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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Log Koc soil: 21.41
Log Koc sewage sludge: 23.21

Key value for chemical safety assessment

Koc at 20 °C:
2 570 395 782 768 864 788 480

Additional information

The phthalate esters are1,2-benzenedicarboxylic acids with side chain esters ranging in carbon chain length from C1 to C13.The US EPA High Production Volume (HPV) chemical challenge program has proposed grouping phthalate esters into a single category, divided into 3 sub-categories, this based on the structural similarities of the substances and their physicochemical and toxicological properties. These sub-categories are: low molecular weight phthalates, transitional phthalates, and high molecular weight phthalates. The high molecular weight phthalates are defined as being produced from alcohols with straight-chain carbon backbones of >C7 or a ring structure. These include varying mixed isomers of linear and branched diheptyl, dioctyl, dinonyl, didecyl, diundecyl and ditridecyl phthalate. All exhibit low solublity in water and are regarded as being too insoluble to exhibit acute or chronic toxicity. Read-across from closely related phthalates thus appears reasonable and this is supported by the data, below:

The adsorption coefficient (Koc) on soil and on sewage sludge using high performance liquid chromatography (HPLC) has been estimated for a phthalate ester with C-11 chain length. Adsorption coefficients were estimated to be log Koc soil = 21.41 and log Koc sewage sludge = 23.21.

 

The adsorption coefficient (Koc) on soil and on sewage sludge using high performance liquid chromatography (HPLC) has also been determined for a phthalate ester with C-6 to C-10 chain length. Adsorption coefficients were estimated to be log Koc soil = 5.55-10.37 and log Koc sewage sludge = 6.29-12.09.

 

In addition the adsorption coefficient (Koc) of the substance, a phthalate ester with chain length of C9 to C-11, has been estimated using calculation methods to yield a log Koc of 6.397. This value is lower than that obtained experimentally on two analogous substances and is likely to be an under-estimate.

 

In all cases, the McCall classification scheme classifies the substances as immobile in soil (Koc > 5000).


Other adsorption coefficient indicated as dimensionless:
- other: Log Koc sewage sludge ,23.21 at the temperature 20.0°C

[LogKoc: 21.41]