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Biodegradation in water: screening tests

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Description of key information

Partially unsaturated TEA-Esterquat is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

There are 20 reliable studies available for biodegradability screening tests of the esterquats .

The ready biodegradability ofTEA-Esterquat partially unsaturated was investigated in a study conducted according to OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test). The test item proved to be readily biodegradable (78.8 % biodegradation after 7 d; 98.9 % biodegradation after 28 d) at an initial test item concentration of 55 mg test mat./L (20 mg TOC/L). Sampling was performed on day 0 and after 4, 7, 11, 14, 21, and 28 days (Elementis, 2005a). The 10 d  window criterion was passed, although this criterion should not be applied to TEA-Esterquats.

A further test according to OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test) with TEA-Esterquat partially unsaturated resulted in 78 % degradation after 28 days, fulfilling the 10 d criterion at a test item concentration of 17.1 mg test mat./L (10 mg C/L) (Kao, 1997a).

TEA-Esterquat partially unsaturated proved to be readily biodegradable in further studies according toOECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test). Biodegradation from 75 % to 67.2% was observed (Clariant, 2005; Elementis, 2005b; Henkel, 1998 and Undesa, 2005).

The ready biodegradation of partially unsaturated TEA-Esterquat was also investigated according to OECD Guideline 301 D and EU-Method C.4 -E over a period of 28 days and using domestic sewage as inoculum. The biodegradation rate was determined by measurement of oxygen consumption. The test item proved to be readily biodegradable and fulfilling the 14-d window criterion. The functional control reached the pass level >60% after 14 d. In the toxicity control containing both test and reference item >25% biodegradation based on oxygen consumption occurred within 14 d thus indicating that the test item was not inhibitory at the concentration tested (Evonik Goldschmidt, 2005b).

Several further studies were performed according to OECD Guideline 301D. Biodegradation was between 74 and 99% (O2consumption) (Kao (1986), Kao (1990a, b, c), Kao (1992)and Henkel (1999).

Two studies according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)) are available for partially unsaturated TEA-Esterquat as well as one study according to OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test) showed ready biodegradability. Biodegradation was 67% - 78% O2consumption for the MITI (I) tests (Evonik, 1992a and b) and 79 % O2consumption for the Manometric respirometry test (Henkel, 1995).

These results are in line with the study conducted with the read across substances TEA-Esterquat, oleic acid-based and TEA-Esterquat, fully saturated.

TEA-Esterquat, oleic acid-based was studied according to OEC D 301 B(Ready Biodegradability: CO2 Evolution Test)resulting in a % degradation of 116% in 28 days. The 10-day criterion was passed. Degradation values in excess of 100 % were considered to be due to sampling/analytical variation (Kao 2005; see Table 12).

TEA-Esterquat fully saturated proved to be readily biodegradable (65-66 % after 28 d). TEA-Esterquats are - as UVBC substances - mixtures of structurally similar chemicals. To interpret the results of a test with a mixture of structurally similar chemicals in a study conducted according to OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test; 1992) the 10 d criterion should not be applied.

The arithmetic mean biodegradability resulting from the % biodegradation of these most reliable studies is 80.2% in 28 days. Further reliable studies on readily biodegradability are available. The arithmetic mean of the biodegradation of all reliable studies is 78.4 % in 28 days. There are 2 reliable studies and one short abstract indicating no ready biodegradability, but inherent biodegradation for partially unsaturatedTEA-Esterquat (Evonik, 1993a/1994a; Henkel, 1993 and Evonik (1991)). However there is strong evidence, that partially unsaturated TEA-Esterquat is readily biodegradable.

Anaerobic biodegradation

Under anaerobic conditions partially unsaturated TEA-Esterquat was biodegraded in a test according to ECETOC Anaerobic Biodegradation (Technical Report No. 28) with activated sludge from a sewage treatment plant as inoculum. The test material attained 76% degradation after 56 days and therefore can be considered as biodegradable under anaerobic conditions (Kao, 1991a).