N-hexane

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

9th January to 6th February 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

Principles of method if other than guideline:

SBP 80/95 LNH is a C6-C7 hydrocarbon solvent with a n-hexane content of less than 3%. Being made from hydrogenated feedstock, its aromatics and olefins content is very low.

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 ºC
- 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-d 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 data available for this substance. However, key data is available for the structural analogue Hydrocarbons, C6-C7, n-alkanes, isoalkanes, cyclics, < 5% n-hexane and is presented in the dossier. The data is read across to this substance based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13.

Hydrocarbons, C6-C7, n-alkanes, isoalkanes, cyclics, <5% n-hexane biodegraded to 98% at the end of 28 days and to 83% at the end of the 10-d window, following an OECD 301F Manometric Respirometry test. The substance is therefore considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

An OECD 301F Manometric Respirometry test was conducted using Hydrocarbons, C6-C7, n-alkanes, isoalkanes, cyclics, < 5% n-hexane. 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.