Phosphoric acid, chromium(3+) salt (1:2.5)

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

Study period:

28.05.2018-17.09.2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Phosphoric acid, chromium(3+) salt (1:2.5)

EC Number:

946-354-8

Molecular formula:

not applicable for UVCB

IUPAC Name:

Phosphoric acid, chromium(3+) salt (1:2.5)

Sampling and analysis

Analytical monitoring:

yes

Test solutions

Vehicle:

no

Test organisms

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

Specification: Unicellular freshwater green alga.
Genus Desmodesmus
Species subspicatus
SAG Strain Number 86.81
Taxonomic position Chlorophyta - Chlorophyceae
Origin and Culture:
The culture of Desmodesmus subspicatus was obtained in February 2014 by MBM Sci-encebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen). The algae are kept as stock culture on solid agar at 2 - 8 °C. From the stock culture, a permanent culture was prepared. From an aliquot of the permanent culture, the pre-culture was prepared.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test conditions

Nominal and measured concentrations:

0.1 / 0.32 / 1 / 3.2 / 10 / 32 / 100 mg/L (nominal)
0.06 / 0.18 / 0.55 / 1.76 / 5.5 / 17.6 / 55 mg/L (active ingredient)

Reference substance (positive control):

yes

Remarks:

Potassium dichromate K2Cr2O7

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

2.96 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

< 1.63 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: large difference between EC50 and NOEC due to strong growth in control

Details on results:

The result should be considered with care, as the growth factor in the control was well above the required value of 16fold. In this experiment a factor of 185 was determined. This leads to a decrease in the lowest concentration by 24%. However, the further reduction with increasing concentration is low (shallow concentration-response curve). A 50% reduction in growth rate was not reached at the highest test concentration.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The toxicity to aquatic algae was determined and the NOEC and EC50 for growth rate after 72 hours was <16 µg/L and 2.96 mg/L, respectively.

Executive summary:

The toxicity of of the test substance to Desmodesmus subspicatus was investigated in a study conducted according to OECD Guideline 201 (Alga, Growth Inhibition Test; 2006/2011) and EU Method C.3 (Algal Inhibition Test; 2008/2009). The 72 h NOEC and EC50 values based on growth rate were determined to be <16 µg/L and 3 mg/L, respectively. However, there is a strong growth in contraol taht may have an impact on the results. Therefore, the values should be used with care.