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EC number: 229-355-1
CAS number: 6486-23-3
According to REACH Guidance R.7c section 188.8.131.52 on tests according to
OECD 305 states that this test might not provide a reliable BCF for
compounds with low aqueous solubility (i.e. below ~10 to 100 micro-g/L).
The submission substance is of extremely low water solubility. As such,
a test according to OECD 305 would most certainly not result in reliable
BCF data. According to the same guideline section, dietary studies are
only recommended for compounds with log Kow > 6 (2.9 for the
submission substance). According to R.7.10.5. describing the hierarchy
of preferred data sources to determine a potential for bioaccumulation,
predicted data from validated QSAR models are on rank 3 (rank 1 and rank
2: reliable BCF data from fish and invertebrates, respectively) and
preferred over in vitro data. Step 3B "evaluation of non-testing data"
states that "QSARS based on Kow are generally recommended if Kow is a
good predictor of bioconcentration". This is the case for the
application of CAESAR BCF-model on the submission substance. In accord
with the here presented data the guidance states that good correlation
of experimental and calculated data for analogues "increases the
confidence in the BCF prediction for the substance" (see attached QPRF).
According to the guidance, calculated BCF-data based on log Kow are
regarded as an upper estimate which may be corroborated or reduced by
strong and weak indicators as specified in table R.7.10-6. If no such
indicators exist, the use of a BCF predicted from Kow is recommended
(see Fig. R.7.10-1 of guidance R.7C). As the model fulfils the OECD
principles for QSAR-models with algorithm and used experimental data for
model build and validation being freely available; as the submission
substance is in the applicability domain of the model and evaluation of
sufficiently similar compounds with experimental data increase the
confidence in the calculated BCF for the submission substance according
to REACH guidance R.7.C; the calculated BCF value is adequate for
PBT/vPvB assessment (first tier) and risk assessment (first tier) for
the submission substance.
Results according to calculation via CAESAR model (key, reliability
category 2; BCF = 10 L/kg ww) are in excellent agreement with the
supporting results from BCFBAF program ( BCF = 10 L/kg ww).
The Arnot and Gobas BCF-model is in general conservative as it assumes
no metabolism (included in regression based models via training data
set) and in particular as a relatively high lipid content of upper
trophic organisms is assumed. The model is independent from a training
data set and the data quality thereof, as it is based on several
relatively simple mechanistical assumptions relating on few
environmental and organism specific parameters and the KOW of the
compound in question. It is therefore completely different from
regression based models dependent on the empirical database used for the
regression. Furthermore as outlined by Arnot and Gobas (2003),
regression based models tend to "arrive at an 'average' BCF value,
allowing for a relatively large number of occurrences where the actual
BCF is greater than the BCF predicted values".
Taken into account the very different methodological approach and the
conservative nature of the value, the deviation by 0.94 log units of the
BCF-value derived according to the Arnot-Gobas model (10.7% lipid
content upper trophic level) from the log BCF of 0.98 according to
CAESAR is modest and may be regarded as an upper confidence limit of the
value derived by CAESAR. This is substantiated by lowering the organism
lipid content to 5% (most standard test fish species) resulting in a log
BCF of 1.61 (i.e. a deviation from the CAESAR derived value of 0.63 log
To estimate BCF of the submission substance by QSAR, besides the key
study (reliability category 2) performed using the CAESAR BCF model v.
v. 184.108.40.206 supporting calculations were performed using BCFBAF v. 3.01
and the Arnot & Gobas (2003) model on bioconcentration. The following
results were achieved:
BCF according to CAESAR (key study): 10 L/kg whole body wet weight
BCF according to BCFBAF (supporting study): 10 L/kg whole body wet weight
BCF according to Arnot & Gobas model, upper trophic level (10.7% lipid
content): 85.6 L/kg whole body wet weight
BCF according to Arnot & Gobas model, standard test fish species (5%
lipid content): 40.6 L/kg whole body wet weight
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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