Alkenes, C15-18 α-, sulfurized

Biodegradation in water and sediment: simulation tests

Description of key information

Biodegradation in water: simulation test

In accordance with Column 2 Specific Rules for Adaptation from Column 1 under Annex IX, simulation testing on ultimate degradation in surface water does not need to be conducted if the substance is highly insoluble in water. Two water solubility studies have been conducted at two different laboratories. In both studies, it was not possible to determine the water solubility, as it was not analytically feasible. Use of QSARs on representative structures also indicates that the substance is insoluble. The OECD 309 TG specifies that selected concentrations for running this study should ideally be in the range of 0.001-0.1 mg/L. However, these concentrations cannot be achieved with this substance. Therefore, this substance is considered highly insoluble in water and this endpoint can be waived.

Biodegradation in sediment: simulation test

Under Section 2 of Annex XI, and with respect to Article 13(3), it is considered that it is not technically possible to run the simulation test. According to OECD 308, prior to running this study, it is necessary to know the solubility in water (according to OECD 305), the n-octanol/water partition coefficient (Kow) (according to OECD 107 or 117) and the adsorption coefficient (Koc) (according to OECD 106). However, the substance is highly insoluble in water, and its water solubility cannot be analytically determined with any level of accuracy or reliability. Therefore, it is not possible to meet the first of these abovementioned criteria. In consideration of the other relevant physico-chemical properties, the Log Kow has been determined to be >10, and no reference standard is currently available to allow a more precise determination. Equally, the Log Koc has been determined to be >5.63. As these values cannot be more accurately determined with current analytical capabilities, these pre-requisites for the OECD 308 are not met.

Furthermore, OECD 308 states that it is applicable to slightly volatile, non-volatile, soluble and poorly water-soluble compounds. The guidance does not include highly insoluble compounds within the scope of applicable substances. Therefore, it is considered that sediment simulation testing methods are not appropriate to this substance based on water solubility. In further consideration of the OECD 308 method, it should be noted that it does allow for the use of solvents for the addition of test substance into the system, which should not exceed 1% v/v. However, in an OECD 301B study, it was necessary to use a greater volume of solvent than this to obtain a meaningful test result. If a similar method were employed in a sediment simulation test, it would be necessary to use of solvents and dissolution substances at concentrations above those prescribed in OECD 308. Therefore, the use of solvents is not considered appropriate in this case. As such, it is considered that the study is not technically feasible.