Heavy metal contamination and health risk assessment of tea in Guangzhou, China

This study evaluated heavy metal contamination and health risks in tea consumed in Guangzhou. Fifty tea samples (green, black, oolong, and dark) from three districts were digested using an optimized microwave protocol with diluted nitric acid (~42% HNO₃), achieving complete matrix decomposition, stable recoveries (95–110%), and reduced acid use. ICP-MS quantified As, Cd, Cr, Cu, and Pb, while Hg was measured using an automatic mercury analyzer. Metals were detected in 96–100% of samples, with mean concentrations (mg/kg) following Cu > Cr > Pb > As > Cd > Hg. Dark tea accumulated the highest levels, and district differences reflected environmental contamination, with no significant tea variety × district interaction. Health risk assessment showed non-carcinogenic risks (HI) within acceptable limits for all groups, whereas total carcinogenic risk (TCR) exceeded 1×10⁻⁴ in several tea types, particularly among females (Green: 1.34×10⁻⁴; Black: 1.25×10⁻⁴; Dark: 2.10×10⁻⁴) compared with males (Green: 1.16×10⁻⁴; Black: 1.08×10⁻⁴; Dark: 1.82×10⁻⁴), highlighting potential long-term carcinogenic concerns. Arsenic was the main contributor. These findings provide region-specific evidence of Guangzhou tea contamination and demonstrate that the optimized microwave digestion method allows accurate, environmentally considerate heavy metal analysis.