2,2-Difluoroethyl Acetate

Biodegradation in soil

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in soil: simulation testing

Data waiving:

other justification

Justification for data waiving:

other:

Transformation products:

not measured

Remarks:

Not applicable in the case of a data waiving

Description of key information

Data waiving (other justification):

Simulation degradation studies aim at (i) identifying/quantifying degradation products, and (ii) investigating the degradation rate constants and half-lives of the parent subtance and, if applicable of the degradation products.

In the case of 2,2-Difluoroethyl acetate (DFEA):

- With respect to (i), the degradation products have already been identified/quantified in the available OECD 301 C study (see IUCLID section 5.2.1). In the three replicates of the 'DFEA + sludge' treatment, 2,2-Difluoroethanol was formed at 56 to 62% and Difluoroacetic acid was formed at 29 to 31%. Acetic acid is another expected product in the theoretical transformation pathway, but it was not detected in this study likely because it is readily biodegradable. The total formation rate of transformation products (2,2-difluoroethanol and difluoroacetic acid) was ~90%; the rest was supposed to have been volatilized as the test substance or 2,2-difluoroethanol during the 28-day exposure.

- With respect to (ii), the same OECD 301C study has demonstrated a complete disappearance of DFEA. Indeed, based on measurements of residual amounts at the end of the 28-day study, the disappearance rates were calculated to be > 99% for the three replicates of the 'DFEA + sludge' treatment. These analytical measurements gave already robust indications on the mother substance half-life. By the way, determining the half-lives of the degradation products would have no added value considering that all of them have been concluded to be not PBT and not vP/vB (see IUCLID section 2.3).

- In addition, the analytical monitoring performed during the chronic toxicity study on earthworms (see IUCLID section 6.3.1) has demonstrated that it was very difficult, if not impossible, to maintain exposure to DFEA in soil substrate due to its volatility potential. From this, it can be concluded that the biodegradation simulation test in soil will be extremely challenging, if not technically unfeasible.

- Finally, a log Koc > 4 is mentioned in ECHA Guidance R.7b (section R.7.9.4.3, v4.0, June 2017) as an indicator that simulation test in soil may be warranted. The Log Koc of DFEA is clearly below this threshold (see IUCLID section 5.4.1).

Based on the above pool of evidence, it is deemed irrelevant to perfom a biodegradation simulation test in soil with 2,2-Difluoroethyl acetate.