Formaldehyde, oligomeric reaction products with 4,4'-isopropylidenediphenol and m-phenylenebis (methylamine)

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

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 301 F (Ready Biodegradability: Manometric Respirometry Test)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

A mixed population of sewage treatment micro-organisms was obtained on 20 June 2016 from the final effluent stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK, which treats predominantly domestic sewage.

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Preliminary Solubility Work
Information provided by the Sponsor indicated that the water solubility of the test item was negilible. Therefore preliminary solubility/dispersibility work was performed in order to determine the most suitable method of preparation.

Test Item Preparation
A nominal amount of test item (10 mg) was adsorbed onto the surface of 100 mg of granular silica gel (Sigma Lot No STBC3040V) prior to dispersal in 350 mL of mineral medium with the aid of high shear mixing (approximately 7500 rpm, 15 minutes). The high shear mixer head was then washed with mineral media (50 mL) and the washings and silica gel/test item/mineral medium dispersion added to the test vessel prior to the addition of the inoculum (5 mL) and adjusting to a final volume of 500 mL to give a final concentration of 20 mg/L.

Reference Item Preparation
A reference item, aniline (C6H5NH2), was used to prepare the procedure control vessels. An initial stock solution of 1000 mg/L was prepared by dissolving the reference item directly in mineral medium with the aid of ultrasonication for approximately 10 minutes. An aliquot (50 mL) of this stock solution was diluted with mineral medium (445 mL) and the inoculum (5 mL), to give the test concentration of 100 mg/L. The volumetric flask containing the stock solution was inverted several times to ensure homogeneity.

Toxicity Control
A toxicity control, containing the test item and aniline, was prepared in order to assess any toxic effect of the test item on the sewage treatment micro-organisms used in the test.

An amount of test item (50 mg) was adsorbed onto the surface of 100 mg of granular silica gel (230-400 mesh Sigma Lot No. STBC3040V) prior to dispersal in 350 mL of mineral medium with the aid of high shear mixing (approximately 7500 rpm, 15 minutes). The high shear mixer head was then washed with mineral media (50 mL) and the washings and test item/silica gel/mineral medium dispersion were then added to the test vessel with an aliquot (50 mL) of the 1000 mg/L aniline stock solution (see Section 3.5.3). The volume was adjusted to 500 mL with mineral medium to give a final concentration of 20 mg test item/L plus 100 mg aniline/L.

Preparation of Test System
The following test preparations were prepared and inoculated in 500 mL bottles:
a) Three replicate bottles containing inoculated mineral medium to act as the inoculum control plus 100 mg silica gel.
b) Two replicate bottles containing inoculated mineral medium plus 100 mg silica gel and the reference item, aniline, at a concentration of 100 mg/L.
c) Three replicate bottles containing inoculated mineral medium plus 100 mg silica gel and the test item at a concentration of 20 mg/L.
d) Two replicate bottles containing inoculated mineral medium plus 100 mg silica gel the reference item, aniline, at a concentration of 100 mg/L and the test item at a concentration of 20 mg/L to act as toxicity control vessels.
Silica gel was added to the inoculum control and procedure control vessels in order to maintain consistency between these vessels and the test item vessels.
All vessels were inoculated with the prepared inoculum at a rate of 1% v/v.
On Day 0 the test and reference items were added and the pH of all vessels measured using a Hach HQ40d Flexi handheld meter, prior to the addition of the inoculum and the volume in all the vessels being adjusted to 500 mL by the addition of mineral medium.
All remaining inoculum control, test item, procedure control and toxicity control vessels were placed in a CES Multi-Channel Aerobic Respirometer.
The system consists of a sample flask sealed by a sensor head/CO2 trap immersed in a temperature controlled water bath. The samples were stirred for the duration of the test with a magnetically coupled stirrer.
As biodegradation progresses, the micro-organisms convert oxygen to carbon dioxide which is absorbed into the ethanolamine solution (50% v/v) causing a net reduction in gas pressure within the sample flask (see Figure 1). The pressure reduction triggers the electrolytic process, generating oxygen and restoring the pressure in the sample flask. The magnitude of the electrolyzing current and the duration of the current is proportional to the amount of oxygen supplied to the micro-organisms. The data generated from the respirometer’s own battery backed memory was collected on the hard disk drive of a non-dedicated computer.
The test was conducted in diffuse light at temperatures of between 22 and 24 ºC.
On Day 28, two inoculum control, one procedure control, two test item and one toxicity control vessel were sampled for pH.
The remaining vessels which were not sampled were discarded and are not reported. Additional replicate vessels were prepared and incubated in order that in the event of a leak in the test system a replicate vessel could be discarded without jeopardizing the integrity of the test.

Reference substance:

aniline

Key result

Parameter:

% degradation (O2 consumption)

Value:

6

Sampling time:

28 d

Details on results:

Validation Criteria
The mean BOD of the inoculated mineral medium (control) was 26.01 mg O2/L after 28 days and therefore satisfied the validation criterion given in the OECD Test Guidelines.
The pH of the inoculated test item vessels on Day 28 ranged from 7.6 and hence satisfied the validation criterion given in the OECD Test Guidelines.
The difference between extremes of replicate BOD values at the end of the test was less than 20% and therefore satisfied the validation criterion given in the OECD Test Guidelines.

Biodegradation
The test item attained 6.0% biodegradation after 28 days, calculated from the oxygen consumption values, and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301F.
The difference between extremes of replicate BOD values, at the end of the test was less than 20% and therefore satisfied the validation criterion given in the OECD Test Guidelines.
The test item attained 6% biodegradation after 28 days, calculated from the oxygen consumption values, and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301F.
Aniline (procedure control) attained 76% biodegradation after 14 days and 80% biodegradation after 28 days thereby confirming the suitability of the inoculum and test conditions.
The toxicity control attained 0% biodegradation after 14 days and 0% biodegradation after 28 days. In the initial test conducted at 100 mg/L statistically significant difference (P≥0.05) between the control and test item Day 14 BOD values were found. As there was no statistically significant difference (P≥0.05) between the control and test item Day 28 BOD values at 20 mg/L the test item was considered not to have had an adverse effect on the sewage treatment micro-organisms used in the test at 20 mg/L.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The test item attained 6% biodegradation after 28 days and therefore cannot be considered as readily biodegradable under the strict terms and conditions of OECD Guideline No. 301F.

Executive summary:

Introduction

The study was performed to assess the ready biodegradability of the test item in an aerobic aqueous media. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (1992) No. 301F, “Ready Biodegradability; Manometric Respirometry Test” referenced as method C.4-D of Commission Regulation (EC) No. 440/2008 and US EPA Fate, Transport, and Transformation Test Guidelines OCSPP 835.3110 (Paragraph (q)).

Methods

In an initial experiment conducted at a concentration of 100 mg/L, the toxicity control vessel, containing both the test item and sodium benzoate, attained less than 25% biodegradation after 14 days indicating that, under the strict terms and conditions of the OECD Guidelines, the test item would be classed as exhibiting inhibitory effects.

Therefore, following the recommendations of the Test Guidelines, in the definitive test, the test item, at a reduced concentration of 20 mg/L, was exposed to sewage treatment micro-organisms with mineral medium in sealed culture vessels in diffuse light at temperatures of between 22 and 24 ºC for 28 days.

The biodegradation of the test item was assessed by the measurement of daily oxygen consumption values on Days 0 to 28. Control solutions with inoculum and the reference item, aniline, together with a toxicity control were used for validation purposes.

Results

The test item attained 6% biodegradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301F.

Description of key information

The test item attained 6% biodegradation after 28 days and therefore cannot be considered as readily biodegradable under the strict terms and conditions of OECD Guideline No. 301F.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed