Di-tert-butyl trisulphide

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:

October 26th to May 14th 2010

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

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Test solutions were sampled after 24, 48 and 72 hours and analysed for cell density using spectrophotometrical measurements. Samples were analysed for growth rate and yield of the algae.

Vehicle:

no

Details on test solutions:

Tests, conducted in 50ml Erlenmeyer flasks closed with a conical stopper using 50 ml of test solution, were inoculuated with 5000 cells per ml. Stock solutions were prepared just prior to test initiation by dissolving the test item by intense stirring before dilution to desired concentration with test water. Solutions were checked daily for the appearance of the test item.

Test organisms (species):

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

Details on test organisms:

Strain: 61.81 SAG. Cultured: IBACON laboratories. Source: "Sammlung von Algenkulturen, Pflanzenphysiologisches Institut der Universität Göttingen", 37073 Göttingen, Germany. An exponentially growing pre-culture was set up under test conditions 4 days prior to test initiation.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

No data reported

Hardness:

OECD medium was prepared and enriched with NaHCO3/L. Hardness: 24 mg/L (0.24 mmol/L) CaCO3.

Test temperature:

Water temperature: 23-24°C

pH:

At test initiation: 8.1-8.2. At test termination: 8.4-9.6.

Dissolved oxygen:

Not aerated - solutions were prepared and placed in stoppered flasks.

Salinity:

Freshwater OECD medium was prepared and enriched with NaHCO3/L.

Nominal and measured concentrations:

Solubility pre-experiments and range-finding tests were performed but have not been included in the report as they were not conducted under GLP. Nominal concentrations: 10, 3.2, 1.0, 0.32, 0.1 mg/L and control. Geometric mean concentrations: 3.90, 0.99, 0.38, 0.12, 0.04 mg/L and control. Blank controls were prepared without algae at each concentration and were analysed using spectrophotometrical measurements.

Details on test conditions:

Number of groups: 5 test groups and 1 control group. Number of replicates per group: 3 replicates for test concentrations and 6 replicates for control. Vessels were continuously illuminated with an mean intensity of 5065 lux.

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.838 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% confidence limits: 0.535-1.41

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.161 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% confidence limits: 0.032-0.298

Details on results:

Microscopic examination showed that algal cells showed no difference from the control after 72 hours in solutions of 10 mg/L nominal concentration.

Reported statistics and error estimates:

All endpoints were based on both nominal and geometric mean concentrations because concentrations of approximately 70% of nominal were found in freshly prepared solutions and the concentration decreased further with the age of the test substance.

[mg test item/L]	Growth rate	95 % conf. limits	Biomass	95 % conf. limits	Yield	95 % conf. limits
72-hour EC50	0.838	0.535-1.41	0.304	0.280-0.328	0.3	0.257-0.346
72-hour EC10	0.161	0.032-0.298	0.103	0.085-0.119	0.09	0.063-0.119
72-hour NOEC	0.04	-	0.04	-	0.04	-
72-hour LOEC	0.12	-	0.12	-	0.12	-
Values refer to geometric mean of test concentrations.
[mg test item/L]	Growth rate	95 % conf. limits	Biomass	95 % conf. limits	Yield	95 % conf. limits
72-hour EC50	2.45	1.63 - 3.72	0.815	0.747 - 0.888	0.81	0.708 - 0.926
72-hour EC10	0.472	0.129 - 0.844	0.260	0.211 - 0.305	0.23	0.166 - 0.292
72-hour NOEC	0.1	-	0.1	-	0.1	-
72-hour LOEC	0.32	-	0.32	-	0.32	-
Values refer to nominal test concentrations.

Validity criteria fulfilled:

yes

Conclusions:

The biomass, growth rate and yield 72 hour NOEC was 0.1 mg/L for nominal concentration and 0.04 mg/L for geometric mean concentrations and the LOEC was 0.32 mg/L for nominal concentrations and 0.12 mg/L for geometric mean concentrations. The 72 hour EC50 for nominal concentrations was 2.45 mg/L for growth rate, 0.815 mg/L for biomass and 0.81 mg/L for yield. The 72 hour EC50 for geometric mean was 0.838 mg/L for growth rate, 0.304 mg/L for biomass and 0.299 mg/L for yield.

Executive summary:

Kley (2010) is a GLP-compliant, 72 hour, static algae study following OECD guideline 201. Due to the volatile nature of the substance, the tests were conducted in closed vessels and geometric means were calculated from analytical measurements. Deviations from the study plan were made for the wavelength of detection light, but this was not thought to have affected the study as it was changed in order to improve the sensitivity of the analytical method. The study is considered reliable and suitable for use for this endpoint. The biomass, growth rate and yield 72 hour NOEC was 0.1 mg/L for nominal concentration and 0.04 mg/L for geometric mean concentrations and the LOEC was 0.32 mg/L for nominal concentrations and 0.12 mg/L for geometric mean concentrations. The 72 hour EC50 for nominal concentrations was 2.45 mg/L for growth rate, 0.815 mg/L for biomass and 0.81 mg/L for yield. The 72 hour EC50 for geometric mean was 0.838 mg/L for growth rate, 0.304 mg/L for biomass and 0.299 mg/L for yield.

Description of key information

Kley (2010) is a GLP-compliant, 72 hour, static algae study following OECD guideline 201. Due to the volatile nature of the substance, the tests were conducted in closed vessels and geometric means were calculated from analytical measurements. Deviations from the study plan were made for the wavelength of detection light, but this was not thought to have affected the study as it was changed in order to improve the sensitivity of the analytical method. The study is considered reliable and suitable for use for this endpoint. The 72 hour EC50 for geometric mean was 0.838 mg/L for growth rate inhibition. The 72 hour NOEC for geometric mean was 0.04 mg/L for growth rate inhibition.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.838 mg/L

EC10 or NOEC for freshwater algae:

0.04 mg/L

Additional information

Kley and Wydra (2010) is a GLP-compliant, 72 hour, static algae study following OECD guideline 201. Due to the volatile nature of the substance, the tests were conducted in closed vessels and geometric means were calculated from analytical measurements. Deviations from the study plan were made for the wavelength of detection light, but this was not thought to have affected the study as it was changed in order to improve the sensitivity of the analytical method. The study is considered reliable and suitable for use for this endpoint.