3-(trimethoxysilyl)propyl isocyanate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1993-08-10 to 1993-12-17

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

Cited as Directive 92/69/EEC, C.3

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

The TOC concentration of the filtered stock solutions used to prepare the test media were determined and used as the basis for calculating the test concentrations that were prepared by dilution of the stock solutions.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: The test substance was added to dilution water and stirred for 18 hours. After mixing it was filtered and used to prepare the other test media by dilution.

The TOC content was determined in the filtered initial solutions.  The TOC content (mg/l) and the substance content (mg/l) in the hydrous, filtered initial solution in Main Test 2 were reported to be 543 mg/l and 1111 mg/l, respectively. The concentrations used in Main Test 2 were calculated from TOC content and included 33, 67, 133, 278, 556, and 1000 mg/l.  The TOC content (mg/l) and the substance content (mg/l) in the hydrous, filtered initial solution in Main Test 4 were reported to be 309 mg/l and 632 mg/l, respectively.  The concentrations used in Main Test 4 were calculated from TOC content and included 1.3, 2.5, 5.1, and 10.1 mg/l.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM

- Strain: 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.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

No data

Test temperature:

24+/-2ºC

pH:

7.9-9.2 in Test 2

7.5-9.0 in Test 4

Dissolved oxygen:

Not applicable

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations in mg/l in Main test 2: 0, 33, 67, 133, 278, 556, and 1000 mg/l.  

Nominal concentrations in mg/l in Main test 4: 1.3, 2.5, 5.1, and 10.1.

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:1150000 cells/ml (Test 2), 970000 cells/ml (Test 4)

- 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 after 24, 48 and 72 hours by spectrophotometer (absorption at 685 nm)


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.8-2.0

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

321 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: growth rate and biomass

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

603 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

other

Reported statistics and error estimates:

ECx values were determined by probit analysis.

NOEC values were determined by comparing Control and treatment means using a Student's t-test.

Table 1. Biological observations (Cell density at each flask at each measuring point)

(a) Main Test 2
                        Cell count (*104 cells/ml)
Conc.(mg/l)             Test interval (h)
                        0 h     24 h    48 h    72 h
Control                 2       7       35      115
33                      2       6       27      106
67                      2       6       27      111
133                     2       6       25      105
278                     2       5       20      82
556                     2       5       15      51
1000                    2       5       16      50

*No median values.  All concentrations are with respect to
the material.  Five each and eight each parallels,
respectively, were examined.  (After 0 h, the theoretical
cell concentration was evaluated).

(b) Main Test 4
                        Cell count (*104 cells/ml)
Conc.(mg/l)             Test interval (h)
                        0 h     24 h    48 h    72 h
Control                 2       6       23      97
1.3                     2       5       23      89
2.5                     2       4       18      85
5.1                     2       5       19      87
10.1                    2       5       19      88

*No median values. All concentrations are with respect to
the material.

Growth curves: The EC values are calculated by regression
analysis based on [Probit] transformation of the percentage
suppression values.  These values then serve as the basis
for the subsequent [Probit] analysis in accordance with
Cavalli-Sforza (1972).  The results are presented below.

Effective Concentrations on the Basis of Cell Growth (EbC)
Parameter       mg/L (substance)
(72 h) EbC50    603
(72 h) EbC10    38
(72 h) EbC90    *
* lies above the highest tested concentration
 

Effective Concentrations on the Basis of Specific Growth
Rate µ(ErC)
Parameter       mg/L (substance)
(72 h) ErC50    *
(72 h) ErC10    321
(72 h) ErC90    *
* lies above the highest tested concentration

Table 2. Percent biomass/growth rate inhibition per concentration

(a) Main Test 2

Areas under growth curves, growth rates, corresponding percentage suppression rates and pH values with respect to test concentrations (all concentration are with respect to the material).

                                       (mg/l)
Method             Control   33    67  133  278  556  1000

Area Under  Area   94.5    81   83.5 78.5 61   40.5  41
Growth     % suppr.       14.3  11.6 16.9 35.4 57.1 56.6
Curve        
                                                        
Growth      µ     1.351  1.323 1.339 1.32 1.238 1.08 1.073
Rate µ    % suppr.        2.1   0.9   2.3  8.4  20.1  20.6
(0-72h)

pH      After 0 h  7.9    8.3   8.4   8.7  8.9   9.1  9.2
values  After 72 h 8.6    8.8   9.1   8.8  8.5   8.3  8.4


(b) Main Test 4

Areas under curves, growth rates, corresponding percentage suppression rates and pH values with respect to test concentrations (all concentrations are with respect to the material).

                                     (mg/l)
Method            Control   1.3      2.5     5.1    10.1

Area Undern Area  72.5    67.5    59.5    52.5     63
Growth    % suppr.         6.9    17.9    13.8    13.1
Curve

Growth      µ    1.294   1.265    1.25    1.258   1.261
Rate µ    % suppr.        2.2      3.4     2.8     2.6
(0-72 h)

pH     After 0 h   7.5    7.8      7.8     7.9     8.1
values After 72h   9.0    8.8      8.7     8.7     8.6

Validity criteria fulfilled:

yes

Conclusions:

A 72-hour EC50 value of >1000 mg/L and a NOEC of 1.3 mg/L have been determined for the effects of the test substance on growth rate of Scenedesmus subspicatus. A 72-hour EC50 of 603 mg/L and NOEC of 1.3 mg/L have been determined for effects on biomass. The test substance is susceptible to hydrolysis and it is therefore likely that the test organisms were exposed to the hydrolysis products of the substance.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2005-04-28 to 2005-05-06

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

ISO 10253 (Water quality - Marine Algal Growth Inhibition Test with Skeletonema costatum and Phaeodactylum tricornutum)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

Test solutions were prepared individually by stirring appropriate amounts of the test substance in app. 500 ml of seawater. the solutions were stirred with a spin-bar for 20 hours at a speed which formed a vortex two-thirds of the depth of the fluid content, followed by standstill for 4 hours. Samples for testing were taken from the mid of the water phase with a peristaltic pump.

Test organisms (species):

Skeletonema costatum

Details on test organisms:

TEST ORGANISM

- Strain: NIVA-BAC 1
- Source (laboratory, culture collection): originally isolated from the Oslo fiord (1962), Norsk Institute for Vannforskning (NIVA), Oslo
- Age of inoculum (at test initiation): 3 days, the cell density of the inoculum was 1.6 million cells/ml determined by microscopic counting using a Palmer-Malony counting slide.
- Method of cultivation: The pre-cultures used in this test was incubated at 20±2°C under conditions light (>50µE x m² x secE-1) from fluorescent tubes of universal natural white type on an orbital shaker.

Test type:

static

Water media type:

saltwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

no

Hardness:

no data

Test temperature:

19.0 - 20.0C

pH:

at start: 8.2 (control) - 9.7 (1549 mg/l test substance)
at end: 8.3 (control) - 8.7 (1549 mg/l test substance

Dissolved oxygen:

not applicable

Salinity:

the used natural seawater has a salinity of 34.5%

Nominal and measured concentrations:

nominal: 6.9; 16.3; 40; 100; 308; 623; 1549 mg/l

Details on test conditions:

TEST SYSTEM

- Test vessel: 50 ml test culture in 100 ml flat-bottomed flasks on an orbital shaker

- Initial cells density: 1.6 million cells/ml

- Control end cells density: more than a factor (growth rate: 0.9 per day)

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

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


GROWTH MEDIUM

- Source: Natural seawater from unpolluted site was collected from a tap, after filtration through sand filter. The seawater was filtered through a GF/C filter, and briefly heated to about 75°C prior to use. The seawater was enriched with nutrient according to ISO 10253, and recommendations from the Paris Commission.


OTHER TEST CONDITIONS

- Adjustment of pH: no

- Photoperiod: continuous light

- Light intensity and quality: (> 50µE/m²sec) from fluorescent tubes of universal natural white type

- Salinity (for marine algae): 34%


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :

- Determination of cell concentrations: by fluorescence on a Turner Designs, Model 10 fluorimeter

- Other:


TEST CONCENTRATIONS

- Test concentrations: 6.9; 16.3; 40; 100; 308; 623; 1549 mg/l

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol 97%, CAS: 591-35-5

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

40 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: growth rate and biomass

Remarks on result:

other: 95%CL

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

863 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95%CL

Details on results:

One of the test concentrations (100 mg/L) was excluded from further calculations because after the solution was prepared there was an unusual precipitation in this concentration. All the other concentrations were clear.

Results with reference substance (positive control):

- Results with reference substance valid? yes

- EC50: 35%

The EC50 result of the 72-hour test with 1.5 mg/L 3.5-dichlorophenol should be within 20-80%.

Reported statistics and error estimates:

In the current study the responses were such that insufficient data are available for statistic evaluation of the response concentration using the computer program TOXEDO and the EL50 value was estimated by interpolation.

Calculation of NOELR was performed by a single-factor ANOVA followed by Dunnet's procedure for comparing each concentration mean with the control mean.

 Table 1. Responses obtained with Experimental data

Concentration in mg / l	Growth rate	Inhibition in percent
control 1	1.87	-
control 2	1.85	-
control 3	1.94	-
control 4	1.89	-
control 5	1.91	-
control 6	1.94	-
control mean	1.90	0
6.90	2.00	0.0
6.90	2.00	0.0
6.90	1.96	0.0
16.30	1.71	10.0
16.30	1.78	6.3
16.30	1.84	3.2
40.00	1.78	6.3
40.00	1.90	0.0
40.00	1.77	6.8
100.00	0.64	66.3
100.00	0.87	54.2
100.00	0.88	53.7
308.00	1.21	36.3
308.00	1.40	26.3
308.00	1.54	18.9
623.00	1.25	34.2
623.00	1.52	20.0
623.00	1.67	12.1
1549.00	0.00	100.00
1549.00	0.00	100.00
1549.00	0.00	100.00

 

Validity criteria fulfilled:

yes

Conclusions:

A 72-hour EC50 value of 863 mg/L and a NOEC of 40 mg/L have been determined for the effect of the test substance on growth rate of Skeletonema costatum. The test substance is susceptible to hydrolysis and it is therefore likely that the test organisms were exposed to the hydrolysis products of the substance.

Description of key information

WoE 72-hour ErC₅₀: >1000 mg/L and ErC₁₀: 321 mg/L, growth rate of Scenedesmus subspicatus; equivalent to ErC₅₀: >620 mg/L and ErC₁₀: 199 mg/L as 3-aminopropylsilanetriol, read-across from 3-aminopropyl(triethoxy)silane (CAS 919-30-2).

WoE 72-hour ErC₅₀: 863 mg/L and NOEC: 40 mg/L, growth rate of Skeletonema costatum; equivalent to ErC₅₀: 535 mg/L and NOEC: 25 mg/L as 3-aminopropylsilanetriol, read-across from 3-aminopropyl(triethoxy)silane (CAS 919-30-2).

Key value for chemical safety assessment

EC50 for freshwater algae:

620 mg/L

EC50 for marine water algae:

535 mg/L

EC10 or NOEC for freshwater algae:

199 mg/L

EC10 or NOEC for marine water algae:

25 mg/L

Additional information

No reliable algal toxicity data are available with 3-(trimethoxysilyl)propyl isocyanate (CAS 15396-00-6), therefore good quality data from an appropriate structural analogue, 3-aminopropyl(triethoxy)silane (CAS 919-30-2), have been read across.

A 72-hour ErC₅₀ value of >1000 mg/L and ErC₁₀ of 321 mg/L have been determined for the effects of the read-across substance 3-aminopropyl(triethoxy)silane (CAS 919-30-2) on growth rate of the freshwater algae Scenedesmus subspicatus, in accordance with EU Test method C.3. A 72-hour EbC₅₀ of 603 mg/L and EbC₁₀ of 38 mg/L have been determined for effects on biomass. The NOEC in the study was 1.3 mg/L (for effects on growth rate and/or biomass; no growth rate-specific NOEC is derived) (derived in an extension to the above study and under consistent conditions) (Hüls, 1993).

The results may be expressed in terms of concentration of the hydrolysis product, 3-aminopropylsilanetriol, by applying a molecular weight correction: (MW of silanol = 137.21 / MW of parent = 221.37) * ErC₅₀ >1000 mg/L and ErC₁₀ 321 mg/L = ErC₅₀ >620 mg/L and ErC₁₀ 199 mg/L. These values are read across to 3-(trimethoxysilyl)propyl isocyanate (CAS 15396-00-6) without further correction.

 

In a separate test, a 72-hour ErC₅₀ value of 863 mg/L and NOEC of 40 mg/L have also been determined for the effect of the read-across substance 3-aminopropyl(triethoxy)silane (CAS 919-30-2) on growth rate of the marine algae Skeletonema costatum, in accordance with test guideline ISO 10253 (M-Lab, 2005). It is likely that the test organisms were exposed to the hydrolysis products of the substance.

The results may be expressed in terms of concentration of the hydrolysis product, 3-aminopropylsilanetriol, by applying a molecular weight correction: (MW of silanol = 137.21 / MW of parent = 221.37) * ErC₅₀ 863 mg/L and NOEC for growth rate 40 mg/L = ErC₅₀ 535 mg/L and NOEC 25 mg/L. These values are read across to 3-(trimethoxysilyl)propyl isocyanate (CAS 15396-00-6) without further correction.

The NOEC in the test with Scenedesmus subspicatus  is not representative of the inhibition of growth rate, as the EC₁₀ values for growth rate and biomass make clear. It is not appropriate to derive PNEC based on biomass effects in the absence of effects on growth rate. Excluding this result, the NOEC in the Skeletonema costatum  study (25 mg/L of 3-aminopropylsilanetriol) is the most appropriate starting value for the derivation of PNEC.

Condensation reactions leading to insoluble oligomers/polymers can be a problem for ecotoxicity testing with substances generating silanols. This has been considered for this substance and is not considered to have been an issue at the test media stock concentration in the key studies (PFA, 2016am).

 

Refer to the IUCLID Section 6 endpoint summary (Section 7.0 of the CSR) for further discussion of the approach to chemical safety assessment for this registration substance, and justification for read-across used.