Triisobutyl phosphate

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:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

Activated sludge from laboratory wastewater plant treating municipal sewage.
Concentration of activated sludge in the test assay: 30 mg/L dry substance

Duration of test (contact time):

28 d

Initial conc.:

37 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Reference substance:

aniline

Key result

Parameter:

% degradation (CO2 evolution)

Value:

70 - 80

Sampling time:

28 d

Details on results:

- Duration of adaptation phase: 8 days
- Duration of degradation phase: 20 days
- Degradation degree of DOC at the end of the test, mean value: 90-100 %

Results with reference substance:

- Degradation degree of the reference substance after 14 days: 80-90 %
- Degradation degree in the inhibition control after 14 days: 70-80 %

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable, but failing 10-day window

Description of key information

Readily biodegradable: 79-82% in 28 days (OECD 301B)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

Two studies investigating the ready biodegradability of Triisobutyl phosphate (TiBP) are available. The key study was conducted according to GLP and OECD guideline 301B using non-adapted activated sludge from a domestic STP as inoculum (BASF 2019). After 28 days 79-82% degradation of TiBP was observed and the 10d-window was passed. Thus, the substance was classified as readily biodegradable. This was confirmed by a second study also conducted to GLP and OECD guideline 301B, which just missed to fulfill the 10d-window criterion.