N-(3-(trimethoxysilyl)propyl)ethylenediamine

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:

2002-01-24 to 2002-02-01

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II) (January 2012)

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A 50 mg/L stock solution was prepared by placing 0.049 ml (density of 1.028 g/ml) of aminosilane in a 1000 mL volumetric flask and diluting to volume with sterile AAP medium containing 0.10 mL of dimethylformamide (DMF, CAS No. 68-12-2). The resulting stock solution was observed to be clear and colourless with no visible undissolved test substance. Nominal concentrations were prepared by dilution of the 50 mg/L stock solution. A solvent control was prepared with AAP medium containg 0.1 mL/L of DMF. A blank control comprising only of AAP medium was also prepared.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM

- Strain: 1648

- Source (laboratory, culture collection): The alga was obtained from Carolina Biological Supply Co., Burlington, North Carolina, and was maintained in stock culture at Springborn Smithers. 

- Culture conditions: The stock cultures were maintained within the following conditions:  a shaking rate of 100 ± 10 rpm, a temperature of 24 ± 1 °C and continuous illumination at the surface of the medium with an intensity of approximately 300 to 500 footcandles (3200 to 5400 lux).  Lighting was supplied by Duro-Test® Vita-Lite® fluorescent bulbs.  Culture flasks were agitated continuously on an orbital shaker.

- Growth/test medium:  The culture medium used was Algal Assay Procedure (AAP) medium prepared with sterile, deionized water.  

- Culture vessesl: Stock cultures were grown in 250 ml glass flasks, each containing 100 ml of culture medium. The flasks were closed with stainless steel caps that permitted gas exchange.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

No data but conductivity measured at start and end of test ranged between 75 and 90 μmhos/cm

Test temperature:

23 to 24 °C

pH:

7.2-8.7 at start of test

7.8-8.2 at end of test

Dissolved oxygen:

No data

Salinity:

No data

Nominal and measured concentrations:

Nominal test concentrations: 0 (Control), 0 (Solvent control), 1.6, 3.1, 6.3, 13, 25 and 50 mg/l

Details on test conditions:

TEST SYSTEM

- Growth/test medium:  The culture medium used was Algal Assay Procedure (AAP) medium prepared with sterile, deionized water.  

- Exposure vessel type: The test was conducted in sterile 250-ml Erlenmeyer flasks containing  100-ml of test solution.  All test vessels were fitted with stainless steel caps which permit gas exchange.  

- Culture medium:  The culture mediumused was Algal assay Procedure (AAP) medium prepared with sterile deionised water. The TOC concentration of a sample collected in January 2002 was 0.47 mg/l.

- Light levels and quality during exposure:  320 - 420 footcandles (3400 - 4500 lux).  The photosynthetically-active radiation (PAR) of the test area measured at test initiation ranged from 50 to 69 µE/m2/s.

- Test Design:  Approximately 30 minutes after the test solutions were added to the test flasks (100 ml per flask), a 0.323-ml inoculum of Pseudokirchneriella subcapitata cells, at a density of approximately 310 x 10E4 cells/ml, was aseptically introduced into each flask.  This inoculum provided the required initial (0 hour) cell density of approximately 1.0 x 104 cells/ml.  Three replicate test vessels were established for each treatment level, the dilution water control and the solvent control.

- Determination of cell concentrations: At the start of the test and at each subsequent 24 observation period, cell counts were made on each three replicates of each treatment using a hemacytometer (Neubauer improved).

- Range finding test: The test concentrations were set on the basis of the results of a range finding test conducted at concentyrations of 0.00095, 0.0095, 0.095 and 0.95 mg/l and a second test conducted at concentrations of 60, 130, 240, 480 and 960 mg/l. No effects were observed in the first test and effects at all treatment levels were observed in the second test.

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

3.1 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.:

8.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

growth rate

Remarks on result:

other: 2.3-34 mg/L

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

5.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

biomass

Remarks on result:

other: 1.8-17

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

biomass

Remarks on result:

other: determined empiracally as the highest concentration with <10% inhibition

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

11 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

other: cell density

Remarks on result:

other: 2.2-61 mg/L

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

6.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

other: cell density

Details on results:

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

- Control cell density at end of test: 1580000 cells/ml (Control), 1360000 cells/ml (Solvent control), 1470000 cells/ml (Pooled control)

Reported statistics and error estimates:

The EC50 values were determined by linear regression using the method of inverse regression.

The NOECs were determined by either Williams' test (if the data sets passed the test homogeneity and normality) or the Kruskal-Wallis'test if they did not. If the statistical analyses did not yield a reasonable NOEC it was selected empiracally as the highest treatment level that resulted in <10% inhibition.

All statistical determinations were made at 95% level of certainty.

Table 1. Test results

Nominal concentration (mg/l)	Mean cell concentration after 24 hours (cells/ml)	Mean cell concentration after 48 hours (cells/ml)	Mean cell concentration after 72 hours (cells/ml)	Mean cell concentration after 96 hours (cells/ml)	Percentage reduction in cell concentration at end of the test*	Percentage reduction in biomass at end of the test*	Percentage reduction in 0 -72 -hour growth rate*
0 (Control)	24200	75000	435000	1580000	-	-	-
0 (Solvent control)	21700	75000	408000	1360000	-	-	-
0 (Pooled control)	20000	80000	420000	1470000	-	-	-
1.6	17500	75800	390000	1420000	3	7.0	2.0
3.1	10800	52500	413000	1590000	-8	14	1.0
6.3	7500	35800	256000	1220000	17	48	15**
13	800	10000	87000	860000	41**	89	44**
25	800	800	3000	10000	99**	108**	128**
50	800	5000	3000	0	100**	106	128**

*A negative sign (-) indicates that biomass or growth rate was higher than in the Control.

** Significantly different compared with pooled control

Validity criteria fulfilled:

yes

Conclusions:

A 96-hour EC50 value of 8.8 mg/l and NOEC of 3.1 mg/l have been determined for the effects of the test substance on growth rate of Pseudokirchnerella subcapitata. The results are expressed relative to nominal concentrations of the test substance. However the substance is subject to rapid hydrolysis and under the test conditions it is therefore likely that exposure will have been to its hydrolysis products (methanol and N-(3-(trihydroxysilyl)propyl)ethylenediamine).

Description of key information

72-hour E_rC₅₀ 8.8 mg/l and NOE_rC 3.1 mg/l (nominal) (OECD 201), Pseudokirchneriella subcapitata. The E_rC₅₀ and NOE_rC values are equivalent to 7.1 mg/l and 2.5 mg/l respectively, when expressed in terms of the silanol hydrolysis product, N-(3-(trihydroxysilyl)propyl)ethylenediamine.

Key value for chemical safety assessment

EC50 for freshwater algae:

7.1 mg/L

EC10 or NOEC for freshwater algae:

2.5 mg/L

Additional information

72-hour E_rC₅₀ and NOE_rC values of 8.8 mg/l and 3.1 mg/l, respectively, (nominal) have been determined for the effects of the registration substance, N-(3-(trimethoxysilyl)propyl)ethylenediamine (CAS 1760-24-3, EC 217-164-6), on the growth rate of Pseudokirchneriella subcapitata (Springborn Smithers, 2002). The results are expressed relative to nominal concentrations of the test substance. The test was conducted according to OECD TG 201 and in compliance with GLP. 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 (methanol and N-(3-(trihydroxysilyl)propyl)ethylenediamine).

The results may be expressed in terms of concentration of the silanol hydrolysis product, N-(3-(trihydroxysilyl)propyl)ethylenediamine, by applying a molecular weight correction: (MW of silanol = 180.28 / MW of parent = 222.36) * 8.8 and 3.1 = 7.1 mg/l and 2.5 mg/l.

A solvent was used to prepare the test solution, however the solvent control was not statistically significantly different to the negative control and the results of the study are considered valid.

This result has been selected as the lowest E_rC₅₀ value for effects on growth rate from four studies. The other reliable E_rC₅₀ value is 126 mg/l and the corresponding NOE_rC is 20 mg/l.

Another report to which it is not possible to assign a reliability score determined EC₅₀ values in the range of 31 to 175 ppm and corresponding NOEC value of <1 to <125 ppm.

The study with lowest reliable E_rC₅₀ and NOE_rC values has been selected as key study as a worst case scenario.