1,1,1,3,3,3-hexamethyldisilazane

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1994-03-21 to 1994-03-25

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.1 (Acute Toxicity for Fish)

Version / remarks:

Cited as Directive 92/69/EEC, C.1

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: All concentrations at the start of the test and after 24, 48, 72 and 96 hours in fresh and/or old media as applicable

- Sampling method: Not reported

- Sample storage conditions before analysis: Not reported

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Test media prepared by mixing for 18 h followed by filtration.

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

TEST ORGANISM

- Common name: Zebrafish

- Source: West aquarium, Bad Lauterberg, Germany

- Length at study initiation (length definition, mean, range and SD): 3.0 cm +/-0.5 cm

- Feeding during test: none

ACCLIMATION

- Acclimation period: at least 14 days

- Acclimation conditions (same as test or not): yes

- Type and amount of food: TetraMin® at 1% of body weight

- Feeding frequency: Daily

- Health during acclimation (any mortality observed): The fish exhibit normal behaviour and are free from visible signs of disease at the start of the t
est.

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Hardness:

220 mg/L as CaCO3

Test temperature:

20ºC

pH:

7.8-8.7

Dissolved oxygen:

78-99% ASV

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal test concentrations: 0 (Control), 120, 180, 250, 350 and 500 mg/L

Mean measure concentrations: 0, 25, 41, 56, 77 or 110 mg/L.

Details on test conditions:

Ten fish per 20 L test aquarium were exposed for 96 hrs to each of the treatments.

Dilution water was Tap water (Gelsenwasser AG)

According to an analysis certificate, the TOC background value is 3  mg/l.

Reference substance (positive control):

no

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

56 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

mortality (fish)

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

88 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: tst substance hydrolysis products

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC100

Effect conc.:

110 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

mortality (fish)

Details on results:

- Mortality of control: 0%

Reported statistics and error estimates:

The LC50 was determined graphically from a plot of mortality versus log mean test substance concentration

Sublethal observations / clinical signs:

Table 1. Test results

Nominal test substance concentration (mg/L)	Mean measured concentration over the test (mg/L)	Percentage mortality at end of test
0 (Control)	-	0
120	25	0
180	41	0
250	56	10
350	77	20
500	110	100

    

Validity criteria fulfilled:

yes

Conclusions:

A 96 LC50 value of 88 mg/L and a NOEC of 56 mg/L have been determined for the effects of the test substance on mortality of Brachydanio rerio. It is likely that the test organisms were predominantly exposed to the hydrolysis products of the substance.

Description of key information

(Key) Short-term toxicity to fish: 96-hour LC₅₀ 88 mg/l (measured) (EU method C.1), registration substance. The LC₅₀ is equivalent to 49 mg/l when expressed in terms of the silanol hydrolysis product, trimethylsilanol and 9.3 mg/l in terms of NH₃.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

88 mg/L

Additional information

A reliable acute toxicity test result for 1,1,1,3,3,3-hexamethyldisilazane (CAS 999-97-3) is available for freshwater fish (Brachydanio rerio): 96-hour LC₅₀ of 88 mg/l based on measured concentrations. It is likely that the test organisms were exposed to the hydrolysis products of the substance.

A supporting study of unassignable reliability is available for the effects of 1,1,1,3,3,3-hexamethyldisilazane on the mortality of Pimephales promelas, reporting a 96-hour LC₅₀ value of 167 mg/l.