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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
10 Apr 2017 - 12 May 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Justification for type of information:
Information is used for read across to Ethyl amyl ketone (EAK)
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Version / remarks:
1992
Qualifier:
according to
Guideline:
ISO 10707 Water quality - Evaluation in an aqueous medium of the "ultimate" aerobic biodegradability of organic compounds - Method by analysis of biochemical oxygen demand (closed bottle test)
Version / remarks:
1994
GLP compliance:
yes
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: EM97160108
- Expiration date of the lot/batch: 14 January 2018 (expiry date)
- Purity test date: 07/07/2016 (certificate of analysis)

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature
- Solubility and stability of the test substance in the solvent/vehicle: Solubility in Water: 167.3 mg/L (20ºC, pH=6.3)

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: n/a
- Preliminary purification step (if any): n/a
- Final preparation of a solid: n/a

OTHER SPECIFICS:
Purity/composition correction factor: No correction factor required
Test item handling: No specific handling conditions required
Molecular formula: C9H18O
Molecular weight: 142.239
Stability in Water: Not available
Oxygen conditions:
aerobic
Inoculum or test system:
natural water
Details on inoculum:
Source:
The source of test organisms was secondary effluent freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.

Treatment:
Secondary effluent was filtered through a coarse filter paper, the first 200 mL was discarded. The filtrate was kept aerated until inoculation.

Inoculation:
4 mL filtrate of secondary effluent per litre of final volume
Duration of test (contact time):
28 d
Initial conc.:
1 mg/L
Based on:
test mat.
Initial conc.:
2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Remarks:
as a percentage of ThOD
Details on study design:
TEST CONDITIONS
-Test duration:
28 days for the inoculum blank and test suspension; 14 days for the procedure and toxicity control

- Milli-RO water:
Tap-water purified by reverse osmosis (Millipore Corp., Bedford, Mass., USA).

- Stock solutions of mineral components:
A)8.50 g KH2PO4
21.75 g K2HPO4
67.20 g Na2HPO4.12H2O
0.50 g NH4Cl
dissolved in 1 litre Milli-RO water, pH 7.4 + 0.2
B)22.50 g MgSO4.7H2O dissolved in 1 litre Milli-ROwater.
C)36.40 g CaCl2.2H2O dissolved in 1 litre Milli-RO water.
D)0.25 g FeCl3.6H2O dissolved in 1 litre Milli-RO water.

-Mineral medium:
1 mL of solution (A) to (D) was mixed and made up to 1 litre with Milli-RO water.

The concentration of dissolved oxygen was measured for control purposes. The mineral medium was left at test temperature to obtain a saturated solution at the start of the test.

- Test temperature: 22.0 - 23.1°C.

- pH: 7.6

- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Test bottles: 250-300 mL BOD bottles with glass stoppers.
- Number of culture flasks/concentration: Individual BOD bottles were prepared for each measuring bottles point, except that the bottles measured at the start were also measured on day 7. Parallel groups were prepared to allow duplicate measurements of oxygen consumption at the test intervals.
- Measuring equipment: WTW oxygen meter supplied with a WTW CellOx 325 oxygen
electrode, electrolyte type ELY/G.
- Test performed in closed vessels due to significant volatility of test substance: yes

SAMPLING
- Sampling frequency: In duplicate; immediately at the start of the experiment (day 0), and at day 7, 14, and on day 21 and 28 for the inoculum blank and test item.

Determination of oxygen concentration:
Oxygen meter: WTW oxygen meter supplied with a WTW CellOx 325 oxygen
electrode, electrolyte type ELY/G.

pH: At the start of the test.
Temperature of medium: Continuously in a vessel with Milli-RO water in the same room.

CONTROL AND BLANK SYSTEM
Inoculum blank: Containing only inoculum (no test item)
Procedure control: Containing reference item and inoculum
Test suspension: Containing test item and inoculum (applicable for both test concentrations)
Toxicity control: Containing test item at the lowest concentration, reference item and inoculum.

ANALYSIS:
The specific theoretical oxygen demand (ThOD) of the test item was calculated, since the
elemental composition of the test item was known.
Reference substance:
acetic acid, sodium salt
Test performance:
The test is valid as shown by an endogenous respiration of 1.0 mg/L at day 28. Furthermore, the differences between the replicate values at day 28 were less than 20% (≤ 11%). Sodium acetate was degraded by at least 60% (76%) of its theoretical oxygen demand within 14 days. Degradation of sodium acetate was not inhibited by the test substance. Finally, the concentration of dissolved oxygen did not fall below 0.5 mg/L in all bottles during the test period.

As for test conditions, the pH values at the start of the test were 7.6 for all vessels. The temperature recorded in a vessel with water in the same room varied between 22.0 and 23.1°C.
Parameter:
% degradation (O2 consumption)
Value:
52
Sampling time:
7 d
Remarks on result:
other: 1mg/L dose
Parameter:
% degradation (O2 consumption)
Value:
66
Sampling time:
14 d
Remarks on result:
other: 1mg/L dose
Parameter:
% degradation (O2 consumption)
Value:
63
Sampling time:
21 d
Remarks on result:
other: 1mg/L dose
Key result
Parameter:
% degradation (O2 consumption)
Value:
60
Sampling time:
28 d
Remarks on result:
other: 1mg/L dose
Parameter:
% degradation (O2 consumption)
Value:
62
Sampling time:
7 d
Remarks on result:
other: 2 mg/L dose
Parameter:
% degradation (O2 consumption)
Value:
65
Sampling time:
14 d
Remarks on result:
other: 2 mg/L dose
Parameter:
% degradation (O2 consumption)
Value:
62
Sampling time:
21 d
Remarks on result:
other: 2 mg/L dose
Key result
Parameter:
% degradation (O2 consumption)
Value:
57
Sampling time:
28 d
Remarks on result:
other: 2 mg/L dose
Details on results:
The relative biodegradation values calculated from the O2 measurements performed during the test period of 28 days revealed significant biodegradation of Nonan-2-one (methyl heptyl ketone) at both concentrations at the end of the test, i.e. 60% and 57% for the low and high concentration, respectively. In addition, >60% biodegradation was attained within a 14-day window.

Apparently, the total biodegradation of the test item slightly decreases from day 14 to day 28. This is due to experimental variation in the individual inoculum blanks as well as the test item replicates. The fact that the test item was >60% biodegraded after 7 and 14 days of incubation in the high and low concentration, respectively, firmly supports a readily biodegradable classification.
Results with reference substance:
Sodium acetate (procedure control) was degraded by at least 60% (76%) within 14 days which fulfills validity criteria

In the toxicity control more than 25% biodegradation occurred within 14 days (71%, based on ThOD). Thus, the toxicity control showed that Nonan-2-one (methyl heptyl ketone) did not inhibit microbial activity.

Validity criteria fulfilled:
yes
Remarks:
The reference substance, toxicity of the test substance, the difference of the replicates at 28d, O2 depletion (inoculum blank) and residual O2 conc in the test bottles met the validity criteria.
Interpretation of results:
readily biodegradable
Conclusions:
Nonan-2-one (methyl heptyl ketone) showed >=60% biodegradation in an OECD TG 301D test at 28d and met the 14-day time window so is considered to be readily biodegradable.
Executive summary:

The ready biodegradability of Nonan-2-one (methyl heptyl ketone) was investigated in a study conducted in accordance with OECD TG 301D (closed bottle test) and GLP. Nominal concentrations of 1 and 2 mg/L of Nonan-2-one (methyl heptyl ketone) were tested. Measurements of the oxygen concentrations were performed at the start of the experiment (day 0) and at day 7, 14, and on day 21 and 28 for the inoculum blank and test item. Sodium acetate was degraded by at least 60% (76%) of its theoretical oxygen demand within 14 days. In addition the toxicity control showed that the substance did not inhibit microbial activity. The relative biodegradation values calculated from the O2 measurements performed during the test period of 28 days revealed significant biodegradation of Nonan-2-one (methyl heptyl ketone) at both concentrations at the end of the test, i.e. 60% and 57% for the low and high concentration, respectively. 60% biodegradation of Nonan-2-one (methyl heptyl ketone) was already reached after 7 and 14 days of incubation in the high and low concentration, respectively. Nonan-2-one (methyl heptyl ketone) is therefore designated as readily biodegradable.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
See attached justification document
Reason / purpose:
read-across source
Test performance:
The test is valid as shown by an endogenous respiration of 1.0 mg/L at day 28. Furthermore, the differences between the replicate values at day 28 were less than 20% (≤ 11%). Sodium acetate was degraded by at least 60% (76%) of its theoretical oxygen demand within 14 days. Degradation of sodium acetate was not inhibited by the test substance. Finally, the concentration of dissolved oxygen did not fall below 0.5 mg/L in all bottles during the test period.
As for test conditions, the pH values at the start of the test were 7.6 for all vessels. The temperature recorded in a vessel with water in the same room varied between 22.0 and 23.1°C.
Parameter:
% degradation (O2 consumption)
Value:
52
Sampling time:
7 d
Remarks on result:
other: 1mg/L dose
Parameter:
% degradation (O2 consumption)
Value:
66
Sampling time:
14 d
Remarks on result:
other: 1mg/L dose
Parameter:
% degradation (O2 consumption)
Value:
63
Sampling time:
21 d
Remarks on result:
other: 1mg/L dose
Key result
Parameter:
% degradation (O2 consumption)
Value:
60
Sampling time:
28 d
Remarks on result:
other: 1mg/L dose
Parameter:
% degradation (O2 consumption)
Value:
62
Sampling time:
7 d
Remarks on result:
other: 2 mg/L dose
Parameter:
% degradation (O2 consumption)
Value:
65
Sampling time:
14 d
Remarks on result:
other: 2 mg/L dose
Parameter:
% degradation (O2 consumption)
Value:
62
Sampling time:
21 d
Remarks on result:
other: 2 mg/L dose
Key result
Parameter:
% degradation (O2 consumption)
Value:
57
Sampling time:
28 d
Remarks on result:
other: 2 mg/L dose
Details on results:
The relative biodegradation values calculated from the O2 measurements performed during the test period of 28 days revealed significant biodegradation of Nonan-2-one (methyl heptyl ketone) at both concentrations at the end of the test, i.e. 60% and 57% for the low and high concentration, respectively. In addition, >60% biodegradation was attained within a 14-day window.

Apparently, the total biodegradation of the test item slightly decreases from day 14 to day 28. This is due to experimental variation in the individual inoculum blanks as well as the test item replicates. The fact that the test item was >60% biodegraded after 7 and 14 days of incubation in the high and low concentration, respectively, firmly supports a readily biodegradable classification.
Results with reference substance:
Sodium acetate (procedure control) was degraded by at least 60% (76%) within 14 days which fulfills validity criteria

In the toxicity control more than 25% biodegradation occurred within 14 days (71%, based on ThOD). Thus, the toxicity control showed that Nonan-2-one (methyl heptyl ketone) did not inhibit microbial activity.

Validity criteria fulfilled:
yes
Remarks:
Results for EAK are validated in the read across justification
Interpretation of results:
readily biodegradable
Conclusions:
According to the read-across assessment from the source Nonan-2-one (MHK) to the target substance Octan-3-one (EAK), EAK is readily biodegradable.
Nonan-2-one (methyl heptyl ketone) showed >=60% biodegradation in an OECD TG 301D test at 28d and met the 14-day time window so is considered to be readily biodegradable.
Executive summary:

Based on the read across assessment from the source Nonan-2-one (MHK) to the target substance Octan-3-one (EAK), EAK is considered readily biodegradable.The ready biodegradability of Nonan-2-one (methyl heptyl ketone) was investigated in a study conducted in accordance with OECD TG 301D (closed bottle test) and GLP. Nominal concentrations of 1 and 2 mg/L of Nonan-2-one (methyl heptyl ketone) were tested. Measurements of the oxygen concentrations were performed at the start of the experiment (day 0) and at day 7, 14, and on day 21 and 28 for the inoculum blank and test item. Sodium acetate was degraded by at least 60% (76%) of its theoretical oxygen demand within 14 days. In addition the toxicity control showed that the substance did not inhibit microbial activity. The relative biodegradation values calculated from the O2 measurements performed during the test period of 28 days revealed significant biodegradation of Nonan-2-one (methyl heptyl ketone) at both concentrations at the end of the test, i.e. 60% and 57% for the low and high concentration, respectively. 60% biodegradation of Nonan-2-one (methyl heptyl ketone) was already reached after 7 and 14 days of incubation in the high and low concentration, respectively. Nonan-2-one (methyl heptyl ketone) is therefore designated as readily biodegradable.

Description of key information

Based on the read across assessment from the source Nonan-2-one (MHK) to the target substance Octan-3-one (EAK), EAK is considered readily biodegradable, based on a OECDTG301D test result, >= 60% biodeg at 28d.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Read across justification is attached in the Target file.