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biodegradation in soil: simulation testing
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance is readily biodegradable
Justification for type of information:
Two ready biodegradation studies (OECD 301D) have been performed on the registered substance (active substance: in a solid state). In these studies, a total of 35% and 45% degradation were reached respectively. These results correspond well with a predicted total mineralisation of the xylitol and anhydro-xylitol fractions. Nevertheless, employing the low inoculum concentration required to meet OECD 301D guideline recommendations, the bacteria may not have had the time to adapt to the larger constituents of the mixture during the timeframe of this study. From the previous information and the BIOWIN prediction of biodegradation of the different components of the registered substance, we would expect Xylitol, anhydro-xylitol and xylityl monoglucoside to be biodegraded in a ready test, at least when tested individually. It is recognised that "mixtures" containing a homologous series of constituents may take longer to biodegrade than single substances (as mentioned in the decision scheme of the CLP guidance (20135)). This is due to the increased lag time as the competent degraders move from one available food source to another.  Then two additional ready biodegradability tests were performed with the registered substance in water (corresponding to the commercial product); this corresponds to the physical state (liquid form) in which the substance will end up in the environment. In the first assay, the batch tested (83.97% dry matter) reached 69-73% in 28 days (10 day window reached) according to the OECD test n° 301F.
In the second assay (performed according to OECD test n° 301D), the commercial product reached 65 and 63% biodegradation with two types of inoculum (sludge from STP and river water, respectively) in 28 days and 68% biodegradation in 60 days (with river water as inoculum). As the registered substance is a multi-constituent substance in homologous series, the 10 days-window does not need to be satisfied to be "readily biodegradable" (guidance on the application of the CLP criteria, version 5.0: II.2.1.2, page 564). So the registered substance is considered "readily biodegradable".

Furthermore, based on the koc value (< 1) and the water solubility value, the registered substance will be found mostly in the aquatic compartment.

Data source

Materials and methods

Results and discussion

Applicant's summary and conclusion