Dimethyl (dimethoxyphosphinyl)succinate

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Type: mixed population of aquatic microorganisms (activated sludge)
- Origin: aeration tank of a wastewater plant treating predominantly domestic sewage (Wupper area water authority, WWTP Odenthal)
- Date of collection: 2017-04-18
- Concentration of inoculum: 30 mg/L suspended solids

Pre-treatment of the inoculum
− Before use, the inoculum was stored for two days at room temperature under continuous stirring with aeration.
− The sludge was washed twice by adding mineral medium and centrifuging for 10 min at 2000 rpm and 20 °C and decanting off the supernatant.
− An aliquot of the wet sludge was dried in order to determine the wet weight / dry weight ratio of the sludge and to prepare a stock suspension (activated sludge) of 3 g dw/L.
− The calculated amount of sludge, needed to achieve 300 mL of this stock suspension, was dissolved in mineral medium and then filled up to a defined end volume.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Pre-treatment of the test item:
- 25 mg of the test item were weighed on aluminum foil and added to the test flasks, filled with 200 mL of mineral medium
- volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg test item/L

Pre-treatment of the reference compound
- 25 mg of the reference compound sodium benzoate were weighed on aluminum foil and added to the test flasks, filled with 200 mL of mineral medium
- volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg reference compound /L

Pre-treatment of the toxicity control
- 25 mg of the test item and 25 mg of the reference compound were weighed on aluminum foil and added to the test flasks, filled with 200 mL of mineral medium
- flask volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg test item and reference compound/L

Exposure conditions
- Test volume: 250 mL
- Test apparatus: OxiTopControl System (WTW)
- Mixing: 1 magnetic stirrer per test vessel
- Incubation time: 28 days
- Incubation temperature: 22 ± 1 °C

Reference substance:

benzoic acid, sodium salt

Remarks:

Acros Organics, purity 99.9 %, batch no. A0357641

Parameter:

% degradation (O2 consumption)

Value:

13

Sampling time:

28 d

Details on results:

5 % degradation after 7 days
9 % degradation after 14 days
12 % degradation after 21 days

Validity criteria fulfilled:

yes

Remarks:

biodegradability reference compound ≥ 60 % 14 d; degradation of toxicity control > 25 % 14 d; end of test, at plateau or end of the 10-d window, biodegradation in parallels (test item) differ < 20 %; oxygen uptake blank ≤ 60 mg/L; pH independent

Interpretation of results:

not readily biodegradable

Conclusions:

For dimethyl (dimethoxyphosphinyl)succinate a degradation of 13 % was determined after 28 d. Therefore, dimethyl (dimethoxyphosphinyl)succinate is considered to be “Not Readily Biodegradable“.

Executive summary:

This study was designed to assess the ready biodegradability of dimethyl (dimethoxyphosphinyl)succinate and conducted in accordance with the Council Regulation (EC) No 440/2008, Method C.4-D “Manometric Respirometry Test“(2008). This test method is in all essential parts identical with OECD Guideline 301 F (adopted July 1992).

A suspension of dimethyl (dimethoxyphosphinyl)succinate in a mineral medium was inoculated and incubated at a constant temperature (22 ± 1 °C) for 28 d under aerobic conditions in the dark. During this period, degradation was followed by continuous automated BOD determinations.

Tests with dimethyl (dimethoxyphosphinyl)succinate were run in triplicate as well as the blank control (inoculum but without test item). A reference compound (sodium benzoate) was run parallel in duplicate to check the operation of the procedures.

A toxicity control (test item and reference compound mixed, one replicate) was run in parallel, to ensure that the chosen concentration of the test item was not inhibitory to microorganisms.

Dimethyl (dimethoxyphosphinyl)succinate showed 13 % degradation after 28 days. Therefore, dimethyl (dimethoxyphosphinyl)succinate is considered to be “Not Readily Biodegradable“.

The reference compound sodium benzoate showed 94 % degradation after 14 days.

Description of key information

A study was designed to assess the ready biodegradability of dimethyl (dimethoxyphosphinyl)succinate and conducted in accordance with the Council Regulation (EC) No 440/2008, Method C.4-D “Manometric Respirometry Test“(2008).

For dimethyl (dimethoxyphosphinyl)succinate a degradation of 13 % was determined after 28 d. Therefore, dimethyl (dimethoxyphosphinyl)succinate is considered to be “Not Readily Biodegradable“.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed