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Adsorption / desorption

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Description of key information


Key value for chemical safety assessment

Koc at 20 °C:
116 000

Additional information

According to the REACH Regulation (EC n. 1907/2006), Annex VIII, Column 2, the study does not need to be conducted when the physicochemical properties the substance can be expected to have a low potential for adsorption (e.g. the substance has a low octanol water partition coefficient) or the substance and its relevant degradation products decompose rapidly . Even though the predicted log Kow value for this substance is 6.13, dioctyl phosphate is ready biodegradable (90 % of biodegradation in 28 days) and so the second waiving criteria is fulfilled.

A predicted value for partition coefficient organic carbon-water was calculated by EUSES 2.1.2 Koc = 1.16*10^5 l/kg. This value was used by CHESAR for chemical safety assessment. As reported in ECHA Guidance Chapter R.7b: in general substances with a Koc <500 – 1000 l/kg are not likely sorbed to sediment (SETAC 1993) and log Koc or log Kow of ≥ 3 is used as a trigger value for sediment effects assessment although other considerations or combinations of triggers might be important as well (e.g. binding to sediment particles that is not Kow/Koc driven, but where for instance the distribution coefficient Kd is important, persistence in the sediment compartment). For Dioctyl phosphonate the predicted Koc value 1.16 *10^5 l/kg equivalent to log Koc = 5.06 raises no concern for adsorption/desorption because the substance is ready-biodegradable.