4-Ethoxy-2,3-difluoro-4'-methyl-1,1'-biphenyl

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:

28.03.2019 - 24.06.2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

water

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
A saturated solution with a nominal loading of 100 mg test item/L was prepared once 24 ± 1 hour prior to the start of the exposure. An appropriate amount of the test item was weighed out. The test
item was applied onto a glass slide. The glass slide with the test item was inserted into a brown glass bottle with an appropriate amount of dilution water. The saturated solution was
stirred for 24 ± 1 hours (1100 rpm, room temperature) with a magnetic stirrer. After a separation phase of 1 hour the saturated solution was removed by siphoning from the middle of the flask.
Undissolved particles were removed by membrane filtration (membrane filter 0.45 μm, RC, Macherey-Nagel). The filter was saturated in order to avoid adsorption during the filtration. The first 25 mL of the filtrate were discarded. The filtration was interrupted for 15 minutes to allow adsorption and saturation of the filter material with dissolved test item. Thereafter, the filtration was continued. The next 25 mL were discarded. The following test item solution was used in the test. During filtration, the filter was always kept covered. The saturated solution was checked via laser beam (Tyndall effect) for undissolved test item. The Tyndall effect was slightly positive.

Test organisms (species):

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

Details on test organisms:

Test organism: Pseudokirchneriella subcapitata HINDÁK CCAP 278/4 (axenic)
Origin: Sammlung von Algenkulturen (SAG), Pflanzenphysiologisches Institut der Universität Göttingen, Göttingen, Germany

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

32 mg CaCO3/L

Test temperature:

21.0-23.0 °C

pH:

7.92 - 9.48

Nominal and measured concentrations:

The geometric mean measured test item concentrations were calculated to: 5.42 - 17.9 - 56.6 - 176 - 406 μg/L
nominal: 6.25, 12.5, 25.0, 50.0, 100.0 mg/L

Details on test conditions:

The study was performed as a static test in open vessels under culture conditions. The flasks contained 100 mL either reconstituted water or test medium (test item group).
The duration of exposure was 72 hours. The algal biomass in each flask was determined daily during the exposure period via Chlorophyll a-fluorescence.
Microscopic evaluation of the cells at the start and at the end of the incubation period was carried out.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

81.4 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: SD: 70.6 - 108 µg/L

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

48.5 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: SD: 39.5 - 55.3 µg/L

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

5.42 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Results with reference substance (positive control):

The toxicity of potassium dichromate to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined over a period of 72 hours from 2019-03-05 to 2019-03-08. The reference item toxicity is in the valid range following test facility SOPs.
ErC50 = 0.752 mg/L, EyC50 = 0.405 mg/L

Reported statistics and error estimates:

The EC50-values for inhibition of growth rate (ErC50) and yield (EyC50) after 72 hours were 81.4 (70.6 - 108) μg/L and 37.1 (27.2 – 49.6) μg/L, respectively.

1) Cell Densities

Geometric mean measured test item concentration	Replicate	Cell density [cells/mL]
[µg/L]	No.	0 hours	24 hours	48 hours	72 hours
406	1	5416	5922	3965	2989
	2	5416	5010	4686	2960
	3	5416	7704	5241	2663
	Mean	5416	6212	4631	2871
176	1	5416	7950	5143	2775
	2	5416	6750	5810	3892
	3	5416	10574	8218	8130
	Mean	5416	8425	6390	4932
56.6	1	5416	14427	73953	408228
	2	5416	17620	136487	969509
	3	5416	16259	133118	839338
	Mean	5416	16102	114519	739025
17.9	1	5416	24379	199859	1306861
	2	5416	12319	186666	1148262
	3	5416	20193	195020	1483764
	Mean	5416	18964	193848	1312962
5.42	1	5416	21605	231121	1727213
	2	5416	24688	263649	1899930
	3	5416	22038	226662	1876855
	Mean	5416	22777	240477	1834666
Control	1	5416	25217	232133	2093043
	2	5416	23540	242580	1970029
	3	5416	23953	272771	1941113
	4	5416	25540	274612	1876904
	5	5416	21544	212535	1664805
	6	5416	20081	194143	1491943
	Mean	5416	23313	238129	1839640

2) Evaluation after 72 hours
Statistically significant differences of growth rates and yield compared to control values are marked (+), not significant differences are marked (-).

Geometric mean measured test item concentration	Replicate	Growth rate		Inhibition of growth rate	Yield		Inhibition of yield
[µg/L]	No.	[d-1]		[%]	[cells/mL]		[%]
406	1		-0.198	100		-2427	100
	2		-0.201	100		-2456	100
	3		-0.237	100		-2753	100
	Mean	(+)	-0.212	100	(+)	-2545	100
176	1		-0.223	100		-2641	100
	2		-0.110	100		-1524	100
	3		0.135	93		2714	100
	Mean	(+)	-0.066	98	(+)	-484	100
56.6	1		1.44	26		402812	78
	2		1.73	11		964093	47
	3		1.68	13		833922	55
	Mean	(+)	1.62	17	(+)	733609	60
17.9	1		1.83	6		1301445	29
	2		1.79	8		1142846	38
	3		1.87	4		1478348	19
	Mean	(+)	1.83	6	(+)	1307546	29
5.42	1		1.92	1		1721797	6
	2		1.95	-1		1894514	-3
	3		1.95	0		1871439	-2
	Mean	(-)	1.94	0	(-)	1829250	0
Control	1		1.99			2087627
	2		1.97			1964613
	3		1.96			1935697
	4		1.95			1871488
	5		1.91			1659389
	6		1.87			1486527
	Mean		1.94			1834224

3) Section-by-Section and Average Specific Growth Rates of the Control Group (0 - 72 hours)

	Replicate No.	Specific growth rate [d-1]			Mean (0 - 72 hours)	SD ±	CV [%]	Mean CV [%]
		section-by-section
		0 - 24 hours	24 - 48 hours	48 - 72 hours
Control	1	1.54	2.22	2.20	1.99	0.388	19.5	23.2
	2	1.47	2.33	2.09	1.97	0.446	22.7
	3	1.49	2.43	1.96	1.96	0.473	24.1
	4	1.55	2.38	1.92	1.95	0.413	21.2
	5	1.38	2.29	2.06	1.91	0.472	24.7
	6	1.31	2.27	2.04	1.87	0.500	26.7
				Mean	1.94
				SD ±	0.04
				CV [%]	2.15

4) Environmental Conditions

Geometric mean measured test item concentration		pH-values
[µg/L]		Start; 0 hours	End; 72 hours
406		8.10	7.92
176		8.01	8.07
56.6		8.02	8.55
17.9		8.01	9.39
5.42		8.04	9.48
Control		8.11	9.47
Room temperature [°C]:	min.: 21.0	max.: 23.0		mean value: 22.0
Light intensity [lux]	n = 24	mean value: 5499 range of the measured values: 4751 to 6050 equalling -13.6 to 10.0%		CV [%]: 6.01

5) Measured Concentration of the test material in the Definitive Test with Algae

Sampling date	Fresh Media, 0 hours	Old Media, 72 hours
Dilution level of the saturated Solution [%]	Test item
	Meas. conc. [µg/L]	Meas. conc. [µg/L]	%	Geometric mean measured concentration [µg/L]
100	485	341	70	406
50.0	253	122	48	176
25.0	132	24.3	18	56.6
12.5	60.6	5.30	9	17.9
6.25	27.9	1.05	4	5.42
Control	< LOQ	< LOQ

Validity criteria fulfilled:

yes

Conclusions:

The 72-h EC50 for growth rate was determined to be 81.4 µg/L and the 72-h EC10 value was determined to be 48.5 µg/L based on growth rate.

Executive summary:

The information for this endpoint study record was obtained from an experimental study. The OECD GLP criteria were met and the methods applied are fully compliant with OECD TG 201.

 

The study was conducted under static conditions with an initial cell density of 5416 cells/mL.

A saturated solution with a nominal loading of 100 mg test item/L was prepared once at room temperature 24 ± 1 hour prior to the start of the exposure. An appropriate amount of the test item was weighed out. The test item was applied onto a glass slide. The glass slide with the test item was inserted into a glass bottle with an appropriate amount of dilution water. The saturated solution was stirred for 24 ± 1 hour (1100 rpm, room temperature) with a magnetic stirrer. After a separation phase of 1 hour (at room temperature), the saturated solution was removed by siphoning (from the approximate middle of the glass flask) and used in the test. The saturated solution was checked via laser beam (Tyndall effect) for undissolved test item. The Tyndall effect was slightly positive.

Five test item concentrations were tested in a geometrical series with a dilution factor of 2: 6.25 - 12.5 - 25.0 - 50.0 - 100 % of the saturated solution, corresponding to the geometric mean measured test item concentration of 5.42 – 17.9 – 56.6 – 176 – 406 µg/L. Three replicates were tested for each test item concentration and six replicates for the control. The environmental conditions were within the acceptable limits.

The 72-h EC50 for growth rate was determined to be 81.4 µg/L and the 72-h EC10 value was determined to be 48.5 µg/L based on growth rate.

Description of key information

The 72-h EC50 for growth rate was determined to be 81.4 µg/L and the 72-h EC10 value was determined to be 48.5 µg/L based on growth rate.

Key value for chemical safety assessment

EC50 for freshwater algae:

81.4 µg/L

EC10 or NOEC for freshwater algae:

48.5 µg/L

Additional information

The information for this endpoint study record was obtained from an experimental study. The OECD GLP criteria were met and the methods applied are fully compliant with OECD TG 201.

 

The study was conducted under static conditions with an initial cell density of 5416 cells/mL.

A saturated solution with a nominal loading of 100 mg test item/L was prepared once at room temperature 24 ± 1 hour prior to the start of the exposure. An appropriate amount of the test item was weighed out. The test item was applied onto a glass slide. The glass slide with the test item was inserted into a glass bottle with an appropriate amount of dilution water. The saturated solution was stirred for 24 ± 1 hour (1100 rpm, room temperature) with a magnetic stirrer. After a separation phase of 1 hour (at room temperature), the saturated solution was removed by siphoning (from the approximate middle of the glass flask) and used in the test. The saturated solution was checked via laser beam (Tyndall effect) for undissolved test item. The Tyndall effect was slightly positive.

Five test item concentrations were tested in a geometrical series with a dilution factor of 2: 6.25 - 12.5 - 25.0 - 50.0 - 100 % of the saturated solution, corresponding to the geometric mean measured test item concentration of 5.42 – 17.9 – 56.6 – 176 – 406 µg/L. Three replicates were tested for each test item concentration and six replicates for the control. The environmental conditions were within the acceptable limits.

The 72-h EC50 for growth rate was determined to be 81.4 µg/L and the 72-h EC10 value was determined to be 48.5 µg/L based on growth rate.