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Bioaccumulation: aquatic / sediment

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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
EPI Suite v4.11 Estimation Programs Interface Suite™ for Microsoft® Windows v 4.11. US EPA, United States Environmental Protection Agency, Washington, DC, USA.

2. MODEL (incl. version number)
BCFBAF v3.01, regression-based method

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
See “Test material information”

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached information on the model provided by the developer. Further information on the OECD criteria as outlined by the applicant is provided below under "Any other information of materials and methods incl. tables"

5. APPLICABILITY DOMAIN
See attached information and information as provided in "Any other information on results incl. tables".

6. ADEQUACY OF THE RESULT
See assessment of adequacy as outlined in the "Overall remarks, attachments" section.
Principles of method if other than guideline:
- Software tool(s) used including version: EPI Suite v4.11
- Model(s) used: BCFBAF v3.01
Full reference and details of the used formulas can be found in:
1. Meylan, W.M., Howard, P.H, Aronson, D., Printup, H. and S. Gouchie.  1997.  "Improved Method for Estimating Bioconcentration Factor (BCF) from Octanol-Water Partition Coefficient", SRC TR-97-006 (2nd Update), July 22, 1997; prepared for: Robert S. Boethling, EPA-OPPT, Washington, DC; Contract No. 68-D5-0012; prepared by: ; Syracuse Research Corp., Environmental Science Center, 6225 Running Ridge Road, North Syracuse, NY 13212.
2. Meylan,WM, Howard,PH, Boethling,RS et al. 1999.  Improved Method for Estimating Bioconcentration / Bioaccumulation Factor from Octanol/Water Partition Coefficient.Environ. Toxicol. Chem. 18(4): 664-672 (1999).
- Model description: see field 'Justification for non-standard information', 'Attached justification' and 'any other information on Material and methods'
- Justification of QSAR prediction: see field 'Justific ation for type of information', 'Attached justification' and/or 'overall remarks'
GLP compliance:
no
Test organisms (species):
other: Fish
Route of exposure:
aqueous
Test type:
other: calculation
Water / sediment media type:
natural water: freshwater
Details on estimation of bioconcentration:
BASIS FOR CALCULATION OF BCF
- Estimation software: BCFBAF v3.01
- Result based on calculated log Kow of: 2.75 – 4.26 (estimated, KOWWIN v.1.68)
Type:
BCF
Value:
>= 12.7 - <= 110 L/kg
Basis:
whole body w.w.
Remarks on result:
other: Calculated BCF range of six representative isomers
Type:
other: Log BCF
Value:
>= 1.11 - <= 2.04 dimensionless
Basis:
whole body w.w.
Remarks on result:
other: Calculated log BCF range of six representative isomers

For detailed information on the results please refer to the attached report.

Endpoint:
bioaccumulation: aquatic / sediment
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
EPI Suite v4.11 Estimation Programs Interface Suite™ for Microsoft® Windows v 4.11. US EPA, United States Environmental Protection Agency, Washington, DC, USA.

2. MODEL (incl. version number)
BCFBAF v3.01, Arnot-Gobas method

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
See “Test material information”

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached information on the model provided by the developer. Further information on the OECD criteria as outlined by the applicant is provided below under "Any other information of materials and methods incl. tables"

5. APPLICABILITY DOMAIN
See attached information and information as provided in "Any other information on results incl. tables".

6. ADEQUACY OF THE RESULT
See assessment of adequacy as outlined in the "Overall remarks, attachments" section.
Qualifier:
according to guideline
Guideline:
other: REACH Guidance on QSARs R.6
Principles of method if other than guideline:
- Software tool(s) used including version: EPI Suite v4.11
- Model(s) used: BCFBAF v3.01
Full reference and details of the used formulas can be found in:
1. Arnot JA, Gobas FAPC. 2003. A generic QSAR for assessing the bioaccumulation potential of organic chemicals in aquatic food webs. QSAR and Combinatorial Science 22: 337-345.
- Model description: see field 'Justification for non-standard information', 'Attached justification' and 'any other information on material and methods'
- Justification of QSAR prediction: see field 'Justific ation for type of information', 'Attached justification' and/or 'overall remarks'
GLP compliance:
no
Vehicle:
no
Test organisms (species):
other: Fish
Route of exposure:
other: aqueous and dietary
Test type:
other: calculation
Water / sediment media type:
natural water: freshwater
Details on estimation of bioconcentration:
BASIS FOR CALCULATION OF BCF
- Estimation software: EPI Suite v4.11, BCFBAF v3.01
- Result based on calculated log Pow of: 2.75 – 4.26
Type:
BCF
Value:
>= 4.07 - <= 12.58 L/kg
Basis:
whole body w.w.
Remarks on result:
other: including biotransformation, upper trophic
Remarks:
calculated BCF range of six representatives isomers
Type:
other: log BCF
Value:
>= 0.61 - <= 1.1 dimensionless
Basis:
whole body w.w.
Remarks on result:
other: including biotransformation, upper trophic
Remarks:
Calculated log BCF range of six representative isomers

For detailed information on the results please refer to the attached report.

Endpoint:
bioaccumulation in aquatic species, other
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, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification
Remarks:
The substance is not fully compliant with the applicability domain of the model. However, this calculation is used in a weight of evidence approach, in accordance to the REACh Regulation (EC) No 1907/2006, Annex XI General rules for adaptation of the standard testing regime set out in Annexes VII to X, 1.2. It is adequately documented and justified. For more detail see field `overall remarks, attachments´.
Justification for type of information:
1. SOFTWARE
Vega version 1.1.3

2. MODEL (incl. version number)
BCF Meylan Model v1.0.3

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
See “Test material information”

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached information on the model provided by the developer. Further information on the OECD criteria as outlined by the applicant is provided below under "Any other information of materials and methods incl. tables"

5. APPLICABILITY DOMAIN
See attached information and information as provided in "Any other information on results incl. tables".

6. ADEQUACY OF THE RESULT
See assessment of adequacy as outlined in the "Overall remarks, attachments" section.
Qualifier:
according to guideline
Guideline:
other: REACH Guidance on QSARs R.6
Principles of method if other than guideline:
- Software tool(s) used including version: Vega v1.1.3
- Model(s) used: BCF Meylan Model version 1.0.3
Full reference and details of the used formulas can be found in:
Meylan W.M., Howard P.H., Boethling R.S. et al. Improved Method for Estimating Bioconcentration / Bioaccumulation Factor from Octanol/Water Partition Coefficient. 1999, Environ. Toxicol. Chem. 18(4): 664-672
- Model description: see field 'Justification for non-standard information', 'Attached justification' and 'any other information on Material and methods'
- Justification of QSAR prediction: see field 'Justification for type of information', 'Attached justification' and/or 'overall remarks'
GLP compliance:
no
Vehicle:
no
Test organisms (species):
other: Fish
Route of exposure:
aqueous
Justification for method:
minimised test method used to support BCF estimates based on QSAR
Test type:
other: calculation
Water / sediment media type:
natural water: freshwater
Details on estimation of bioconcentration:
BASIS FOR CALCULATION OF BCF
- Estimation software: Vega version 1.1.3, Meylan Model version 1.0.3
- Result based on calculated log Pow of: 2.35 - 3.41
QSAR calculations were performed using six representative individual constituents of the UVCB substance. All six molecules are monoesters of Dodecanoic acid and oxybis[propanediol]. Structural differences are related to the esterification position on the poly-functional alcohol, and on the isomerization of the alcohol’s structure.
Type:
BCF
Value:
>= 16 - <= 83 L/kg
Basis:
whole body w.w.
Remarks on result:
other: Calculated BCF range of six representative isomers
Type:
other: Log BCF
Value:
>= 1.22 - <= 1.92 dimensionless
Basis:
whole body w.w.
Remarks on result:
other: Calculated log BCF range of six representative isomers

For detailed information on the results please refer to the attached report.

Description of key information

Key value for chemical safety assessment

Additional information

Experimental bioaccumulation data are not available for Dodecanoic acid, monoester with oxybis[propanediol] (CAS No. 96499-68-2). The substance is a UVCB substance whose individual constituents have a log Kow range of <0.3 to >6.5. This range indicates a potential for bioaccumulation for some individual constituents. However, the information gathered on environmental behaviour and metabolism in combination with QSAR results provide enough evidence (in accordance with Regulation (EC) No 1907/2006, Annex XI General rules for adaptation of the standard testing regime set out in Annexes VII to X, 1.2), to state that the substance is likely to show negligible bioaccumulation potential.

 

Environmental behaviour

Dodecanoic acid, monoester with oxybis[propanediol] (CAS No. 96499-68-2) is readily biodegradable (84% degradation after 28 d, O2 consumption). The substance is therefore assumed to degrade rapidly and ultimately in most environments, including biological sewage treatment plants (STP). Thus, only limited amounts will get in contact with activated sludge microorganisms in STPs and the concentration of the substance in effluents of conventional STPs is presumably marginal.

In order to support the prediction that Dodecanoic acid, monoester with oxybis[propanediol] (CAS No. 96499-68-2) has negligible bioaccumulative potential, QSAR calculations were performed using six representative individual constituents of the UVCB substance. All six molecules are monoesters of Dodecanoic acid and oxybis[propanediol]. Structural differences are related to the esterification position on the poly-functional alcohol, and on the isomerization of the alcohol’s structure.

A log BCF range of 1.11 - 2.04, corresponding to a BCF range of 12.7 – 110, was calculated using BCFBAF Program (v3.01), regression-based estimate. A log BCF range of 0.610 – 1.100, corresponding to a BCF range of 4.07 – 12.58, was calculated using BCFBAF Program (v3.01), Arnot-Gobas upper trophic model. In addition a log BCF range of 1.22 – 1.92, corresponding to a BCF range of 16 – 83, was calculated using VEGA (v1.1.3), Meylan Model v1.0.3. All calculated BCF values are below the critical classification level of BCF = 500; the bioaccumulation potential of Dodecanoic acid, monoester with oxybis[propanediol] (CAS No. 96499-68-2) is therefore considered negligible.
The constituents of the UVCB substance all fit in the applicability domain of the selected QSAR models (except for VEGA). Thus, the results are valid and can be used for the assessment of bioaccumulation potential of the substance.

 

Metabolism/Bioaccumulation

After uptake and absorption, Dodecanoic acid, monoester with oxybis[propanediol] (CAS No. 96499-68-2) is expected to be enzymatically hydrolysed by carboxylesterases yielding the corresponding alcohol and fatty acids. The metabolism of the hydrolysis products alcohol (i.e. glycerol) and fatty acids is well established and not of concern in terms of bioaccumulation. Glycerides are the predominant lipid class in the diet of both marine and freshwater fish. Once ingested, they will be hydrolysed into fatty acids and glycerol by a specific group of carboxylesterase (CaE) enzymes (lipases) as reported in different fish species (Tocher, 2003). Parts of the free fatty acids will be re-esterified once more with glycerol and partial acyl glycerols to form triglycerides, which will be stored as long-term energy reserves. Glycerol is naturally present in animal and vegetable fats, rarely found in free state (mostly combined with fatty acids forming triglycerides) (ed. Knothe, van Gerpen and Krahl, 2005). If freely available in aquatic organisms, it will not bioaccumulate in view of its low log Kow value of -1.76 (OECD SIDS, 2002). Especially in periods in which the energy demand is high (reproduction, migration, etc.), glycerides are mobilized from the storage sites as source of fatty acids. Fatty acid catabolism is the most important energy source in many species of fish, resulting in the release of acetyl CoA and NADH (through β-oxidation) and eventually, via the tricarboxylic cycle, the production of metabolic energy in the form of ATP. This fatty acid-catabolism pathway is the predominant source of energy related to growth, reproduction and development from egg to adult fish. A similar metabolic pathway is observed in mammals (see section 7.1.1 Basic toxicokinetics). In conclusion, no potential for bioaccumulation is to be expected for Dodecanoic acid, monoester with oxybis[propanediol] (CAS No. 96499-68-2).

 

Conclusion

Dodecanoic acid, monoester with oxybis[propanediol] (CAS No. 96499-68-2) is a UVCB substance whose individual constituents have a log Kow range of <0.3 to >6.5 which is indicative of bioaccumulative potential. However, due to its readily biodegradable nature, extensive degradation of the substance in conventional STPs will take place and only low concentrations are expected to be released (if at all) into the environment. Once present in the aquatic compartment, further biodegradation will occur. If the substance is taken up by organisms, extensive and fast biotransformation of the substance by carboxylesterases into fatty acids and glycerol is expected. BCF/BAF values estimated by QSAR (BCFBAF v3.01) also support the assumption that the substance has low bioaccumulation potential (BCF values all well below 500 L/kg).

Taking all these information into account, it can be concluded that bioaccumulation of Dodecanoic acid, monoester with oxybis[propanediol] (CAS No. 96499-68-2) acid is unlikely to occur.