Commiphora myrrha, ext.

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:

From 2017-08-11 to 2017-11-13

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Study performed according to OECD 301F guideline and under GLP compliance. All validity criteria was successful

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Deviations:

no

Principles of method if other than guideline:

Not applicable.

GLP compliance:

yes (incl. QA statement)

Remarks:

2017-03-13

Specific details on test material used for the study:

None

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Test Species: Aerobic activated sludge (microorganisms from a domestic waste¬water treatment plant) was supplied by the sewage treatment plant of Rossdorf, Germany.
- Conditioning: The aerobic activated sludge used for this study was deposited for 15 minutes, afterwards it was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in test water and centrifuged again. This procedure was done three times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 3.5 g dry material per litre were mixed with test water and aerated overnight. This suspension was used for the experiment.

Duration of test (contact time):

60 d

Initial conc.:

102.3 mg/L

Based on:

other: Test Item Loading Rate (initial concentration in medium C0)

Initial conc.:

301.1 mg/L

Based on:

ThOD

Remarks:

ThOD(NH4)

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Aliquots of washed sludge suspension were mixed with reconstitued test water.
- Reconstitued pure water: Analytical grade salts were added to pure water to prepare the following stock solutions:
a) 8.5 g KH2PO4, 21.75 g K2HPO4, 33.4 g Na2HPO4 x 2 H2O, 0.5 g NH4Cl filled up with pure water to 1000 mL volume; The pH-value was 7.4.
b) 11.25 g MgSO4 x 7 H2O filled up with pure water to 500 mL volume
c) 18.2 g CaCl2 x 2 H2O filled up with pure water to 500 mL volume
d) 0.125 g FeCl3 x 6 H2O filled up with pure water to 500 mL volume
In order to avoid precipitation of iron hydroxide in the stock solution d), one drop of concentrated HCl per litre was added before storage. 50 mL of stock solution a) and 5 mL of the stock solutions b) to d) were combined and filled up to a final volume of 5000 mL with pure water.
- Solubilising agent: Silicone oil AR20 was used. (1%)
- Test temperature: 22°C ± 1°C
- pH: 7.6 (measured at the start of the test); 7.6 to 8.2 (measured at day 61)
- Continuous darkness: yes


TEST SYSTEM
- Culturing apparatus: The closed test flasks were incubated in a climatised chamber under continuous stirring.
- Number of culture flasks/concentration: 2
The test flasks were closed gas-tight by a measuring head. Potassium hydroxide solution (45%) was used for trapping the produced carbon dioxide. The amount of O2 consumed by the activated sludge was calculated from the decrease of pressure in the reaction vessel.
- Measuring equipment: BSB/BOD-Sensor- System, Aqualytic Dortmund, Germany
- Test performed in closed vessels due to significant volatility of test substance:

SAMPLING
O2 consumed daily by the activated sludge was calculated from the decrease of pressure in the reaction vessel.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 (activated sludge + silicone oil + test water)
- Abiotic sterile control: 1
- Toxicity control: 1
- Other: Procedure control : (Ref. Item + activated sludge + silicone oil + test water)

Reference substance:

benzoic acid, sodium salt

Remarks:

Sodium Benzoate

Preliminary study:

No data.

Test performance:

No data.

Parameter:

% degradation (O2 consumption)

Remarks:

ThOD NH4

Value:

24

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Remarks:

ThOD NH4

Value:

32

Sampling time:

60 d

Details on results:

TEST ITEM: At day 28, the mean biodegradation of the test item was 24% (ThODNH4). The study was prolonged until day 60. At the end of the test at day 60, the mean degradation was 32% (ThODNH4).

TOXICITY CONTROL: In the toxicity control containing both, the test item and the reference item sodium benzoate, 35% biodegradation was noted within 14 days and 46% biodegradation after 28 days of incubation. At test end after 60 days incubation, the degradation was 55%. According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was >25% within 14 days.

Results with reference substance:

The reference item sodium benzoate was sufficiently degraded to 89% after 14 days and to 94% after 28 days of incubation. The percentage biodegradation of the reference item confirms the suitability of the used aerobic activated sludge inoculum.

Table 5.2.1/2: Percentage Biodegradation of Test Item, of Sodium Benzoate and of the Toxicity Control based on ThOD_NH4:

Time	Percentage Biodegradation
(Days)	Essential oil of Commiphora myrrha^1		Sodium Benzoate^2	Toxicity control^1, 2
	Flask 1 [%]	Flask 2 [%]	Flask 5 [%]	Flask 7 [%]
1	0	0	26	11
2	0	0	40	16
3	0	0	52	22
4	2	2	69	28
5	2	3	72	29
6	3	5	75	30
7	4	4	76	31
8	5	5	78	31
9	7	7	81	32
10	8	8	84	32
11	10	10	84	33
12	10	12	86	34
13	12	13	86	34
14	12	15	89	35
15	13	16	89	36
16	13	18	92	37
17	13	20	92	37
18	17	21	92	39
19	17	21	89	39
20	18	21	89	41
21	20	23	92	42
22	21	22	91	42
23	21	24	91	43
24	21	24	91	44
25	23	24	91	44
26	23	24	94	44
27	23	24	94	44
28	23	24	94	46
29	23	25	94	47
30	24	25	97	47

31	26	25	97	47
32	26	25	97	48
33	25	25	98	47
34	25	25	98	47
35	25	25	98	48
36	27	26	98	48
37	27	26	98	48
38	25	25	98	48
39	25	25	98	48
40	27	26	98	48
41	27	26	98	49
42	29	26	98	49
43	29	26	98	49
44	29	26	98	50
45	29	28	98	50
46	29	28	98	50
47	29	28	98	50
48	29	28	98	50
49	29	30	98	51
50	30	30	98	51
51	29	29	99	51
52	29	29	99	53
53	29	29	99	53
54	29	29	99	53
55	29	29	99	53
56	29	29	99	54
57	29	29	99	54
58	29	29	99	54
59	34	29	99	55
60	34	29	99	55

Validity Criteria of the Study

- Inoculum Control: The oxygen demand of the inoculum control (medium and inoculum) was 18 mg O₂/L and thus not greater than 60 mg O₂/L within 28 days as required by the test guideline.

- pH-Value: The pH-value of the test item flasks at the end of the test was 7.6 and therefore within the range of pH 6.0 to 8.5 as required by the test guideline

- Reference Item: The percentage degradation of the reference item should reach the level for ready biodegradability (>60%) within 14 days as required by the test guideline. The reference item sodium benzoate was degraded to more than 60% after 4 days of incubation.

- Test Item: The difference of duplicate values for the degradation of the test item at the end of the 10-day window, at day 28 and at the end of the test was less than 20%. The difference of duplicate values at day 28 and day 60 differed by 1% and 5%.The validity criterion was fulfilled.

- Toxicity Control: If in a toxicity test, containing both the test substance and a reference compound less than 25% biodegradation (based on total ThOD) occurred within 14 days, the test substance can be assumed to be inhibitory. The biodegradation was 35% at day 14; the test item was not inhibitory.

All validity criteria are fulfilled.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Essential oil of Commiphora myrrha is considered to be not readily biodegradable based on ThODNH4 after 28 days. Moreover, 60% degradation was not reached after 60 days of incubation.

Executive summary:

The test item Essential oil of Commiphora myrrha was investigated for its ready biodegradability in a manometric respirometry test over a period of 28 days, according to the OECD 301F guideline, and further prolongated to 60 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.

At day 28, the mean biodegradation of the test item was 24% (ThOD_NH4). In agreement with the study monitor, the study was prolonged until day 60. At the end of the test at day 60, the mean degradation was 32% (ThOD_NH4).

 

Therefore, Essential oil of Commiphora myrrha is considered to be not readily biodegradable based on ThODNH4 after 28 days. Moreover, 60% degradation was not reached after 60 days of incubation.

The reference item sodium benzoate was sufficiently degraded, thus confirming the suitability of the aerobic activated sludge inoculum used.

According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was >25% within 14 days in the toxicity control.

The oxygen demand of the inoculum control (medium and inoculum) was not greater than 60 mg O₂/L within 28 days as required by the test guideline.

pH values were in the range required in the guideline. Therefore, all validity criteria of the study were fulfilled.

Description of key information

Under the test conditions, Essential oil of Commiphora myrrha is considered to be not readily biodegradable based on ThODNH4 after 28 days. Moreover, 60% degradation was not reached after 60 days of incubation.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

A reliable experimental study performed on the registered substance was available for that endpoint.

The test item was investigated for its ready biodegradability in a manometric respirometry test over a period of 28 days, according to the OECD 301F guideline, Based on results at day 28, the study has been extended up to 60 days.

The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.

At day 28, the mean biodegradation of the test item was 24% (ThOD_NH4). At the end of the test at day 60, the mean degradation was 32% (ThOD_NH4).

Based on the test guideline, Essential oil of Commiphora myrrha is considered to be not readily biodegradable based on ThODNH4 after 28 days, under test conditions. Moreover, 60% degradation was not reached after 60 days of incubation.

All validity criteria were fulfilled. The percentage biodegradation of the reference item confirmed the suitability of the used aerobic activated sludge inoculum, and the test item was assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was >25% within 14 days in the toxicity control.

Therefore, this study complied with the requirements of the guideline and was considered acceptable for that endpoint.