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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

p-TFMA ahs to be considered as not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

A report (Hoechst, 1996) on a biodegradation test concludes about readily biodegradation potential for pTFMA.

This report was discussed with the study director who provided additional information about nitrification potential and the calculation of the theoretical oxygen demand.

The summary of the disregarded study is the following:

In a study (Hoechst, 1996), the biodegradability of p-TFMA was evaluated according to OECD 301F guideline under GLP.

The biodegradation of the test item was followed during 28 days, at a concentration of 71.5 mg/L, using 30 mg/L of inoculum from Municipal sewage treatment plant.

After 28 days, the test item was found readily biodegradable (reaching the 10-day window).

However this test is not fully valid, because there are some deficiencies in regards the recommendations in the OECD 301 guideline:no pH measurements (it should be adjusted to 7.4 +/- 0.2), no abiotic sterile control, no toxicity control, no details on analytical method. In addition a replicate in the control had to be disregarded but this is not discussed in the report. Finally the calculation of the theoretical demand in oxygen is not in line with the OECD recommendation and significant differences in the final result may come from this different calculation.

In the end the nitrification of the test item was not taken into account in this study. Based on calculation described inAnnex IV.2 of OECD 301 guideline, the percentage of biodegradation expected in this study, would have been47.5 to 57.3% after 28 days.

In these conditions p-TFMA would have been considered as not readily biodegradable.

For all the above deficiencies / uncertainties in the study and despite the additional information provided by the study director, the data had to be unvalidated for the following reasons:

- the test is not fully valid in regards to OECD 301 recommendations,

- the report does not contain any details on the preparation of the inoculum, analytical method.

- "technical effects" that conducted to invalidate a replicate in the control is not described precisely,

- the theoretical oxygen demand is not calculated as recommended in the OECD guideline (and the calculation according to the OECD301Fguideline would have lead to higher values, then the substance may have had a lower potential for biodegradation)

- there is no evidence in the literature to show that a nitrification process is not expected for these compounds

- other similar compounds have been tested and found "non readily biodegradable": o-TFMA, 2,6 dichloro-pTFMA, 4 fluoroaniline, trifluoromethylbenzene

- other similar compounds are found "non readily biodegradable" with structure activity models: pTFMA, 2,4 difluoroaniline, 2 Fluoroaniline, 4- Fluoroaniline, 3,5 difhuoroaniline.

 

Considering the actual deficiencies in the study and the result of the literature search on the biodegradation potential for similar fluorinated compounds it is proposed to keep the "R53" classification and consider the substance as "non readily biodegradable”.

 

The result of QSAR, considering as key study concludes about "non readily biodegradable" substance with all relevant prediction models (BIOWIN v4.10 (2010)).