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Environmental fate & pathways

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Trifluoroacetic acid anhydride (TFAH) reacts violently with water and is instantaneously degraded in trifluoroacetic acid (TFA) which is the relevant substance for risk assessment and classification & labelling purposes. TFA is a strong organic acid with a pKa of 0.43 so it will be under dissociated form in all environmental compartments.

The possible reductive and oxidative degradation of TFA has been investigated by photocatalytic experiments conducted with aqueous suspensions of semiconducting materials. TFA proved to be a rather inert compound under practically all conditions and from these experiments it can be postulated that direct and indirect photolysis are not expected to be an important transformation process for TFA in water and air. No standard test is available to assess the decomposition or degradation of TFA by reaction with water. However the hydrolysis potential of TFA is expected to be very low based on its chemical structure, the preliminary results of non standard tests and the concentrations stability observed during analytical measurements of standard biodegradation and ecotox tests. The results of standard respiration tests with activated sludge showed that TFA is not readily nor inherently biodegradable.

In conclusion, TFA was found to be highly resistant to abiotic and biotic degradation and, coupled with its extreme chemical stability, these results suggest a very long lifetime for TFA in the environment.

No bioaccumulation studies obtained from established experimental protocols are available for TFA. The substance is expected to have a low potential for bioaccumulation.

However, based on a weight of evidence approach, results indicate a low level of incorporation of TFA by natural microbial communities and thus their potential to serve as a point for TFA to enter into the food web. Overall incorporation of radioactive TFA in aquatic organisms spanning a range of trophic levels (microbial communities, oligochaetes, macroinvertebrates, Callitriche sp., Lemna sp., and Impatiens capensis) was very low (low ppb range for microbial communities and low ppm range for oligochaetes and jewelweed).

Based on a weight of evidence approach, the TFA-anion poorly adsorbs to the different soil components because after 16 hours of agitating in a soil/water system less than 3% of the initial amount of TFA had disappeared from the water phase. Due to the fact that less than 25% is adsorbed, no further testing is required by the OECD guidelines.