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Bioaccumulation: aquatic / sediment

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Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Summary of QSAR models and read acros comparisons for the registered substance
Principles of method if other than guideline:
QSAR and read cross
GLP compliance:
no
Key result
Type:
BCF
Value:
<= 8.1 L/kg
Remarks on result:
other: Based on the data presented above, it is possible to construct a strong case based on the available weight of evidence that bioaccumulation is not a concern for CAS 2373-38-8.
Validity criteria fulfilled:
not applicable
Executive summary:

Based on the data presented above, it is possible to construct a strong case based on the available weight of evidence that bioaccumulation is not a concern for CAS 2373-38-8. The in silico fish BCF QSAR data for the target substance, combined with the empirical fish BCF data for the source substance (considered valid for read-across to the target), leads to the conclusion that CAS 2373-38-8 should not be considered as potentially bioaccumulative in the environment. This conclusion is considered to be sufficiently well-supported to justify no need for experimental BCF testing for CAS 2373-38-8 in fish, since vertebrate testing should always be avoided where scientifically reliable data providing evidence of low bioaccumulation potential exists.

Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, and documentation / justification is limited
Justification for type of information:
1. SOFTWARE

EPISuite 4.11

2. MODEL (incl. version number)

BCFBAF (v3.01)

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL

CAS 2373-38-8
CC(C)CC(C)OC(=O)C(S(=O)(=O)O([Na]))CC(=O)OC(C)CC(C)C

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint:
yes
- Unambiguous algorithm:
yes
- Defined domain of applicability:
yes (similar substance is within the training set)
- Appropriate measures of goodness-of-fit and robustness and predictivity:
yes
- Mechanistic interpretation:
no

5. APPLICABILITY DOMAIN
- Descriptor domain: A similar substance (CAS 577-11-7) is part of the training set (BCF 9.33 L/kg)
- Structural and mechanistic domains: A similar substance (CAS 577-11-7) is part of the training set (BCF 9.33 L/kg)
- Similarity with analogues in the training set:
A similar substance (CAS 577-11-7) is part of the training set (BCF 9.33 L/kg)
- Other considerations (as appropriate):
for surface active substances, the QSAR calculations which are based on the logKow are considered to be not appropriate by ECHA.

6. ADEQUACY OF THE RESULT
The result is used in the WoE approach.

BCFBAF™: Formerly called BCFWIN™, this program estimates fish bioconcentration factor and its logarithm using two different methods. The first is the traditional regression based on log KOW plus any applicable correction factors, and is analogous to the WSKOWWIN™ method. The second is the Arnot-Gobas method, which calculates BCF from mechanistic first principles. BCFBAF also incorporates prediction of apparent metabolism half-life in fish, and estimates BCF and BAF for three trophic levels.

Further information on the models, trainings sets and validation is provided in the attached background information.

The result is considered to be adequate for the risk assessment.
Qualifier:
no guideline followed
Principles of method if other than guideline:
QSAR
Type:
BCF
Value:
3.16 L/kg
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: regression based on log KOW plus any applicable correction factors
Type:
BAF
Value:
6.719 L/kg
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: Arnot-Gobas (upper tropic)
Validity criteria fulfilled:
not applicable
Conclusions:
The QSAR tool BCFBAF (v3.01) predicts a BCF of 3.16 L/kg (regression based estimate for ionic substance)
Executive summary:

The QSAR tool BCFBAF (v3.01) predicts  a BCF of 3.16 L/kg (regression based estimate Ionic substance)

Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
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 adequate and reliable documentation / justification
Justification for type of information:
1. SOFTWARE
OASIS Catalogic v.5.14.1.5

2. MODEL (incl. version number)
BCF base-line model
Catalogic v.04.11 - November, 2019
available in OASIS Catalogic v.5.14.1.5

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CC(C)CC(C)OC(=O)CC(C(=O)OC(C)CC(C)C)S(=O)(=O)O{-}.[Na]{+}

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: BCF (QMRF attached)
- Unambiguous algorithm: yes
- Defined domain of applicability: yes
- Appropriate measures of goodness-of-fit and robustness and predictivity: yes
- Mechanistic interpretation: yes (The expected uptake mechanism of the target chemical is passive diffusion across biological
membranes.)

5. APPLICABILITY DOMAIN
- Descriptor domain: The chemical fulfils the general properties requirements
- Structural domain: The chemical is in the interpolation structural space
- Mechanistic domain: The chemical is in the mechanistic domain of the model.
- Similarity with analogues in the training set: not reported


6. ADEQUACY OF THE RESULT
The result is considered to be adequate for the risk assessment.



For details see also QMRF file.
Principles of method if other than guideline:
QSAR modelling using the CATALOGIC simulation
GLP compliance:
no
Radiolabelling:
no
Key result
Type:
BCF
Value:
4.9 L/kg
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: QSAR calculation, this is the highest log Pow including parent substance and metabolites as predicted by Catalogic. The output by Catalogic is log BCF = 0.69, the BCF has been calculated from this to 4.90 L/kg.
Validity criteria fulfilled:
yes
Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Justification for type of information:
see read across justification
Reason / purpose for cross-reference:
read-across source
Lipid content:
4.1 %
Time point:
other: not reported
Conc. / dose:
50 µg/L
Temp.:
25 °C
Type:
BCF
Value:
9.33 L/kg
Basis:
whole body w.w.
Calculation basis:
steady state
Conc. / dose:
500 µg/L
Temp.:
25 °C
Type:
BCF
Value:
0.891 L/kg
Basis:
whole body w.w.
Calculation basis:
steady state
Validity criteria fulfilled:
yes
Conclusions:
BCF fish Cyprinus carpio 4.1 % lipid content: 9.33 and 0.891 L/kg at water concentrations of 500 and 50 µg/L
Executive summary:

The source of the experimental fish BCF data is actually cited by Arnot and Gobas (2006) as being from the Japanese National Institute of Technology and Evaluation (NITE) database for Biodegradation and Bioconcentration of Existing Chemical Substances under the Chemical Substances Control Law. In this study, the non-radiolabelled source substance sodium docusate was exposed to common carp (Cyprinus carpio) at concentrations of 0.5 and 0.05 mg/L under flow-through conditions for 42 days. At the end of the study, whole body fish BCF values of 9.33 and 0.891 L/Kg were obtained for fish exposed to 0.05 and 0.5 mg/L of sodium docusate, respectively.


 


The fish BCF data from this study was assigned a high overall quality and reliability rating in the publication by Arnot and Gobas (2006) (see spreadsheet in Annex I) and the data is included in the training set for ionisable chemicals in the BCFBAF v3.01 QSAR model as part of the US EPA Episuite software package.[1] This fish BCF data for sodium docusate is also included in the BCF gold standard database developed as a result of a CEFIC LRI project in 2006 (CEFIC, 2007). On this basis, the quality and reliability of this source data for sodium docusate is deemed sufficient to use for adressing this data requirement.


 


Since the target substance is structurally similar to the source substance, the read across is considered to be justified and supports that the target substance is not bioaccumulating.


The study is considered relevant and reliable for the risk assessment of the target substance.


 


[1]The BCF values selected for the BCFBAF training and validation datasets are available in Appendix G and via Internet download at:http://esc.syrres.com/interkow/EpiSuiteData.htm

Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
significant methodological deficiencies
Justification for type of information:
See read across justification
Reason / purpose for cross-reference:
read-across source
GLP compliance:
no
Details on preparation of test solutions, spiked fish food or sediment:
see above
Conc. / dose:
5.5 µg/L
Temp.:
12 °C
Type:
BCF
Value:
3.47 L/kg
Basis:
other: blood
Calculation basis:
kinetic
Conc. / dose:
5.5 µg/L
Temp.:
12 °C
Type:
BCF
Value:
3.78 L/kg
Basis:
other: Carcass
Calculation basis:
kinetic
Metabolites:
not determined in the BCF study. The BCF was based on total 14C activity.
Validity criteria fulfilled:
not specified
Executive summary:

Experimental fish BCF data are available for the closely related read-across analogue substance sodium docusate (CAS: 577-11-1) from a peer reviewed publication by Goodrich et al (1991). In this study, the bioconcentration and metabolism of 14C-radiolabelled sodium docusate was assessed in rainbow trout (Onchorynchus mykiss) and bioconcentration factor (BCF). The trout were exposed for 72h uptake followed by a 72h period for depuration with tissue sampling and analysis conducted at 2, 4, 12, 24, 48 and 72h during both phases. At the end of the study, sodium docusate was calculated to have bioconcentration factor values of 3.47 (blood) and 3.78 (carcass) in rainbow trout. Although this study was not conducted in accordance with current OECD 305 guidelines, it does indicate the bioaccumulation potential of the read-across substance is low and possibly even overestimated given the fact the use of radiolabelled test compound does not discriminate between parent and metabolites.


Since the study period was shorter than requested by the guideline and no equilibrium was reached, the result is considered to be not fuly reliable.


However, the result from this structurally similar source substance supports the QSAR finding for the registered substance that the registered substance is not bioaccumulating.


 

Endpoint:
bioaccumulation in aquatic species: fish
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance has a low potential for bioaccumulation based on log Kow <=3

Description of key information

In accordance with EC 1907/2006, Annex IX, point 9.3.2, column 2, bioaccumulation in aquatic species (water and sediment) is not required due to the fact that the substance has a log Kow of < 3 (0).


An experimental study with a structurally similar source substance (CAS 577-11-7, Arnot & Gobas 2006, 42 day exposure, steady state) resulted in a BCF of 9.33 L/kg in carp (4.1% lipid content). A further 72 -hour study with the same source substance CAS 577-11-7 (Goodrich et al. 1991) with rainbow trout resulted in a BCF of 3.78 L/kg in carcas. In addition to the experimental results, a QSAR using the BCFBAF (v3.01) module implemented in EPISuite 4.11 resulted in a BCF of 56.2 L/kg for the source substance. Hence, there was a good agreement between the experimental values and the QSAR with the indication that the result from the QSAR model results in more conservative values. For the registered substance, the same QSAR model as for the source substance resulted in a BCF of 3.16 L/kg. Hence, it can be assumed that the EPISuite result is conservative for the registered substance as well.


For the registered substance, a QSAR calculation with the model Catalogic resulted in a maximum BCF of 4.90 L/kg for the parent substance and its metabolites. As for EPISuite, a direct comparison of the experimental result and the Catalogic QSAR prediction for the BCF of docusate sodium, the source substance, resulted in the finding that the QSAR prediction from Catalogic for docusate sodium and its metabolites (13.8 L/kg) is slightly more conservative than the experimental finding (9.33 L/kg). Hence, it can be assumed that this is the case also for the registered substance.


For the risk assessment, the more conservative experimentally determined BCF of 9.33 L/kg will be used since this study with the source substance is considered to be scientifically most relevant study. The use of the less conservative QSAR result of the source substance would not have had a different qualitative outcome for, e.g., the PBT assessment. The QSAR results (two models) for the registered substances and its metabolites resulted in lower BCFs. Hence, the BCF of 9.33 L/kg is conservative and will be used for the risk assessment.


In conclusion, bioaccumulation of the substance is of no concern.


 

Key value for chemical safety assessment

Additional information