Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs.

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

(Q)SAR

Adequacy of study:

key 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 adequate and reliable documentation / justification

Justification for type of information:

A reliable QSAR model was used to calculate the bioaccumulation potential of Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. (EC No: 941-154-7). BCF values were calculated using the BCFBAF v3.01 module embedded within the EPISuite v4.11 computer model. The calculated BCF (regression-based model) was 70.8 L/kg wet-wt., while the BCF (Arnot-Gobas upper trophic) was 1113 L/kg wet-wt. The SMILES notation used for the predictions was:
OS(=O)(=O)c1cccc(C(CC)CCCCCCCCCCCCC)c1

The BCFBAF predicted bioaccumulation values are considered valid and fit for purpose. A calculated value from a QSAR model is considered valid and fit for purpose if the following conditions are met: 1) Results are derived from a (Q)SAR model whose scientific validity has been established; 2) The substance falls within the applicability domain of the (Q)SAR model; 3) Results are adequate for the purpose of classification and labelling and/or risk assessment and 4) Adequate and reliable documentation of the applied method is provided.

1) Results are derived from a (Q)SAR model whose scientific validity has been established

EPISuite and its modules (including BCFBAF) have been utilized by the scientific community for prediction of phys/chem properties and environmental fate and effect properties since the 1990’s. The program underwent a comprehensive review by a panel of the US EPA’s independent Science Advisory Board (SAB) in 2007. The SAB summarized that the EPA used sound science to develop and refine EPISuite. The SAB also stated that the property estimation routines (PERs) satisfy the Organization for Economic Cooperation and Development (OECD) principles established for quantitative structure-activity relationship ((Q)SAR) validation.

The EPISuite modules (including BCFBAF) have been incorporated into the OECD Toolbox. Inclusion in the OECD toolbox requires specific documentation, validation and acceptability criteria and subjects EPISuite to international use, review, providing a means for receiving additional and on-going input for improvements.

BCFBAF is listed as one of the QSARs for use in predicting bioaccumulation values in the Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance. In summary, the EPISuite modules (including BCFBAF) have had their scientific validity established repeatedly.

2) The substance falls within the applicability domain of the (Q)SAR model

According to the BCFBAF documentation, there is currently no universally accepted definition of model domain. However, the documentation does provide information for reliability of the calculations. Estimates will possibly be less accurate for compounds that 1) have a MW and log Kow outside the ranges of the training set compounds and 2) 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. The molecular weight of Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. is 382.61 which falls within the range of the training set (68.08 to 959.17). Also, its log Kow (6.68) falls within the training set’s range (-1.37 to 11.26).

In addition, the BAF calculations clearly show that all fragments of the substance were analysed:

===========================================================
Whole Body Primary Biotransformation Rate Estimate for Fish:
===========================================================
------+-----+--------------------------------------------+---------+---------
TYPE | NUM | LOG BIOTRANSFORMATION FRAGMENT DESCRIPTION | COEFF | VALUE
------+-----+--------------------------------------------+---------+---------
Frag | 1 | Linear C4 terminal chain [CCC-CH3] | 0.0341 | 0.0341
Frag | 1 | Sulfonic acid / salt -> aromatic attach | 0.0248 | 0.0248
Frag | 1 | Alkyl substituent on aromatic ring | 0.1781 | 0.1781
Frag | 1 | Aromatic-CH | -0.4629 | -0.4629
Frag | 4 | Aromatic-H | 0.2664 | 1.0655
Frag | 2 | Methyl [-CH3] | 0.2451 | 0.4902
Frag | 13 | -CH2- [linear] | 0.0242 | 0.3144
Frag | 1 | Benzene | -0.4277 | -0.4277
L Kow| * | Log Kow = 6.68 (KowWin estimate) | 0.3073 | 2.0516
MolWt| * | Molecular Weight Parameter | | -0.9811
Const| * | Equation Constant | | -1.5371
============+============================================+=========+=========
RESULT | LOG Bio Half-Life (days) | | 0.7498
RESULT | Bio Half-Life (days) | | 5.621
NOTE | Bio Half-Life Normalized to 10 g fish at 15 deg C |
============+============================================+=========+=========


As a result Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. would not be considered outside the estimation domain.

3) Results are adequate for the purpose of classification and labelling and/or risk assessment

BCFBAF calculated the regression based BCF from the following equation:

Equation Used to Make BCF estimate:
Log BCF = 1.85 (Ionic; 11 or more -CH2- groups)

The BCFBAF model had the following statistics:

Training Set
number = 527
correlation coef (r2) = 0.833

Validation Set
number = 158
correlation coef (r2) = 0.82

These correlation coefficients indicate the BCFBAF model calculates results that are equivalent to those generated experimentally and are, hence, adequate for the purpose of classification and labelling and/or risk assessment.

4) Adequate and reliable documentation of the applied method is provided

Documentation of the BCFBAF model is provided in the following references:

Arnot JA, Mackay D, Bonnell M. 2008b. Estimating metabolic biotransformation rates in fish from laboratory data. Environmental Toxicology and Chemistry 27: 341-351.

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.

Arnot, J.A. and F.A.P.C. Gobas. 2006. A review of bioconcentration factor (BCF) and bioaccumulation factor (BAF) assessments for organic chemicals in aquatic organisms. Environmental reviews 14(4): 257-297.

Arnot JA, Meylan W, Tunkel J, Howard PH, Mackay D, Bonnell M, Boethling RS. 2009. A QSAR for predicting metabolic biotransformation rates for organic chemicals in fish. Environmental Toxicology and Chemistry. 28: in press.

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.

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).ECHA (2012) “Guidance on information requirements and chemical safety assessment Chapter R.7b: Endpoint specific guidance”.

McFarland, M. et al. 2007. “Science Advisory Board (SAB) Review of the Estimation Programs Interface Suite (EPI SuiteTM)”.

Qualifier:

no guideline required

Principles of method if other than guideline:

Results are derived from a (Q)SAR model whose scientific validity has been established

GLP compliance:

no

Specific details on test material used for the study:

The SMILES notation used for the predictions was: OS(=O)(=O)c1cccc(C(CC)CCCCCCCCCCCCC)c1

Type:

BCF

Value:

70.8 L/kg

Basis:

whole body w.w.

Calculation basis:

other: regression-based model

Type:

BCF

Value:

1 113 L/kg

Basis:

whole body w.w.

Calculation basis:

other: Arnot-Gobas upper trophic

Validity criteria fulfilled:

yes

Conclusions:

A reliable QSAR model was used to calculate the bioaccumulation potential of Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. (EC No: 941-154-7). BCF values were calculated using the BCFBAF v3.01 module embedded within the EPISuite v4.11 computer model. The calculated BCF (regression-based model) was 70.8 L/kg wet-wt., while the BCF (Arnot-Gobas upper trophic) was 1113 L/kg wet-wt.

Executive summary:

The calculated BCF (regression-based model) for Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. was 70.8 L/kg wet-wt., while the BCF (Arnot-Gobas upper trophic) was 1113 L/kg wet-wt.

Reference 2

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well documented peer-reviewed publication.

Justification for type of information:

see read-across document.

Qualifier:

according to guideline

Guideline:

OECD Guideline 305 E (Bioaccumulation: Flow-through Fish Test)

GLP compliance:

not specified

Radiolabelling:

not specified

Details on sampling:

Water samples (~40 ml) were taken at least once per day, and extracted immediately or preserved with 10% vol MeOH and stored under N2 in a refrigerator for no more than 2 days. Fish samples were killed by immersion in liquid N2, and stored at -20 degrees C until analysis. 2-4 replicates of fish samples were taken.

Vehicle:

not specified

Details on preparation of test solutions, spiked fish food or sediment:

To address differences in composition of mixtures, bioconcentration potential was calculated for
1) mixtures typical of LAS in European detergent formulations (C10 12%, C11 29%, C12 34%, C13 24%; average alkyl chain length = C11.6) and
2) mixtures typical of LAS in filtered Mississippi river water (C10 45%, C11 23%, C12 23%, C13 2%; average chain length = C10.8).

Stock solutions were kept under N2 to prevent aerobic biodegradation.

Test organisms (species):

Pimephales promelas

Details on test organisms:

TEST ORGANISM
- Common name: fathead minnow
- Source: Urecht University hatchery
- Weight at study initiation (mean and range, SD): 0.5-1 g
- Health status: free from observable diseases and abnormalities
- Feeding during test
- Amount: 1 % body weight per day, in order to minimize suspended solids, fish were fed for 30 min in a separate aquarium

ACCLIMATION
- Acclimation period: 1 week

Route of exposure:

aqueous

Test type:

other: measured flow-through

Water / sediment media type:

natural water: freshwater

Total exposure / uptake duration:

48 - 192 h

Hardness:

1.21 mM

Test temperature:

20.7-22.5 degrees C

Details on test conditions:

When tested by itself: The exposure phase in Experiment A was 48-hours. The exposure phase in Experiments B-D ranged from 168 to 192 hours. Due to the rapid equilibrium demonstrated in these studies, a longer exposure period was not needed. Fish were then transferred to untreated water for the depuration phase (duration not stated).

TEST SYSTEM
- Test vessel: aquaria
- Type of flow-through (e.g. peristaltic or proportional diluter): peristaltic
- Renewal rate of test solution (frequency/flow rate): 1 L/day g fish


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstituted H2O

Nominal and measured concentrations:

2.7 and 4.1 uM

Reference substance (positive control):

not specified

Details on estimation of bioconcentration:

The calculation of BCF for the typical mixtures was done using the following equation developed in the above testing:

(ΣCf,i/ΣCw,i)rel = Σ(øi,w x BCFi,rel)

Remarks on result:

other: not reported

Key result

Type:

BCF

Value:

87 L/kg

Details on results:

The BCFs were 87 L/kg for a standard mixture typical of LAS in European detergent formulations (average alkyl chain length = C11.6) and 22 L/kg for a representative environmental sample (filtered Mississippi river water, average alkyl chain length = C10.8)

When tested by itself:

Values of Steady-State Bioconcentration Factor (BCF_ss) and Average Length of Alkyl Chain (n_C,Av) are shown in the following table.

                                                

expt	comp*	BCFss L/kg	nC,Av
A	C10-2	1.7	10.8
	C11-2	5.8
	C12-2	47.6
	C13-2	353.8
B	C11-5	6.1	11.7
	C12-2	99.1
	C12-5	10.0
	C13-5	34.0
C	C11-5	9.8	11.4
	C12-2	168.4
	C12-3	42.1
	C12-6	31.9
D	C10-2	6.0	10.6
	C11-2	31.9
	C12-2	211.5
	C13-2	987.2
	C10-in	3.0
	C11-in	9.1
	C12-in	29.9
	C13-in	112.4

*In the format C_n-m, n and m are the length of the alkyl chain and the position at which the sulfophenyl moiety is substituted to the alkyl chain, respectively.

As shown in the table, BCF values ranged between 2-1000 L/kg.  Experiments A, B and D showed that BCFs increase with increasing alkyl chain length for a given isomer.  In addition, the results of Experiments B and C demonstrate that the closer the p-sulfophenyl moiety is positioned to the terminal carbon of the alkyl chain, the higher the BCF.  However, alkyl chain length has a much bigger effect than does the phenyl position.

Conclusions:

BCF values ranged from between 2 and 1000 L/kg, with BCFs increasing with increasing alkyl chain lengths.

Executive summary:

The bioaccumulation potential of a series of LAS substances was evaluated in flow-through studies with fathead minnows. Results show that the bioconcentration potential of LAS is low and is decreased by environmental processes such as biodegradation and absorption, which reduce aquatic concentrations.

Description of key information

A reliable QSAR model was used to calculate the bioaccumulation potential of Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. (EC No: 941-154-7). BCF values were calculated using the BCFBAF v3.01 module embedded within the EPISuite v4.11 computer model. The calculated BCF (regression-based model) was 70.8 L/kg wet-wt., while the BCF (Arnot-Gobas upper trophic) was 1113 L/kg wet-wt.

In a supporting study, the bioaccumulation potential of a series of LAS homologues and isomers were evaluated in flow-through studies with fathead minnows (Pimephales promelas) according to OECD 305E guidelines. The resulting BCFs ranged from 2 L/kg (6-phenyl-C10 LAS) to almost 1000 L/kg (2-phenyl-C13 LAS), with BCFs generally increasing with increasing alkyl chain length for a given isomer.

Key value for chemical safety assessment

BCF (aquatic species):

1 113 L/kg ww

Additional information

BCF values for Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. were calculated using the BCFBAF (v.3.01) embedded in EPISuite v 4.11. The calculated BCF using the regression based model was 70.8 L/kg wet-wt. while the Arnot-Gobas Upper Trophic BCF was 1113 L/kg wet-wt.

Supporting the QSAR calculations, the bioaccumulation potential of a series of LAS homologues and isomers were evaluated in flow-through studies with fathead minnows (Pimephales promelas) according to OECD 305E guidelines. Individual homologues were tested for up to 192 hours for the uptake phase, followed by a depuration phase in which fish were transferred to unspiked water. The resulting BCFs ranged from 2 L/kg (6-phenyl-C10 LAS) to almost 1000 L/kg (2-phenyl-C13 LAS), with BCFs generally increasing with increasing alkyl chain length for a given isomer. In addition, Tolls et al. (1997, 2000) demonstrated the closer the p-sulfophenyl moiety is positioned to the terminal carbon of the alkyl chain, the higher the BCF. However, alkyl chain length has a much bigger effect than does the phenyl position. The results show that the bioconcentration potential of LAS is low. Tolls et al. (2000) demonstrated that biotransformation of LAS occurs as a sequence of reactions, with the first step yielding the corresponding alcohol followed by two additional biotransformations to yield p-sulfophenyl-lauric acid and oxidative chain shortening. Dyer et al. (2008) confirmed this with the additional conclusion that biotransformation was mainly due to Phase-I enzymes and that efflux pumps play a critical role in loss from cells. LAS metabolites were eliminated in bile and urine suggesting activities of Phase-II enzymes. Cowan-Ellsberry et al. (2008) developed an effective physiologically constructed BCF model based partly on in vitro biotransformation studies of LAS and showed that the corresponding in vivo BCF estimates were replicated when biotransformation was included.