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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:
29-05-2017 - 31-05-2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Experimental test result performed using standard test guidelines
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
GLP compliance:
no
Test material information:
Composition 1
Specific details on test material used for the study:
- Name of test material: (±)-menthone
- Molecular formula: C10H18O
- Molecular weight: 154.2512 g/mol
- Substance type: Organic
- Physical state: Liquid
Analytical monitoring:
not specified
Vehicle:
yes
Details on test solutions:
The stock solution (160 mg/L) was prepared by dissolving colourless iquid in reconstituted water. The test solutions of required concentrationas were prepared by mixing the stock solution of the test sample in reconstituted water.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Water flea
- Strain: Straus
- Source: Own breeding at University of Chemistry and Technology, Prague
- Age at study initiation (mean and range, SD): The animals used for the test shall be less than 24 h old and should not be first brood progeny
- Feeding during test: No feeding

ACCLIMATION - No data available
- Acclimation period:
- Acclimation conditions (same as test or not):
- Type and amount of food:
- Feeding frequency:
- Health during acclimation (any mortality observed):
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Remarks on exposure duration:
± 1 hr
Hardness:
No data
Test temperature:
20 ± 1°C
pH:
Without adjustment
Sample at concentration 160 mg/l: pH=7.9 did not changed to 7.8 during the test
Control: pH= 7.7 change to 8 during the test
Dissolved oxygen:
higher than 7.4 mg/L at the end of test both in control and the sample
Salinity:
No data
Conductivity:
No data
Nominal and measured concentrations:
0, 5, 10, 20, 40, 80 and 160 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 50 ml glass vessel
- fill volume: 25 ml
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water:
Natural water (surface or ground water), reconstituted water or dechlorinated tap water are acceptable as culturing and dilution water if D. magna survives in it for the duration of the culturing, acclimation and testing without showing signs of stress. Waters in the range pH 6 to pH 9, with hardness between 140 mg/l and 275 mg/l (as CaCO3) are recommended.
As an example, the preparation of dilution water meeting the requirements is described below.
Dissolve known quantities of reagents in water. The dilution water prepared shall have a pH of 7.8 ± 0.5, a hardness of (225 ± 50) mg/l (expressed as CaCO3), a molar Ca + Mg ratio close to 4 + 1 and a dissolved oxygen concentration above 7 mg/l.

Prepare the solutions specified below:
- Calcium chloride solution: Dissolve 117.6 g of calcium chloride dihydrate (CaCl2.2H2O) in water (4.2) and make up to 1 l with water (4.2).
- Magnesium sulfate solution: Dissolve 49.3 g of magnesium sulfate heptahydrate (MgSO4.7H2O) in water (4.2) and make up to 1 l with water (4.2).
- Sodium bicarbonate solution: Dissolve 25.9 g of sodium bicarbonate (NaHCO3) in water (4.2) and make up to 1 l with water (4.2).
- Potassium chloride solution: Dissolve 2.3 g of potassium chloride (KCI) in water (4.2) and make up to 1 l with water (4.2).

Mixing
Mix 2.5 ml of each of the four solutions and make up to 1 l with water.
The dilution water shall be aerated until the dissolved oxygen concentration has reached saturation and the pH has stabilized. If necessary, adjust the pH to 7.8 ± 0.5 by adding sodium hydroxide (NaOH) solution or hydrochloric acid (HCI). The dilution water prepared in this way shall not be further aerated before use.

- Sodium hydroxide solution, e.g. [NaOH] : 1 mol/l.
- Hydrochloric acid, e.g. [HCl] : 1 mol/l.

Reference substance:
Dissolve 600 mg of potassium dichromate (K2Cr2O7) in water and make up to 1 l with water (4.2).

OTHER TEST CONDITIONS
- Adjustment of pH: no adjustment done
- Photoperiod: No - Darkness
- Light intensity:

CALCULATION:
EC50 was calculated using non linear regression by the software Prism 4.0
Reference substance (positive control):
yes
Remarks:
Potassium dichromate (K2Cr2O7)
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
74.7 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: 95% CL: 54.1 - 103.2 mg/L
Results with reference substance (positive control):
- Results with reference substance valid
- EC50: 0.73 mg/L (24 hours)
Validity criteria fulfilled:
yes
Conclusions:
The median effective concentration (EC50) for the test substance,(±)-menthone, in Daphnia magna was determined to be 74.7mg/L on the basis of mobiity inhibition effects in a 48 hour study.
Executive summary:

Determination of the inhibition of the mobility of daphnids was carried out with the substance (±)-menthone according to OECD Guideline 202.

The test substance was tested at the concentrations 0, 5, 10, 20, 40, 80 and 160 mg/L. Effects on immobilisation were observed for 48 hours.

The median effective concentration (EC50) for the test substance, (±)-menthone, in Daphnia magna was determined to be 74.7mg/L for immobilisation effects.

This value indicates that the substance is likely to be hazardousto aquatic invertebrates and can be classified as Aquatic Chronic 3 as per the CLP criteria.

Description of key information

The median effective concentration (EC50) for the test substance,(±)-menthone, in Daphnia magna was determined to be 74.7mg/L on the basis of mobiity inhibition effects in a 48 hour study.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
74.7 mg/L

Additional information

Various studies, used as key and supporting, for short term toxicity to aquatic invertebrates was reviewed for 2-isopropyl-5-methylcyclohexanone (CAS no 1074-95-9) and two read across, 2-(4-chlorophenoxy)-2-methylpropanoic acid (882-09-7) and (R)-2-(4-Chloro-2-methylphenoxy) propionic acid (16484-77-8). The results are summarised as follows:

In a key study conducted by SSS, determination of the inhibition of the mobility of daphnids was carried out with the substance(±)-menthoneaccording to OECD Guideline 202. The test substance was tested at the concentrations0, 5, 10, 20, 40, 80 and 160 mg/L. Effects on immobilisation were observed for 48 hours.The median effective concentration (EC50) for the test substance,(±)-menthone, in Daphnia magna was determined to be 74.7mg/L for immobilisation effects.

This value indicates that the substance is likely to be hazardousto aquatic invertebrates and can be classified as Aquatic Chronic 3 as per the CLP criteria.

Above experimental data is supported by the prediction done using the OECD QSAR toolbox version 3.4 with log kow as the primary descriptor and considering the five closest read across substances, the short term toxicity on aquatic invertebrates was predicted for 2-isopropyl-5-methylcyclohexanone (CAS no 1074-95-9). EC50 value was estimated to be 55.84mg/L on the basis of mobility for Daphnia magna for 48 hrs duration.

Another prediction on short-term toxicity to invertebrate is predicted using EPI suite, ECOSAR version 1.1, 2017, based on the effects observed in 48 hr exposure. The lethal concentration (LC50) for the substance is estimated to be 12.90 mg/L.

A study was performed for read across chemical 2-(4-chlorophenoxy)-2-methylpropanoic acid (882-09-7) (Toxicology Letters 142 (2003) 185-194) using Daphnia magna strauss for 48 hrs at different concentrations. The Daphnids was bred in ADaM, a culture medium imitating natural fresh water. Experiment was performed at temperature 20±1ᵒC and 16:8 photoperiod. Twenty daphnids younger than 24 h were used for the controls and each treatment subdivided in four replicates each containing five daphnids. Culture volume was 50 ml. After experiments, the EC 50 value for 2-(4-chlorophenoxy)-2-methylpropanoic acid (882-09-7) for short term toxicity to aquatic invertebrates was determined to be 72 mg/l on the basis of mobility.

Further, another study was performed for read across (R)-2-(4-Chloro-2-methylphenoxy) propionic acid (16484-77-8)(Ecotox database,2017)in Daphnia magna for 48 hr using freshwater in static condition. 5 daphnia magna were used having age of <24 hrs. After experiment the EC 50 value for (R)-2-(4-Chloro-2-methylphenoxy) propionic acid (16484-77-8) for Daphnia magna was determined to be 90.94 mg/l on the basis of intoxication.

Thus, based on the experimental key results of EC50= 74.7mg/L for 2-isopropyl-5-methylcyclohexanone (CAS no 1074-95-9), it can be considered that the substance isopropyl-5-methylcyclohexanone (CAS no 1074-95-9) was likely to be toxic to aquatic invertebrates at environmentally relevant concentrations and can be considered to be classified as aquatic chronic 3 as per the criteria of CLP regulation.