1,2,3,4,4a,7,8,8a-octahydro-2,4a,5,8a-tetramethyl-1-naphthyl formate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Study period:

The study was conducted between 25 October 2002 and 02 December 2002.

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 301F, Ready Biodegradability by the Manometric Respirometry Test

Deviations:

no

Principles of method if other than guideline:

Inhibition Control in Ready Biodegradablity Test.

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Lot No.: 9000477976
Purity (GC): 97.4% (sum of the four isomers)
Aspect: colourless to pale yellow liquid

Analytical monitoring:

not required

Vehicle:

no

Details on test solutions:

A measured volume of inoculated mineral medium containing 100 mg/L of test substance was used.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Peney-Dessous) was used. The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.
Dry weight of suspended solids: 3.970 g/l.
To obtain a concentration of 30 mg/I (dry weight) in a 250 ml flask, 1.89 ml of sludge is needed (inoculum).

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

35 d

Test temperature:

22 C

pH:

Initial pH was 7.44 in all flasks; final pH ranged from 7.39 to 7.92.

Nominal and measured concentrations:

Nominal concentration of test and reference substances is 100 mg/L.

Details on test conditions:

Water
The water used during this study is deionised water containing less than 10 mg/L dissolved organic carbon.

Stock solutions of mineral components
The following stock solutions were prepared:

Solution A:
KH2PO4: 8.5 g
K2HPO4: 21.75 g
Na2H PO4.2H2O: 33.4 g
NH4CI: 0.5 g
dissolved in water and made up to 1 litre.

Solution B:
CaCl2: 27.5g
dissolved in water and made up to 1 litre.

Solution C:
MgSO4•7H2O: 22.5g
dissolved in water and made up to 1 litre.

Solution D:
FeCI3.6H2O: 0.25g
HCI Conc.: one drop
dissolved in water and made up to 1 litre .

Mineral medium
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.

Toxicity of the test substance
As suggested in the OECD 301F method, the toxicity of the test substance for the inoculums is checked. Therefore a pair of flasks of the volumetric respirometer are filled with mineral medium + test substance (100 mg/L) + reference substance (100 mg/L) + inoculums and their respirations are recorded as for the other flasks. If they are lower than those of the flasks containing mineral medium + reference substance (100 mg/L) + inoculums, the test substance can be assumed to be inhibitory to the inoculums used.

Preparation of the flasks
Test substance samples (25 mg, corresponding to 100 mg/l in a 250 ml flask) are weighed in small aluminium boats and added directly to the test flasks of the SAPROMAT, whereas reference substance samples (sodium benzoate) are added as 1.0 ml of a 25 mg/ml solution in mineral medium.
All flasks are filled with 250 ml of mineral medium. Samples of test or reference substance, or both, are added. Then, a volume of suspended sludge corresponding to 7.5 mg dry weight (as determined, generally 1 to 3 ml) is added. Except when the test substance has an acid or alkaline character, the pH of each flask is not measured but assumed to be the same as the mineral medium, in order not to remove any floating undissolved test substance from the test medium by dipping a glass electrode in it. Neutral test substances, even sodium benzoate, were shown not to affect the pH of the medium by more than 0.1 pH unit. About 2 g of soda lime is placed in an attachment of the stopper, the flasks are closed and placed in the water bath of the SAPROMAT. After temperature and pressure equilibration, the oxygen-meters of the instrument are set to zero (time zero of the experiment).

Performance of the test
Every day 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.

Test temperature: 22°C
Test duration: 35 days

Dry weight of suspended solids: 3.97 g/L.
To obtain a concentration of 30 mg/L (dry weight) in a 250 mL flask 1.89 mL of sludge is needed (inoculum).

Reference substance (positive control):

yes

Remarks:

Sodium benzoate

Key result

Duration:

35 d

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Comparison of respiration of flasks containing test chemical + positive control and flasks containing positive control only

Details on results:

The curves obtained with the reference substance alone and with the test substance + reference substance show no toxic effect of the test substance to the microorganisms at the test concentration of 100mg/L - see illustration section.

Results with reference substance (positive control):

Degradation of sodium benzoate exceeded 40 % after 7 days and 65 % after 14 days. The activity of the inoculum was verified.

Validity criteria fulfilled:

yes

Conclusions:

The toxicity of OXYOCTALINE FORMATE to microorganisms was assessed in an inhibition control of a standardised ready test performed according to OECD 301F. The curves obtained with the reference substance alone and with the test substance + reference substance show no toxic effect of the test substance to the microorganisms at the test concentration of 100mg/L. This concentration can be considered the NOEC for the toxicity to STP microorganisms.

Executive summary:

A ready biodegradation test was performed on the test substance according to OECD Test method 301 F. The toxic effect of the test substance on the inoculum was assessed during this test and it was demonstrated that there was no toxic effect to microorganisms at the test concentration (100 mg/L).

Description of key information

In a standardised ready biodegradability screening study (Rudio 2003), no toxicity was observed in an inhibition control at a test concentration of 100 mg/L. This concentration can be considered as a NOEC for the toxicity to STP microorganisms.

Key value for chemical safety assessment

EC50 for microorganisms:

100 mg/L

Additional information

Activated sludge respiration inhibition was assessed during a ready biodegradation test. The curves obtained with the reference substance alone and with the test substance + reference substance showed no toxic effect of the test substance to the microorganisms at the test concentration of 100mg/L. Degradation of the reference substance, sodium benzoate, exceeded 40 % after 7 days and 65 % after 14 days. The activity of the inoculum was verified.