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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:
02.10.2017 - 04.10.2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Experimental test result performed using standard test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Principles of method if other than guideline:
Short term toxicity of test chemical to aquatic invertebrates was performed according to the OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test) in a static system.
GLP compliance:
no
Analytical monitoring:
no
Details on test solutions:
The stock solution 100.0 mg/l was prepared by dissolving dark orange powder in reconstituted water. The test solutions of required concentrations 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
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Remarks on exposure duration:
48 hr ± 1 hr
Test temperature:
20±1°C
pH:
Sample at concentration 16.0 mg.I'1: pH = 8.0 changed to pH = 7.9 during the test,
control: pH = 7.8 changed to pH = 7.9 during the test
Dissolved oxygen:
higher than 8.7 mg/L at the end of test
Nominal and measured concentrations:
1,2,4,8,16 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.:
6.2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: 95 % CI :3.5-11.2
Results with reference substance (positive control):
- Results with reference substance valid
- EC50: 0.76 mg/L (24 hours)
Reported statistics and error estimates:
EC50 was calculated using non linear regression by the software Prism 4.0
Validity criteria fulfilled:
yes
Conclusions:
The median effective concentration (EC50) for the test substance,2,3-dimethylphenol (526-75-0), in Daphnia magna was determined to be 6.2 mg/L (95 % CI :3.5-11.2) on the basis of mobility inhibition effects in a 48 hour study.
Executive summary:

Aim of this study was to assess the short term toxicity of test chemical 2,3-dimethylphenol (526-75-0) to aquatic invertebrates daphnia magna. Study was performed according to the OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test) in a static system for the total exposure period of 48 hrs. The stock solution 100.0 mg/l was prepared by dissolving dark orange powder in reconstituted water. The test solutions of required concentrations were prepared by mixing the stock solution of the test sample in reconstituted water. 1,2,4,8,16 mg/l concentrations were used in the study. Effects on immobilisation were observed for 48 hours. With the test substance one positive control Potassium dichromate (K2Cr2O7) was also run simultaneously. After the exposure of chemical, effect concentration EC50 was calculated using nonlinear regression by the software Prism 4.0. The median effective concentration (EC50) for the test substance 2,3-dimethylphenol (526-75-0), in Daphnia magna was determined to be 6.2 mg/L (95 % CI :3.5-11.2) on the basis of mobility inhibition effects in a 48 hour study. Based on the EC50 value, substance is likely to be hazardous to aquatic invertebrate and can be classified as aquatic chronic 2 category as per the CLP classification criteria.

Description of key information

The median effective concentration (EC50) for the test substance,2,3-dimethylphenol (526-75-0), in Daphnia magna was determined to be 6.2 mg/L (95 % CI :3.5-11.2) on the basis of mobility inhibition effects in a 48 hour study.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
6.2 mg/L

Additional information

Short term toxicity to aquatic invertebrates for 2, 3-Dimethylphenol (526-75-0) is summaries with key and supporting studies are as follows:

In an experimental key study report,aim of this study was to assess the short term toxicity of test chemical 2,3-dimethylphenol (526-75-0) to aquatic invertebrates daphnia magna. Study was performed according to the OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test) in a static system for the total exposure period of 48 hrs. The stock solution 100.0 mg/l was prepared by dissolving dark orange powder in reconstituted water. The test solutions of required concentrations were prepared by mixing the stock solution of the test sample in reconstituted water.1,2,4,8,16 mg/l concentrations were used in the study. Effects on immobilisation were observed for 48 hours. With the test substance one positive control Potassium dichromate (K2Cr2O7) was also run simultaneously. After the exposure of chemical, effect concentration EC50 was calculated using nonlinear regression by the software Prism 4.0. The median effective concentration (EC50) for the test substance 2,3-dimethylphenol (526-75-0), in Daphnia magna was determined to be 6.2 mg/L (95 % CI :3.5-11.2) on the basis of mobility inhibition effects in a 48 hour study. Based on the EC50 value, substance is likely to be hazardous to aquatic invertebrate and can be classified as aquatic chronic 2 category as per the CLP classification criteria.

In another supporting study,short-term toxicity test was conducted to 2, 3-Dimethylphenol (526-75-0) by Kahruet,al(Environ Toxicol 15: 431-442, 2000) to determined the toxicity of 2, 3-dimethyl phenol to Daphnia magna. Test plates with Daphnia magna neonates (Daphtoxkit Fᵀᴹ manga) were incubated for 48 h at 20 deg C in the dark. Immobilization of the organism was observed after exposure to 2, 3-dimethyl phenol. The LC50 value of 2, 3-dimethylphenol was considered to be 11 mg/l for Daphnia magna.

Supporting study by James Devillers (Science of The Total Environment Volume 76, Issue 1, 15 September 1988, Pages 79-83) short-term toxicity to aquatic invertebrates for 2, 3-dimethyl phenol, in Daphnia magna when exposed for 24h.Daphnia magna were found to be immobilized at the concentration of 13.615 mg/l .Therefore the IC50 was considered to be 13.615 mg/l for 2, 3-dimethyl phenol when Daphnia magna were exposed for 24h under static condition.

Another supporting study by Kahru et, al(Environ Toxicol 15: 431-442, 2000) was conducted to find out the toxicity of 2, 3-dimethyl phenol to Thamnocephalus platyurus. Test plates with Thamnocephalus platyurus larvae (Thamnotoxkit F) was incubated at 25°C for 24 h in the dark. Mortality was observed after exposure to 2, 3-dimethyl phenol. The LC50 value of 2, 3-dimethylphenol was considered to be 6 mg/l for Thamnocephalus platyurus.

Study of Daphnia magna was carried out for 48 hrs from HSDB, 2011 to determine the effect of test substance 2, 3-Dimethylphenol on test organism. After the experiment the LC50 value was determined to be 16.0 mg/l.

Based on the above key and supporting studies it was considered that 2, 3-Dimethylphenol was considered to be hazardous to aquatic invertebrates.

Thus, based on the LC50/EC50 values mentioned for invertebrates in the range 6 -16 mg/L, the substance 2, 3-dimethyl phenol can be considered as toxic to aquatic organisms. and thus, classified in Aquatic Chronic category 2 as per the CLP regulation.