2-methyl-3-(p-tolyl)propionaldehyde

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 12 April, 2021 to June 24, 2021

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2021

Report date:

2021

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

1992

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

2-methyl-3-(p-tolyl)propionaldehyde

EC Number:

255-410-4

EC Name:

2-methyl-3-(p-tolyl)propionaldehyde

Cas Number:

41496-43-9

Molecular formula:

C11H14O

IUPAC Name:

2-methyl-3-(4-methylphenyl)propanal

Test material form:

liquid

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (Bois-de-Bay, Satigny, Switzerland) was used.
The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.

Duration of test (contact time):

60 d

Initial test substance concentration

Initial conc.:

30 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Preparation of the flasks
Test substance samples (7.65 mg, corresponding to 30.0 mg/I in 255 ml of test medium) are weighed in small aluminium boats and added directly to the test flasks of the Oxitop. For reference substance samples 12.75 mg (corresponding to 50.0 mg/I in 255 ml of test medium) are weighed in small aluminium boats and added directly to the test flasks of the Oxitop.
Flasks are filled with 250 ml of mineral medium. Samples of test or reference substance are added . Then 5.00 ml of suspended sludge diluted to a concentration of 1.53 g/1 dry matter is added. Except when the test substance has an acid or alkaline character, the pH of each flask is not measured but assumed to be the same as the mineral medium (see 3.5.), in order not to remove any floating undissolved test substance from the test medium by dipping a glass electrode in it. Neutral test substances, even sodium benzoate, were shown not to affect the pH of the medium by more than 0.1 pH unit.
Two sodium hydroxide pellets are placed in the quivers on top of the bottle, and the flasks are closed tightly with the measuring heads. The flasks are allowed to equilibrate to the test temperature. The measurement is started by programming the measuring unit of the Oxitop test flasks, and the test flasks are placed in the temperature controlled cupboard of the Oxitop system. After temperature equilibration, the controller of the instrument starts the data acquisition (time zero of the experiment).

Everyday the oxygen consumption of each flask is recorded and correct temperature and stirring are checked. At the end of the test period (normally 28 days), the pH of each flask is measured again.

An optional toxicity control as suggested by OECD guideline 301 F was not performed. The validity of the study is not adversely affected.

Reference substance

Reference substance:

benzoic acid, sodium salt

Remarks:

Sodium benzoate (Sigma-Aldrich, Switzerland, Art. No. 109169), purity : min. 99.0%.

Results and discussion

Test performance:

Everyday the oxygen consumption of each flask is recorded and correct temperature and stirring are checked.
At the end of the test period (normally 28 days), the pH of each flask is measured again.

% Degradation

% Degradation 1

Key result

Parameter:

% degradation (O2 consumption)

Value:

81

Sampling time:

28 d

% Degradation 2

Parameter:

% degradation (O2 consumption)

Value:

91

Sampling time:

60 d

Details on results:

Oxygen uptakes, as read on the Oxitop controller, are corrected to account for the small
differences between actual and nominal concentrations of test and reference
substances.
Degradation of sodium benzoate exceeded 40% after 7 days and 65% after 14 days: the activity of the inoculum was thus verified (validity criterion).
The repeatability validity criterion (not more than 20% difference between replicates) is fulfilled. Therefore, the test is considered valid.

BOD5 / COD results

Results with reference substance:

Degradation of sodium benzoate exceeded 40% after 7 days and 65% after 14 days: the activity of the inoculum was thus verified (validity criterion).
The repeatability validity criterion (not more than 20% difference between replicates) is fulfilled. Therefore, the test is considered valid.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

The Ready Biodegradability of 2-methyl-3-(p-tolyl)propionaldehyde was determined by the Manometric Respirometry Test.
2-methyl-3-(p-tolyl)propionaldehyde undergoes 81 % biodegradation after 28 days and 91 % biodegradation after 60 days in the test conditions. The 10-day window criterion is not fulfilled (11 % on day 5 and 44% on day 15).
2-methyl-3-(p-tolyl)propionaldehyde did not inhibit the intrinsic respiration of the inoculum during the study and can be considered to be non-toxic to the inoculum at the test concentration.
Thus, according to this test, 2-methyl-3-(p-tolyl)propionaldehyde reached the pass level for Ready Biodegradability but failing the 10-day window criterion.

Executive summary:

The Ready Biodegradability of 2-methyl-3-(p-tolyl)propionaldehyde was determined by the Manometric Respirometry Test.
2-methyl-3-(p-tolyl)propionaldehyde undergoes 81 % biodegradation after 28 days and 91 %  biodegradation after 60 days in the test conditions. The 10-day window criterion is not fulfilled (11 % on day 5 and 44% on day 15).
2-methyl-3-(p-tolyl)propionaldehyde did not inhibit the intrinsic respiration of the inoculum during the study and can be considered to be non-toxic to the inoculum at the test concentration.
Thus, according to this test, 2-methyl-3-(p-tolyl)propionaldehyde reached the pass level for Ready Biodegradability but failing the 10-day window criterion.