6-sec-butylquinoline

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:

13th December 2018 to 26 February 2019

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)

Version / remarks:

Version from 23th March 2006

Deviations:

yes

Remarks:

The deviation can be considered as uncritical

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Name: 6-sec-butylquinoline
- Purity by GLC: > 99.2%
- Lot number: 6SBQ5/2017
- Molecular formula: C13H15N
- Molecular weight: 185.26955 g/mol

Analytical monitoring:

yes

Details on sampling:

Samples were diluted with an equal amount of acetonitrile (dilution factor 2). A second dilution step was done for the sample with higher concentrations (10 * LOQ) using acetonitrile / medium 50/50 (% v/v) in a ratio 1:1.

Vehicle:

no

Details on test solutions:

Date: 08. – 11. Jan. 2019
Treatments tested: 0.1 / 0.32 / 1 / 3.2 / 10 mg/L nominal concentration (The concentrations to be tested are based on non GLP pre-tests)

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 January 2016 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.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

not measured

Test temperature:

21.0 to 24.0 °C (the temperature fluctuates by more than ± 2 °C. As all validity criteria were met and exponential growth was observed in the blank control this was stated as uncritical)

pH:

7.5 to 9.1

Dissolved oxygen:

not measured

Salinity:

not measured

Conductivity:

not measured

Nominal and measured concentrations:

At the start and at the end of the test and every 24 hours, the content of the test item in the test solutions was determined using HPLC-UV.
The test item was not stable during the test. The measured concentrations lay between 89 % and 100 % of the nominal concentrations at the beginning of the test and between 48 % and 51 % of the nominal concentrations at the end of the test. In the lowest concen-tration the test item was no longer quantifiable after 24 hours incubation.
Therefore, the determination of the results was based on the geometric mean of the measured concentrations.
The lowest concentration is not necessary for evaluation, since the next higher concentration does not show any inhibition either. Therefore, the lowest concentration is not used for evaluation.

Details on test conditions:

TEST SYSTEM
- Test vessel: closed glass flasks total volume 65 mL
- Type (delete if not applicable): closed
- Aeration: no
- Initial cells density: 2580 cell/mL
- Control end cells density: 174533 cell/mL (72h)
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes (OECD TG 201 medium)

TEST MEDIUM / WATER PARAMETERS
- Intervals of water quality measurement: pH was measured at the beginning of the test and at the end for the control and all test concentrations.

OTHER TEST CONDITIONS
- Sterile test conditions: yes (all used solution were sterilized before use)
- Adjustment of pH: no
- Photoperiod: continuous lighting
- Light intensity and quality: 5000 Lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: electronic particle counter

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2
- Test concentrations: 0.1 / 0.32 / 1 / 3.2 / 10 mg/L nominal concentration
- Results used to determine the conditions for the definitive study: The concentrations to be tested are based on non GLP pre-tests

Reference substance (positive control):

yes

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.19 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.19 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

0.59 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

0.59 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.51 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

1.82 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.57 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Reported statistics and error estimates:

Calculation of results was performed with the help of validated software (Microsoft Ex-cel®). The estimation of the biological data was accomplished using the software ToxRat® Professional, version 3.2.1.

Validity criteria fulfilled:

yes

Conclusions:

The EC50 for growth rate inhibition (72h-EC50) was 1.82 mg/l based on nominal concentrations. The EC10 for growth rate inhibition was 0.30 mg/L based on nominal concentrations.

Executive summary:

The study was performed using 5 concentrations ranging from 0.1 to 10 mg/L. Incubation time (test systemDesmodesmus 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[1]were determined from the cell number at the respective observation times.

Significant inhibition of algal growth was observed at the following concentrations:

1 – 10 mg/L (nominal concentration)

 

At the start and at the end of the test and every 24 hours, the content of the test item in the test solutions was determined using HPLC-UV.

The test item was not stable during the test. The measured concentrations lay between 89 % and 100 % of the nominal concentrations at the beginning of the test and between 48 % and 51 % of the nominal concentrations at the end of the test. In the lowest concentration the test item was no longer quantifiable after 24 hours incubation.

Therefore, the determination of the results was based on the geometric mean of the measured concentrations.

The lowest concentration is not necessary for evaluation, since the next higher concentration does not show any inhibition either. Therefore, the lowest concentration is not used for evaluation.

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).

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.

The following results for the test item6-sec-butylquinolinewere determined:

Endpoint	NOEC	LOEC	EC10	EC50
Growth Rate	0.19 mg/L	0.59 mg/L	0.30 mg/L	1.82 mg/L
Yield	0.19 mg/L	0.59 mg/L	0.51 mg/L	0.57 mg/L

Note: According to the guideline, NOEC is determined by comparing of the respective treatment with the blank control. Statistically insignificant variation is considered as “no observed effect”, although the EC₁₀which is read from the graph toxicity vs. concentration may lie lower.

Description of key information

The EC50 for growth rate inhibition (72h-EC50) was 1.82 mg/l based on nominal concentrations. The EC10 for growth rate inhibition was 0.30 mg/L based on nominal concentrations.

Key value for chemical safety assessment

EC50 for freshwater algae:

1.82 mg/L

EC10 or NOEC for freshwater algae:

0.3 mg/L

Additional information

Endpoint	NOEC	LOEC	EC10	EC50
Growth Rate	0.19 mg/L	0.59 mg/L	0.30 mg/L	1.82 mg/L
Yield	0.19 mg/L	0.59 mg/L	0.51 mg/L	0.57 mg/L