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Long-term toxicity to aquatic invertebrates

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Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
05 Sep - 20 Oct 2012
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP Guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
OECD Guideline 211 (Daphnia magna Reproduction Test)
Qualifier:
according to guideline
Guideline:
EU Method C.20 (Daphnia magna Reproduction Test)
GLP compliance:
yes (incl. QA statement)
Remarks:
The Department of Health of the Government of the United Kingdom, date of inspection: 10 July 2012
Analytical monitoring:
yes
Details on sampling:
- Sampling method: Water samples were taken from the control, solvent control and each surviving test group (replicates pooled) for quantitative analysis. Samples of the fresh test preparations were taken on Days 0, 5, 12 and 19 and of the expired test preparations on Days 2, 7, 14 and 21. Samples were stored at approximately -20 °C prior to analysis. Duplicate samples were taken and stored at approximately -20 °C for further analysis if necessary. Only samples at the No Observed Effect Concentration and above were analyzed.
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: An amount of test item (100 mg) was dissolved in dimethylformamide and the volume adjusted to 10 mL to give a 100 mg/10 mL solvent stock solution. An aliquot (200 µL) of this solvent stock solution was dispersed in 2 liters of Elendt M7 media with the aid of magnetic stirring for approximately 10 minutes. After stirring any undissolved test item was removed by filtration through a 0.2 µm Gelman Acrocap filter (first approximate 500 mL discarded in order to pre-condition the filter) to give the required stock concentration of 100 % v/v solution.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: water flea
- Source: in-house laboratory cultures
- Age of parental stock (mean and range, SD): 1st instar Daphnia magna, less than 24 hours old
- Housing: Adult Daphnia were maintained in 150 mL glass beakers containing Elendt M7 medium in a temperature controlled room at approximately 20 °C. The lighting cycle was controlled to give a 16 hours light and 8 hours darkness cycle with 20 minute dawn and dusk transition periods. Each culture was fed daily with a mixture of algal suspension (Desmodesmus subspicatus) and Tetramin® flake food suspension. Culture conditions ensured that reproduction was by parthenogenesis. Gravid adults were isolated the day before initiation of the test, such that the young daphnids produced overnight were less than 24 hours old.
- Feeding during test: Each daphnid received approximately 2 to 7 μL of an algal suspension (Desmodesmus subspicatus) and approximately 14 to 43 μL of Tetramin® flake food suspension daily. Feeding was at a level of approximately 0.1 to 0.2 mg carbon/daphnid/day, dependent on the age and size of the animals. Equal amounts of food were given to each daphnid.
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
21 d
Hardness:
200 to 316 mg/L as CaCO3
Test temperature:
19 - 21 °C
pH:
6.7 - 8.6
Dissolved oxygen:
8.3 - 9.5 mg O2/L
Nominal and measured concentrations:
control, 0.32, 1.0, 3.2, 10 and 32 % v/v (nominal)
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: 150 mL glass flasks filled with 100 mL test solution and covered with a plastic lid to reduce evaporation
- Aeration: none
- Renewal rate of test solution (frequency/flow rate): daily
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10
- No. of vessels per vehicle control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The reconstituted water (Elendt M7 medium) used for the range-finding and definitive tests was the same as that used to maintain the stock animals

OTHER TEST CONDITIONS
- Photoperiod: 16 hours light and 8 hours darkness with 20 minute dawn and dusk transition periods
- Light intensity: 715 to780 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): On a daily basis the numbers of live and dead of the "Parental" (P1) generation, the numbers of live and dead "Filial" (F1) Daphnia and the number of discarded unhatched eggs were counted. An assessment was also made of the general condition and size of the parental Daphnia as compared with the controls. The number of Daphnia with eggs or young in the brood pouch was determined daily. At the end of the test, the length of each surviving parent animal was determined.

VEHICLE CONTROL PERFORMED: yes

RANGE-FINDING STUDY
- Test concentrations: 1.0, 10 and 100 % v/v solution
- Results used to determine the conditions for the definitive study: No immobilization was observed at the test concentrations of 1.0 and 10 % v/v solution. However, immobilization was observed at 100 % v/v solution.
Reference substance (positive control):
no
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
> 0.002 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
other: filtered test solution
Basis for effect:
immobilisation
Remarks on result:
other: parental Daphnia generation P1
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
> 0.002 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
other: filtered test solution
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
> 0.002 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
other: filtered test solution
Basis for effect:
immobilisation
Remarks:
and reproduction
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
>= 0.002 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
other: filtered test solution
Basis for effect:
immobilisation
Remarks:
and reproduction
Details on results:
Lethal Effects on the Parental Generation (P1):
Mortality (immobilization) occurred at the 3.2 % v/v solution nominal test concentration resulting in 30 % mortality by Day 15. However, as no immobilization was seen in the higher concentrations of 10 and 32 % v/v nominal test concentrations, this mortality did not follow a concentration-dependent pattern. This mortality is therefore not considered to be a true toxic effect of the test item.
Single daphnids were observed to be immobilized in the control and 1.0 % v/v test groups, and 2 daphnids were observed to be immobilized in the solvent control and 0.32 % v/v test groups. However as these values equate to ≤ 20 % immobilization, and do not follow a concentration-dependent pattern, they are not thought to be true toxic effects of the test item.
Therefore, it is considered that no significant mortalities occurred at the 0.32, 1.0, 10 and 32 % v/v test concentrations for the duration of the test.

Sub-lethal Effects on the Parental Generation (P1):
There was no effect on the color of the daphnids at all test concentrations employed. However, after 21 days the results for the adult lengths showed that there was a significant difference between the test concentrations and the solvent control. After 21 days there were no statistically significant differences between the solvent control and all the test groups in terms of the number of live young produced per adult.
The EC50 (reproduction) value based on time-weighted mean measured test concentrations was estimated to be greater than 0.0019 mg/L. Analysis of the data obtained on Day 21 showed that the numbers of live young produced per adult by the solvent control group were not significantly different (P≥0.05) from the control and each test group.
After 21 days the length of each surviving adult was determined. The results showed that there were statistically significant differences (P≥ 0.05)
between the solvent control and all test groups in terms of length of the daphnids after 21 days exposure to the test item.

Effects on the Filial Generation (F1):
Information on the effects of the test item on the F1 generation is limited, since, by study design, the young are removed soon after liberation from the brood pouch. However, an assessment made at each media renewal showed the "filial" daphnids produced by all the test groups were in the same general condition as the young produced by the solvent controls over the duration of the test. Young were first produced in the solvent control test group on Day 8 of the test. There were no unhatched eggs or dead young observed in all control and treatment groups surviving to maturation.
Reported statistics and error estimates:
For the estimation of the "Lowest Observed Effect Concentration" (LOEC) and the "No Observed Effect Concentration" (NOEC) the numbers of live young produced per adult over the duration of the test for the control, solvent control and each test group were compared using one way analysis of variance incorporating Bartlett's test for homogeneity of variance (Sokal and Rohlf 1981) and the Williams test for differences between treatment means when several dose levels are compared with a zero dose control (Williams 1971). Results from the control, solvent control and all the test groups Daphnia length data, determined for the surviving daphnids on termination of the test, were compared using one way analysis of variance incorporating Bartlett’s test for homogeneity of variance (Sokal and Rohlf 1981) and Dunnett’s multiple comparison procedure for comparing several treatments with a control (Dunnett 1955). All statistical analyses were performed using the SAS computer software package (SAS 1999 - 2001).

DUNNETT, C W (1955) A Multiple Comparison Procedure for Comparing Several Treatments With a Control. J Am Stat Assoc 50, 1096-1121.
SAS/STAT Proprietary Software Release 8.02 (1999 - 2001), SAS Institute Inc, Cary, NC, USA.
SOKAL, R R and ROHLF, F J (1981) Biometry. New York : W H Freeman and Company.
WILLIAMS, D A (1971) A Test for Differences Between Treatment Means When Several Dose Levels are Compared With a Zero Dose Control. Biometrics 27, 103-117.

Analysis of the freshly prepared test media for the 32 % v/v nominal test concentration on Days 0, 5, 12 and 19 showed measured test concentrations of 0.0055, 0.0013, 0.0062 and 0.0045 mg/L were obtained respectively. A decline in measured test concentration was observed in the old or expired test media on Days 2, 7, 14 and 21 to less than the limit of quantitation (LOQ) of the analytical method employed (0.0012 mg/L). This decline in concentration was considered to be due to the unstable nature of the test item. It was therefore considered justifiable to base the results on the time-weighted mean measured test concentrations of the test media to give a “worst case” analysis of the data. The time-weighted mean measured test concentration for the 100 % v/v solution nominal test concentration was 0.0019 mg/L.

Table: Summary of Findings Following the Exposure of Daphnia magna for 21 Days

Nominal Concentration (% v/v solution)

% Survival of P1

Number of Live Young*

Number of Dead Young*

Number of Unhatched Eggs*

Total

Per Female (cumulative) 

Total

Per Female (cumulative) 

Total

Per Female (cumulative) 

Control

90

682

69

0

0

0

0

Solvent Control

80

644

72

0

0

0

0

0.32

80

585

62

0

0

0

0

1.0

90

771

85

0

0

0

0

3.2

70

589

74

0

0

0

0

10

100

735

74

0

0

0

0

32

100

806

81

0

0

0

0

* The number of live young per live adult at Day 21

Table: Numbers of live young produced per adult

Nominal Concentration (% v/v solution)

Number of Live Young Produced per Adult by Day 21

Control

Mean

68.2

 

Standard Deviation

24.9

Solvent Control

Mean

68.6

 

Standard Deviation

28.0

10

Mean

58.5

 

Standard Deviation

33.0

18

Mean

77.1

 

Standard Deviation

27.4

32

Mean

58.9

 

Standard Deviation

40.9

56

Mean

73.5

 

Standard Deviation

15.4

100

Mean

80.6

 

Standard Deviation

11.1

Table: Daphnia length data

Nominal Concentration (% v/v solution)

Daphnia lengths at Day 21 (mm)

Control

Mean

3.7

 

Standard Deviation

0.1

Solvent Control

Mean

3.8

 

Standard Deviation

0.1

10

Mean

3.7

 

Standard Deviation

0.1

18

Mean

3.7

 

Standard Deviation

0.1

32

Mean

3.6

 

Standard Deviation

0.1

56

Mean

3.6

 

Standard Deviation

0.1

100

Mean

3.6

 

Standard Deviation

0.1

Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Remarks:
Summary of available data used for the endpoint assessment of the target substance
Adequacy of study:
key study
Justification for type of information:
Please refer to the Analogue Justification provided in IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
> 0.002 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
other:
Remarks:
filtered test solution
Basis for effect:
immobilisation
Remarks on result:
other:
Remarks:
source, CAS 68855-18-5, Croda, 2013, Daphnia magna, 21 d, RL2
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
> 0.002 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
other: filtered test solution
Basis for effect:
reproduction
Remarks on result:
other:
Remarks:
source, CAS 68855-18-5, Croda, 2013, Daphnia magna, 21 d, RL2
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
> 0.002 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
other: filtered test solution
Basis for effect:
immobilisation
Remarks:
and reproduction
Remarks on result:
other:
Remarks:
source, CAS 68855-18-5, Croda, 2013, Daphnia magna, 21 d, RL2
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
>= 0.002 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
other: filtered test solution
Basis for effect:
immobilisation
Remarks:
and reproduction
Remarks on result:
other:
Remarks:
source, CAS 68855-18-5, Croda, 2013, Daphnia magna, 21 d, RL2
Conclusions:
No effects are expected up to the limit of water solubility.

Description of key information

NOEC (21 d)0.0019 mg/L (measured, TWA; Daphnia magna); no effects up to the limit of water solubility; read-across

Key value for chemical safety assessment

Additional information

There is no study available in which the long-term toxicity of Neopentyl glycol dicaprate (CAS No. 27841-06-1) to aquatic invertebrates was assessed. Therefore, read-across to the structurally and chemically closely related source substance Heptanoic acid, ester with 2,2-dimethyl-1,3-propanediol (CAS 68855-18-5) was performed in accordance with Regulation (EC) No 1907/2006 Annex XI, section 1.5 in order to fulfill the data requirements for this substance. The source substance is characterized by similar chemical structure and is therefore considered a suitable representative for the assessment of the long-term toxicity of the target substance to aquatic invertebrates. A detailed read-across justification in provided in IUCLID section 13.

The study conducted with the source substance Heptanoic acid, ester with 2,2-dimethyl-1,3-propanediol (CAS 68855-18-5) was conducted under semi-static conditions and according to OECD Guideline 211, using Daphnia magnaas test organism. Five treatment solutions of 0.32, 1.0, 3.2, 10 and 32 % v/v (nominal), plus blank and solvent controls were prepared using the solvent dimethylformamide (DMFA) as vehicle. The test solutions were applied as filtered solutions. No significant immobilisation or effects on reproduction that can be attributed to the intrinsic toxicity of the test item was observed in the parental generation (P1) during the 21 day exposure period. Statistically significant differences for body length of the surviving adults were observed between the solvent control and all test groups after 21 days. No adverse effects were observed in the filial generation (F1).

The NOEC was determined as ≥ 0.0019 mg/L loading rate (measured, TWA) for immobilisation and reproduction.

Based on the available results from a structurally related read-across substance (in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5) which is characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that the target substance Neopentyl glycol dicaprate (CAS No. 27841-06-1) is expected to be not chronically toxic to aquatic invertebrates.