Octadecan-1-ol, ethoxylated

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: Acceptable, well documented publication which meets basic scientific principles

Qualifier:

no guideline followed

Principles of method if other than guideline:

Fish were exposed in a flow-through system to the test substance during an uptake phase of up to 72 h. The following elimination phase lasted for 24 h.

GLP compliance:

no

Radiolabelling:

no

Vehicle:

no

Test organisms (species):

Pimephales promelas

Details on test organisms:

TEST ORGANISM
- Common name: fathead minnow
- Source: hatchery of Utrecht University, The Netherlands
- Weight at study initiation (mean and range, SD): 0.5 - 1.0 g

ACCLIMATION
- Acclimation period: at least 1 week
- Type and amount of food: Lapis dry feed at a rate of 1% of body weight
- Feeding frequency: daily

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

natural water: freshwater

Total exposure / uptake duration:

54 - 72 h

Total depuration duration:

24 h

Test temperature:

20.7 - 22.5 °C

Details on test conditions:

TEST SYSTEM
- Test vessel: 5 - 8 L aquaria
- No. of organisms per vessel: 30


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstituted freshwater was prepared by dissolving 0.75 mM CaCl2 x 2H2O, 0.46 mM MgSO4 x 7H2O, 1.51 mM NaHCO3, 0.04 mM KH2PO4, 1.01 mM NaNO3 and 0.10 mM Na2SiO3 in distilled water.

Nominal and measured concentrations:

The AE concentrations were higher than the critical micelle concentration. 0.029 µM steady state concentration of the test compound in water

Reference substance (positive control):

no

Lipid content:

0.9 - 8.2 %

Time point:

start of exposure

Remarks on result:

other: average content: 4.9%

Type:

BCF

Value:

12.7 L/kg

Basis:

not specified

Time of plateau:

24 h

Calculation basis:

steady state

Remarks on result:

other: for C12EO8

Remarks:

Conc.in environment / dose:0.570 µM steady state concentration of the test compound in water

Type:

BCF

Value:

237 L/kg

Basis:

not specified

Time of plateau:

24 h

Calculation basis:

steady state

Remarks on result:

other: for C14EO4

Remarks:

Conc.in environment / dose:0.029 µM steady state concentration of the test compound in water

Type:

BCF

Value:

387.5 L/kg

Basis:

not specified

Time of plateau:

24 h

Calculation basis:

steady state

Remarks on result:

other: for C16EO8

Remarks:

Conc.in environment / dose:0.033 µM steady state concentration of the test compound in water

Type:

BCF

Value:

232.5 L/kg

Basis:

not specified

Time of plateau:

24 h

Calculation basis:

steady state

Remarks on result:

other: for C13EO4

Remarks:

Conc.in environment / dose:0.236 µM steady state concentration of the test compound in water

Details on results:

- Mortality of test organisms: no mortality was observed
- Behavioural abnormalities: no signs of sublethal effects, such as swimming or breathing behavior, were observed during the experiments.

The test substance was not stored inside fish and no relationship between BCF and lipid content was observed. The elimination rate suggested rapid biotransformation of the test substance.

Description of key information

Alcohol ethoxylates are not expected to bioaccumulate due to a rapid biotransformation and excretion.

Additional information

The bioaccumulation potential of alcohol ethoxylates fish (Fathead minnow) was extensively investigated and in flow-through experiments by Tolls (1998) and Tolls et al. (2000). The BCFs, reported in the publication ranged between <5 and 387.5 L/kg. For the uptake rate constant (k1) a range of 330 - 1660 (L/kg per day) was reported; the determined elimination rate constant (k2) ranged from 3.3 - 59 L/kg per day. According to the authors, the uptake rate constant and the BCF increase with increasing chain length of alkyl chain. Whereas an increase in the length of the ethoxylate chain reduces the bioaccumulation potential. The elimination rate constant decreases with increasing alkyl chain length and decreasing ethoxylate chain length. A decrease in the elimination rate constant was correlated with increasing alkyl chain length and decreasing ethoxylate chain length. The results indicate a rapid biotransformation of alcohol ethoxylates.

In a publication by Dyer et al. (2008) the biotransformation of two surfactants, i.e. C12-2-LAS and C13EO8, was tested in subcellular and cellular hepatic systems. Liver homogenates and microsomes from the common carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss) were used as subcellular systems. The cellular systems consisted of primary hepatocytes from the common carp (Cyprinus carpio) and PLHC-1 cells, and hepatocarcinoma cells from the clearfin livebearer (Poeciliopsis lucida). All in vitro systems were exposed to radiolabelled test compounds and assayed for biotransformation using liquid scintillation and thin layer chromatographic methods. Predicted BCF-values corresponded closely to measured values in several fish species, verifying the utility of in vitro systems in refining Kow-only-based BCFs via the inclusion of biotransformation rates. Resulting from that study biotransformation of C13EO8 could be demonstrated with both, primary hepatocytes and PLHC-1 cells, although with different metabolic profiles. First-order in vitro clearance rates based on exposure of C13EO8 to rainbow trout and carp microsomes and primary hepatocytes from carp lead to predicted BCF-values which were below 98 for all test systems.

Munoz et al. (2010), performed in-vivo experiments investigating the uptake and elimination kinetics of pure homologues of linear alcohol ethoxylates. The bioconcentration (BCF), biotransformation (identification of the metabolites generated by an organism), and depuration at different exposure levels was determined. Steady state BCF-values ranged from 99.4 to 130 L/kg/d for the tested alcohol ethoxylates. For C12EO6 the rate of uptake (k1) ranged from 63.2 to 122.6 L/kg/d. The rate of uptake was not affected by the exposure concentration. For the rate of elimination (k2) the results showed a very slight decrease with increasing exposure level. As internal degradation products in fish, the glucuronic conjugate of alcohol ethoxylates was detected. The results suggest that predominant biotransformation process for alcohol ethoxylates is a phase II biotransformation. Although the depuration percentage was very high at the beginning of the elimination phase, a slight increase was observed over time. Alcohol ethoxylates were considered to have a delayed elimination and potential of short-term bioaccumulation (Beek, 2000).

 

The common principle of the biotransformation of surfactants is either an enzymatic cleavage of the two surfactant molecule moieties (forming a fatty alcohol/acid and a hydrophilic product) or is a terminal oxidation and subsequent stepwise degradation of the alkyl chain (leaving again a hydrophilic product). The metabolism of the surfactant alkyl chain through a combination of omega- and beta-oxidations with subsequent excretion of a short chain derivative has been demonstrated for several fish species (Newsome et al., 1995; Van Egmond et al. 1999).

 

In conclusion, bioconcentration factors of alcohol ethoxylates in the aqueous phase are below the level of concern, and can be quantitatively related to the length of the hydrophobic and hydrophilic components. There is also evidence that overall molecular size may place constraints on biological uptake. The cited studies cited indicate no to long-term retention of accumulated surfactant material in tissue. The studies provide clear evidence that alcohol ethoxylates are rapidly eliminated and metabolised. Although the fate of metabolites of AE has not been thoroughly studied, rapid biodegradation of alcohol ethoxylates in the aquatic environment is considered to be a mitigating aspect, since the rate of biodegradation of alcohol ethoxylates are significantly faster than the uptake rates of bioaccumulation. 

 

 

References:

Dyer, S. D., Bernhard, M. J., Cowan-Ellsberry, C. C., Perdu-Durand, E., Demmerle, S. and Cravedi, J.-P. (2008): In vitro biotransformation of surfactants in fish. Linear alkylbenzene sulfonate (C12 -LAS) and alcohol ethoxylate (C13EO8).Chemosphere 72, 850 -862.

Munoz DA, Gomez-Parra A and Gonzalez-Mazo E (2010) Influence of the molecular structure and exposure concentration on the uptake and elimination kinetics, bioconcentration, and biotransformation of anionic and nonionic surfactants, Environ. Toxicol. Chem, 29 (8): 1721-1734

Newsome, C. S., Howes, D., Marshall, S. J. and Van Egmond, R. A. (1995): Fate of some anionic and alcohol ethoxylate surfactants in Carassius auratus. Tenside Surfact. Deter. 32, 498 -503.

Van Egmond, R., Hambling, S. and, S. (1999): Bioconcentration, biotransformation, and chronic toxicity of sodium laurate to zebrafish (Danio rerio).