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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
See ilustration.
Analytical monitoring:
yes
Details on sampling:
The concentrations in the test solutions were measured at 0 and 48 hours. At the start of the test, the excess test solutions were sampled, and at the end of the test, one replicate of the dilution water control and test concentration were sampled.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION:
A primary stock concentrate of methyl propyl ketoxime, with a nominal concentration of 100 mg/L, was prepared by adding a nominal 0.1 g of test substance to 1 litre of dilution water. The concentrate was then inverted and stirred for 10 minutes.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Daphnia magna
- Source: Brixham Environmental Laboratory
- Age at study initiation (mean and range, SD): < 24 hours
- Method of breeding: The parent animals were 28 ± 1 days old and had been maintained with a twice weekly renewal of reconstituted water medium since birth.
- Feeding during test: No
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
48 h
Post exposure observation period:
none
Hardness:
251.3 mg/L CaCO3
Test temperature:
20 ± 1°C
pH:
7.87 to 7.97
Dissolved oxygen:
9.2 mg/l
Nominal and measured concentrations:
Nominal concentrations: 0 (control), 100 mg/L
Measured concentrations (mean): 0 (control), 99 mg/L
The measured concentration at the start of the study was 98 % of nominal and at the end was 100 % of nominal. On the basis of the analytical data the nominal concentrations were used for reporting results.
Details on test conditions:
TEST SYSTEM
- Test vessel: Glass beakers of 250 ml nominal capacity
- Type (delete if not applicable): covered with loose fitting glass lids
- Material, size, headspace, fill volume: 200ml, 60 mm depth
- Aeration: no
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Biomass loading rate: 5 D. magna per 200 ml (1 Daphnid per 40 ml).

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: no
- Conductivity: 639 μS/cm

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16 hours light:8 hours dark, with 20 minute dusk and dawn transition periods

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): An assessment of the response of the D. magna was made 24 and 48 hours after the commencement of the test. Each D. magna was viewed by eye and was defined as affected if showing no whole body movement, relative to the water, within a period of 15 seconds even if movement of individual appendages was visible. D. magna so affected were termed immobile. Any overt symptoms of toxicity were also recorded.
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Key result
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
- Behavioural abnormalities: No daphnids were immobile in the test concentration after 24 and 48 hours, although a proportion of the D. magna in the test concentration were floating on the meniscus of the water, fully mobile.
- Other adverse effects control: 1 of 20 were immobile at 48hrs (5 %), which is within the validity criteria
- Abnormal responses: none observed

Reported statistics and error estimates:
The median effect concentration (EC50) was defined as the concentration resulting in 50 % immobilisation of the D. magna in the time period specified.
Validity criteria fulfilled:
yes
Remarks:
immobilization of controls and dissolved oxygen within appropriate range
Conclusions:
The 48h-EC50 of the test item in Daphnia magna was determined to be >113 mg/L and the NOEC was >= 113 mg/L based on mobility.
Executive summary:

A short-term toxicity tests on aquatic invertebrates was performed with the test substance MPKO according to OECD Guideline 202. 20 Daphnia magna (<24 h old, 5 per replicate) were exposed to either a control medium or 100 mg/L MPKO for 48 hours under static conditions. Validity criteria were fulfilled. There was no immobility observed within the period of the test, therefore the 48h-EC50 for MPKO was >100 mg/L. The 48h-NOEC based on immobility was determined to be ≥100 mg/L.

Description of key information

Based on the read-across approach from the analogue substance MPKO, the 48h-EC50 of OS1600 in Daphnia magna was determined to be >113 mg/L and the NOEC was >= 113 mg/L based on mobility.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
113 mg/L

Additional information

Key study: Read-across approach from experimental data on the analogue substance MPKO: A short-term toxicity tests on aquatic invertebrates was performed according to OECD Guideline 202 in Daphnia magna (GLP study). Based on the read-across approach from the experimental data on the analogue MPKO, the hydrolysis product of OS1600 (48h-EC50 > 100 mg/L and the 48h-NOEC >= 100 mg/L), the 48h-EC50 for OS1600 was determined to be >113 mg/L and the 48h-NOEC >= 113 mg/L in Daphnids.