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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
Additional information is available in the endpoint summaries and the read-across justification (see section 13).
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Parameter:
% degradation (DOC removal)
Value:
>= 90 - <= 100
Sampling time:
20 d
Remarks on result:
other: test result from RA Source CAS 112-60-7 (BASF, 1995)
Parameter:
% degradation (DOC removal)
Value:
>= 90 - <= 100
Sampling time:
10 d
Remarks on result:
other: test result from RA Source CAS 107-21-1 (BASF, 1996)
Parameter:
% degradation (DOC removal)
Value:
>= 90 - <= 100
Sampling time:
28 d
Remarks on result:
other: test result from RA Source CAS 111-46-6 (BASF, 1995)
Parameter:
% degradation (CO2 evolution)
Value:
>= 70 - <= 80
Sampling time:
28 d
Remarks on result:
other: test result from RA Source CAS 111-46-6 (BASF, 1995)
Parameter:
% degradation (O2 consumption)
Value:
>= 25 - <= 92
Sampling time:
28 d
Remarks on result:
other: test result from RA Source CAS 112-27-6 (NITE, 1992)

Description of key information

Readily biodegradable (according to OECD criteria).

Key value for chemical safety assessment

Additional information

The biodegradability of the test substance is assessed in a weight-of-evidence approach. Data from the two main constituents triethyleneglycol (CAS 112-27-6) and tetraethyleneglycol (CAS 112-60-7) of the test substance are available. Furthermore, data from the following comparable glycols is available: ethane-1.2 -diol (CAS 107-21-1) and 2,2'-oxydiethanol (CAS 111-46-6).

For main constituent triethyleneglycol, the biodegradation potential of the substance in water was determined in a screening study according to OECD TG 301C (Modified MITI Test) (NITE, 1992). Although no detailed test report is available, all tests from the Japanese Authorities are performed according to OECD guidelines and GLP. In this study, 100 mg/L test substance was inoculated with activated sludge for 28 days under aerobic conditions. During the incubation period the biological oxygen demand (BOD) was measured and biodegradation expressed as percentage of the theoretical uptake (ThOD). After the 28-day incubation periodbetween 25% and 92% degradationof the test substance was observed. The results indicate that the test substance is readily biodegradable.

For main constituent tetraethyleneglycol, the biodegradation potential in water was determined in a screening study according to OECD TG 301A (DOC Die Away Test) and in compliance with GLP criteria (BASF, 1995). In this study, 20 mg/L test substance (expressed as DOC) was inoculated with non-adapted activated sludge from a predominantly domestic sewage treatment plant for 20 days under aerobic conditions. After the 20-day incubation period the substance was biodegraded almost completely (≥ 90% - ≤ 100%). The 10-day window criterion was met. The study included a blank control, an inhibition control, an abiotic control and a reference substance. Based on the results of the appropriate controls, the test was considered valid. Based on the findings, the test substance is classified as readily biodegradable.

Other glycols that belong to the same category show similar results. In case of 2,2'-oxydiethanol, testing was performed according to OECD 301A and OECD 301B. In the DOC Die Away Test according to OECD 301A that was in compliance with GLP criteria, the substance biodegraded for 90 - 100% based on DOC removal after 28-days incubation, but did not fulfill the 10-day window (BASF, 1995). In the CO2 Evolution Test according to OECD 301B that was in compliance with GLP criteria, the substance biodegraded for 70 - 80% based on CO2 evolution after 28-day incubation. Overall, the substance can classified as readily biodegradable.

In case of ethane-1.2 -diol, very rapid biodegradation was detected in the DOC Die Away Test according to OECD 301A that was in compliance with GLP criteria (BASF, 1996). The time window of the degradation phase was approx. 3 days.

Summarising all available data on these glycols, it can be concluded that they all are readily biodegradable. Taking all data into account, the test substance Reaction mass of 2,2'-(ethylenedioxy)diethanol and 3,6,9-trioxaundecane-1,11-diol of is assessed to be readily biodegradable.