Reaction mass of 6-(2-ethyl-6-methylanilino)-5-(4-{4-[ethyl(3-sulfobenzyl) amino] phenylazo} phenylazo)-4-hydroxynaphthalene-2-sulfonic acid, sodium and/or disodium salt(s) and 6-(2-ethyl-6-methylanilino)-5-(4-{4-[ethyl(4-sulfobenzyl) amino] phenylazo} phenylazo)-4-hydroxynaphthalene-2-sulfonic acid, sodium and/or disodium salt(s)

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2007

Report date:

2007

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2006

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Acid Navy RN-2682

IUPAC Name:

Acid Navy RN-2682

Test material form:

solid

Sampling and analysis

Analytical monitoring:

yes

Test solutions

Vehicle:

no

Test organisms

Test organisms (species):

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

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test conditions

Hardness:

24 mg CaCO3/l

Test temperature:

23 - 24 °C

pH:

8.3 - 10.9

Nominal and measured concentrations:

1, 3.2, 10, 32, 100 mg/l (nominal)
Mean measured concentrations varied in the range 21 to 101 % of nominal values, thus biological results are related to mean measured concentrations.
Geometric mean over all measurements per test concentration:
1 not analysed (below 72-h NOEC)
3.2 0.66 mg/l
10 8.9 mg/l
31 31.9 mg/l
100 101.3 mg/l

Details on test conditions:

Experimental part A: algae gorwn in presence of different test item concentrations
Experimental part B: alage grown in test water without test item; glass dishes above algal suspensions contained the coloured test item at the same concentrations as in part A.

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

ca. 7.7 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

ca. 37 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 3

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.66 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 4

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.66 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

The results in experimental parts A and B were compared based on growth rates. The EC values in experimental part B were higher than the corresponding EC values in experimental part A. Thus, only a part of the algal growth inhibition was caused by the light effect.
This modified algal test has demonstrated that the observed growth inhibition effect of the test item on Pseudokirchneriella subcapitata was caused in part by the indirect effect, the light absorption in the colored test solutions. However, the differences between experimental parts A and B were too high to state that the algal growth inhibition is only a result of a reduction in light intensity. Therefore, the results of experimental part A should be taken into consideration for the determination of the inhibitory effect of the test item on the growth of Pseudokirchneriella subcapitata.

Applicant's summary and conclusion

Conclusions:

EC50 (72h) for growth rate = 37 mg/l as based on measured concentrations