Tris(2-ethylhexyl) orthoborate

Endpoint summary

Additional information

Abiotic degradation; Hydrolysis

Investigation of the test item via Method 111 of the OECD Guidelines for Testing of Chemicals, 12 May 1981, was not possible due to the absence of a suitable substance-specific method of analysis. However, hydrolytic behaviour was obtained through exposure of test material solutions to aqueous buffers and subsequent NMR analysis. Hydrolytic half-life was shown to be less than 10 minutes at pH 1.2 (37.0 ± 0.5 °C) and pH 4, 7 and 9 (25.0 ± 0.5°C).

Biodegradation

Key study

 

In a key study performed on an analogue substance to OECD Guideline No. 301B and EC Method C.4-C: CO2 Evolution test the test item, at a concentration of 10 mg Carbon/L, was exposed to activated sewage sludge micro-organisms with mineral medium in sealed culture vessels in the dark at approximately 21°C for 28 days.

 

Following the recommendations of ISO 1995, the test item was dissolved in an auxiliary solvent prior to being absorbed onto filter paper and subsequent dispersal in the test media. Using this method the test item is evenly distributed throughout the test medium and the surface area of test item exposed to the test organisms is increased thereby increasing the potential for biodegradation.

 

The biodegradation of the test item was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the reference item sodium benzoate, together with a toxicity control were used for validation purposes.

 

The test item is an unstable UVCB substance in aqueous conditions and hydroyses rapidly (less than 30 minutes). The water solubility of the test item is therefore equivalent to the water solubility of the two main degradation products boric acid and 2-propyl heptan-1-ol. Both degradation products have been registered under REACH. Boric acid is an inorganic substance with high water solubility and will not undergo biodegradation. 2-propyl heptan-1-ol is a poorly soluble substance (> 100 mg/L) and is readily biodegradable with over 90% degradation in 28-days.

 

The analogue test item attained 74% biodegradation after 28 days. As the test material is a UVCB the 10 -day window validation criterion are not applicable. Therefore, the test material can be considered to be readily biodegradable. The organic degradation product derived from hydrolysis of the test item is readily biodegradable.

 

Supporting study

 

The study was conducted in compliance with OECD Guidelines for the Testing of Chemicals No 301 B "CO2 Evolution Test" (adopted 17 July 1992) and the Guidelines for the Testing of Chemicals, SEPA, P.R. China No 301 B "CO2 Evolution Test" (May 2004).

 

The study was conducted in activated sludge in an aerobic aqueous medium. The results showed that the ThCO2 was 110.095 mg. The accumulated percentage biodegradation on Days 2, 4, 5, 6, 7, 9, 11, 13, 17, 21 and 28 after treatment were 0.129 %, 3.680 %, 12.935 %, 17.484 %, 22.622 %, 27.871 %, 30.913 %, 32.932 %, 35.509 %, 38.119 % and 44.621 % respectively.

 

According to the grading criteria in the Guidelines for the Hazard Evaluation of New Chemical Substances, State Environmental Protection Agency of P.R. China (HJ/T 154-2004), the test item was not readily biodegradable under the conditions of the test.

Adsorption / desorption coefficient (Koc)

Hydrolytic instability of the test material meant that testing via Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001 was not possible. Therefore the adsorption coefficient of the test material, and its proposed hydrolysis products for environmental consideration, was estimated by Quantitative Structure Activity Relationships (QSAR). The estimated values of adsorption coefficient obtained by QSAR, using Log10 Pow values were calculated to be 5.28 for the test material, 1.78 for 2-ethylhexanol and 0.40 for boric acid.