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Environmental fate & pathways

Biodegradation in water: screening tests

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Link to relevant study record(s)

Description of key information

The key study for this endpoint clearly demonstrates the ready biodegradability of Docusate Sodium, according to the criteria for surfactants, as defined under 648/2004/EEC. The study was conducted according to ISO 14593 (equivalent to OECD 310). Docusate Sodium passed the test specific 60% criterion for ready biodegradation, as set by the above guidelines. Totally average 91% had been degraded after 28 days of incubation. Although the 10 day window criterion is not relevant for surfactants according to 648/2004/EEC, the 10 day window was met in this study.

These results are used as a read-across to the substance registered, which is the corresponding potassium salt of the substance.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The substance registered is an anionic surfactant and has the following physical-chemical characteristics, relevant for the selection of appropriate OECD test procedures to assess ready biodegradability.

Water solubility: 8.2 g/L.

Vapour Pressure: 1.63 10 -12Pa.

KOC: 952.3 L/kg.

Based on these values, Docusate Sodium can be considered water soluble, non-volatile and not strongly adsorptive. Four reliable studies are available for the assessment of ready biodegradability, based on testing requirements for anionic surfactants, according to Annex III of 648/2004/EEC .

The study of Cognis, Borowivcz 1998 (GLP) is considered the key study, since it is using analytical grade Docusate Sodium (98% pure). Furthermore, it applied test guideline ISO 14593, i.e. the reference method of 648/2004/EEC. ISO 14593 is equivalent to OECD 310, the most appropriate test design for anionic surfactants. The results of this study indicate that more than 90% of the test substance was degraded within 28 days, respectively. The results demonstrate that Docusate Sodium is readily biodegradable.

Three of the studies are considered supportive.

The study of Dow, Häner 2008 was conducted with analytical grade Docusate Sodium (98.5% pure, i.e., within its specification). Furthermore, it used a suitable method according to Directive 67/548/EEC Annex V, i.e., C.4 -D, equivalent to OECD 301 F. As a result 76% (ThOD) or 100% (DOC) were

degraded within 28 days, respectively. This finding supports the result of the key study, i.e., that Docusate Sodium is readily biodegradable, according to the criteria set by the above guideline.

Two other studies were conducted with formulations of Docusate Sodium containing 85 and 76.4% of it (Cognis, Richterich 2001a and Elementis, Brunswick-Titze 2003). Between 90 and 100% of the test item was degraded within 28 days, respectively.

 

In conclusion it can be stated that Docusate Sodium is readily biodegradable.

Two studies of the registered substance are available, but documentation is insufficient for a key study. However they support the conclusion that biodegradability results can be read across from the sodium salt.