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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:
1995-01-02 to 1995-01-05
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study but potential for oligomerisation to have occurred during preparation of the stock
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
Nominal test concentrations: Control, 24, 107, 182, 322, 536 and 965 mg/l

The concentration of the stock solution used to prepare the test media was determined at the start and end of the test.

The concentration of the test media was determined at the start and end of the test.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Test media prepared by dilution of a 1000 mg/l stock solution prepared by mixing for 18 h followed by filtration. TOC concentration of stock solution determined.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM

- Strain: CHODAT (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. The cell concentration is determined from a calibration curve of absorbance at 685 nm versus cell density.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
Not reported
Test temperature:
24 +/-2ºC
pH:
Start of test: 8.6-8.7

End of test: 7.7-9.2
Dissolved oxygen:
Not applicable
Salinity:
Not applicable
Nominal and measured concentrations:
Measured concentration in stock solution at start of test: 1072 mg/l

Measured concentration in stock solution at end of test: 1043 mg/l

Nominal: Control, 24, 107, 182, 322, 536 and 965 mg/l

Measured concentrations in treatments at start of test: 62, 105, 181, 321, 544 and 928 mg/l

Measured concentrations in treatments at end of test: 57, 104, 184, 325, 607 and 928 mg/l

Concentrations used as the basis for assessing effects: Control, 24, 107, 182, 322, 536 and 965 mg/l
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: 20000 cells/ml

- 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 (with observation intervals if applicable):

- Determination of cell concentrations: spectrophotometer (absorption at 685 nm)

- Other:


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.7
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 536 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 536 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
503 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
402 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
322 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Validity criteria fulfilled:
yes
Conclusions:
A 72-h EC50 value of >536 mg/land a NOEC of 322 mg/l have been determined for the effects of the test substance on growth rate of Scenedesmus subspicatus. 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:
experimental study
Adequacy of study:
weight of evidence
Study period:
2002-05-17 to 2002-07-05
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: Control and nominal test concentrations of 4.6, 10, 22, 46 and 100 mg/l.

- Sampling method: Duplicate samples of test media that did not contain algae were taken at the start and end of the test. The analysis media were incubated under the same conditions as the test media.

- Sample storage conditions before analysis: The samples were immediately frozen to -20ºC.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Test media prepared by direct addition followed by stirring for 35 minutes.

- Controls: Algal growth medium
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM

- Strain: 86-81 SAG

- Source (laboratory, culture collection): Sannlung von Algenkulturen, Gottingen, Germany

- Age of inoculum (at test initiation): 4 days. Maintained in exponential growth phase by diluting three-fold on the day before the test.

- Method of cultivation: Culture grown in the same medium and under the same conditions used for the test.


ACCLIMATION

- Culturing media and conditions: same as test
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
˜24 mg/l (as CaCO3)
Test temperature:
22 - 23ºC
pH:
Start of test: 7.9 - 8.1

End of test: 9.0 - 9.6
Dissolved oxygen:
Not applicable
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal: Control, 4.6, 10, 22, 46 and 100 mg/l.

Measured concentration in 100 mg/l nominal treatment at start of test: 104 mg/l

Measured concentration in 100 mg/l nominal treatment at end of test: 92.5 mg/l

Mean measured concentration in 100 mg/l nominal treatment over the test: 96.5 mg/l
Details on test conditions:
TEST SYSTEM

- Test vessel: Erlenmeyer flasks

- Type (delete if not applicable): covered Erlenmeyer flasks

- Material, size, headspace, fill volume: glass, 50 ml, 15 ml fill volume

- Aeration: none

- Initial cells density: 10000 cells/ml

- Control end cells density: 662000 cells/ml

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

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


GROWTH MEDIUM

- Standard medium used: yes


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Sterile purified water

- 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: 7100 Lux (6400-7600 Lux) obtained from fluorescent tubes (Philips TLD 36W-1/840)


EFFECT PARAMETERS MEASURED (with observation intervals if applicable):

- Determination of cell concentrations: electronic particle counter (Coulter counter)


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2.2

- Range finding study

- Test concentrations: not reported

- Results used to determine the conditions for the definitive study: not reported
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
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

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no
Results with reference substance (positive control):
- EC50: not reported
Reported statistics and error estimates:
Dunnett's test was used to determine if there were significant differences between the Control and the highest treatment.

Table 1. Test results

 Nominal test substance concentration (mg/l)  Cell concentration at start of test (cells/ml)  Cell concentration after 24 hours (cells/ml)  Cell concentration after 48 hours (cells/ml)   Cell concentration after 72 hours (cells/ml)  Inhibition of growth rate at end of test (%)*  Inhibition of biomass at end of test (%)* 
 0 (Control)  10000  59000  129000  662000  -  -
 4.6  10000  54000  151000  735000  -2.5  -10.7
 10  10000  58000  130000  741000  -2.6 -7.9
 22  10000  52000  129000  731000  -2.3  -5.5
 46  10000  53000  122000  705000  -1.5  -1.8
 100  10000 55000   128000  701000  -1.4  -3.0

*A negative value indicates that growth rate or biomass was higher in the treated media than in the Control.

Validity criteria fulfilled:
yes
Conclusions:
A 72-h EC50 value of >100 mg/l and NOEC of =100 mg/l have been determined for the effects of the test substance on growth rate of Scenedesmus subspicatus. It is likely that the test organisms were primarily exposed to the hydrolysis products of the substance.

Description of key information

WoE Short-term toxicity to algae: 72 hr ErC50 >100 mg/l and NOEC of =100 mg/l (measured, highest concentration tested) according to EU C.2 (CAS 2530-85-0, Momentive 2002)

WoE Short-term toxicity to algae: 72 hr ErC50 >536 mg/l and NOEC of 322 mg/l (measured, highest concentration tested) according to EU C.2 (CAS 2530-85-0, Evonik 2000)

The observations in these study are attributed to the exposure of test organisms to the hydrolysis products in the test system.

Key value for chemical safety assessment

Additional information

A 72-h EC50 value of >100 mg/l and NOEC of =100 mg/l (measured, highest concentration tested) have been determined for the effects of the test substance (CAS 2530-85-0) on growth rate of Scenedesmus subspicatus. Test media were prepared by direct addition with stirring for 35 minutes. However in view of the exposure period it is likely that the test organisms were primarily exposed to the hydrolysis products of the substance (Momentive 2002).

In a second reliable test, a 72-h EC50 value of >536 mg/l and NOEC of 322 mg/L were determined. In this test, the registration substance would have been fully hydrolysed during preparation of stock solution (which was also filtered prior to the exposure period) (Evonik 2000). There is potential for oligomerisation to have occurred during preparation of the stock, however, high recoveries at the end of the test indicate that precipitation did not occur to a significant extent. At the loading levels corresponding to the NOEC and EC50 the concentration of monomeric silanol should have been stable in the test medium.

Both of these reliable studies provide useful weight of evidence for the hazard assessment.

Refer to the discussion in the Section 6 endpoint summary (Section 7.0 of CSR) for further discussion of the approach to chemical safety assessment for the registered substance.