2,4-dithiapentane

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:

07.08.2017 to 10.08.2017

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)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II) (January 2012)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

For determination of the test item concentrations, three replicate samples (5 mL per replicate) were taken from each test concentration and six replicates (5 mL per replicate) from the control at the start and at the end of the test.

Vehicle:

no

Details on test solutions:

The test solutions used in the test was prepared by mechanical dispersion without using any solubilising agents. A stock solution was first prepared by dissolving an amount of 0.06 g test item in 600 mL dilution water (OECD Medium) to obtain the nominal concentration of 100 mg/L. The test solutions of subsequent lower test concentrations were prepared by appropriate diluting of this stock solution.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Raphidocelis subcapitata (Printz-Starr)
- Strain: 61.81 SAG (identical strains: CCAP 278/4; UTEX 1648; ATCC 22662)
- Source: SAG: Collection of Algal Cultures, Inst. Plant Physiology, University of Göttingen, Untere Karspüle 2, D-37073 Göttingen, Germany
- Method of cultivation: Small algal cultures that are regularly planted on agar are transferred to fresh medium at least once every two months under standardised conditions according to the test guidelines. Pre-culture was prepared with Algal Mineral Salts Culture Medium, incubated under the conditions of the test and used when still exponentially growing, normally after an incubation period of 2 - 4 days.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

not specified

Test temperature:

21.4 – 21.5°C (test vessel), 21.2 - 22.3°C (climate chamber)

pH:

7.61 – 10.19 (control: 9.82 -9.97)

Dissolved oxygen:

not specified

Salinity:

not applicable

Conductivity:

not specified

Nominal and measured concentrations:

The following nominal concentrations were tested: 0.95, 3.05, 9.77, 31.3 and 100 mg/L were investigated in the main study. Corresponding calculated geometric mean measured concentrations were: 0.63, 2.01, 7.23, 23.5 and 72.3 mg/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL Erlenmeyer flask
- Type: covered with air-permeable stoppers
- Medium volume per flask: 100 mL
- Initial cells density: 10^4 cells/mL
- Control end cells density: 104×10^4 cells/mL (mean value)
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

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

OTHER TEST CONDITIONS
- Photoperiod: continuously
- Light intensity and quality: 7885 lux, fluorescent lamps

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: counting chamber
- Morphological Changes of Algal Cells: microscopy

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2
- Range finding study: yes
- Test concentrations: 0.1, 1, 10 and 100 mg/L plus a control
- Results used to determine the conditions for the definitive study: significant growth inhibition at the test concentration of 100 mg/L

Reference substance (positive control):

yes

Remarks:

Potassium dichromate, test period: 07 – 10 March 2017

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

91.6 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

32.8 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

2.34 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

7.23 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

7.23 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

23.5 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

23.5 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

- Exponential growth in the control: Yes, cell density in the control has increased from nominal N = 1×10^4 cells/mL at the start of the test (0 hours) to 88.33x10^4 at the end of the test (72 hours).
- Observation of abnormalities: No morphological abnormalities were observed in the control and in the concentrations of 0.63, 2.01, 7.23 and 23.5 mg/L (mean measured).
Some swollen cells were observed in the highest concentration of 72.3 mg/L (mean measured) together with the normal cells during the test.

Results with reference substance (positive control):

The 72h ErC50: 0.99 mg/L (95 % confidence limits: 0.68 – 1.49 mg/L). The 72h EyC50: 0.59 mg/L (95 % confidence limits: 0.47 – 0.75 mg/L).

Reported statistics and error estimates:

For the determination of the LOEC and NOEC, ANOVA and Dunnett’s test (α = 0.05; 2-sided) was used and for the determination of the ECx values Probit analysis was used.

Validity criteria fulfilled:

yes

Conclusions:

In this 72-h algal growth inhibition test the effects of Bis(methylthio)methane on the growth of Raphidocelis subcapitata was determined. The 72-h EC10, EC20, EC50 for growth were determined to be 32.8, > 100 and > 100 mg/L, respectively. The 72-h EC10, EC20, EC50 for yield were determined to be 2.34, 8.23 and 91.6 mg/L, respectively. The LOEC and NOEC values based on growth rate and yield were determined to be 23.5 and 7.23 mg/L, respectively. The results are based on measured geometric mean test item concentrations.

Executive summary:

The purpose of this study was to determine the effect of the test item Bis(methylthio)methane on the growth of a unicellular green algal species Raphidocelis subcapitata. Exponentially growing cultures of Raphidocelis subcapitata were exposed to test item concentrations of 0.95, 3.05, 9.77, 31.3 and 100 mg/L ((corresponding to 0.63, 2.01, 7.23, 23.5 and 72.3 mg/L (geometric mean measured concentrations)). The algal growth in relation to a control culture was determined over a fixed test period of 72 hours. The 72-h EC10, EC20, EC50 for growth were determined to be 32.8, > 100 and > 100 mg/L, respectively. The 72-h EC10, EC20, EC50 for yield were determined to be 2.34, 8.23 and 91.6 mg/L, respectively. The LOEC and NOEC values based on growth rate and yield were determined to be 23.5 and 7.23 mg/L, respectively. The results are based on measured geometric mean test item concentrations.

Description of key information

The effect of the test item on the growth of a unicellular green algal species Raphidocelis subcapitata was determined according to OECD 201, Regulation (EC) No. 226/2016 Method C.3 and EPA OPPTS 850.5400 and under GLP (reference 6.1.5-1). The study was conducted under static conditions with an initial cell density of 1x10^4 cells/mL for a period of 72 hours. The EC50 and EC10 based on growth rate were determined to be > 100 mg/L and 32.8 mg/L (mean measured), respectively.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

32.8 mg/L

Additional information

The effect of the test item on the growth of a unicellular green algal species Raphidocelis subcapitata was determined according to OECD 201, Regulation (EC) No. 226/2016 Method C.3 and EPA OPPTS 850.5400 and under GLP (reference 6.1.5-1). The study was conducted under static conditions with an initial cell density of 1x10^4 cells/mL for a period of 72 hours. A stock solution of 100 mg/L was freshly prepared with OECD Medium and shaken overnight and the non-dissolved test material was separated by filtration. Five concentrations were tested in a geometrical series with a dilution factor of 3.2: 0.95, 3.05, 9.77, 31.3 and 100 mg/L ((corresponding to 0.63, 2.01, 7.23, 23.5 and 72.3 mg/L (calculated geometric mean concentrations)).The EC50 values for inhibition of growth rate (ErC50) was > 100 mg/L and for inhibition of yield (EyC50) 91.6 mg/L. The EC10 value was determined to be 32.8 mg/L based on growth rate (ErC10) and 2.34 mg/L based on yield (EyC10).