α-(2,4-dichlorophenyl)-1H-imidazole-1-ethanol

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:

weight of evidence

Study period:

From February 5th to February 8th, 2013

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Deviations:

yes

Remarks:

no analytical monitoring

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

yes

Remarks:

no analytical monitoring

GLP compliance:

no

Remarks:

No justification provided.

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: For the stock solution 75.0 mg of test item was solved in 500 ml OECD medium so that the nominal concentration was 150 mg/l. Correction for the active content was applied by using weighing correction factor (1.086 for Imidazol Ethanol (CAS No 24155-42-8)). Thus the actual concentration of the test item in the stock solution was 138 mg/l. Eight test solutions of different concentration were prepared by mixing appropriate volume of OECD medium and stock solution of the test substance. The applied concentrations were spaced by a factor 2.
- Eluate: OECD medium
- Controls: OECD medium
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): no.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: (Korshikov) F.Hindák
- Source (laboratory, culture collection): National Institute of Environmental Health
- Method of cultivation: The alga cells were passed from old seed stock cultures to fresh solid medium in every two or three weeks. The new seed cultures were kept under continuous illumination for five or seven days. After this grow phase they were kept in refrigerator. Three days before the test an inoculum culture was made by passing a small amount alga biomass from seed stock culture to 75 ml sterile OECD medium with a sterile inoculating loop. The inoculum culture was shaken and illuminated continuously for three days at 21 ± 2 °C. The test and control cultures were inoculated from log phase inoculum culture. The test and control cultures were shaken and illuminated continuously for three days at
21 ± 2 °C.

ACCLIMATION
- Acclimation period: no.
- Culturing media and conditions (same as test or not): yes.
- Any deformed or abnormal cells observed: no.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

21 ± 2 °C

pH:

7.8 ± 0.5

Nominal and measured concentrations:

0.2; 0.5; 0.9; 1.8; 3.7; 7.4; 14.7 and 29.4 mg/l (nominal).

Details on test conditions:

TEST SYSTEM
- Test vessel: conical glass flasks
- Type (delete if not applicable): closed, rubber plugs with a filter for ensuring the proper air exchange.
- Material, size, headspace, fill volume: glass, 150 ml, yes, 75 ml.
- Aeration: yes
- Initial cells density: 5001 cell/ml
- Control end cells density: 2 055 556 cell/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: Deionised water was used for preparing the media. The media was sterilized by filtration.
- Culture medium different from test medium: no.

OTHER TEST CONDITIONS
- Adjustment of pH: no.
- Photoperiod: continuous illumination.
- Light intensity and quality: 2880 – 3230 lux.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [counting chamber] At 24, 48 and 72 hours after the beginning of the test, the algal cell concentrations were determined by microscopically counting with a Bürker chamber. Microscopic observation of the algal cells was performed to detect any abnormal appearance in the algae.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study: The range of concentrations of the test item for the test was determined previously in a range-finding test (results not specified).

Reference substance (positive control):

yes

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.81 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

0.57 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.47 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Remarks on result:

not determinable because of methodological limitations

Details on results:

The evaluation of toxic effect was based on the nominal concentrations, which were modified by a correction factor for the active content (1.086). The NOEC and LOEC were determined with Fisher’s exact binominal test with Bonferroni correction. The results were inconclusive.

- 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.
- 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.
- Effect concentrations exceeding solubility of substance in test medium: no.

Reported statistics and error estimates:

The values of EC50 was determined by the ToxRat® statistic software.

Table 2. Determination of algae biomass.

Dilution level	Test item (mg/l)	Test vessel No.	0 h	24 h	48 h	72 h
1	29.4	1	5001	7813	10417	0
		11	5001	0	5208	2604
		21	5001	5208	0	5208
2	14.7	2	5001	0	13021	0
		12	5001	7813	0	2604
		22	5001	5208	2604	0
3	7.4	3	5001	15625	7813	5208
		13	5001	7813	0	0
		23	5001	15625	0	2604
4	3.7	4	5001	23438	20833	5208
		14	5001	10417	20833	18229
		24	5001	10417	5208	20833
5	1.8	5	5001	23438	15625	13021
		15	5001	20833	23438	23438
		25	5001	13021	13021	44271
6	0.9	6	5001	23438	96354	597222
		16	5001	36458	130208	583333
		26	5001	44271	119792	444444
7	0.5	7	5001	23438	125000	597222
		17	5001	23438	138021	666667
		27	5001	36458	122396	260417
8	0.2	8	5001	39063	145833	527778
		18	5001	26042	106771	486111
		28	5001	18229	70313	278646
Control	0	9	5001	28646	184896	750000
		10	5001	28646	145833	791667
		19	5001	31250	158854	819444
		20	5001	28646	161458	513889
		29	5001	26042	148438	527778
		30	5001	26042	156250	791667

 

Table 3. Measurements of pH.

Dilution level	Test item (mg/l)	Test vessel No.	pH at start of the test	pH at end of the test
1	29.4	1	7.88	7.45
		11		7.93
		21		7.90
2	14.7	2		7.81
		12		7.80
		22		7.88
3	7.4	3		7.76
		13		7.82
		23		7.88
4	3.7	4		7.80
		14		7.84
		24		8.88
5	1.8	5		7.87
		15		8.82
		25		7.85
6	0.9	6		9.06
		16		9.17
		26		8.70
7	0.5	7		9.02
		17		9.36
		27		8.68
8	0.2	8		8.31
		18		9.33
		28		8.03
Control	0	9		10.01
		10		9.47
		19		10.01
		20		7.89
		29		8.87
		30		9.26

 

Validity criteria fulfilled:

yes

Remarks:

See 'overall remarks, attachments'.

Conclusions:

The 72h EC50 value of the test item on Pseudokirchneriella subcapitata is 0.81 mg/l.

Executive summary:

A short-term toxicity test on aquatic algae was performed on the test item, according to OECD TG 201 / EU Method C.3, under GLP conditions. In accordance to a range-finding preliminary study, the nominal concentrations of test item used in the main experiment were: 0.2; 0.5; 0.9; 1.8; 3.7; 7.4; 14.7 and 29.4 mg/l (nominal). Three replicates were exposed to each of the test item concentrations, and six replicates were exposed to the control medium, for 72 hours under static conditions. No analytical monitoring was performed. The validity criteria were fulfilled. Based on the results obtained, the72h-EC50 value of the test item on Pseudokirchneriella subcapitata is 0.81 mg/L, and the 72h-EC10 value is 0.47 mg/L (based on growth rate). No NOEC value was obtained.

Description of key information

Key study. Method according to OECD TG 201 / EU Method C.3, GLP study. Based on the results obtained, the 72h-EC50 value of the test item on Pseudokirchneriella subcapitata is 0.81 mg/L, and the 72h-EC10 value is 0.47 mg/L (based on growth rate). Also, according to a calculation by ECOSAR v1.11 model, the 96-h LC50 of the test item on algae is 0.255 mg/l (ECOSAR v1.1, class: imidazoles).

Key value for chemical safety assessment

EC50 for freshwater algae:

0.81 mg/L

EC10 or NOEC for freshwater algae:

0.47 mg/L

Additional information

A short-term toxicity test on aquatic algae was performed on the test item, according to OECD TG 201 / EU Method C.3, under GLP conditions. In accordance to a range-finding preliminary study, the nominal concentrations of test item used in the main experiment were: 0.2; 0.5; 0.9; 1.8; 3.7; 7.4; 14.7 and 29.4 mg/l (nominal). Three replicates were exposed to each of the test item concentrations, and six replicates were exposed to the control medium,for 72 hours under static conditions.No analytical monitoring was performed. The validity criteria were fulfilled. Based on the results obtained, the72h-EC50 value of the test item on Pseudokirchneriella subcapitata is 0.81 mg/L,

A short-term toxicity test on aquatic algae was performed on the test item, according to OECD TG 201 / EU Method C.3, under GLP conditions. In accordance to a range-finding preliminary study, the nominal concentrations of test item used in the main experiment were:0.2; 0.5; 0.9; 1.8; 3.7; 7.4; 14.7 and 29.4 mg/l (nominal). Three replicates were exposed to each of the test item concentrations, and six replicates were exposed to the control medium,for 72 hours under static conditions.No analytical monitoring was performed. The validity criteria were fulfilled. Based on the results obtained, the72h EC50 value of the test item on Pseudokirchneriella subcapitata is 0.81 mg/L, and the 72h-EC10 value is 0.47 mg/L (based on growth rate). No NOEC value was obtained. Furthermore, according to a calculation by ECOSAR v1.11 model, the96-h LC50 of the test item on algae is 0.255 mg/l (ECOSAR v1.1, class: imidazoles).