General Aspects of Metal Toxicity
H. Kozlowski, P. Kolkowska, J. Watly, K. Krzywoszynska and S. Potocki
Affiliation: University of Wroclaw, Faculty of Chemistry, Joliot-Curie 14 St. 50-383 Wroclaw, Poland.
Keywords: Metal toxicity, fenton reaction, heavy metals.
This review is focused on the general mechanisms of metal toxicity in humans. The possible and mainly confirmed
mechanisms of their action are discussed. The metals are divided into four groups due to their toxic effects. First
group comprises of metal ions acting as Fenton reaction catalyst mainly iron and copper. These types of metal ions participate
in generation of the reactive oxygen species. Metals such as nickel, cadmium and chromium are considered as
carcinogenic agents. Aluminum, lead and tin are involved in neurotoxicity. The representative of the last group is mercury,
which may be considered as a generally toxic metal. Fenton reaction is a naturally occurring process producing most
active oxygen species, hydroxyl radical:
Fe2+ + He2O2 ↔ Fe3+ + OH- + OH•
It is able to oxidize most of the biomolecules including DNA, proteins, lipids etc. The effect of toxicity depends on the
damage of molecules i.e. production site of the hydroxyl radical. Chromium toxicity depends critically on its oxidation
state. The most hazardous seems to be Cr6+ (chromates) which are one of the strongest inorganic carcinogenic agents. Cr6+
species act also as oxidative agents damaging among other nucleic acids. Redox inactive Al3+, Cd2+ or Hg2+ may interfere
with biology of other metal ions e.g. by occupying metal binding sites in biomolecules. All these aspects will be discussed
in the review.
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