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Biodegradation in water and sediment: simulation tests

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Endpoint:
biodegradation in water: simulation testing on ultimate degradation in surface water
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1993
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 309 (Aerobic Mineralisation in Surface Water - Simulation Biodegradation Test)
Deviations:
yes
Remarks:
purity of test substance not reported; half of the sediment-water samples were bubbled with N2 prior to addition of the test substance and not shaken during incubation
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems)
Deviations:
yes
Remarks:
purity of test substance not reported; half of the sediment-water samples were bubbled with N2 prior to addition of the test substance and not shaken during incubation
GLP compliance:
no
Radiolabelling:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
natural water / sediment
Details on source and properties of surface water:
- Details on collection (e.g. location, sampling depth, contamination history, procedure): The seawater used was collected below the halocline in a less polluted coastal area
Details on source and properties of sediment:
sieved soft bottom sediment
Details on inoculum:
not specified
Duration of test (contact time):
8 - 16 wk
Initial conc.:
11 µg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
radiochem. meas.
Details on study design:
TEST CONDITIONS
- Test temperature: 11 +/- 2 °C
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 2L Erlenmeyer flasks with either only 1 L of seawater or both 1 L of seawater and 50 ml of sieved (1mm) soft bottom sediment.
- 5.45 ml of concentrated formalin were supplied to 4 flasks containing seawater
- Half of the flasks containing seawater and sediment were bubbled with nitrogen gas for 15 min
- An amount of 0.06 µCi 14C-NP (11 µg) dissolved in acetone was added to each of a number of small glass plates and the solvent was evaporated at room temperature.
- One glass plate with 14C-NP was added to each of the prepared E-flasks which were sealed and shaken vigorously.
- Incubated flasks were shaken twice a week for one minute.
- The N2 bubbled flasks were not shaken.

SAMPLING
- Sampling frequency: 1, 2, 4 and 8 weeks, moreover for flasks without sediment after 16 weeks (four replicates)
Compartment:
other: water, material (mass) balance
% Recovery:
78
Compartment:
other: sediment, material (mass) balance
% Recovery:
100
Key result
% Degr.:
44
Parameter:
radiochem. meas.
Remarks:
of formed 14CO2
Sampling time:
58 d
Remarks on result:
other: sediment
Key result
% Degr.:
50
Parameter:
radiochem. meas.
Remarks:
of formed 14CO2
Sampling time:
58 d
Remarks on result:
other: seawater
Remarks on result:
not measured/tested
Transformation products:
not measured
Evaporation of parent compound:
not measured
Volatile metabolites:
not measured
Residues:
not measured
Details on results:
- The recovery of labelled carbon dioxide which was expelled and collected immediately after the addition of 14C-carbonate to the flasks with seawater was 78 % and from the flasks with sediment in addition it was about 100 %.
- The corresponding recovery at collection 8 weeks after the carbonate addition was 94 % and 80 %, respectively.
- When using the method described above, no radioactivity was obtained from flasks which had been incubated for 8 weeks after the addition of formalin besides 14C-NP. => No mineralization of NP in the absence of microorganisms, unchanged NP does not contribute to the radioactivity in the final sample

DEGRADATION IN THE ABSENCE OF SEDIMENT:
- very slow during the first weeks (about 0.06 % of NP degraded per day)
- increased after 28 days to about 1 % per day-> microorganisms adapted to the added substrate

DEGRADATION IN THE PRESENCE OF SEDIMENT AND O2:
- high from the beginning (1.2 % NP per day)
- half as rapid at very low oxygen concentrations
- higher rate in presence of sediment probably due to larger number of microorganisms
- rate did not increase with time -> lack of substrate adaption may be explained with by the richer supply of other carbon sources and by decreased availability of NP due to adsorption down to a level where no adaption is induced

RECOVERY:
- No transformation of NP should have occurred in the flasks with added formalin, and from these samples 84% of the added radioactivity was extracted by hexane : diethyl ether.
- From the samples without formalin and sediment, 64 % of the radioactivity was recovered, 44 % in the CO2 fraction and 20 % in the organic solvent. The remaining 36 % of the radioactivity not recovered, may have existed partially as NP metabolites with high water solubility.
- Whether the nonylphenol molecule is attacked in the nonyl or the phenol part, carboxylic groups should be formed and the reaction then will give products which are more water-soluble than the original compound. Inability to recover all the added radioactivity is a common observation in degradation tests.
- From the flasks with sediment, 49 % of the added activity was regained, 46 % in the CO2 fraction and 3 % in the organic solvent.
- It is possible that a significant part of undegraded NP was not extracted as it had been adsorbed to the sediment particles for a long period of time. In this case part of the lost radioactivity may similarly have occurred in water-soluble intermediates. Thus a larger proportion of NP may have been transformed or degraded than is indicated by the radioactivity in the carbon dioxide fraction.

Results with reference substance



Not applicable


Applicant's summary and conclusion
Validity criteria fulfilled:
not applicable
Executive summary:

Biodegradation of 14C-labelled nonylphenol at the concentration of 11 µg/L in seawater alone and in seawater and marine sediment has been estimated by collection and quantification of the formed labelled CO2.

With seawater only, the initially degradation was very slow but when (after four weeks at 11 °C) the microorganisms had become adapted, the degradation rate increased rapidly, and after 58 days about 50% of 14C from NP was found in the CO2 fraction.

In the presence of sediment the initial degradation rate was high and did not increase after longer incubation. Approximately 44% percent of the test substance was degraded after 58 days. Lack of oxygen reduced the degradation rate by half in the presence of sediment.

Endpoint:
biodegradation in water: sediment simulation testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Analogue justification document is in chapter 13
Reason / purpose:
read-across source
GLP compliance:
no
Key result
% Degr.:
44
Parameter:
radiochem. meas.
Remarks:
of formed 14CO2
Sampling time:
58 d
Remarks on result:
other: sediment
Remarks on result:
not measured/tested
Transformation products:
not measured
Endpoint:
biodegradation in water: simulation testing on ultimate degradation in surface water
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
see Analogue justification document in chapter 13
Reason / purpose:
read-across source
GLP compliance:
no
Key result
% Degr.:
50
Parameter:
radiochem. meas.
Remarks:
of formed 14CO2
Sampling time:
58 d
Remarks on result:
other: seawater
Remarks on result:
not measured/tested
Transformation products:
not measured

Description of key information

Seawater: 50% degradation in 58 days (simulation test, read across)

Sediment: 44% degradation in 58 days (simulation test, read across)

Key value for chemical safety assessment

Additional information

Since no simulation studies assessing the biodegradability of Benzaldehyde, 2-hydroxy-5-nonyl, oxime, branched (CAS 174333-80-3) in water and sediment are available, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 Grouping of substances, a read-across to Phenol,4-nonyl-,branched (CAS 84852-15-3) was conducted , which is on the one hand a secondary component of the substance and on the other hand structurally very similar to the main component of the substance. The only structural difference between the source substance and the target substance is the lack of a aldoxime group at the phenol ring of the molecule. The read across is justified by similarity of structure and functional groups and accordingly similar physico-chemical properties, which is expected to result in similar environmental behavior and fate (see table below and the Analogue justification document attached).

Substance

Benzaldehyde, 2-hydroxy-5-nonyl, oxime, branched

Phenol, 4-nonyl, branched*

CAS number

174333-80-3

84852-15-3

Structure

see attachment (chapter 6.1)

 see attachment (chapter 6.1)

Molecular formula

C16O2NH25

C15H24O

Molecular weight

~ 263 g/mole

~ 220.35 g/mole

PC parameter

 

 

Water solubility

0.4 mg/L (EU method A.6)

5.7 mg/L (ASTM E 1148-02)

Partition coefficient

5.5 (EU method A.8)

5.4 (OECD 117)

Vapour pressure

0.37 Pa at 20 °C (OECD 104)

~1 Pa at 20 °C (ASTM-D 2879)

Environmental fate

 

 

Biodegradability

0 % in 28 days (OECD 302c)

non-adapted inoculum:

0 % in 28 days (OECD 301B)

 

adapted inoculum:

48.2-62 % in 28 days (OECD 301B)

Adsorption [log KOC]

3.7 (OECD 121)

4.35 - 5.69 (EPA OTS 796.2750)

Hydrolysis

not relevant

Ecotoxicology

 

 

Short-term toxicity to fish

[96h-LC50]

1.1 mg/L (EU method C.1)

0.05 – 0.22 mg/L (different methods)

Long-term toxicity to fish

[NOEC]

0.005 mg/L (OECD 210)

0.006 mg/L (ASTM E 1241-05)

Short-term toxicity to aquatic invertebrates

[48h-EC50]

2.7 mg/L (EU method C.2)

0.08 – 0.14 mg/L (different methods)

Long-term toxicity to aquatic invertebrates

[21d-NOEC]

0.189 mg/L (OECD 211)

0.024 - 0.116 mg/L (different methods)

Short-term toxicity to algae

[72h-EC50]

36.3 mg/L (OECD 201)

0.33 - 1.3 mg/L (different methods)

Long-term toxicity to algae

[72h-NOEC/EC10]

14.9 mg/L (OECD 201)

0.5 mg/L (Algal growth inhibition test according to UBA 1984)

Toxicity to microorganisms

[EC50]

200.4 mg/L (OECD 209)

950 mg/L (OECD 209)

* Data were taken from Phenol, 4-nonyl-,branched (CAS 84852-15-3) dossier published on the ECHA data base

 

Several water/sediment - simulation studies with 4-nonylphenol are available in the literature. However, only one study clearly indicated that branched nonylphenol was tested. Ekelund et al.(1993) studied the biodegradation of 4-nonylphenol in seawater and sediment using a test design similar to OECD guideline 308/309. In the experiments 14C uniformly ring-labelled nonylphenol (synthesized using nonene containing a mixture of branched isomers) was used. The reaction flasks used contained seawater or seawater plus sieved soft bottom sediment. Formalin was added to four flasks containing seawater and half of the flasks containing seawater and sediment were bubbled with nitrogen gas prior to the start of the experiment. 11 µg 14C ring-labelled nonylphenol was dissolved in acetone and added to small glass plates, the solvent was then evaporated and the glass plates added to the reaction flasks. The flasks were incubated at 11 ± 2 °C in the dark for 16 weeks. In flasks containing formalin no 14CO2 was recovered, indicating that any 14CO2 must come from the nonylphenol in the presence of living organisms. In the absence of sediment, degradation (as measured by 14CO2 production) was very slow at 0.06% per day up to 28 days than 1% per day after 28 days, suggesting a period of adaptation is required. In the presence of sediment the degradation rate was faster at 1.2% per day. In the low oxygen experiments the reaction rate was slow. The increase in degradation rate in the sediment system was attributed to the higher number of microorganisms present. The overall recovery of 14C from these experiments was around 64% (44% in the CO2 fraction) in the flasks without sediment and 49% (46% in the CO2 fraction) in the flasks with sediment. Thus, around 45% of the ring-label was converted to CO2 in 8 weeks, giving a mineralization half-life of slightly longer than 56 days (~ 58d). Lack of oxygen reduced the degradation rate by half in the presence of sediment. However, the low overall recovery of 14C-label in the experiments indicates that the actual extent of biodegradation may be higher (with a resulting shorter half-life) than implied by the 14CO2 measurements (for example incorporation of the 14C-label into biomass may have occurred. In conclusion, branched nonylphenol is considered to be inherently biodegradable in marine water and sediment. This conclusion is also considered to be true for Benzaldehyde, 2-hydroxy-5-nonyl, oxime, branched (CAS 174333-80-3).