Bis(trimethoxysilylpropyl)amine

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 - 23 Aug 2013

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:

2006

Qualifier:

according to guideline

Guideline:

other: Algal Growth Inhibition Test stipulated in the Testing Methods for New Chemical Substances of Japan

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: all concentrations and the control were sampled at the start and the end of exposure. Algae were removed by centrifugation (3000 rpm, 10 min) prior to sampling at the end of the exposure period.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: test item and OECD medium were mixed and stirred for 2 h. The suspension was filtered with a glass fiber filter. The theoretical concentration of methanol in the prepared stock solution was 56 mg/L. Test solutions were prepared mixing the stock solution with the appropriate amount of dilution water.

- Other: in order to ignore the additional effect of methanol on the organisms in the test solutions and to determine only the toxicity of silanol form, the definitive test condition was designed appropriately so that test solution in all exposure levels contained same methanol concentrations.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM

- Common name: green algae

- Strain: ATCC 22662

- Source (laboratory, culture collection): laboratory culture (initial source: American Type Culture Collection)

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

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

pH unadjusted: 21.8 - 22.0 °C
pH adjusted: 22.8 - 22.9 °C

pH:

pH unadjusted: 7.8 - 9.0
pH adjusted: 7.9 - 8.0

Nominal and measured concentrations:

0 (control), 0.31, 0.93, 2.8, 8.3, 25 and 75 mg/L (nominal, as silanol form, pH unadjusted)
0 (control), 0.31, 0.93, 2.8, 8.3, 25 and 75 mg/L (nominal, as silanol form, pH adjusted)

Details on test conditions:

TEST SYSTEM

- Test vessel: sterilized 500 mL Erlenmeyer flasks (with gas-permeable Silicosen)

- Fill volume: 100 mL

- Initial cells density: 0.75 x 10^4 cells/mL

- Control end cells density: 85 x 10^4 cells/mL (pH unadjusted), 110 x 10^4 cells/mL (pH adjusted)

- Methanol end cells density: 95 x 10^4 cells/mL (pH unadjusted), 100 x 10^4 cells/mL (pH adjusted)

- No. of vessels per concentration (replicates): 3

- No. of vessels per control (replicates): 3

- No. of vessels per methanol control (replicates): 6

GROWTH MEDIUM

- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: according to OECD guideline

- Intervals of water quality measurement: pH was measured at the start and at the end of the exposure period. Temperature and light intensity were measured daily.

OTHER TEST CONDITIONS

- Adjustment of pH: as the pH in the highest test concentration exceeded pH 9, a parallel was set up for all test concentration in which the pH was adjusted to the pH of the medium, in order to examine wether effects are caused by the high pH values.

- Photoperiod: continuous illumination provided by fluorescent lights with wavelength range of 400 - 700 nm

- Light intensity and quality: 83 - 85 µE*m^-2*s^-1

- Aggitation: continuous rotary shaking at approx. 100 rpm

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : cell biomass was measured every 24 h

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3

- Preliminary study: was conducted in order to follow hydrolysis of the the test item. 156 mg/L (as test item concentration) were prepared in ultra pure water. Methanol was measured after 0, 0.5, 1 and 2 hours in order to follow the state of hydrolysis. 94.3, 95.2, 98.5 and 102% of the theoretical formed concentration (87.8 mg/L) was measured after 0, 0.5, 1 and 2 h, respectively.

- Range finding study: yes, 2-3 replicates, 2 parallels were set up with and without pH adjustment, silanol form and methanol were measured with and without algae at the beginning and at the end of the exposure

- Test concentrations: 1.2, 2.6, 5.6, 12, 27 and 60 mg/L (nominal, as silanol form, pH unadjusted), 0.6, 1, 10, 60 and 100 mg/L (nominal, silanol form, pH adjusted)

- Results used to determine the conditions for the definitive study: growth inhibition based on growth rate was 0.033, 3.9, 8.1, 19, 64 and 123% for 1.2, 2.6, 5.6, 12, 27 and 60 mg silanol form/L, respectively in the experiment with no pH adjustment. 2.1, 1.2, 6, 92 and 135% growth rate inhibition was observed at 0.6, 1, 10, 60 and 100 mg/L, respectively in the preliminary experiment with pH adjustment. Based on these results concentrations between 0.31 - 75 mg/L

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

31 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: pH unadjusted, 95% CI: 26 - 36 mg/L

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

36 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: pH adjusted, 95% CI: 33-40 mg/L

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

2.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: pH unadjusted

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

8.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: pH adjusted

Details on results:

- Exponential growth in the control when pH was unadjusted: yes (109-fold increase in the control and 120-fold increase in the methanol control)

- Exponential growth in the control when pH was adjusted: yes (147-fold increase in the control and 127-fold increase in the methanol control)

Results with reference substance (positive control):

- Results with reference substance valid: yes

- EC50: 1 mg/L

Reported statistics and error estimates:

For the estimation of NOEC, Bartlett´s test was applied to determine the homogeneity of variance of the data. Then one-way analysis of variance and Dunnett´s multiple comparison test was used to determine the significant difference between the methanol control and the exposure levels.

Measured test item concentrations at the beginning and at the end of the test:

- pH unadjusted: measured silanol form concentrations at test start: 97 – 108% of nominal concentrations, silanol concentrations at test end: 96 - 108% of nominal concentrations. Measured methanol concentrations at test start: 98 – 112% of nominal concentration, methanol concentration at test end: 104 – 112% of the theoretical formed concentration.

- pH adjusted: measured silanol form concentrations at test start: 106 - 114% of nominal concentrations, measured concentrations of silanol form at test end: 98 – 120% of nominal. Measured methanol in the test solutions at the beginning of the test: 104 – 111% of the nominal concentration, methanol determined at test end: 100 – 112% of the theoretical formed concentration.

Table 1: Growth inhibition in %.

Nominal concentrations [mg/L]	pH unadjusted	pH adjusted
	Inhibition rate %	Inhibition rate %
Control	2.3	-1.1
Methanol control	-	-
0.31	0.16	0.88
0.93	1.6	-0.67
2.8	3.2	-1.2
8.3	4	1.2
25	32	23
75	129	102

Validity criteria fulfilled:

yes

Conclusions:

An EC50 (72 h) value of 31 mg/L and a NOEC of 2.8 mg/L have been determined based on the growth rate of Pseudokirchnerella subcapitata when the pH of the solution was not adjusted. An EC50 (72 h) of 36 mg/L and a NOEC (72 h) of 8.3 mg/L were determined based on the growth rate of the test organism when the pH was adjusted to the pH of the dilution water.

Description of key information

ErC50 (72 h) = 36 mg/L and NOErC (72 h) = 8.3 mg/L (nominal, OECD 201)

Key value for chemical safety assessment

EC50 for freshwater algae:

36 mg/L

EC10 or NOEC for freshwater algae:

8.3 mg/L

Additional information

One study is available according to the OECD guideline 201 testing the toxicity of bis(trimethoxysilylpropyl)amine (CAS 82985 -35 -1) towards algae (2014). Pseudokirchneriella subcapitata as the test organism was exposed to nominal test item concentrations of 0 (control), 0.31, 0.93, 2.8, 8.3, 25 and 75 mg/L for 72 h. Two parallels were tested, with and without a pH adjustment.

The tested substance was analytically monitored during the study by LC-MS and GC analysis. Due to rapid hydrolysis of the substance, the hydrolysis products were analytically followed during the test and measured in all test levels at test start and test end. The analytical recovery of the hydrolysis products was between 96 - 112% at the start and at the end of the experiment. The study resulted in an EC50 of 36 mg/L and a NOEC of 8.3 mg/L when pH was adjusted.