Ia. Alsaleh et I. Aldoush, SEQUENTIAL MULTIELEMENT ANALYSIS OF CD, CR, HI, AND PB IN HUMAN TISSUES BY INDUCTIVELY-COUPLED PLASMA SPECTROMETRY, Bulletin of environmental contamination and toxicology, 57(4), 1996, pp. 511-516
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.