Isopropyl 2-methylbutyrate

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:

27 January to 25 February 1998

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)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva: Alre). The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 10009 for 10 minutes, discarding the supernatant and re-suspending in mineral medium) and kept aerobic until being used on the same day.

Duration of test (contact time):

28 d

Initial conc.:

2.865 g/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral medium was prepared by mixing 50 ml of solution A and 2000 ml deionised water, adding 5 ml of each of the solutions B: C and D and making up to 5 litres with deionised water The pH is measured and if necessary adjusted to 7.4 ± 0.2 with phosphoric acid or potassium hydroxide.
- Test temperature: 22°C
- pH: initial = 7.45; final = 7.35 - 8.30
- pH adjusted: no data

SAMPLING
- Sampling frequency: Everyday the oxygen consumption of each flask is recorded and correct temperature and stirring are checked. At the end of the test period (normally 28 days), the pH of each flask is measured again.
- Sampling method: A measured volume of inoculated mineral medium, containing a known concentration of test substance (100 mg/I) as the nominal sole source of organic carbon, is stirred in a closed flask at a constant temperature (± 1°C) for up to 28 days. The consumption of oxygen is determined by measuring the quantity of oxygen (produced electrolytically) required to maintain constant the gas volume in the respirometer flask. Evolved carbon dioxide is absorbed in soda lime pellets. The amount of oxygen taken up by the microbial population during biodegradation of the test chemical (corrected for uptake by blank inoculum. run in parallel) is expressed as a percentage of ThOD (Theoretical Oxygen Demand, calculated from the elemental composition, assuming that carbon is oxidized to carbon dioxide and hydrogen to water).

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

63

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

58

Sampling time:

10 d

Remarks on result:

other: Fails 10 day window.

Oxygen uptakes, as read on the SAPROMAT meters, are corrected:

- by deducting the basic oxygen uptake of sludge (flasks 2/3 and 2/4)

- proportionally to account for the small differences between actual and nominal concentrations of test and reference substances.

 

Means of identical flasks were used to obtain the different results and curves that can be found in Appendices 1 to 4.

 

Degradation of sodium benzoate exceeds 40% after 7 days and 65% after 14 days: the activity of the inoculum is thus verified and the test is considered as valid.

Interpretation of results:

inherently biodegradable

Conclusions:

Isopropyl Methyl-2-Butyrate undergoes 63% biodegradation after 28 days in the test conditions. Biodegradation starts on day 3 and reaches 58 % at the end of the 10-day window (days 3 to 13).
Though these results are close to the pass level (60% at the end of the 10-day window), Isopropyl Methyl-2-Butyrate should be regarded as not readily biodegradable according to this test. However it may be regarded as inherently biodegradable but as the substance showed 63% biodegradability and was within 2% of the pass level at the end of the 10-day window, under REACH it may be considered to be readily biodegradable but failing the 10 day window.
The curves obtained with the reference substance alone and with Isopropyl Methyl-2-Butyrate + reference substance show no toxic effect of Isopropyl Methyl-2-Butyrate on the micro-organisms at the test concentration.

Description of key information

Isopropyl Methyl-2-Butyrate undergoes 63% biodegradation after 28 days in the test conditions. Biodegradation starts on day 3 and reaches 58 % at the end of the 10-day window (days 3 to 13).

Though these results are close to the pass level (60% at the end of the 10-day window), Isopropyl Methyl-2-Butyrate should be regarded as not readily biodegradable according to this test. However it may be regarded as inherently biodegradable but as the substance showed 63% biodegradability and was within 2% of the pass level at the end of the 10-day window, under REACH it may be considered to be readily biodegradable but failing the 10 day window.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable but failing 10-day window

Type of water:

freshwater