Rare Earth Element and Yttrium Fingerprints in Human Kidney Stones: Tracing Environmental Exposure and Pathological...

Rare earth elements and yttrium (REE + Y) are increasingly mobilized in modern environments, affecting human physiological processes through multiple exposure pathways. Pathological biominerals, such as kidney stones, may provide valuable records of long-term elemental deposition. However, it remains unclear whether REE + Y directly inherit environmental signals or are reshaped by physiological and mineralogical processes. This study analyzed kidney stones from a high-incidence karst region in eastern Yunnan, China. The results indicate that regional hydrogeochemical background and the mineralogical pathways jointly control the REE + Y distribution of kidney stones. Fourier transform infrared spectroscopy combined with non-negative matrix factorization identified the dominant spectral components and their relative proportions in the stones. The total REE + Y load was mainly controlled by the dominant mineral phase, with the median in uric acid stones (36.4 ng/g) remaining significantly lower than in calcium-bearing stones (up to 218.2 ng/g). This study further found that increasing phosphate proportions were significantly correlated with weaker Yb anomalies and higher Lu concentrations, whereas total REE concentrations showed no significant change. Unsupervised and supervised model analyses demonstrated that REE + Y distribution patterns can reliably distinguish stones with different dominant mineral types. These results indicate that REE + Y are sensitive to biomineralization processes in kidney stones and may serve as potential tracers for apatite incorporation in calcium-bearing stones. Moreover, although human metabolism and biomineralization filter most environmental signals, the light REE-enriched patterns in calcium-bearing stones are broadly compatible with the karst hydrogeochemical background. Overall, this study reveals the REE + Y fingerprints support precise subtyping of kidney stones, serving as composite geochemical archives reflecting both environmental signals and pathological biomineralization.