Reaction products of triphenyl phosphite and isodecanol (1:2)

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:

weight of evidence

Study period:

2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline/GLP study

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

a) ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification (omission does not result in nitrogen limitation as shown by the biodegradation of the reference compound), and b) river water instead of an effluent.

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water

Details on inoculum:

River water was sampled from the Rhine near Heveadorp, The Netherlands (19-03-2014). The nearest plant (Arnhem-Zuid) treating domestic wastewater biologically was 3 km upstream. The river water was aerated for 7 days before use to reduce the endogenous respiration (van Ginkel and Stroo, 1992). River water without particles was used as inoculum. The particles were removed by sedimentation after 1 day while moderately aerating.

Duration of test (contact time):

42 d

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Parameter followed for biodegradation estimation:

other: Theoretical Oxygen Demand (ThOD)

Details on study design:

The Closed Bottle test (OECD TG 301) was performed according to the study plan. The study plan was develo¬ped from ISO Test Guidelines (1994). Use was made of 10 bottles con¬taining only river water, 6 bottles con¬taining river water and sodium acetate, 10 bottles con¬taining river water with test substance and surfactant, and 10 bottles containing river water with surfactant. The con¬centrations of the test substance, surfactant and sodium ace¬tate in the bottles were 2.0, 2.0 and 6.7 mg/L, res¬pectively. Each of the prepared solutions was dispensed into the respective group of BOD bottles so that all bottles were com¬pletely filled without air bubbles. The zero time bottles were immediately analyzed for dissolved oxygen using an oxygen electrode. The remaining bot¬tles were closed and incubated in the dark. Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at day 7, 14, 21, and 28. One extension from the protocol of the Closed Bottle test was intro¬duced. The Closed Bottle test was prolonged by measuring the course of the oxygen decrease in the bottles of day 28 using a spe¬cial funnel. This funnel fitted exactly in the BOD bottle. Subsequently, the oxygen electrode was inserted in the BOD bottle to measure the oxy¬gen concentration. The medium dissipated by the electrode was collected in the funnel. After with¬drawal of the oxygen electrode the medium collected flowed back into the BOD bottle, followed by removal of the funnel and closing of the BOD bottle (van Ginkel and Stroo 1992).

Reference substance:

acetic acid, sodium salt

Preliminary study:

Theoretical oxygen demand (ThOD)The calculated theoretical oxygen demand (ThOD) of triisotridecyl phosphite is 3.0 mg/mg. The ThOD of sodium acetate is 0.8 mg/mgToxicityInhibition of the degradation of a well-degradable compound, e.g. sodium acetate by the test substance in the Closed Bottle test was not determined because possible toxicity of triisotridecyl phosphite to microorganisms degrading acetate is not relevant. Inhibition of the endogenous respiration of the inoculum by the test substance at day 7 was not detected (Table I). Therefore, no inhibition of the biodegradation due to the "high" initial test substance concentration is expected.

Test performance:

Validity of the testThe validity of the test is demonstrated by an endogenous respiration of 1.3 mg/L at day 28. Furthermore, the differences of the replicate values at day 28 were less than 20%. The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 80. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Parameter:

% degradation (O2 consumption)

Value:

30

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

38

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

47

Sampling time:

21 d

Parameter:

% degradation (O2 consumption)

Value:

57

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

63

Sampling time:

42 d

Dissolved oxygen concentrations (mg/L) in the closed bottles.

Time (days)	Oxygen concentration (mg/L)
	Ocs	Ot	Oc	Oa
0	8.9	8.9	8.9	8.9
	8.9	8.9	8.9	8.9
Mean (M)	8.9	8.9	8.8	8.9
7	7.8	6.0	8.1	4.0
	7.9	6.2	8.1	3.9
Mean (M)	7.9	6.1	8.1	4.0
14	7.5	5.3	7.7	3.3
	7.4	5.0	7.7	3.4
Mean (M)	7.5	5.2	7.7	3.4
21	7.5	4.4	7.7
	7.3	4.7	7.6
Mean (M)	7.4	4.6	7.7
28	7.3	4.0	7.5
	7.2	3.8	7.6
Mean (M)	7.3	3.9	7.6
42	6.8	2.9
	6.7	3.1
Mean (M)	6.8	3.0

O_cs      River water with nutrients and surfactant.

O_t       River water with nutrients, and test material (2.0 mg/L) emulsified with surfactant.

O_c       River water with nutrients.

O_a       River water with nutrients and sodium acetate (6.7 mg/L).

Oxygen consumption (mg/L) and the percentages biodegradation of the test substance, triisotridecyl phosphite (BOD/ThOD) and sodium acetate (BOD/ThOD) in the Closed Bottle test.

Time (days)	Oxygen consumption (mg/L)		Biodegradation (%)
	Test substance	Acetate	Test substance	Acetate
0	0.0	0.0	0	0
7	1.8	4.1	30	76
14	2.3	4.3	38	80
21	2.8		47
28	3.4		57
42	3.8		63

 

 

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

Triisotridecyl phosphite was biodegraded by 57% at day 28 in the Closed Bottle test. In the prolonged Closed Bottle test this substance was biodegraded by 63% at day 42. Although triisotridecyl phosphite cannot be classified as readily biodegradable, the biodegradation reached at the last day of the test demonstrates that this substance is inherently biodegradable and not persistent.

Executive summary:

Triisotridecyl phosphite was biodegraded by 57% at day 28 in the Closed Bottle test. In the pro­longed Closed Bottle test this substance was biodegraded by 63% at day 42. Although triisotridecyl phosphite cannot be classified as readily biodegradable, the bio­degradation reached at the last day of the test demonstrates that this substance is inherently biodegradable and not persistent.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study following current guideline.

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

1 minor deviation; the omission of ammonium chloride from the medium to prevent oxygen consumption due to nitrification

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Obtained from wastewater treatment plant Nieuwgraaf in Duiven, Netherlands The plant treats predominantly domestic wastewater. The activated sludge was preconditioned to reduce the endogenous respiration rates by aeration for one week.

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

formulation

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

The Closed Bottle test was performed according to the study plan. The study plan was developed from ISO Test Guidelines (1994). Use was made of 10 bottles containing only inoculum, 10 bottles containing inoculum, silica gel and test substance, 10 bottles containing inoculum, and silica gel, and 6 bottles containing sodium acetate, and inoculum. The concentrations of the test substance, and sodium acetate in the bottles were 2.0, and 6.7 mg/L, respectively. Each of the prepared solutions was dispensed into the respective group of BOD bottles so that all bottles were completely filled without air bubbles. The zero time bottles were immediately analyzed for dissolved oxygen using an oxygen electrode. The remaining bottles were closed and incubated in the dark. Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at day 7, 14, 21, and 28.

Reference substance:

acetic acid, sodium salt

Preliminary study:

Results of a preliminary study lead to the use of activated sludge with silica carrier agent.

Test performance:

Triphenyl phosphite is biodegraded by 84% at day 28 in the Closed Bottle tes). Over 60% biodegradation was achieved after approximately 6 days immediately
following the attainment of 10% biodegradation. The test substance therefore fulfilled the time window criterion for ready biodegradable substances. Hence, the test substance is classified as readily biodegradable.

Parameter:

% degradation (O2 consumption)

Value:

70

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

75

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

80

Sampling time:

21 d

Parameter:

% degradation (O2 consumption)

Value:

84

Sampling time:

28 d

Theoretical oxygen demand (ThOD)

The calculated theoretical oxygen demand (ThOD) of triphenyl phosphite is 2.2 mg/mg. The ThOD of sodium acetate is 0.8 mg/mg

Toxicity

Inhibition of the degradation of a well-degradable compound, e.g. sodium acetate by the test substance in the Closed Bottle test was not determined because possible toxicity of triphenyl phosphite to microorganisms degrading acetate is not relevant. Inhibition of the endogenous respiration of the inoculum by the test substance at day 7 was not detected . Therefore, no inhibition of the biodegradation due to the "high" initial test substance concentration is expected.

Test conditions

The pH of the media was 7.3 at the start of the test. The pH of the medium at day 28 was 7.3 (both controls), and 7.1 (test). Temperatures were within the prescribed temperature range of 22 to 24°C.

Validity of the test

The validity of the test is demonstrated by an endogenous respiration of 0.9 mg/L at day 28. Furthermore, the differences of the replicate values at day 28 were less than 20%. The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 83%. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Validity criteria fulfilled:

yes

Remarks:

The validity of the test is demonstrated by an endogenous respiration of 0.9 mg/L at day 28 (Table I). Furthermore, the differences of the replicate values at day 28 were less than 20%. The biodegradation percentage of the reference compound, sodium aceta

Interpretation of results:

readily biodegradable

Conclusions:

The results of the study show TPP is readily biodegradable meeting both the overall and 10-window criteria.

Executive summary:

TPP was 84% biodegradable in a 28 -day ready biodegradation study using OECD 301D (closed bottle test). The results also passed the 10 -day window of 60% biodegradation during the first week of the study. TPP will be classified as readily biodegradable based on these results.

Description of key information

Alkyl/phenyl phosphites are considered to be readily biodegradable based on several lines of evidence:

1) They hydrolyse rapidly in water and their hydrolysis products - isoalkyl alcohols and phenol - are readily biodegradable.

2) Recent biodegradation studies that employ methods to make the phosphite test material more soluble (i.e. more bioavailable) have shown ready biodeg results.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater