The assessment of soil contamination by persistent substances is based on a multi-level system of criteria of contents, mobilities and transfer of hazardous trace elements into organisms and of contents and behaviour of organic xenobiotic substances, which reflects the increasing risks. The basis of the assessment are background values of contaminants, which represent the upper limit of the variability of natural and anthropogenic diffuse contents. The development of the eco-, zoo- and humanotoxicologically relevant criteria is supported by risk assessments, which are additionally performed to verify the on-site risk after the limits have been surpassed. Cooperation is needed among toxicologists of human and veterinary medicine, sanation specialists and soil scientists.

        Key words: soil contamination, persistent contaminants, trace elements, organic xenobiotic substances, bac- kground values, reference values, protection of food chain, humans health.