Detection of plant-derived silica particle contamination in wheat flour: A first step toward understanding possible dietary exposure

Plant-derived silica structures (phytoliths) occur naturally in cereals such as wheat, but their role as unintended dietary contaminants has been underexplored. Using field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy (FESEM-EDX), we systematically detected and quantified sharp, needle-like siliceous spicules in wheat flour from two regions of northern China that differ in aridity and esophageal squamous cell carcinoma (ESCC) incidence. Flour from Linzhou (high-ESCC, high-aridity) contained nearly twice the spicule burden of Linfen (low-ESCC, low-aridity), corresponding to an estimated 2.4-fold higher daily intake. Controlled washing experiments showed up to ∼75% reduction in contamination, but residual levels persisted, suggesting a possible heavier contamination burden in Linzhou where limited water availability constrains washing practices. These findings provide quantitative evidence that dietary exposure to sharp biogenic silica particles is environmentally modulated by aridity and may contribute to geographic disparities in ESCC risk. While causality remains unproven, this work revitalizes the “glass root” hypothesis with modern quantitative data and highlights the need for larger surveys, agronomic studies, and biological assessments to clarify health implications. • Systematic quantification of plant-derived siliceous spicules in wheat flour. • Flour from high-ESCC arid regions contains nearly double spicule burden. • Washing reduces contamination but spicules persist under water shortage. • Findings provide quantitative support for the “glass root” hypothesis. • Findings highlight aridity-driven dietary exposure.