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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:
key study
Study period:
1994-05-10 to 1994-05-13
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 500 mg/l nominal treatment

- Sampling method: Samples of test media were taken at the start and end of the test

- Sample storage conditions before analysis: Refrigerated
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A 500 mg/l nominal concentration of the test substance was prepared by stirring overnight.

- Controls: Dilution water (algal growth medium)
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM

- Strain: CCAP 278/4

- Source (laboratory, culture collection): Culture Collection of Algae and Protozoa (CCAP), Institute of Freshwater Ecology, Ambleside, Cumbria, U.K.

- Age of inoculum (at test initiation): Cultures in exponential growth

- Method of cultivation: Axenic cultures maitained in liquid medium.


ACCLIMATION

- Culturing media and conditions: same as test
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Hardness:
no data
Test temperature:
24ºC
pH:
Control: 7.9 - 9.6

500 mg/l treatment: 7.9 - 9.3
Dissolved oxygen:
no data
Salinity:
not applicable
Nominal and measured concentrations:
Nominal concentration: 500 mg/l

Measured concentration at start of test: 486 mg/l

Measured concentration at end of test: 508 mg/l

Mean measured concentration: 497 mg/l

Mean measured concentration as a % of nominal: 99.4

The test results are presented and interpreted with reference to nominal concentrations.
Details on test conditions:
TEST SYSTEM

- Test vessel: Erlenmeyer flasks

- Type: closed

- Material, size, headspace, fill volume: Glass, 250 ml, no headspace, full

- Aeration: no

- Renewal rate of test solution (frequency/flow rate): no

- Initial cells density: 10000 cells/ml

- Control end cells density: ≈250000 cells/ml

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

- No. of vessels per control (replicates): 4


GROWTH MEDIUM

- Standard medium used: yes


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Standard algal growth medium in accordance with EU test method

- Culture medium different from test medium: no


OTHER TEST CONDITIONS

- Sterile test conditions: yes

- Adjustment of pH: no

- Photoperiod: Continuous

- Light intensity and quality: 12527 - 11745 Lux


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :

- Determination of cell concentrations: electronic particle counter
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 500 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is to hydrolysis product
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 500 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is to hydrolysis products
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 500 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is to the hydrolysis product
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 500 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is to the hydrolysis product
Basis for effect:
biomass
Details on results:
- Exponential growth in the control (for algal test): yes

- Any stimulation of growth found in any treatment: no
Reported statistics and error estimates:
No toxic effects were observed in the test media, the test results were therefore not subject to statistical analysis.
Validity criteria fulfilled:
yes
Conclusions:
A 72-hour EC50 value of >500 mg/l and NOEC of ≥500 mg/l have been determined for the effects of the test substance on growth rate of Pseudokirchnerella subcapitata (tested as: Selenastrum capricornutum) based on nominal concentration of the substance. However it is likely that the test organisms were primarily exposed to the hydrolysis products of the substance.
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The result was obtained by an appropriate predictive method.
Principles of method if other than guideline:
The ECOSAR ‘neutral organics’ QSARs for acute data have been applied and the effect concentrations calculated using log Kow and molar mass as input variables. An additional factor of *0.2 has been applied to the results.

The USEPA model ECOSAR was used as the basis for the estimation. This method is well-validated for ‘neutral organics’, i.e. those which act by a general narcotic mechanism, the potency of which is usually related to log Kow. Its scope is acute and long-term effects for the three standard trophic levels.

The method was validated for use with organosilicon compounds with a high weight percent of Si and limited or no additional functionality. Many of the reliable data for the category are limit values, therefore, the data were considered in terms of the range of the E(L)C 50, in accordance with normal classification bands:    

E(L)C50 < 1 mg/l;
E(L)C50 in the range > 1 mg/l to 10 mg/l;
E(L)C50 in the range > 10 mg/l to 100 mg/l;
E(L)C50 > 100 mg/l.

In general ECOSAR predicted correctly for most substances for each trophic level. However, performance was improved significantly by application of a factor of 0.2 to each predicted value (expressed in mg/l). The organosilicon substances are slightly more toxic than the general ECOSAR ‘neutral organics’ regression lines, although still well within the range of each model. The factor of 0.2 is applicable to fish,Daphniaand algae, across the whole range of log Kowvalues. It is concluded that the acute effects of the substances in the sub-category can therefore be predicted from ECOSAR, with a minor modification.
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
2 115 mg/L
Basis for effect:
growth rate
Conclusions:
A 96 h EC50 values of 2115 mg/L was obtained for the hydrolysis product of the submission substance using an appropriate calculation method . The results are considered to be reliable.
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Not reported
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
secondary literature
Remarks:
The result is reported in a peer reviewed secondary source, however there is insufficient information to fully assess its reliability.
Principles of method if other than guideline:
No guideline specified.
GLP compliance:
not specified
Analytical monitoring:
not specified
Vehicle:
not specified
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Test type:
static
Water media type:
freshwater
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
not specified
Conc. based on:
other: hydrolysis products
Basis for effect:
biomass
Conclusions:
An EC50 value of >1000 mg/L has been reported for the test substance to Selenastrum capricornutum. The result is reported in a peer reviewed secondary source, however there is insufficient information to fully assess its reliability. It is likely that the test organisms were primarily exposed to the hydrolysis products of the substance.

Description of key information

(72-hour) EC50: >500 mg/l growth rate Pseudokirchnerella subcapitata

(72-hour) NOEC: ≥500 mg/l growth rate Pseudokirchnerella subcapitata

(72-hour) LC50: 2115 mg/l growth rate, algae, hydrolysis product (using an appropriate calculation method)

Key value for chemical safety assessment

Additional information

A 72-hour EC50 value of >500 mg/l and NOEC of ≥500 mg/l have been determined for the effects of the test substance on growth rate of Pseudokirchnerella subcapitata (tested as: Selenastrum capricornutum) based on nominal concentration of the substance.

The study was conducted according to a standard guideline (EU Method C.3, Algal Inhibition test) and GLP and so was selected as key study (1994).

In support of this data, two other results of lower reliability, from secondary sources, are available and report EC50 values of >1000 mg/l for S. capricornutum and Anabaena flos-aquae. As the substance hydrolyses rapidly (half-life of approximately 5.5 hours), it is very likely that the test organisms were primarily exposed to hydrolysis product, methylsilanetriol. A 96-h LC50 of 2115 mg/l was derived for the hydrolysis product using an appropriate calculation method (2011).