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Short-term toxicity to fish

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Description of key information

The 96 hour LC50 was determined to be 0.27mg/l and the NOEC was determined to be 0.18 mg/l.

Key value for chemical safety assessment

LC50 for freshwater fish:
0.27 mg/L

Additional information

Method:

A 96 hour study was carried out under semi static conditions according to OECD guideline 203 to investigate the acute toxicity of the test material to rainbow trout.

5 test concentrations (0.10, 0.18, 0.32, 0.56 and 1.0 mg/l) plus 1 control (including 100µl/l auxiliary solvent) were tested, with 10 animals per test concentration.

The study was carried out in darkness since preliminary analytical data showed "DIXT" to be unstable in water when exposed to light.

Results:

Analysis of the mortality data gave the following results:

Time (h)

LC50 (mg/l)

95% confidence limits (mg/l)

3

>1.0

-

6

>1.0

-

24

0.37

0.32 – 0.44

48

0.27

0.22 - 0.32

72

0.27

0.22 – 0.32

96

0.27

0.22 – 0.32

 

Highest test concentration resulting in 0% mortality = 0.18 mg/l

Lowest test concentration resulting in 100% mortality = 0.56 mg/l

It was not possible to quantify the test concentrations due to the reaction of the test material with the surfactant (Tween 80) and the degradation of DIXT in water. Hence the nominal test concentrations were used in the calculation of LC50 values.

The 96 hour LC50 was determined to be 0.27 mg/l and the NOEC was determined to be 0.18 mg/l.

A variety of approved dispersing agents, such as HC0 40 (hydrogenated castor oil), ethanol, acetone, DMF, DMSO etc., were used both prior to and after the definitive test but only the formula of 20% Tween 80 in tetrahydrofuran was found to give a satisfactory dispersion of the test substance in water. Although the test substance is now known to be unstable under these conditions all other preparations were unsuitable for testing. However, because of the instability/reactivity of the test substance, considerable caution should be exercised in the interpretation of these data.