2-ethylhexyl 10-ethyl-4,4-dimethyl-7-oxo-8-oxa-3,5-dithia-4-stannatetradecanoate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Preferred study for this SIDS endpoint; GLP guideline study. No analytical confirmation of exposure concentrations.

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Details on sampling:

not applicable

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A single 1,000 mg/L WAF was formulated by combining 0.5 g of test substance and 500 ml of dilution water in a glass mixing vessel equipped with a magnetic stirrer (the vortex extended approximately 25% of the distance from the surface to the bottom of the mixing vessel). The mixture was stirred for approximately 24 hours and allowed to settle for approximately 1 hour. Following the settling period the water phase containing the WAF was removed from the mixing vessel with a siphon using care to exclude any material on the surface, bottom, or sides of the mixing vessel. Test media was prepared at 0.10, 1.0, 10, 100, and 1,000 mg/L by combining the appropriate volume of the 1,000 mg/L WAF and dilution water.
- Eluate: NA
- Differential loading: NA
- Controls: Dilution water control
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): None
- Concentration of vehicle in test medium (stock solution and final test solution(s) including control(s)): Dilution control, 1.10, 1.0, 10, 100, and 1,000 mg/L.
- Evidence of undissolved material (e.g. precipitate, surface film, etc): The 1,000 mg/L WAF was cloudy throughout the test. No other insoluble material was observed during the test.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: Green algae
- Strain: Selenastrum capricornutum
- Source (laboratory, culture collection): University of Texas at Austin and delivered to T.R. Wilbury on April 11, 1995.
- Age of inoculum (at test initiation): The inoculum used for the test was from a single source that had been growing for 8 days prior to testing.
- Method of cultivation: No data


ACCLIMATION
- Acclimation period: Approximately 14 days
- Culturing media and conditions (same as test or not): Same as test media.
- Any deformed or abnormal cells observed: No

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Post exposure observation period:

not applicable

Hardness:

no data

Test temperature:

24.0 deg. C at test initiation to 23.9 deg. C at test termination

pH:

7.3-10.2

Dissolved oxygen:

no data

Salinity:

no data

Nominal and measured concentrations:

nominal: 0.10, 1.0, 10, 100 and 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 125 500 ml glass Erlenmeyer flasks
- Type (delete if not applicable): open / closed open
- Material, size, headspace, fill volume: Fill volume was less than 50% of vessel volume.
- Aeration: Rotary shaker adjusted to 100 ppm in an incubator
- Type of flow-through (e.g. peristaltic or proportional diluter): Static
- Renewal rate of test solution (frequency/flow rate): None
- Initial cells density: 10, 000 cells/ml
- Control end cells density: 1,804,000 cells/ml
- No. of organisms per vessel: 10,000 cells/ml
- No. of vessels per concentration (replicates): 2 Replicates
- No. of vessels per control (replicates): 2 Replicates
- No. of vessels per vehicle control (replicates): None


GROWTH MEDIUM
- Standard medium used: yes/no Yes, sterile enriched media identical to media used for this test and maintained at test conditions for at lest 14 days before the definitive test. The inoculum used for the test was from a single source that had been growing for 8 days prior to testing.
- Detailed composition if non-standard medium was used: NA


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Water used for acclimation of test organisms and for all toxicity testing was sterile enriched media with a pH of 7.5. Dilution water was analyzed for particulate matter at the start of the test and media from a control vessel was analyzed for particulate matter at the end of the test.

- Total organic carbon: non detect
- Particulate matter: non detect at 0-hr; 33 mg/L at 96-hr
- Metals: all non detect; iron 0.03 mg/L
- Pesticides: non detect
- Chlorine: non detect
- Alkalinity: no data
- Ca/mg ratio: no data
- Conductivity: NA
- 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: 24 hour’s light
- Light intensity and quality: Approximately 400 foot-candles
- Salinity (for marine algae): NA


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Growth rate- see table
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter]


- Chlorophyll measurement: NA
- Other: Calculations and Statistical Methods – The average specific growth rate was calculated as the natural log of the number of cells/ml at 72 and 96 hours minus the natural log of the number of cells/ml at 0 hours divided by the exposure period. The percent change from the control was calculated by subtracting the treatment average specific growth rate from the control average specific growth rate, dividing the difference by the average specific growth rate in the control, and multiplying that value by 100. The EC50 and NOEC values were calculated using nominal concentrations of test substance, when warranted. The values were computed twice, once using the average number of cells/ml at each concentration expressed as a percent of the control and a second time using the average specific growth rate expressed as the percent change from the control. The binomial/nonlinear interpolation method (Stephan, 1983) was used to calculate EC50 values. The slope of the 96-hour dose response curve (cell density) was computed using the probit method. The no observed effect concentration (NOEC) is the highest concentration of test substance that allowed cell growth equal to at least 90% of the control growth.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: Each concentration approximately 10% of the next higher concentration.
- Justification for using fewer concentrations than requested by guideline: NA
- Range finding study
- Test concentrations: 1.10, 1.0, 10, 100, 1,000 mg/L
- Results used to determine the conditions for the definitive study: This is a range finding study.

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

270 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

120 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: cell density

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: cell density

Details on results:

- Exponential growth in the control (for algal test): Yes
- Observation of abnormalities (for algal test): No
- Unusual cell shape: No
- Colour differences: No
- Flocculation: No
- Adherence to test vessels: No
- Aggregation of algal cells: No
- Other: After 120 hours, examination of the media from the flask containing a 0.50 ml subsample of test media from the flask containing the 1,000 mg/L Alkyltin MA WAF and 50 ml of fresh media contained 472,000 algal cells/ml, indicating that the effect of the test substance at the concentration was algistatic.
- Any stimulation of growth found in any treatment: No
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: The 1,000 mg/L WAF was cloudy throughout the test. No other insoluble material was observed during the test.
- Effect concentrations exceeding solubility of substance in test medium: greater than 1,000 mg/L

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

Data were evaluated using the binomial/non-linear interpolation method (Stephan 1983). The slope of the 96-h dose response curve (cell density) was computed using the probit methd. The NOEC was defined as the highest concentration tested that allowed cell growth equal to at least 90% of the control growth.

Mean cell growth data (number of cells/ml x 10^3) at 72 hours, by nominal  concentration of the WAF tested:
Control (0 mg/l): 838 (72 h)
0.10 mg/l: 811 (72 h)
1.0 mg/l: 822 (72 h)
10 mg/l: 803 (72 h)
100 mg/l: 465 (72 h)
1000 mg/l: <13 (72 h)

Average specific growth rate at 72 hours, by nominal concentration of the  WAF tested:
Control (0 mg/l): 0.062 (72 h)
0.10 mg/l: 0.061 (72 h)
1.0 mg/l: 0.061 (72 h)
10 mg/l: 0.061 (72 h)
100 mg/l: 0.053 (72 h)
1000 mg/l: 0.004 (72 h)

Validity criteria fulfilled:

yes

Conclusions:

Exposure of the freshwater alga, Selenstrum capricornutum, to the test substance resulted in a 72-h EC50 based on growth rate of 270 mg/L and a 72-h NOEC based on growth rate of 10 mg/L .

Executive summary:

The toxicity of the WAF of the test substance tot he freshwater alga, Selenastrum capricornutum, was investigated during a range-finding study. The test was performed under static conditions with the WAF of 0.10, 1.0, 10, 100 and 1000 mg/L mixtures of test substance and water. Cell counts were made at 0, 72 and 96 hours with a hemocytometer.

A 72 -h EC50 based on the growth rate was 270 mg/L with a no observed effect concentration at 72 -h of 10 mg/L based on growth rate.

Description of key information

EC50 (72-h) 270 mg/L based on growth rate for Selenastrum capricornutum (OECD 201)

Key value for chemical safety assessment

EC50 for freshwater algae:

270 mg/L

EC10 or NOEC for freshwater algae:

10 mg/L

Additional information

The toxicity testing available for the test substance is a range-finding study conducted with the freshwater alga, Selenastrum capricornutum. The study was performed under GLP conditions and followed OECD testing guideline 201. A water accommodated fraction (WAF) of the test substance was prepared for testing. The NOEC was defined as the highest concentration tested that allows cell growth equal to at least 90% of the control growth. The 72 -hr NOEC was 10 mg/L based on growth rate. The 72-hr EC50 was 270 mg/L, based on growth rate.