Isooctyl mercaptoacetate

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

Study period:

March 05, 2010 to May 10, 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch No. 04.12.09.H
Purity: 99.87%

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): domestic wastewater treatment plant (sewage works, Darmstadt, Germany).
- Preparation of inoculum for exposure: centrifugation, resuspension of solid mterial in tap water (repeat three (3) time).
- Pretreatment: Aliqout of wet sludge material was weighed, dried, and the ratio of wet sludge material to dry weight was determined.
- Concentration of sludge: Aliqouts corresponding to 1.5 g dry sludge material were mixed with one (1) liter of test water (equals 1.5 g/L).

Duration of test (contact time):

28 d

Initial conc.:

102 mg/L

Based on:

ThOD

Remarks:

Oxygen demand of about 249 mg/L

Parameter followed for biodegradation estimation:

O2 consumption

Remarks:

Calculated from the decrease of pressure in the reaction vessel.

Details on study design:

Principle: The test flasks were incubated at 22 ± 2 °C. The pressure decrease in the reaction vessels was measured over complete experimental phase of 28 days using the BSB Sensomat 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.
Identification: Each test unit was uniquely identified with the study number, treatment and replicate number.

Reference substance:

benzoic acid, sodium salt

Test performance:

Inoculum Control: The oxygen demand of the inoculum control (medium and inoculum) was 20 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 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 4 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 and at the end of the 10-day window should be less than 20%. The validity criterion was fulfilled.

Key result

Parameter:

% degradation (O2 consumption)

Remarks:

Flask 1 and 2

Value:

76

Sampling time:

28 d

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

The degradation rate of iOTG reached 76% after 28 days of incubation. According to the test guideline, iOTG is considered to be readily biodegradable.

Executive summary:

The degradation rate of iOTG reached 76% after 28 days of incubation; the 10-day window criterion was curtly not passed. According to the test guideline, iOTG is considered to be readily biodegradable.

Description of key information

The readily biodegradation potential of isooctyl thioglycolate (iOTG) has been investigated through the OECD 301F methodology. The results concluded that iOTG is ready biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater