Heavy metal assessment of tea leaves and infusions
Other than water, tea is the most consumed beverage worldwide and constitutes a significant part of our diet. However, heavy metal content of tea leaves has been a major health concern associated with tea consumption. To inform consumers and stakeholders, the carcinogenic and non-carcinogenic health risk assessment for heavy metals in tea was conducted. A total of 45 tea (Camellia sinensis) samples from China, India, and the USA, including black and green tea were analyzed for nine heavy metals (Ag, As, Ba, Cd, Cr, Cu, Pb, Se, and Zn) using both the tea leaves as well as three types of tea infusions prepared based on various tea drinking habits. The results showed that country of origin had a significant influence on Ba, Cr, Pb, and Zn contents in tea and on As, Ba, Cd, Cr, Pb, and Zn contents in tea infusions. The Cr and Cu contents in black tea were significantly higher (p < 0.05) than in green tea. However, only the Cr content in black tea was significantly higher (p < 0.05) than that of the green tea in tea infusion. Among the three types of infusions, the heavy metal contents were the highest in the first infusion and decreased as the number of infusion steps increased. Subsequently, the results were used for health risk assessment of these heavy metals for both non-carcinogenic and carcinogenic risk. For non-carcinogenic risk, the trend of mean hazard quotient (HQ) values was in the order of As > Cr > Cu > Pb > Se > Zn > Cd > Ba > Ag. The hazard index (HI) values, representing combined non-carcinogenic effects of the studied heavy metals, were well below one, indicating that the consumption of tea infusion is not likely to cause non-carcinogenic risk. However, the carcinogenic risk for As was of concern; R > 1.0 × 10-5. Our results indicate that avoiding drinking the first infusion can help to reduce both carcinogenic and non-carcinogenic health risks for heavy metals.