Interplay between essential and toxic metals: A cross-sectional study of blood metal levels and interactions in residents of agricultural and coal mining areas.

This study assessed blood levels and interrelationships of toxic (Pb, Cd, Cr) and essential (Fe, Zn, Cu, Co, Ca) metals in adult male residents of a rural coal mining area (rCMA, n = 63) and an unexposed agricultural area (rAA, n = 60). All participants were healthy, disease-free, and had lived in their respective locations for over five years. Mean blood concentrations of Pb, Cd, Fe, Cu, and Co were significantly higher in rCMA than in rAA (p < 0.05). Among toxic metals, Pb showed the highest apparent absorption and retention. Pb and Cd were strongly correlated in both groups (r = 0.50-0.60, p < 0.0001), and, in rCMA, both metals exhibited negative associations with Fe and Ca, suggesting interference with essential mineral metabolism. Iron was inversely associated with Zn and positively correlated with Co, indicating potential nutrient imbalances, including Zn deficiency, under elevated Fe exposure. These results demonstrate that chronic, low-level exposure to multiple environmental metals can alter essential nutrient dynamics even when individual metal concentrations remain below toxic thresholds. The findings underscore the importance of incorporating multi-metal interaction into environmental health monitoring and developing targeted nutritional strategies for populations in industrially impacted regions.