tris(branched-alkyl) borate

Endpoint summary

Description of key information

Short term toxicity to fish

In the key study, exposure of rainbow trout to the test item gave an LC50 (96 h) value of 1.3 mg/L (95 % confidence limits 1.1 to 1.6 mg/L) based on carbon content. The No Observed Effect Concentration (NOEC) based on carbon content was 1.1 mg/L and the Lowest Observed Effect Concentration (LOEC) based on carbon content was 1.6 mg/L. With respect to boron content, the LC50 (96 h) value was determined to be 8.4 mg/L (95 % confidence limits 6.4 to 11 mg/L). The No Observed Effect Concentration (NOEC) based on boron content was 6.4 mg/L and the Lowest Observed Effect Concentration (LOEC) based on boron content was 11 mg/L (OECD 203 and EU Method C.1). In a supporting study, exposure of Gobiocypris rarus to the test item reported an LC50 (96 h) value of 0.57 mg/L (95 % confidence limits 0.51 to 0.65 mg/L based on measured concentration). The maximum tested concentration causing no mortality was 0.221 mg/L and the minimum concentration causing 100 % mortality was 0.798 mg/L (OECD 203, relevant Chinese guidelines and OPPTS 850.1075).

Long term toxicity to fish

Following exposure of Gobiocypris rarus to test substance, the LOEC (28 d) was determined to be > 8 % v/v saturated solution (measured concentration 0.171 mg/L) and the NOEC (28 d) was reported as 8 % v/v saturated solution (measured concentration 0.171 mg/L) (OECD 215 and relevant Chinese guidelines).

Short term toxicity to Daphnia

Exposure of the test item to the freshwater invertebrate Daphnia magna gave a 48-Hour EC50 value of 2.6 mg/L based on carbon content (95 % confidence limits 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. With respect to boron content, the EC50 (48-hour) value was determined to be 5.7 mg/L (95 % confidence limits 5.0 to 6.3 mg/L); the No Observed Effect Concentration (NOEC) was 3.6 mg/L and the Lowest Observed Effect Concentration (LOEC) was 6.3 mg/L.

(OECD 202 and EU Method C.2).

Long term toxicity to Daphnia

Exposure of Daphnia magna to the test item resulted in significant mortalities at the nominal test concentration of 5.0 % v/v saturated solution resulting in 50 % mortalities by Day 14. Based on equivalent test item concentrations from Total Organic Carbon (TOC) analysis, exposure of Daphnia magna to the test item gave EC10 (21 d) 0.81 mg/L and EC50 (21 d) 1.4 mg/L based on immobilisation. The EC10 (21 d) was 0.63 mg/L and the EC50 (21 d) value was 0.85 mg/L based on reproduction. The No Observed Effect Concentration (NOEC) was reported as 0.34 mg/L, the Lowest Observed Effect Concentration (LOEC) was 0.69 mg/L and the Maximum Acceptable Toxicant Concentration (MATC) was 0.48 mg/L. Based on equivalent test item concentrations from boron analysis, exposure of Daphnia magna to the test item gave EC10 (21 d) 3.7 mg/L and EC50 (21 d) 5.6 mg/L based on immobilisation. The EC10 (21 d) was 3.0 mg/L and the EC50 (21 d) value was 3.8 mg/L based on reproduction. The No Observed Effect Concentration (NOEC) was reported as 1.9 mg/L, the Lowest Observed Effect Concentration (LOEC) was 3.3 mg/L and the Maximum Acceptable Toxicant Concentration (MATC) was 2.5 mg/L (OECD 211, EU Method C.20 and OPPTS 850.1300).

Algae

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 (OECD 201 and EU Method C.3).

Microorganisms

The effect of the test item on the respiration of activated sewage sludge gave a 3-Hour EC50 value of 230 mg/L. A No Observed Effect Concentration (NOEC) was not identified (OECD 209).

Additional information

Short term toxicity to fish

A key study was performed to assess the acute toxicity of the test item to rainbow trout (Oncorhynchus mykiss). The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (1992) No 203 “Fish, Acute Toxicity Test” referenced as Method C.1 of Commission Regulation (EC) No 440/2008.

 

Due to the low aqueous solubility and pure nature of the test item, the test medium was prepared as a slow stir saturated solution for the purposes of the definitive test. Following a preliminary range-finding test, fish were exposed, in groups of seven, to the test item over a range of nominal concentrations (1.0, 1.8, 3.2, 5.6 and 10 % v/v saturated solution) for a period of 96 hours at a temperature of 14 °C under semi-static conditions. The number of mortalities and any sub-lethal effects of exposure were determined in each test and control vessel at 3 and 6 hours after the start of exposure and then daily throughout the test until termination after 96 hours.

 

Chemical analysis of the 5.6 and 10 % v/v saturated solution test preparations at 0 and 72 hours (fresh media) and at 24 and 96 hours (old media) showed measured boron concentrations of 0.13 to 0.24 mg/L (equivalent to test item concentration of 6.06 to 11.09 mg/L based on a test item boron content of 2.146 %). Total Organic Carbon (TOC) analysis of the 1.0, 1.8, 3.2, 5.6 and 10 % v/v saturated solution test preparations at 0 and 72 hours (fresh media) and at 24 and 96 hours (old media) showed measured carbon concentrations of less than the limit of quantification of the analytical method (LOQ 1.0 mg C/L to 3.01 mg C/L; equivalent to test item concentrations of less than LOQ to 4.0 mg/L based on test item carbon content of 75.78 %).

 

Exposure of rainbow trout to the test item gave an LC50 (96 h) value of 1.3 mg/L (95 % confidence limits 1.1 to 1.6 mg/L) based on carbon content. The No Observed Effect Concentration (NOEC) based on carbon content was 1.1 mg/L and the Lowest Observed Effect Concentration (LOEC) based on carbon content was 1.6 mg/L. With respect to boron content, the LC50 (96 h) value was determined to be 8.4 mg/L (95 % confidence limits 6.4 to 11 mg/L). The No Observed Effect Concentration (NOEC) based on boron content was 6.4 mg/L and the Lowest Observed Effect Concentration (LOEC) based on boron content was 11 mg/L.

 

In a supporting study, the acute toxicity of the test item to Gobiocypris rarus was investigated under static conditions in accordance with The Guidelines for the testing of chemicals (HJ/T 153-2004) and with reference to Procedure 203 of the Guidelines for Testing of Chemicals “Fish Acute Toxicity Test” (OECD; 1992).

 

A range-finding test was performed followed by a definitive test. Nominal concentrations of 1.0, 10.0 and 100 mg/L were used in the range finding test and nominal concentrations of 10 %, 20 %, 40 %, 60 %, 80 % and 100 % v/v saturated solution were used in the definitive test. The stock solution was 100 % saturated solution prepared by dissolving 0.3001 g or 0.3002 g of test material in 3 L of test media and this was diluted to obtain 10 %, 20 %, 40 %, 60 % and 80 % v/v saturated solutions. Water samples taken from blank control and treatment groups in the definitive test were analysed. Five fish were used for the range-finding test (no replicates) and ten fish per treatment were used for the definitive test (no replicates). The fish were exposed to test item for 96 hours.

 

Concentrations of test substance were quantified using ICP-MS and the measured concentrations were 0.221 mg/L (10 %), 0.470 mg/L (20 %), 0.798 mg/L (40 %), 1.16 mg/L (60 %), 1.68 mg/L (80 %) and 2.00 mg/L (100 %). The analytical results showed that the concentration of test item was consistent in the test medium throughout the 96-hour study period (deviation within 20 %) and that a static procedure was reasonable. During the test period, all fish in the control and 10 % treatment group were alive and appeared normal. Effects (fish lying on side or back) occurred at nominal test concentrations of 20 % v/v saturated solution. All fish were dead after 96 hours exposure at a nominal test concentration of 40 % v/v saturated solution. A positive control substance (K2Cr2O7) assessed under the same conditions gave an LC50 (24 h) value of 269 mg/L. The study met the acceptability criteria prescribed by the protocol (pH 6.0 to 8.5; dissolved oxygen concentration > 60 % of the air saturation value; total hardness 10 to 250 mg/L as CaCO3; temperature 23 ± 2 °C; LC50 (24 h) for K2Cr2O7 in the range 200 to 400 mg/L).

 

The results showed that under valid static test conditions the LC50 (96 h) value was 0.57 mg/L (95 % confidence limits 0.51 to 0.65 mg/L based on measured concentration). The maximum tested concentration causing no mortality was 0.221 mg/L and the minimum concentration causing 100 % mortality was 0.798 mg/L.

 

Long term toxicity to fish

The key study was designed to determine the effect on growth rates and other endpoints in juvenile fish (Gobiocypris rarus) exposed to test substance. The study met the requirements of HJ/T 153-2004, The guidelines for the testing of chemicals [S], Beijing: SEPA, 2004, CRC-MEP; The Guidelines for the Testing of Chemicals, Effects on Biotic Systems [M] 2nd edition, Beijing: China Environment Press, 2013: 135-144;GB/T21806-2008, Chemicals - Fish juvenile growth test, Beijing: SAC, 2008; Guidelines for Testing of Chemicals, 215,Fish, Juvenile Growth Test [S], OECD,2000.

In accordance with results from an acute toxicity test, fish were exposed to nominal concentrations of 1 %, 2 %, 4 %, 5 %, 8 % and 10 % v/v saturated solution prepared by diluting a saturated (100 %) stock solution (0.3000 to 0.3003 g test substance dissolved in 3 L test media). Concentrations of the test substance were quantified by ICP-MS. A linear regression equation A = 867816c + 6030.3 was obtained from the peak area values versus the concentration of test item (0.02, 0.05, 0.10, 0.20 and 0.30 mg/L) and good linearity was observed (r2 = 0.993). The analytical results showed that mean concentration of test item with nominal concentrations of 1 % and 8 % v/v saturated solutionwere 0.020 mg/L and 0.171 mg/L respectively. The test solution was stable throughout the 72 hour investigation (deviation within 20 %) showing that a semi-static test with 72-hour renewal was reasonable.

The pH values of the control and test media were between 7.84 and 8.04 during the test. Dissolved oxygen values varied from 74 % to 94 % of air saturation and the temperature of test media was maintained at 23.1 to 23.5 °C. The mean weight of the fish in the control group increased by > 50 %. The study met the acceptability criteria of the protocol (dissolved oxygen concentration no less than 60 % of air saturation; temperature 23 ± 2 °C with a difference of no more than ± 1 °C between chambers; the increasing rate of fish mean wet weight no less than 50 % of initial weight). Under the valid, semi-static, test conditions, no fish died in the control or 1 %, 2 %, 4 % and 5 % v/v saturated solution treatment groups. Effects (fish lying on side or back) occurred at nominal test concentrations of 8 % and 10 % v/v saturated solution. All fish were dead after three days exposure at a nominal concentration of 10 % v/v saturated solution. This result was slightly different to the acute toxicity result and suggested the juveniles may be more sensitive to the test substance.

The LOEC (28 d) was determined to be > 8 % v/v saturated solution (measured concentration 0.171 mg/L) and the NOEC (28 d) was reported as 8 % v/v saturated solution (measured concentration 0.171 mg/L).

 

Short term toxicity to Daphnia

A study was performed to assess the acute toxicity of the test item to Daphnia 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%).

Exposure of the test item to the freshwater invertebrate Daphnia magna gave a 48-Hour EC50 value of 2.6 mg/L based on carbon content (95 % confidence limits 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. With respect to boron content, the EC50 (48 -hour) value was determined to be 5.7 mg/L (95 % confidence limits 5.0 to 6.3 mg/L); the No Observed Effect Concentration (NOEC) was 3.6 mg/L and the Lowest Observed Effect Concentration (LOEC) was 6.3 mg/L.

 

Long term toxicity to Daphnia

A study was performed to assess the chronic toxicity of the test item to Daphnia magna. The method was designed to be compatible with the OECD Guidelines for Testing of Chemicals (2012) 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 Guideline OPPTS 850.1300 “Daphnid Chronic Toxicity Test”.

 

Due to the low aqueous solubility and pure nature of the test item, the medium was prepared as a slow stir saturated solution for the definitive test. Based on the results of an acute toxicity study, Daphnia magna were exposed (10 replicates of a single daphnid per group) to a solution of the test item over a range of test concentrations (0.31, 0.63, 1.25, 2.5 and 5.0 % v/v saturated solution) for a period of 21 days. The test solutions were renewed three times per week during the test. The number 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 fresh test preparations on days 0, 5, 9, 14 and 19 plus the old test preparations on days 2, 7, 12, 16 and 21 showed boron concentrations to range from less than the Limit of Quantification (LQQ) for the analytical method (determined to be 0.025 mg/L) to 0.13 mg/L (equivalent to test item concentrations of less than the LQQ to 6.15 mg/L based on test item boron content of 2.146 %). Total Organic Carbon (TOC) analysis of the fresh test preparations on days 0, 5, 9, 14 and 19 plus the old test preparations on days 2, 7, 12, 16 and 21 showed measured carbon concentrations to range from less than the LQQ of the analytical method (assessed as being 1.0 mg C/L) to 3.7 mg/L (equivalent to test item concentrations of less than the LQQ to 4.9 mg/L based on test item carbon content of 75.78 %). Given that values of less than the LQQ were obtained for many of the sampling points at the lower nominal concentrations, it was considered appropriate to calculate the equivalent time weighted mean measured test item concentration of the 5.0 % v/v saturated solution and calculate the remaining equivalent test concentrations based on that value.

 

Based on equivalent test item concentrations from Total Organic Carbon (TOC) analysis, exposure of Daphnia magna to the test item gave EC10 (21 d) 0.81 mg/L and EC50 (21 d) 1.4 mg/L based on immobilisation. The EC10 (21 d) was 0.63 mg/L and the EC50 (21 d) value was 0.85 mg/L based on reproduction. The No Observed Effect Concentration (NOEC) was reported as 0.34 mg/L, the Lowest Observed Effect Concentration (LOEC) was 0.69 mg/L and the Maximum Acceptable Toxicant Concentration (MATC) was 0.48 mg/L. Based on equivalent test item concentrations from boron analysis, exposure of Daphnia magna to the test item gave EC10 (21 d) 3.7 mg/L and EC50 (21 d) 5.6 mg/L based on immobilisation. The EC10 (21 d) was 3.0 mg/L and the EC50 (21 d) value was 3.8 mg/L based on reproduction. The No Observed Effect Concentration (NOEC) was reported as 1.9 mg/L, the Lowest Observed Effect Concentration (LOEC) was 3.3 mg/L and the Maximum Acceptable Toxicant Concentration (MATC) was 2.5 mg/L.

 

Algae

A study was performed to assess the effect of the test item 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.

 

Micro-organisms

A study was performed to assess the effect of the test item on the respiration of activated sewage sludge. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (2010) No. 209 "Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation)".

Following a preliminary range finding study activated sewage sludge was exposed to an aqueous dispersion of the test item at concentrations of 100, 180, 320, 560 and 1000 mg/L (3 replicates) for a period of 3 hours at a temperature of approximately 20 to 22°C with the addition of a synthetic sewage as a respiratory substrate. The rate of respiration was determined after 3 hours contact time and compared to data for the control and a reference item, 3,5-dichlorophenol.

The reference item gave a 3 -hour EC50 value of 7.6 mg/L (95% confidence limits of 6.0 - 9.7 mg/L). The effect of the test item on the respiration of activated sewage sludge gave a 3-Hour EC50 value of 230 mg/L. A No Observed Effect Concentration (NOEC) was not identified.