Methyl benzoylformate

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

Deviations:

yes

Remarks:

Exceeding the test temperature range of 20 ± 2 °C with 0.6°C (highest temperature was 22.6°C). This deviation was considered not to effect the validity of the test result.

Principles of method if other than guideline:

One deviation from the study plan and the test guidelines were realized:
1. Exceeding the test temperature range of 20 ± 2 °C with 0.6°C (highest temperature was 22.6°C). However, an influence to the results of this study can be excluded.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
Application of the test substance: Direct addition by initial weight into the test flasks. The test substance was weighed in the required amounts for the test concentrations directly to the test vessels. The test substance was added in the required amounts according to the test concentrations directly to the test vessels with about 234 mL deionized water

Test organisms (species):

activated sludge, domestic

Details on inoculum:

Age: 1 day
Origin: aeration tank of the wastewater treatment plant of Mannheim, Germany
Collection of the test system: 18 Aug 2014
Arrival in the test facility: 18 Aug 2014
After arrival of the activated sludge suspension in the test facility the suspension was sieved with a fine woven mesh (mesh size about 1 mm). This suspension was pre-aerated over night at room temperature. At the next day the sludge suspension was washed once with drinking water and the suspension was adjusted to 3 g/L Dw.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20 ± 2°C

pH:

7.4

Dissolved oxygen:

Oxygen concentration during aeration: > 2 mg/L
Oxygen concentration immediately before measurement: > 7 mg/L

Nominal and measured concentrations:

1000, 500, 250, 125, 62.5 mg/L as nominal concentration based on test substance without correction of purity and blank controls.
100, 10, 1 mg/L as nominal concentration based on reference substance.

Details on test conditions:

TEST SYSTEM
- Test vessel: Glas-beakers (nominal volume 1L)
- Test volume: 500 mL
- Synthetic medium: 16 mL/test vessel of 100-fold concentrated OECD medium
- Aeration:
- No. of organisms per vessel:
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per reference substance (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: OECD medium

OTHER TEST CONDITIONS
- Adjustment of pH: No (An adjustment was not necessary)
- Light intensity: Because the test substance is light sensitive the weighing in the test vessels, the incubation and the measurement of oxygen consumption were performed at red light.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :

TEST CONCENTRATIONS
- Spacing factor for test concentrations: According to the test guidelines, at least 5 concentrations in a geometric series with a separation factor of ≤ 3.2 should be used, preferably encompassing the range from 10 – 80% inhibition
- Justification for using less concentrations than requested by guideline:

Reference substance (positive control):

yes

Remarks:

3,5 dichlorophenol

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

390 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

540 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

other: EC80

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

The results in this study were consistent with the validity criteria with one exception. The mean oxygen uptake in the blank controls was lower than 20 mg/g*h (10 mg/g*h). Because the reference substance shows an EC50 in the specified range (usual range of EC50 of the last 20 values in the laboratory was 6.0 - 14.1 mg/L) and the measured oxygen uptake from the test substance concentrations showed a good curve progression the study is classified as valid. The used activated sludge which was collected from the same waste water treatment plant showed a maximum oxygen consumption of 36.8 mg/g*h and minimum oxygen consumption of 10.2 mg/g*h of the last 20 measurements. For this the study is classified as valid.

Results with reference substance (positive control):

In order to verify that the microorganisms are responding normally to toxic stress, tests with a reference substance are conducted according to OECD 209 guideline. The results from the reference substance test are compared to EC50 values published in OECD 209 guideline, which represent the typical response range.
According to the test guideline OECD 209 the EC50 values of the reference substance 3,5-dichlorophenol should be in the range of 2-25 mg/L after 3 hours of incubation.
The EC50 of the reference substance 3,5-dichlorophenol was in the range of 2-25 mg/L in 3 hours.
These results indicate that the microorganisms are responding normally to toxicant stress.

Validity criteria fulfilled:

yes

Conclusions:

The inhibition of the degradation activity of activated sludge is not anticipated when introduced to biological treatment plants in appropriate low concentrations.

Executive summary:

In this guideline (OECD 209) study conducted with GLP certification, the nominal LC50 to microorganisms of the test material (EC 239-263-3) was determined be >1000 mg/l. The test was carried out using a washed sewerage sludge taken from a municipal STP. Inhibition of biotic degradation by microorganisms in biological treatment plants is not expected at low concentrations.

Description of key information

 Study carried out according to guideline and with GLP compliance. 

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

EC10 or NOEC for microorganisms:

390 mg/L

Additional information

A GLP guideline study according OECD 209 has been conducted (BASF SE 2015). After 3 h following results were found in the activated sludge respiration inhibition test:

EC10 = 390 mg/L, EC20 = 540 mg/L, EC50 = oder >1000 mg/L, EC80 = oder >1000 mg/L

The results in this study were consistent with the validity criteria with one exception. The mean oxygen uptake in the blank controls was lower than 20 mg/g*h (10 mg/g*h). Because the reference substance shows an EC50 in the specified range (usual range of EC50 of the last 20 values in the laboratory was 6.0 - 14.1 mg/L) and the measured oxygen uptake from the test substance concentrations showed a good curve progression the study is classified as valid. The used activated sludge which was collected from the same waste water treatment plant showed a maximum oxygen consumption of 36.8 mg/g*h and minimum oxygen consumption of 10.2 mg/g*h of the last 20 measurements. For this the study is classified as valid.

Therefore, the inhibition of the degradation activity of activated sludge is not anticipated when introduced to biological treatment plants in appropriate low concentrations.