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Diss Factsheets

Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Readily biodegradable: 85.6% (ThCO2) after 28 d (OECD 301 B) but failing 10-day window

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable but failing 10-day window

Additional information

The biodegradability of 6-methyl-2-oxoperhydropyrimidin-4-yl urea was tested in a GLP guideline study following the specifications given by OECD guideline 301 B. The study was conducted under aerobic conditions using domestic activated sludge as inoculum. During the incubation time of 28 days the degradation was followed by determining the CO2 production. A mean of 85.6% degradation was determined at test termination. Though the ultimate degradation rate was consistent in all test replicates the degradation kinetics differed between the replicates. Two of the three replicates showed a sigmoidal degradation curve whereas a lag phase was observed in the third replicate. Thus the ten day window criterion was not met by all replicates. The mean degradation rate was 56.2% of ThOC2 at the end of the 10-day window on day 16 of the incubation period (10-day window criterion: 60% of ThOC2). However after 28 days all replicates reached a homogenously high degradation level with a mean of 85.6% based on ThOC2. Thus the substance is assumed to be readily biodegradable.