Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Fiel (2009) is a ready biodegradability manometric respiration test on polysulfides, di-tert-dodecyl, following OECD guideline 301F. This is a GLP compliant, aerobic, activated sludge study, though it did not fulfill the validity criteria because the oxygen demand of the inoculum control (medium and inoculum) was not greater than 60 mg O2/L within the 28 days as required. The study is considered reliable and suitable for use for this endpoint. Polysulfides, di-tert-dodecyl is not readily biodegradable, with 0% degradation after 28 days.

Therefore additional tests are required in order to better characterize behaviour and biodegradation profile.

Based on the intrinsic properties of the registered substance, it is expected to mainly sorb to sediment particles and will not persist in water column. Therefore simulation test has been proposed for sediment.

Biodegradation of tert-dodecyl polysulfides in freshwater sediments has been evaluated through an OECD TG 308 compliant study. Two water/sediment systems with duly characterised different properties were used ("SL" is OC poor, "SW" is OC rich).

The 2 water/sediment systems were incubated during 98 days in the dark at 20°C. Periodically, samples were removed in duplicates in order to measure concentration of TPS 32 in each phase.

It was shown that the substance migrates rapidly from water to sediment. Dissipation half-life TD50 in water was 6.4 days in "SL" water/sediment system and 6.6 days in "SW".

It was further shown that, after an increase of its concentration in the sediment phase, resulting from the partitioning (in agreement with the high Koc), the concentration decreased from 28 days onwards in both sediments. A DT50 could be calculated as being = 180 days in "SL" and 158 days in "SW" sediment, 169 days on the average.

According to this result, TPS 32 can be considered as persistent P (half-life in freshwater sediment > 120 days) but not very persistent vP (half-life in freshwater sediment < 180 days) in the environment.