bis(O,O-2-ethylhexyl-thiophosphoryl)polysulfide

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1998-11-03 - 1998-12-01

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)

Version / remarks:

according to Council Directive 92/69 EEC

Deviations:

no

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): secondary effluent of a domestic sewage treatment plant (Kläranlage Odenthal)
- Preparation of inoculum for exposure: aeration for 4 days
- Pretreatment: separation of coarse particles by filtration
- Concentration of sludge: 5 mL/L
- Water filtered: no
- Type and size of filter used, if any: coarse fluted filter

Duration of test (contact time):

28 d

Initial conc.:

2.5 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Test temperature: 20±1°C
- Continuous darkness: yes

TEST SYSTEM
- Number of culture flasks/concentration: 10

SAMPLING
- Sampling frequency: weekly

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes

Reference substance:

aniline

Remarks:

2.0 mg/L

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Results with reference substance:

With the reference substance aniline a degradation of 98 % was achieved within 14 days.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The study was conducted under GLP according to EU method C.4E on the registered substance itself with marginal deficiencies in documentation in the test report; the available information allows to draw the conclusion that the test was conducted properly without deviation from the guideline. The method is considered reasonable, the reference substance produced the appropriate response and the validity criteria are met. Hence, the results can be considered as reliable to assess the ready biodegradability of bis(O,O-2-ethylhexyl-thiophosphoryl)polysulfide by sludge retrieved from the secondary effluent of a domestic sewage treatment plant. Within the test period of 28 days, a degradation of 0 % was determined for bis(O,O-2-ethylhexyl-thiophosphoryl)polysulfide. Hence, the test item has to be classified as "Not Readily Biodegradable".

Executive summary:

In a study according to EU method C.4E under GLP, 2.5 mg/L bis(O,O-2-ethylhexyl-thiophosphoryl)polysulfide is suspended in a mineral medium, inoculated with a mixed population of aquatic microorganisms (secondary effluent of a domestic sewage treatment plant) and incubated for 28 days under aerobic conditions in the dark at 20 ± 1°C. During this period, the biodegradation of the test substance is determined on the basis of the reduction of dissolved oxygen.

Within the test period of 28 days, a degradation of 0 % was determined for bis(O,O-2-ethylhexyl-thiophosphoryl)polysulfide.

In parallel preparations with the reference substance aniline a degradation of 98 % was achieved within 14 days.

Accordingly, bis(O,O-2-ethylhexyl-thiophosphoryl)polysulfide has to be classified as "Not Readily Biodegradable".

This biodegradation study is classified as acceptable and satisfies the guideline requirement for a biodegradation study (closed bottle test).

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1996-10-29 - 1996-11-26

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

Deviations:

not specified

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

- Concentration of sludge: 30 mg/L

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: not specified
- Test temperature: 25 +/- 1 °C
- pH: 7.0 at test start, 7.0 - 8.2 at test end

TEST SYSTEM
- Culturing apparatus: Bottles
- Number of culture flasks/concentration: 2 (test substance + sludge + basal medium)

CONTROL AND BLANK SYSTEM
- Inoculum blank: 1 (sludge + basal medium)
- Toxicity control: 1 (aniline + sludge + basal medium

Reference substance:

aniline

Remarks:

100 mg/L

Parameter:

% degradation (O2 consumption)

Value:

10

Sampling time:

28 d

Results with reference substance:

With the reference substance aniline a degradation of 74 % was achieved within 14 days.

Results

Measured values (day 28)

	Bottle No.		Theoretical value
	3*	4*
BOD, mg	6.5	6.8	66.5
DOC, mg/L	9.8	3.0	46.5

 * value corrected with BOD or DOC value of Bottle 2 (= inoculum blank).

Degradabilities (%)

	Bottle No.		average
	3	4
BOD	10	10	10
DOC	NA**	NA**	NA**

 ** not calculated because the test substance was not dissolved in the test solution.

Validity criteria fulfilled:

not specified

Interpretation of results:

not readily biodegradable

Conclusions:

The study was conducted on accepted methods, i.e. MITI-Test, on the substance itself with deficiencies in documentation. The method is to be considered scientifically reasonable and suitable for the test item, the toxicity control showed the appropriate results. Hence, the results can be considered as sufficient to assess ready biodegradability of bis[bis[(2-ethylhexyl)oxy]phosphinothioyl] by supporting the information as provided in the key study. The test item attained 10 % biodegradation after 28 days and therefore cannot be considered as readily biodegradable. This results is consistent with the one of the key study (0 % degradation after 28 days), clearly showing that bis[bis[(2-ethylhexyl)oxy]phosphinothioyl] is not readily biodegradable according to the recent OECD Guidelines.

Executive summary:

The biodegradability of bis[bis[(2-ethylhexyl)oxy]phosphinothioyl] was examined at a concentration of 100 mg/L in a MITI-Test (non-GLP) according to the Chemical Substances Control Law (Japanese Law 117, 1973). The degradation parameter was the biochemical oxygen demand (BOD) in the samples. After 28 days incubation 10 % degradation had occured. Due to this result bis[bis[(2-ethylhexyl)oxy]phosphinothioyl] can be considered as not readily biodegradable. Aniline was used as reference substance. After 14 days incubation the reference substance is degraded 74 % within the 14d-window, confirming the inoculum and the test set-up to be appropriate.

Description of key information

Biodegradation in water: screening tests: Not readily biodegradable: 0% (BOD) in 28 days (EU method C.4 -E, GLP)

Biodegradation in water: screening tests:  Not readily biodegradable: 10% (BOD) in 28 days (MITI-Test, non-GLP)

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

There are two studies available to determine the ready biodegradability of bis[bis[(2-ethylhexyl)oxy]phosphinothioyl]. The key study was assessed with Klimisch 2 (EU method C.4 -E), the supporting (MITI-Test) as Klimisch 4. Both studies showed consistently that bis[bis[(2-ethylhexyl)oxy]phosphinothioyl] is not readily biodegradable (0% resp. 10% after 28 days based on BOD), leaving no doubt that the results are reliable. Hence, the endpoint is sufficiently covered, no data gaps were identified.