Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

The test substance is a multiconstituent substance which has a very low water solubility (< 0.1 mg/L). For the purpose of the chemical safety assessment, the key water solubility value is determined to be 21 µg/L at 25°C. The value is the weighted average (using the % w/w of each constituent in the whole substance) of the individual water solubility values of each constituent. Further information on the determination of the key information for water solubility is available in the appropriate endpoint (4.8 Water solubility). Thus, the test substance has to be considered as a difficult substance to be tested particularly for achieving exposure concentration and for preparing representative media.

The hydrolysis study was not conducted due to the low solubility of the test substance in water and as the test substance was found to be readily biodegradable under enhanced test conditions. As the test substance is a multi-component substance and it is considered that sequential degradation is likely to be taking place, the ten-day window condition is waived and the pass level is applied at 28 days. Under standard test conditions, the biodegradation rate was 14% on Day 28. The poor solubility of the test substance may make its bioavailability very low, resulting in lower than expected biodegradation rate. In another screening test, experimental conditions were designed to improve the bioavailability of the test substance using non-biodegradable surfactants and/or silicon oil. Over 60% of biodegradation was thus achieved within 28 days. To conclude, the substance is considered as readily biodegradable.

An estimation of the adsorption coefficient Koc has been performed on 99422018 using the HPLC Method (OECD 121) and QSAR Estimations. The Log Koc values were high for all the three constituents (i.e. Log Koc > 4.0). A key value of 251,000 (log Koc = 5.4) was determined for the Koc of the test substance, which has to be considered as poorly mobile.