Registration Dossier

Physical & Chemical properties

Partition coefficient

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

Partition coefficient: log Kow = 7.17 (QSAR)

Key value for chemical safety assessment

Additional information

Reasons to use EPISUITE (EPA) to calculate log Kow instead of measurements

Experimental determination of log Kow is very difficult for “pure cut” fatty acids or “broad cut” fatty acids which are represented by C-chain distribution between C8 and C24. Only very few experimental data has been found, see table below. In addition percentages of C-chains may vary to a certain degree.

Following “ECHA guidance information requirements and chemical safety assessment, Chapter R.7(a), section R.7.1.8.4. (page 57)” log Kow may be calculated “when no experimental data of high quality are available, or if experimental methods are known to be unreliable”. In the case of C-chain distributions, the valid (Q)SARs for log Kowis used to find a range of log Kow, e.g. the software EPIWIN (EPA)).

“Log Kow is a commonly documented property in substance databases, such as IUCLID (http://ecb.jrc.it). Additional sources are the Canadian National Committee for CODATA (CNC/CODATA) database with evaluated log Kow values for over 20000 substances (http://logkow.cisti.nrc.ca/logkow/) and the QSAR Toolbox (http://www.qsartoolbox.org).”

Log Kow calculation with EPIWIN (EPA) has been validated using -amongst others- the mentioned data bases and related publications.

For that reason EPIWIN (EPA) and database sources are seen as an appropriate method to determine the log Kow ranges for fatty acid C-chain distributions.

 

Discussion of log Kow values for fatty acids:

 

Substance

log Kow
(calculated EPIWIN)

Log Kow (calculated Rekker (D’Amboise, 1982))

log Kow measured

references

FA, C8

3.05

2.93

 

 

FA, C10

4.02

3.99

3.91

Tehrany, 2005

FA, C8-10

 

 

3.14

Frischmann, 2010

FA, C12

5.00

5.05

 

 

FA, C14

5.98

6.11

 

 

FA, C16

6.96

7.17

 

 

FA, C18

7.94

8.23

 

 

FA, C8-18

 

 

3.3

Frischmann, 2010

FA, C18:1

7.73

7.64

 

 

FA, C18:2

7.51

7.05

 

 

FA, tall oil (16-18, 18:1)

 

 

4.9 - 7.6

Lightbody S.M et al., 2002

FA, C20

8.93

9.29

 

 

FA, C22

9.90

 

 

 

FA, C24

10.89

 

 

 

FA, C8-24

3.05 - 7.73

 

 

 

FA, C14-18 and C16-18 unsatd.

5.98 - 7.94

 

 

 

FA, C18 unsatd.

7.51 - 7.73

 

 

 

FA, hydrogenated tallow, distn. residues

6.96 - 7.94

 

test ordered, result not yet available

 

 

Justification of “read across” and “WoE”

The log Kow values for pure cuts are used as substances to read across to C-chain ranges. The very few experimental data confirm that the Kow values calculated with EPIWIN are always slightly higher proving a “conservative” approach. This is taken as basis to determine a log Kow range for broad cuts like C8-24 fatty acids e.g. for CAS 71076-48-7 Fatty acids, C8-24 the log Kow is in range of 3.05-10.89. Due to low percentages of C8, C10 and >C20 only contributions to log Kow of C-chain between C12 and C18 are considered. In case of CAS 71076-48-7 Fatty acids, C8-24 the log Kow range is 5.00 - 8.23.

This result supports both the read across from pure cuts to broad cuts and the WoE approach.

 

Conclusion

The log Kow 7.17 value was estimated by a validated calculation method according Rekker (D'Amboise, 1982). The value of this study was found in a peer-reviewed database (Sangster). Additionally, a very similar partition coefficient value of log Kow 6.96 was calculated using an alternative, validated calculation method (EPIWIN).