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Short-term toxicity to fish

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Reference
Endpoint:
short-term toxicity to fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1998
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
OECD Guideline 203 (Fish, Acute Toxicity Test)
Version / remarks:
(1992)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material: not reported
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 0.5 and 5.0 mg/L were measured during 96 hours as a limit test.
Vehicle:
yes
Details on test solutions:
2,2'-methylenebis(6-tert-butyl-4-methylphenol) was mixed with DMF/Castor oil HCO-40 (3/1(w/w); 20 times weight to the substance) and dissolved into dilution water to prepare the nominal concentration of 5.0 mg/L for exposure (No precipitations as well as emulsions were observed at this nominal concentration). Due to low water solubility of 2,2'-methylenebis(6-tert-butyl-4-methylphenol), homogenous solution could be attained only at (and less than) this nominal concentration with the maximum allowable dispersant concentration of 100 mg/L.
Dilution water: dechlorinated tap water of the city Takarazuka, CaCO3 content of 55.2 mg/L equal 3.1 °dH, pH = 8.1.
Test organisms (species):
Oryzias latipes
Details on test organisms:
Test fish
Acclimated under test condition (water quality, temperature, etc.) for more than 12 days, and no mortality was observed for 7 days before the exposure. Fed daily with commercial fish feed (TetraMin staple food) and starved for 24 hr before the exposure.
The fish body weight and body length measured at the initiation of exposure were 0.17 g (0.16 -0.20 g) and 2.2 cm (2.0 – 2.3 cm) on the average.
The test fish was purchased from a fish farm Izumoto, Osaka on 1998-12-22.
The Batch number was K-981222.
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Remarks on exposure duration:
no remarks
Post exposure observation period:
not reported
Hardness:
55.2 mg CaCO3/L = 3.1 °dH
Test temperature:
ranged from 23.7 to 23.8 °C
pH:
ranged from 7.5 to 7.8
Dissolved oxygen:
ranged from 5.8 to 8.3 mg/L (more than 60 % saturation)
Salinity:
not reported
Nominal and measured concentrations:
nominal concentration: 5.0 mg/L
measured value: 4.0 mg/L (initiation of exposure) and 4.3 mg/L after 48 hr of exposure
Note: The geometric mean value was 4.1 mg/L, corresponding to 83 % of the nominal concentration. Thus, the results (e.g. LC50 values) were expressed based on the nominal exposure concentrations.
Details on test conditions:
TEST SYSTEM
- Test vessel: 5 L glass aquarium (inner size: 21 x 16 x 23 cm)
- No. of organisms per vessel: 10 fish
- No. of vessels per concentration (replicates): one
- No. of vessels per control (replicates): one
- No. of vessels per vehicle control (replicates): one
- Photoperiod: 16 h light / 8 h dark
- Temperature: 24 ± 1 ℃
- Exposure: 96 hours
- Feedind: none
Reference substance (positive control):
yes
Remarks:
Copper sulfate (5 hydrate), lot No.PAH2068 from Wako Pure Chemical Industries, Ltd.
Duration:
24 h
Dose descriptor:
LC50
Effect conc.:
> 5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
48 h
Dose descriptor:
LC50
Effect conc.:
> 5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
72 h
Dose descriptor:
LC50
Effect conc.:
> 5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
> 5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Details on results:
Biological observations/Abnormal responses: Visual inspections of test aquaria (i.e. Control, Solvent control and 5.0 mg/L of Nominal concentration) conducted every 24 h revealed that no toxic symptoms in fish (e.g. abnormal respiration, abnormal swimming, inverted, etc.) were observed during the experiment.
Results with reference substance (positive control):
The 96 h-LC50 value determined was 4.0 mg/L.
Reported statistics and error estimates:
Due to low water solubility of 2,2'-methylenebis(6-tert-butyl-4-methylphenol), limit exposure experiment with only one nominal concentration was conducted. Thus, no statistical method for the determination of LC50 value was employed. A regression line for GC-MS analyses was derived by least square calculations. Numerical values were rounded according to the method specified in JIS.

Cumulative mortality

Measured Concentration [mg/L]

Cumulative Number of Dead (Percent Mortality)

24 h

48 h

72 h

96 h

Control

0 (0)

0 (0)

0 (0)

0 (0)

Solvent Control

0 (0)

0 (0)

0 (0)

0 (0)

5.0 mg/L

0 (0)

0 (0)

0 (0)

0 (0)

 

Highest concentration in 0% mortality/Lowest concentration in 100% mortality:

Exposure period (h)

Highest concentration in 0% mortality

Lowest concentration in 100% mortality

24

5.0

>5.0

48

5.0

>5.0

72

5.0

>5.0

96

5.0

>5.0

Validity criteria fulfilled:
yes
Remarks:
(-The mortality in the control did not exceed 10 % by the end of the test. - The dissolved oxygen concentration remained above 60 % of the air-saturation value throughout the exposure period. - The pH did not vary by more than 1 unit.)
Conclusions:
The acute toxicity of fish (Oryzias latipes) to 2,2'-methylenebis(6-tert-butyl-4-methylphenol) was tested in a semi-static test. After 96 hours of exposure a LC50 more than 5.0 mg/L was observed at a limit test concentration of 5.0 mg/L. No toxic symptoms were observed during the study.
Executive summary:

A study was performed to assess the acute toxicity of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) to Oryzias latipes under semi-static condition. The study was conducted in accordance to the OECD guideline for Testing of Chemicals No. 203 'Fish, Acute Toxicity Test' (1992).

Due to low water solubility of the substance, the limit experiment was conducted with the maximum dispersable concentration of 5.0 mg/L.

The determined 96 h-LC50 value was more than 5.0 mg/L based on the nominal concentration. No toxic symptoms were observed during the study.

Experimental designs and results were well documented and prescribed conditions in the guideline were well satisfied.

Description of key information

The lowest 96h-LC50 is reported to be >5 mg/L (Environmental Agency of Japan, 1999a). The assessment of DBMC in OECD SIDS (2001) is also based on this value. As the reported LC50 is above the water solubility no PNEC can be derived based on this result.

Key value for chemical safety assessment

Additional information

The above study is assessed in the OECD SIDS Report (2001) and the PBT Report (2009) of the European Chemical Bureau (ECB). This test can be regarded as reliable without restrictions. However the relevant test was performed with a solubilizer in order to overcome the low water solubility of 0.007 mg/L. As a consequence, no effects have been observed up to the limit of the water solubility. No PNEC can be derived based on this result.