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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Deviations:
no
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
GLP compliance:
yes
Test material information:
Composition 1
Analytical monitoring:
yes
Details on sampling:
Sampling schedule of chemical analysis:
Stock solution: at 0 hours
Control: at 0 and 48 hours
Test concentrations: at 0 and 48 hours, exception 20 mg/L at 0 and 24 h
Vehicle:
no
Details on test solutions:
Culture and dilution water:
Reconstituted water (so-called 'M4 medium', originally described in Water Research 24 (9): 1157-1167), prepared according to the recommendations of Bundesgesundheitsamt Berlin. This standard dilution water is used for both, the maintenance of the test animals and the preparation of stock and test solutions of the test substance.
Test organisms (species):
Daphnia magna
Details on test organisms:
- Name: Daphnia magna STRAUS, parthenogenetic females
- Source: Strain of Bundesgesundheitsamt Berlin

Maintenance and Acclimatisation:
A population of parthenogenetic females of synchronized age structure is maintained since more than 15 years in the test facility under constant temperature conditions (20 +/- 1 °C) at a 16 : 8 hour light-dark photoperiod (illumination: < 1000 lux). The culture water (so-called 'M4 medium') is partly renewed once a week. The Daphnia are exclusively fed with unicellular green algae (Scenedesmus subspicatus CHODAT) 'ad libitum'. Mortalities of parent Daphnia during the culture period are recorded daily in a semi-quantitative way. The neonates are separated from their parent Daphnia by filtration prior to the acute test.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
15.7 °dH (280.2 mg/L CaCO3)
Test temperature:
18 - 22 °C, mean +- 1 °C
pH:
7.7 - 8.0
Dissolved oxygen:
8.7 - 9.0 mg/L
Nominal and measured concentrations:
Nominal: 2.5, 5.0, 10 and 20 mg/L
Mesaured (mean): 5.1, 7.7, 12.8, 22.1 mg/L
Details on test conditions:
- Test vessels: 50 mL glass beakers holding 10 neonates in 20 mL of test medium
- Experimental design: 4 test concentrations plus 1 control, 10 neonates per vessel, 2 replicates per concentration/control, no feeding during the exposure period
- Method of initiation: Neonates were placed in prepared media
- Photoperiod: 16 h light : 8 h dark
- Aeration: none
- Criteria of effects: The criterion of adverse effects used in this study was the substance-induced alteration of the normal mobility behaviour and the loss of locomotory actions of the neonates, observed at 24 and 48 hours
Duration:
48 h
Dose descriptor:
EC0
Effect conc.:
5 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
other: immobilisation
Duration:
48 h
Dose descriptor:
EC100
Effect conc.:
12.8 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
other: immobilisation
Duration:
48 h
Dose descriptor:
other: Geometric mean EC0 / EC 100
Effect conc.:
8.1 mg/L
Basis for effect:
other: immobilisation
Details on results:
24h-EC0 5.0 mg/L, 24h-EC100 20.0 mg/L, Geometric mean EC0/EC100 10 mg/L

The above results are expressed in terms of nominal concentrations (at 24 hours) and in terms of mean measured concentrations (at 48 hours).
Measured concentrations ranged from 111 - 204 % of nominal values.

Immobilisation (initial population: 20)

 cummulative [%]        time [h]
[mg/L]  0  24  48
control  0
2.5  0 0
 0 0 25
10  0 50 100
20  0  100  --

Chemical analysis

Factor 'Molecular weight/Organic C content': 1.7

TOC values multiplied by Factor 1.7 corresponds to test substance

TOC values / testsubstance

       time [h]  mean value testsubstance
[mg/L]  0  24  48  [mg/L]
control  < 2 / <3.4 --  < 2 / <3.4  < 3.4
2.5 3 / 5.1 -- 3 / 5.1  5.1
 4 / 6.8 -- 5 / 8.5  7.7
10  7 / 11.9 -- 8 / 13.6  12.8
20  13 / 22.1  13 / 22.1  --  22.1
Validity criteria fulfilled:
yes
Remarks:
dissolved O2 > 3 mg/L; immob. in controls < 10%; concentration of test substance > 80% of initial conc. throughout the study
Conclusions:
Daphnia Magna was exposed under static conditions for 48 h to four concentrations of the test substance Imidoxim. The geometric mean of EC0 and EC100 is 8.1 mg/L.
Executive summary:

A study was performed to assess the acute toxicity of the test substance Imidoxim to Daphnia magna STRAUS under static conditions. The study was conducted in accordance with EEC Methods for Determination of Ecotoxicity Annex to Directive 92/69/EEC (O.J. No. L383A, 29.12.92) Part C, Method 2 'Acute toxicity for Daphnia' which is in most parts equivalent to the OECD Guideline for Testing of Chemicals No. 202 'Daphnia sp., Acute Immobilisation Test and Reproduction Test, Part I - 24h EC50 Acute Immobilisation Test'. The Daphnia were exposed to a range of concentrations, nominally 2.5 mg/L, 5.0 mg/L, 10 mg/L and 20 mg/L of the test substance dissolved in water. Auxiliaries used to prepare the test media were an ultrasonic bath, a magnetic stirrer and a folded filter. A control was run in parallel. 20 Daphnia were exposed per concentration / control. Observations were made on swimming ability and the immobilisation rate, respectively, after 24 and 48 hours of exposure. Analysis of the immobilisation rates give the following results: the highest test concentration resulting in 0 % immobilisation (48h-EC0) is 5.1 mg/L and the lowest test concentration resulting in 100 % immobilisation (EC 100 48h) is 12.8 mg/L. The geometric mean of EC0 and EC100 is 8.1 mg/L.

Description of key information

A study was conducted in accordance with EEC Methods for Determination of Ecotoxicity Annex to Directive 92/69/EEC (O.J. No. L383A, 29.12.92) Part C, Method 2 'Acute toxicity for Daphnia' to assess the acute toxicity of the test substance Imidoxim to Daphnia magna STRAUS.

Daphnia Magna was exposed under static conditions for 48 h to four concentrations of the test substance. The geometric mean of EC0 and EC100 is 8.1 mg/L.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
8.1 mg/L

Additional information