There are many investigations, which have documented clean up from about 2,000 down to about 200 mg total PAH/kg with time scales of 6 months to several years. Generally, it is difficult to calculate the time scale for biological techniques.

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Therearemanyinvestigations,whichhavedocumentedcleanupfromabout2,000downtoabout200mgtotalPAH/kgwithtimescalesof6monthstoseveralyears.Generally,itisdifficulttocalculatethetimescaleforbiologicaltechniques.