Pentaerythritol tetrakis(3-mercaptopropionate)

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Remarks:

Biodegradation in water: screening test, toxicity control is used to derive effect concentration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2007-11-13 to 2007-12-12

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

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)
The test item was a 5% aquatic dispersion.The concentration in the test assays were 2000 mg dispersion per litre mineral test medium and 400 mg dispersion per litre mineral test medium, respectively. 2000 mg test item correspond to 290 mg ThOD, 400 mg test item correspond to 58 mg ThOD.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Fresh samples of activated sludge are withdrawn on June 10th, 2014 from the sewage treatment plant Ruhrverband Kläranlage, Sunthelle 6, 57392 Schmallenberg, Germany, which is mainly fed with municipal wastewater. Since it was not necessary, the samples were not washed with mineral medium after the arrival at the laboratory but kept aerobic until use.The concentration used in the test was 29.6 mg dry mass/litre (7.39 mg dry mass/250 mL).

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

28 d

Details on test conditions:

TEST CONDITIONS
- Composition of medium:
( a )
KH2PO4: 8.50 g/L
K2HPO4: 21.75 g/L
Na2HPO4 x 12 H2O: 67.13 g/L
NH4Cl: 0.50 g/L
adjusted to 7.4 ± 0.2 with H2SO4 (50 g/L)
( b )
CaCl2 x 2 H2O: 36.40 g/L
( c ) MgSO4 x 7 H2O: 22.50 g/L
( d ) FeCl3 x 6 H2O: 0.25 g/L.
The mineral medium applied in the test contained 10 mL/L of mineral stock solution a and 1 mL/L of the mineral stock solution b–d, respectively.
- Test temperature: 22 °C
- pH: 7.4 +/- 0.2
- pH adjusted: no
- Continuous darkness: yes

TEST SYSTEM
- Test vessel: 500 mL glass vessels, fill volume 250 mL
- Aeration: yes
- Number of culture flasks/concentration: 2 vessels containing test item (2000 mg/L) and inoculum; 2 vessels containing test item (400 mg/L) and inoculum; 2 vessels containing only inoculum; 2 vessels containing test item (2000 mg/L) and a sterilising agent
- Method used to create aerobic conditions: The suspension was aerated during the whole test.
- Measuring equipment: SAPROMAT respirometer (VOITH Inc.).

SAMPLING
- Sampling frequency: The measurement and recording of the oxygen demand was carried out continuously

CONTROL AND BLANK SYSTEM
- Inoculum blank: The blank control consists of inoculated mineral medium only
- Abiotic sterile control: An abiotic control containing test item at 2000 mg per litre sterilized mineral test medium was applied. The assay was sterilized by adding HgCl2.
- Toxicity control: A toxicity control containing test item at 2000 mg per litre and reference item at 100 mg per litre mineral test medium was applied.

STATISTICAL METHODS:
Theoretical Oxygen Demand (ThOD):
The Theoretical Oxygen Demand (ThOD) was calculated on the basis of the sum formula of the test and reference item by:
ThOD [g/g] = 16 * (2 C + 1/2 H + 5/2 N + 1/2 Na – O) / Molecular weight.
The ThOD values for Na-benzoate, the test item and the toxicity control were determined as follows:
ThODPC-2014-536: 0.145 mg O2/mg test item
ThODNa-Benzoate: 1.665 mg O2/mg reference item
ThODtoxicity control: 0.218 mg O2/mg substance mixture
Biochemical Oxygen Demand (BOD):
The Biochemical Oxygen Demand (BOD) was calculated on the basis of the test raw data by BOD [mg/mg] = mg O2 uptake corrected by blank per mg test item.
The percent degradation was calculated according to the following formula:
Dt = [(Ct –Cb) / ThOD] x 100Dt: degradation (%) at time t;
Ct: mean oxygen consumption (mg/L) in the test suspension at time t;
Cb: mean oxygen consumption (mg/L) in the blanks at time t;
ThOD: Theoretical oxygen demand of the test suspension (mg/L).

Duration:

14 d

Dose descriptor:

IC0

Effect conc.:

23.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: tox control of OECD301, inhibition of degradation of sodium benzoate

Validity criteria fulfilled:

yes

Conclusions:

inocculum

Executive summary:

The toxicity of PETMP to microorganisms was investigated during a ready biodegradation study according to OECD 301 B (CO2 evolution).

The test material, at a concentration of 10 mg C/L, was exposed to activated sewage sludge micro-organisms with culture medium in sealed culture vessels in the dark at approximately 21°C for 28 days. In view of the difficulties associated with the evaluation of the biodegradability of organic compounds with low water solubility, a modification to the standard method of preparation of the test concentration was performed: Following the recommendations of the International Standards Organisation (ISO 1995) and the published literature (Handley et al. 2002), the test material was adsorbed onto granular silica gel prior to dispersion in the test medium to aid dispersion of the test material in the test medium and to increase the surface area of the test material exposed to the test organisms. The degradation of the test material was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the standard material, sodium benzoate were used for validation purposes.

The respiration of sodium benzoate by inocculum was determined as toxicity control.

The biodegradation of the item mixture in the toxicity control was found to be 31.1% after 14 days of incubation. Thus, according to the test guidelines, the test item had no inhibitory effect on activated sludge microorganisms at the tested concentration of 2000 mg/L, as the biodegradation in the toxicity control was higher than 25% within 14 days of incubation.

Description of key information

PETMP at a concentration of 23.9mg/l has no inhibitory effect on the respiration of sodium benzoat by sewage sludge inocculum.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

23.9 mg/L

Additional information

The toxicity of PETMP to microorganisms was investigated during a ready biodegradation study according to OECD 301 B (CO2 evolution).

The test material, at a concentration of 10 mg C/L, was exposed to activated sewage sludge micro-organisms with culture medium in sealed culture vessels in the dark at approximately 21°C for 28 days. In view of the difficulties associated with the evaluation of the biodegradability of organic compounds with low water solubility, a modification to the standard method of preparation of the test concentration was performed: Following the recommendations of the International Standards Organisation (ISO 1995) and the published literature (Handley et al. 2002), the test material was adsorbed onto granular silica gel prior to dispersion in the test medium to aid dispersion of the test material in the test medium and to increase the surface area of the test material exposed to the test organisms. The degradation of the test material was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the standard material, sodium benzoate were used for validation purposes.

The respiration of sodium benzoate by inocculum was determined as toxicity control.

The biodegradation of the item mixture in the toxicity control was found to be 31.1% after 14 days of incubation. Thus, according to the test guidelines, the test item had no inhibitory effect on activated sludge microorganisms at the tested concentration of 2000 mg/L, as the biodegradation in the toxicity control was higher than 25% within 14 days of incubation.