Dimethyl cyclohexane-1,4-dicarboxylate

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

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

Adequacy of study:

weight of evidence

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study conducted under GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

1,4-dimethyl cyclohexane-1,4-dicarboxylate (trans)

Cas Number:

3399-22-2

Molecular formula:

C10H16O4

IUPAC Name:

1,4-dimethyl cyclohexane-1,4-dicarboxylate (trans)

Details on test material:

- Name of test material (as cited in study report): trans-Dimethyl 1,4-cyclohexanedicarboxylate
- Physical state: liquid
- Analytical purity: 99.9%
- Lot/batch No.: 910521

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Activated sludge microorganisms were obtained from the Van Lare Treatment Plant, Rochester, New York. On arrival at the laboratory, the activated sludge was aerated for about four hours. A sample (about 500 mL) of the mixed liquid was collected and homogenized for two minutes with a mechanical blender. It was then settled for approximately one hour. The supernatant was decanted to provide sufficient volume for a 1% inoculum for each carboy.

Duration of test (contact time):

35 d

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

10 mg/L

Based on:

test mat.

Initial test substance concentration 2

Initial conc.:

20 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

Four test vesseles were utilized: one for inoculated BSM (Inoculation Blank), one for inoculated Positive Control Solution, and the last two for inoculated Test Solutions at the two test concentrations (10 mg/L and 20 mg/L). The appropriate amounts of BSM stock solutions were added for a final volume of 3000 mL. Then, 30 mL of the prepared inoculum (i.e., supernatant) were added to each carboy. This mixture was aerated with CO2-free air for approximately 24 hours, to purge the system of carbon dioxide. After the aeration period, 100 mL of the 0.0125M Ba(OH)2 was introduced into each of three CO2 absorber bottles and connected in series to the exit airline of each carboy. Test Chemical was added to two of the four carboys to begin the test period. The chemical was tested at two concentrations: 10 and 20 mg/L. As this is a water-insoluble test material, it was added dry to the test carboys together with 500 mL of distilled water (30 mg to one Test carboy and 60 mg to the other). To the third carboy, used as an Inoculum Blank control and containing no test material, 500 mL of distilled water were added. The fourth carboy was for the Positive Control (final concentration, 20 mg/L): 250 mL of the Positive Control Stock Solution (240 mg/L) and 250 mL of distilled water were added to this carboy. The final volume in each carboy was now 3000 mL. Each carboy was agitated with a magnetic stirrer. The test was started by bubbling CO2 -free air through the solutions at a rate of about 50 to 100 mL/minute (one to two bubbles per second) at a temperature of 20 to 25C. The course of degradation was followed by performing titrations over the 35-day test period. The total amount of CO2 produced over the test period is calculated as a percentage of the total theoretical CO2.

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

% Degradation

% Degradation 1

Parameter:

% degradation (CO2 evolution)

Value:

75

Sampling time:

27 d

Remarks on result:

other: 10 mg/L

% Degradation 2

Parameter:

% degradation (CO2 evolution)

Value:

74

Sampling time:

27 d

Remarks on result:

other: 20 mg/L

% Degradation 3

Parameter:

% degradation (CO2 evolution)

Value:

81

Sampling time:

35 d

Remarks on result:

other: 10 mg/L

% Degradation 4

Parameter:

% degradation (CO2 evolution)

Value:

79

Sampling time:

35 d

Remarks on result:

other: 20 mg/L

Details on results:

Biodegradation in Test #1 carboy (10 mg/L) reached negative values ( - 3%) on Days 2 and 4 when less carbon dioxide was evolved from these carboys than from the Blank, resulting in a negative value after subtraction of the Blank (this procedure corrects for background). An approximate 11 day lag period was observed before biodegradation had reached the 10% level. By approximately day 21, 54% biodegradation at 10 mg/L and 48% at 20 mg/L had taken place, as estimated from the graph. This period represents the 10-day time window in which 60% degradation must occur in order for the chemical to be classified as readily biodegradable. The time window for DMCD to reach the 60% level was approximately 12 days for both test concentrations. DMCD finished the test on day 35 with 81% degradation at 10 mg/L and 79% at 20 mg/L. Measurements at day 27 showed 75% and 74% biodegradation for the 10 and 20 mg/L concentrations respectively. The positive control substance yielded >60% biodegradation within 28 days. No significant amount of CO2 (>50 mg/3 L of medium) was evolved from the Inoculum Blank during the test. These conditions fulfill the requirements for a valid test.

BOD5 / COD results

Results with reference substance:

The Positive Control, sodium benzoate, yielded 79% of theoretical over the course of the test.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable, but failing 10-day window

Executive summary:

A 35-day biodegradation test was performed to determine the ready biodegradability of trans-Dimethyl 1,4-cylohexanedicarboxylate using OECD 301b (modified Strum). The substance was tested at concentrations of 10 mg/L and 20 mg/L. An approximate 11-day lag period was observed before 10% biodegradation took place and at the end of the following 10 day window the substance had only reached 51% (10 mg/L) and 48% (20 mg/L) biodegradation. However, >60% biodegradation did occur within slightly less than 12 days after reaching the 10% threshold, and > 74% biodegradation was measured at day 27 of the exposure. The test was continued until day 35 where the cumulative biodegradation reached 81% (10 mg/L) and 79% (20 mg/L). While the substance acheived the degree of degradation necessary to be considered readily biodegradable, it missed the 10 day window criterion by slightly less than 2 days and therefore is considered readily biodegradable, but failing the 10 day window.