acrylic acid, 3-(trimethoxysilyl)propyl ester

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:

20 March - 24 March 1995

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

pH deviated in one test concentration beyond 1.5 units outlined in OECD TG 201. ErC50 was only determined for 24h, not 72h as recommended by the guideline.

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

Previous version (1984)

Deviations:

yes

Remarks:

Test duration was 96 hours however exponential growth rate was maintained. pH deviated beyond 1.5 units in one test concentration. These deviations are not expected to impact the results of the study

Qualifier:

according to guideline

Guideline:

EPA OTS 797.1050 (Algal Toxicity, Tiers I and II)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: control and each test concentration (replicates were pooled) at 0 h and 96 h
- Sampling method: Water samples were taken (no details reported)
- Sample storage conditions before analysis: not reported

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Test material (1000 mg) was dissolved in culture medium with the aid of ultrasonic disruption and shaking by hand. The volume was adjusted to 2 L to give a stock solution of 500 mg/l. Serial dilutions were made from this stock solution to make stock solutions for each test concentrations. Aliquots of these solutions were added to algal suspensions to give the test concentrations.
- Eluate: Not reported
- Differential loading: no
- Controls: test media
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): none reported
- Other relevant information:

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: green algae
- Strain: CCAP 278/4
- Source (laboratory, culture collection): Culture Centre for Algae and Protozoa, Institute of Freshwater Ecology, Ferry House, Ambleside, Cumbria.
- Age of inoculum (at test initiation):
- Method of cultivation: transfer of algal cells to fresh culture medium, weekly.

ACCLIMATION
- Acclimation period: not reported
- Culturing media and conditions (same as test or not): yes
- Any deformed or abnormal cells observed: none reported

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Post exposure observation period:

A regrowth period of 9 days was observed in subcultures from the control and the 250 mg/l test concentration. Regrowth occurred in the control subculture, but no regrowth occurred in the test subculture.

Hardness:

Not reported

Test temperature:

Maintained at 24+/- 1 degrees C with the exception of three measurements (approx. 21.5, 22.0 and 22.5 degrees C).

pH:

8.0 - 11.3. See Results for details of pH values at 0 and 96h. Control vessels did not deviate in pH by more than 1.5 units.

Dissolved oxygen:

Not reported

Salinity:

Not reported

Conductivity:

Not reported

Nominal and measured concentrations:

Nominal: control, 15.625, 31.25, 62.5, 125, 250 mg/l
Measured: control, 10.4, 22.5, 57.7, 114 and 217 mg/l (at 0 h). All test concentrations

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 ml conical glass flasks, ground glass stoppers
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: glass, 250 ml fill volume
- Aeration: constantly shaken at 100 rpm for 96 hours
- Initial cells density: 10E+4 cells/ml
- Control end cells density: See results section
- No. of organisms per vessel: not reported
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes - OECD standard medium

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: not reported
- Culture medium different from test medium: no
- Intervals of water quality measurement: pH was measured at 0 h and 96 h, continuous temperature recording

OTHER TEST CONDITIONS
- Sterile test conditions: no
- Adjustment of pH: not reported
- Photoperiod: 24 hours light
- Light intensity and quality: approximately 7000 lux


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: counting chamber (haemocytometer)
- Chlorophyll measurement: not measured
- Other:

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Justification for using less concentrations than requested by guideline: not applicable
- Range finding study
- Test concentrations: First range finder: 0.10, 1.0, 10 and 100 mg/l. Second range finder: 62.5, 125, 250, 500 mg/l
- Results used to determine the conditions for the definitive study: No inhibition of growth in 0.10, 1.0 and 10 mg/l and 26% inhibition (based on biomass) at 100 mg/l. The second range finder did not report inhibition values, however cell densities did decrease (1.16E+5 in 500 mg/l compared to 1.22E+6 in the control).

Reference substance (positive control):

not specified

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 125 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: As calculated by reviewer

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 31.25 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: As calculated by reviewer

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

105 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

70 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

87 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

31.25 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): abnormalities in the highest treatment level, see below.
- Unusual cell shape: no abnormalities in the first four treatments but in the 250 mg/l treatment, cells were observed to be small in size and distorted in shape
- Colour differences: none reported
- Flocculation: none reported
- Adherence to test vessels: none reported
- Aggregation of algal cells: none reported
- Other:
- Any stimulation of growth found in any treatment: yes, slight increase in 15.625 mg/l test concentration
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: none reported
- Effect concentrations exceeding solubility of substance in test medium: not reported

Reported statistics and error estimates:

EC50 values were fitted by eye onto growth/biomass curves. A one way Anova was used to determine the 96-hour NOEC

Table 1. Mean algal cell densities at 24 hour intervals during the definitive test

Nominal concentration (mg/l)	Mean cell densities (cells/ml)
	0h	24h	48h	72h	96h
Control	2.47E+04	1.08E+05	3.61E+05	9.03E+05	3.22E+06
15.625	2.16E+04	1.08E+05	3.43E+05	9.58E+05	3.51E+06
31.25	2.78E+04	9.88E+04	3.73E+05	9.17E+05	3.03E+06
62.5	3.39E+04	8.94E+04	2.44E+05	4.29E+05	8.68E+06
125	3.08E+04	6.48E+04	1.64E+05	3.18E+05	4.54E+05
250	3.08E+04	3.70E+04	6.18E+04	1.20E+05	1.61E+05

Table 2. Inhibition of algal growth in the definitive test

Nominal concentration (mg/l)	Growth rate (0-24h)	% Inhibition	Area under the curve (72h)	% Inhibition	Area under the curve (96h)	% Inhibition
Control	0.061	-	2.06 x10^7	-	6.95 x10^7	-
15.625	0.067	-10*	2.10 x10^7	-2*	7.42 x10^7	-7*
31.25	0.053	13	2.07 x10^7	0	6.74 x10^7	3
62.5	0.040	34	1.11 x10^7	46	2.59 x10^7	63
125	0.031	49	7.45 x10^6	64	1.60 x10^7	77
250	0.008	87	1.97 x10^6	90	4.60 x10^6	93

* values show increase of growth in comparison to the control group.

Table 3. Inhibition of growth rate after 72 hours (as calculated by reviewer)

Nominal concentration mg/l	Cell density		72 hour average specific growth rate	% Inhibition of growth rate
	0 h	72 h
Control	24700	903000	1.20	N/a
15.625	21600	958000	1.26	-5.4
31.25	27800	917000	1.17	2.9
62.5	33900	429000	0.85	29.5
125	30800	318000	0.78	35.1
250	30800	120000	0.45	62.2

Table 4. pH values at 0h and 96h

Nominal concentration (mg/l)	Replicate number	pH 0h	pH 96h
Control	1	8.0	9.4
	2	8.0	9.4
	3	8.0	9.4
15.625	1	8.0	11.3
	2	8.0	10.6
	3	8.0	10.7
31.25	1	8.0	9.4
	2	8.0	9.0
	3	8.0	9.2
62.5	1	8.0	8.7
	2	8.0	8.7
	3	8.0	8.7
125	1	8.0	8.3
	2	8.0	8.5
	3	8.0	8.8
250	1	8.0	8.2
	2	8.0	8.4
	3	8.0	8.4

Table 5. Verification of test concentrations

Samples	Nominal concentration (mg/l)	Measured concentration (mg/l)	% of nominal concentrations
0 hours	Control	<LOD	-
	15.625	10.4	67
	31.25	22.5	72
	62.5	57.7	92
	125	114	91
	250	217	87
96 hours	Control	<LOD	-
	15.625	<LOD	-
	31.25	<LOD	-
	62.5	<LOD	-
	125	<LOD	-
	250	<LOD	-

Validity criteria fulfilled:

not specified

Remarks:

Mean coefficient of variation was not reported. However, the biomass increased by a factor of more than 16 over 72 hours (OECD guideline, actual value 37) and by over a factor of 100 over 96 hours (US EPA guidelines, actual value 130)

Conclusions:

A 24-hour ErC50 value of 105 mg/l was reported for the effects of 3-(trimethoxysilyl)propyl acrylate on the growth rate of Pseudokirchneriella subcapitata (reported as Selenastrum capricornutum), based on nominal concentrations. Individual replicate growth rates and biomass values were not reported, therefore a 72-hour ErC50 value based on growth rate could not be calculated. However, based on the mean inhibition of growth rate values at 72-hours, the 72-hour ErC50 and ErC10 values have been estimated by the study reviewer as >125 mg/l and >31.25 mg/l respectively, based on nominal concentrations. These values are supported by a 72-hour EbC50 value of 70 mg/l and a 96-hour NOEbC value of 31.25 mg/l, based on biomass.

Because the growth rate and biomass values have not been reported for individual replicates, the coefficient of variation (COV) for each 24 hour stage and total COV could not be determined. Therefore, two validity criteria in OECD TG 201 could not be assessed. However, the study methodology is documented sufficiently and the biomass increased by more than a factor of 16 over 72 hours, so the study is considered reliable for the purposes of assessing the toxicity to aquatic algae endpoint.

Description of key information

24-hour E_rC₅₀ 107 mg/l, based on the growth rate of Pseudokirchneriella subcapitata (reported as: Selenastrum capricornutum), based on nominal concentrations. 72-hour E_rC₅₀ and E_rC₁₀ values of >125 mg/l and >31.25 mg/l respectively, were calculated by the study reviewer based on the mean growth rate inhibition values and nominal concentrations. The 24-hour E_rC₅₀, 72-hour E_rC₅₀ and E_rC₁₀ values are equivalent to 86 mg/l, >103 mg/l and >26 mg/l, respectively, when expressed in terms of concentration of the silanol hydrolysis product, 3-acryloxypropylsilanetriol.

Key value for chemical safety assessment

EC50 for freshwater algae:

86 mg/L

Additional information

A 24-hour E_rC₅₀ value of 105 mg/l, was determined in a reliable test conducted under static conditions with the registration substance, 3-(trimethoxysilyl)propyl acrylate (CAS 4369-14-6, EC 419-560-6), according to OECD Test Guideline 201. 72-hour E_rC₅₀ and E_rC₁₀ values of >125 mg/l and >31.25 mg/l respectively, were calculated by the study reviewer based on mean growth rate values. These values are supported by a 72-hour E_bC₅₀ value of 70 mg/l and a 96-hour NOE_bC value of 31.25 mg/l, based on biomass. Gas chromatography analysis determined concentrations of the parent test substance were within 80-120% of nominal values at 0 hours, however no parent was detected in test solutions after 96-hours. The results are expressed in terms of the nominal concentrations of the test substance.

Because the growth rate and biomass values have not been reported for individual replicates, the coefficient of variation (COV) for each 24 hour stage and total COV could not be determined. Therefore, two validity criteria in OECD TG 201 could not be assessed. However, the study methodology is documented sufficiently and the biomass increased by more than a factor of 16 over 72 hours, so the study is considered reliable for the purposes of assessing the toxicity to aquatic algae endpoint.

The test substance is subject to rapid hydrolysis and under the test conditions it is therefore likely that exposure will have been to its hydrolysis products (3-acryloxypropylsilanetriol and methanol).

The results may be expressed in terms of concentration of the silanol hydrolysis product, 3-acryloxypropylsilanetriol, by applying a molecular weight correction: (MW of silanol = 192.25 / MW of parent = 234.33) * [Concentration of parent = 105, >125 and >31.25 mg/l] = 86, >103 and >26 mg/l, respectively.

There is no basis to expect that methanol significantly influences the results of the test. The toxicity of methanol is discussed further in Section 6.1 Aquatic Toxicity endpoint summary of IUCLID.