Calcium 1,4-bis(2-ethylhexyl) bis(2-sulphosuccinate)

Biodegradation in water: screening tests

Description of key information

The key study for this endpoint clearly demonstrates the ready biodegradability of the substance, according to the criteria for surfactants, as defined under 648/2004/EEC. The key study contributed to the EC surfactant ring-test (CO2 headspace) and was hence conducted according to ISO 14593 (equivalent to OECD 310). The substance passed the test specific 60% trigger for ready biodegradation, as set by the above guideline, since average 91.1% had been mineralized after 28 days of incubation. Three supportive studie showed average mineralization of 68%, 76% and 93% on day 28.

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

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

The substance 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: 8.17 g/L.

Vapour Pressure: 1.63 10 ^-12Pa.

K_OC: 952.3 L/kg.

Based on these values, the substance can be considered water soluble, non-volatile and not strongly adsorptive according to FAO mobility classification, respectively.

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. Of these, the study conducted by Borowicz (1998) was selected as the key study. Three of the studies were selected as supportive: One of them was conducted with analytical grade substance, the other two were conducted with formulated products.

Key study (test material = analytical grade substance):

The study of Cognis, Borowicz 1998 (GLP) is the key study. The work was conducted as a part of the EC Surfactant Biodegradation Ring-Test (CO2 Headspace). It used analytical grade of the substance (98% pure) and applied test guideline ISO 14593, i.e. the reference method of 648/2004/EEC for surfactants (CO2 headspace test). ISO 14593 is equivalent to OECD 310, the most appropriate test design for anionic surfactants (CO2 headspace). The results of this study show that average 91.1% of the test substance was minerlaized within 28 days, respectively (pass level is 60%). Hence, the substance is readily biodegradable.

Supporting studies (test material = analytical grade substance):

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 average 76% were mineralized within 28 days. Though the 10 -day window is not applicable as a criterion for the ready biodegradation of surfactants, according to 648/2004/EEC, the study reports that average 57.2% of the substance were mineralized by day 14, the end of the 10 -day window. This finding supports the result of the key study, i.e., that the substance is readily biodegradable, according to the criteria set by the above guideline. Though the study was conducted non-GLP, the work was conducted by a ISO/IEC 17025 certified laboratory. Hence the results are considered valid to support the finding of the key study.

Supporting studies (test material = formulated product of the substance): Two other studies were conducted with formulations containing 76.4% and 85% substance (Elementis, Brunswick-Titze 2003 and Cognis, Richterich 2001a, respectively). Between average 93% and 68% of the test item was mineralized within 28 days by activated sludge and effluent, respectively. The 10 -day window was met in both studies, although its not applicable as a criterion for the ready biodegradation of surfactants, according to 648/2004/EEC). Though the work of Richterich 2001a was conducted non-GLP, the study was conducted following appropriate industrial research standards to that the results are equally valid.

Based on key and supporting studies, it is concluded that the substance is readily biodegradable.

This conclusion is supported by findings of Cognis, Richterich 2001b, who reported primary biodegradation (64%) within 5 days of a 70% substance formulation exposed to a non-adapted, activated sludge.

Other available study results were non reliable to assess this endpoint, and were hence disregarded, for various reasons (sole or in combination):

1. The test materials contained up to 10% ethanol. Since ethanol is known to enhance biodegradation, the results of these studies might be false positive and are therefore not reliable.

2. The tests were conducted according to OECD 301 A and E, which are less suitable for the purpose or ready biodegradation assessment according to 648/2004/EEC, due to the physical-chemical properties of the substance, K_OC in particular.

3. Tests were conducted according to testing guidelines, which are not recommended by 648/2004/EEC for the assessment of ready biodegradation of surfactants.

4. Essential experimental details were not reported.

5. GLP was not applied.