Trimethoxy(methyl)silane

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:

2007-06-29 to 2007-07-12

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling: Measurement of test concentrations in one replicate test chamber of each treatment group at test initiation and at test termination.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Test solutions were prepared by direct addition of test article to dilution water (100 and 200 mg/L treatment groups) or by addition of  stocks prepared in DMF (13, 25 and 50 mg/L treatment groups).

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM

- Test fish (age/length/weight, loading, pretreatment):  Age 50 Days/Mean Total Length 3.7 cm (Range 3.4 to 4.0 cm)/Wet Weight 0.37 g (Range 0.30 to 0.51 g), Flow-Through Loading 0.035 g/L/24 hours, Instantaneous Loading 0.25 g/L, Fish were acclimated to laboratory conditions for a minimum of 2 weeks prior to the test.

- Supplier: Thomas Fish Company

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

Hardness 138 mg/L as CaCO3, Alkalinity 74 mg/L as CaCO3

Test temperature:

11.4 - 12.1ºC

pH:

7.3-7.7

Dissolved oxygen:

7.6-9.1 mg/L

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: Negative Control, Solvent Control, 13, 25, 50, 100 and 200 mg/L

Mean measured concentrations: The results are interpreted with reference to mean measured concentrations.

Details on test conditions:

- Exposure vessel type:  25-L polyethylene aquaria containing 15-L of test solution

- Number of replicates, fish per replicate:  Two replicates per treatment, 10 Fish per replicate

- Dilution water source:  Dechlorinated Municipal Water

- Dilution water chemistry:  Hardness 138 mg/L as CaCO3, Alkalinity 74 mg/L as CaCO3, Conductivity 362 µmhos/cm, pH 7.6, Total Residual Chlorine <10  g/L        

- Vehicle/solvent and concentrations:  The solvent control, 13, 25 and 50 mg/L treatment groups contained 0.1 mL/L DMF.  No solvent was delivered in the 100 and 200 mg/L treatment groups.

- Water chemistry in test:  DO, pH and temperature measured in each test chamber daily

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 110 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 110 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 200 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 200 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Reported statistics and error estimates:

There was no significant mortality in any treatment; statistical analysis was therefore not required.

Sublethal observations / clinical signs:

Table 1. Test results

Nominal concentration (mg/L)	Mean measured concentration (mg/L)	Percentage mortality after 24 hours	Percentage mortality after 48 hours	Percentage mortality after 72 hours	Percentage mortality after 96 hours
0 (Control)	0	0	0	0	0
0 (Vehicle control)	0	0	0	0	0
13	0	0	0	0	0
25	0	0	0	0	0
50	0	0	0	0	0
100	0	0	0	0	0
200	0	0	0	0	5

       
24-Hour LC50:  >110 mg/L (not calculable)
48-Hour LC50:  >110 mg/L (not calculable)
72-Hour LC50:  >110 mg/L (not calculable)
96-Hour LC50:  >110 mg/L (not calculable)

Biological observations:  All surviving fish appeared normal and healthy.   
Lowest test substance concentration causing 100% mortality:  None
Mortality of controls:  None
Abnormal responses:  None
Any observations, such as precipitation that might cause a
difference between measured and nominal values:  All test
solutions were clear and colorless.

Validity criteria fulfilled:

yes

Conclusions:

A 96-hour LC50 value of >110 mg/L and NOEC of ≥110 mg/L have been determined for the effects of the substance on mortality of Oncorhynchus mykiss. Under the flow-through conditions used in the test the results reflect exposure to the test substance.

Description of key information

Short-term toxicity to fish: 96-hour LC₅₀ >110 mg/l (measured concentration); mortality of Oncorhynchus mykiss.

Additional information

A 96-hour LC₅₀ value of >200 mg/l, based on nominal concentration (highest concentration tested), and >110 mg/l, based on measured concentration, has been determined for the effects of the registered substance on mortality of Oncorhynchus mykiss (Dow Corning Corporation, 2007). The test was carried out in accordance with test guideline OECD 203 and in compliance with GLP. Under the flow-through conditions used in the test it is likely that the fish were exposed to a mixture of the parent substance and its hydrolysis products. This is reflected in the nominal versus measured test concentrations.

To support the chemical safety assessment of the hydrolysis product, methylsilanetriol (CAS 2445-53-6; EC No. 219-489-9), data have been read-across from a structural analogue which rapidly hydrolyses to methylsilanetriol. A 96-hour LC₅₀ value of >500 mg/l (nominal concentration) (highest concentration tested) has been determined for the effects of triethoxy(methyl)silane (CAS 2031-67-6; EC No. 217-983-9) on mortality of Danio rerio (Hazelton, 1994), carried out in accordance with EU test Method C.1 and in compliance with GLP.

In view of the test media preparation method/exposure regime it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance. The results may be expressed in terms of concentration of the hydrolysis product, methylsilanetriol, by applying a molecular weight correction: (MW of silanol = 94.14 / MW of parent = 178.31) * (CONCENTRATION OF PARENT = >500) = >264 mg/l as methylsilanetriol.

Refer to Section 6 endpoint summary, Section 7.0 of CSR, for further discussion of the approach to chemical safety assessment for this registration substance, and justification for read-across used.