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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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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 approximately 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 continuous 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
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
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
40 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
(but exposure is to hydrolysis products)
Basis for effect:
other: growth rate and biomass
Remarks on result:
other: 95%CL
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
863 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: 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 at 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 72h 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 done by single-factor ANOVA followed by Dunnett's procedure for comparing each concentration mean with the control mean.

 Table 1. Responses obtained with Dynaslylan AMEO / 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. It is likely that the test organisms were exposed to the hydrolysis products of the substance.
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:
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.:
> 1 000 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.:
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)             
Concentration (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)            

Concentration (mg/L) 

Test Interval (h)         

0 h 

 24 h

 48 h

 72 h

Control

23 

97 

1.3

2

23 

89 

2.5

2

18

85 

5.1

2

19 

87 

10.1

2

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 concentrations are with respect to the material.)


 Method    Control  33 mg/L  67 mg/L  133 mg/L  278 mg/L  556 mg/L  1000 mg/L
 Area Under Growth Curve    Area  94.5  81  83.5  78.5  61  40.5  41
% inhibition  14.3 11.6 16.9 35.4  57.1 56.6 
 Growth Rate µ (0 -72 h) µ 1.351   1.323  1.339  1.32  1.238  1.08  1.073
% inhibition    2.1  0.9  2.3  8.4  20.1  20.6
 pH Value    After 0 h  7.9  8.3  8.4  8.7  8.9  9.1  9.2
After 72 h  8.6  8.8  9.1  8.8  8.5  8.3  8.4


(b) Main Test 4
Areas under growth curves, growth rates, corresponding percentage suppression rates, and pH values with respect to test concentrations. (All concentrations are with respect to the material.)

 Method Control  1.3 mg/L  2.5 mg/L  5.1 mg/L  10.1 mg/L
 Area under growth curve  Area  72.5  67.5  59.5  52.5  63
 % inhibition    6.9  17.9  13.8  13.1
Growth rate µ (0 -72 h)   µ  1.294  1.265  1.25  1.258  1.261
   % inhibition    2.2  3.4  2.8  2.6
 pH values  After 0 h  7.5  7.8  7.8  7.9  8.1
   After 72 h  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 Desmodesmus subspicatus (previous name: Scenedesmus subspicatus). A 72-hour EC50 of 603 mg/L and NOEC of 1.3 mg/L have been determined for effects on biomass. It is likely that the test organisms were exposed to the hydrolysis products of the substance.

Description of key information

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).

72 hour ErC50: 863 mg/l and NOEC: 40 mg/l, growth rate of the marine algae 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 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

The isocyanate group is very rapidly hydrolysed to the corresponding amine (half-life <5 minutes at pH 7), and further hydrolysis of the alkoxy groups proceeds at a slower rate (half-life of 8.5 hours at pH 7 and 25°C). No data are available for the registered substance; however data are read across from 3-aminopropyl(triethoxy)silane (CAS 919-30-2), the amine which is formed very rapidly when the registered substance comes into contact with water / moisture. 

A 72 hour ErC50 value of >1000 mg/l and ErC10 of 321 mg/l (nominal concentration) have been determined for the effects of 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. 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, 1994b).

The test substance is susceptible to hydrolysis and, due to the test media preparation (stirring for 18 hours) and exposure regime (static), it is likely that the test organisms were predominantly 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 >1000 mg/l and ErC10 321 mg/l = ErC50 >620 mg/l and ErC10 199 mg/l.

Both the registration substance and the substance used as surrogate for read-across are susceptible to hydrolysis reaction of the alkoxysilane groups (to silanols) and to potential condensation reactions (described in Section 4.8). During the tests with the read-across substance, pre-hydrolysis and filtration were used as part of media preparation. Analytical recoveries by DOC were high (within 20% of nominal). Models would suggest that the irreversible condensation is unlikely for these silanol hydrolysis products at the concentrations relevant to the studies (PFA, 2016am).

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.