Toxic polychlorinated dioxins and dibenzofurans have been identified in effluents and products from pulp and paper mills using chlorine bleaching. The amounts and levels depend on the bleaching technique used and the product quality. The same compounds have also been identified in sediment samples and aquatic organisms collected in the vicinity of pulp mills. The highest levels were found in hepatopancreas from crustaceans. Much higher levels of alkyl-substituted polychlorodibenzofurans have been found in sediment and sludge samples.