Evaluation of phytotoxicity and cytotoxicity of industrial catalyst components (Fe, Cu, Ni, Rh and Pd): A case of lethal toxicity of a rhodium salt in terrestrial plants

Until recently, chemical derivatives of platinum group metals have not been in a systematic direct contact with living organisms. The situation has changed dramatically due to anthropogenic activity, which has led to significant redistribution of these metals in the biosphere. Millions of modern cars are equipped with automotive catalytic converters, which contain rhodium, palladium and platinum as active elements. Everyday usage of catalytic technologies promotes the propagation of catalyst components in the environment. Nevertheless, we still have not accumulated profound information on possible ecotoxic effects of these metal pollutants. In this study, we report a case of an extraordinarily rapid development of lethal toxicity of a rhodium (III) salt in the terrestrial plants Pisum sativum, Lupinus angustifolius and Cucumis sativus. The growth stage, at which the exposure occurred, had a crucial impact on the toxicity manifestation: at earlier stages, RhCl3 killed the plants within 24 h. In contrast, the salt was relatively low-toxic in human fibroblasts. We also address phytotoxicity of other common metal pollutants, such as palladium, iron, nickel and copper, together with their cytotoxicity. None of the tested compounds exhibited phytotoxic effects comparable with that of RhCl3. These results evidence the crucial deficiency in our knowledge on environmental dangers of newly widespread metal pollutants.