Comparative assessment of heavy metal exposure and health risks in khaini and filtered khaini smokeless tobacco products

Smokeless tobacco (SLT) products are widely consumed in India, contributing significantly to the burden of oral cancer and systemic diseases. Despite their popularity, limited data exist on heavy metal contamination and associated health risks, particularly for filtered khaini, which is often perceived as safer than traditional khaini. Thus, the objectives of the study are to quantify heavy metal concentrations in khaini and filtered khaini and evaluate the associated non-carcinogenic and carcinogenic health risks. Samples of filtered khaini (FK) and conventional khaini (K) were analysed for 20 heavy metals using inductively coupled plasma mass spectrometry (ICP-MS). Mean concentrations were compared using the Mann–Whitney U test. Estimated daily intake (EDI), hazard quotient (HQ), hazard index (HI), and target cancer risk (TCR) were calculated based on oral (buccal) exposure scenarios at absorption fractions of 6%, 20%, 25%, and 100%. Cancer slope factors (CSFs) were derived from U.S. EPA and WHO databases. FK contained significantly higher concentrations (p ≤ 0.05) of Pb, Cd, As, Cr, Ni, Co, Cu, Zn, Fe, Mn, Al, Ba, V, Se, U, and Be than khaini. Non-carcinogenic risk assessment at 25% absorption yielded an HI = 1.224 for FK and 0.592 for khaini, indicating potential chronic health effects for the former. The total target cancer risk at 6% absorption was 0.264 for FK and 0.147 for khaini, dominated by arsenic and cadmium contributions. FK exhibits markedly higher heavy-metal contamination and health-risk indices than traditional khaini. Both products present lifetime cancer risks far exceeding acceptable limits (10⁻⁶–10⁻⁴), underscoring the need for regulatory surveillance and public-health intervention to mitigate oral and systemic toxicity from smokeless-tobacco use.