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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Endpoint:
biodegradation in water: sewage treatment simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
11/01/2012 - 08/03/2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP, Guideline study
Qualifier:
according to guideline
Guideline:
other: Commission Regulation 440/2008/EC, Method C.4-D
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: OECD 301 F
Deviations:
no
GLP compliance:
yes
Radiolabelling:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Aerobic activated sludge, micro organisms from a domestic waste water treatment plant was supplied by the sewage plant Rossdorf, Germany.
Duration of test (contact time):
28 d
Initial conc.:
102 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Reference substance:
other: Sodium benzoate as procedure control
Test performance:
The test item dinotefuran technical contains nitrogen, therefore the evaluation of biodegradation has to be based ThODNH4 and ThODNO3. The criterion for ready biodegradability under the conditions of a manometric respirometry test is the 10-day window, describing the period between reaching at least 10% degradation and 60% degradation. This period should not exceed 10 days.

The mean biodegradation after 28 days of dinotefuran technical was 0% (ThODNH4) and (ThODNO3); the 10 day window criterion was not passed.
Therefore, dinotefuran technical is considered not to be readily biodegradable.

The reference item sodium benzoate was sufficiently degraded to 85% after 14 days and after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used.

In the toxicity control containing both, the test item and the reference item sodium benzoate, 52% (ThODNH4) and 35% (ThODNO3) biodegradation was noted within 14 days and 50% (ThODNH4) and 34% (ThODNO3) biodegradation after 28 days of incubation. Thus, the test item can be assumed to be not inhibitory to the aerobic activated sludge micro organisms.
% Degr.:
0
Parameter:
O2 consumption
Sampling time:
28 d
Transformation products:
not measured
Evaporation of parent compound:
not measured
Volatile metabolites:
not measured
Residues:
not measured
Details on results:
The test item dinotefuran technical contains nitrogen, therefore the evaluation of biodegradation has to be based ThODNH4 and ThODNO3. The criterion for ready biodegradability under the conditions of a manometric respirometry test is the 10-day window, describing the period between reaching at least 10% degradation and 60% degradation. This period should not exceed 10 days.

The mean biodegradation after 28 days of dinotefuran technical was 0% (ThODNH4) and (ThODNO3); the 10 day window criterion was not passed.
Therefore, dinotefuran technical is considered not to be readily biodegradable.

Results with reference substance:
The reference item sodium benzoate was sufficiently degraded to 85% after 14 days and after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used.

In the toxicity control containing both, the test item and the reference item sodium benzoate, 52% (ThODNH4) and 35% (ThODNO3) biodegradation was noted within 14 days and 50% (ThODNH4) and 34% (ThODNO3) biodegradation after 28 days of incubation. Thus, the test item can be assumed to be not inhibitory to the aerobic activated sludge micro organisms.
Validity criteria fulfilled:
yes
Conclusions:
The degradation rate of dinotefuran technical did not reach 60% within the 10-day window and after 28 days of incubation.

Therefore, dinotefuran technical is considered not to be readily biodegradable.

The percentage biodegradation of the reference item confirms the suitability of the used aerobic activated sludge inoculum.

According to the validity criteria of OECD test guideline 301, the test item can be assumed to be not inhibitory on the aerobic activated sludge micro organisms because degradation was >25% within 14 days.
Endpoint:
biodegradation in water: sediment simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
09/12/1998 - 20/10/2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP, Guideline study
Qualifier:
according to guideline
Guideline:
EPA Subdivision N Pesticide Guideline 162-4 (Aerobic Aquatic Metabolism)
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: SETAC Europe: Guideline 8.2
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: Commission Directive 95/36/EC of 14 July 1995 amending Council Directive 91/414/EEC: Annex I: 7.2.1.3.2 Water/Sediment Study
Deviations:
no
GLP compliance:
yes
Radiolabelling:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
natural water / sediment
Details on source and properties of surface water:
See Table 1
Details on source and properties of sediment:
See Table 1
Duration of test (contact time):
320 d
Initial conc.:
0.05 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
radiochem. meas.
test mat. analysis
Details on study design:
See Table 2
Reference substance:
not required
Compartment:
other: water / sediment, material (mass) balance
Remarks on result:
other: See Table 3
Compartment:
water
DT50:
49 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: River
Compartment:
water
DT50:
23 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Pond
Compartment:
sediment
DT50:
45 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: River
Compartment:
sediment
DT50:
128 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Pond
Compartment:
entire system
DT50:
57 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: River
Compartment:
entire system
DT50:
45 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Pond
Transformation products:
yes
No.:
#1
Details on transformation products:
Dinotefuran mainly degraded to DN, reaching a maximum amount of 23.1% and 32.6% AR in the river and pond system at 180 and 103 days, respectively. Additionally up to 5 minor degradation products were formed but never exceeding 5% AR. Half lives for the degradation product DN could be calculated.

Aerobic DT50 [days]: River and pond system; 114 and 80
Evaporation of parent compound:
not measured
Volatile metabolites:
yes
Residues:
not measured
Details on results:
The degradation of dinotefuran under aerobic conditions was studied with 14C labelled test substance in two different labels. Two water/sediment systems of differing properties were selected.

In the experiment, total recoveries of radioactivity (mass balances) were generally 95.2±5.9% applied radioactivity (AR) for the river system and 96.6±3.7% for the pond system. In the last sampling point at 320 days after application, the recoveries went below 90% in the river system. Total radioactivity in water declined from 98% on day 0 to 8.3% AR on day 320 in the river, and from 98.4% to 2.6% AR in the pond. There were corresponding increases with time in sediment radioactivity with maxima of 50.3% AR in the river (day 141) and 77.2% in the pond system (day 180). Of the radioactivity associated with the sediment, non-extractable residues also increased with time to maxima of 29.5% AR in the river and 62.4% AR in the pond system. Volatile radioactivity, all associated with 14CO2, represented a maximum of 34.4% AR in the river samples and 19.9% AR in the pond samples. Degradation half lives in the total system of 57 and 45 days were calculated.

Chromatographic profiles were qualitatively similar between aquatic sediments. A significant metabolite in both the aerobic and anaerobic experiments was DN, formed by loss of the 2-nitro group. This degradation product accounted for up to 32.6% AR in the total system. A number of minor degradation products were formed, none accounting for more than 5.0% AR in any system.
Results with reference substance:
No reference substance used.

Table 3:           Distribution and recovery of radioactivity in aerobic pond sediment

Sample

Time after application [days]

 

0

1

2

7

14

28

56

103

141

180

258

320

Water

98.4

89.1

82.7

75.9

59.3

41.4

23.4

11.8

7.7

5.4

3.0

2.6

Extractable sediment

3.5

9.6

14.8

21.0

33.4

29.0

36.8

46.4

29.7

22.5

12.4

13.2

Non-extractable sediment

0.3

0.7

1.6

2.8

5.9

21.8

31.3

25.4

43.6

54.7

62.4

62.9

Organic volatiles

-

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

CO2

-

<0.1

<0.1

0.1

0.7

1.2

2.3

7.3

10.3

14.8

19.9

15.7

Total recovery

102.2

99.4

99.1

99.8

99.3

93.5

93.7

90.9

91.3

97.5

97.7

94.4

Identified as parent

101.9

98.7

97.5

95.2

81.9

58.4

37.0

24.0

18.1

11.3

7.3

7.6

Identified as DN

n.d.

n.d.

n.d.

n.d

8.6

8.8

20.1

32.6

18.8

15.2

8.1

7.8

n.d. not detected or below limit of quantification

DN: l-methyl-3-(tetrahydro-3-furylmethyl) guanidinium

Minor degradation products are not listed in the table

Validity criteria fulfilled:
yes
Conclusions:
Dinotefuran declined from the water of aerobic aquatic sediment systems with DT50 values of 49 and 23 days (river and pond system, respectively). Corresponding DT50 values for sediments were 45-128 days, and for the total system 57-45 days, respectively.

One major degradation product was formed, DN, which accounted for up to 32.6% of the applied radioactivity. DT50 values of 114 and 80 days were calculated for DN in the river and pond system, respectively.

Description of key information

Dinotefuran declined from the water of aerobic aquatic sediment systems with DT50 values of 49 and 23 days (river and pond system, respectively). Corresponding DT50 values for sediments were 45-128 days, and for the total system 57-45 days, respectively.

Key value for chemical safety assessment

Half-life in freshwater:
49 d
at the temperature of:
20 °C
Half-life in freshwater sediment:
128 d
at the temperature of:
20 °C

Additional information

Dinotefuran was shown to degrade slowly but steadily in water-sediment systems with DT50 values (at 20 °C) of 59.00 d (total river system) and 46.55 d (total pond system) using sequential “parent & metabolite” SFO kinetic modelling. When corrected to 12 °C, total system degradation DT50 values of 88.3 d (pond) and 112 d (river) were predicted