3-chloropropyltrimethoxysilane

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1993-06-01 to 1993-06-04

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

no date or version given

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

The dissolved organic carbon analysis (DOC) concentration of the stock solution used to prepare the test media was determined and used as the basis for setting the treatment levels.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A stock solution was made by dissolving the test substance to obtain 1 g/l concentration in water and stirred for 18 h. The solution was filtered and served as the initial solution for testing.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM

- Strain: 86.81.SAG

- Source (laboratory, culture collection): Institute for Water, Ground and Air Hygiene, Berlin (Germany)

- Age of inoculum (at test initiation): 3 days

- Method of cultivation: A pre-culture is produced from an original culture by super-inoculation three days before the test begins. From this culture the test cultures are inoculated at a density of about 20000 cells/ml.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

No data

Test temperature:

24 ± 2ºC

pH:

Start of test: 7.6 - 7.8

End of test: 7.6 - 8.5

Dissolved oxygen:

No data

Salinity:

Not applicable

Nominal and measured concentrations:

The measured DOC concentration in the stock solution was 356 mg/L corresponding to 981 mg/L of the test substance.

Nominal concentrations based on measured concentrations in stock solution: 0 (Control), 59, 98, 167, 294, 491, and 883 mg/L.

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Type: open Erlenmeyer flasks

- Material: glass

- Aeration: none

- Initial cells density: 20000 cells/ml

- Control end cells density:1150000 cells/ml (Test 2), 970000 cells/ml (Test 4)

- No. of vessels per concentration (replicates): 5

- No. of vessels per control (replicates): 8

GROWTH MEDIUM

- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS

- Culture medium different from test medium: no

- Intervals of water quality measurement: start and end of test

OTHER TEST CONDITIONS

- Sterile test conditions: yes

- Adjustment of pH: no

- Photoperiod: continuous

- Light intensity and quality: 8000 Lux

EFFECT PARAMETERS MEASURED: Determination of cell concentrations after 24, 48 and 72 hours by spectrophotometer (absorption at 685 nm)

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.7-1.8

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

167 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

514 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 833 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

241 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 883 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

- Exponential growth in the control: yes
- Any stimulation of growth found in any treatment: yes, in the 98 mg/l treatment stimulation of growth was found at 24, 48 and 72-hour measurements

Reported statistics and error estimates:

The ECx values were determined by Probit analysis. The NOEC was determined by visual examination of the raw data.

Table 1. Test results

Nominal concentration (mg/L)	Cell concentration at start of test (cells/ml)	Cell concentration after 24 hours (cells/ml)	Cell concentration after 48 hours (cells/ml)	Cell concentration after 72 hours (cells/ml)
0 (Control)	20000	70000	280000	790000
59	20000	70000	270000	770000
98	20000	70000	300000	850000
167	20000	70000	260000	730000
294	20000	60000	240000	650000
491	20000	80000	240000	590000
883	20000	80000	210000	390000

72 h EbC50: >883 mg/l

72 h EbC10: 241 mg/l

Validity criteria fulfilled:

yes

Conclusions:

A 72-hour EC50 value of >833 mg/L and a NOEC of 167 mg/L have been determined for the effects of the test substance on growth rate of Scenedesmus subspicatus (new name: Desmodesmus subspicatus). It is likely that the test organisms were predominantly exposed to the hydrolysis products of the substance.

Description of key information

72-hour EC₅₀ >833 mg/l and NOEC 167 mg/l (measured based on DOC in the stock solution) (OECD guideline 201). The observations in this study are attributed to the exposure of test organisms to the silanol hydrolysis product, (3-chloropropyl)silanetriol, in the test system. The EC₅₀ and NOEC are equivalent to >657 and 132 mg/l, respectively, when expressed in terms of the silanol hydrolysis product.

Additional information

A 72-hour EC₅₀ value of >833 mg/l and an EC₁₀ of 514 mg/l (measured) have been determined for the effects of the registered substance (3-chloropropyl)trimethoxysilane (CAS 2530-87-2) on growth rate of Scenedesmus subspicatus . A 72-hour NOEC value of 167 mg/l has also been derived for the effects of the test substance on cell number of Scenedesmus subspicatus (Hüls, 1993). In view of the test media preparation method and exposure regime it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance. The nominal test concentrations are supported by DOC analysis of the stock solution. The results may be expressed in terms of concentration of the silanol hydrolysis product, (3-chloropropyl)silanetriol, by applying a molecular weight correction: (MW of silanol = 156.64 / MW of parent = 198.72) * >833 mg/l = EC₅₀, EC₁₀ and NOEC values of >657, 405 and 132 mg/l, respectively.

 

Above a concentration of approximately 1000 mg/l, dimeric / oligomeric, cyclic or cross-linked condensation products could potentially form over time in the aqueous test media. There was no mention of undissolved material (parent substance or precipitated products) in the study report for this test. 

Refer to the discussion in the Section 6 endpoint summary (Section 7.0 of CSR) for further discussion of the approach to chemical safety assessment for this registration substance.