Quaternary ammonium compounds, bis(hydrogenated tallow alkyl)dimethyl, acetates

Sediment toxicity

Administrative data

Endpoint:

sediment toxicity: long-term

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:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Results published in a scientific review and peer-reviewed in the European RAR.

Data source

Reference

Reference Type:

publication

Title:

Bioaccumulation and toxicity of a cationic surfactant (DODMAC) in sediment dwelling freshwater invertebrates

Author:

Comber S.D.W. et al.

Year:

2008

Bibliographic source:

Environmental Pollution 153 (2008) 184-191

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

other: ASTM, 2001. E1706-00e1

Deviations:

no

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Dimethyldioctadecylammonium chloride

EC Number:

203-508-2

EC Name:

Dimethyldioctadecylammonium chloride

Cas Number:

107-64-2

Molecular formula:

C38H80N.Cl

IUPAC Name:

N,N-dimethyl-N-octadecyloctadecan-1-aminium chloride

Details on test material:

Dimethyldioctadecylammonium chloride (DODMAC) is a cationic surfactant and forms a major component of the technical product dihydrogenated tallow dimethyl ammonium chloride (DHTDMAC). To facilitate the deterrnination of concentrations of DODMAC in sediment, pore water, overlying water and biota, 14C-labelled DODMAC was used (Unilever, specific activity 0.196 MBq/ mg, radiochemical purity approximately 88%). All concentrations were corrected according to the reported specific activity. The compound was labelled on the C-18 chain on the carbon adjacent to the nitrogen. Non-labelled DODMAC was also provided by Unilever with a purity of 98%.

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

Analytical determinations were made using the radio-labelled DODMAC to calculate concentrations by scaling up according to the appropriate ratio to provide concentrations of non-labelled DODMAC.

To determine possible degradation during the exposure period (up to 28 days) the sediment was removed from test vessels themselves after draining off overlying water.

Test substrate

Vehicle:

yes

Details on sediment and application:

A natural uncontaminated sediment was used. It was collected from the ARC Study Centre, Wolverton Road, Great Linford, Milton Keynes, UK. Il contained 44% sand, 48% silt and 8% clay, with a total organic carbon content of 1.7% and a cation exchange capacity of 104.5 ± 6.7 meq/kg (n = 6); the pore water dissolved organic carbon concentration was 28 ± 1.3 mg/L (n = 20). The sediment particle size ranged frorn 0 to 500 µm with the bulk
of the particles being less than 63 µm (68%). The water content of the sediment was 51 ± 2% dw (n = 6) and sediment was stored at 4 °C prior to use.

Sediment was spiked with both radio-labelled and non-labelled DODMAC. The radio-labelled DODMAC was added as a 'tracer' at specific ratios (between 1:50 and 1:125 labelled to non-labelled material) depending on the non-labelled concentration.
Dry sediment (10 g ± 1 g) was spiked with aliquots of non-labelled (200 mg/kg DODMAC in dichloromethane) and radio-labelled (90,8784 Bq/mL in methanol, specific activity 19,6000 Bq/mg) DODMAC. Sediment spiked with varying amounts of DODMAC was then left overnight in order for the solvent to evaporate. Before use, the dry sediment was diluted with 600 g of wet sediment, and mixed thoroughly for 1 h to ensure even distribution of DODMAC in the sediment. An unspiked sediment control was also prepared, as well as an unspiked solvent control, where the highest dichloromethane volume used for the toxicity tests was added to the sediment.

Test organisms

Test organisms (species):

Tubifex tubifex

Details on test organisms:

The test was based on the Standard ASTM methodology (ASTM, 2001). A wet weight of 20 g (± 1 g) of the prepared sediment (containing ca. 0- 3600 mg/kg dw DODMAC) was added to clean 60 ml glass vessels followed by 30 ml of groundwater drawn from an aquifer on-site.
Four adult T. tubifex were added to each vessel following a 24-h equilibration period. Again, the vessels were aerated for 5 min each day and the overlying water replenished with distilled water every 2 days. For each vessel pH, DO and temperature were monitored daily to ensure that DO in the overlying water did not fall below 60% and pH remained between 6 and 8.5. Each test concentration was replicated six times. Samples of sediment and overlying water were taken for analysis after 0 and 28 days. The sediment was sieved through 500- and 250-µm sieves and the sediment retained in the sieve examined under a microscope in order to obtain a count of juvenile T. tubifex. This sediment was also examined for evidence of cocoons. Adult T. tubifex retained in the 500 µm sieve were counted, and the adults blotted dry and wet weighed, with the content from two vessels of the same concentration being pooled in order to provide enough mass for an accurate wet-weight measurement. The adults were then reweighed following 48 h of air-drying to determine dry weight.

Study design

Study type:

laboratory study

Test type:

static

Water media type:

freshwater

Type of sediment:

natural sediment

Limit test:

no

Exposure duration

Duration:

28 d

Exposure phase:

total exposure duration

Test conditions

Test temperature:

20°C

pH:

pH remained between 6 and 8.5

Dissolved oxygen:

DO in the overlying water did not fall below 60%

Nominal and measured concentrations:

Nominal DODMAC concentrations between 0 and 5000 mg/kg dw.

Details on test conditions:

The sediment:water partition coefficient (Kp) was calculated as 3428 l/kg which confirmed the consistency in the physico-chemical nature of the freshwater sediment, and the spiking and test methodology. By normalising the Kp to the organic carbon content of the sediment (1.7%) a log Koc value of 4.85 may be derived, which is consistent with the fate and behaviour of DODMAC reported elsewhere (EU RAR, 2002). Concentrations in the aqueous phases attained equilibrium within 16 days and remained stable thereafter, with measured concentrations in the µg/L range. HPLC analysis of the parent compound confirmed that there was no measurable degradation over the duration of any of the toxicity tests, again consistent with other reports of sediment half-lives (EU RAR, 2002).

All tests were carried out at 20°C under 18 h of light and 6 h of darkness lighting conditions. Daily measurements of pH, dissolved oxygen and conductivity were made to ensure consistency of exposure conditions.

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

28 d

Dose descriptor:

EC10

Effect conc.:

550 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

other: number of juveniles

Remarks on result:

other: 95% CL: 336-1400

Effect concentrations 2

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

1 515 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

other: number of juveniles

Effect concentrations 3

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

3 898 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

other: survival and body weight of adult worms

Details on results:

There was no statistically significant difference between survival of the adult T. tubifex in the controls and any of the DODMAC spiked concentrations (one-way ANOVA, Fconc = 1.32, Fcrit = 2.37, df = 6,35; at the 5% level of significance).
Lethal effect concentrations for T. tubifex are therefore greater than 3897 mg/kg dw DODMAC (mean of day 0 and day 28 data) in sediment. The relationship between DODMAC sediment concentration and the dry weight of T. tubifex at the end of the test was analysed to assess potential effects on sub-lethal effects such as growth. There was no statistically significant difference between the mass of adult worms in the controls compared with any of the spiked sediment concentrations (one-way ANOVA,Fconc = 1.16, Fcrit = 2.85, df = 6,14; at the 5% level of significance). It was therefore concluded that a concentration greater than 3898 mg/kg dw DODMAC (mean of measured day 0 and day 28 concentrations) would be needed in order to have an effect on the growth of adult T. tubifex.
Sub-lethal effects were, how ever, observed for juvenile numbers, with increasing sediment DODMAC concentration. A NOEC of 1515 mg/kg dw of DODMAC was calculated, as well as a LOEC of 2484 mg/kg dw DODMAC. A mean EC 10 of 555 mg/kg dw (336- 1400 mg/kg dw, based on 95% CL - skewed distribution) and EC50 of 3022 mg/kg dw DODMAC were calculated using a linear interpolation model. The wide confidence intervals were a resultof large variance in the number of juveniles in each vessel.

Reported statistics and error estimates:

A paired t-test showed that there was no significant difference between the solvent controls and the control samples at the 95% level, and as a result the data were pooled.

Applicant's summary and conclusion

Conclusions:

NOEC (number of juveniles): 1515 mg/kg dw
LOEC of(number of juveniles): 2484 mg/kg dw
Mean EC10: 550 mg/kg dw
Mean EC50: 3022 mg/kg dw

Executive summary:

The toxicity of DODMAC to the oligochaete Tubifex tubifex was assessed using a 28d sediment bioassay (Comber et al., 2008) and a natural sediment (organic carbon content: 1.73 %). A mixture of radio-labelled and non-labelled DODMAC was used for the experiment and the analytical determinations were made using the radio-labelled DODMAC. 4 adult worms per test vessel (6 vessels per concentration) were exposed to the spiked sediment containing nominal DODMAC concentrations between 0 and 5,000 mg/kg dw. The examined endpoints were survival of the worms, number of juveniles and body weight. At the end of the test samples of overlying water and sediment were taken for analysis. The measured sediment concentrations ranged between 224 mg/kg dw and 3600 mg/kg dw. All effect values were related to the measured concentrations.

Up to the highest test concentration no effects on the survival of Tubifex were observed. Also in the dry weight of the adult worms no statistically significant difference was found between the control and the worms exposed to DODMAC. However, for the endpoint number of juveniles, a concentration effect was observed. A NOEC of 1515 mg/kg dw and a LOEC of 2484 mg/kg dw was found. Using a linear interpolation method, a mean EC10 of 550 mg/kg dw and an EC50 of 3022 mg/kg dw was calculated.