Toxicity as a Biogeochemical Problem.

The concept of toxicity is analyzed from the standpoints of theoretical biogeochemistry and geochemical ecology. The phenomenon of toxicity is demonstrated to appear and be able to significantly manifest itself only as a consequence of anthropogenic disturbances of self-regulation systems and dynamic equilibria that existed in natural biogeochemical cycles throughout the whole history of the biosphere. Thanks to these phenomena and in spite of unequilibrated distribution of elements in natural environments, all living organisms practically always coexisted in optimal geochemical environments. All chemical elements, which are always present in habitats, are needed for the adequate existence of living organisms, and hence, there are no undeniably and absolutely toxic elements, but instead these there are toxic dozes of elements able to induce toxic effects. It is important that deviations to both higher and lower concentrations from the optimal ones are equally hazardous, and hence, some organisms can be damaged by artificial deficits in some elements, whose ecological–geochemical properties are still understood inadequately poorly. The paper discusses the possibility of applying a new approach to solving the problem, and this is illustrated by mapping the distribution of the risk of thyroid carcinoma. [ABSTRACT FROM AUTHOR]