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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:

experimental study

Adequacy of study:

key study

Study period:

28 April 2017 to 30 June 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Excess test solutions were sampled and at the end of the test one replicate of the dilution water control, solvent control and the test concentration was sampled
- Concentrations: all concentrations
- Sampling method: from excess test solutions at the start of the test and from one replicate of the dilution water control and solvent control and all replicates of the test concentration at the end of the test
- Sample storage conditions before analysis: no data

At the end of the tests all test concentration replicate vessels were rinsed with 20 ml of 0.5 mg/l Phenanthrene in hexane and an aliquot transferred to an auto-sampler vial for analysis

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION A primary stock concentrate of the substance with a nominal concentration of 500 g/L, was prepared by weighing a nominal 5 g of test substance and making up to 10 mL with the solvent tetrahydrofuran (THF) in a volumetric flask. The resultant stock was observed to be a clear and colourless solution and was used to prepare the test solutions. THF concentration in controls and exposure solutions was 0.1 mg/L.

Test solutions were clear and colourless.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: CCAP 278/4
- Source: laboratory culture maintained under axenic conditions
- Age of inoculum (at test initiation): 3 days

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

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

21.7-22.2 °C

pH:

7.18-8.11

Nominal and measured concentrations:

nominal: 0 and 50 mg/L
measured:

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL glass conical flask with 100 mL of test solution
- Type (delete if not applicable): closed with foam bung
- Aeration: none (shalen at 160 rpm)
- Initial cell concentration 0.5 E04 cells/mL
- Control end cells density: 25.03E04 and 22.4$04 cells/mL for medium and solvent control resp.
- No. of vessels per concentration (replicates):6
- No. of vessels per control (replicates):6
- No. of vessels per vehicle control (replicates):6

GROWTH MEDIUM
- Standard medium used: yes AAP medium according to OECD 201

TEST MEDIUM / WATER PARAMETERS
- Test medium: AAP medium according to OECD 201

OTHER TEST CONDITIONS
- Adjustment of pH: none
- Light intensity and quality: 600 Lux (cool white)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: Coulter counter
- Chlorophyll measurement: none

TEST CONCENTRATIONS: limit test at 50 mg/L (nominal)

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 20 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

20 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 20 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

20 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

Inhibition of growth compared to solvent controls was 0% and compared to cells density also 0%.

The recovery of the substance after the rinsing of the test vessels after 72 hours was 50% of the initial loading

Reported statistics and error estimates:

t test

Algal cell particle density

Mean measured concentration (mg/L)	Replicate	Algal cell particle density (10^4cells/mL)
		24 hours	48 hours	72 hours
Culture medium control	A	1.95	8.81	15.10
	B	1.52	4.99	23.60
	C	1.80	7.44	28.10
	D	1.72	6.93	27.40
	E	1.91	6.65	26.30
	F	1.86	7.20	29.70
	Mean	1.79	7.00	25.03
Solvent control	A	1.53	6.01	21.50
	B	1.59	5.85	25.10
	C	1.59	6.10	24.70
	D	1.63	7.07	20.60
	E	1.52	6.10	21.70
	F	1.58	5.37	20.80
	Mean	1.57	6.08	22.40
20	A	1.15	6.29	20.70
	B	1.14	7.62	25.10
	C	1.01	7.75	24.30
	D	1.04	7.89	22.00
	E	1.01	6.15	21.20
	F	1.11	7.37	21.20
	Mean	1.08	7.18	22.42

Inoculum (Day 0) cell density = 0.511 x 10⁴cells/mL

All values are quoted to 2 decimal places.

Analytical results

Nominal concentration (mg/L)	Measured concentration				Mean measured concentration    (mg/L)	Mean measured concentration (%)
	0 hour		72 hour
	(mg/L)	% of nominal	(mg/L)	% of nominal
Control	<LOQ	-	<LOQ	-	<LOQ	-
Solvent Control	<LOQ	-	<LOQ	-	<LOQ	-
50	31^a	61	10^b	20	20	41

All measurements are quoted to 2 significant figures

a    Mean of triplicate analyses: 33, 31 and 28 mg/L

b    Mean of triplicate analyses: 6, 13 and 13 mg/L

The limit of quantification (LOQ)in the study was 0.075 mg/L

Validity criteria fulfilled:

yes

Conclusions:

The ErC50 for the substance in algae is >20 mg/L
The NOEC is 20 mg/L

Executive summary:

In a limit test according to OECD 201 algae were exposed to the substance (measured concentration 20 mg/L with 0.1 mg/L THF in the test solution) for 72 hours. No effects on cell density or growth rate were observed. The NOEC is 20 mg/L. The ErC50 is > 20 mg/L.

Description of key information

In a limit test according to OECD 201 algae were exposed to the substance (measured concentration 20 mg/L with 0.1 mg/L THF in the test solution) for 72 hours. No effects on cell density or growth rate were observed. The NOEC is 20 mg/L. The ErC50 is > 20 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

20 mg/L

EC10 or NOEC for freshwater algae:

20 mg/L