Highly toxic thallium in plants from the vicinity of Olkusz (Poland)

Thallium is a highly toxic metal that plays no role in the metabolism of plants or animals. Recent studies using small mammals and bird feathers as bioindicators demonstrated for the first time that animals from the vicinity of the Bolesław metal works near Olkusz (southern Poland) had large amounts of thallium in their tissues. Because of concern over these reports, four plant species (Plantago lanceolata, Biscutella laevigata, Dianthus carthusianorum, Silene vulgaris) growing wildly in the same area on a 100-year-old calamine waste heap, as well as the waste heap soil, were examined. The average concentration of thallium in the waste heap soil was 43 mgTl/kg dry wt, with the highest value 78 mg Tl/kg dry wt. P. lanceolata accumulated extremely large amounts of thallium (average, 65 mg Tl/kg dry wt; maximum 321 mg Tl/kg dry wt in roots). S. vulgaris and D. carthusianorum accumulated much less (averages, 10 and 6.5 mg Tl/kg dry wt, respectively). On the other hand, B. leavigata accumulated negligible amounts of thallium in its tissues. The concentration of thallium in plants (shoots, roots) from the calamine waste heap was 100-1000 times the level normally found in plants (0.05 mg Tl/kg dry wt). Possible sources of thallium are discussed and the urgent need for large-scale studies on thallium contamination of soils and vegetation in Poland, especially its southern regions, which are the most industrialized, is pointed out.