STI571 F8

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: Directive 87/302/EEC, Method C.11.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Test material form:

solid: particulate/powder

Details on test material:

Batch number: 022401

Sampling and analysis

Analytical monitoring:

not specified

Test solutions

Details on test solutions:

A stock solution of nominally 1500 mg/l of "STl571 FB" in deionised water was prepared. Appropriate amounts of these stock solution were added to the different samples at the beginning of the incubation.
A stock solution of 3,5-dichlorophenol (nominally 0.5 /l) was prepared by dissolving 50 mg of the substance in 100 ml of deionised water. Three concentrations, nominally from 5 to 30 mg/l, were prepared.
All incubation mixtures were prepared by mixing 200 ml of microbial inoculum and 200 ml of synthetic sewage solution (see 4.7.2) with 100 ml of tap water or the appropriate dilution of the test or control substance in glass beakers with a nominal volume of 1000 ml.
The samples consisted of two negative controls (one at the beginning and one at the end of the series), five concentrations of "STl571 F8" and three concentrations of the positive control (3,5-dichlorophenol).
After mixing , the samples were aerated at a flow rate of 0.8 Umin using oil free compressed air and a Pasteur-pipette as aeration device.

The incubation of the individual samples was started at inte,rvals of 12-15 min and each sample was aerated for 3 hours at 18 °C. At the end of the incubation time aliquots of the samples wI re transferred to measuring bottles and oxygen consumption was recorded.

nominal concentrations in the incubation mixtures:
"STl571 F8": 7.7, 19.2, 48, 120 and 300 mg/L
3,5-dichlorophenol: 5, 12.2 and 30 mg/L

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The microbial inoculum was a preparation of activated sludge collected on the day of the test. The concentration of the microbial inoculum was adjusted to 4 g of dry weight per litre which gives a final amount of 1.6 g dry weight per litre. The inoculum was kept aerated before the begin of the test.

Study design

Test type:

flow-through

Water media type:

other: synthetic sewage solution

Total exposure duration:

3 h

Test conditions

Test temperature:

The incubation of the individual samples was started at intervals of 12-15 min and each sample was aerated for 3 hours at 18 °c.
At the end of the incubation time aliquots of the samples were transferred to measuring bottles and oxygen consumption was recorded.

pH:

The pH of the incubation mixtures after the 3 hour incubation was between 8.27 and 8.32 . The test substance did not influence the pH.

Results and discussion

Effect concentrations

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

162 mg/L

Basis for effect:

inhibition of total respiration

Details on results:

The test substance inhibited the respiration of the activatec sludge in a concentration dependent extent. The highest obtained inhibition was 63. %.
The dose - response curve of the test substance is presented in Figure 1.
The pH of the incubation mixtures after the 3 hour incubation was between 8.27 and 8.32 . The test substance did not influence the pH.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

The test results fulfilled the criteria for validity: • the respiration rates of the two control samples were within 15 % of each other. Actual values:± 0.06 %. • the EC50 of 3,5-dichlorophenol was in the accepted range of 5 to 30 mg/L. Actual EC50: 13.2

Conclusions:

The test substance inhibited the respiration of the activated sludge in a concentration dependent extent. The highest obtained inhibition was 63.3 %.