Diphenyl methylphosphonate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2011-12-16 - 2012-01-13

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

GLP compliance:

yes (incl. QA statement)

Remarks:

The Department of Health of the Government of the United Kingdom

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
No surrogate or analogue material was used.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: final effluent of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK
- Preparation of inoculum for exposure: The sample of effluent was filtered through coarse filter paper (first approx. 200 mL discarded) and the filtrate maintained on continuous aeration in a temperature controlled room at approx. 21 °C prior to use.

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of culture medium: Solution a: 8.50 g/L KH2PO4, 21.75 g/L K2HPO4, 33.40 g/L Na2HPO4.2H2O, 0.50 g/L NH4Cl (pH 7.4) / Solution b: 27.50 g/L CaCl2 / Solution c: 22.50 g/L MgSO4.7H2O / Solution d: 0.25 g/L FeCl3.6H2O / The "dilution water" was kept in a temperature controlled room , at approximately 21 °C, overnight and under gentle aeration prior to use. An aliquot (1 mL) of each solutions a to d was added to each litre of aerated reverse osmosis purified and deionised water (Elga Optima 15+ or Elga Purelab Option R-15 BP).
- Continuous darkness: yes
- Other: The culture medium used was recommended in the OECD Guideline.

TEST SYSTEM
- Culturing apparatus: 250 - 300 mL Biological Oxygen Demand (BOD) bottles (darkened glass) with ground glass stoppers
- Measuring equipment: YSI dissolved oxygen meter

SAMPLING
- Sampling frequency: Days 0, 3, 5, 7, 11, 14, 18, 21, 24 and 28 (control, reference and test item) / Days 0, 7 and 14 (toxicity control)
- Other: Dissolved oxygen concentrations in duplicate samples

CONTROL AND BLANK SYSTEM
- Inoculum blank: inoculated culture medium
- Toxicity control: Test item (2 mg/L) plus the reference item (1 mg/L) in inoculated culture medium. The reference item concentration was reduced to 1 mg/L in the toxicity control to prevent complete deoxygenation of the test media occurring.

Reference substance:

benzoic acid, sodium salt

Remarks:

Sigma Lot No. MKBC1469

Preliminary study:

No preliminary study was performed.

Test performance:

Neither unusual observations during the test performance nor any other information affecting results are reported.

Parameter:

% degradation (O2 consumption)

Value:

3

Sampling time:

28 d

Remarks on result:

other: No St.dev. available.

Details on results:

The oxygen depletion of the inoculated control did not exceed 1.5 mg O2/L after 28 days, the residual oxygen concentration in the test bottles remained at 3.80 mg O2/L or greater in all test vessels and the difference between the extremes of replicate oxygen depletion values at the end of the test was less than 20 % in all vessels (satisfying the validation criteria).
The toxicity control attained 25 % degradation after 14 days (confirming that the test item is not toxic to the microorganisms used in the test).

Results with reference substance:

The reference item attained 67 % degradation after 14 days and 76 % after 28 days (confirming the suitability of the test method and culture conditions).

Validity criteria fulfilled:

yes

Remarks:

Validity criteria of the applied guideline are fulfilled.

Interpretation of results:

not readily biodegradable

Conclusions:

The test material attained 3 % degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline 301D. The study was conducted under certificated GLP compliance and a well documented study report is available.

Executive summary:

The biodegradability of the test substance was investigated according to OECD guideline 301D, EU method C.4 -E and US EPA Fate, Transport and Transformation Test Guidelines OPPTS 835.3110 Paragraph (o) (Clarke, 2012). The study was conducted in compliance with the Principles of Good Laboratory Practice (GLP). A mixed population of sewage treatment microorganisms collected from the final effluent stage of the Severn Trent Water Plc (UK), which treats predominantly domestic sewage, was used as inoculum. Sodium benzoate (C6H5COONa) was used as reference substance.

The test material (2 mg/L) plus the reference substance (1 mg/L) in inoculated culture medium served as toxicity control. In this case the reference item concentration was reduced to 1 mg/L to prevent complete deoxygenation of the test media occurring. Furthermore, a blank (inoculated culture medium) was run in parallel. The test BOD bottles were firmly stoppered to exclude all air bubbles and incubated in darkness in a temperature controlled water bath at approximately 20 °C. Sodium benzoate attained 76 % degradation after 28 days thereby confirming the suitability of the test method and culture conditions. The toxicity control attained 25 % degradation at the end of the test which confirms that the test material was not toxic to the sewage treatment microorganisms used in this experiment. The test material attained 3 % degradation after 28 days and therefore cannot be considered to be "readily biodegradable" under the strict terms and conditions of OECD Guideline 301D. All validity criteria were fulfilled.

Description of key information

1. Experimental result: 3 % degradation in 28 days (Not readily biodegradable according to OECD 301D)
2. Calculation with BIOWIN v4.11 (EPIWIN software by US-EPA), overall ready biodegradation prediction: NO  

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

The biodegradability of the test substance was investigated experimentally according to OECD Guideline 301D, EU Method C.4-E and US EPA Fate, Transport and Transformation Test Guidelines OPPTS 835.3110 Paragraph (o) (Clarke, 2012). The study was conducted in compliance with the Principles of Good Laboratory Practice (GLP). A mixed population of sewage treatment microorganisms collected from the final effluent stage of the Severn Trent Water Plc (UK), which treats predominantly domestic sewage, was used as inoculum. Sodium benzoate (C6H5COONa) was used as reference substance. The test material (2 mg/L) plus the reference substance (1 mg/L) in inoculated culture medium served as toxicity control. In this case the reference item concentration was reduced to 1 mg/L to prevent complete deoxygenation of the test media occurring. Furthermore, a blank (inoculated culture medium) was run in parallel. The test BOD bottles were firmly stoppered to exclude all air bubbles and incubated in darkness in a temperature controlled water bath at approximately 20 °C. Sodium benzoate attained 76 % degradation after 28 days thereby confirming the suitability of the test method and culture conditions. The toxicity control attained 25 % degradation at the end of the test which confirms that the test material was not toxic to the sewage treatment microorganisms used in this experiment. The test material attained 3 % degradation after 28 days and therefore cannot be considered to be "readily biodegradable" under the strict terms and conditions of OECD Guideline 301D. All validity criteria were fulfilled.

Supporting information is given by predictions with the computer program BIOWIN v4.11 (EPIWIN software) by US-EPA.This program uses seven different models for its prediction: Linear Model, Non-linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model, and Anaerobic Model (called Biowin 1 – 7, respectively). Due to the overall results a prediction of the ready biodegradability is done for the desired chemical. This can only be predicted for organic substances.If the Biowin 3 result is given in weeks or even faster and the Biowin 5 probability is ≥ 0.5, then the overall prediction is “yes”, thus the substance will be considered as readily biodegradable. This procedure is based on application of Bayesian analysis to ready biodegradation data (for the detailed descriptions please refer to the “help” option of the software).Biowin 5 and 6 predict the ready biodegradability for degradation in the OECD Guideline 301C only and thereby using the database from the Chemicals Evaluation and Research Institute Japan (CERIJ). According to the Linear and also Non-linear Model the test substance is biodegrading fast. The Ultimate Biodegradation Timeframe is given in weeks to months, whereas the Primary Biodegradation Timeframe shows days to weeks for the substance. Both MITI Models predict that the substance is not readily biodegradable, which is also the prediction as overall result. Also under anaerobic conditions the substance is not suspected to be biodegraded fast. However, the linear and the non-linear model said that DPP will biodegrade fast, the ultimate timeframe is given as weeks to months, and a timeframe of days to weeks is given by the primary timeframe. Therefore, although DPP is not readily biodegradable, an ultimate biodegradability cannot be ruled out.