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 contradict ory. Attention is focused primarily on a) four metals (As, Cd, Cr, and Ni) that have been implicated as human carcinogens on the basis of ep idemiological investigations, and b) compounds of nine metals (Be, Cd, Co, Cr, Fe, Ni, Pb, Ti, and Zn) that have been reported to induce can cers in experimental animals (Sunderman 1978; Frust, 1977; Aitio and T omatis 1991; Magos 1991). Most toxic elements affect multiple organ sy stems, with specific biochemical processes and (or) organelles as targ ets. Their toxic effect usually involves an interaction between the fr ee 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 d eposit in tissue after exposure. There are three principal binding sit es for metals on the nucleic acid molecules: the phosphate groups, the heterocyclic bases and the 2-OH groups in the case of RNA (Eichhorn e t al 1979). It is generally accepted that a combination of environment al 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 t he environment such as radioactive elements and heavy metals were poss ible causes of the high incidence of cancers in some districts in Czec hoslovakia. In view of conflicting reports in the literature, the conc entrations of Cd, Cr, Ni and Pb were determined in the kidney and brai n of Saudi patients with malignant or benign tumors.