A method of decontaminating a medium containing polychlorinated biphenyls (PCBs) or dioxins is disclosed. The contaminated medium is brought into contact with hairy roots derived through introduction of an Ri plasmid from Agrobacterium rhizogenes into a plant capable of absorbing, or absorbing and decomposing PCBs or dioxins, or is brought into contact with regenerated plantlets derived from the hairy roots, to thereby cause the hairy roots or regenerated plantlets to absorb, or absorb and decompose PCBs or dioxins.
