Hexan-4-olide

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Activated sludge from a domestic sewage treatment plant was used. The sludge used was collected at the domestic sewage treatment plant of Piracicaba, Águas do Mirante. It was collected and used on the same day of the test.
A moisture test was performed on the sludge and it presented 3 g L-1 of suspended solids.

Vehicle:

yes

Details on test solutions:

Water Milli-Q
Acetonitrile 99.9%
Bacteriological Peptone
Beef Extract
Urea 99%
Sodium Chloride 99%
Calcium chloride 98%
Magnesium Sulfate 98%
Potassium phosphate 99.3%
Deionized water
Copper sulphate penta hydrate
Water without chlorine

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

All chemicals used in the test were “analytical grade” or “for use in microbiology”.
Composition of nutrient solution (synthetic sewage):

Peptone 16.0 g
Beef extract 11.0 g
Urea 3.0 g
NaCl 0.7 g
CaCl2 *2H2O 0.4 g
MgSO4 *7H2O 0.2 g
K2HPO4 2.8 g
Deionised water 1000 mL

The pH of the solutions was 7.52. The medium was prepared and stored in the dark at a temperature of 4°C.

Test type:

not specified

Water media type:

freshwater

Total exposure duration:

3 h

Test temperature:

20

pH:

7.52

Details on test conditions:

The study was performed in a closed system with aeration. In the control vessels, 16 mL of nutrient solution was mixed with 234 mL of water. The positive control and the test vessels were prepared by adding the appropriate amount of positive control solution respectively test item into the test vessel, adding 16 mL nutrient solution and water to give 250 mL. Then, 250 mL inoculum was added in ten minutes intervals. After addition of the inoculums, the flasks were closed immediately and the mixtures were stirred with aeration.
After three hours the contents were poured into a tube of approximately 50 mL and the respiration rate was determined by measuring the O2 concentration over a ten minutes period. The following vials were measured equally at ten minutes intervals.

Reference substance (positive control):

yes

Key result

Duration:

3 h

Dose descriptor:

other: Effective Concentration

Effect conc.:

ca. 51.6 mg/L

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

other: O2-Consumption, Inhibition

Details on results:

The test substance was solubilized in water because of its solubility. As there were no statistically significant toxic effects at the highest concentration (1000 mg L-1), no further testing was required at higher or lower concentrations as outlined in OECD 209, 2010.

Results with reference substance (positive control):

Average oxygen uptake rate was 25.10 mg L-1 h. The variation of OD consumption in the controls was 27.78% which are far below the recommended upper limit of 30%.

Validity criteria fulfilled:

yes

Conclusions:

There were no statistically significant toxic effects at the highest concentration (1000 mg L-1).

Description of key information

The test substance was solubilized in water because of its solubility.As there were no statistically significant toxic effects at the highest concentration (1000 mg L^-1), no further testing was required at higher or lower concentrations as outlined in OECD 209, 2010.