2,6-bis(1,1-dimethylethyl)-4-(phenylenemethylene)cyclohexa-2,5-dien-1-one

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1998-02-03 to 1998-05-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study according to OECD 301B

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

adopted on 17th July 1992

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

429-460-4

EC Name:

-

Cas Number:

7078-98-0

Molecular formula:

C21 H26 O

IUPAC Name:

2,6-bis(1,1-dimethylethyl)-4-(phenylenemethylene)cyclohexa-2,5-dien-1-one

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Loxahatchee Environmental Control District sewage treatment plant (Jupiter, FL)

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

20 mg/L

Based on:

other: carbon

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: in accordance to the guideline
- Test temperature: 22 ± 2°C
- pH: between 7.3 and 7.4
- pH adjusted: yes/no
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 4-liter test bottles
- Number of culture flasks: 7
- Method used to create aerobic conditions: The content of each bottle was purged with CO2-free air for 24 hours.
- Details of trap for CO2 and volatile organics if used: two gas-washing bottles containing 100 mL of 0.0125 M Ba(OH)2

CONTROL AND BLANK SYSTEM
- Inoculum blank: two bottles
- Sterile control: one bottle
- Reference control: one bottle
- Toxicity control: one bottle

Reference substance

Reference substance:

aniline

Results and discussion

Test performance:

During the first week of the study, CO2 analysis was conducted at two-day intervals after the first day. At each interval, aeration was stopped, the firstgas washing bottle in each series was removed from the system, and the content transferred into a 250-mL Erienmeyer flask. The amount of unreacted Ba (OH)2 in this gas washing bottle was quantified by titrating a hydrochloric acid solution to the phenolphthalein endpoint. The second gas washing bottle in each series was then moved forward to replace the first gas washing bottle. Another gas washing bottle containing 100 mL of fresh Ba(OH)2 solution was inserted as the second gas washing bottle. In this way, the cumulative CO2 production from each test bottle was quantified and the biodegradation of the test substance monitored. After the first week, the sampling schedule was changed to once every three to five days as appropriate to the degradation rate of the test substance. After the biodegradation curve showed the plateau, the test was terminated. At termination, the pH of the solution in each test bottle, except for the sterile control, was measured again. Final titrations were made at test termination (day 28).

% Degradation

Parameter:

% degradation (CO2 evolution)

Value:

7.27

Sampling time:

28 d

Details on results:

At a test substance concentration of 20.0 mg carbon/L, cumulative biodegradation only reached 7.27% by day 28. There was no significant increase in the cumulative CO2 production and percent biodegradation rates from day 1 to day 28. No acceleration period was observed during the whole test period. Therefore, biodegradability of test item was calculated based on the mean of the percentage cumulative biodegradation rates calculated at day 28 at both containers. Based upon these data, the percent biodegradability of test item was determined to be 7.27%. The half-life of test item was calculated to be 267 days. The test substance was not toxic to the inoculum since biodegradation occurred in a mixed solution of test and reference substances. The test substance was also found to be stable to abiotic processes because no biodegradability of test item was found under sterile conditions (70% of isopropanol in water).

BOD5 / COD results

Results with reference substance:

Cumulative biodegradation of the reference substance reached 62.8% on day 13 which met the test criterion of >60% degradation of the reference substance by day 14. The total CO2 evolution in the inoculum blank at the end of the test was 41.4 mg/L. Both the amount of inorganic carbon and the CO2 evolution concentration values were within the acceptable ranges for a valid test.

Applicant's summary and conclusion

Interpretation of results:

other: Not readily biodegradable (according to OECD criteria)