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Biodegradation behaviour of o-cresol was assessed in several experiments showing that the substance is readily as well as inherently biodegradable in water and soil.

Primary metabolic intermediates of o-cresol using phenol-adapted activated sludge were 3 -methylcatechol, 4 -methylresorcinol and methylhydroquinone. Secondary degradation products are formed either by further hydroxylation yielding trihydroxy and tetrahydroxy-toluenes or by cleavage of the aromatic ring system.

Aerobic degradation experiments in soil yielding a half-life times of 1.6 d for the sandy loam (basic soil) and 5.1 d for the sandy silt loam (acidic soil).

No anaerobic degradation was observed in primary anaerobic sludges from 12 treatment plants receiving mainly domestic wastewater.

o-cresol is readily biodegradable under aerobic conditions. Therefore, if released to wastewater or surface water, it is unlikely that o-cresol will reach the anaerobic zones. Anaerobic degradation is expected to be of minor importance for the hazard assessment of o-cresol.