N-1-naphthylaniline

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:

weight of evidence

Study period:

10.01. 1990 to 07.02.1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

GLP study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

modified according to EU ring test: Assessment of Biodegradability of Chemicals in Water by manometric respirometry (DG X1 283/82 Rev. 5)

Deviations:

yes

Remarks:

- no determination of stability, homogeneity and concentration of test substance in test medium

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): 10 L laboratory facility (Wupperverband)
- Pretreatment: none
- Concentration of sludge: 30 mg/L TS

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Test temperature: 20 +/- 1°C
- pH: no data

TEST SYSTEM
- Culturing apparatus: closed respirometer
- Number of culture flasks/concentration: 1
- Measuring equipment: respirometer

SAMPLING
- Sampling frequency: once
- Sampling method: determination of theoretical oxygen demand

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: yes, aniline

Reference substance:

aniline

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Details on results:

theoretical oxygen demand: 2700 mg/g

Parameter:

COD

Value:

2 700 mg O2/g test mat.

Results with reference substance:

degradation of 69% after 28 d

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

no data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Data from published data base (performed according to guideline)

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

- Concentration of sludge: 30 ppm
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): sludge sampling at 10 places in Japan (Fukogawa city sewage plant, Fukashiba industry sewage plant, Nakahama city sewage plant, Ochiai city sewage plant, Kitakami river, Shinano river, Yoshino river, Lake Biwa, Hiroshima bay, Dookai bay) in March, June, September and December in every year. City sewage: Returned sludge of sewage. Rivers, lakes and sea: surface water and surface soil in contact with the atmosphere were collected.
- Laboratory culture: about 30 min after ceasing aeration to the sludge mixture, supernatan corresponding to 1/3 of the whole volume was removed. The equal volume of dechlorination water was added to the remaining portion and aerated again, followed by addition of synthetic sewage (glucose, peptone, monopotassium phosphate, pH 7 +/- 1). The procedure was repeated once every day. 25 +/- 2°C.
- Water filtered: no

Duration of test (contact time):

14 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

other: BOD, TOC removal and analysis of test substance

Details on study design:

TEST CONDITIONS
- Composition of medium: 3 mL of solution A, B and C, respectively, prescribed in JIS K 0102-1986-21, made up to 1000 ml with purified water
- Additional substrate: no
- Test temperature: 25 +/- 1°C
- pH: 7.0
- pH adjusted: yes
- Aeration of dilution water: yes
- Suspended solids concentration: 30 to 100 mg/L


TEST SYSTEM
- Culturing apparatus: 300 mL closed system oxygen consumption measuring apparatus (Coulometer: Ohkura Electric Co., Ltd.)
- Number of culture flasks/concentration: 1
- Measuring equipment: Coulometer: Ohkura Electric Co., Ltd.


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: yes
- Toxicity control: yes

Reference substance:

aniline

Remarks:

guaranteed reagent, Showa Chemicals Inc.

Parameter:

other: BOD, TOC removal and analysis of test substance

Value:

0

Sampling time:

14 d

Results not further specified.

Validity criteria fulfilled:

not specified

Interpretation of results:

under test conditions no biodegradation observed

Reference 3

Endpoint:

biodegradation in water: screening test, other

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well-documented publication which meets basic scientific principles

Qualifier:

no guideline followed

Principles of method if other than guideline:

10d biodegradation study using samples of lake water and primary sewage effluent (US-EPA method)

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

other: lake water and primary sewage effluent

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): lake water from Oneida Lake (US), sewage from a local domestic waste-water treatment plant
- Preparation of inoculum for exposure: supplementation with either nutrient broth or yeast extract at 500 mg/mL (partly)
- Initial cell/biomass concentration: Prior to starting the biodegradation studies, the microbial population in the water was determined using the standard serial dilution and plating techniques. The microbial population ranged from 1500 to 2200 CFU/mL.

Duration of test (contact time):

10 d

Initial conc.:

2 other: ppm

Based on:

test mat.

Parameter followed for biodegradation estimation:

radiochem. meas.

Details on study design:

TEST CONDITIONS
- Composition of medium: water
- Additional substrate: some samples were supplemented with either nutrient broth or yeast extract (500 mg/mL)
- Test temperature: 21 +/- 1°C
- pH: no data
- pH adjusted: no

TEST SYSTEM
- Culturing apparatus: Erlenmeyer flasks stoppered with foam plugs
- Number of culture flasks/concentration: not specified
- Measuring equipment: HPLC, liquid scintillation counting, by acidifying with HCl
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: The water samples (50-mL) were incubated with 2 ppm 14 of C-PNA in the biometer flask and 0.1 N KOH was used as the CO2-trapping solution in the side arm.

SAMPLING
- Sampling frequency: 2 mL aliquots were removed periodically

CONTROL AND BLANK SYSTEM
- Inoculum blank: no data
- Abiotic sterile control: yes

Parameter:

% degradation (CO2 evolution)

Value:

50

Sampling time:

5 d

Remarks on result:

other: sewage

Parameter:

% degradation (CO2 evolution)

Value:

>= 75

Sampling time:

2 d

Remarks on result:

other: sewage supplemented

Key result

Parameter:

% degradation (CO2 evolution)

Value:

100

Sampling time:

18 d

Remarks on result:

other: sewage supplemented

Parameter:

% degradation (CO2 evolution)

Value:

50

Sampling time:

10 d

Remarks on result:

other: lake water

Key result

Parameter:

% degradation (CO2 evolution)

Value:

>= 90

Sampling time:

18 d

Remarks on result:

other: lake water

Details on results:

Unsupplemented sewage:
Assuming first-oder kinetics for the degradation, the rate constant and half-life were 6.8 x 10e-3 per hour and 4.2 days, respectively. Thereafter, degradation continued slower and only 3% of the original chemical remained after 18 d. Sterile sewage: <20% degradation within 18 d.

Supplemented sewage:
half-life: 1.2 d, no PNA could be detected after 18 d. Rate constant: 2.4 x 10e-2 per hour.

Lake water:
Degradation was slower than in sewage effluent. Rate constant: 7.9 x 10e-3 per hour, half-life: 7.2 d

Degradation products:
The presence of a major metabolite(s) was shown (95% of extractable radioactivity after 10 d, 5% as unmetabolized PNA). These metabolites were tentatively identified by GC-MS as dihydroxy derivative of PNA (m/e 252) and N-acetyl PNA (m/e 262).
The results provide evidence that PNA undergoes hydroxylation and ring cleavage (phenyl moiety and/or at naphtyl-1-14C position). It is speculated that PNA metabolism involves hydroxylation at a position ortho to the amino group followed by ring cleavage at this position.

Validity criteria fulfilled:

not applicable

Interpretation of results:

inherently biodegradable

Conclusions:

The results of this study demonstrate that PNA is extensively degraded to the extent of ring cleavage by the action of aquatic microorganisms. Addition of an external carbon and energy source (yeast extract, nutrient broth) appears to significantly increase the rate of biodegradation of PNA. The addition of yeast extract or nutrient broth may enhance the degradation of PNA by (i) increasing the number of microorganisms capable of degrading the chemical or (ii) serving as carbon or energy source for microorganisms capable of co-metabolizing PNA.

Description of key information

Based on the available data used in a Weight-of-evidence approach, PNA is considered to be inherently biodegradable in wastewater treatment plants as well as the aquatic environment.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Additional information

Three studies are available investigating the biodegradation of N-phenyl-1-naphtylamine in water. In one ready biodegradation screening study, the degradation of the test substance (purity 99.5%) was determined according to OECD guideline 301C (Kanne 1990). An initial test substance concentration of 100 mg/L was used. After an incubation time of 28 days, 0% degradation was observed. This finding is supported by a second ready biodegradation screening study conducted by the Japanese National Institute of Technology and Evaluation (MITI Database 2002), also reporting 0% degradation after 14 d in a test according to OECD guideline 301C. Hence the test substance is considered as not readily biodegradable under this test conditions.

However, a third study following recommendations of the US-EPA and measuring CO2 evolution, yielded 50% degradation of N-phenyl-1-naphtylamine within 5 days in sewage effluent and >75% and 100% degradation within 2 and 10 days, respectively, in supplemented sewage sludge (Sikka et al. 1981). For lake water, 50% degradation after 5 days and > 90% degradation after 18 days were observed. In this study, the presence of major transient metabolites was shown (95% of extractable radioactivity after 10 d) and tentatively identified by GC-MS as dihydroxy derivative of N-phenyl-1-naphtylamine (m/e 252) and N-acetyl-N-phenyl-1- naphtylamine (m/e 262).

Based on the available data used in a Weight-of-evidence approach, the test substance is considered to be inherently biodegradable in wastewater treatment plants as well as the aquatic environment.