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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:
December 1997 - April 1998
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 211 (Daphnia magna Reproduction Test)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Concentrations:
- Sampling method: the test solution was collected 6 times during the 21 day exposure period (3 repititions, before and after water change)
- Sample storage conditions before analysis:
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- the required amount of test substance was dissolved in dilution water to prepare 1000 mg/l of undiluted test solution;
- the test solution for each dose group was prepared by miximg the approriate amount of undiluted test solution with dilution water and apportioning into the appropriate test vessel
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Daphnia
- Source: the species was obtained from Sheffield University (Sheffield, UK) and continously bred in thr research laboratory
- Breeding:
* Daphnia were bred continously, 2 to 4 weeks of age were used as parents for the test organisms. When daphnia matured to the point where they
could produce juveniles, juveniles were removed on the day before the test or on a prior day. Batches with high mortality and batches in which
resting eggs or males were found were not used.
* Breeding water: dilution water
* Breeding density: 10 - 30 organisms / 800 ml breeding water
* Water temperature: 20 +/- 1 °C
- Age of parental stock (mean and range, SD): 2 - 4 weeks
- Age of juveniles: < 24 hours
- Feeding breeding and during test
- Food type: Chlorella vulgaris,
- Amount: 0.1 - 0.2 mgC/day/individual
- Frequency: daily


ACCLIMATION
- Acclimation period: 2-4 weeks
- Acclimation conditions: same as test
- Type and amount of food: same as during breeding and test
- Feeding frequency: daily

Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
21 d
Post exposure observation period:
not applicable
Hardness:
38.8 - 44.0 mg/l CaCO3
Test temperature:
19.5 - 20.8 °C
pH:
7.5 -7.9
Dissolved oxygen:
7.8 - 8.9 mg/l
Salinity:
not applicable
Nominal and measured concentrations:
Nominal concentrations: 25, 50, 100 mg/L (Dosage was set up from the result of an acute toxicity study to daphnia magna and a preliminary study)
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): open
- Aeration: no
- Volume: 100 ml
- Fill volume: 80.0 ml per vessel
- Type of flow-through (e.g. peristaltic or proportional diluter):
- Renewal rate of test solution (frequency/flow rate):
- 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: dichlorinated tap water (chlorine < 0.02 mg/L)
- Metals: < L.O.D.
- Pesticides: < L.O.D.
- Chlorine: < 0.02 mg/l
- Alkalinity: 29.0 mg/l
- Ca/mg ratio: 2.95
- Conductivity: 148 µS/cm



OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: light / dark cycle: 16 hours / 8 hours
- Light intensity: 1200 lux or below
- Water temperature: 20 +/- 1 °C


Reference substance (positive control):
yes
Remarks:
potassium dichromat, EiC50 (48 hours) = 0.141 mg/l
Duration:
14 d
Dose descriptor:
LC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: The mortality rate in parental Daphnia in the 100 mg/l group was 40 %
Key result
Duration:
21 d
Dose descriptor:
LC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: The mortality rate in parental Daphnia in the 100 mg/l group was 40 %
Duration:
14 d
Dose descriptor:
other: ErC50
Effect conc.:
70.7 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Remarks on result:
other: 95 % CL: 50.0 - 100.0 mg/l
Duration:
21 d
Dose descriptor:
other: ErC50
Effect conc.:
69.6 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Remarks on result:
other: 95 % CL: 50.0 - 100.0 mg/l
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
25 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
50 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Details on results:
- Mortality of parent animals:
* cumulative mortality in control group at the end of the exposure period: < 10 %
* mortality in the 25.0 mg/l group at the end of the exposure period: 1 organism was found dead
* mortality in the 50.0 mg/l group on Days 19 and 21 of exposure 1 and 2 organisms, respectively, were found dead
* mortality in the 100.0 mg/l group on Days 4, 8 and 16 of exposure 2, 1 and 1 organisms, respectively, were found dead
* however, no group showed significant statistical differences when compared to the control group

- Day of first juvenile birth:
* the average day of the first juvenile birtj in the 25.0 mg/l and 50.0 mg/l group was day 8.3
* this was largely identical to that in the control group, Day 8.2
* no juvenile production was observed in the 100 mg/l group

- No. of offspring produced per day per female:
* the average cumulative offspring number per parent Daphnia in the control group was 126
* the average cumulative offspring number per parent Daphnia in the 25.0 mg/l and 50.0 mg/l groups were 135 and 125, respectively
* these results were not significantly different from those in the control group
* in the 100 mg/l group, no juveniles were produces and thus a significant difference was seen with the control group

- Size and condition of parent animals:
* no difference was found in size or condition of the 25.0 mg/l group in comparison to the control group
* in the 50.0 mg/l and 100.0 mg/l groups, in addition to other phenomena, inhibition of growth and body colour paling were observed in several
organisms from Day 14 and Day 2, respectively, from the start of exposure until the end of the test

- Emergence of resting-eggs and other phenomena:
* emergence of resting-eggs was not obserevd in any test group during the exposure period
* in the control group and 25.0 mg/l group, just 3 and 7 dead juveniles, respectively, were found
* allthough fallen eggs were obserevd in the control, 25.0 mg/l and 50.0 mg/l groups (3.4, 5.1 and 7.9, respectively, per parent Daphnia), a
significant increase was seen in the 100.0 mg/l group (28.2 per parent Daphnia)
Results with reference substance (positive control):
potassium dichromat, EiC50 (48 hours) = 0.141 mg/l
Reported statistics and error estimates:
- Mortality of parent animals: Kruskal-Wallis rank sum test
- Day of first juvenile birth: Kruskal-Wallis rank sum test
- Average cumulative number of juveniles: one-factor ANOVA and Scheffe Multiple Comparison Methods

 

Table 1: Cumulative number of dead parental Daphnia and mortality during exposure of 21day

Nominal concentration

[mg/L]

Number of dead parental Daphnia

Mortality(%)

Control

1

10

25.0

1

10

50.0

3

30

100.0

4

40

 

Table 2:mean cumulative number of juveniles produced per adult during exposure after 21 days

Nominal concentration

[mg/L]

Number

Control

126

25.0

135

50.0

125

100.0

0 **

**: Significantly different from Control at p < 0.01

Validity criteria fulfilled:
yes
Conclusions:
The 21 day LC50based on mortality was > 100 mg/L.  The 21-day NOEC based on reproduction was 25.0 mg/L.  The concentration with causing 50 % of inhibition of reproduction (EC50) over 21 days was 69.9 mg/L (95 % confidence limit 50.0 – 100.0 mg/L). The lowest observed effect concentration on reproduction (LOEC) was 50.0 mg/L.
Therefore, it can be concluded that Dicyandiamide was practically non-toxic to Daphnia magna under the conditions of this 21- day toxicity test.
Executive summary:

The 21-day-chronic toxicity of Dicyandiamide to Daphnia magna was studied under semi-static conditions. Daphnids were exposed to control and test chemical solutions at nominal concentrations of 0, 25.0, 50.0, and 100.0 mg/L. 

The 21 day LC50based on mortality was > 100 mg/L.  The 21-day NOEC based on reproduction was 25.0 mg/L.  The concentration with causing 50 % of inhibition of reproduction (EC50) over 21 days was 69.9 mg/L (95 % confidence limit 50.0 – 100.0 mg/L). The lowest observed effect concentration on reproduction (LOEC) was 50.0 mg/L.

This study is classified as acceptable and satisfies the guideline requirements for a chronic toxicity study with freshwater invertebrates (OECD 211).

 

Results Synopsis

Test Organism Age (e.g. 1stinstar): 2-4 weeks (parental animals)

Test Type: semi-static

LC50> 100.0 mg/L

EC50:   69.9 mg/L

NOEC:  25.0 mg/L

LOEC:  50.0 mg/L                     Endpoint(s) Effected:  reproduction

Description of key information

The 21-day-chronic toxicity of Dicyandiamide to Daphnia magna was studied under semi-static conditions according to OECD 211 (Daphnia magna Reproduction Test). Daphnids were exposed to control and test chemical solutions at nominal concentrations of

0, 25.0, 50.0, and 100.0 mg/L. 
 

Key value for chemical safety assessment

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

Additional information

The 21 day LC50 based on mortality was > 100 mg/L.  The 21-day NOEC based on reproduction was 25.0 mg/L.  The concentration causing 50 % inhibition of reproduction (EC50) over 21 days was 69.9 mg/L (95 % confidence limit 50.0 – 100.0 mg/L). The lowest observed effect concentration on reproduction (LOEC) was 50.0 mg/L.

This study is classified as acceptable and satisfies the guideline requirements for a chronic toxicity study with freshwater invertebrates (OECD 211).

 

Results Synopsis

Test Organism Age (e.g. 1stinstar): 2-4 weeks (parental animals)

LC50> 100.0 mg/L

EC50:   69.9 mg/L

NOEC:  25.0 mg/L

LOEC:  50.0 mg/L                     Endpoint(s) Effected:  reproduction