Registration Dossier

Diss Factsheets

Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

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.

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
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.

Key value for chemical safety assessment

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.