Decyl laurate

Sediment toxicity

Link to relevant study record(s)

Reference

Endpoint:

sediment toxicity: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 Oct - 02 Dec 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 218 (Sediment-Water Chironomid Toxicity Test Using Spiked Sediment)

Deviations:

yes

Remarks:

The total organic carbon content of the final sediment mixture was 2.89% (requirement: 2.0 ± 0.5%). This must be considered for interpretation of results.

GLP compliance:

yes (incl. QA statement)

Remarks:

The Department of Health of the Government of the United Kingdom (15 Nov 2016)

Analytical monitoring:

yes

Remarks:

HPLC/GC-MS

Details on sampling:

- Concentrations: All test item concentrations were analytically verified in overlying water samples (HPLC) and sediment samples (GC-MS) for all treatments on Days 0, 7 and 28.
- Sampling interval: On Day -7 samples were taken of the sediments as dispensed to the test vessels. On Days 0 and 7, one assigned, sacrificial replicate of the control, solvent control and test concentration was sampled. On Day 28, single test replicates were sampled after checking for the presence of test organisms. For the water samples, the aqueous layer from the top of the vessel was decanted into 3 x 35 mL PTFE centrifuge tubes (full to the top). Sediment samples were accurately weighed out into a pre-weighed 250 mL centrifuge bottle containing 50 mL acetone.

SEDIMENT
- Concentrations: Control, solvent control and each test item treatment.
- Sampling interval: Day -7 (start of equilibration), Day 0 (test start), Day 7, Day 28 (test end)

OVERLYING WATER
- Concentrations: All concentrations.
- Sampling interval: Days 0, 7 and 28

Vehicle:

yes

Remarks:

Tetrahydrofuran (THF)

Details on sediment and application:

PREPARATION OF SPIKED SEDIMENT
- Details of spiking: A proportion (50%) of the dry sand component of the sediment for each treatment was added to a glass crystallising dish. Each sand aliquot received 10 mL test item in solvent (Tetrahydrofuran), such that the nominal sediment concentration was supplied. All stock solutions were clear and colourless. The stock solutions were pipetted onto the surface of the sand.
- Pooling or mixing of different substrates: After evaporation of the solvent carrier from the sand component, the remaining quantitiy of sand plus the kaolinite clay, conditioned peat and reconstituted water components of the sediment were mixed in individual bottles. The amount of reconstituted water added to the sediment was that which liquefied it sufficiently to obtain good mixing on a tumble mill, using known and (pro-rata) equal additions to all bottles.
- Method of mixing: The contents of the bottles were mixed on a tumble mill overnight before being dispensed to the test vessels.
- Equilibration time: 7 d
- Equilibration conditions: For each treatment, approximately 140 g wet weight of the spiked sediment was weighed into each test and analytical replicate vessel. Reconstituted water was added to all vessels to a total volum of 400 mL, minimising disturbance of the sediment. After a period of settlement, the test vessels were provided with gentle aeration (as to be employed during the animal exposure).
- Controls: Control (reconstituted water without solvent or test item) and solvent control (same volume of solvent without test item)
- Chemical name of vehicle: Tetrahydrofuran (THF)
- Concentration of vehicle in test medium: 0.008 mL/g sediment dw
- Evaporation of vehicle before use: Yes, the solvent was allowed to evaporate overnight in a fume hood.

Test organisms (species):

Chironomus riparius

Details on test organisms:

TEST ORGANISM
- Common name: Midge fly larvae (harlequin fly)
- Details on test organism: C. riparius is distributed throughout North America and Europe in a wide variety of freshwater habitats. The larvae construct and live in tubes within sediments. After 4 larval stages the larvae pupate and the pupae rise to the surface where the adult insects emerge. Adults mate and egg ropes are laid in water within a few days.
- Source: Continuous in-house laboratory cultures
- Breeding conditions: Same as test
- Age of animals at beginning of exposure: Less than 48 h post hatch at the start of the test
- Feeding during breeding and test: Once daily with finely ground Aquarian Tropical Fish Flakes prepared as suspension in reverse osmosis water. The Aquarian suspension was prepared weekly and was stored under refrigeration.
- Feeding rates: 0.50 mg/animal/day (0 - 6 d), 1.0 mg/animal/day (7 - 13 d), 0.50 mg/animal/day (14 - 20 d), 0.25 mg/animal/day (21 - 27 d), and 0 mg/animal/day (Day 28)

Study type:

laboratory study

Test type:

static

Water media type:

freshwater

Type of sediment:

artificial sediment

Remarks:

Reconstituted sediment with an organic carbon content of 2.89% equilibrated with overlying water for 7 d prior test start.

Limit test:

no

Duration:

28 d

Exposure phase:

total exposure duration

Hardness:

72.5 - 78.5 mg CaCO3/L (overlying water Day 0)
50.5 - 75.5 mg CaCO3/L (overlying water Day 28)

Test temperature:

19.8 - 20.2 °C (overlying water, Day 0 - Day 28)

pH:

7.35 - 8.22 (overlying water, Day 0 - Day 28)

Dissolved oxygen:

94 - 105 % ASV (Air Saturation Value, overlying water, Day 0 - Day 28)
8.55 - 9.56 mg/L (overlying water, Day 0 - Day 28)

Ammonia:

0.010 - 0.132 mg/L NH4 (Day 0)
0.083 - 0.134 mg/L NH4 (Day 28)

Conductivity:

282 µS/cm (reconstituted, overlying water)

Nominal and measured concentrations:

Control, solvent control, 62.5, 125, 250, 500 and 1000 mg/kg sediment dw (nominal)
Control, solvent control, 39.7, 81.3, 176, 383, and 787 mg/kg sediment dw (mean measured)

Details on test conditions:

TEST SYSTEM
- Test container: Glass beakers fitted with lids consisting of inverted plastic beakers (400 mL capacity) with meshed air vents acting as traps to retain emerged adults.
- Sediment volume: The initial sediment depth was approximately 2 cm.
- Weight of wet sediment with and without pore water: 140 g (nominal wet weight)
- Overlying water volume: 400 mL
- Depth of sediment and overlying water: 2 cm sediment depth and 5.5 cm water depth
- Aeration: Yes, after a period of settlement of disturbed sediment, gentle aeration was supplied by a capillary tube positioned such as to minimise disturbance of the sediment .
- Replacement of evaporated test water, if any: The water level was marked on each vessel, so that any evaporative loss could be replaced during th study with reverse osmosis (RO) water.
- Other: No floating particulates were observed on the surface of the overlying water. Test vessels were positioned randomly by rows within the testing area. Additional sacrificial replicates were deployed for chemical analyses on exposure Days 0, 7 and 28.

EXPOSURE REGIME
- No. of organisms per container (treatment): 20
- No. of replicates per treatment group: 4
- No. of replicates per control / vehicle control: 4
- Feeding regime: Once daily
- Type and preparation of food: Aquarian Tropical Fish Flakes prepared as suspenion in reverse osmosis water
- Amount of food: 0.25 - 1.0 mg/animal/day
- Other: At the start of the test, 20 larvae (< 48 h post-hatch) were impartially allocated to each test replicate vessel. Larvae were transferred from a stock, in replicates of 10 using a pipette and placed into a disposable weighing boat. These were then washed into the test vessels with the minimum volume of test reconstituted water.

RENEWAL OF OVERLYING WATER
- Details on volume additions: The overlying water was not renewed during the test, but volumes (20 mL) removed for dissolved oxygen and pH determinations after the start of the test were replaced with fresh medium.

OVERLYING WATER CHARACTERISTCS
- Type of water: Reconstituted water prepared using reverse osmosis water from testing facility
- Location: Scymaris Ltd
- Quantities of chemicals used to prepare medium (reconstituted, overlying water) from reverse osmosis water: 96.0 mg/L NaHCo3, 60.0 mg/L CaSO4.2H2O, 122.5 mg/L MgSO4.7H2O, 4.0 mg/L KCl
- Facility background data for reconstituted (overlying) water: pH: 8.10; Conductivity: 282 µS/cm; Total hardness as CaCO3: 77.3 mg/L; Suspended solids at 105 °C: < 3.0 mg/L; Total organic carbon: < 0.7 mg/L; Chemical oxygen demand: < 10.0 mg/L; Ammoniacal nitrogen as N: < 0.002 mg/L; Highest organophosphorous pesticides: < 0.01 µg/L; Highest organochlorine pesticides: < 0.01 µg/L; Highest PCB: < 0.002 µg/L; Aluminium: < 10.0 µg/L; Arsenic: < 1 µg/L; Boron: < 100 µg/L; Cadmium: < 0.1 µg/L; Chromium: < 0.5 µg/L; Cobalt: < 1 µg/L; Copper: < 1 µg/L; Iron: < 30 µg/L; Lead: < 2 µg/L; Manganese: < 10 µg/L; Mercury: < 0.01 µg/L; Nickel: < 1 µg/L; Silver: < 1 µg/L, Zinc: < 5 µg/L

CHARACTERIZATION OF ARTIFICIAL SEDIMENT
- % dry weight of sphagnum moss peat: 5 (dw)
- % Quartz sand: 75 (dw )
- % Kaolinite clay: 20 (dw)
- Composition: Sand, kaolinite, calcium carbonate and finely sieved sphagnum moss peat
- Method of preparation: The peat was air dried and sieved to < 1 mm. The required amount of peat was mixed with an appropriate amount of calcium carbonate and sufficient reverse osmosis water to form a suspension. Following stirring overnight, the pH of the suspension was 6.25 (this is higher than the required 5.5 ± 0.5 but was deemed acceptable as the pH after conditioning was required to be 6.0 ± 0.5). After removal of floating material and the addition of further dilution water, the suspension was conditioned with gentle stirring for at least 2 d at 20 ± 2 °C to stabilise the pH. The pH was measured again and was 6.17 which is within the acceptable pH of 6.0± 0.5. Floating material and excess water were removed to obtain a homogeneous peat slurry.
- Moisture: 86%
- Other: The final peat slurry was stored in a sealed container under refrigeration for 5 d before use.
- Total organic carbon (%): 2.89% (According to the OECD test guideline, 5% peat should provide a final organic carbon level of approximately 2.0 ± 0.5%)

OTHER TEST CONDITIONS
- Photoperiod: 16 h light and 8 h dark with 20 min dawn and dusk transition periods
- Light intensity: 845, 1070, and 1080 lux (cosine, on Days -7, 0 and 28, respectively)

EFFECT PARAMETERS MEASURED:
- Total time to emergence
- Total number of emerged adult insects: Daily
- Sex ratio of emerged adult insects: Daily
- Visual assessment of test vessels: 3 times per week

VEHICLE CONTROL PERFORMED: Yes

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2

Reference substance (positive control):

no

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 787 mg/kg sediment dw

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

emergence rate

Remarks:

and sex ratio

Reported statistics and error estimates:

Statistical analyses were performed with Minitab packed. The following tests were used to compare the recorded effects on "Total number emerged after 28 d" and "Sex Ratio" in the control, solvent control and treatments: Fisher's Exact test, Bonferroni adjustment. The following tests were used to compare the recorded effects on "Deveopment Rates" in the control, solvent control and treatments: Two sample t-test, Barlett's test, ANOVA followed by Dunnett's.

VALIDITY CRITERIA

The study fulfilled the validity criteria defined by the guideline (Table 1) and is thus considered reliable and valid.

 

Table 1. Validity criteria for OECD 218.

Criterion from the guideline	Outcome	Validity criterion fulfilled
The emergence in the control must be at least 70% at the end of the test.	The emergence in the control and solvent was 93 and 89%, respectively.	Yes
C. riparius and C. yoshimatsui emergence to adults from control vessels should occur between 12 and 23 d after their insertion into the vessels.	Emergence occurred between Days 15 – 23.	Yes
At the end of the test, pH and the dissolved oxygen concentration should be measured in each vessel. The oxygen concentration should be at least 60% of the air saturation value (ASV) at the temperature used and the pH of the overlying water should be in the 6-9 range in all test vessels.	pH on Day 28 ranged from 7.35 to 7.94 and dissolved oxygen ranged from 94 to 105% ASV.	Yes
The water temperature should not differ by more than ± 1.0 °C.	Water temperature varied only by ± 0.2 °C.	Yes

 

ANALYTICAL RESULTS

SEDIMENT

The measured test item concentrations in sediment are summarized in Table 2. The limit of quantification is provided in Table 3.

The measured concentrations for the wet sediment at the start of the equilibration period (Day -7) ranged from 90 – 95% of the nominal values. On Day 0, the total recoveries from the sediment fraction ranged from 67 – 80% of nominal. On Day 7, the total recoveries from the sediment fraction ranged from 61 – 88% of nominal. On Day 28, the total recoveries for the sediment fraction ranged from 40 to 59% of nominal.

 

Table 2. Summary of analytical data from sediment analysis.

Nominal test item concentration [mg/kg]	Measured concentration of test item in sediment								Geom. mean measured	Geom. mean measured
	Day -7		Day 0		Day 7		Day 28
	[mg/kg]	[% of nominal]	[mg/kg]	[% of nominal]	[mg/kg]	[% of nominal]	[mg/kg]	[% of nominal]	[mg/kg]	[% of nominal]
Control	< LOQ	-	< LOQ	-	< LOQ	-	< LOQ	-	0	-
Solvent control	< LOQ	-	< LOQ	-	< LOQ	-	< LOQ	-	0	-
62.5	59.5	95	43.9	70	37.9	61	25.2	40	39.7	64
125	112^A	90	83.5^B	67	84.5^C	68	55.4^D	44	81.3	65
250	229	92	198	79	184	74	114	46	176	70
500	457	91	402	80	406	81	287	57	383	77
1000	930	93	789	79	880	88	593	59	787	79

A Mean of triplicate analyses: 114, 111, 111 mg/kg

B Mean of triplicate analyses: 95.8, 90.1, 64.7 mg/kg

C Mean of triplicate analyses: 83.8, 89.0, 80.7 mg/kg

D Mean of triplicate analyses: 57.2, 56.6, 52.3 mg/kg

 

OVERLYING WATER

All the overlying water samples contained < LOQ test item on Days 0, 7 and 28.

 

On the basis of the analytical data, effect concentrations were based on the geometric mean measured concentrations.

 

Table 3. Limits of Quantification for sediment analysis

nominal test item concentration	Dilution factors	Day -7 LOQ	Day 0 LOQ	Day 7 LOQ	Day 28 LOQ
[mg/kg]		[mg/kg]	[mg/kg]	[mg/kg]	[mg/kg]
Control	1	0.83	1.49	1.54	0.76
Solvent control	1	0.81	1.51	1.51	0.77
62.5	10	8.08	15.05	15.03	7.76
125	20	16.13 – 16.25	30.15 – 55.31	30.53 – 52.41	15.40-25.88
250	40	32.33	60.33	60.42	31.75
500	100	81.57	151.38	148.99	77.76
1000	200	167	300.12	313.28	138.70

LOQ = limit of quantification

 

BIOLOGICAL RESULTS

The visual observations of the test vessels showed no differences between treatments. A summary of emergence and sex ratio data is provided in Table 4.

 

EMERGENCE AFTER 28 d

After 28 d adult emergences in the control and solvent control were 93% and 89%, respectively. No significant difference was found between the controls. All subsequent comparisons were performed against the solvent control.

No significant effects on total emergence was found in any treatment compared to the control. The obtained effect concentrations are summarized in Table 4.

 

SEX RATIO

In the control and solvent control, 49 and 44% males were recorded, respectively, thus yielding the the expected ratio close to 50:50. No significant difference was detected between the control and solvent control. All subsequent comparisons were performed against the solvent control.

No significant difference in sex was found in any treatment compared to the control. The obtained effect concentrations are summarized in Table 5.

 

TIME TO FIRST EMERGENCE

The mean times to first emergence for all test treatments ranged from 15 to 17 days. The mean time to first emergence for the control was 15 days and the solvent control was 15.5 days.

This data was not statistically analyzed.

 

Table 4. Summary of emergence data.

Nominal test item concentration	Geom. mean measured test item concentration	Replicate	Time to 1^stemergence	Mean emergence time	Replicate mean development rate	Number emerged after 28 d	Mean males per treatment
[mg/kg]	[mg/kg]		[d]	[d]	[per day]		[%]
Control	-	A	15	16.4	0.06321	19	49
		B	15	16.6	0.06275	20
		C	15	16.6	0.06255	18
		D	15	16.6	0.06235	17
		Mean	15.0	16.5	0.06272	18.5
Solvent control	-	A	17	18.6	0.05537	19	44
		B	15	17.0	0.06096	17
		C	15	16.9	0.06155	17
		D	15	17.4	0.06001	18
		Mean	15.5	17.5	0.05947	17.8
62.5	-	A	16	18.7	0.05566	18	55
		B	15	17.2	0.06048	19
		C	15	17.1	0.06115	20
		D	16	16.7	0.06173	19
		Mean	15.5	17.4	0.05976	19
125	-	A	15	16.9	0.06156	19	52
		B	15	16.9	0.06143	19
		C	16	17.7	0.05863	20
		D	15	16.6	0.06232	21
		Mean	15.3	17.0	0.06099	19.8
250	-	A	16	17.7	0.05868	20	43
		B	15	17.5	0.05946	18
		C	16	17.1	0.06072	18
		D	16	17.7	0.05889	20
		Mean	15.8	17.5	0.05944	19.0
500	-	A	16	18.3	0.05675	18	48
		B	17	17.9	0.05780	20
		C	15	17.5	0.05951	19
		D	16	18.2	0.05720	19
		Mean	16.0	18.0	0.05782	19
1000	-	A	16	19.1	0.05437	18	55
		B	16	17.7	0.05881	18
		C	16	17.9	0.05762	19
		D	16	18.3	0.05650	18
		Mean	16.0	18.3	0.05682	18.3

 

Table 5. Effect concentrations for emergence and sex ratio.

NOEC (28 d)	>= 787 mg/kg
LOEC (28 d)	> 787 mg/kg

 

 

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Description of key information

NOEC (28 d) ≥ 787 mg/kg sediment dw (geom. mean measured, OECD 218, C. riparius)

Additional information

One experimental study is available, in which the long-term toxicity ofdecyl laurate (CAS 36528-28-6) to sediment organisms was assessed according to OECD guideline 218 and GLP.

A static sediment-freshwater toxicity test was performed in which the model organism Chironomus riparius, a widespread sediment-dwelling midge in freshwater habitats, was exposed to the nominal test item concentrations of 62.5, 125, 250, 500 and 1000 mg/kg sediment dry weight for 28 d via spiked artificial soil. A sediment spiking method was selected because the most likely entry route into the aquatic environment is expected to occur via particulate material carrying adsorbed substance. The artificial sediment was formulated from sand, kaolinite, calcium carbonate and finely sieved sphagnum moss peat according to the guideline, resulting in a final organic carbon content of 2.89%, slightly above the 2.0 ± 0.5%, as recommended by the guideline. Nevertheless, the organic matter content of 4.93% is nearly in line with the recommendations given in ECHA Guidance R.7b (5%; ECHA, 2017). The sediment was spiked by adding 10 mL of the test substance dissolved in the solvent Tetrahydrofuran to the dry sand component of the sediment only, which was allowed to evaporate overnight. Subsequently, all sediment components were combined, liquefied with reconstituted water and mixed on a tumble mill overnight. The spiked sediment was then dispensed to the test vessels, covered with overlying water (reconstituted) and allowed to equilibrate for 7 d prior test start. A control and solvent control (Tetrahydrofuran) were included in the test design. The measured endpoints included effects of the test item on larval development and emergence, effects on the sex ratio of emerged adult insects, development rates and on the time to first emergence. The actual test item concentrations in the sediment and overlying water were analytically verified by GC-MS/HPLC on Day -7 (for sediment only), 0, 7 and 28.

The measured test item concentrations in wet sediment was 90 – 95% of nominal on Day -7, 67-80% of nominal on Day 0, 61 – 88% on Day 7 and 40 – 59% on Day 28. The measured test item concentrations in the overlying water was < LOQ on Day 0, 7 and 28. Based on these findings, the effect values were based on the geometric mean measured test item concentrations in the sediment, resulting in test item exposure concentrations of 39.7, 81.3, 176, 383 and 787 mg/kg sediment dry weight.

At the end of the test, no statistical differences between the control and solvent control was found for any endpoint and all statistical comparisons were made against the solvent control. After 28 d exposure, no significant differences between the total emergence of adults, sex ratio and development rates in the treatments and solvent control were found. The mean times to first emergence ranged from 15 to 17 d, which was similar to that of the controls (15 and 15.5 d, respectively) but was not statistically analyzed.

Thus, the test resulted in an overall NOEC (28 d) of ≥ 787 mg/kg sediment dw (highest exposure concentration) based on development rates, total number of emerged adult insects and their sex ratio. The LOEC (28 d) was > 787 mg/kg sediment dw for all endpoints.