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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Reference
Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification
Justification for type of information:
1. SOFTWARE
EPIWIN software by US-EPA

2. MODEL (incl. version number)
BCFBAF v3.01

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
Oc(c(cc(c1)C)Cc(c(O)c(cc2C)C(CCCC3)C3)c2)c1C(CCCC4)C4

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- The model and the training and validation sets are published by US Environmental Protection Agency (USA).
The Arnot-Gobas model estimates steady-state bioconcentration factor (BCF; L/kg) and bioaccumulation factor (BAF; L/kg) values for non-ionic organic chemicals in three general trophic levels of fish (i.e., lower, middle and upper) in temperate environments. The model calculations represent general trophic levels (i.e., not for a particular fish species) and are derived for “representative” environmental conditions (e.g., dissolved and particulate organic carbon content in the water column, water temperature). Thus, it provides general estimates for these conditions in absence of site-specific measurements or estimates. The default temperature for the BCF and BAF calculations is 10°C (temperate regions); therefore, the model predictions are not recommended for arctic, sub-tropical or tropical regions or for comparisons with other vastly different conditions (e.g., laboratory tests at ~25°C).
The original estimation methodology used by the original BCFWIN program is described in a document prepared for the U.S. Environmental Protection Agency (Meylan et al., 1997). The estimation methodology was then published in journal article (Meylan et al, 1999).
The BCFBAF Program updates the BCF estimation methodology of the BCFWIN program by using an updated and better evaluated BCF database for selecting training and validation datasets. The exact same regression methodology used to derive the original BCFWIN method was used to derive the BCFBAF method for estimating BCF.

5. APPLICABILITY DOMAIN
The minimum and maximum values for molecular weight and logKow are listed below. Currently there is no universally accepted definition of model domain. However, users may wish to consider the possibility that bioconcentration factor estimates are less accurate for compounds outside the MW and logKow ranges of the training set compounds, and/or that have more instances of a given correction factor than the maximum for all training set compounds. It is also possible that a compound may have a functional group(s) or other structural features not represented in the training set, and for which no fragment coefficient was developed; and that a compound has none of the fragments in the model’s fragment library. In the latter case, predictions are based on molecular weight alone. These points should be taken into consideration when interpreting model results.
Training Set (527 Compounds):
Molecular Weight:
Minimum MW: 68.08 (Furan)
Maximum MW: 991.80 Ionic: (2,7-Naphthalenedisulfonic acid, 4-amino-5-hydroxy-3,6- bis[[4-[[2-(sulfooxy)ethyl]sulfonyl]phenyl]azo]-, tetrasodium salt)
Maximum MW: 959.17 Non-Ionic: (Benzene, 1,1 -oxybis[2,3,4,5,6-pentabromo-)
Average MW: 244.00
Log Kow:
Minimum LogKow: -6.50 Ionic: (2,7-Naphthalenedisulfonic acid, 4-amino-5-hydroxy-3,6-bis[[4-[[2-(sulfooxy)ethyl]sulfonyl]phenyl]azo]-, tetrasodium salt)
Minimum LogKow: -1.37 Non-Ionic: (1,3,5-Triazine-2,4,6-triamine)
Maximum LogKow: 11.26 (Benzenamine, ar-octyl-N-(octylphenyl)-)
Model predictions may be highly uncertain for chemicals that have estimated log KOW values > 9. The model is not recommended at this time for chemicals that appreciably ionize, for pigments and dyes, or for perfluorinated substances.

6. ADEQUACY OF THE RESULT
The organic substance 2,2'-Methylen-bis-(4-methyl-6-cyclohexylphenol) lies within the applicability domain with a molecular weight of 392.57 and a logPow of 6.3. The result seems reasonable taking into account the structure of the substance and its water solubility. Due to the magnitude of the result and the suitable training set the result is considered as adequate.
Reference:
Composition 0
Guideline:
other: REACH guidance on QSARs Chapter R.6
Version / remarks:
May 2008
GLP compliance:
no
Test material information:
Composition 1
Type:
BCF
Value:
6 664 L/kg
Type:
other: logBCF
Value:
3.824 dimensionless
Validity criteria fulfilled:
not applicable
Conclusions:
The study report describes a scientifically accepted calculation method for the BCF using the US-EPA software BCFBAF v3.01. No GLP criteria are applicable for the usage of this tool and the QSAR estimation is easily repeatable. The result is adequate for the regulatory purpose.
BCF = 6664 L/kg
Executive summary:

The bioaccumulation factor BCF of the substance 2,2'-Methylen-bis-(4-methyl-6-cyclohexylphenol) was determined by the computer program BCFBAF v3.01 (EPIWIN software) by US-EPA (2012). The program uses the chemical structure of a compound to predict the bioaccumulation factor BCF. The structure is denoted in its SMILES notation. The experimentally determined logPow was entered manually. In this case a BCF of 6664 L/kg was determined as result.

Adequacy of the QSAR:

- QSAR model is scientifically valid.

- The substance falls within the applicability domain of the QSAR model.

- The prediction is fit for regulatory purpose.

Description of key information

Key value for chemical safety assessment

BCF (aquatic species):
6 664 L/kg ww

Additional information