4,4'-cyclohexylidenedi-o-cresol

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

A barometric pressure controller which eliminates effects of barometric pressure changes on the respirometer was not functioning. With very low oxygen demand in tests like these, the system will be affected by barometric pressure changes.

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

- modifications to the study guidelines included the use of an industrial sludge in addition to a municipal sludge and the use of a larger sludge inoculum than is specified in the guidelines

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, industrial (adaptation not specified)

Details on inoculum:

This study used activated sludge from the wastewater treatment plant (WWTP) of an industrial facility. In addition, a sample of return sludge from the Schenectady City Water Pollution Control Facility was used in this study.

Biomass (return sludge) was obtained from the Sponsor’s industrial facility in manufacturing site (MF Site) and aerated immediately before packaging on ice with overnight shipment to the testing facility. Samples of influent and effluent (from clarifiers) were also shipped. Upon arrival at the test facility, the sludge was aerated. Return sludge was obtained from the Schenectady municipal plant the morning the MF Site samples arrived. Time elapsed from sampling of the Schenectady sludge until aeration began was approximately 30 minutes. After aeration for an hour, samples of each sludge were taken and prepared for the MLVSS determination (mixed liquor volatile suspended solids, an estimate of the biomass solids).

Duration of test (contact time):

800 h

Initial conc.:

50 mg/L

Based on:

test mat.

Initial conc.:

200 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Details on test conditions: A Challenge environmental Systems, Inc. respirometer with the capability of running 16 vessels simultaneously was used to measure the oxygen uptake rate of the biomass automatically over time. Each vessel held 500 mL and was held in place in a water bath situated over synchronised stirrers. A small trap suspended in the top of each vessel held potassium hydroxide solution to trap the carbon dioxide that was generated during active respiration.

In the Challenge system, oxygen demand was quantified by counting oxygen bubbles that were generated by precisely milled flow measuring cells. As the biomass depleted oxygen and the carbon dioxide was adsorbed by the potassium hydroxide, pure oxygen was pulled into the flow measuring cell through a manifold. Oxygen bubbles of a fixed volume were formed in an inert silicone oil in the lower section of the cell and passed through a detection section which activated a counter in the interface module. Each of the 16 cells was calibrated for the bubble size it produced and the mass of oxygen the bubble contained. The oxygen flowed from the cell into a flexible tube which was attached to a needle inserted into the vessel through a butyl rubber septum. The system was controlled by a computer and the collected data were stored as the accumulated oxygen uptake over time. The test was run at 24 ± 1 °C. A test was performed to qualify the respirometer prior to use which demonstrated that all 16 cells functioned identically.

Reference substance:

benzoic acid, sodium salt

Remarks:

Aldrich Chemical Company, Milwaukee, WI

Parameter:

% degradation (O2 consumption)

Value:

4 - 8.5

Sampling time:

33.3 d

Remarks on result:

other: MF Site sludge, initial DMPBC concentration: 50 mg/L

Parameter:

% degradation (O2 consumption)

Value:

11.5 - 11.7

Sampling time:

33.3 d

Remarks on result:

other: MF Site sludge, initial DMPBC concentration: 200 mg/L

Parameter:

% degradation (O2 consumption)

Value:

35.6 - 38

Sampling time:

33.3 d

Remarks on result:

other: Schenectady sludge, initial DMPBC concentration: 50 mg/L

Details on results:

There is no evidence for DMBPC biodegradation in the tests with MF Site inoculum. All bottles for MF Site sludge showed good recoveries of DMBPC at the end of the experiment. If DMBPC were biodegradable, MF Site sludge would most likely demonstrate it over the Schenectady sludge since MF Site sludge is acclimated to structurally similar chemicals.

DMBPC Recoveries from Bottles:

Bottle No.	Sample ID	% RSD^1	DMBPC recovered (mg)	DMBPC added (mg)	% recovery
1	MF Site + 50 mg/L DMBPC	0.89	24.48	25.5	96.0
2	MF Site + 50 mg/L DMBPC	3.26	23.41	25	92.9
3	MF Site + 200 mg/L DMBPC	0.55	100.13	101.9	98.3
4	MF Site + 200 mg/L DMBPC	1.25	100.32	102	98.5
5	MF Site + 50 mg/L DMBPC	2.37	24.06	26.3	91.5
10	Schen.+ 50 mg/L DMBPC	1.71	16.42	26.5	62.0
11	Schen. + 50 mg/L DMBPC	0.99	16.60	25.8	64.4
12	DMBPC alone	0.77	25.50	26	98.1
14	Schen. + benzoate + 50 mg/L DMBPC	2.82	15.11	26	58.1
15	Schen. + benzoate + 100 mg/L DMBPC	0.55	37.87	50.1	75.6

MF = Manufacturing, Schen. = Schenectady

¹ % relative standard deviation. Three injections were made for each sample.

Validity criteria fulfilled:

not specified

Interpretation of results:

not readily biodegradable

Conclusions:

Under the conditions of this test, DMBPC was not readily biodegradable.

Executive summary:

The potential of the test material to undergo degradation by activated sludge under aerobic conditions was investigated in accordance with the standardised guideline OECD 301 F under GLP conditions.

Modifications to the study guideline included the use of an industrial sludge in addition to a municipal sludge and the use of a larger sludge inoculum than is specified. The activated sludge was exposed to the test material for a contact period of 800 h (approximately 33.3 d) at initial concentrations of 50 and 200 mg/L for the industrial sludge and 50 mg/L only for the municipal sludge. The parameter followed to measure biodegradation was oxygen consumption.

The percentage degradation observed with the industrial sludge was 4 to 8.5 and 11.5 to 11.7 for the 50 ad 200 mg/L initial concentrations, respectively. The percentage degradation observed with the municipal sludge was 35.6 to 38.

Under the conditions of this test, DMBPC was not readily biodegradable.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

abstract

Remarks:

Although it appears to be a guideline study conducted under GLP conditions (which is typically considered K1), only the Abstract was translated from Japanese to English and hence it was not possible to fully evaluate/determine study details.

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

The sludges, collected from 10 different places in Japan, were combined and cultivated for one month.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

The concentration of sludge was 30 mg/L. The test substance was incubated with the cultivated sludge for 4 weeks at 25 °C. During incubation, the oxygen consumption was measured. After 28 days, DMBPC was analysed quantitatively by HPLC and biodegradability determined.

Reference substance:

aniline

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Remarks on result:

other: 3 replicate samples all had 0 % degradation.

Details on results:

The percent biodegradability of the test substance after 28-days incubation based on oxygen consumption was 0, 0 and 0 % in 3 replicate samples.
The percent biodegradability based on HPLC analyses was determined to be: -1, -1 and -1 % in three replicate samples.

Results with reference substance:

Aniline was used as a reference compound and the biodegradability after 7 days incubation was 56 %.

Validity criteria fulfilled:

not specified

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The results of this OECD 301C test indicate that DMBPC is not biodegradable under the test conditions.

Executive summary:

The potential of the test material to undergo degradation by activated sludge under aerobic conditions was investigated in accordance with the standardised guideline OECD 301 C under GLP conditions.

Activated sludge was exposed to the test material at an initial concentration of 100 mg/L under aerobic conditions for 28 days. The sludges, collected from 10 different places in Japan, were combined and cultivated for one month prior to study initiation.

During incubation, the oxygen consumption was measured. After 28 days, DMBPC was analysed quantitatively by HPLC and biodegradability determined.

After the contact period of 28 d, 0 % degradation was observed (measured by O₂ consumption) in all three replicate samples.

The results of this OECD 301 C test indicate that DMBPC is not biodegradable under the test conditions.

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Non-GLP study that does not totally comply with the specific testing guideline, but test methods and parameters are sufficiently documented to enable an evaluation of the data and the study is deemed to be scientifically acceptable. Although a reference substance was not reported in the study report as being concurrently run during the experiment, the laboratory that conducted the study has a proven ability to perform the test method.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

Deviations:

yes

Remarks:

- biochemical oxygen demand (BOD) was not measured. Also, a reference substance was not used in this study. Outside of these limitations, the study is considered appropriate to support the weight of evidence.

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

Details on inoculum: The sludges, collected from 10 different places in Japan, were combined and cultivated for three months. Activated sludge was prepared as follows to maintain its uniformity. The filtrate (5 L) of the supernatant of the combined and cultivated activated sludge was mixed with the mixed filtrate (5 L) of the supernatant of a sludge newly collected at each location. The mixed filtrate (10 L) was aerated with prefiltered open air after the pH value of the mixture was adjusted to 7.0 ± 1.0.

Approximately 30 minutes after ceasing aeration of the sludge mixture, supernatant corresponding to about 1/3 of the whole volume was removed. Dechlorinated water was added to the remaining portion so that the total volume reached 10 L. This mixture was aerated, and then a predetermined amount of synthetic sewage was added to the mixture so that the concentration of the synthetic sewage was 0.1 wt % in the volume of dechlorinated water added. This procedure was repeated once every day. Cultivation was carried out at 25 ± 2 °C.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

TOC removal

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

Conditions of cultivation:
1. Concentration of Test Substance: 100 mg/L
2. Concentration of activated sludge: 30 mg/L (as the concentration of suspended solid)
3. Volume of test solution: 300 mL
4. Cultivation temperature: 25 ± 1 °C
5. Cultivation duration: 28 days

Measurement and analysis:
1. Determination of dissolved organic carbon by means of a total organic carbon analysis (TOC)
2. Determination of test substance by means of high performance liquid chromatography (HPLC)

Parameter:

other: HPLC

Value:

1

Sampling time:

28 d

Remarks on result:

other: average percent degradation

Parameter:

% degradation (TOC removal)

Value:

1

Sampling time:

28 d

Remarks on result:

other: average percent degradation

At the start of the cultivation period the appearance of test media indicated that the test substance was not dissolved in either the water or sludge. At termination, insoluble compound was observed in the test media and growth of the sludge was not observed.

The percent biodegradability of the test substance by HPLC after 28-days incubation were 2% and 1% (average 1%).  The average percent biodegradability of the test substance by TOC was also 1%.

Validity criteria fulfilled:

not specified

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Based on the results of this OECD 301C test, DMBPC was not biodegraded by microorganisms.

Executive summary:

The potential of the test material to undergo degradation by activated sludge under aerobic conditions was investigated broadly in accordance with the standardised guideline OECD 301 C.

The non-GLP study did not totally comply with the specific testing guideline (biochemical oxygen demand (BOD) was not measured and a reference substance was not used), but test methods and parameters were sufficiently documented to enable an evaluation of the data and the study is deemed to be scientifically acceptable.

Activated sludge was exposed to the test material at an initial concentration of 100 mg/L under aerobic conditions for 28 days. The sludges, collected from 10 different places in Japan, were combined and cultivated for three months prior to study initiation.

Two analytical methods were used: determination of dissolved organic carbon by means of a total organic carbon analysis (TOC) and determination of test substance by means of high performance liquid chromatography (HPLC).

At the start of the cultivation period the appearance of test media indicated that the test substance was not dissolved in either the water or sludge. At termination, insoluble compound was observed in the test media and growth of the sludge was not observed.

The average percent biodegradation of the test substance by HPLC after 28-days incubation was 1 %. The average percent biodegradability of the test substance by TOC was also 1 %.

Based on the results of this OECD 301C test, DMBPC was not biodegraded by microorganisms. 

Description of key information

Ready biodegradability

Overall, the test material was determined to be not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

Three studies are available investigating the biodegradability of DMBPC in aquatic environments, all of which demonstrate that DMBPC is not readily biodegradable.

 

In a study performed according to OECD Test Guideline 301 F, the aerobic biodegradability of DMBPC was examined, testing two types of domestic activated sludge for a contact period of 800 h (approximately 33.3 d) (Lockwood SH, 2001b). The study was awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch et al. (1997).

In these tests, a maximum of 38 % degradation (measured by O₂ consumption) was observed after 800 h. 

 

In a study performed according to OECD Test Guideline 301 C, the ready biodegradability of DMBPC was investigated (Institute of Ecotoxicology, Ltd., 2002). After a contact period of 28 d, 0 % degradation was observed (measured by O₂ consumption) in all three replicate samples. However, the study report is in Japanese with only the abstract provided in English; therefore, a thorough assessment of the reliability of the study cannot be completed. The study was therefore awarded a reliability score of 4 in accordance with the criteria set forth by Klimisch et al. (1997).

 

In a third study, the biodegradability of DMBPC was investigated by High Performance Liquid Chromatography (HPLC) and Total Organic Carbon (TOC) analysis; no biodegradation was observed using either analytical method (Kurume Laboratory, 2001). However, a reference substance was not tested to evaluate the efficacy of the inoculum and test system; therefore, the results of this study cannot be validated. The study was awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch et al. (1997).

 

Based on the available data, it is concluded that DMBPC is not readily biodegradable.

 

References:

Institute of Ecotoxicology. 2002. Test on Ready Biodegradability of DMBPC by Microorganisms. Institute of Ecotoxicology, Ltd., Saitama City, Japan. Report No.: E4-02030 - D28. 2002-10-17.

 

Lockwood, S.H. 2001. Biodegradation and Sludge Inhibition of Dimethyl Bisphenolcyclohexane (DMBPC). Corporate Research and Development, Schenectady, NY, USA.

 

Matsunobu, Y. 2001. Biodegradation test of DMBPC by Microorganisms (non-GLP Test). Kurume laboratory, Fukuoka, Japan. Report No.: 13752. 2001-07-31.