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Partition coefficient

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Description of key information

 Log Kow of 1,2,4-trimethylbenzene is 3.63. 

Key value for chemical safety assessment

Additional information

Partition coefficient values for this substance are cited in a number of reliable, peer-reviewed secondary data sources. A weight of evidence approach has been used to fill this endpoint based on the data from these secondary sources. A log Kow value of 3.63 is cited in Hansch (1995, citing Doucette and Andren, 1988), Lide (2008) and in the CODATA database (citing Wasik et al 1981). This same value taken from Hansch (1995) is also used in the training data set of the USEPA KOWWIN QSAR (USEPA 2008). As this QSAR is widely accepted by Regulators, we believe this demonstrates that the data used to develop the model should also be considered reliable. It appears that at least two separate original sources are being cited in these four data sources. The CODATA database also contains a number of log Kow values for this substance from different primary sources. These log Kow results available in the database are 3.58 (Mackay et al 1980), 3.78 (Hammers et al 1982), 3.91 (Sherblom et al 1988) and 3.65 (Guo et al 1996). Hansch (1995) also cites the value of 3.78 from Hammers et al 1982.

The reported log Kow values range from 3.58 -3.91 and are therefore within a narrow range. They do not span any criteria used to define the appropriate classification of the substance or its bioaccumulation potential. As a number of different primary references are cited by these authoritative data sources we believe that the use of these data is justifiable to fulfil this data requirement.

The log Kow value of 3.63 is identified as the key value for the risk assessment as the method and temperature were stated in the secondary source (CODATA database), two separate publications have reported this value (Wasik et al 1981 and Doucette and Andren 1988), it is reported by several secondary sources, and this value was also used in the training set of the USEPA KOWWIN model.