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EC number: 246-770-3 | CAS number: 25265-71-8
Biodegradation in water: screening tests
Administrative data
Link to relevant study record(s)
Description of key information
Dipropylene glycol was found to be readily biodegradable after 28 days under aerobic conditions.
Key value for chemical safety assessment
- Biodegradation in water:
- readily biodegradable
Additional information
Under aerobic conditions 82% biodegradation was found in a ready biodegradability screening test, based on oxygen consumption, for 100 mg/l dipropylene glycol tested according to GLP compliant OECD Guideline 301F study (West et al., 2007). In an inherent biodegradability study (GLP compliant OECD Guideline 302A) 83.6% biodegradation was found for 18.5 mg/l dipropylene glycol (Sittingbourne Research Centre, 1994). The result of the readily biodegradability test will be used in the assessment.
In the study of West et al. (2007), 58.7 ± 1.3 % biodegradation based on O2 consumption was observed in the 10-day window, indicating that the 10-day window criterium of 60% ThOD removal for ready biodegradability was just not met. A previous study has shown that the various isomers and homologues typically comprising technical surfactant mixtures can be biodegraded preferentially and sequentially in the ready biodegradability test (Richter and Steber, 2001). In such cases, the extent of degradation occurring over the 10-d window represents the average rate of degradation for all components of the mixture and has little relevance for individual components. For this reason, a recent revision to Section 3: Degradation and Accumulation of the OECD guidelines has excluded the 10-d window criterion for ready biodegradability tests involving substances that occur as mixtures of isomers and/or homologues in their purest commercial form (OECD, 2006). In the present study, markedly different rates of biodegradation were observed among the discrete propylene glycol oligomers having one to four oxypropylene repeating units. Kawai (1987) also showed that biodegradation of dipropylene glycol involves preferential oxidation of the structural isomers having secondary alcohol groups. Thus, different rates of biodegradation could be expected for the distinct homologues and isomers comprising the propylene glycol substances, and the 10-d window criterion should not be applied in evaluating their ready biodegradability.
It is therefore concluded that dipropylene glycol can be regarded as ready biodegradable.
Significant biodegradation (>20%) was found in a screening test with natural seawater after 64 days (West et al., 2007).
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