours. After the stirring period, the saturated solution was allowed to stand for 1-Hour prior to the removal of any undissolved test item by filtration through a glass wool plug (first approximate 75-100 mL discarded) to produce a 100% v/v saturated solution of the test item. This saturated solution was then further diluted as necessary, to provide the remaining test groups. Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter® Multisizer Particle Counter.

 

Chemical analysis of the test preparations at 0 and 72 hours showed measured boron concentrations to range from 0.070 to 2.5 mg/L. Total Organic Carbon (TOC) analysis of test preparations at 0 and 72 hours showed measured carbon concentrations to range from less than the limit of quantification (LOQ), determined to be 1.0 mg C/L at 1.0% v/v saturated solution, through to 32 mg/L at 100% v/v saturated solution (equivalent to test item concentrations of less than the LOQ to 42 mg/L based on a test item carbon content of 75.78%). It was considered appropriate to calculate the results based on the equivalent test item concentrations obtained from TOC analysis as these results give an estimate of the total dissolved test item concentrations present.

 

Exposure of the test item to Pseudokirchneriella subcapitata gave a 72-Hour EC50 value based on growth rate of 9.0 mg/L (95% CI = 7.8 -11 mg/L). The No Effect Concentration was 1.9 mg/L and the LOEC was considered to be 5.1 mg/L.