Reaction mass of chlorodifluoroacetic acid and trifluoroacetic acid

Biodegradation in water: screening tests

Description of key information

Based on experimental data on each constituent, the reaction mass is considered as not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

No data is available on the reaction mass of chlorodifluoroacetic acid and trifluoroacetic acid. Reliable data are available on the constituents of the reaction mass as described below:

The inherent biodegradation test of CDFA was performed according to the Procedure 302C of the ‘Guidelines for Testing of Chemicals’ of the OECD: “Inherent Biodegradability: Modified MITI Test (II)” (1981). The inherent biodegradability of Chlorodifluoroacetic acid was determined in a 28-day Biochemical Oxygen Demand (BOD) test and the analysis of residual chemical of CDFA in BOD bottles in an aerobic, aqueous medium.

During the test, the temperature was kept at (25±1)°C. The test was valid because the level of biodegradation of the reference substance sodium benzoate was 57.4% (≥40%) after 7 days, and 69.6% (≥65%) after 14 days.

At 28 day, residue concentration of the test substance CDFA in abiotic and test bottles was 292mg/L and 243 mg/L, respectively. Degradation rate of the test substance was 16.9% in the “test” vessel during the testing period. The BOD results showed that biodegradation of CDFA was 15.9% after 28 days. Therefore, Chlorodifluoroacetic acid has no inherent biodegradability under these test conditions and can be considered as not readily biodegradable.

The ready biodegradability of TFA was studied on the sodium salt of this acid (i.e. sodium trifluoroacetate, CAS RN 2923-16-2). The read-across approach is relevant for the assessment of the biodegradability profile as in the environment, this acid is neutralised by cations in presence, including Na+. Trifluoroacetic acid and sodium trifluoroacetate are both very soluble in water. Therefore, the biodegradability of sodium trifluoroacetate determined in the closed bottle test is relevant for TFA.

The study has been performed according to slightly modified OECD 301D, EEC 1984 Part C., and ISO Test Guidelines. Microorganisms (Secondary activated sludge at concentration of 2 mg DW/L, obtained from the WWTP Nieuwgraaf in Duiven: plant treating predominantly domestic wastewater) are inoculated into a chemically defined liquid medium containing the test substance (Trifluoroacetic acid, sodium salt at 20 mg/L) or the reference substance (Acetic acid, sodium salt or Sodium acetate at 6.7 mg/L) under aerobic conditions for a period of 77 days; the test was prolonged because the pass level was not reached at day 28. Use was made of 10 bottles containing only inoculum, 10 bottles containing test substance and inoculum, and 10 bottles containing sodium acetate and inoculum. The temperature and pH was measured, temperatures ranged from 23 to 25°C and the pH of the media was 7.0 and 7.1 at the start and the end of the test, respectively. Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration using an oxygen electrode at day 0, 7, 14, 21, 28, 42 and 77 days. Parameter followed for degradation estimation was O2 consumption.

The percentages biodegradation of Trifluoroacetic acid, sodium salt in the closed bottle test were 0% for 0, 7, 21, 28 and 77 days and 8% for 14 and 42 days. However, the results of the prolonged test are invalid because the differences of extremes of replicate values of the removal of the test chemical at 77 days are 95% ( > 20%). Moreover, the result of 8% degradation at day 42 is probably an artefact due to the 40 % coefficient of variation between duplicate values of the control.

The percentages biodegradation of sodium acetate in the closed bottle test were 0, 83, 92, 85 and 83% for 0, 7, 14, 21 and 28 days respectively. The test substance caused no reduction in the endogenous respiration. Therefore, Trifluoroacetic acid, sodium salt is considered to be non-inhibitory to the inoculum. Trifluoroacetic acid, sodium salt was not biodegraded in the closed bottle test (28 days) and should therefore not be classified as readily biodegradable.

Consequently, considering that both constituents of the reaction mass are not readily biodegradable, the reaction mass of chlorodifluoroacetic acid and trifluoroacetic acid is not readily biodegradable.