Registration Dossier

Data platform availability banner - registered substances factsheets

Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Currently viewing:

Administrative data

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:
2007-04-16 to 2007-05-10
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Guideline study. This was a GLP compliant study with measured test concentrations
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Sampling method: Test Concentrations were measured in each  treatment at test initiation and at test termination
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method:   Stock solutions were prepared by direct addition of test article to algal  assay medium
Test organisms (species):
Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)
Details on test organisms:
- Species/strain # and source: Pseudokirchneriella subcapitata/Strain UTEX 1648,  from in-house cultures initiated from cultures originally supplied by the University of Texas at Austin.

- Initial Density 10,000 cells/mL
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
Not reported
Test temperature:
24.0 to 24.4ºC
pH:
7.6-7.7 at start of test

7.8-9.0 at end of test
Dissolved oxygen:
Not reported
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal concentrations: Negative Control, 7.5, 15, 30, 60 and 120 mg/L

Mean measured concentrations:
The large difference between nominal and mean measured exposure concentrations is attributed to the hydrolysis of the test substance under the static test conditions. The hydrolysis half-life of  methyltrimethoxysilane is approximately 2.2 hours.  All measured  concentrations on Day 3 were less than the limit of quantitation (LOQ =  0.27 mg/L).  Due to the decline in test concentrations during the test,  mean measured concentrations were estimated as the geometric mean of Day  0 and Day 3 measured concentrations.  The geometric mean concentrations  were calculated using ½  LOQ for all Day 3 measurements (0.135 mg./L).
Details on test conditions:
TEST SYSTEM

- Exposure vessel type:  250-mL Erlenmeyer flasks covered with a sponge  closure containing 100 mL of test solution.

- Test Design:  Three replicates for each treatment group.  Five test  concentrations and a negative control.

- Element basis (i.e. number of cells/ml, area under the curve, growth  rate, etc.): Yield (Biomass) and Growth Rate "  

- Growth/test medium chemistry:  Algal Assay Medium (ASTM E 1218-04), pH  7.6

- Dilution water source:  Distilled Water

- Water chemistry in test:  Temperature was measured in the environmental  chamber daily.  Measurements of pH were made in each treatment group at  test initiation and test termination.

- Light levels and quality during exposure:  490 to 626 foot-candles,  continuous cool-white fluorescent lighting
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 120 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Growth Rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 120 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Yield (Biomass) and Growth Rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 3.6 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: Growth Rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 3.6 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: Yield (Biomass) and Growth Rate
Details on results:
- Exponential growth in the control (for algal test): yes

- Observations:  Visual examination of algal cells at test termination showed no concentration-dependent changes in shape, color or size.
Reported statistics and error estimates:
Statistical methods: Dunnett's test was used to determine if there were differences between Control and treatments.

Table 1. Test results

 Nominal concentration (mg/L)

 Geometric mean measured concentration (mg/L)  Mean yield after 72 hours (cells/mL)  Percentage inhibition of yield  Mean growth rate 0 -72 hours  Percentage inhibition of growth rate  
 Control  Control  1098489  -  1.5692  -
 7.5  0.77  1116978  -1.7  1.5749  -0.4
 15  1.2  1112844  -1.3  1.5737  -0.3
 30  1.7  1048378  4.6  1.5532  1.0
 60  2.4  1080444  1.6  1.5635  0.4
 120  3.6  1092800  0.5  1.5676  0.1
Validity criteria fulfilled:
yes
Conclusions:
A 72-hour EC50 value of >3.6 mg/L and NOEC of ≥3.6 mg/L have been determined for the effects of the test substance on yield and growth rate of Pseudokirchneriella subcapitata based on geometric mean measured exposure concentrations of the test substance. The test substance is known to hydrolyse rapidly in water and 3.6 mg/L was the concentration measured in the highest nominal test concentration of 120 mg/L. It is therefore likely that the test organisms were predominantly exposed to the hydrolysis products of the substance.

Description of key information

Toxicity to Algae: 72-hour EC50 >120 mg/l and NOEC ≥120 mg/l (nominal) (>3.6 and ≥ 3.6 mg/l, respectively, measured) (highest concentration tested) (OECD 201 (Alga, Growth Inhibition test)), effects of the test substance on growth rate of Pseudokirchneriella subcapitata. The EC50 is equivalent to >83 mg/l when expressed in terms of the silanol hydrolysis product.

Key value for chemical safety assessment

Additional information

A 72-hour EC50 value of >120 mg/l and NOEC of ≥120 mg/l (nominal) (>3.6 and ≥3.6 mg/l, respectively, measured) (highest concentration tested) have been determined for the effects of trimethoxy(methyl)silane (CAS 1185-55-3) on growth rate of Pseudokirchneriella subcapitata (Dow Corning Corporation 2007). The test was carried out in accordance with test guideline OECD 201 and in compliance with GLP.

The test substance is known to hydrolyse rapidly and, in view of the test media preparation method/exposure regime, it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance. This is reflected in the low measured parent substance concentrations. Effect concentrations are therefore reported in terms of the nominal concentration.

The results may be expressed in terms of concentration of the silanol hydrolysis product, methylsilanetriol (CAS 2445-53-6; EC No. 219-489-9), by applying a molecular weight correction: (MW of silanol = 94.14 / MW of parent = 136.22) * (concentration of parent = >120 (3.6 mg/l measured)) = >83 mg/l as methylsilanetriol, nominal concentration (>2.5 mg/l measured concentration).

The chemical safety assessment focuses on the silanol hydrolysis product methylsilanetriol. Due to the static testing regime, the algal data with the registered substance reflects exposure to the hydrolysis products. However, the short-term fish and Daphnia data with the registered substance reflect exposure to a mixture of parent substance and hydrolysis products. To support the chemical safety assessment of the hydrolysis product, data for fish and Daphnia have therefore been read across from triethoxy(methyl)silane (CAS 2031-67-6; EC No. 217-983-9) which rapidly hydrolyses to methylsilanetriol and the organisms in the tests were exposed to methylsilanetriol.

For consistency and to show that the read-across and registered substance test data are comparable, algal toxicity data with triethoxy(methyl)silane have also been read across. A 48-hour EC50 value of >500 mg/l and a NOEC value of ≥500 mg/l have been determined for the effects of triethoxy(methyl)silane on growth rate of Pseudokirchneriella subcapitata in a test carried out according to test guideline EU Method C.3 and in compliance with GLP (Hazelton, 1994).

In view of the test media preparation method/exposure regime it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance. The results may be expressed in terms of concentration of the hydrolysis product, methylsilanetriol, by applying a molecular weight correction: (MW of silanol = 94.14 / MW of parent = 178.31) * (CONCENTRATION OF PARENT = >500) = >264 mg/l as methylsilanetriol.

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