Disodium 2,5-dichloro-4-(5-hydroxy-3-methyl-4-(sulphophenylazo)pyrazol-1-yl)benzenesulphonate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

From July 30th to August 02nd, 2001

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Justification for type of information:

Justification for Read Across is reported in the endpoint summary and it is further detailed in the report attached to the IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

not specified

Details on test solutions:

A stock solution was prepared diluting 156.5 mg/l of test item in demineralized water (giving a concentration of 125 mg/l).

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Scenedesmus subspicatus CHODAT.
- Source: Collection of Culture Algae, Insitute of Plant Physiology of Gottingen University

ACCLIMATION
- Culturing media and conditions: the culture was kept in stock to 8 ° C. Three days before the start of the test was incubated at 8000 lux to promote exponential growth.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

21 ± 2 °C

Nominal and measured concentrations:

125 mg/l, nominal

Details on test conditions:

TEST SYSTEM
- Test vessel: 8 ml tubes open, agitated individually.
- No. of vessels per concentration: 3 replicates.
- No. of vessels per control: 3 replicates.

EFFECT PARAMETERS MEASURED
Determination of light absorption in the cuvettes at the beginning and end of the test period with spectrophotometer PU 8625 at λ = 440 nm against test batch without algae. In the ranges where the measured, the cell number and the optical density are proportional to each other.

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 125 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

ca. 125 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

The No Observed Effect Level at 72 hours resulted to be lower than 125 mg/l.

The factor 16 required in the control approach within 72 hours corresponds to a growth rate of 0.9. A growth rate of 1.40 was achieved.
The pH of the control batch should not change by more than 1.5 units; in the test, the change was 0.8 units.

Extinctions

Nominal conc. (mg/l)	E (0h)	E (24h)	E (48h)	E (72h)
0	6	54	193	386
0	6	55	205	392
0	6	50	161	351
120	6	20	92	230
120	6	12	97	233
120	6	17	94	229

Data obtained

Nominal conc. (mg/l)	Biomass		Growth rate		Average of inhibition (%)
	Value	Inhibition	Value	Inhibition	Biomass	Growth rate
0	425.00	-3.03	1.41	-0.63	0!	0!
0	441.00	-6.91	1.41	-1.00
0	371.50	9.94	1.38	1.64
120	212.00	48.61	1.23	11.73	48.8	11.7
120	210.50	48.97	1.24	11.42
120	210.50	48.97	1.23	11.83

Conclusions:

ErC50 (72h) > 125 mg/l (nominal)
EbC50 (72h): 125 mg/l (nominal)

Executive summary:

Method

The influence of the test item on the growth of the green algal species Desmodesmus subspicatuswas investigated in a 72-hour test according to the OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test).

Result

ErC50 (72h) > 125 mg/l (nominal)

EbC50 (72h): 125 mg/l (nominal)

Description of key information

ErC50 (72h) > 125 mg/l (nominal)

EbC50 (72h): 125 mg/l (nominal)

Key value for chemical safety assessment

EC50 for freshwater algae:

125 mg/L