Formaldehyde, oligomeric reaction products with aniline

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-GLP study carried out in accordance with an OECD Guideline.

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)

GLP compliance:

no

Inoculum or test system:

activated sludge, adapted

Details on inoculum:

Activated sludge from the BASF wastewater treatment plant (1g total solids/litre)

Duration of test (contact time):

27 d

Initial conc.:

389 mg/L

Value:

48

Sampling time:

7 d

Value:

95

Sampling time:

14 d

Value:

97

Sampling time:

21 d

The study was based on OECD Guideline 302B and measured the removal of DOC to determine the degree of biodegradation. Therefore, no BOD was determined.

Interpretation of results:

inherently biodegradable

Conclusions:

MDA is inherently biodegradable.

Reference 2

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Carried out according to OECD Guideline.

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

Fresh activated, non-adapted municipal sewage. Temperature of incubation 21 +/- 1°C

Duration of test (contact time):

28 d

Initial conc.:

30 mg/L

Based on:

test mat.

Parameter:

other: BOD

Value:

43

Sampling time:

28 d

Details on results:

43% after 28 days

Parameter:

BOD5

Value:

ca. 1 other: mg/l

Results with reference substance:

77% biodegradation of aniline after 4 days.

Under these test conditions, 4,4'-MDA showed some degradation (43%) after 28 days.

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Carried out in accordance with an OECD Guideline.

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD 303A (1981)

Deviations:

yes

Remarks:

For the determination of DOC, the solution was filtered through a 0.45 micrometer filter.

Principles of method if other than guideline:

Bioelemination by aerobic micro-organisms in a continuously operated test system simulating the activated sludge process.

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, adapted

Details on inoculum:

Activated sludge produced in the test apparatus from a mixed inoculum obtained from;
- bacteria collected from the secondary effluent of the sewage treatment plant of CH-4153 Reinach
- water from the Rhine collected in CH-4000 Basle
- a suspension of garden soil collected in CH-4000 Basle

Duration of test (contact time):

34 d

Parameter followed for biodegradation estimation:

DOC removal

Parameter:

% degradation (DOC removal)

Value:

6.5

Sampling time:

25 d

Remarks on result:

other: 25 d adaption time, contact time was 34 d

Details on results:

The average elimination of MDA, measured by DOC analysis, was 6.5%.

Parameter:

BOD5

Value:

other: unknown

An adaption time of 25 days is not sufficient and results suggest that MDA is not readily biogradeable. Furthermore, the test substance does not fulfill the conditions specified for inherent biodegradability. The study was based on OECD Guideline 303A and measured the removal of DOC to determine the degree of biodegradation. Therefore, no BOD was determined.

Reference 4

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:

other: A GLP study carried out in accordance with an OECD Guideline.

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Municipal activated sludge from the wastewater treatment plant Mannheim/Baden Württemberg (Germany) was collected on 06 July 2007 from the aeration tank of the plant and aerated in the laboratory until further use. A suitable aliquot of the activated sludge suspension was sieved using a finely woven mesh with a mesh size of about 1 mm. After settling, the supernatant was discarded and the sludge suspension was filled up with tap water. This washing procedure was repeated three times. The suspended solids concentration of the resulting sludge suspension will be determined, and a suitable portion was used to inoculate the mineral medium at a final suspended solids concentration of 30 mg/L. The inoculum was pre-adapted to the test conditions by stirring and aeration with CO2-free air at the test temperature for about five days. After this adaptation period, the inoculated mineral medium (1.5 L) was dispensed into the various test vessels.

Reason for the choice of the biological test system: The test guideline recommends the usage of activated sludge from a wastewater treatment plant, treating municipal sewage.

Duration of test (contact time):

28 d

Initial conc.:

ca. 500 µg/L

Based on:

other: corresponding to a total radioactivity of about 11 microCi in the test assay.

Parameter followed for biodegradation estimation:

radiochem. meas.

Details on study design:

Test temperature 22+/-2 degree C

Reference substance:

aniline

Parameter:

% degradation (CO2 evolution)

Value:

46

St. dev.:

3.96

Sampling time:

28 d

Details on results:

46% biodegradation after exposure of 28 days
53% (standard deviation +/-3.54%) after exposure of 63 days.

Results with reference substance:

66% degradation after 14 days (%CO2/ThCO2)

The test substance was partly or moderately biodegradable. The study was based on OECD Guideline 301B and measured the evolution of CO2 to determine the degree of biodegradation. Therefore, no BOD was determined.

Validity criteria fulfilled:

yes

Interpretation of results:

other: moderately biodegradable

Description of key information

For ready biodegradability, the key study is Schwarz (2009) which is fully documented with a GLP certificate. Caspers et al (1986) and BASF (1988) are key studies, of similar quality, with respect to the determination of inherent biodegradation. The Baumann (1986) coupled units (simulation test) study is a good quality key study.
4,4'-MDA is considered to be inherently biodegradable in industrial wastewater treatment plants (wwtps) only.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Additional information

Justification on read-across of data for the 4,4´-isomer of MDA for oligomeric MDA in the scope of REACH.

Oligomeric MDA (oMDA) is produced by a condensation reaction between aniline and formaldehyde. The main component of the crude product is 4,4’-MDA, which makes up 46 to 65%. Further, the crude product contains minor amounts of methylene-2,4’-dianiline and traces of methylene-2,2’-dianiline. The other main component is a mixture of higher oligomers.

The general molecular formula is:

 H₂N-C₆H₄-[H₂N-C₆H₄]_m-C₆H₄-NH₂

The higher oligomers include mainly 3-ring (m=1; product of 3 aniline + 2 formaldehyde) together with other higher number ring types (m=4-7; 4 to 7 aniline with 3-6 formaldehyde) as shown in the table below.

 Following nomenclature for the isoformes are defined:

1) CAS name: Benzenamine, 4,4'-methylenebis- (mono constituent substance), CAS number: 101-77-9. EC name: 4,4'-methylenedianiline, EC number:202-974-4

2) CAS name: Formaldehyde, polymer with benzenamine (UVCB), CAS number 25214-70-4. EC name: Formaldehyde, oligomeric reaction products with aniline, EC number: 500-036-1.

Concentration ranges of MDA-isoforms [%]:

CONTENT	4,4’-MDA	Oligomeric MDA
4,4’-MDA	75-100	46-65
2,4’-MDA	0-20	0.8-1.4
2,2’-MDA	0-5	<0.1
Formaldehyde, oligomeric reaction products with aniline	0-15	3- to 7-ring isomers concentrations shown below
3-ring isomers	No data	22-28
4-ring isomers	No data	12-14
5-ring isomers	No data	6-8
6-ring isomers	No data	3-5
7-ring isomers	No data	1-3

2,4'-methylenedianiline: CAS number 1208-52-2, EC number 214-900-8

2,2'-methylenedianiline: CAS number 6582-52-1, EC number 229-512-4

 

Comparison of physico-chemical properties of MDA-isoforms:

Property	4,4'-MDA	oligomeric MDA
Melting range	83 - 92°C	30 - 70°C
MW [g/mol]	198.26	233 (average)
water solubility [g/l]	1.01 (at 25°C)	0.36-1.22 (at 20°C)
logPow(at 25°C)	1.55	1.3 - 2.5
Vapor pressure [hPa]	0.00025 Pa at 25°C	<0.000001hPa at 20°C

 

The higher oligomers are substantially less soluble than the diamine (4,4’-MDA: 1.25 g/l; 3-core-MDA: 42.5 mg/l) (EU RAR, 2001) and are emitted into the environment in much lower amounts than the diamines. If waste water is monitored, only the 4,4’-MDA is detected. It is unlikely the higher ring oligomers will significantly raise the total emissions and are therefore of less importance in any exposure assessment. Therefore as 4,4’-MDA is the main constituent of both isoforms, efate properties of the incompletely tested oMDA can be extrapolated from this isomer by means of a worst case consideration.

Biodegradation

Results from the ready biodegradation studies clearly indicate that MDA is not readily biodegradable. In the Schwarz (2009) study 0.5mg/l radiolabeled MDA was used in the OECD 301B test. At this very low concentration of test substance and where inhibition of the microbial population would not be expected, only 46% biodegradation was recorded after 28 days exposure.

In the Caspers et al (1986) study using activated sludge from a predominantly municipal source, the inherent biodegradation of MDA was found to be only 43% after 28 days. In a further inherent biodegradation study (BASF, 1988), using activated sludge from an industrial wastewater treatment plant, MDA was found to undergo 95% degradation after 14 days, and 97% after 21 days.

A Coupled Units Test (OECD 303A, Baumann 1986) with activated sludge produced from a mixed inoculum (secondary effluent, Rhine-water, suspension of garden soil) with an adaption phase of 25 days indicated only 6.5% biodegradation after 34 days.

These results clearly show that 4,4'-MDA is not readily biodegradable and fulfills the criteria for inherent biodegradation only if an adapted industrial inoculum is used. From the Coupled Units Test it can be deduced that an adaptation time of 25 days is not sufficient. Therefore 4,4'-MDA has to be considered as inherently biodegradable in industrial wastewater treatment plants (wwtps) only. Degradation in municipal wwtps cannot be deduced from these results.

On the basis of available biodegradation tests it is not possible to conclude that the substance is biodegraded under environmental conditions.