Propane-1-thiol

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

Remarks:

GLP-compliant with the exception of analysis of the substance. Guideline study, available as an unpublished report. Reliable without restrictions.

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

Deviations:

no

Principles of method if other than guideline:

- Deviation from GLP: As analysis for homogeneity, concentration or stability were not required in the test guidelines, these were not carried out

GLP compliance:

yes (incl. QA statement)

Remarks:

With the exception of analysis though this not considered to have affected the purpose or integrity of the study

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic, non-adapted

Details on inoculum:

- Inoculum: Mixed population of sewage treatment micro-organisms
- Retrieval date: 2011-08-19
- Source: Final effluent stage of Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK
- Preparation: Continuous aerated filtrate from a coarse filter paper (first 200 mL discarded) kept at 21°C until use
- Addition to test media: Micro-organisms were added to test vessels at a rate of 1 drop per litre

Duration of test (contact time):

28 d

Initial conc.:

1 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

- Culture media: OECD recommended
- Vehicle: None, the substance was dissolved directly in the culture medium
- Solution preparation: A 1000 mg/L stock solution was prepared by ultrasonicating 100 mg substance was dissolved in the test media for approximately 15 minutes and adjusting the volume. The stock solution was inverted several times and 6 mL were dispersed in the inoculated culture media to give a test concentration of 1.0 mg/L.
- Vessels: 250 to 300 mL darkened glass biological oxygen demand bottles with ground glass stoppers
- Test systems: (A) blank control: inoculated culture media, (B) test vessel: 3.0 mg/L sodium benzoate in inoculated culture media, (C) positive control: 1.0 mg/L test item in inoculated culture media, (D) toxicity control: 1.0 mg/L test item and 1.5 mg/L sodium benzoate in inoculated culture media
- Test conditions: Incubated in a water bath at approximately 21°C in the dark
- Observations: Dissolved oxygen concentration were recorded on days 0, 3, 5, 7, 14, 18, 21, 24 and 28 in the test series and days 0, 7 and 14 in the toxicity control

Reference substance:

benzoic acid, sodium salt

Remarks:

Sigma Lot No. MKBC 1469

Preliminary study:

No data reported

Test performance:

- Variation in degradation: Normal biological variation in respiration rates between the control and test vessels were considered to be the cause of variation int degradation rates on different sampling days
- Toxicity control: After 14 days, the toxicity control reached 36 % biodegradation, therefore confirming the test item was not toxic to the micro-organisms

Parameter:

% degradation (O2 consumption)

Value:

17

Sampling time:

28 d

Details on results:

- Conclusion: Propane-1-thiol cannot be considered to be readily biodegradable under the strict conditions of OECD guideline 301D

Results with reference substance:

- Positive control: Sodium benzoate biodegradation reached 65 % after 14 days and 73 % after 28 days therefore the suitability of the test method and culture conditions were confirmed

Validity criteria fulfilled:

yes

Interpretation of results:

other: Cannot be considered as readily biodegradable under strict OECD conditions

Conclusions:

Propane-1-thiol reached 17 % biodegradation in 28 days and therefore cannot be considered readily biodegradable under the strict conditions of OECD guideline 301D.

Executive summary:

Propane-1-thiol reached 17 % biodegradation in 28 days and therefore cannot be considered readily biodegradable under the strict conditions of OECD guideline 301D. The toxicity control showed that propane-1 -thiol is not inhibitory to micro-organisms at a concentration of 1 mg/L. Micro-organisms from a predominantly domestic sewage treatment plant were exposed to 1 mg/L propane-1 -thiol for 28 days in dark glass closed biological oxygen demand bottles. The data are taken from Harlan (2012), an unpublished experimental, ready biodegradability study following OECD 301D, which is GLP-compliant, with the exception of the lack test item analysis, and considered to be reliable without restrictions.

Description of key information

In the key study, propane-1-thiol reached 17 % biodegradation in 28 days and therefore cannot be considered readily biodegradable under the strict conditions of OECD guideline 301D.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

Micro-organisms from a predominantly domestic sewage treatment plant were exposed to 1 mg/L propane-1-thiol for 28 days in dark glass closed biological oxygen demand bottles (Harlan, 2012). Propane-1-thiol reached 17 % biodegradation in 28 days and therefore cannot be considered readily biodegradable under the strict conditions of OECD guideline 301D. The toxicity control showed that propane-1-thiol is not inhibitory to micro-organisms at a concentration of 1 mg/L.

Only the summary of Thiebaud (1997) is available and therefore it cannot be fully evaluated. However, this summary indicated that propane-1-thiol reached 84.7% biodegradation after 28 days, indicating that it is readily biodegradable and that it is not inhibitory to microorganisms. This is a non-GLP study following OECD guideline 301D. There are limitations in reporting, but the study is considered Klimisch 2 (reliable with restrictions) and suitable for use as a supporting study for this endpoint.