Zinc sulfide (ZnS), manganese-doped

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

Reliability:

2 (reliable with restrictions)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Zinc sulphide

EC Number:

215-251-3

EC Name:

Zinc sulphide

Cas Number:

1314-98-3

Molecular formula:

SZn

IUPAC Name:

thioxozinc

Details on test material:

ZnS-SACHTOLITH HD-S; lot no 2230100; purity 98.3% +/- 0.6%; expiration date: 7 May 2003; storage conditions: at room temperature at about 20°C away from direct sunlight.

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

The following samples were taken:
Just before the start: duplicates amples from the test medium (without algae) and duplicate samples from the control (without algae);
After 72 hours: duplicate samples from the test medium (without algae) and duplicate samples from the control (without algae).
All samples were deep-frozen immediately after sampling. The concentration of the test item was analyzed in the duplicate test medium samples of the single test concentration for both sampling times (0 and 72h). From the control samples only one of the duplicate samples was analyzed from each of both sampling times.

Test solutions

Vehicle:

no

Details on test solutions:

synthetic test water prepared according to test guidelines. Test was started by inoculation of 10000 algal cells per ml test medium.

Test organisms

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

Strain No. 86.81 SAG supplied by the Sammlung von Algenkulturen Göttingen, Germany. The algae had been grown in the lab under standard conditions according to test guidelines.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test conditions

Test temperature:

22°C

pH:

start: 8.1
end: 9.3

Dissolved oxygen:

/

Nominal and measured concentrations:

Loading rate of 100mg/l translated into a mean measured test item concentration of 0.13 mg/l.

Details on test conditions:

Due to the insoluble properties of the test item, the study was performed as a limit test, using an undiluted filtrate of a supersaturated dispersion with the maximum concentration of dissolved test item as the only test concentration. The loading rate of 100mg/l was prepared by weighing 220 mg of the test item into 2200 ml test water. No auxiliary solvent or emulsifier was used. The test item was mixed into the test water as homogeneously as possible by ultrasonic treatment for 15 minutes and by intense stirring for 3 hours at room temperature in the dark to dissolve a maximum concentration of the test item in the dispersion. Then the solution was filtered through a membrane filter (0.45 µm) just before the start of the test.
The stirring period of 3h was chosen according to the results of a pre-test (without GLP) which showed that the solution equilibrium was reached after this time. The undiluted filtrate was used as test medium.
The test concentration was based on the results of a range-finding test and on results of a pre-experiment to the solubility of the test item.
The test method is also based on the OECD Guidance document on Aquatic Toxicity testing of Difficult Substances and Mixtures (OECD, 2000).

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 13 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

dissolved

Basis for effect:

growth rate

Remarks on result:

other: dissolved concentration corresponding to 100mg/l loading of ZnS

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 13 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

dissolved

Basis for effect:

growth rate

Remarks on result:

other: dissolved concentration corresponding to 100mg/l loading of ZnS

Details on results:

No effects were observed at the loading rate of 100mg/l of the substance (ZnS), corresponding to 13µg Zn/l in solution. Therefore the EC50 is expressed as ">".The 72h NOEC may have been higher than 13 µg/l but the loading rates in excess of 100 mg/l were not tested in accordance to the test guidelines.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

test valid for assessing acute toxicity of the substance to algae; results demonstrate no toxicity accoring to classification criteria

Executive summary:

A standard OECD 202 test on Scenedesmus subspicatus showes that at loading of 100mg substance/l, no effects are observed.