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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:
2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Version / remarks:
OECD 202 (2004)
Deviations:
not specified
GLP compliance:
yes
Specific details on test material used for the study:
- Name of test material: tert-butylbenzene
- IUPAC name: tert-Butylbenzene
- Molecular formula: C10H14
- Molecular weight: 134.22 g/mol
- Substance type: Organic
- Physical state: Liquid
Analytical monitoring:
not specified
Vehicle:
no
Details on test solutions:
The primary stock solution used in the range-finding test was prepared by dissolving 10 mg of the test substance in 40 mL of dilution water – M4 and the total volume was completed to 100 mL, resulting in a concentration of 100 mg.L-1. The secondary stock solutions of the 10 and 1 mg.L-1 were prepared by dilution of the primary stock solution.

The primary stock solution used in the definitive test was prepared by dissolving 50 mg of the test substance in 40 mL of dilution water – M4 and the total volume was completed to 500 mL, resulting in a concentration of 100 mg.L-1.
Test organisms (species):
Daphnia magna
Details on test organisms:
The test system used for this study is described below, according to Straus (1820):

Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Branchiopoda
Order: Cladocera
Family: Daphniidae
Genus: Daphnia
Species: Daphnia magna

Young Daphnia magna ≤ 24 hours old were obtained from the culture kept at the Ecotoxicology Laboratory, maintenance and cultivation records are archived at BIOAGRI.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
48 h
Hardness:
148.1 mg.L-1 CaCO3
Test temperature:
20.2 to 20.3°C
pH:
7.7 to 7.8
Dissolved oxygen:
8.0 mg.L-1
Nominal and measured concentrations:
In the range-finding test the exposure conditions were: control; 0.1; 1; 10 and 100 mg.L-1;
In the definitive test the exposure conditions were: control and 100 mg.L-1
Details on test conditions:
TEST SYSTEM
Test vessel: 30 mL glass beakers

In the range-finding test the exposure conditions were:

a) Total number of organisms per each tested concentration or control: 10;
b) Number of replicates per each tested concentration and control: 2;
c) Number of organisms per test container: 5;
d) Volume: 15 mL of test solution per test container, 3 mL to each Daphnia;
e) The organisms were distributed randomly in the test container. Firstly, three organisms were placed in each test container and, finally, two organisms were added to the container;
f) Nominal used concentrations: control; 0.1; 1; 10 and 100 mg.L-1;
g) Temperature of the test solutions: 20.2 to 20.3°C;
h) Photoperiod: 16 hours of light and 8 hours of dark;
i) Parameters evaluated: immobility after 24 and 48 hours; and still animals were considered unable to swim for a period of 15 seconds of observation after mild agitation of the flasks.

In the definitive test the exposure conditions were:

a) Total number of organisms per each tested concentration or control: 20;
b) Number of replicates per each tested concentration and control: 4;
c) Number of organisms per test container: 5;
d) Volume: 15 mL of test solution per test container, 3 mL to each Daphnia;
e) The organisms were distributed randomly in the test container. Firstly, three organisms were placed in each test container and, finally, two organisms were added to the container;
f) Nominal used concentrations: control and 100 mg.L-1;
g) Temperature of the test solutions: 20.0 to 20.3°C;
h) Photoperiod: 16 hours light and 8 hours dark;
i) Parameters evaluated: immobility after 24 and 48 hours; and still animals were considered unable to swim for a period of 15 seconds of observation after mild agitation of the flasks;
j) Analytical determination: content dissolved oxygen, pH of the test solutions and the test substance concentration were determined at the beginning of the test and after 48 hours.



TEST MEDIUM / WATER PARAMETERS
Source/preparation of dilution water: M4 (OECD 202)
pH: 7.7 to 7.8
Hardness: 148.1 mg.L-1 CaCO3
Dissolved oxygen: 8.0 mg.L-1
Temperature: 20.2 to 20.3 °C

Reference substance (positive control):
yes
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Results with reference substance (positive control):
- Results with reference substance valid? yes
- EC50 (24 h): 1.06 mg/L (95% confidence limits = 0.93 to 1.22 mg.L-1).
Validity criteria fulfilled:
yes
Conclusions:
The 48-hours EC50 value was not determined because the highest tested concentration of Tert-Butylbenzene, 100 mg/L, did not cause immobility to the test organisms. Therefore the 48-hours EC50 value of the tested substance is higher than 100 mg/L.
Executive summary:

Assessing the toxicity to aquatic invertebrates, Daphnia magna was exposed to tert-butylbenzene for 48 hours. The experiment was conducted according to OECD Guideline 202 (2004). The test gave a 48-h EC50 value of higher than 100 mg/L .

Description of key information

Study carried out according to guideline and with GLP compliance.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
100 mg/L

Additional information

In a static test conducted according to OECD 202 guideline an EC50 of higher than 100 mg/L after 48 h based on mean measured concentration has been determined.