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Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reason / purpose for cross-reference:

read-across source

pH:

7.0 - 7.5

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

27 mg/L

Nominal / measured:

nominal

Conc. based on:

not specified

Remarks:

cells/mL

Basis for effect:

cell number

Remarks on result:

other: 3.3 - 330 mg/L

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

120 mg/L

Nominal / measured:

nominal

Conc. based on:

other: specific growth rate

Basis for effect:

growth rate

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

3.3 mg/L

Nominal / measured:

nominal

Conc. based on:

other: cell/mL

Basis for effect:

cell number

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

3.3 mg/L

Nominal / measured:

nominal

Conc. based on:

other: growth rate

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): yes

- Unusual cell shape: There were no abnormalities detected in any of the control or test cultures

- Colour differences: no effects.

- Flocculation: no effects

- Adherence to test vessels: no effects.

- Aggregation of algal cells: no effects.

- Any stimulation of growth found in any treatment: no effects.

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: None.

- Effect concentrations exceeding solubility of substance in test medium: None.

Results with reference substance (positive control):

No data available

Reported statistics and error estimates:

None

Table 1: Test Results After 96 Hours

Concentration (mg/L)	Average cells /ml	Percent of Control
0 (control)	1,901,000	─
0.3	1,875,000	99
3.3	1,825,000	96
33	831,000	44
330	42,000	2
3300	<10,000	<1

Validity criteria fulfilled:

yes

Conclusions:

Exposure of freshwater alga to test material at concentrations of 0.3, 3.3, 33, 330, and 3,300 mg/L, plus an untreated control, was conducted in accordance with OECD Guideline 201 and US EPA (TSC) 797.1050. The study report was entitled as “range –finding study”, but the report was comprehensive and well documented. Therefore this study was regarded equivalent to definitive study with Klimisch code of 2.
From this study, a 96 hour EC50 of 27 mg/L (95% confidence interval = 3.3 to 330 mg/L) when calculated using cells/ml, and 120 mg/L (95% confidence interval =96 to 160 mg/L) when determined using the average specific growth rate were obtained. The 96 hour NOEC is 3.3 mg/L when determined using either the number of cells/ml or the average specific growth rate.

Executive summary:

The acute toxicity of the water accommodated fraction (WAF) of test material to the freshwater alga,Selenastrum capricornutum,was investigated during a range-finding study conducted at T.R. Wilbury Laboratories, Inc., in,. The test, which was designed to establish the approximate toxicity of the test substance, was performed for 96 hours from September 29 to October 3, 1997.

The test was performed at 24 ± 1°C under static conditions with a control (0 mg/L) and five concentrations of WAF (0.3, 3.3, 33, 330, and 3,300 mg/L). The dilution water was sterile enriched media adjusted to a pH of 7.5± 0.1. The five WAFS were prepared by formulating individual concentrations of the test substance and dilution water in mixing vessels equipped with a magnetic stirrer, stirring the mixtures for approximately 20 hours, settling the mixtures for approximately four hours, and siphoning the water phase containing the WAF. During the mixing period, the vortex extended approximately 25% of the distance from the water surface to the bottom of the mixing vessels. 

The 3,300 mg/L test solution was cloudy throughout the test. No other insoluble material was noted during the test. Exposure of the algae to the test substance resulted in the following growth after 96 hours:

Concentration (mg/L)	Average cells /ml	Percent of Control
0 (control)	1,901,000	─
0.3	1,875,000	99
3.3	1,825,000	96
33	831,000	44
330	42,000	2
3300	<10,000	<1

Exposure of freshwater alga to the test item resulted in a 96 hour EC50 of 27 mg/L (95% confidence interval = 3.3 to 330 mg/L) when calculated using cells/ml, and 120 mg/L (95% confidence interval =96 to 160 mg/L) when determined using the average specific growth rate. The 96 hour NOEC is 3.3 mg/L when determined using either the number of cells/ml or the average specific growth rate.

Description of key information

96 hour EC50 27 mg/L (95% confidence interval = 3.3 to 330 mg/L) when calculated using cells/ml,

and 120 mg/L (95% confidence interval =96 to 160 mg/L) when determined using the average specific growth rate were obtained.

The 96 hour NOEC is 3.3 mg/L when determined using either the number of cells/ml or the average specific growth rate.

Key value for chemical safety assessment

EC50 for freshwater algae:

27 mg/L

EC10 or NOEC for freshwater algae:

3.3 mg/L

Additional information

Exposure of freshwater alga to test material at concentrations of 0.3, 3.3, 33, 330, and 3,300 mg/L, plus an untreated control, was conducted in accordance with OECD Guideline 201 and US EPA (TSC) 797.1050. The study report was entitled as “range –finding study”, but the report was comprehensive and well documented. Therefore this study was regarded equivalent to definitive study with Klimisch code of 2.

From this study, a 96 hour EC50 of 27 mg/L (95% confidence interval = 3.3 to 330 mg/L) when calculated using cells/ml, and 120 mg/L (95% confidence interval =96 to 160 mg/L) when determined using the average specific growth rate were obtained. The 96 hour NOEC is 3.3 mg/L when determined using either the number of cells/ml or the average specific growth rate.