[1,3-phenylenebis(1-methylethylidene)]bis[tert-butyl] peroxide

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

Data waiving:

other justification

Justification for data waiving:

other:

Reference 2

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

August 2008 to May 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: 1a: GLP guideline study

Justification for type of information:

see read across rationale in Section 13.2

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

EPA Subdivision N Pesticide Guideline 162-3 (Anaerobic Aquatic Metabolism)

Deviations:

not specified

GLP compliance:

yes

Radiolabelling:

no

Oxygen conditions:

anaerobic

Inoculum or test system:

natural water / sediment

Details on source and properties of surface water:

Sediment and pond water were collected on september 15, 2008 from Refugio Park Pond in Hercules, California and received at the laboratory on the same day. The test system was refrigerated in the dark until use.

pH: 8.1
Calcium: 263 ppm
Mg: 122 ppm
Na: 287 ppm
Hardness: 1168 mg eq. CaCO3/L
Conductivity: 2.48 mmhas/cm
Sodium Absorption Ratio (SAR): 3.67
Total Dissolved Solids: 2386 ppm
Turbidity: 10.0 NTU
Dissolved Oxygen: 9.7 mg/L

Details on source and properties of sediment:

Sediment and pond water were collected on september 15, 2008 from Refugio Park Pond in Hercules, California and received at the laboratory on the same day. The test system was refrigerated in the dark until use.

Sediment: described as a loam soil (Agvise Laboratories, Inc.), was passed throught a 2 mm sieve then stored in plastic bags.

Sand: 46%
Silt: 38%
Clay: 16%
USDA textural class: loam
bulk density: 0.95
CEC (meq/100g): 15.4
% moisture at 1/3 bar: 20.1
% oragnic matter: 3.1
ph in 1:1 soil:water ratio: 7.8

Duration of test (contact time):

90 d

Initial conc.:

1 other: µg/g (dry soil weight) (1.0 ppm)

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

Preparation of Test System
 
The Test System consisted of the test substance applied to 30 g dry weight equivalent of sediment flooded with 120 mL of pond water. Samples were prepared by combining approximately 53.43 g wet weight of sediment (30 g dry weight equivalent) and pond water to a final volume of 120 mL. The samples were prepared in amber bottles with Teflon-lined septum caps. A total of 31 samples were prepared.
 
The anaerobicity of the samples was checked by measuring the dissolved oxygen and redox potential of random samples. All samples were pre-incubated at 25°C for 4 weeks under anoxic conditions prior to test application.

Preparation of test substance, chemical application
 
Concentration of the dose solution: 290.3 µg/mL.
 The dosing was carried out under a nitrogen atmosphere (nitrogen stream above the dosing area).
 100µL aliquot of the dosing solution was added to 12 previously prepared sediment/water samples by unscrewing the cap and adding the dosing solution directly into the water layer. Nitrogen was bubbled through the water layers of each sample after dosing. Caps were replaced immediately and the bottles were placed in an incubator after dosing and maintained at 25°C in the dark (samples were maintained in the dark at 25 +/- 1°C for up to 90 days).

Sampling:
duplicate dosed samples were removed for sampling and analysis at each time interval (0, 7, 13, 69 and 90 days), processed and axtracted the same day of collection.
Water layer was separated by centrifugation
solutions were filtered (0.45 µm nylon filters) prior to analysis.

Sediment layer was extracted with acetonitrile and filtered (0.45 µm nylon filters) prior to analysis.

Statistics
Averages, linear regression, standard deviation, relative tandard deviation and relative error were the only statistical methods employed (Microsoft Excel)

Reference substance:

not specified

Compartment:

other: water, material (mass) balance

% Recovery:

1

Compartment:

other: sediment, material (mass) balance

% Recovery:

94.7

% Degr.:

ca. 30

Parameter:

test mat. analysis

Sampling time:

7 d

% Degr.:

ca. 30

Parameter:

test mat. analysis

Sampling time:

13 d

% Degr.:

ca. 80

Parameter:

test mat. analysis

Sampling time:

69 d

% Degr.:

> 90

Parameter:

test mat. analysis

Sampling time:

90 d

Compartment:

entire system

DT50:

29 d

Type:

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

Remarks on result:

other: r²=0.991

Remarks on result:

other: DT90=96.3 days

Transformation products:

yes

No.:

#1

Details on transformation products:

tert-butanol was detected in the sediment and water layers for all time points after 0, but the amount was below quantifiable limits for all except Day 90 samples. in the day 90 sediment layers, tert-butanol was detected but below the limit of quantification. in water layers, an average of 8.3 µg were recovererd in the water extracts. the mass of tert-butanol in the system at day 90 is equivalent to 61.5%n yield from the initial test substance dose.

Evaporation of parent compound:

not specified

Volatile metabolites:

not specified

Residues:

not specified

Details on results:

pH were comprised between 7.13 and 8.11
O2 concentrations were comprised between 0.08 and 1.48 ppm
Eh values were comprised between -309 and 113

Validity criteria fulfilled:

not specified

Executive summary:

A study was conducted to determine the biodegradation of structurally analogous [1,3(or 1,4)-phenylenebis(1-methylethylidene)]bis[1,1-dimethylethyl] peroxide in water/sediment simulation test, according to US EPA guideline.

The substance was not found in the water layers at all time points. In the sediment layer, an average of 94.7% of the applied dose was detected at day 0. The substance has decreased to an average of 9.7% of the applied dose at day 90. The half-life in sediment/water sediment under anaerobic conditions was determined as 29 days.

Tert-butanol, the main expected breakdown product, was detected in water and sediment layers at all time point (except day 0) but below a quantifiable level until day 90: it represented an average of 61.5% of the test substance applied dose.

Description of key information

The ready biodegradability was evaluated in a study performed in accordance with OECD testing guideline 301 D and GLP requirements.

The test substance is not biodegraded in the closed bottle test, and thereforeshould not be classified as readily biodegradable. This lack of biodegradation is not due to toxicity of the test compound because the endogenous respiration is not inhibited by bis (tert-butyl peroxy isopropyl) benzene.

Sediment and water compartments exposure is likely. Besides, based upon the adsorption potential of the substance of interest,a study was conducted to determine the biodegradation of [1,3(or 1,4)-phenylenebis(1-methylethylidene)]bis[1,1-dimethylethyl] peroxide in water/sediment simulation test, according to US EPA guideline.

The substance was not found in the water layers at all time points. In the sediment layer, an average of 94.7% of the applied dose was detected at day 0. The substance has decreased to an average of 9.7% of the applied dose at day 90. The half-life in sediment/water compartment under anaerobic conditions was determined as 29 days.

Tert-butanol, the main expected breakdown product, was detected in water and sediment layers at all time point (except day 0) but below a quantifiable level until day 90: it represented an average of 61.5% of the test substance applied dose.

An aerobic mineralisation in surface water study (simulation biodegradation test) according to the OECD 309 Test Guideline is currently ongoing in accordance with the ECHA decision number SEV-D-2114369067-43-01/F.