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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

BCF value was derived from an OECD 305 study and other approaches under a WoE approach.
BCF of TDM lies between 500 and 1950 L/kg.

Key value for chemical safety assessment

BCF (aquatic species):
1 950 L/kg ww

Additional information

The BCF of TDM has been determined using a number of different methods (see document "TDM BCF report FINAL.pdf" attached):

 

1.   Prediction from the BCF/BAF Arnot-Gobas model using a log Kow of 7.43 are 496, 688 and 760 L/Kg for TDM depending upon the trophic level of the fish used in the model.

2.   Prediction with the Gobas model and including the experimental TDM metabolism from the trout cell-line in vitro study,Cowan-Ellsberry et al.(2008), the BCF was predicted to be in a range from 594 to 867 L/Kg

3.   The experimentally derived BMF was measured in a study based on the OECD 305 draft protocol, 2010, Egeler and Gilberg (2012). The growth-corrected BMFK values are 0.00356 based on wet weight, and 0.00635 based on the mean lipid content as determined in fish and food which correlates with BCF values of 260 to 1246 when compared with other chemicals, where the BCF and BMF have been measured.

4.   Experimentally, in vivo with the BMF method including a transformation to BCF using allometric equations. As no single BCF value can be estimated a range of values is provided. The BCFs have been lipid normalised to 5% w/w as recommended by the OECD Guideline. Due to the difference in depuration rate equations, two sets of BCF have been highlighted depending on whether the 7 or 14 day depuration data are used (each based on six K1 calculation methods):

a.  Lipid normalised BCF based on 7 day: mean = 1369.9 (with a range of approximately 1000 to 1950) and

b.  Lipid normalised BCF based on 14 day: mean = 2577.8 (with a range of approximately 1500 to 3650) depending on the method.

 

Given the concerns already expressed about these data, a weight of evidence approach leads to the conclusion that there is reasonable evidence the BCF of TDM lies between 500 and 1950 L/Kg.

 

Using the equation recommended in REACH guidance (R11 and R7) from Sijm et al, 1995, the BCF based on day 7 data is estimated to be 1067 L/Kg and based on day 14 data is 2008 L/Kg.