(3-chloropropyl)dimethoxymethylsilane

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:

1994-05-24 to 1994-05-27

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Guideline study without restrictions. The study was conducted according to the appropriate OECD test guideline, and in compliance with GLP.

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 34, 57, 95, 161, 284, 473 and 851 mg/L.

- Sampling method: Samples of the test media were taken for analysis at the start and end of the test.

- Sample storage conditions before analysis: not described

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Nominal test concentrations of 34, 57, 95, 161, 284, 473 and 851 mg/L were prepared by dilution of a 1000 mg/l nominal concentration stock solution. The stock solution was prepared by stirring for 18 h followed by filtration and contained 432 mg/l of dissolved organic carbon equivalent to 945 mg/L of test substance.

- Controls: Dilution water (algal growth medium)

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM

- Strain: CHODAT (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. The cell concentration is determined from a calibration curve of absorbance at 685 nm versus cell density.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

not reported

Test temperature:

24+/-2ºC

pH:

8.4-8.5 at start of test

7.9-9.6 at end of test

Dissolved oxygen:

not reported

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations: 0(Control), 34, 57, 95, 161, 284, 473 and 851 mg/L.

Measured concentrations were within 20% of nominal. The results are therefore reported with reference to nominal concentrations.

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: 1050000 cells/mL

- 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: spectrophotometer (absorption at 685 nm)

- Other:

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.7

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

ca. 57 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

growth rate

Remarks:

and biomass

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

137 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

99 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

437 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

262 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

biomass

Details on results:

- Exponential growth in the control (for algal test): yes

- Any stimulation of growth found in any treatment: no

Reported statistics and error estimates:

The area under the growth curve (biomass) and growth rate parameters were calculated from the cell concentration data in accordance with the description of the test method.

The EC50 values were determined by probit analysis (Cavalli-Sforza, L. (1972). Biometrie. Gustav Fischer Verlag, Stuttgart, pp. 212). The NOEC was determined by t-test.

Table 1. Test results

Nominal test substance concentration (mg/L)	Mean cell concentration at start of test (cells/mL)	Mean cell concentration after 24 hours  (cells/mL)	Mean cell concentration after 48 hours  (cells/mL)	Mean cell concentration after 72 hours  (cells/mL)
0 (Control)	20000	80000	250000	1050000
34	20000	80000	280000	1010000
57	20000	80000	270000	990000
95	20000	80000	250000	860000
161	20000	80000	230000	650000
284	20000	70000	160000	450000
473	20000	50000	100000	120000
851	20000	40000	40000	40000

Table 2. Results of analysis of test media

Nominal test substance concentration (mg/L)	Measured concentration at start of test (mg/L)	Measured concentration at end of test (mg/L)	Concentration used as the basis for assessing effects (mg/L)
34	36	33	34
57	60	56	57
95	93	85	95
161	168	152	161
284	295	273	284
473	462	420	473
851	923	739	851

Validity criteria fulfilled:

yes

Conclusions:

A 72-hour EC50 value of 437 mg/L and NOEC of approximately 57 mg/L have been determined for the effects the test substance on growth rate of Scenedesmus subspicatus. The results are interpreted with reference to nominal concentrations of the test substance. However it is likely that the test organisms were predominantly exposed to the hydrolysis products of the substance during the study, and not the parent compound.

Description of key information

72-hour E_rC₅₀ 437 mg/l, E_rC₁₀ 137 mg/l and NOEC 57 mg/l (nominal concentration) (EU Method C.3 (Algal Inhibition test)), read-across from an analogous/structurally related substance, 3-chloropropyl(diethoxy)methylsilane (CAS 13501-76-3, EC 236-828-6). The observations in this study are attributed to the exposure of test organisms to the hydrolysis products in the test system. The result may be expressed in terms of concentration of the hydrolysis product: 72-hour ErC₅₀ 321 mg/l and E_rC₁₀ 101 mg/l as 3-chloropropyl(methyl)silanediol.

Key value for chemical safety assessment

EC50 for freshwater algae:

321 mg/L

EC10 or NOEC for freshwater algae:

101 mg/L

Additional information

No data are available for toxicity of the registration substance, 3-chloropropyl(dimethoxy)methylsilane (CAS 18171-19-2, EC 242-056-0), to algae. However, data are available from the related substance 3-chloropropyl(diethoxy)methylsilane (CAS 13501-76-3). Both substances have the same silanol hydrolysis product, 3-chloropropyl(methyl)silanediol. The other hydrolysis products are methanol and ethanol, respectively. In the test with 3-chloropropyl(diethoxy)methylsilane (CAS 13501-76-3), the observations are attributed to the exposure of test organisms to 3-chloropropyl(methyl)silanediol in the test system. There is no basis to expect that ethanol significantly influenced the results of the tests. The toxicity of ethanol is discussed further in the RAAF report for ecotoxicity attached in Annex 4 of the CSR and Section 13 of IUCLID.

A 72-hour E_rC₅₀ value of 437 mg/l, E_rC₁₀ value of 137 mg/l and NOEC value of approximately 57 mg/l have been determined for the effects of 3-chloropropyl(diethoxy)methylsilane (CAS 13501-76-3) on growth rate of Desmodesmus subspicatus. The results have been reported in terms of nominal concentrations of parent substance. Due to the hydrolysis rate of the test substance (9.5 hours at pH 7) and test media preparation methods (stirring for 18 hours prior to addition of test organisms), it is very likely that the test organisms were exposed to the hydrolysis products 3-chloropropyl(methyl)silanediol and ethanol. The results may be expressed in terms of concentration of the hydrolysis product, 3-chloropropyl(methyl)silanediol, by applying a molecular weight correction: (MW of silanol = 154.67 / MW of parent = 210.78) * [CONCENTRATION OF PARENT = EC₅₀ 437 mg/l and EC₁₀ 137 mg/l] = E_rC₅₀ 321 mg/l and E_rC₁₀ 101 mg/l.