2,2'-dibromobiphenyl

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:

Feb 12 - Nov 09, 2015

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

Details on sampling:

The concentrations of the test item were determined in fresh media (0 hours) and at the end of the exposure interval (72 hours) via HPLC - UV

Vehicle:

yes

Remarks:

water

Details on test solutions:

A saturated solution as stock solution (100 mg test item/L was weighed out) was freshly prepared with dilution water.
The stock solution was stirred for 24 hours (1100 rpm) with a magnetic stirrer. Undissolved particles were removed by membrane filtration (membrane filter 0.45 µm, RC, MACHEREY-NAGEL).
The saturated solution and further four dilution levels out of the saturated solution 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 nominal concentration levels of 6.25 - 12.5 - 25.0 - 50.0 - 100 mg/L.
The concentrations were based on the results of a preliminary range finding test (non GLP).

Test organisms (species):

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

Details on test organisms:

Test organism: Pseudokirchneriella subcapitata HINDAK, SAG 61.81
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:

0.24 mmol Ca+Mg/L

Nominal and measured concentrations:

nominal: 6.25 - 12.5 - 25.0 - 50.0 - 100 mg/L
measured: 9.40 - 17.1 - 43.8 - 84.1 - 168 µg/L

Details on test conditions:

Preculture A three days old preculture, prepared in dilution water, was used as inoculum.
Initial cell density
Nominal: approximately 5 x 103 - 104 cells/mL
Current: 6153 cells/mL
Incubation The flasks were positioned randomly and repositioned daily.
Temperature (target) Nominal range: 21 - 24 °C, controlled at ± 2 °C
Agitation Test containers were placed on a rotary shaker and oscillated at approximately 70 rpm.
Light intensity (target) 60 - 120 µE · m-2 · s-1
Light regime 24 hours/day light
Light source Fluorescent tubes, OSRAM L 36 W/11-865, cool daylight
Light homogeneity (target) Within ± 15 % over incubation area

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

106 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: SD: 95.8 - 131 µg/L

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

68.2 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: SD: 55.5 - 75.9 µg/L

Details on results:

The EC50-values with 95 % confidence intervals for inhibition of growth rate (ErC50) and yield (EyC50) after 72 hours were 106 (95.8 – 131) µg/L and 69.6 (59.9 – 76.4) µg/L, respectively

Results with reference substance (positive control):

ErC50 = 0.613 (0.589 - 0.638) mg/L

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
168	1	6153	5143	<LOQ	<LOQ
	2	6153	4779	3839	<LOQ
	3	6153	2863	<LOQ	<LOQ
	Mean	6153	4262	n.a.	n.a.
84.1	1	6153	12676	45999	412679
	2	6153	11873	40922	403898
	3	6153	15545	73828	622666
	Mean	6153	13365	53583	479748
43.8	1	6153	22777	267106	1617311
	2	6153	27255	281751	1566884
	3	6153	27249	314177	1677898
	Mean	6153	25760	287678	1620698
17.1	1	6153	33813	368179	1987421
	2	6153	29729	328101	1699599
	3	6153	30237	350649	1980334
	Mean	6153	31260	348976	1889118
9.40	1	6153	24408	396936	1621387
	2	6153	28058	364008	1695522
	3	6153	27337	265506	1508930
	Mean	6153	26601	342150	1608613
Control	1	6153	32825	378434	2244072
	2	6153	29043	363883	1739050
	3	6153	34289	397877	1843040
	4	6153	28782	376145	1669180
	5	6153	29438	355729	1718353
	6	6153	27995	322237	1544179
	Mean	6153	30395	365718	1792979

    < LOQ = below the limit of quantification (2736 cells/mL)        
    n.a. = data not determinable

2) Evaluation after 72 hours

Geometric mean measured test item concentration	Replicate	Growth rate		Inhibition of growth rate	Yield		Inhibition of yield
[µg/L]	No.	[d-1]		[%]	[cells/mL]		[%]
168	1		< LOQ	< LOQ		< LOQ	< LOQ
	2		< LOQ	< LOQ		< LOQ	< LOQ
	3		< LOQ	< LOQ		< LOQ	< LOQ
	Mean	(n.a.)	n.a.	n.a.	(n.a.)	n.a.	n.a.
84.1	1		1.40	26		406526	77
	2		1.40	26		397745	78
	3		1.54	19		616513	66
	Mean	(+)	1.45	24	(+)	473595	74
43.8	1		1.86	2		1611158	10
	2		1.85	2		1560731	13
	3		1.87	1		1671745	6
	Mean	(-)	1.86	2	(-)	1614545	10
17.1	1		1.93	-2		1981268	-11
	2		1.87	1		1693446	5
	3		1.93	-2		1974181	-10
	Mean	(-)	1.91	-1	(-)	1882965	-5
9.40	1		1.86	2		1615234	10
	2		1.87	1		1689369	5
	3		1.83	3		1502777	16
	Mean	(-)	1.86	2	(-)	1602460	10
Control	1		1.97			2237919
	2		1.88			1732897
	3		1.90			1836887
	4		1.87			1663027
	5		1.88			1712200
	6		1.84			1538026
	Mean		1.89			1786826

    < LOQ         = below the limit of quantification        
    n.a. = data not determinable   
    negative values    = growth stimulation

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

	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	1.67	2.45	1.78	1.97	0.418	21.2	27.6
	2	1.55	2.53	1.56	1.88	0.560	29.8
	3	1.72	2.45	1.53	1.90	0.486	25.6
	4	1.54	2.57	1.49	1.87	0.609	32.6
	5	1.57	2.49	1.58	1.88	0.532	28.3
	6	1.52	2.44	1.57	1.84	0.522	28.3
				Mean	1.89
				SD ±	0.04
				CV[%]	2.25

    SD = Standard deviation   
    CV = Coefficient of variation

4) Environmental Conditions

Geometric mean measured test item concentration		pH-value
[µg/L]		Start; 0 hours	End; 72 hours
168		7.56	7.47
84.1		7.56	7.52
43.8		7.56	7.59
17.1		7.56	7.66
9.40		7.58	7.71
Control		7.58	7.82
Room temperature [°C]:	min.: 22.0	max.: 22.5		mean value: 22.3
Light intensity [µEˆm-2ˆs-1]	n = 20	mean value: 76.1 range of the measured values: 69.8 to 81.5 equalling -8.31 to 7.06 %		CV [%]: 4.95

    CV = Coefficient of variation       
    n = number of measuring points

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

Sampling	0 h fresh medium	72 h old medium
Nominal loading rate of the test item [mg/L]	Test material
	Meas. conc. [µg/L]	Meas. conc. [µg/L]	[%]	Geometric mean measured test item concentration [µg/L]
100*	316	89.5	28	168
50.0	157	45.1	29	84.1
25.0	81.6	23.5	29	43.8
12.5	31.7	9.19	29	17.1
6.25	18.0	4.91	27	9.40
Control	< LOQ	< LOQ

    *        = saturated solution
    Meas. Conc    = Measured concentration of the test item (dilution factor taken into account), mean value of two replicates
    %    = Percent of the nominal concentration of the test item
    LOQ    = Limit of quantification  (3 µg/L test item)

Validity criteria fulfilled:

yes

Conclusions:

The EC50 value for inhibition of growth rate after 72 hours was determined to be 106 µg/L (geometric mean measured concentration) and the EC10 value for inhibition of growth rate after 72 hours was determined to be 68.2 µg/L (geometric mean measured concetration).

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 EC50-value with 95 % confidence intervals for inhibition of growth rate (ErC50) after 72 hours was 106 (95.8 – 131) µg/L and the EC10 value with 95% confidence intervals for inhibition of growth rate (ErC10) after 72 hours was 68.2 (55.5 – 75.9) µg/L, respectively. The effect values based on the geometric mean measured concentration of the test item.

Description of key information

The EC50 value for inhibition of growth rate after 72 hours was determined to be 106  µg/L (geometric mean measured concentration) and the EC10 value for inhibition of growth rate after 72 hours was determined to be 68.2 µg/L (geometric mean measured concetration).

Key value for chemical safety assessment

EC50 for freshwater algae:

106 µg/L

EC10 or NOEC for freshwater algae:

68.2 µg/L