(Z)-N-octadecyldocos-13-enamide

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

03 Dec 2019 to 16 Jun 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 305 (Bioaccumulation in Fish: Aqueous and Dietary Exposure) -III: Dietary Exposure Bioaccumulation Fish Test

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Details on sampling:

- Sampling intervals/frequency for test organisms: Exposure phase day 0, 14, Depuration phase day 1, 4, 7, 21 and 28
- Sampling intervals/frequency for test medium samples: Exposure phase day 0, 14, Depuration phase day 1, 4, 7, 21 and 28
- Sample storage conditions before analysis: Frozen (temperature not measured)
- Details on sampling and analysis of test organisms and test media samples (e.g. sample preparation, analytical methods): Fish were homogenised by mincing with scissors. At least triplicate aliquots were taken for analysis by combustion and radioassay. The samples were stored at -10 °C to -30 °C following analysis.
The pooled extracts were analyzed by reverse phase high performance liquid chromatography (HPLC) or normal phase thin-layer chromatography (TLC).

Vehicle:

yes

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

A portion of test item stock solution (15.46 mg, 56.17 MBq) was transferred in portions to a glass vial and evaporated to dryness under nitrogen. A portion (3 mL) of corn oil was added to the vial and solid was dissolved by sonication (15 minutes). Duplicate aliquots (10 µL) were removed from the corn oil and diluted to volume (5 mL) with THF. Duplicate aliquots (100 µL) were taken for radioassay. A portion (2.33 mL) of the treated oil was added to 120.04 g of feed, which was manually shaken followed by rotational agitation for five minutes. This shaking and agitation was repeated a total of six times. Five weighed aliquots (approximately 0.02 g) were removed for assessment of homogeneity by combustion and radioassay.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Source: Brow Well Fisheries Limited
- Length at study initiation (length definition, mean, range and SD): mean 7.9 cm
- Weight at study initiation (mean and range, SD): mean 4.40 g, range 3.5 g to 5.00 g
- Feeding during test: daily
- Food type: commercial trout pellets
- Amount: 4.25 g


ACCLIMATION
The fish were acclimatized in holding tanks for a period of at least 2 weeks and fed commercial trout pellets. No mortality was observed during the acclimatization period.

Route of exposure:

feed

Justification for method:

minimised test method used to support BCF estimates based on QSAR

Remarks:

This method was chosen due to the high adsorption potential and low water solubility of the substance. Thus, the dietary route is the main route of exposure.

Test type:

flow-through

Water / sediment media type:

natural water: freshwater

Total exposure / uptake duration:

14 d

Total depuration duration:

28 d

Hardness:

112 mg CaCO3

Test temperature:

13.7 – 14.3 °C

pH:

7.8 – 8.3

Dissolved oxygen:

9.4 – 10.5 mg/L (91 – 102% ASV)

Details on test conditions:

TEST SYSTEM
- Test vessel: Two glass aquaria (one test and one control), fitted with overflows to maintain a volume of approximately 100 liters, were set up with a continuous flow through of approximately 1152 liters per day (nominal flow rate 800 mL/minute).
- Type (delete if not applicable): closed
- Aeration: yes
- No. of organisms per vessel: 50
- No. of vessels per concentration (replicates): 1
- No. of vessels per control / vehicle control (replicates): 1


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tap water UK
- Metals: Copper = 0.0764 mg/L, Lead < 1.5 µg/L, Nickel = 4.6 µg/L
- Pesticides < 0.004 µg/L
- Chloride: 26.28 mg/L

OTHER TEST CONDITIONS
- Photoperiod: 16 hours light and 8 hours darkness with 20 minute dawn and dusk transition periods
- Light intensity: 841 to 899 Lux
- For OECD 305 part III (dietary exposure fish bioaccumulation), overall daily feeding rate used in the study: 2% bodyweight under dynamic (continuous flow) test conditions
- For OECD 305 part III (dietary exposure fish bioaccumulation), number of feeds per day (number of feeds daily ration split between): 1
- For OECD 305 part III (dietary exposure fish bioaccumulation), overall lipid content of spiked food before test start taking into account the contribution from the corn oil vehicle, if used: not specified
- For OECD 305 part III (dietary exposure fish bioaccumulation), overall lipid content of spiked food after end of exposure taking into account the contribution from the corn oil vehicle, if used: 18% lipid food content

RANGE-FINDING / PRELIMINARY STUDY
- Test concentrations: 10 µg/g,100 µg/g, 500 µg/g and 1000 µg/g in corn oil
- Results used to determine the conditions for the definitive study: A concentration of 100 µg/g feed was chosen for the main test, as this was the highest concentration tested at which no adverse effects were observed, all food was consumed and accumulated levels of radioactivity were sufficient to monitor 95% reduction in body burden.

Nominal and measured concentrations:

Recovery express as % sample radioactivity:
D14 Uptake: 115%
D1 Depuration: 91.5%
D4 Depuration: 112.1%
D7 Depuration: 101.2%
D21 Depuration: 115.8%
D28 Depuration: 75.5%

Reference substance (positive control):

no

Details on estimation of bioconcentration:

BMF is derived based on the kinetic biomagnification factor.

Lipid content:

>= 3.06 - <= 3.89 %

Time point:

end of exposure

Conc. / dose:

0.775 other: µg/g

Temp.:

ca. 14 °C

pH:

7.8

Type:

BMF

Value:

0.056 dimensionless

Basis:

normalised lipid fraction

Calculation basis:

kinetic, corrected for growth

Elimination:

yes

Parameter:

DT50

Depuration time (DT):

0.46 d

Rate constant:

growth-corrected half-life (d)

Value:

0.455

Metabolites:

Up to five unidentified metabolites were observed in addition to test item. Two major unknown metabolites increased to >10% of the sample radioactivity. However as <6% of radioactivity remained in fish tissues after 28 days of depuration, each metabolite accounted <6% of sample concentration. Therefore, no further analysis was conducted on these components.

Details on results:

- Mortality of test organisms: With the exception of one fish from the 100 µg/g treatment group which exhibited increased pigmentation on Day 20 (for one day only) of the depuration phase, no mortalities or sub lethal effects of exposure were observed throughout the test.
- Observations on body length and weight: No abnormalities detected
- Reproduction during test period: not measured
- Other biological observations: No abnormalities detected
- Organ specific bioaccumulation: only whole fish radioactivity is measured
- Mortality and/or behavioural abnormalities of control: No abnormalities detected
- Loss of test substance during test period: total radioactivity remain stable during all test

Table 1 Recoveries of Radioactivity and Purity from Extracts of Feed Treated with [14C]-Test item at a Nominal Concentration of 100 µg/g

	Radioactivity (%)
Days	Feed Extracts	Post Extraction Solid	Total Recovery	Test item (TLC)^a
0	97.9	0.6	98.5	98.1
14	106.8	1.1	107.9	97.3

^a           Expressed as % sample radioactivity, not corrected for extractability

 

 

 

 

Table 2 Concentration in Whole Fish Treated with [14C]-Test item at a Nominal Concentration of 100 µg/g

Day/Phase	Concentration (µg equivalents/g)
	Fish 1	Fish 2	Fish 3	Fish 4	Fish 5	Mean	SD
Day 0 (pre-exposure)	nd	nd	nd	nd	nd	nd	-
14 exposure/ Day 0 depuration	1.27	1.04	0.784	0.664	0.845	0.921 (100)	0.238
Day 1 depuration	0.193	0.193	0.175	0.204	0.196	0.192 (79.1)	0.011
Day 4 depuration	0.167	0.154	0.189	0.160	0.153	0.165 (82.1)	0.015
Day 7 depuration	0.168	0.129	0.119	0.125	0.102	0.129 (86.0)	0.024
Day 21 depuration	0.089	0.076	0.098	0.094	0.100	0.091 (90.1)	0.010
Day 28 depuration	0.042	0.054	0.050	0.050	0.053	0.050 (94.6)	0.005

Values in parentheses represent the percent decline in concentration from the mean value at the end of the exposure phase

SD       Standard deviation

nd        Not detected

• Not applicable

 

 

Table 3 Proportions and Concentrations in Extracts of Whole Fish Treated with

Day/Phase	% Test item	Mean mg equivalents of Test item/g (corrected for parent)
Day 14 exposure/ Day 0 depuration	84.1	0.921 (0.775)
Day 1 depuration	7.8	0.192 (0.015)
Day 4 depuration	2.3	0.165 (0.004)
Day 7 depuration	1.8	0.129 (0.002)
Day 21 depuration	2.9	0.091 (0.003)
Day 28 depuration	1.1	0.050 (0.001)

 

Table 4 Lipid Content Normalized Concentrations in Whole Fish Treated with [14C]-Test item

Day/Phase	Lipid Content (% tissue weight)	Mean concentration normalized to 5% lipid content (mg equivalents/g)	Mean concentration normalized to 5% lipid content (mg equivalents/g corrected for parent)
Day 0^a	3.06	nm	nm
Day 14 exposure/ Day 0 depuration	3.56	1.294	1.088
Day 1 depuration	3.28	0.293	0.023
Day 4 depuration	3.68	0.224	0.005
Day 7 depuration	3.36	0.192	0.003
Day 21 depuration	3.89	0.117	0.004
Day 28 depuration	3.35	0.075	0.001

Results are normalized to 5% lipid content

nm         not measured, no radioactivity in fish tissue

^a             fish sampled from stock

 

 

 

Table 5 Kinetic Parameters Delivered from Mean Radioactivity Concentrations in Rainbow Trout after 14 Days Exposure to [14C]-Test item at a Nominal Concentration of 100 µg/g

Parameter	Estimate
Kinetic biomagnification factor (BMFK)	0.0091952
Growth corrected kinetic biomagnification factor (BMFKg)	0.0092532
Growth corrected half-life (t½g in days)	0.45545
Lipid normalized growth corrected kinetic biomagnification factor (BMFKgL for 18% lipid food content)	0.055519

 

 

Validity criteria fulfilled:

yes

Reference 2

Endpoint:

bioaccumulation in aquatic species, other

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Validated QSAR model

Justification for type of information:

QSAR prediction: migrated from IUCLID 5.6

Principles of method if other than guideline:

Calculation based on BCFBAF v3.01, Estimation Programs Interface Suite™ for Microsoft® Windows v 4.10. US EPA, United States Environmental Protection Agency, Washington, DC, USA.

GLP compliance:

no

Test organisms (species):

other: fish

Route of exposure:

aqueous

Test type:

other: calculation

Water / sediment media type:

natural water: freshwater

Type:

BCF

Value:

0.89 L/kg

Basis:

whole body w.w.

Remarks on result:

other: Arnot Gobas (including biotransformation rate estimates, upper trophic)

BCFBAF Program (v3.01) Results:

==============================

SMILES : O=C(NCCCCCCCCCCCCCCCCCC)CCCCCCCCCCCC=CCCCCCCCC

CHEM : 13-Docosenamide, N-octadecyl-, (Z)-

MOL FOR: C40 H79 N1 O1

MOL WT : 590.08

--------------------------------- BCFBAF v3.01 ----------------------------

----

Summary Results:

Log BCF (regression-based estimate): 0.50 (BCF = 3.16 L/kg wet-wt)

Biotransformation Half-Life (days) : 1.83e+003 (normalized to 10 g fish)

Log BAF (Arnot-Gobas upper trophic): -0.04 (BAF = 0.911 L/kg wet-wt)

Log Kow (experimental): not available from database

Log Kow used by BCF estimates: 17.26

Equation Used to Make BCF estimate:

Log BCF = -0.49 log Kow + 7.554 + Correction

Correction(s): Value

No Applicable Correction Factors

Minimum Log BCF of 0.50 applied when Log Kow > 7

Estimated Log BCF = 0.500 (BCF = 3.162 L/kg wet-wt)

===========================================================

Whole Body Primary Biotransformation Rate Estimate for Fish:

===========================================================

------+-----+--------------------------------------------+---------+-------

--

TYPE | NUM | LOG BIOTRANSFORMATION FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+-------

--

Frag | 2 | Linear C4 terminal chain [CCC-CH3] | 0.0341 | 0.0682

Frag | 1 | Amide [-C(=O)-N or -C(=S)-N] | -0.5952 | -0.5952

Frag | 2 | Methyl [-CH3] | 0.2451 | 0.4902

Frag | 35 | -CH2- [linear] | 0.0242 | 0.8465

Frag | 2 | -C=CH [alkenyl hydrogen] | 0.0988 | 0.1977

Frag | 2 | -C=CH [alkenyl hydrogen] | 0.0000 | 0.0000

L Kow| * | Log Kow = 17.26 (KowWin estimate) | 0.3073 | 5.3046

MolWt| * | Molecular Weight Parameter | | -1.5132

Const| * | Equation Constant | | -1.5058

============+============================================+=========+=======

==

RESULT | LOG Bio Half-Life (days) | | 3.2618

RESULT | Bio Half-Life (days) | | 1827

NOTE | Bio Half-Life Normalized to 10 g fish at 15 deg C |

============+============================================+=========+=======

==

Biotransformation Rate Constant:

kM (Rate Constant): 0.0003793 /day (10 gram fish)

kM (Rate Constant): 0.0002133 /day (100 gram fish)

kM (Rate Constant): 0.0001199 /day (1 kg fish)

kM (Rate Constant): 6.745e-005 /day (10 kg fish)

Arnot-Gobas BCF & BAF Methods (including biotransformation rate estimates):

Estimated Log BCF (upper trophic) = -0.049 (BCF = 0.893 L/kg wet-wt)

Estimated Log BAF (upper trophic) = -0.040 (BAF = 0.9113 L/kg wet-wt)

Estimated Log BCF (mid trophic) = -0.031 (BCF = 0.9315 L/kg wet-wt)

Estimated Log BAF (mid trophic) = -0.027 (BAF = 0.9394 L/kg wet-wt)

Estimated Log BCF (lower trophic) = -0.027 (BCF = 0.9402 L/kg wet-wt)

Estimated Log BAF (lower trophic) = -0.025 (BAF = 0.9444 L/kg wet-wt)

Arnot-Gobas BCF & BAF Methods (assuming a biotransformation rate of zero):

Estimated Log BCF (upper trophic) = -0.049 (BCF = 0.893 L/kg wet-wt)

Estimated Log BAF (upper trophic) = -0.038 (BAF = 0.9168 L/kg wet-wt)

Reference 3

Endpoint:

bioaccumulation in aquatic species, other

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Validated QSAR model

Justification for type of information:

QSAR prediction: migrated from IUCLID 5.6

Principles of method if other than guideline:

Calculation based on BCFBAF v3.01, Estimation Programs Interface Suite™ for Microsoft® Windows v 4.10. US EPA, United States Environmental Protection Agency, Washington, DC, USA

GLP compliance:

no

Test organisms (species):

other: Fish

Route of exposure:

aqueous

Test type:

other: Calculation

Water / sediment media type:

natural water: freshwater

Type:

BCF

Value:

3.16 L/kg

Basis:

whole body w.w.

Remarks on result:

other: regression-based estimate

Description of key information

The kinetic parameters are given below:

Parameter	Estimate
Kinetic biomagnification factor (BMFK)	0.0091952
Growth corrected kinetic biomagnification factor (BMFKg)	0.0092532
Growth corrected half-life (t½g in days)	0.45545
Lipid normalized growth corrected kinetic biomagnification factor (BMFKgL for 18% lipid food content)	0.055519

 

 

BCF regression based = 3.16 L/Kg

BCF Arnot Gobas = 0.89 L/Kg

Key value for chemical safety assessment

BMF in fish (dimensionless):

0.056

Additional information

The potential for the substance (Z)-N-octadecyldocos-13-enamide (CAS No. 10094-45-8) to bioaccumulate in rainbow trout (Oncorhynchus mykiss) was studied by exposure to treated diet in a continuous flow-through system under OECD 305 "Bioaccumulation in Fish: Aqueous and Dietary Exposure" protocol (Covance, 2020).

Juvenile fishes were exposed to radiolabeled test item, at a nominal concentration of 100 µg/g feed over a 14-day exposure period at a temperature of 12°C.  At the end of the 14 day exposure period, ten fish were removed for analysis.  The depuration of accumulated residues in remaining fish was monitored over 28 days.  The mean concentration of total radioactivity in fish tissue was 0.921 µg equivalents/g after 14 days of exposure, but had declined to 0.050 µg equivalents/g after 28 days of depuration.  This represents a reduction in total body burden of 94.6% of the accumulated radioactivity.

The radioactivity extracted from the fish tissue was in the range 68.4 – 113.3% sample radioactivity.  Chromatographic analysis of the extracts showed most of the radioactivity extracted from fish tissue at Day 14 uptake phase was unchanged test item, accounting for 84.1% sample radioactivity (0.775 µg/g).  After 1 day depuration, test item accounted for 7.8% sample radioacitivity (0.015 µg/g).

Up to five unidentified metabolites were observed in addition to test item. Two major unknown metabolites increased to >10% of the sample radioactivity. However as <6% of radioactivity remained in fish tissues after 28 days of depuration, each metabolite accounted <6% of sample concentration. Therefore, no further analysis was conducted on these components.

 

The kinetic parameters are given below:

Parameter	Estimate
Kinetic biomagnification factor (BMFK)	0.0091952
Growth corrected kinetic biomagnification factor (BMFKg)	0.0092532
Growth corrected half-life (t½g in days)	0.45545
Lipid normalized growth corrected kinetic biomagnification factor (BMFKgL for 18% lipid food content)	0.055519

 

 

For the duration of the depuration phase, the overall range of lipid content (% body weight) measured was 3.06 – 3.89%.  The mean concentrations of test item normalized to an average 5% lipid content declined from 1.088 µg equivalents/g after 14 days of exposure to 0.023 µg equivalents/g after 1 day of depuration and 0.001 µg equivalents/g after 28 days of depuration.

The biomagnification factor (BMFK) and the lipid normalized biomagnification factor corrected for growth rate (BMFKgL) were estimated to be <0.1.  The growth corrected half-life (t1/2g) was estimated to be 0.46 days, suggesting a rapid elimination of radioactivity from fish tissues following a 14-day exposure to food treated with [14C]-test item.

 

In support of this study, two QSAR were performed to estimate the BCF of the substance. Indeed the bioaccumulation potential of a substance is driven by the physico-chemical properties of the substance triggering the bioavailability as well as by metabolism and excretion. As the test substance is highly unsoluble in water (< 0.05 mg/L) the bioavailability of the substance in water is negligible. Though the substance has a high partition coefficient (log Kow of >10) indicating the potential to bioaccumulate a significant accumulation is not expected based on the environmental fate and on BCF/BAF calculation as well as the result from the experimental study.

The log Koc values of 5 indicates that the substance will adsorb to suspended organic particles, to dissolved organic matter and to some degree to biota in the aquatic environment. If available, a potential uptake of the substance by organisms of the pelagic zone is expected to occur mainly via food ingestion since the substance may adsorb to solid particles.

Despite that the substance is not readily biodegradable, the substance is poorly soluble (< 0.05 mg/L) reducing its availability in the water column. Moreover, as the substance is highly adsorptive, this reduces even more the availability of the substance in the water column. Thus, a significant uptake of the substance by aquatic organisms through the water phase is not expected. Therefore, the dietary route is the main possible route for any bioaccumulation.

This assumption is supported by QSAR calculations. A calculated BCF/BAF of 0.89 L/kg (SRC BCFBAF v3.01 Arnot Gobas, upper trophic level) indicates that the substance has a low bioaccumulation potential via the water phase (Knoell Consult GmbH, 2012).

In conclusion, the bioaccumulation potential of the substance is low.