Dichlobenil

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

Study period:

08 July 1987 to 20 July 1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: EPA Guideline 123-2

Deviations:

yes

Remarks:

(the protocol states algae are transferred into fresh medium regularly to provide 6- to 8-day old inoculum cultures. For this study the algae which had been cultures in MBL medium were transferred into fresh medium four days prior to testing).

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

50 mL taken from appropriate flasks of each treatment level and control. Two samples were taken from the nominal 1 mg/L flask as a check on reproducibility of analytical results. Three QA samples prepared for each test concentration.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: 5 mg/L stock solution prepared by adding 5.1 mg/L of test material to a 1 L volumetric flask and diluting to volume with MBL medium. The stock solution was ultrasonicated for approximately 30 minutes with heat to dissolve the test material. Test solutions were prepared by adding appropriate volumes of stock solution to 500 mL volumetric flasks and diluting to volume with MBL medium.

Test organisms (species):

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

Details on test organisms:

ACCLIMATION
- Culturing media and conditions (same as test or not): yes

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

120 h

Test temperature:

22-25 ºC

pH:

7.2-7.4 (0 hours); 10.2-10.6 (120 hours)

Nominal and measured concentrations:

0.13, 0.25, 0.50, 1.0, 2.0 and 4.0 mg/L (nominal)

0.085, 0.16, 0.35, 0.67, 1.4 and 3.2 mg/L (measured)

Details on test conditions:

TEST SYSTEM
- Test vessel: 125 mL volumetric flasks
- Material, size, headspace, fill volume: fill volume - 50 mL
- Initial cells density: 3 x 10E+3
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: yes - culture medium includes Na2EDTA

OTHER TEST CONDITIONS
- Photoperiod: continuous illumination
- Light intensity and quality: approximately 5000 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: using a hematcytometer at 24 hour intervals

TEST CONCENTRATIONS
- Range finding study
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

EC10

Effect conc.:

0 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95 % C.I. 0-1.3 mg/L

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

1.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95 % C.I. 0.11-3.4 mg/L

Key result

Duration:

48 h

Dose descriptor:

EC90

Effect conc.:

3.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95 % C.I. 2.0-5.7 mg/L

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.21 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95 % C.I. 0.038-0.99 mg/L

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

1.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95 % C.I. 0.22-5.7 mg/L

Key result

Duration:

72 h

Dose descriptor:

EC90

Effect conc.:

5.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95 % C.I. 1.1-38 mg/L

Key result

Duration:

96 h

Dose descriptor:

EC10

Effect conc.:

0.082 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95 % C.I. 0.01-0.44 mg/L

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

0.81 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95 % C.I. 0.15-5.0 mg/L

Key result

Duration:

96 h

Dose descriptor:

EC90

Effect conc.:

8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95 % C.I. 1.5-80 mg/L

Key result

Duration:

120 h

Dose descriptor:

EC10

Effect conc.:

0 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95 % C.I. 0-2.4 mg/L

Key result

Duration:

120 h

Dose descriptor:

EC50

Effect conc.:

2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95 % C.I. 0-9.7 mg/L

Key result

Duration:

120 h

Dose descriptor:

EC90

Effect conc.:

5.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95 % C.I. 1.7-23 mg/L

Details on results:

Mean cell densities determined at 24, 48, 72, 96 and 120 hours are presented in Table 1.

Based on these data EC10, EC50 and EC90 values were determined by linear regression. The 24 hour values could not be calculated, as there were too few cells.

Analysis of the test solutions demonstrated that the exposure concentrations ranged from 0.085 to 3.2 mg/L. No insoluble material was observed at any treatment level throughout the experiment.

Table 1: Mean cell density of Selenastrum capricornutm

	Cell density (x 10^4 cells/mL)
Nominal concentration (mg/L)	24 h	48 h	72 h	96 h	120 h
0	7.8	33	102	302	416
0.13	5.2	30	114	244	367
0.25	4.8	26	98	289	203
0.50	4.8	24	95	169	314
1.0	5.3	25	53	150	311
2.0	3.7	16	27	135	182
4.0	4.2	6.5	36	76	166

Validity criteria fulfilled:

not specified

Conclusions:

Under the conditions of the test, the 5 day EC50, using an effect criterion a reduction in cell density relative to the control, was determined to be 2 mg/L (95 % C.I. 0-9.7 mg/L).

Executive summary:

In a GLP compliant acute algal toxicity study conducted in line with standardised guideline EPA OPP 123-2, the acute toxicity to freshwater green alga of the test material over 5 days was determined. Algae were exposed to the test material at nominal test concentrations of 0, 0.13, 0.25, 0.50, 1.0, 2.0 and 4.0 mg/L (equivalent to mean measured concentrations of 0.085, 0.16, 0.35, 0.67, 1.4 and 3.2 mg/L). Under the conditions of the test, the 5 day EC₅₀ based on cell density was 2.0 mg/L (95 % C.I. 0 -9.7 mg/L).

Description of key information

The EC50 of the test material was determined to be 2 mg/L according to a study performed in line with EPA Guideline 123-2.

Key value for chemical safety assessment

EC50 for freshwater algae:

2 mg/L

Additional information

In the key GLP compliant acute algal toxicity study conducted in line with standardised guideline EPA OPP 123-2, the acute toxicity to freshwater green alga of the test material over 5 days was determined. Algae were exposed to the test material at nominal test concentrations of 0, 0.13, 0.25, 0.50, 1.0, 2.0 and 4.0 mg/L (equivalent to mean measured concentrations of 0.085, 0.16, 0.35, 0.67, 1.4 and 3.2 mg/L). Under the conditions of the test, the 5 day EC₅₀based on cell density was 2.0 mg/L (95 % C.I. 0 -9.7 mg/L).

In a supporting GLP compliant acute algal toxicity study conducted in line with standardised guideline EPA OPP 123-2, the acute toxicity to blue-green algae of the test material over 5 days was determined. Under the conditions of the test, the 5 day EC₅₀ based on cell density was determined to be 2.7 mg/L; the EC₅₀ based on impact on relative fluorescence was determined to be 7.4 mg/L.