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Environmental fate & pathways

Biodegradation in soil

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Description of key information

In several batch experiments using soil systems, degradation of naphthalene occurred efficiently under aerobic conditions: following an acclimatisation period/lag phase ranging from 2-12 days, degradation was accomplished within 10 days.

Key value for chemical safety assessment

Additional information

In none of the three reports, which were taken into account, a half-life value has been assessed, but it can be concluded that naphthalene is readily biodegradable under aerobic test conditions.

In the Environment Addendum of December 2007 to the EU Risk Assessment of naphthalene (UK 2007), a very conservative half-life of 300 days in soil has been reported (based on model calculations of Mackay et al. 1992).

This not well founded conclusion should not be taken for granted for a potentially easily degradable substance like naphthalene, even though evaluable long-term elimination data are lacking. (compare: Biodegradation in water-sediment systems).

By weight of evidence, it can be concluded that naphthalene is easily/inherently degradable without signs of bioaccumulation.

The limiting factor is anoxic/anaerobic conditions which also may occur in soil, but potential naphthalene degraders are ubiquitous in soil.

References:

UK 2007: Environment Addendum of December 2007 to the EU Risk Assessment of naphthalene, final approved version. UK Environment Agency, Chemicals Assessment Unit [R020_0712_env].

Mackay D, Shiu WY, and Ma KC 1992: Illustrated Handbook of Physical–Chemical Properties and Environmental Fate of Organic Chemicals. Lewis Publishers, Boca Raton, FL.