m-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:

other: Study comparable to OECD Guideline 301C

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

yes

Remarks:

Voith sapromat B12

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Minicipal sewage sludge with initial cell concentration: 30 mg/l

Duration of test (contact time):

20 - 40 d

Initial conc.:

100 mg/L

Based on:

test mat.

Reference substance:

aniline

Remarks:

100 mg/L

Parameter:

% degradation (O2 consumption)

Value:

80 - 95

Sampling time:

40 d

Remarks on result:

other: readily biodegradable

Details on results:

The oxygen uptake curves are not reported. However, the authors state that all test compounds revealed the lag phase, biodegradation phase and the plateau region within a period of 10 days, indicating that the 10-day window criteria is met.
First order biodegradation constant (hr-1): ln k = -5.77
maximum specific substrate uptake rate per unit biomass km = 17.3 / day (Aniline 16.1, Phenol 16.9).
m-Cresol is slightly better biodegradable than phenol and aniline.

Results with reference substance:

degradation of reference substance aniline >=60 % within 28 days

The OECD (2003) discussed the study during the OECD/ICCA HPVC program as follows:

Desai et al. (1990) determined the Monod kinetics of m- and p-cresol using an electrolytic

respirometry test comparable to OECD guideline 301 C. Activated sludge from a wastewater

treatment plant receiving predominantly domestic sewage was used as inoculum in a concentration

of 30 mg/l. Within an incubation period of 40 days degradation of both cresol isomers (initial

concentration 100 mg/l) was in the range of 80 % to 95 %. The specific oxygen uptake curves of the

cresols are not reported. However, the authors state that all test compounds revealed the same

pattern: the lag phase, biodegradation phase and the plateau region within a period of 10 days.

Therefore, it can be concluded from this test that m- and p-cresol are readily biodegradable. The

first order degradation constants ln(k) [h-1] were determined to be -5.77 (m-cresol) and -5.87 (pcresol).

From these values half-lives of 9.3 d resp. 10.3 d can be calculated.

Validity criteria fulfilled:

not specified

Interpretation of results:

readily biodegradable

Conclusions:

In a test according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)), 80 to 95 % of m-cresol were degraded within 40 d.

Executive summary:

In a test according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)), 80 to 95 % of m-cresol were degraded within 40 d. m-Cresol was slightly better biodegradable than phenol and aniline supporting the conclusion that it is readily biodegradable.

Reference 2

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Test procedure comparable to standard method and in accordance with generally accepted scientific standards; basic data given

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)

Deviations:

yes

Remarks:

minor deviations

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, adapted

Details on inoculum:

100 mg/L dry weight

Initial conc.:

200 mg/L

Based on:

COD

Details on study design:

Test compound was sole source of carbon

Parameter:

other: COD removal

Value:

95.5

Sampling time:

5 d

Details on results:

Initial degradation rate: 55.0 mg COD/g/h

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Executive summary:

m-Cresol is inherently degradable as shown by a test similar to OECD guideline 302 B with a removal of 96 % of m-cresol after 5 days of incubation.

Reference 3

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study, basic data given

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)

Deviations:

no

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, industrial, adapted

Details on inoculum:

acclimatization 2 d

Duration of test (contact time):

10 d

Initial conc.:

>= 50 - <= 400 mg/L

Based on:

DOC

Initial conc.:

>= 200 - <= 1 000 mg/L

Based on:

COD

Parameter:

% degradation (DOC removal)

Value:

96

Sampling time:

10 d

Details on results:

90 % degradation during the log-phase (8 d)

The substance is inherently biodegradable (Wellens 1990).

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Executive summary:

m-Cresol is inherently degradable as shown by a test according to OECD guideline 302 B with a removal of 96 % of m-cresol after 10 days of incubation.

Description of key information

m-Cresol is readily biodegradable under aerobic conditions in freshwater. It is inherently biodegradable, and anaerobically biodegradable

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

Serveral experiments on biodegradability are available for m-cresol.

In the aquatic phase, the biodegradability of m-cresol was tested according to OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test). Degradation was 90 % after 28 d and the 10 d window was fulfilled.

In a test according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)), 80 to 95 % of m-cresol was degraded within 40 d. m-Cresol was slightly better biodegradable than phenol and aniline supporting the conclusion that it is readily biodegradable.

m-Cresol is inherently degradable as shown in a test according to the OECD guideline 302 B where 96 % of the added m-cresol was degraded within 10 days after a lag-period of 2 days, and by a similar test, with a removal of 96 % after 5 days of incubation. m- Cresol is also anaerobically biodegradable.

As measured from methane release and carbon dioxide formation, m-cresol is mineralized under methanogenic conditions by anaerobic sludges from wastewater treatment plants. Therefore, m-cresol is considered to be "Readily and Inherently" Biodegradable.

Although the substance is readily biodegradable and no biodegradation simulation test has to be performed for sediments, there are studies available on biodegradation in sediments. m-Cresol is biodegraded in aquifer sediment under anaerobic conditions and by anoxic river sediment within 3-4 weeks.