Zinc is a naturally occurring element and is ubiquitous in the environment. Zinc itself is stable in dry air, but exposure to moist air results in the formation of zinc oxide or basic carbonate. Due to the reactivity of zinc metal, it is not found as a free element in nature but as a variety of different compounds including zinc chloride, zinc oxide, and zinc sulfate. Zinc and zinc compounds are used across a wide range of industries that include rubber production, animal feed supplementation, as a fertilizer additive, in cosmetics and drugs, as a paint pigment, in dental cements, as a wood preservative, in batteries, in galvanizing and metal work, in textile production, in television screens and watches, and in smoke bombs. Of the zinc compounds, zinc oxide is the most widely used. Zinc was nominated by the Agency for Toxic Substances and Disease Registry (ATSDR) for carcinogenicity and genotoxicity testing based on the increasing size of the population exposed to zinc through dietary supplements and the lack of studies examining the carcinogenicity of zinc. There was an additional nomination to investigate the tumorigenicity of zinc deficiency by private individuals as a result of data showing that deficiency of some vitamins and minerals in humans can cause DNA damage. Zinc carbonate basic was selected as the source of dietary zinc due to its use as the source of supplemental zinc in rodent diets. Male and female Hsd:Sprague Dawley SD rats were exposed to dietary zinc in feed for 2 years. Genetic toxicology studies were conducted in rat peripheral blood erythrocytes, peripheral blood leukocytes, and colon epithelial cells. (Abstract Abridged).
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