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Ecotoxicological information

Short-term toxicity to fish

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Reference
Endpoint:
short-term toxicity to fish
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The source substance is the racemic form of the target substance d-tetramethrin. Tetramethrin does consist of 50% d- and l-form, and both do exist as cis and trans isomers. Hence, the target substance does consist of d-cis-tetramethrin, d-trans-tetramethrin, l-cis-tetramethrin and l-trans-tetramethrin, whereas the target substance only contains the first two (i.e. d-cis-tetramethrin, d-trans-tetramethrin).
Both, the source as well as the target substance, do have a cis/trans ratio of approximately 1/4 and obviously do share same molecular formula and mass, functional groups and other properties. Thus, the source substance by definition does contain ~50% of the d-form and the l-form is not expected to be significantly different with respect to its toxic properties. Acute toxicity to fish has been assessed in two acute fish toxicity tests (semi-static and flow through method) and one fish early life stage study, forming a solid foundation for assessing aquatic toxicity to fish. Accordingly, data do indicate that racemic tetramethrin and thus also d-tetramethrin is very toxic to fish and results of d-tetramethrin are not expected to significantly differ from the racemic mixture, considering that this contained the d-enantiomer as the main component.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The d-tetramethrin with a purity > 80 % does contain its corresponding l-form as an impurity in the range of < 7%, other impurities from the manufacturing process are individually below 1% (w/w) each. The source substance that has been tested was having a purity of approx. 98% as tetramethrin with a cis/trans ratio of 1/4 and a d-form/l-form ratio of ~50/50.
3. ANALOGUE APPROACH JUSTIFICATION
Source and Target substance do share identical structure and molecular weight, only differentiating by the fact that the source substance is a racemic mixture, whereas the target substance represents almost pure d-form. Thus, behaviour regarding toxicity to fish is expected not being affected significantly by stereochemistry, and being fully comparable, thus justifying using available data on fish toxicity properties on the racemic form for read-across to the d-enantiomer.
4. DATA MATRIX
Composition comparison
D-tetramethrin (target) tetramethrin (source)
D-trans tetramethrin 70 - 80% 40 – 50%
D-cis tetramethrin 10 - 20% 7 – 11 %
L-trans tetramethrin 0 – 5% 35 – 40%
L-cis tetramethrin 0 – 2% 7 – 11%
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
34.9 µg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
mortality
Conclusions:
The acute toxicity of test item tetramethrin has been tested on zebra fish under flow-through conditions. The NOEC, LOEC and LC50 values after 96 h, calculated based on the median of the measured exposure concentrations, were as follows:
96 h NOEC: 5.0 µg/L
96 h LOEC: 10.3 µg/L
96 h LC50: 34.9 µg/L (95% confidence range: 18.7 - 65.2 µg/L)
The flow-through conditions applied resulted in almost identical results as a previous semi-static fish toxicity study with danio rerio, also performed with racemic tetramethrin. The flow-through study results are used for hazard and risk assessment, as the flow through method was more appropriate maintaining concentrations and was performed more recently. Both results are considered adequate also for assessing the toxicity of d-tetramethrin towards fish.

Description of key information

The acute toxicity of the test item d-tetramethrin to zebra fish (Danio rerio) was determined a 96-hour flow-through test according to the OECD 203 using racemic tetramethrin resulting in:

96 h NOEC: 5.0 µg/L

96 h LOEC: 10.3 µg/L

96 h LC50: 34.9 µg/L (95% confidence range: 18.7 - 65.2 µg/L)

These findings were supported by an older acute fish toxicity study with semi-static exposure (danio rerio as test species) finding an LC50 (96h) of 33 µg/L. Both studies do show absolutely comparable results and the flow through study has been chosen as key study for hazard and risk assessment.

Key value for chemical safety assessment

LC50 for freshwater fish:
34.9 µg/L

Additional information