Diphenylamine

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

June 1996

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

not specified

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

other: secondary effluent from a waste water treatment plant

Duration of test (contact time):

28 d

Initial conc.:

1.9 mg/L

Based on:

not specified

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral medium
- Test temperature: 20°C
- Suspended solids concentration: 0.5 ml/l
- Continuous darkness: yes

TEST SYSTEM
- Method used to create aerobic conditions: aerated medium (9 mg O2/l)

SAMPLING
- Sampling frequency: 0, 3, 9, 14, 21 & 28 d

Reference substance:

not specified

Parameter:

% degradation (O2 consumption)

Value:

26

Remarks on result:

other: Indications on sampling time were not provided

Validity criteria fulfilled:

not specified

Remarks:

detailed results not given

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Under the conditions of the study, diphenylamine may be characterised as not readily biodegradable because the measured biodegradation 26 % is lower than the pass level of 60 %

Executive summary:

The ready biodegradability of diphenylamine was tested in the Closed Bottle Test (OECD 1992). The biodegradability is determined by measuring the oxygen consumption in inoculated test bottles. Diphenylamine was added directly to an aerated ( - 9 mg 02/I) mineral medium inoculated with secondary effluent (0.5 ml/l) from Ussered WWTP, and stirred magnetically at 600 rpm for 4 h.

The initial concentration of the test substance was 1.9 mg/l. The test bottles were placed in the dark at a constant temperature of 20 +/- 1 °C. A triplicate set of test bottles was sacrificed at the start of the test and after 3, 9, 14, 21 and 28 d for oxygen measurements.

The biodegradability of diphenylamine was expressed as the biological oxygen demand (BOD) in percent of the theoretical oxygen demand (ThOD) for a complete mineralisation of the test substance.

 

Under the conditions of the study, diphenylamine may be characterised as not readily biodegradable because the measured biodegradation 26 % is lower than the pass level of 60 %

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Guideline study reported by an authoritative secondary source

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

yes

Remarks:

initial concentrations of nitrate unknown

GLP compliance:

yes (incl. QA statement)

Remarks:

certified laboratory

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

not specified

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral salts
- Test temperature: 20-24 °C
- Suspended solids concentration: 4.8 g/l
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5-liter glass vessels

SAMPLING
- Sampling frequency: day 4, 7, 10, 14, 21 & 28

CONTROL AND BLANK SYSTEM
- Inoculum blank: 5 ml microbial inoculum + 4995 ml mineral medium
- Abiotic sterile control: 5000 ml mineral medium
- Toxicity control: 2 ml microbial inoculum + 20 ml reference item + 1978 ml mineral medium

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

0

Remarks on result:

other: Indications on sampling time were not provided

Results with reference substance:

% degradation
day 4: 62.57
day 7: 69.16
day 10: 67.37
day 14: 79.64
day 21: 80.54
day 28: 51.80

Net mean oxygen depletion values (mg O2/L) on the whole test period: 0 mg/L

Validity criteria fulfilled:

yes

Remarks:

reference substance readily biodegradable; activated sludge viable

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Under the conditions of the Closed Bottle test diphenylamine was not readily biodegradable, since no biodegradation was observed after 28 days.
Under the conditions of the toxicity control diphenylamine did not appear to exhibit any inhibitory effect on the microbial inoculum as a mean biodegradation of 44.57 % was observed after 28 days.

Reference 3

Endpoint:

biodegradation in water: screening tests

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

June 1996

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

Deviations:

yes

Remarks:

only one sampling source instead of 10 for the inoculum

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: Usserod waste water treatment plant
- Concentration of sludge: 5 g suspended solids (dw)/l

Duration of test (contact time):

28 d

Initial conc.:

30 mg/L

Based on:

not specified

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral medium
- Test temperature: 20 °C
- pH adjusted: yes/no
- Suspended solids concentration: 5.0 g dw/l
- Continuous darkness: yes

TEST SYSTEM
- Method used to create aerobic conditions: aerated medium
- Measuring equipment: BOD meter
- Details of trap for CO2 and volatile organics if used: KOH absorber placed in the BOD meter

Reference substance:

not specified

Parameter:

% degradation (O2 consumption)

Value:

38

Sampling time:

28 d

Results with reference substance:

no data

Diphenylamine inhibited the activity in the activated sludge during the last 2 weeks of the test period

Validity criteria fulfilled:

not specified

Remarks:

detailed results not given

Interpretation of results:

inherently biodegradable

Conclusions:

Under the conditions of the study, diphenylamine is regarded as inherently biodegradable because the measured biodegradation of 38 % ThOD is higher than the pass level of 20 %

Executive summary:

The inherent biodegradability of diphenylamine was tested according to the procedures described for the modified MIT1 II test (OECD 1992). The guideline prescribes the use of a mixed inoculum obtained from at least 10 sampling sources, but the inoculum used in the present test originated from only Usserod WWTP. The biodegradation is determined from the oxygen consumption in closed, inoculated test vessels (BOD-meters).

In this test, the produced CO, is trapped in a KOH absorber placed in the BOD-meter. The consumption of 0, is calculated from the reduction of air pressure. Diphenylamine was added directly to an aerated mineral medium inoculated with activated sludge (5.0 g suspended solids (d.w.)/l) and dispensed into the BOD-meters.

The initial test concentration of the test substance was 30 mg/l. The test bottles were placed in the dark at a constant temperature of 20 +/- 1 °C. The oxygen consumption was determined by recording the reduction of pressure displayed on the BOD-meters at appropriate time intervals during 28 d.

 

The result of the Mod. MITI (II) Test resulted in a degradation of 38 % but may have been influenced by toxic effects as the substance concentration in this test was 30 mg/l. A test on inhibition of respiration according to OECD 209 showed an EC50 of 18.7 mg/l.

Description of key information

2 key studies from the same publication have been selected (Murin et al., 1997). Murin et al. (1997) reported a biodegradation of 26 % in a Closed Bottle Test (OECD 301 D, 1992) and 38 % in a Mod. MITI (II) Test after 28 days.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable, not fulfilling specific criteria

Type of water:

freshwater

Additional information

The result of the Mod. MITI (II) Test resulted in a degradation of only 38 % but may have been influenced by toxic effects as the substance concentration in this test was 30 mg/l. Indeed, a test on inhibition of respiration according to OECD 209 showed an EC50 of 18.7 mg/l. Another study tested a lower non toxic concentration also showed a limited biodegradability.