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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:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
The lowest and highest nominal concentrations (3.2 mg/l and 1000 mg/l) were analytically tested direct after the preparation of the solution and after the 48 h exposure time.
Vehicle:
no
Test organisms (species):
Daphnia magna
Details on test organisms:
Phylum: Clone culture of the Geman health authority, Berlin.
Laboratory culture of the Bayer AG Leverkusen.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
15.6°dH
Test temperature:
21.0-22°C
pH:
8.0 - 8.2
Dissolved oxygen:
8.3 - 8.9 mg/l
Nominal and measured concentrations:
The actual concentrations of test solutions with the lowest (3.2 mg/L) and highest (1000 mg/L) nominal concentrations were analyzed at both the beginning and the end of the exposure. The analyzed results were always below 0.3mg/L.
Duration:
48 h
Dose descriptor:
other: EC05
Effect conc.:
54 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: 24 - 85 mg/l
Duration:
48 h
Dose descriptor:
EC10
Effect conc.:
73 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: 37 - 108 mg/l
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
211 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: 151 - 294 mg/l

The actual concentrations of test solutions with the lowest (3.2 mg/L) and highest (1000 mg/L) nominal concentrations were analyzed at both the beginning and the end of the exposure. The analyzed results were always below 0.3mg/L. MBTS has an estimated water solubility in the range of 0.27 - 0.37 mg/L at 25°C and hence the result from this study can be interprated as no effect up to water solubility of MBTS. The observed effect is most probably due to the direct impact from undissolved substance.

Conclusions:
No acute toxicity of MBTS to Daphnia magna was observed up to its water solubility (<=0.3 mg/L) at pH 8.0-8.2 and 21-22°C.
Executive summary:

No acute toxicity of MBTS to Daphnia magna was observed up to its water solubility (<=0.3 mg/L) at pH 8.0-8.2 and 21-22°C according to EU Method C.2 (Acute Toxicity for Daphnia) (Bayer AG, 1993).

Description of key information

No acute toxicity of MBTS to Daphnia magna was observed up to its water solubility (<=0.3 mg/L) at pH 8.0-8.2 and 21-22°C according to EU Method C.2 (Acute Toxicity for Daphnia) (Bayer AG, 1993).

Key value for chemical safety assessment

Additional information

Monsanto (1979) reported a 48h-EC50 of 82 mg/l of MBTS to Daphnia magna without analytical monitoring. This value was based on nominal concentration and precipitations were observed in all concentrations tested from 10 to 100 mg/L; and hence the observed effect is due to both dissolved and undissolved substance.