o-cresol

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sewage treatment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Principles of method if other than guideline:

biodegradation process by phenol acclimated activated sludge; identifying of metabolic intermediates

GLP compliance:

no

Radiolabelling:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, adapted

Details on inoculum:

activated sludge was cultured by a medium containing phenol as the carbon source over a period of more than a year in a 4-l laboratory unit, concentration of microorganism in dry weight was 950 mg/l

Duration of test (contact time):

24 h

Initial conc.:

200 mg/L

Based on:

test mat.

Parent/product:

parent

Compartment:

water

Parameter:

test mat. analysis

Remarks on result:

not measured/tested

Compartment:

natural water: freshwater

Type:

(pseudo-)first order (= half-life)

Temp.:

12 °C

Remarks on result:

other: not assessed

Transformation products:

yes

No.:

#1

No.:

#2

No.:

#3

Evaporation of parent compound:

no

Volatile metabolites:

no

Residues:

not specified

o-cresol was first transformed to three dihydroxytoluenes

Validity criteria fulfilled:

not applicable

Conclusions:

The metabolic pathway of o-cresol was examined using phenol-adapted sludge. The primary metabolic step is the ring-hydroxylation yielding isomers of dihydroxy-toluene (3-methyl-catechol, 4-methyl-resorcinol, methylhydroquinone). Secondary degradation products are formed either by further hydroxylation yielding trihydroxy and tetrahydroxy-toluenes or by cleavage of the aromatic ring system.

Executive summary:

The o-cresol metabolic pathway was examined by Masunaga (1986) using a phenol-adapted activated sludge. About 90% of the o-cresol is degraded after 24 hours and the metabolites also diminish significantly with time. The primary metabolic step is the ring-hydroxylation yielding isomers of dihydroxy-toluene (3-methyl-catechol, 4-methyl-resorcinol, methylhydroquinone). Secondary degradation products are formed either by further hydroxylation yielding trihydroxy and tetrahydroxy-toluenes or by cleavage of the aromatic ring system.

Reference 2

Endpoint:

biodegradation in water: sediment simulation testing

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance is readily biodegradable

Transformation products:

not specified

Reference 3

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance is readily biodegradable

Transformation products:

not specified

Description of key information

The primary metabolites of o-cresol by phenol-adapted activated sludge were 3 -methylcatechol, 4 -methylresorcinol and methylhydroquinone.

Additional information

Although readily biodegradable, the o-cresol metabolic pathway was examined by Masunaga (1986) using a phenol-adapted activated sludge. About 90% of the o-cresol is degraded after 24 hours and the metabolites also diminish significantly with time. The primary metabolic step is the ring-hydroxylation yielding isomers of dihydroxy-toluene (3-methyl-catechol, 4-methyl-resorcinol, methylhydroquinone). Secondary degradation products are formed either by further hydroxylation yielding trihydroxy and tetrahydroxy-toluenes or by cleavage of the aromatic ring system.