**7. Discussion**

Concentrations of uranium are quite variable in the phosphate products. The average ratio of phosphorus to uranium in phosphates appeared not to be only related to their origin since all tested Brazilian phosphates are from igneous deposits (ratio varying from 1000-4000 atoms of phosphorus to 1 atom of uranium), instead the foreign data are related exclusively to sedi‐ mentary rocks (ratio varying from 300-2400 atoms of phosphorus to 1 atom of Uranium). Differences amongst tested products are the region of exploitation of phosphate ores that implies different ages of mineralization, deposit types and accessory minerals associated that may vary in phosphates of the same origin, and finally they are separated by the routes of production of each final product for those are industrialized.

No significant difference was observed in uranium presence in the muscle tissues from rabbits (tab. 6) receiving dicalcium phosphate and those animals receiving bovine bone meal: average uranium content are 1.25 ± 0.45 μg.g-1 for dicalcium phosphate fed group and 0.91 ± 0.29 μg.g-1 for the bovine bone meal fed group. Possibly, *longissimus dorsi* muscle is not a target tissue for uranium in mammals. Indeed, uranium is often associated to replace calcium in the bone hydroxyapatites; both are considered mutual inorganic cation exchangers in apatite [21].

IAEA International Atomic Energy Agency

USDA United States Department of Agriculture

USP University of Sao Paulo

PHS Public Health Service

ppb parts per billion

ppm parts per million

ppt parts per trillion

yr year

> greater than

= equal to

< less than

% percent

β beta γ gamma

μm micrometer

μg microgram

**Acknowledgements**

α alpha

δ delta

PMR proportionate mortality ratio

USEPA United State Environment Protection Agency

Brazil

pg picogram

pmol picomole

IPEN *Instituto de Pesquisas Energéticas Nucleares* Nuclear Energy Research Institute, São Paulo,

Nuclear Analytical Techniques in Animal Sciences: New Approaches and Outcomes

http://dx.doi.org/10.5772/55071

189

This project is partially supported by: the Minas Gerais State Research Funding Agency FAPEMIG, the Brazilian Ministry of Science and Technology of Brazil via CNPq and the Brazilian Ministry of Education via CAPES/School of Veterinary from the Universidade Federal de Minas Gerais. We appreciate every support from CDTN/CNEN in particular we wish to thank its employee, Dr. Maria A.B.C. Menezes who supported us in our analyses.
