From rice grain to human hair: Assessing dietary heavy metal exposure and health risks in Narsingdi, Bangladesh.

Heavy metal contamination in rice poses significant health risks, yet comprehensive assessments across ages and genders, including hair samples and dietary habits, are rare. This study evaluates metal(loids)-chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), and lead (Pb)-in soil, rice, water, and hair from Narsingdi District, Bangladesh, assessing health risks linked to dietary habits. Localized Cd concentration in soil was dominant. Water samples exceeded safety guidelines. Rice grains (n = 111) had mean concentrations (mg/kg): Cr (0.83), Ni (0.74), Cu (6.44), Zn (19.43), As (0.16), Cd (0.26), and Pb (2.47). Overall, 60.4 % of the grains exceeded the WHO recommended limits for Cr, Cu, Cd, Ni, and As. The mean concentrations (mg/kg) of human hair (n = 101) were Cr (2.58), Ni (2.27), Cu (26.75), Zn (33.90), As (0.85), Cd (1.0), and Pb (9.93), with significant differences across age groups. Notably, the 50 and above 50 aged groups contained higher metal(loids) than the smaller groups, together males contained higher metal(loids) in hair than females' hair. Pairwise Pearson correlation confirmed strong correlations (r > 0.90**) among soil, grain, water, and hair metal(loids) concentrations. Around 14 % of each metal(loids) was confirmed by Principal Component Analysis among the different samples. Pairing 63 participants' hair samples with their rice consumption patterns showed a significant positive association between rice consumption and hair metal concentrations (p < 0.001). Higher rice intake (≥450 g/day) was linked to elevated hair metal concentrations compared to lower rice intake (≤ 350 g/day). All participants exceeded reference doses for As, Cd, Pb, and Cu, with the highest risk in children aged 0-15. The Hazard Index ranked above 1 for Pb, As ≃ Cd, and Cu, while carcinogenic risk exceeded the threshold (ILCR>0.0001). These results emphasize the urgent need for ongoing monitoring of dietary habits to mitigate harmful metal(loids) exposure.