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Bioaccumulation: aquatic / sediment

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Reference
Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
September 2009
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
EpiSuite v4.11, US EPA, 2012

2. MODEL (incl. version number)
BCFBAF v3.00

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
SCCC(=O)OCC(COC(=O)CCS)(COC(=O)CCS)COC(=O)CCS

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: BCF
- Unambiguous algorithm:
The BCFBAF method classifies a compound as either ionic or non-ionic. Ionic compounds include carboxylic acids, sulfonic acids and salts of sulfonic acids, and charged nitrogen compounds (nitrogen with a +5 valence such as quaternary ammonium compounds). All other compounds are classified as non-ionic.

Training Dataset Included:
466 Non-Ionic Compounds
61 Ionic Compounds (carboxylic acids, sulfonic acids, quats)

Methodology for Non-Ionic was to separate compounds into three divisions by Log Kow value as follows:
Log Kow < 1.0
Log Kow 1.0 to 7.0
Log Kow > 7.0

For Log Kow 1.0 to 7.0 the derived QSAR estimation equation is:

Log BCF = 0.6598 Log Kow - 0.333 + Σ correction factors
(n = 396, r2 = 0.792, Q2 = 0.78, std dev = 0.511, avg dev = 0.395)

The previous BCFWIN equation:
Log BCF = 0.77 Log Kow - 0.70 + Σ correction factors

For Log Kow > 7.0 the derived QSAR estimation equation is:

Log BCF = -0.49 Log Kow + 7.554 + Σ correction factors
(n = 35, r2 = 0.634, Q2 = 0.57, std dev = 0.538, avg dev = 0.396)

For Log Kow < 1.0 the derived QSAR estimation equation is: All compounds with a log Kow of less than 1.0 are assigned an estimated log BCF of 0.50

- Defined domain of applicability:
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)-)

- Appropriate measures of goodness-of-fit and robustness and predictivity:
Accuracy of the Training Set:
n=527
r²=0.833
SD=0.502
Average deviation=0.382

Accuracy of the Validation Set:
n=158
r²=0.82
SD=0.59
Average deviation=0.46

5. APPLICABILITY DOMAIN
- Descriptor domain: The components of the substance are within the molecular weight range of the training set compounds, and all fragments are represented in the training set. Thus, it is concluded, that the substance is within the applicability domain.


6. ADEQUACY OF THE RESULT
The QSAR prediction is valid and of good reliability. Thus, the result is adequate for chemical safety assessment.
Principles of method if other than guideline:
Calculation. Software: BCFBAF v3.00 in Estimation Programs Interface (EPI) SuiteTM, US Environmental Protection Agency's Office of Pollution Prevention and Toxics and Syracuse Research Corporation (SRC).
GLP compliance:
no
Radiolabelling:
no
Vehicle:
no
Test organisms (species):
other: calculation
Route of exposure:
other: calculation
Test type:
other: calculation
Water / sediment media type:
not specified
Details on estimation of bioconcentration:
BASIS FOR CALCULATION OF BCF
- Estimation software: BCFBAF v3.00
Type:
BCF
Value:
23.7 L/kg
Basis:
other:

Summary Results:


Log BCF (regression-based estimate): 1.37 (BCF = 23.7 L/kg wet-wt)


Biotransformation Half-Life (days) : 9.01e-006 (normalized to 10 g fish)


 


Log Kow (experimental): 2.59


Log Kow used by BCF estimates: 2.59


 


Equation Used to Make BCF estimate:


Log BCF = 0.6598 log Kow - 0.333 + Correction


 


Estimated Log BCF = 1.374 (BCF = 23.67 L/kg wet-wt)


 


Whole Body Primary Biotransformation Rate Estimate for Fish:







































































TYPE



NUM



LOG BIOTRANSFORMATION FRAGMENT DESCRIPTION



COEFF



VALUE



Frag



4



Ester [-C(=O)-O-C]



-0.7605



-3.0421



Frag



1



Carbon with 4 single bonds & no hydrogens



-0.2984



-0.2984



Frag



12



-CH2- [linear]



0.0242



0.2902



L Kow



*



Log Kow = 2.59 (KowWin estimate)



0.3073



0.7952



MolWt



*



Molecular Weight Parameter



 



-1.2531



Const



*



Equation Constant



 



-1.5058



RESULT


RESULT


NOTE



LOG Bio Half-Life (days)



 



-5.0452



Bio Half-Life (days)



 



9.011e-006



Bio Half-Life Normalized to 10 g fish at 15°C



 



 



 


Biotransformation Rate Constant:


kM (Rate Constant): 75 /day (10 gram fish)


kM (Rate Constant): 42.18 /day (100 gram fish)


kM (Rate Constant): 23.72 /day (1 kg fish)


kM (Rate Constant): 13.34 /day (10 kg fish)


Predicted value exceeds theoretical whole body maximum value


kM (Rate constant) of 75/day is recommended/applied for 10 g fish


 


Arnot-Gobas BCF & BAF Methods (including biotransformation rate estimates):


Estimated Log BCF (upper trophic) = 0.581 (BCF = 3.814 L/kg wet-wt)


Estimated Log BAF (upper trophic) = 0.581 (BAF = 3.814 L/kg wet-wt)


Estimated Log BCF (mid trophic)= 0.667 (BCF = 4.644 L/kg wet-wt)


Estimated Log BAF (mid trophic)= 0.667 (BAF = 4.644 L/kg wet-wt)


Estimated Log BCF (lower trophic) = 0.689 (BCF = 4.888 L/kg wet-wt)


Estimated Log BAF (lower trophic) = 0.689 (BAF = 4.888 L/kg wet-wt)


 


Arnot-Gobas BCF & BAF Methods (assuming a biotransformation rate of zero):


Estimated Log BCF (upper trophic) = 1.625 (BCF = 42.2 L/kg wet-wt)


Estimated Log BAF (upper trophic) = 1.651 (BAF = 44.76 L/kg wet-wt)

Conclusions:
The BCF of PETMP was determined using the software BCFBAF v3.00 developed by US EPA based on a QSAR approach to assess the potential for bioaccumulation. The BCF was calculated to be 23.7 L/kg and indicates a low bioaccumulation potential.

Description of key information

PETMP is considered to have a low potential for bioaccumulation.

Key value for chemical safety assessment

BCF (aquatic species):
23.7

Additional information

The log Pow for PETMP is reported to be ca. 2.8 at pH 7 and 30 °C (see chapter 4.7). This value is below the trigger value of 3 which indicates the potential of a compound for bioaccumulation and which triggers a test on bioconcentration. To support the estimation of a low bioaccumulation potential, the BCF was determined in a first step using the software BCFBAF v3.00 developed by US EPA based on a QSAR approach to assess the potential for bioaccumulation. The BCF was calculated to be 23.7 and indicates only a low bioaccumulation potential.


The substance is not stable in the aquatic environment. However, it is not experimentally confirmed which mechanisms is the primary cause for the degradation, hydrolysis or oxidation. The hydrolysis test showed the fast elimination of the test substance, probably due to oxidation.


Thus, testing on bioconcentration of PETMP in aquatic organisms is not considered to provide further relevant information for the bioaccumulation assessment as the calculated BCF is far below 2000 which is the criterion for a substance to be classified as 'B'. Additionally, the log Pow of PETMP is lower than 4.5 which is a screening criterion for bioaccumulating substances.