Registration Dossier

Environmental fate & pathways

Adsorption / desorption

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

Two experimental data are available for adsorption of DEHP on particles.

First in freshwater, Williams et al. 1995 showed in a US EPA study a Koc= 482000. This value is in the same range with EUSES model default value which indicates a Koc 589,000 l/kg (based on log Kow = 7). The PCKOC model (Syracuse model, Meylan 1992) based on structure analysis estimates Koc to 165,000. This value seems to be more in agreement with the majority of experimental values than the EUSES estimate and is therefore used in the EUSES calculation.

Second in natural seawater, Sullivan et al. 1982 studied the adsorption by varying the amounts and types of solid adsorbent at various DEHP concentration. Thus an average corrected partition coefficient are 130000  to 1270000 depending on minerals.

Furthermore, Sullivan et. al. 1982 reported Koc-values from a marine sediment/water system of 794,000 to 1,260,000.

Key value for chemical safety assessment

Additional information

As previously reported in the Risk Assessement Report 2008, with a log Kow of about 7.5 DEHP is expected to be strongly adsorbed to organic matter. In the environment DEHP therefore is expected to be found in the solid organic phase. Due to the high log Kow value and low water solubility, the equilibrium for DEHP will be in favour of particles. This is further enhanced by bonding (van der Waahls type bonds) between mineral surfaces and the benzene rings and carbonyl groups of the phthalate ester (ECETOC 1985). Thus the transport of DEHP in aquatic environments will to a high degree depend on the transport of particles. This also indicates that the mobility of DEHP in soil would be low, but since DEHP is adsorbed to for instance organic acids (especially humic substances) and to non-humic matter such as proteins, this may not always be the case. Adsorption to colloidal matter may also enhance subsurface transport of contaminants in soils through cracks and micropores.