Reaction products of [3-(2,3-epoxypropoxy)propyl]trimethoxysilane and triacetoxyvinylsilane.

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:

December 10, 1999 to January 31, 2001

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

yes

Remarks:

adjustment of pH

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0, 32, 56, 100, 178 and 317 mg/L.
- Sampling method: At 0 hours duplicate samples were taken directly from their preparation vessels (one vessel per level, prior to algal inoculation). Aliquots of the control and test mixtures were drawn with 50 mL glass volumetric pipettes. Sample aliquots were taken directly from test chambers at 96-h. The 50 ml aliquots were transferred from the pipettes in 50 mL polypropylene centrifuge tubes with screw-on lids. Samples were analysed for silicon using ICP-OES.
- Sample storage conditions before analysis: Not reported.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Stock solutions were prepared by weighing each respective dose of test article into a sterile glass cap. Each glass cap was added into its respective sterile 1 l beaker containing ~ 950 mL of sterile Algal Assay Medium (AAM) test medium. An empty sterile glass cap was added to the control stock solution. A sterile stir bar was added to each beaker and the beaker was covered with aluminium foil. After the test article (or empty glass cap for the control) was added, each stock solution was stirred for ~ 2 mins using a magnetic stirrer and stir bar, then placed in the environmental incubator for ~ 4 hours to allow the hydrolysis reaction to occur. After 4 hours the pH was adjusted to a value approximately equal to the controls using a measured volume of 1N NaOH. After pH adjustment, a measured volume of sterile AAM was added to each stock solution to bring the total volume up to 1 L. Four 100 mL aliquots of each stock solution were then poured into respective replicate 250 mL flasks. These solutions in the test vessels were then designated as test solutions. Algae were added into each flask (except media blanks) by transferring a specific density of algal cells from a test inoculum to achieve a 0-h concentration of approximately 10000 cells/mL. A random number generation program was used to provide the daily incubator locations.
- Controls: AAM with no test substance
- Evidence of undissolved material: None reported

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: Selenastrum capricornutum Printz
- Strain: UTEX-1648
- Source: Originally from the University of Texas at Austin, The Culture Collection of Algae, Botany Department, Austin, Texas - March 1998
- Age of inoculum: Not reported
- Method of cultivation: Not reported

ACCLIMATION
- Acclimation period:
- Culturing media and conditions (same as test or not): Culture medium was US EPA algal assay medium (AAM). Culture medium prepared from commercially available distilled water that is analysed annually for contaminants. None were shown to be present which might adversely impact the viability of the cultures or the study.
- Any deformed or abnormal cells observed: None reported

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

Not reported

Test temperature:

23 - 24 °C

pH:

0-h 7.2-7.4
96-h 7.2-7.8

Dissolved oxygen:

Not reported

Nominal and measured concentrations:

0, 32, 56, 100, 178 and 317 mg/L nominal.
0, 33.2, 57.3, 104, 191 and 344 mg/L measured.

Details on test conditions:

TEST SYSTEM
- Test vessel: Sterile 250 ml Erlenmeyer flasks
- Type: open / closed: Covered with a sponge closure
- Material, size, headspace, fill volume: 250 mL flasks filled with 100 mL test solution or AAM
- Aeration: None
- Type of flow-through: Static
- Renewal rate of test solution (frequency/flow rate): Static
- Initial cells density: 10000 cells/mL
- Control end cells density: 1352667 cells/mL
- No. of organisms per vessel:
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Commercially available distilled water
- Total organic carbon: Not reported
- Particulate matter: Not reported
- Metals: Not reported
- Pesticides: Not reported
- Chlorine: Not reported
- Alkalinity: Not reported
- Ca/mg ratio: Not reported
- Conductivity: Not reported
- Culture medium different from test medium: Culture medium US EPA AAM. Culture medium prepared from commercially available distilled water.
- Intervals of water quality measurement: 0 and 96 h

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: Yes
- Photoperiod: 24-h light, 0-h dark
- Light intensity and quality: GE Cool White and GE "E" type fluorescent lights, 368-469 foot-candles.

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter] Cell counts determined using a coulter counter Z1 particle counter. Cell counts determined at 0, 24, 48, 72 and 96 h
- Chlorophyll measurement: No
- Other:

TEST CONCENTRATIONS
- Spacing factor for test concentrations: ~ 1.78

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

104 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: hydrolysis products according to study author

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

193 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: hydrolysis products according to study author

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

275 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: hydrolysis products according to study author

Basis for effect:

growth rate

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

104 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: hydrolysis products according to study author

Basis for effect:

cell number

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

217 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: hydrolysis products according to study author

Basis for effect:

biomass

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

326 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: hydrolysis products according to study author

Basis for effect:

growth rate

Reported statistics and error estimates:

Area under the growth curve for cell populations or biomass - percent inhibition values were regressed against concentration by linear regression using Microsoft Excel for Windows 95, version 7.0a.
NOEC and ErC50 values were determined using SAS v. 6.12 (10)

Table 1: Test Substance Concentrations (mg/l) Measured During Daphnia Study

Loading Level (mg/l)	Time = 0 hrs  (duplicate samples, single vessel)		Time = 96 hrs (single samples, triplicate)
	Sample 1	Sample 2	Sample 1	Sample 2	Sample 3
32	33	33	33	33	33
56	57	57	58	58	58
100	102	102	106	105	107
178	190	191	191	192	190
316	345	347	341	342	344

Table 2: Daily Algal Cell Populations (cells/ml)

Concentration mg/l	Cell count 0-h	Cell count 24-h	Cell count 48-h	Cell count 72-h	Cell count 96-h
0	11789	36567	118522	482778	1352667
33.2	12134	35344	134111	604667	1648000
57.3	12766	28811	106756	488222	1410889
104	13989	23734	82823	397778	1273778
191	11900	21923	64256	244555	972222
344	13467	17822	19611	36889	154000

Table 3: Algal Population Inhibition at 72-h and 96-h

Concentrations mg/l	% Inhibition 72-h	% Inhibition 96-h
0	0	0
33.2	-20	-22
57.5	5	-1
104	26	14
191	51	39
344	94	92

*Negative values indicate growth rate greater than the control

Validity criteria fulfilled:

yes

Conclusions:

A 72-h EC50 of 275 mg/L has been determined for the effects of the tested substance (CAS 154518-41-9) on growth rate of Selenastrum capricornutum (new name: Pseudokirchnerella subcapitata). In the same test a 72-h and 96-h NOEC of 104 mg/L has been determined for effects on cell number. It is likely that the test organisms will have been exposed to a mixture of the parent substance and its hydrolysis products.

Description of key information

Toxicity to aquatic algae: 72 hour E_rC₅₀ 275 mg/L (measured arithmetic mean) (OECD Guideline 201 (Alga, Growth Inhibition Test)). It is not feasible to reinterpret this test result in terms of the silanol hydrolysis products.

Additional information

A 72-h ErC₅₀ value of 275 mg/L (measured (based on total silicon), arithmetic mean) has been determined for the effects of Reaction Products of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and triacetoxy(vinyl)silane (CAS 154518-41-9) on growth rate of Pseudokirchneriella subcapitata. A NOEC of 104 mg/L has been determined for effects on cell number. 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. It is not feasible to reinterpret this test result in terms of the silanol hydrolysis products.

The constituents of the registration substance hydrolyse rapidly (half-life <12 hours at pH 7 and 25°C) to [3-(2,3-epoxypropoxy)propyl]silanetriol, vinylsilanetriol, acetic acid/acetates and methanol.