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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

In conclusion, the evaluation of the biodegradability of the five short chain ethylene glycols can be derived from numerous different studies. Summarizing all available data it can be concluded that the diethylene glycol is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

Several results on the ready biodegradability of the diethylene glycol are available. According to the available study reports, the substance fulfils the ready biodegradability criteria within the 28-d test period; however, the 10-day window criterion is failed in all of the available studies (301A BASF AG 1995, 1994, 301B BASF AG, 1995). DEG can be assessed as „biodegradable“ or „readily biodegradable, but failing the 10-d window“.

In addition to this information, the biodegradability of diethylene glycol is assessed in the read-across approach of 'ethylene glycol and higher glycols' (mono-, di-, tri-, tetra- and pentaethylene glycol). Within this read-across, all evidence indicates that the ethylene glycols are readily biodegradable. In case of mono-ethylene glycol (EG) a very rapid biodegradation was detected in the DOC Die Away Test according to OECD 301A (BASF AG, 1996). After 10 days > 90 % degradation of ethylene glycol was determined. The time window of the degradation phase is approx. 3 days.

In a MITI-I test (similar to OECD 301 C) the substance was degraded between 83 and 96% in 14 days of exposure (based on oxygen consumption, BOD/ThOD; MITI, 1988). A mixture of sewage, soil and natural water was used as inoculum. The validity criteria of the OECD guideline 301C were met. In the test study conducted according to OECD 301A tetra-EG was degraded within a time window of approx. 9 days (BASF, 1995).

Additionally, the inherent biodegradability of DEG is supported by a OECD 302C study (NITE, 2017).

It should also be considered that diethylene glycol is also used as a reference substance in biodegradability screening tests.

In conclusion, the evaluation of the biodegradability of the five short chain ethylene glycols can be derived from numerous different studies. Summarizing all available data it can be concluded that the complete members of the group including the diethylene glycol are readily biodegradable.