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Biodegradation in water: Screening


Key Study:


In an OECD Guideline 301B study, conducted according to GLP, 5,5'-Dithiodi-1,3,4-thiadiazole-2(3H)-thione achieved 0% biodegradation after 28 days and is considered not readily biodegradable (Envigo Research Limited, 2016).


 


Biodegradation in water and sediment: simulation tests


Data waiving:


According to columns 1 and 2 of Annex IX of REACH regulation EC 1907/2006, biotic degradation testing in water shall be proposed by the registrant to investigate further the degradation of the substance and its degradation products.


A well-documented and reliable QSAR approach was adopted in order to evaluate the biotic degradation potential of the parent substance and its degradation products. The estimated biowin screening values indicate that 12 of the 18 degradation products do not fulfill the P criteria. In addition, the test substance and all the identified degradation products had estimated n-octanol partition coefficient and BCF values lower than the cut-off values, which indicate that none of them is B, nor vB. According to the PBT/vPvB assessment, the substance and its identified degradation products are therefore not considered PBT/vPvB.


In addition, according to the chemical risk assessment, the risks for water, sediment and soil compartments are considered all acceptable (all RCR are below 1 in all exposure scenarios). Therefore, the CSA does not indicate the need to investigate further hazards and risks for water, sediment and soil compartments, nor that further degradation testing is necessary in water, sediment soil compartments.


In conclusion, the study is therefore waived in compliance with column 2 of annexes IX and X of REACh regulation EC 1907/2006.