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The threshold that triggers the need to investigate a potential bioconcentration/bioaccumulation tendency experimentally is a log10 Kow value greater than or equal to 3.0. The US EPA's KOWWIN model predicts a log Kow of 1.76 for isophthalic acid (IPA) and the database on which the model is constructed contains a published (public domain) value of 1.66 for IPA (Hansch, C. et al., 1995).

The octanol/water partition coefficient of isophthalic acid has also been determined according to the shake-flask procedure, in a system buffered to pH 7. The mean log Kow obtained under these conditions was -2.34. This value implies a much higher relative solubility of IPA in the aqueous phase than the log Kow indicated by KOWWIN QSAR and by the experimentally determined value for IPA that has been used in the construction of the KOWWIN model. This is likely to have been caused by the presence of the buffer used to maintain the test system at pH 7: IPA would have been converted under these conditions to salts with higher aqueous solubility than that of the free acid.

Both these log10 Kow values lie below the trigger of 3.0 and isophthalic acid is therefore not expected to exhibit significant bioconcentration or bioaccumulation tendencies. The US EPA's model BCFBAF v3.00 predicts a bioconcentration factor in fish of 3.16 L/kg wet weight, derived from the measured log Kow value. Studies of bioconcentration/bioaccumulation are not triggered for IPA.

It may be concluded that isophthalic acid is not bioaccumulative (not B).

Isophthalic acid is not expected to remain stable in the form of the free acid under environmental conditions. Aquatic ecotoxicology studies have been conducted with IPA after converting it to its disodium salt to increase its solubility and the range of achievable exposure concentrations. This is considered representative of the likely behaviour of IPA in the environment. The increased aqueous solubility of isophthalate salts relative to that of the free acid implies a corresponding decrease in log10 Kow, similar to that observed in the test system buffered to pH 7, and hence a reduced bioconcentration/bioaccumulation potential.