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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Determination of the ready biodegradability and the inherent biodegradability of TK 12146, ACCELERATOR DY 9577, in an aerobic aqueous medium.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

The ready biodegradability test was peformed to evaluate a non-volatile test substance for its ready biodegradability in an aerobic aqueous medium with microbial activity introduced by inoculation of activated sludge.

TK 12146, ACCELERATOR DY 9577 was tested for its ready biodegradability in the Carbon Dioxide (CO2) Evolution test (Modified Sturm tst) at ca. 57 mg per 2 litres, corresponding to ca. 12 mg TC/l.

The study procedure was based on EEC directive 92/69, C.4 -C, December 1992, and OECD guideline N° 301 B July 17, 1992.

The Total Carbon content (TC) of TK 12146 was determined to be 42.2%. The Theorical CO2 production (ThCO2) of TK 12146 was calculated to be 1.547 mg CO2/mg.

The relative degradation values calculated from the measurments performed during the test period revealed no significant degradation of TK 12146, in bottle A (SIGNIFICANT >10%), and 25% degradation in bottle B.

In the control toxicity TK 12146 was found to have no inhibiting effect on microbial activety.

Since all acceptability criteria prescribed by protocol were met, this study was considered to be valid.

In conclusion, TK 12146 was not readily biodegradable under the conditions of the modified Sturm test presently performed.

The inherent biodegradability study was performed to assess the inherent biodegradability of the test item in an aerobic aqueous medium. The method followed are designed to be compatible with the OECD Guidelines for Testing of Chemicals (1981) No. 302C Inherent Biodegradability; Modified MITI (II) Test and in the MITI Gazette, 19 July 1974 under paragraph 7-1: Method for Testing the Biodegradability of Chemical Substances by Micro-organisms.

 

The test item was prepared as an aqueous dispersion at a concentration of 30 mg/L, inoculated with micro-organisms from a laboratory culture originating from 10 different sites throughout the UK and incubated in diffuse light at 25 °C for 28 days. The degradation of the test item was assessed by the measurements of oxygen consumption on Days 0 and 28. Control solutions with inoculum and the reference item, aniline, were used for validation purposes.

The test item attained 38%, 48% and 40% degradation with a mean of 42% degradation calculated from oxygen consumption values after 28 days.

 

The test item can therefore be considered to show evidence for inherent, primary biodegradation under the terms and conditions of OECD Guideline No 302C.