Absorption and elimination of [C-14-4,5,9,10]pyrene and production of water-insoluble and water-soluble pyrene metabolites by the polychaetes Nereis diversicolor and Arenicola marina were studied. Both polychaete species were capable of rapidly accumulating and eliminating pyrene. Steady state concentrations of pyrene were established in both polychaete species within 5 days of exposure to contaminated sediments, with A. marina having 5-10 times higher bioaccumulation factors than N. diversivolor. Both water-soluble and water-insoluble metabolites were detected in tissues of N. diversicolor and A. marina. After transferring worms to uncontaminated sediment, about 50% of the body burden of parent pyrene was excreted within 1.5 days, with elimination in A. marina being faster than in N. diversicolor. The only identified water-insoluble metabolite produced by N. diversicolor was 1-hydroxypyrene. Pyrene metabolites were present in A. Marina, but could not be identified. Long- and short-term absorption experiments showed an increasing production of water-soluble metabolites over time in the lugworm, which strongly suggests the presence of a PAH metabolising system in A. marina. (C) 2002 Elsevier Science B.V. All rights reserved.