Registration Dossier

Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Currently viewing:

Administrative data

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:
10. Dec. 2018 - 13. Dec. 2018
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)
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
4.6 / 10 / 22 / 46 / 100 mg/L nominal concentration
Analytical monitoring:
yes
Vehicle:
no
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
Genus Desmodesmus
Species subspicatus
SAG Strain Number 86.81
Taxonomic position Chlorophyta - Chlorophyceae
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
21.2 – 22.2 °C
pH:
7.7 - 8.2
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
50.69 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
23.5 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
14.64 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
12.25 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
22 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
22 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
10 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
10 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Validity criteria fulfilled:
yes
Executive summary:

One valid experiment was performed.

The study was performed using 5 concentrations ranging from 4.6 to 100 mg/L. Incubation time (test system Desmodesmus subspicatus) was 72 hours. The cell concentration of each replicate was determined by measuring the cell numbers every 24 hours with an electronic particle counter. Growth rate µ and the yield were determined from the cell number at the respective observation times.

Significant inhibition of algal growth was observed at the concentrations 22 mg/L, 46 mg/L and 100 mg/L.

At the start and at the end of the test, the content of the test item in the test solutions was determined using HPLC. The measured concentrations lay between 98 % and 107 % of the nominal concentrations at the beginning of the test and between 99 % and 119 % of the nominal concentrations at the end of the test. Therefore, the biological results were based on the nominal concentrations.

The first replicate of the blank control was flocculated and therefore, this replicate was not used for the evaluation of the biological results.

The 72h-EC50values of potassium dichromate (K2Cr2O7, CAS No. 7778-50-9) were determined in a separate reference test. The values lay within the range of the laboratory (growth rate 0.73 - 1.10 mg/L, yield 0.21 – 0.66 mg/L).

 

The following results for the test itemN-(2-hydroxypropyl)imidazole, purified by distillationwere determined:

Table 3           Results of the Test Item

Endpoint

NOEC

LOEC

EC10

EC50

Growth Rate

10 mg/L

22 mg/L

14.64 mg/L

50.69 mg/L

Yield

10 mg/L

22 mg/L

12.25 mg/L

23.50 mg/L


[1]Yield (according to OECD Guideline 201) is defined as the biomass at the end of the exposure period minus the biomass at the start of the exposure period. Calculation see under 8.2 Growth and growth inhibition are quantified from measurements of the algal biomass as a function of time. Algal biomass is defined as the dry weight per volume, e.g. mg algae/L test solution. However, dry weight is difficult to measure and therefore surrogate parameters are used. Of these surrogates, cell counts are most often used.

Description of key information

A study according to OECD 201 was conducted.

Based on the test results the ErC50, 72h for Desmodesmus subspicatus can be stated to be 50.69 mg/L.

The ErC10 was determined to be 14.64 mg/L and the NOEC 10 mg/L, respectively.

Thus the test material is not toxic towards aquatic invertebrates according to the criteria of CPL.

Key value for chemical safety assessment

EC50 for freshwater algae:
50.69 mg/L
EC10 or NOEC for freshwater algae:
14.64 mg/L

Additional information