2,2-dimethylbutane

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:

Jan. 9, 1997-Feb. 6, 1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study.

Justification for type of information:

A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Chester Sewage Works, Welsh Water
- Preparation of inoculum for exposure: Inoculum was collected the day before the test. It was homogenized for two minutes, then allowed to settle. The supernatent was filtered through medical gauze.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: OECD mineral salts medium
- Test temperature: 21.4-21.7 degree C
- Aeration of dilution water: aerated with moist air for 22 h


TEST SYSTEM
- Culturing apparatus: respirometer flask
- Number of culture flasks/concentration: 3 test substance only, 2 test substance and sodium benzoate (inhibition controls)
- Measuring equipment: Co-ordinated Environmental Servies Ltd. Aerobic Respirometer
- Test performed in closed vessels due to significant volatility of test substance: yes, closed with CO2 trap

SAMPLING
- Sampling frequency: hourly
- Sampling method: respirometer


CONTROL AND BLANK SYSTEM
- Inoculum blank: 2
- Other: 2 controls using sodium benzoate


STATISTICAL METHODS: CESAN Data Analysis Program v1.1

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

83

St. dev.:

16

Sampling time:

10 d

Remarks on result:

other: end of 10 day window

Key result

Parameter:

% degradation (O2 consumption)

Value:

98

St. dev.:

12

Sampling time:

28 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

81

Sampling time:

28 d

Remarks on result:

other: inhibition control

Details on results:

% degradation of test samples at end of 10 day window: 87, 96, 65
% degradation of test samples on day 28: 104, 104, 84
% degradation of inhibition controls: 81, 82 - test substance does not inhibit degradation.

Results with reference substance:

The reference substance was 95% degraded by day 14, and degraded 104% by day 28.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The test substance is readily biodegradable, and is not inhibitory.

Executive summary:

This study examined the ready biodegradability of SBP 80-95 LNH. Activated sludge was exposed to a concentration of 100 mg/L of test substance. The O2 consumption was then monitored for the next 28 days. Sodium benzoate was used as the reference substance. The test substance was 98% degraded at the end of 28 days, and 83% degraded at the end of the 10 -day window. The reference substance was 104% degraded, therefore the test is valid. The test substance is readily biodegradable and does not inhibit degradation.

Description of key information

There is no key data available for 2,2 -Dimethylbutane. Key data is available for Hydrocarbons, C6, isoalkanes, <5% n-hexane.

An OECD 301F Manometric Respirometry test was conducted using C6-C7, n-alkanes, isoalkanes, cyclics C6 aliphatics (Shell, 1997a). The test substance was 98% degraded at the end of 28 days, and 83% degraded at the end of the 10 -day window. The reference substance was 104% degraded, therefore the test is valid. The test substance is readily biodegradable and does not inhibit degradation. 2,2 -dimethyl butane is predicted to be readily biodegradable based on this read-across.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable