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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

BCF values for (1-methylethyl)-1,1'-biphenyl were determined in a pre-guideline study using a method similar to OECD TG 305 E. For the two concentrations applied very diverging factors were determined. BCF value of the supporting substance 4-ethylbiphenyl and values calculated for comparison with seven different methods were with one exception below 2000.

Key value for chemical safety assessment

BCF (aquatic species):
2 896 dimensionless

Additional information

BCF values for (1-methylethyl)-1,1'-biphenyl were determined in a pre-guideline study similar to OECD TG 305 E based on uptake and depuration rate constants (Ozburn et al 1980). Documentation is limited. Individual fish concentration data for the different time points of the study are not reported as well as BCF values directly calculated from this data. BCF values were obtained employing the calculation program BIOFAC. It uses the fish concentration data of the uptake and the depuration phase to calculate respective rate constants. BCF is received as the ratio of uptake and depuration rate. BCF values calculated were

low concentration test group (3.5 µg/L)                           2,896

high concentration test group (24.1 µg/L)                      10,790

Both BCF values are remarkably different. The difference is much more pronounced than is normal for other substances similar to isopropylbiphenyl. In addition, compared to BCF of substances with similar molecular structure, the BCF of the high exposure group appears extremely high.

In order to assess the solidity of the measured BCF values, two approaches were taken.

For the supporting substance 4-ethylbiphenyl, a measured value is reported in the literature (Dimitrov, 2005). This value is quoted to be 667. 4-Ethylbiphenyl is used with this value in the training sets of several QSAR models for predicting BCF values. This value is considered as characterising the range of the isopropylbiphenyl BCF. Justification for use of 4-ethylbiphenyl as supporting substance is given in the Section to aquatic toxicity.

In a second step, BCF were estimated for (1-methylethyl)-1,1'-biphenyl using various calculation/QSAR methods. Methods/methodologies and results are displayed in the following table

 

 

US EPA EPI Suite

US EPA T.E.S.T.

Method

regression based on log Kow

Arnot-Gobas

Hierarchical clustering

Single model

Group contribution

FDA

Nearest neighbour

Predicted value

1527

3471

1175

815

1290

1950

440

 

It is obvious, that none of the BCF estimates is close to the value of 10,790 obtained for the high exposure group of Ozburn. Except one value (3,471 - Arnot-Gobas), all other values fall in the range below 2000.

Compared to the BCF of 4-ethylbiphenyl as well as in comparison with the estimated BCF values of isopropylbiphenyl, the measured BCF of 2,896 for (1-methylethyl)-1,1'-biphenyl resulting from the low exposure group of Ozburn appears already high but is considered yet to be realistic. This value is taken as BCF of (1-methylethyl)-1,1'-biphenyl for further use in the chemical safety assessment.

The BCF value for the high exposure group of Ozburn is out of bounds by comparison to the data compiled to evaluate the BCF value of isopropylbiphenyl. It is considered as outlier and is disregarded.