Cyclopentene

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:

May to Spetember 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Identification: Cyclopentene
Appearance: Clear colourless liquid
Batch: 0000015386
Stable under storage conditions until: 19 March 2021 (expiry date)
CAS number: 142-29-0

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

Source: The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.
Treatment: The freshly obtained sludge was kept under continuous aeration until further treatment. The concentration of suspended solids was determined to be 3.5 g/L in the concentrated sludge. Before use, the sludge was allowed to settle (31 minutes) and the liquid was decanted for use as inoculum at the amount of 10 mL/L of mineral medium.
Reason for selection: The test has been accepted internationally (EC, OECD) for determining the 'ready' biodegradability of test items under aerobic conditions.

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

inorg. C analysis

Details on study design:

Test Procedure and Conditions
Test duration: 28 days
Test vessels: Well-sealed glass serum vessels (TFE/silicone septa and Teflon seals). Vessels were filled to give a headspace to liquid ratio of 1:2 (107 mL test medium in 160 mL-capacity vessel).
Milli-RO / Milli-Q water: Tap-water purified by reverse osmosis (Milli-RO) and subsequently passed over activated carbon and ion-exchange cartridges (Milli-Q) (Millipore Corp., Bedford, Mass., USA).
Milli-RO water: carbon levels < 500 ppb.

Stock solutions of mineral components
A) 8.50 g KH2PO4
21.75 g K2HPO4
67.20 g Na2HPO4.12H2O
0.50 g NH4Cl
dissolved in Milli-Q water and made up to 1 litre,
pH 7.4 ± 0.2
B) 22.50 g MgSO4.7H2O dissolved in Milli-Q water and made up to 1 litre.
C) 36.40 g CaCl2.2H2O dissolved in Milli-Q water and made up to 1 litre.
D) 0.25 g FeCl3.6H2O dissolved in Milli-Q water and made up to 1 litre.

Mineral medium: 1 litre mineral medium contains: 10 mL of solution (A), 1 mL of solutions (B) to (D) and Milli-RO water.

Test set-up:
- Inoculum blank = Inoculated medium
- Procedure control = Inoculated medium + Reference item at 20 mg C/l
- Test item = Inoculated medium + Test item at 20 mg C/l
- Toxicity control = Inoculated medium + Reference item at 20 mg C/l + Test item at 20 mg C/l
- Abiotic control: = Untreated medium + sterilising agent (1 mL of a solution containing 10 g/L of HgCl2 (Thermo Fisher GmbH, Kandel, Germany, 99.999%) + Test item at 20 mg C/l






Sampling points and the Inoculum blank: day 1(3), 7 (3), 14 (5), 21 (3) and 28 (5)
number of vessels Procedure control: day 1 (3), 7 (3) and 14 (5).
(between brackets) Test item: day 1(3), 7 (3), 14 (3), 21 (3) and 28 (5).
Toxicity control: day 1 (3), 7 (3) and 14 (5).
Abiotic control: day 1 (3) and 28 (5).
Three parallel reserve vessels for each test series were prepared. These vessels were not used and were removed at the end of the test.
Furthermore, an additional vessel of each test series was prepared for pH measurement. The vessel was prepared identically to the test vessels.
Incubation In the dark on an orbital shaker, with a shaking rate sufficient to keep the vessel well mixed and in suspension.
7 M NaOH 7M NaOH (Merck KGaA, Darmstadt, Germany) was prepared freshly at the start of the test.
Sample pre-treatment 1 mL 7 M NaOH was injected through the septum of each vessel and the vessels were returned to the orbital shaker for 1 h.
Thereafter, the vessels were removed from the shaker and allowed to settle. The supernatant was used for IC analysis.

Reference substance:

other: 1-Octanol

Test performance:

The temperature, recorded in a vessel with Milli-RO water in the same room, varied between 19 and 22 °C, and we slightly outside the range stated in the Study Plan for a short period of time. For a period of <60 minutes, the temperature was outside of the range in the Study Plan. Evaluation: Highest temperature recorded was 21.8 °C. Since the temperature was outside the range for such a short period (<60 minutes for a 28 day study), there was no influence on the outcome or validity of the study.

In the toxicity control, more than 25% biodegradation occurred within 14 days (34%, based on ThIC). Therefore, the test item was assumed not to inhibit microbial activity.

Key result

Parameter:

% degradation (inorg. C analysis)

Value:

1

Sampling time:

28 d

Details on results:

Assuming 100% mineralization of the test item to CO2, the Theoretical maximum IC production (ThIC) in excess of that produced in the inoculum blanks equals the Total Organic Carbon (TOC) added to each test vessel at the start of the test. The TOC content of Cyclopentene was determined to be 88.2%. Thus, the ThIC of Cyclopentene was calculated to be 0.88 mg/mg.

The ThIC of the reference item (1-octanol) was calculated to be 0.74 mg/mg.

The relative biodegradation values calculated from the measurements performed during the test period revealed no biologically relevant biodegradation of Cyclopentene.

However, the test item is extrememly volatile and there is potential for minimal exposure of the test item to the inoculum as the test item may have been mostly present in the headspace of the vessels.

Results with reference substance:

The reference substance, 1-octanol had a mean biodegradation of 73% in 14 days.

Table1          
Mean Biodegradation in Percentage of theTheoretical maximum IC Production (ThIC)

Nominal day	Microbial degradation in percentage of the ThIC			Degradation
	Reference Item	Test Item	Toxicity Control	Abiotic Control
1	1	1	0	0
7	52	0	23	-
14	73	2	34	-
21	-	0	-	-
28	-	1	-	0

- = Not measured

Table2          
pH Values of Different Test Media

Test medium:	pH at the start of the test:
Inoculum blank	7.7
Procedure control	7.7
Test item	7.7
Toxicity control	7.7
Abiotic control	7.4

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Cyclopentene is not readily biodegradable.

Executive summary:

The ready biodegradation potential of cyclopentene was tested in a study according to OECD 310, headspace test. It was reported that there was no biological degradation of the test item during the test. Therefore, cyclopentene is not readily biodegradable.

However, the test item is extrememly volatile and there is potential for minimal exposure of the test item to the inoculum as the test item may have been mostly present in the headspace of the vessels.

Description of key information

 The ready biodegradation potential of cyclopentene was determined in a study according to OECD TG 310. It was reported that there was no biological degradation of the test item during the test. Therefore, cyclopentene is not readily biodegradable.
    
    
    
    

However, the test item is extrememly volatile and there is potential for minimal exposure of the test item to the inoculum as the test item may have been mostly present in the headspace of the vessels.








 

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater