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Environmental fate & pathways

Adsorption / desorption

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Description of key information

The soil adsorption coefficient of sulfonic acids, C10-21-alkane, Ph esters was calculated yielding a logKoc range between 4.7 and 9.3 (Currenta, 2010). 
According to Swann et al. (1983), all components of sulfonic acids, C10-21-alkane, Ph esters are assumed to have a high potential to sorb on soil and sediment.

Key value for chemical safety assessment

Koc at 20 °C:
50 120

Additional information

In the absence of any measured Koc values for sulfonic acids, C10-21-alkane, Ph esters, estimated values were used to assess the environmental fate of the test item. According to the classification of Swann et al. (1983), the substance has a high potential to sorb on soil. As this is the most stringent judgement with respect to the environmental fate of a substance, it can be taken as worst case assumption for the description of the environmental fate of the test item. Estimations are only appropriate for non-ionisable and/ or non-surface active substances and the applied estimation method must be proven to be valid for the type of chemical under consideration. All requirements are fulfilled for the test item.

Koc values are neither used in the scope of classification and labelling, nor for the PBT assessment. However, it is a key property to describe the environmental fate of the substance in the scope of the CSA. According to the Guidance Document R.7a (ECHA, 2008), an estimated value will be sufficient if it is indicated that the adsorption coefficient will not affect the CSA, i.e. no risk is identified for the sediment/soil compartments. Based on a qualitative assessment of substance properties (no acute aquatic effects, only a low potential for bioaccumulation, the potential to be biotically degraded), no risk for the sediment/ soil compartment is assumed supporting the use of an estimated Koc value.

Koc values provide information about the potential of the test item to sorb on suspended matter in sewage treatment plants as well as in receiving waters, but also on the potential to desorb from the solid phase being available for the uptake into sediment or soil organisms. Concluding, higher Koc values suggest a greater potential to sorb on suspended matter strongly influencing concentrations in the respective phases, whereas low Koc values imply a better desorption from soil or sediment suggesting a higher risk for soil and sediment organisms due to higher pore water concentrations. As sulfonic acids, C10-21-alkane, Ph esters is characterized by a Koc range rather than a single value, the selection of the lower as well as the upper limit should carefully be evaluated. The lower limits of the three calculated logKoc values range from logKoc 4.5 to 4.8 showing only a minor difference between the three methods used not significantly influencing the further assessment. But the upper limits range from logKoc 7.8 to 9.3 showing a difference greater than one order of magnitude. Therefore, to adequately assess the sorption potential of the test item, the highest value was chosen for the further assessment to avoid the underestimation of the sorption potential of the test item.

Concluding, the logKoc range of 4.7 to 9.3, calculated according to Sabljic (1995), was chosen for the further the further assessment.

[LogKoc: 4.7]