Methyl benzoate

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

Study period:

1992-06-15 to 1992-06-17

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

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Details on sampling:

not applicable

Vehicle:

no

Test organisms (species):

activated sludge

Details on inoculum:

- Source: Activated sludge from a laboratory wastewater treatment plant
- Preparation of inoculum for exposure: not reported
- Pretreatment: no pretreatment
- Initial biomass concentration: 6 g dry matter/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

not applicable

Hardness:

not reported

Test temperature:

not reported

pH:

not reported

Dissolved oxygen:

not reported

Salinity:

not applicable

Nominal and measured concentrations:

Nominal: 560, 1000, 1800, 3200, 5600 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: not reported
- Type (delete if not applicable): not reported
- Material, size, headspace, fill volume: not reported
- Aeration: not reported

- No. of vessels per concentration (replicates): not reported
- No. of vessels per control (replicates): not reported

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: not reported
- Total organic carbon: not reported
- Particulate matter: not reported
- Metals: not reported
- Pesticides: not reported
- Chlorine: not reported
- Alkalinity: not reported
- Ca/mg ratio: not reported
- Conductivity: not reported
- Culture medium different from test medium: not reported

OTHER TEST CONDITIONS
- Adjustment of pH: not reported
- Photoperiod: not reported
- Light intensity: not reported

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : respiration rate of sewage sludge

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

815 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

The inhibition of the respiration of the sludge was between 30% at the lowest test concentration of 560 mg/L and 92.3% at the highest test concentration of 5600 mg/L

Results with reference substance (positive control):

The study results with the reference substance are not reported.

Validity criteria fulfilled:

yes

Conclusions:

The substance inhibited the microbial activity of sewage sludge and the EC50 value was 815 mg/L after 3 hours.

Executive summary:

The toxicity of the substance methyl benzoate to bacteria in sewage sludge was tested under GLP conditions in a static system in accordance with OECD guideline No 209. The respiration rate of activated sludge from a laboratory wastewater treatment plant was determined at a sludge concentration of 6 g dry matter/L in the absence of test substance. Then the corresponding respiration rate of the sludge exposed to nominal test concentrations of 560, 1000, 1800, 3200 and 5600 mg/L for 3 hours was determined and compared to the respiration rate of untreated sludge. The microbial activity of the sludge was inhibited at all test concentrations and reduced by 30% to 92.3%. The EC50 value for inhibition was 815 mg/L after 3 hours. The sensitivity of the activated sludge was tested and confirmed with the reference substance 3,5 -dichlorophenole.

Description of key information

The 3-hour EC50 value for inhibition of respiration of activated sludge was 815 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

815 mg/L

Additional information

The inhibition of respiration of activated sludge following three hours of exposure to methyl benzoate at a series of test concentrations was determined in a valid study in accordance with OECD TG 209. Activated sludge was taken from a laboratory sewage treatment plant according to OECD. The EC50 value for inhibition of the respiration rate of activated sludge was 815 mg/L after 3 hours of exposure.