Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

The test item is considered as being readily biodegradable.

Testing of hydrolysis and adsorption/desorption behaviour was not conducted because the test item is readily biodegradable and has a LogKow <3.

Additional information

Biodegradability

The biodegradability of Sophorolipids was investigated in three guideline studies.

a.OECD guideline 301F

The biodegradation of the test substance was investigated over a 28 day period in a manometric Respirometry Test according to OECD Guideline 301 F (1992). The test medium was inoculated with microorganisms from a digester of a sewage treatment plant mainly fed with municipal wastewater.

The rate of degradation was monitored by measuring the quantity of oxygen required to maintain a constant gas volume in the respirometer flasks over 28 days.

Sodium benzoate was used as a degradable reference substance at a concentration of 100 mg/L, along with a toxicity control at 100 mg/L test substance and 100 mg/L sodium benzoate. The biodegradation of the test substance was found to be at mean 69 % with a standard deviation of 0.8 % for a concentration of 100 mg test substance/L and at mean 85 % with a standard deviation of 5.4 % for a concentration of 60 mg test item/L. For a concentration of 100 mg test substance/L biodegradation within the 10-day-window was found to be 61 %.

For a concentration of 60 mg test substance/L biodegradation within the 10-day-window was found to be 75 %.

The degradation of of the reference substance sodium benzoate had reached 83 % within the first 14 days.

According to the guideline, the test item is considered as beingreadily biodegradableunder the test conditions.

b. OECD guideline 311

The anaerobic biodegradation of the test substance was determined in a test according to OECD guideline 311 (2006) and EN ISO 11734 (1998). Biodegradation was monitored by continuous measurement of the gas developed until the end of the test. Anaerobic sludge was used as inoculum.

After 61 days a degradation of 110.7 % was observed. The degradation exceeding 100 % might be explained by the following: In the test flasks bacterial growth was enhanced by the well biodegradable test substance. After digestion of the test substance the biomass started self-digestion. Self-digestion of the previously increased biomass in the test flasks might very well be higher than the control flasks.

Except for the degradation of the positive control, the validity criteria were met. As the test item was readily and completely biodegradable under test conditions, this deviation from the guideline can be stated as uncritical.

Therefore, the test item is stated to bebiodegradable under anaerobic conditions.

c. Read-across study, OECD 301C test

The biodegradation of the test substance was determined in an OECD 301C test (modified MITI test). The degradation was measured by means of oxygen uptake. After 28 days more than 99 % of the test substance was degraded, meeting the 10 day window requirement. Under the conditions of the test the test substance wasreadily biodegradable.

Discussion biodegradability:

The test item Sophorolipids was readily biodegradable in both an OECD guideline 301F and an OECD guideline 311 test.

A supporting study based on a read-across approach is available which gave comparable results.

Hydrolysis

Testing is not required. According to the REACH Regulation, Annex VIII, column 2 the study does not need to be conducted if the substance is readily biodegradable. Handbook data describe that the test substance hydrolyses under to both acid and alkaline conditions. Transformation products are sophorose and deacetyled free acids.

Adsorption / desorption

An adsorption/desorption study was not conducted due to LogKow < 3 and ready biodegradability of the test item. Instead, Koc was calculated with EUSES 2.1.2 using the following parameters:

Molecular weight: 623 g/mol (molecular weight of main constituent based on oleic acid as major fatty acid moiety for the acidic form with the

representative molecular formula of C 30 H 54 O 13)

Melting point: 150 °C

Vapour pressure: minimum (1E-06)

Water solubility: 0.2 g/L (according to critical micelle concentration (CMC))

LogKow: 2.4, worst case value calculated from measurement of CMC and solubility in octanol

Chemical class: default QSAR

Result Koc: 185