Sequential multielement analysis of Cd, Cr, Hi, and Pb in human tissues by inductively coupled plasma spectrometry

The role of trace metals in cancer has been the subject of conjecture, and reports of different authors are often conflicting and contradictory. Attention is focused primarily on a) four metals (As, Cd, Cr, and Ni) that have been implicated as human carcinogens on the basis of epidemiological investigations, and b) compounds of nine metals (Be, Cd, Co, Cr, Fe, Ni, Pb, Ti, and Zn) that have been reported to induce cancers in experimental animals (Sunderman 1978; Frust, 1977; Aitio and Tomatis 1991; Magos 1991). Most toxic elements affect multiple organ systems, with specific biochemical processes and (or) organelles as targets. Their toxic effect usually involves an interaction between the free metal ion and the specific target protein. Cells or organs involved in the transport of trace metals, i.e., muscle, liver, renal tubular, or gastrointestinal cells, are particularly susceptible to toxicity. Most of these elements are concentrated intracellulary; heavy metals deposit in tissue after exposure. There are three principal binding sites for metals on the nucleic acid molecules: the phosphate groups, the heterocyclic bases and the 2-OH groups in the case of RNA (Eichhorn et al 1979). It is generally accepted that a combination of environmental factors and life-style contribute to about 70-90% of cancer cases. The most important factors are smoking (about 30-40%) and food (30-50%), whereas environmental pollution contributes only a small percentage (1-3%). Augustin and Zejda (1991) found that geochemical factors in the environment such as radioactive elements and heavy metals were possible causes of the high incidence of cancers in some districts in Czechoslovakia. In view of conflicting reports in the literature, the concentrations of Cd, Cr, Ni and Pb were determined in the kidney and brain of Saudi patients with malignant or benign tumors.