New Insights into the Chemical and Isotopic Composition of Human Body Biominerals. II: COM Kidney Stones from Greece

We have analyzed kidney stones from patients from Greece in which the mineral phase was calcium oxalate monohydrate (COM) as identified by powder-XRD and FTIR spectra. SEM-EDS analysis revealed microscale-COM crystal aggregates mixed with organic/biological matter. XRF revealed that in addition to Ca (max. ca. 21.4 wt.%; av. ca. 21 wt.%) and Sr (max. 35 ppm; av. 34 ppm), there were significant levels of heavy metal impurities, namely Zn (max. 214 ppm; av. 204 ppm), Pb (max. 149 ppm; av. 136 ppm), Fe (max. 136 ppm; av. 132 ppm) and Cu (max. 17 ppm; av. 15 ppm), as well as minor amounts of Br. As identified by IRMS, all three examined kidney stones presented a very light δ13C signature (average δ13C ca. -25.4‰ PDB) as compared to previously reported data on kidney stones from humans from different geographical locations. The δ18O values averaged ca. -7.31‰ PDB. With regard to radioactive isotopes, HR γ-ray spectrometry demonstrated the existence of the natural radionuclides 214Pb and 214Bi due to 238U-series, and also an additional amount of 40Κ. We conclude that these kidney stones from southeastern Europe are enriched in essential biometals (Zn and Fe), and also contain a high content of harmful heavy metals such as Pb, and traces of U. This elemental composition may be related to a toxic diet and/or environmental pollution.