Phosphinylidynetrimethanol

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Remarks:

Toxicity control from study on ready biodegradability (301F)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2020-01-08 - 2020-04-27

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted under GLP on the registered substance itself according to OECD guideline 301F without deviations. Hence, the available data is reliable, although the test design did not directly aim to cover the present endpoint.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: OECD 301F

Version / remarks:

OECD Guideline for Testing of Chemicals No. 301 F: "Ready Biodegradability: Manometric Respirometry Test", adopted July 17, 1992

Qualifier:

according to guideline

Guideline:

other: EU Method C.4-D

Version / remarks:

Commission Regulation 440/2008/EC, Method C.4-D of May 30, 2008: Manometric Respirometry Test (EEC Publication No. L 142/496, May 2008)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: 25.2 mg test item (corresponding to 17.5 mg active ingredient of THPO) were directly weighed into the test flasks containing 25.0 mg of the reference item sodium benzoate, 242 mL test water and 2 mL activated sludge. The concentration of the stock suspension of the activated sludge was 3.5 g/L on dry matter base, resulting in a final sludge concentration of 28.7 mg sludge/L in the test flasks. No emulsifiers or solvents were used, but the solutions were dispersed by stirring to achieve a homogeneous solution of the test item.
- Controls: Inoculumn control including test water and inoculum
- Evidence of undissolved material (e.g. precipitate, surface film, etc): none noted

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Aerobic activated sludge, microorganisms from a domestic waste water treatment plant was supplied by the sewage treatment plant Rossdorf, Germany.
- Preparation of inoculum for exposure: The aerobic activated sludge used for this study was
deposited for 30 min, washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in test water and centrifuged again. This procedure was done three times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 3.5 g dry material per litre were mixed with test water and aerated. This suspension was used for the experiment.
- Initial biomass concentration: The concentration of the stock suspension of the activated sludge was 3.5 g/L on dry matter base. The final sludge concentration in the test flasks was 28.7 mg sludge/L.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

28 d

Hardness:

not specified

Test temperature:

19°C

pH:

pH-value of test solutions:
7.6 (measured at the start of the test)
7.6 to 7.7 (measured at the end of the test)

Nominal and measured concentrations:

104.1 mg test item/L corresponding to 72.3 mg active ingredient of THPO/L (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel: Test flasks
- Type (delete if not applicable): The test flasks were closed gas-tight by a measuring head.
- Material, size, headspace, fill volume: 500 mL total volume, approximately 244 mL fill volume
- Aeration: yes
- No. of vessels per concentration (replicates): 1 (containing test item, reference item, activated sludge and test water)
- No. of vessels per control (replicates): 2 (containing activated sludge and test water)
- No. of vessels per abiotic control (replicates): 1 (containing test item, activated sludge and test water)
- Sludge concentration (weight of dry solids per volume): The final sludge concentration in test flasks was 28.7 mg sludge/L.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Reconstituted water (please see "Any other information on materials and methods incl. tables" for details on the composition and preparation of the test water)

OTHER TEST CONDITIONS
- Adjustment of pH: not necessary
- Photoperiod: Darkness
- Other: The closed test flasks were incubated in a climatised chamber under continuous stirring.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : The pressure decrease in the reaction vessels was measured over complete experimental phase of 28 days using the BSB/BOD-Sensor-System. The test flasks were closed gas-tight by a measuring head. Potassium hydroxide solution (45%) was used for trapping the produced carbon dioxide. The amount of O2 consumed by the activated sludge was calculated from the decrease of pressure in the reaction vessel.

In addition test conditions were recorded continuously with suitable instruments, documented in the raw data and reported in the final report. The temperature was recorded by means of the automated software AMR Wincontrol©. pH-values were measured in procedure control, a separately prepared test flask with test item (to prevent loss of test item in the test flasks) and a separately prepared test flask without test item (control) at test start and in all flasks at the end of the test, except in the abiotic and toxicity control, using a pH-electrode WTW pH 340i.

Reference substance (positive control):

yes

Remarks:

Sodium benzoate (purity 100%) was used as reference item

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 72.3 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: biodegradation

Remarks on result:

other: see Remarks

Remarks:

The toxicity control (containing the test item and the reference item sodium benzoate) of the presented study on biodegradation according to OECD 301F attained 55 % degr. after 14 d and 61 % degr. after 28 d of incubation, confirming that the test material was not toxic to the sewage treatment micro-organisms used in the study.

Biodegradation in the Toxicity Control

In the toxicity control containing both, the test item and the reference item sodium benzoate, 55% (ThODNH₄) biodegradation was noted within 14 days and 61% (ThODNH₄) biodegradation after 28 days of incubation.

According to the test guidelines the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was >25% within 14 days.

Validity Criteria

Inoculumn control: The oxygen demand of the inoculum control was 15 mg O₂/L and thus not greater than 60 mg O₂/L within 28 days as required by the test guideline.

pH-value: The pH-value of the test item flasks at the end of the test was 7.6 and therefore within the range of pH 6.0 to 8.5 as required by the test guideline.

Reference item: The percentage degradation of the reference item should reach the level for ready biodegradability (>60%) within 14 days as required by the test guideline. The reference item sodium benzoate was degraded to more than 60% after 10 days of incubation.

Test item: The difference of duplicate values for the degradation of the test item at the plateau, at the end of the test was less than 20%. The difference of duplicate values at day 28 was 13%. The validity criterion was fulfilled.

Toxicity Control: If in a toxicity test, containing both the test item and a reference item less than 25% biodegradation (based on ThODNH₄) occurred within 14 days, the test item can be assumed to be inhibitory. The biodegradation was 55% at day 14; the test item was not inhibitory.

Validity criteria fulfilled:

yes

Conclusions:

The available data were extracted from a study conducted under GLP on the registered substance itself according to OECD guideline 301F without deviations. The available data in general is as such fully reliable, however, test design did not directly aim to cover the present endpoint. Nevertheless the study was well performed and suffices to support the data within the key study. Based on the obtained results the test substance is not toxic to microorganisms at concentrations ≥ 72.3 mg active ingredient/L over 28 days with an EC0 and NOEC of ≥ 72.3 mg/L.

Executive summary:

The biodegradability of the test substance was investigated according to OECD Guidelines for Testing of Chemicals (1992) No 301 F, "Manometric Respirometry Test" referenced as Method C.4-D of Commission Directive 92/69/EEC (which constitutes Annex V of Council Directive 67/548/EEC). The study was conducted in compliance with the Principles of Good Laboratory Practice (GLP). The study was performed including a toxicity control containing the test substance and the reference substance sodium benzoate beside the aerobic activated sludge from a domestic sewage treatment plant and test water. Within this toxicity control the test item was exposed to the sewage treatment micro-organisms at a concentration of 72.3 mg active ingredient/L in a manometric test system at 19°C for 28 days. The degradation of the test material was assessed by the determination of the amount of oxygen consumed. Based on the obtained results the toxicity control attained 55 % biodegradation after 14 days and 61 % degradation after 28 days of incubation. If degradation in the toxicity flask is below 25 % after 14 days, the test item can be considered as toxic towards the inoculum. Accordingly, the test material was not toxic to the sewage treatment microorganisms used in this experiment and the EC₀ as well as the NOEC were determined to be ≥ 72.3 mg/L over 28 days.

Description of key information

NOEC (28d) for microorganisms: 72.3 mg/l  [nominal; based on biodegradation; OECD 301F]

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

72.3 mg/L

Additional information

The biodegradability of the test substance was investigated according to OECD Guidelines for Testing of Chemicals (1992) No 301 F, "Manometric Respirometry Test" referenced as Method C.4-D of Commission Directive 92/69/EEC (which constitutes Annex V of Council Directive 67/548/EEC). The study was conducted in compliance with the Principles of Good Laboratory Practice (GLP) and a reliability score of 2 was awarded in accordance with the criteria set forth by Klimisch et al. (1997).

The study was performed including a toxicity control containing the test substance and the reference substance sodium benzoate beside the aerobic activated sludge from a domestic sewage treatment plant and test water. Within this toxicity control the test item was exposed to the sewage treatment micro-organisms at a concentration of 72.3 mg active ingredient/L in a manometric test system at 19°C for 28 days. The degradation of the test material was assessed by the determination of the amount of oxygen consumed. Based on the obtained results the toxicity control attained 55 % biodegradation after 14 days and 61 % degradation after 28 days of incubation. If degradation in the toxicity flask is below 25 % after 14 days, the test item can be considered as toxic towards the inoculum. Accordingly, the test material was not toxic to the sewage treatment microorganisms used in this experiment and the EC₀as well as the NOEC were determined to be ≥ 72.3 mg/L over 28 days.