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Long-term toxicity to aquatic invertebrates

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Reference
Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2015
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
a small inconsistency is present in the reported EC50 for reproduction which appear instead to be related to female mortaility
Qualifier:
according to
Guideline:
OECD Guideline 211 (Daphnia magna Reproduction Test)
GLP compliance:
no
Remarks:
The publication does not mention that the study has been conducted under GLP conditions.
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source: Merck (Darmstadt, Germany)
- Purity test date: p.a. grade
Analytical monitoring:
yes
Details on sampling:
- Sampling method: measured once a week after preparing fresh solutions and they varied from the nominal concentrations ±0.1 to 5 %
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Dilution water used for preparing the test solution and the contol (ISO test water) contained 11.76 g CaCl2x2H2O, 4.93 g MgSO4x7H2O, 2.59 g NaHCO3, and 0.23 g KCl. The test item was diluted in deionised water to 1 L and 25 mL was added to prepare 1 L of dilution water. The dilution water had a conductivity of <10 μS/cm, pH 7.8 and hardness 250 mg/L CaCO3. ISO test water contains 294 mg/L CaCl2 so each exposure CaCl2 concentration was an addition to that content.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: water flea
- Strain/clone: originating from a local wild population and an unpolluted area were reared in the laboratory culture
- Age at study initiation (mean and range, SD): 3rd-5th brood ≤24 h old (from mothers previously acclimated in dilution water)
- Feeding during test: fed daily with 4×105 cel/mL of the algae species Chlorella vulgaris and Scenedesmus obliquus 2:1

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES, INCLUDING CULTURING CONDITIONS:
Laboratory culture was kept in 1000 mL glass vessels at a density of 50 individuals per L in dechlorinated tap water, passed through activated charcoal. Daphnids were fed daily with a concentrated suspension of fresh cultured green algae Chlorella vulgaris and Scenedesmus obliquus, alternately with an addition of suspended dry baking yeast once a week and kept at 20±2 °C at 12/12 photoperiod (550 lux). Once a week, daphnids were transferred to fresh water and neonates were regularly removed.
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
21 d
Remarks on exposure duration:
no data
Post exposure observation period:
not applicable
Hardness:
250 mg/L CaCO3
Test temperature:
20±2 °C
pH:
7.8
Dissolved oxygen:
no data
Salinity:
not applicable
Conductivity:
<10 μS/cm
Nominal and measured concentrations:
nominal concentrations: 240, 481 and 1925 mg/L
measured concentrations: varied from the nominal concentrations ±0.1 to 5 %
Details on test conditions:
TEST SYSTEM
- Test vessel: 50 mL of test solution in glass beakers covered with watch glass
- Aeration: no
- Renewal rate of test solution (frequency/flow rate): 3 times a week
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: preparing test solutions and the controls (ISO test water) contained 11.76 g CaCl2x2H2O, 4.93 g MgSO4x7H2O, 2.59 g NaHCO3, and 0.23 g KCl
- Conductivity: <10 μS cm-1

OTHER TEST CONDITIONS
- Photoperiod: 12:12 photoperiod
- Light intensity: 550 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Three times a week during hange of the medium, neonates and aborted eggs were recorded and discarded, survival was recorded daily.

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 240, 481 and 1925 mg/L
- Results used to determine the conditions for the definitive study: yes. Acute exposure to CaCl2 showed 100% mobility after 48h in daphids exposed to 240 and 481 mg/L and 60% mobility in 1925 mg/L. EC50 48-hour value for CaCl2 was 2020 mg/L (p=0.01)
Reference substance (positive control):
no
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
240 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
900 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality: Total number living offspring produced at the end of the test per parent daphnia at the start of the test excluding from the analysis parental accidental and/or inadvertent mortality {TG 211}
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
481 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: No. of broods
Details on results:
no data
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
The experiments were statistically analysed with one- factorial ANOVA and Tukey post hoc test to reveal the statistical differences between treatments, using Statistica 6 (StatSoft, Tulsa, AZ, USA). The half maximal effective concentration EC50 values were calculated using regression analysis and Bonferroni test and the significance of females’ mortality was determined using Cochran- Armitage trend test

Reproduction and survival of Daphnia magna exposed to CaCl2for 21 days

Group

No. of neonates

No. of broods

Brood size

Days to 1stbrood

Viable neonates/ surviving female/day

No. of aborted eggs

Females’mortality (n)

Longevity (Days)

Control

85.5±7.72

4.5±0.4

20.7±3.31

9.7±0.34

4.1±0.34

0

1

20.9±032

240 mg/L

23.4±2.41

4.1±0.3

5.7±0.53

9.8±1.03

1.1±0.12

0

2

20.8 ±0.42

481 mg/L

17.7±1.77

4.3±0.4

4.8±0.81

10.2±0.79

0.8±0.08

0

3

20.6±0.70

1925 mg/L

2.1±3.00*

0.9±0.7*

1.6±3.02*

11.0±1.15

0.26±0.14*

0

8

16.5±3.84

·      Denotes significance compared to the control

Validity criteria fulfilled:
not specified
Conclusions:
21 days exposure to the test item to Dapnia magna resulted in a LOEC for reproduction of 240 mg/L, a NOEC for number of broods of 481 mg/L and a EC50 for parental mortality of 900 mg/L.

Executive summary:

A study was conducted for 21 days to determine the effect on reproduction of the test item on the crustacean, Daphnia magna. The study was performed the standard OECD guidelines 211. Analytical concentrations varied from the nominal concentrations ±0.1 to 5 %. Results showed LOEC for reproduction of 240 mg/L, a NOEC for number of broods of 481 mg/L and an EC50 for parental mortality of 900 mg/L.

Description of key information

The chronic effect of 21-day exposure on reproduction of Daphnia magna was investigated in two reliable studies (K2) (Biesinger and Christensen 1972 and Mazuran et al. 2015). However, only one was conducted by a standard guideline and hence selected as key study. The lowest effective concentration for reproduction was 240 mg/L (LOEC). The LOEC was the lowest concentrations tested, hence no NOEC for reproduction could be determined.

 

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:
240 mg/L

Additional information

Please note that the NOEC mentioned in the table for key value for chemical safety assessment is a LOEC, not a NOEC. However as it is the lowest reported value, this one was selected to be presented.