Benzenesulfonic acid, C10-13-alkyl derivs., sodium salts

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well documented peer-reviewed publication.

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:

SUM(Cf,j)/SUM(Cw,i)rel = SUM(ɸi,w·BCFi,rel)

“ɸ” is theta (molar concentration of each isomers (i); C is concentration in fish (f) or water (W); rel is relative.

Remarks on result:

other: not reported

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

The bioaccumulation potential of a series of LAS homologues and isomers were evaluated in flow-through studies with fathead minnows. 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).

In a supporting study, the bioconcentration of LAS in the marine shrimp Palaemonetes varians was measured in a radiotracer study.The BCF55 for shrimp was calculated to be 159 L/kg. A DT50 of 14 hrs was calculated, and only 1% of the body burden of the test substance remained in the shrimp after 8 days.

Key value for chemical safety assessment

BCF (aquatic species):

87 L/kg ww

Additional information

The bioaccumulation potential of LAS has been evaluated and found to be low based on aquatic data in fish and marine shrimp. No specific data are available for bioaccumulation in terrestrial organisms, but based on the low bioaccumulation potential in aquatic organisms, bioaccumulation is not expected.

In the key 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. 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-C10LAS) to almost 1000 L/kg (2-phenyl-C13LAS), 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 onin vitrobiotransformation studies of LAS and showed that the correspondingin vivoBCF estimates were replicated when biotransformation was included.

In a supporting study, the bioconcentration of LAS in the marine shrimp Palaemonetes varians was measured in a radiotracer study. Shrimp in seawater were exposed to radiolabelled [14C]C12-6-LAS . A first order saturation exponential modeled was used. Sorption of the test substance to the test vessel wall was negligible. Depuration kinetics were described using a one component exponential model. Body residue in shrimp was 0.64 ug/g wet weight. This is at least 40 times below the critical body burden for acute or chronic exposure.