2-(2-butoxyethoxy)ethyl 6-propylpiperonyl ether

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Type of information:

experimental study

Adequacy of study:

key study

Study period:

12.03.1990-22.08.1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

EPA Subdivision N Pesticide Guideline 162-4 (Aerobic Aquatic Metabolism)

Deviations:

yes

Remarks:

An agricultural soil instead of sediment was used for test item.

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

A stock solution was prepared with a measured concentration of 660 µg/mL and radiopurity of 94.1 %.
A second stock solution was prepared by purification by reverse ühase linear thin-layer chromatography with a measured concentration of 848 µg/mL and radiopurity of 98.7 %.

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water

Remarks:

Natural soil samples were flooded with natural water.

Details on source and properties of surface water:

- Details on collection (e.g. location, sampling depth, contamination history, procedure): Natural water samples were obtained from a well in Columbia, Missouri, USA.
- Storage conditions: not specified
- Storage length: not specified
- Temperature (°C) at time of collection: 20°C
- pH at time of collection: 8.1
- Electrical conductivity: 520 µMhos/cm
- Redox potential (mv) initial/final: not specified
- Oxygen concentration (mg/l) initial/final: 8.1 mg/L
- Hardness (CaCO3): 270
- Dissolved organic carbon (%): not specified
- Biomass (e.g. in mg microbial C/100 mg, CFU or other): not specified
- Water filtered: not specified
- Type and size of filter used, if any:

Details on source and properties of sediment:

See details on surface water and inoculum.

Details on inoculum:

- Source of inoculum wastewater (e.g. location, contamination history): Natural soil samples were obtained from an agricultural site near Ashland, Nebraska, USA.
- Storage conditions: RT
- Textural classification (i.e. %sand/silt/clay): Sandy loam
- pH at time of collection: 6.8
- Organic carbon (%): 1.6 (organic matter)
- CEC (meq/100 g): 11.6
- Bulk density (g/cm³): 1.51
- Biomass (e.g. in mg microbial C/100 mg, CFU or other):
Total plate count: 1.92 x 10E+07 colonies/g
Fungal plate count: 2.0 x 10E+04 coloniers/g
- Samples sieved: air dried and sieved through a 2mm mesh screen

Duration of test (contact time):

30 d

Initial conc.:

9.82 other: mg/kg

Based on:

test mat.

Parameter followed for biodegradation estimation:

radiochem. meas.

Details on study design:

A 7-day preliminary study was run to evaluate the acceptability of the proposed experimental design and to estimate a half-life for Piperonyl Butoxide under aerobic aquatic conditions.


TEST CONDITIONS
- Volume of test solution/treatment: ca. 40 mL
- Composition of medium: 30 mL of water and 10 g of soil (dry weight)
- Additional substrate: no
- Solubilising agent (type and concentration if used): none
- Test temperature: 25°C +/- 1°C
- pH: not determined
- pH adjusted: no
- CEC (meq/100 g): not determined
- Aeration of dilution water: tubes were connected to air supply
- Suspended solids concentration: not determined
- Continuous darkness: yes
- Any indication of the test material adsorbing to the walls of the test apparatus: no
- Other:

TEST SYSTEM
- Culturing apparatus: 50 mL pyrex culture tubes, each placed in 3000 mL aeration vessels.
- Number of culture flasks/concentration: 36 flasks, 9 control samples, nine for replicate I and 8 for replicate II, one concentration
- Method used to create aerobic conditions: air supply at 50 mL/min under positive pressure
- Method used to create anaerobic conditions: not applicable
- Method used to control oxygen conditions: air supply
- Measuring equipment:

- Test performed in closed vessels due to significant volatility of test substance: closed system to trap 14C volatiles
- Test performed in open system: no

The incoming air was passed through a saturation bottle before entering the incubation vessel. The wasted air was passed trough a series of traps to collect volatiles (Ethylene glycol, 1 N H2SO4) and to absorb evolved CO2 (2x 1 N KOH traps).

- Details of trap for CO2 and volatile organics if used:
1. Ethylene glycol trap
2. 1 N H2SO4
3. 1 N KOH-1
4. 1 N KOH-2

- Other:

SAMPLING
- Sampling frequency: Day 0 (triplicate),1,2,7,14,21,30; Replicate II sample were placed in a freezer.
- Sampling method used per analysis type: centrifugation, then water was decanted and analyzed with LSC. Soil was extracted with methanol, shaken and centrifuged, and extracts were decanted. After triplicate extraction, the extracts were combined and analyzed by LSC. The soils were further extracted with NaOB:methanol (3:1, v/v) to give an orgaic re-extract.

Radioactivity of the water samples and in the sediment's methanol and NaOH/methanol extracts was analysed by LSC and TLC. Possible degradation products were analysed by TLC, HPLC and EI-MS for identification. Radioactivity in the trapping solutions was quantified by LSC.

The remaining soil samples were combusted.
- Sterility check if applicable: Samples were tested for microbial counts at T0 and T30.
- Sample storage before analysis:
- Other:

DESCRIPTION OF CONTROL AND/OR BLANK TREATMENT PREPARATION
CONTROL AND BLANK SYSTEM
- Inoculum blank:
- Abiotic sterile control:
- Toxicity control:
- Other:

STATISTICAL METHODS:
The half-life of Piperonyl Butoxide was calculated assuming first order kinetics.

Compartment:

entire system

% Recovery:

100

Remarks on result:

other: water soluble residues: 37.9 %

Compartment:

entire system

% Recovery:

100.5

Remarks on result:

other: water soluble residues: 35.7 %

Compartment:

entire system

% Recovery:

99.8

Remarks on result:

other: water soluble residues: 39.2 %

Compartment:

entire system

% Recovery:

101.2

Remarks on result:

other: water soluble residues: 41.7 %

Compartment:

entire system

% Recovery:

106.8

Remarks on result:

other: water soluble residues: 54.4 %

Compartment:

entire system

% Recovery:

104.8

Remarks on result:

other: water soluble residues: 55.7 %

Compartment:

entire system

% Recovery:

100

Remarks on result:

other: water soluble residues: 45.4 %

Key result

% Degr.:

16.2

Parameter:

radiochem. meas.

Sampling time:

30 d

Key result

Compartment:

entire system

DT50:

109 d

Type:

(pseudo-)first order (= half-life)

Temp.:

25 °C

Transformation products:

yes

No.:

#1

Details on transformation products:

Altogether 3 possible metabolites could be observed during the TLC analysis of water and soil extracts. None exceeded 10 % of applied radioactivity. One degradate, which had a maxima of 7.1 % at day 14, was qualitatively identified as one component and named Metabolite F (Origin). A slightly increase of two further metabolites could be observed, but not identified. They were named Unknown 1 (Intermediate II, Rf = 0.05) and Unknown 2 (Intermediate I, Rf = 0.1).

Proposed degradation pathway:
Parent compound > Intermediate I > Intermediate II > Metabolite F > 14CO2 + Non-extractable residues.- Formation and decline of each transformation product during test:
- Pathways for transformation: Parent - Unknown 1 - Unknown 2 - Metabolite F.
- Maximum occurrence of each transformation product:
Metabolite F: 7.1 %
Unknown 1: 1.19%
Unknown 2: 0.089%
- Other:

Evaporation of parent compound:

yes

Remarks:

All volatiles were determined to be CO2 (up to 0.122% at study termination).

Volatile metabolites:

no

Residues:

yes

Remarks:

The parent substance was not fully degraded and parent as well as the 3 metablites were present at study termination.

Details on results:

The half-life of Piperonyl Butoxide under aerobic aquatic conditions was calculated to be 109 days by using first-order kinetics. The kinetic constant for the degradation was obtained from the linear regression analysis of the plot of ln percent applied 14C-Piperonyl Butoxide versus days (y = -0.00638 x + 4.60, r = -0.899).

TEST CONDITIONS
- Aerobicity (or anaerobicity), moisture, temperature and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered (if yes): No
- The Total Plate Count decreased from 1.92E+07 to 2.0E+04 during the course of the study.

MAJOR TRANSFORMATION PRODUCTS
none

MINOR TRANSFORMATION PRODUCTS
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: Metabolite F reached up to 7.1% (day 14). Unknown 1 and 2 had their maximum at the end of the study.
- Range of maximum concentrations in % of the applied amount at end of study period: Metabolite F/Unknown 1/Unknown 2 were present at 5.37%/1.19%/0.89% at day 30.

TOTAL UNIDENTIFIED RADIOACTIVITY (RANGE) OF APPLIED AMOUNT:
none

EXTRACTABLE RESIDUES
- % of applied amount at day 0: 98.92%
- % of applied amount at end of study period: 93.69%

NON-EXTRACTABLE RESIDUES
- % of applied amount at day 0: 0.08%
- % of applied amount at end of study period: 6.31%

MINERALISATION
- % of applied radioactivity present as CO2 at end of study: 0.122%

VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: none

STERILE TREATMENTS (if used)
- Transformation of the parent compound:
- Formation of transformation products:
- Formation of extractable and non-extractable residues:
- Volatilization:

RESULTS OF SUPPLEMENTARY EXPERIMENT (if any):

Degradation of Piperonyl Butoxide and formation of metabolites in water/sediment systems (values are given as % of applied radioactivity).

 

Days after application	Ashland, Nebraska
	0	1	2	7	14	21	30
Water phase	45.4	55.7	54.2	41.7	39.2	35.7	37.9
Extractable	45.4	55.7	54.2	41.7	39.2	35.7	37.9
Piperonyl Butoxide	43.8	53.1	51.7	38.5	33.6	31.0	32.0
Metabolite F	1.0	1.6	1.6	2.2	3.7	3.4	4.1
Unknown 1	0.0	0.0	0.0	0.0	1.1	1.0	1.1
Sediment	54.5	48.8	52.2	57.6	57.2	59.3	55.7
Extractable	54.5	48.8	52.2	57.6	57.2	59.3	55.7
Piperonyl Butoxide	52.96	47.55	50.96	56.02	51.76	56.68	51.88
Metabolite F	0.43	1.41	1.53	0.68	3.54	1.48	1.71
Unknown 1	0.0	0.0	0.0	0.0	0.04	0.05	0.09
Unknown 2	0.0	0.0	0.0	0.0	0.05	0.07	0.09
Total not extractable	0.08	0.24	0.38	1.88	3.31	5.4	6.31
14CO2	0.0	0.0	0.0	0.013	0.031	0.051	0.122
TOTAL	99.98	104.74	106.78	101.19	99.74	100.45	100.03

 

Validity criteria fulfilled:

yes

Conclusions:

Piperonyl Butoxide was degraded in the aerobic aquatic metabolism study with an estimated half-life of 109 days (25°C).
There were no major metabolites.
The Total Plate Count decreased from 1.92E+07 to 2.0E+04 during the course of the study. It may be assumed that degradation and mineralization could have been faster if the microbial count had been stable at the inital level.

Executive summary:

Piperonyl Butoxide was degraded in the aerobic aquatic metabolism study with an estimated half-life of 109 days (25°C).
There were no major metabolites.
The Total Plate Count decreased from 1.92E+07 to 2.0E+04 during the course of the study. It may be assumed that degradation and mineralization could have been faster if the microbial count had been stable at the inital level.

Since an agriculural soil was used, the study may be cosidered less reliable than the study by Derz, 2006.

Reference 2

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

November 21, 2005 - Sept 5, 2006

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems)

GLP compliance:

yes (incl. QA statement)

Remarks:

Statement of GLP compliance from Fraunhofer Institute for Molecular Biology and Applied Ecology

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water / sediment

Details on source and properties of surface water:

Two sediment systems from a river and a pond including sediment and natural water were collected and were equilibrated in incubation flasks for 15 – 19 days at 20 °C ± 2 °C in the dark.

Details on source and properties of sediment:

The sediment with the “fine texture” was sampled from a pond (“Heiminghausen”) located close to the testing facility. The sediment with the “coarse texture” was collected from the creek “Wenne” which is also located close to the testing facility.
The water/sediment systems collected from a creek and a pond were set up in cylindrical glass vessels and were equilibrated under laboratory conditions (20 °C ± 2 °C, in the dark) for 15 days (creek) and 19 days (pond) before application.

Duration of test (contact time):

ca. 120 d

Initial conc.:

1 908 µg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

radiochem. meas.

Reference substance:

other: Di(5-Propyl-benzo[1,3]dioxole)methane

Compartment:

water

DT50:

27 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: test system : pond

Compartment:

water

DT50:

165 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: test system : creek

Compartment:

sediment

DT50:

81 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: test system : pond

Compartment:

sediment

DT50:

36 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: test system : creek

Compartment:

entire system

DT50:

55 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: test system : pond

Compartment:

entire system

DT50:

54 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: test system : creek

Transformation products:

not specified

Details on results:

DT90: Water phase Pond: 91
DT90: Water phase Creek : 549

DT90 Sediment: Pond :269
DT90 Sediment creek: 121

DT50 value of PBO in the total system calculated by the computer program ModelMaker was 54.5 days
As individual processes the DT50 values were calculated to 67 days in the compartment water and 54 days in the compartment sediment (geom. mean of pond and creek system).

Results with reference substance:

Results valid

A total radioactivity balance and the distribution of radioactivity in every incubation flask was established at each sampling day. The following results were obtained.

• Total mean recoveries ranged between 90.1 and 97.8 % of initially applied radioactivity (ITR).

• Only trace amounts of volatile metabolites with low molecular weight and with basic character (never exceeding 0.6 % ITR as sum) were produced during the aerobic soil degradation of PBO in the water/sediment systems.

• Radioactivity trapped in 1 N NaOH indicated the production of 14CO2 and therefore mineralization of the test item during the incubation time of 120 days. The mineralization rate depended on the water/sediment system used for aerobic degradation of PBO. In the creek sediment system a relatively low mineralization rate was determined in the extent of 1.9 % ITR. A higher amounts (6.6 % ITR) of radioactivity detected in the sodium hydroxide traps were found during degradation in the pond sediment system.

After treatment during the first three days of incubation the radioactivity recovered in the water phase was high, amounting to a maximum of 92.7 % of the applied radioactivity for the pond system and 89.1 % for the creek system. During the further incubation, the total radioactivity in water rapidly decreased, whilst that in sediment increased. At the end of incubation the amounts of radioactivity remaining in the water were 16.5 % ITR for the pond system and 39.5 % ITR in the creek system.

• The radioactivity extractable from sediment increased rapidly during the first 14 days of incubation. Thereafter it remained relatively constant at a value of around 50 % in the pond system or decreased slightly in the creek system after a maximum value of 33.7 % ITR (62 days) to 30.8 % ITR. The amount of non-extractable radioactivity (NER) generally increased with increasing incubation time. After 120 days of incubation, the NER amounted to 24.2 % ITR in the pond system and 20.8 % ITR in the creek system.

• Parent compound PBO detected in the water phase decreased nearly continuously with increasing incubation time down to values of 0.1 % ITR in the pond system and 0.7 % in the creek system at 120 days after application. This decrease was compensated by an increase of PBO in the sediment extract. At the end of experiments 23.7 % ITR in the pond system and 17.2 % ITR in the creek system were identified as PBO. However, the amount of PBO in the entire system decreased with increasing incubation to endpoints of 23.8 % ITR in the pond and 17.9 % in the creek system, respectively.

• One main metabolite (M2) was detected. This metabolite amounted up to 21.4 % ITR (entire system) during the incubation of the pond system. In the entire creek system metabolite M2 correspond to a maximum value of 40.7 % ITR (100 days), which decreased to 36.1 % ITR at the end of experiment. Further metabolites were M1, which amounted to 7.6 % in the entire pond system and 4.4 % ITR in the entire creek system, and EN 1-93/3 which was detected in amounts of 6.1 % ITR in the total pond system and 5.5 % ITR in the entire creek system, respectively. Metabolite EN 1-101/4 was detected only in minor extent never exceeding 4.4 % ITR (in the entire system). Metabolites M1 and M2 are described below.

Validity criteria fulfilled:

yes

Remarks:

Criteria OECD Guideline 308

Conclusions:

DT50:
Water phase Pond:27d,; Creek :165d
Sediment: Pond :81d; Creek:36d
Entire System Pond: 55d; Creek: 54d

DT90:
Water phase Pond:91d; Creek : 549d
Sediment Pond :269d; Creek: 121d
Entire system Pond: 182; Creek 179d

Description of key information

The study dated 2006 provided the most reliable results and should be used for risk assessments. Piperonyl Butoxide was degraded from the entire system with DT₅₀ values calculated to be 54 and 55 days in creek and pond respectively at 20°C. The other study by Wiliams, 1991, used an agricultural soil and is therefore considered less reliable.

Key value for chemical safety assessment

Half-life in freshwater:

165 d

at the temperature of:

20 °C

Half-life in freshwater sediment:

81 d

at the temperature of:

20 °C