Sodium mentholate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1975

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)

Deviations:

not specified

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, adapted

Details on inoculum:

The adaptation of the activated sludge is made in the following way. Activated sludge taken from a sewage plant is cultivated in a 1000 mL volumetric cylinder. The mixture is aerated with pressure air. Every day 200 mL of the mixture is driven off so that the sludge age is 5 days. After driving off the 200 mL of the mixture aeration is interrupted, and after sedimentation ca. 600 mL of the liquid phase is driven off. The residue (200 mL of the thickened activated sludge) is diluted with tap water to the volume of ca. 800 mL and 600 mg/L of starch or glucose, 600 mg/L of peptone, 25 mL of a phosphate buffer pH 7.2, and the solution of the tested compound are added. Then the mixture in the cylinder is made up to 1000 mL with tap water and aerated for 23 h (the recirculation ratio is 0-25). After this period the procedure is repeated.
The concentration of the tested substance is gradually increased so that after 20 days of adaptation it reaches the equivalent value of 200 mg/L COD. During this period an occasional biological analysis is made and the change of biocenosis is evaluated. In case the substance is a toxic one, the sludge must be adapted at lower initial concentrations, and the concentration of the compound in the actual experiment on degradability is to be decreased equally.

Duration of test (contact time):

>= 0 - <= 20 d

Initial conc.:

200 mg/L

Based on:

COD

Parameter followed for biodegradation estimation:

other: decrease of COD

Details on study design:

To 1000-1500 mL of the biological medium such amount of the solution of the substance tested is added that the initial COD is 200 mg/L. Then such an amount of the adapted activated sludge, washed and thickened by sedimentation, is dosed to the medium that the concentration of the dry matter is 100 mg/L. Simultaneously, a blank test is prepared, or possiby also a test with a standard compound, to verify the activity of the inoculum (glucose, phenol etc.). With volatile substances a test without the inoculum is to be carried out as well in order to differentiate the actual biological degradation and the losses due to mere volatalization.
From the beakers 50-80 mL of the mixture are taken, and after filtration through a filter paper of medium porosity the initial values of COD or organic carbon of the liquid phase are determined. If the filtrates are turbid the liquid phase must be separated by centrifuging or with membrane ultrafilters with average pore size 0.6-1.0 µm. The initial levels of the mixture in the beaker is marked either with pencil on the glass or by means of a strip of mm paper stuck to the outer wall of the beaker. Afterwards the beakers are placed in a dark room with a temperature 20 +/- 3 °C on magnetic stirrers. The oxygenation capacity of this device was ca. 11 mg of oxygen /hxl at 800 rev/min.
At conveniently chosen time intervals always ca. 50-80 ml of the sample are taken for analysis, When the time intervals are longer the potential losses due to evaporation should be made up with distilled water prior to each sampling. The time intervals between the individual samplings depend on the rate of degradation. With very readily degradable substances the process is completed as early as in 24 h. Generally it is sufficient to take samples once or twice a day. The values of the blank test are subtracted.
The experiment is carried out till there is no decrease of COD. After that time the total percentage of COD removed and the rate of degradation are evaluated.
If under the given experimental conditions already in 120 h of incubation over 90 m% of the initial COD is removed (the degradation rate being over 15 mg of COD /gxh), the substance tested can be considered to be biologically readily decomposable.
When even after 20 days of incubation there is no complete biological degradation, the experiments are repeated at lower initial concentration of the substance tested. With very low initial values of COD or organic carbon the degradation is to be studied
using a suitable structural-analytical methods.

Parameter:

other: COD

Value:

95.1

Sampling time:

5 d

Parameter:

COD

Value:

17.7 other: mg COD per gramm and hour

Menthol: 95.1 % removed based upon COD with a rate of biodegradation of 17.7 mg COD g^-1 h^-1.

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

Within 5 days a degradation of 95.1 % was determined.

Executive summary:

Inherent biodegradability of the test item was assessed by Pitter puplished in 1976. The test was conducted in a way similar to Zahn-Wellens-test described in OECD TG 302 B. The test substance as sole source of carbon was tested with an initial concentration of 200 mg/L COD (chemical oxygen demand). Activated sludge from a sewage treatment plant adapted for 20 days was used as inoculum (100 mg/L dry matter). 95.1 % of the test item was degraded within 5 days with a rate of 17.7 mg COD g^-1h^-1. Therefore it is concluded, that the test substance is inherently biodegradable.

Reference 2

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The registered substance rapidly degrades to sodium hydroxide and menthol via hydrolysis. It hydrolyses within minutes (2 min 24 s) (please refer to RSS of hydrolysis study linked under 'Cross-reference). Therefore, the properties of the registered substance in aqueous media are determined by its hydrolysis products. This approach is in accordance with Scenario 1 of the RAAF (ECHA 2017).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Please refer to test material.

3. ANALOGUE APPROACH JUSTIFICATION
As the test substance rapidly degrades to sodium hydroxide and menthol via hydrolysis, biodegradation is only relevant for the organic hydrolysis product menthol. Thus, to fulfil the data requirements of Regulation EC No 1907/2006 Annex VII, it is fully justified to adress this endpoint with data on the degradation product menthol.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

reference to other study

Parameter:

other: COD

Value:

95.1

Sampling time:

5 d

Parameter:

COD

Value:

17.7 other: mg COD per gramm and hour

Menthol: 95.1 % removed based upon COD with an rate of biodegradation of 17.7 mg COD g^-1 h^-1.

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

Within 5 days a degradation of 95.1 % was determined.

Executive summary:

Inherent biodegradability of the test item was assessed by Pitter puplished in 1976. The test was conducted in a way similar to Zahn-Wellens-test described in OECD TG 302 B. The test substance as sole sourceof carbon was tested with an initial concentration of 200 mg/L COD (chemical oxygen demand). Activated sludge from a sewage treatment plant adapted for 20 days was used as inoculum (100 mg/L dry matter). 95.1 % of the test item was degraded within 5 days with a rate of 17.7 mg COD g^-1h^-1. Therefore it is concluded, that the test substance is inherently biodegradable.

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Data waiving:

study technically not feasible

Justification for data waiving:

the study does not need to be conducted because the substance is inorganic

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The registered substance rapidly degrades to sodium hydroxide and menthol via hydrolysis. It hydrolyses within minutes (2 min 24 s) (please refer to RSS of hydrolysis study linked under 'Cross-reference). Therefore, the properties of the registered substance in aqueous media are determined by its hydrolysis products. This approach is in accordance with Scenario 1 of the RAAF (ECHA 2017).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Please refer to test material.

3. ANALOGUE APPROACH JUSTIFICATION
As the test substance rapidly degrades to sodium hydroxide and menthol via hydrolysis, biodegradation is only relevant for the organic hydrolysis product menthol. Thus, to fulfil the data requirements of Regulation EC No 1907/2006 Annex VII, it is fully justified to adress this endpoint with data on the hydrolysis product menthol. The endpoint is waived for the inorganic hydrolysis product sodium hydroxide.

Description of key information

As the test substance rapidly degrades to sodium hydroxide and menthol via hydrolysis, biodegradation is only relevant for the organic hydrolysis product menthol. Thus, to fulfil the data requirements of Regulation EC No 1907/2006 Annex VII, it is fully justified to adress this endpoint with data on the hydrolysis product menthol. The endpoint is waived for the inorganic hydrolysis product sodium hydroxide.

Inherent biodegradability of the test item was assessed by Pitter puplished in 1976. The test was conducted in a way similar to Zahn-Wellens-test described in OECD TG 302 B. The test substance as sole source of carbon was tested with an initial concentration of 200 mg/L COD (chemical oxygen demand). Activated sludge from a sewage treatment plant adapted for 20 days was used as inoculum (100 mg/L dry matter). 95.1 % of the test item was degraded within 5 days with an rate of 17.7 mg COD g^-1h^-1. Therefore it is concluded, that the test substance is inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Type of water:

freshwater