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Ecotoxicological information

Long-term toxicity to fish

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Reference
Endpoint:
fish early-life stage toxicity
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Justification for type of information:
Data from structural related substance
Reason / purpose:
read-across: supporting information
Principles of method if other than guideline:
Method: Federal Register 50:TSCA Test Standard No. 797.1600. This test is comparable with the OECD-Guideline 210.
GLP compliance:
yes
Specific details on test material used for the study:
- Common name: 2-mercaptobenzothiazole
Analytical monitoring:
yes
Vehicle:
yes
Test organisms (species):
Oncorhynchus mykiss (previous name: Salmo gairdneri)
Details on test organisms:
Unfertilised rainbow trout eggs and sperm were individually packaged and shipped under refrigeration from Mount Lassen Farm, a certified disease-free trout hatchery located in Red Bluffs, California.
Test type:
flow-through
Water media type:
freshwater
Total exposure duration:
89 d
Hardness:
26 - 30 mg/L CaCO3 = 1.46 - 1.68 °dH
Test temperature:
12 +/- 2°C
pH:
6.9 - 7.4
Dissolved oxygen:
7.1 - 11.2 mg/L
Duration:
89 d
Dose descriptor:
NOEC
Effect conc.:
0.041 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
larval development
Duration:
89 d
Dose descriptor:
LOEC
Effect conc.:
0.078 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
larval development
Details on results:
MATC = Maximum Acceptable Toxicant Concentration
geometric mean = 0.057 mg/l

At the termination of the test, data obtained on embryo viability, survival at hatch, larval survival and larval growth (wet weight and total length) were statistically analysed to establish treatment level effects.

Validity criteria fulfilled:
not applicable
Conclusions:
For benzothiazole-2-thiol as hydrolysis product of TBBS, the Maximum Acceptable Toxicant Concentration (MATC) in an early-life stage test on rainbow trout was determined to be 0.041 - 0.078 mg/L within 89 days. The concentration of 0.078 mg/L was reported as LOEC and 0.041 mg/L as NOEC.
Executive summary:

For benzothiazole-2-thiol as hydrolysis product of TBBS, the Maximum Acceptable Toxicant Concentration (MATC) in an early-life stage test on rainbow trout was determined to be 0.041 - 0.078 mg/L within 89 days. The concentration of 0.078 mg/L was reported as LOEC and 0.041 mg/L as NOEC.

Description of key information

For benzothiazole-2-thiol (MBT) as hydrolysis product of TBBS, the Maximum Acceptable Toxicant Concentration (MATC) in an early-life stage test on rainbow trout was determined to be 0.041 - 0.078 mg/L within 89 days. The concentration of 0.078 mg/L was reported as LOEC and 0.041 mg/L as NOEC. 

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater fish:
0.041 mg/L

Additional information

There is no direct data available regarding the chronic effect of TBBS on fish. TBBS shows a fast hydrolysis under environmental relevant pH (half-life 9.53 h at pH 7, 25 °C), therefore effects in water are mainly based on the hydrolysis product. The endpoint chronic toxicity is covered by MBT as identified hydrolysis product. During short-term toxicity testing fish are more sensitive towards MBT (96 h LC50 0.73 mg/L) than towards TBBS (96 h LC50 1.38 mg/L). Therefore, it is not expected that chronic toxicity of TBBS is higher than for MBT. The MBT study result is used for risk assessment.