Human exposure asseessment to different arsenic species in tea.

Background: Inorganic forms of arsenic are much more highly toxic to humans than organic species. Their effects include being carcinogenic, genotoxic and neurotoxic, where in the latter case, above all, they affect nervous system development in the foetus, infants and children. The main foodstuffs contributing significantly to its total dietary intake are drinking water, rice (and its products), fish, seafood, cereals, seaweed, root vegetables, food supplements, mushrooms and tea. After water, tea is the second most popular beverage drunk in Poland with average consumption annually indicating that statistically every Polish inhabitant drinks at least one cup of tea daily.

Objectives: The aim of the study was to determine the total and inorganic content of arsenic in various black and green teas available on the market and thus to estimate consumer exposure to inorganic arsenic from this foodstuff.

Materials And Methods: Analyses of total and inorganic arsenic were performed on 23 samples of black and green teas that consisted of tea leaves, teas in bags and granules, from various sources. The analytical method was hydride generation atomic absorption spectrometry (HGAAS), after dry ashing of samples and reduction of arsenic to arsenic hydride using sodium borohydride. In order to isolate only the inorganic forms of arsenic prior to mineralisation, samples were subjected to concentrated HCl hydrolysis, followed by reduction with hydrobromic acid and hydrazine sulphate after which triple chloroform extractions and triple 1M HCl re-extractions were performed. Exposure of adults was estimated in relation to the Benchmark Dose Lower Confidence Limit (BMDL05) as set by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) that resulted in a 0.5% increase in lung cancer (3.0 μg/kg body weight (b.w.) per day).

Results: Green teas were found to be more highly contaminated with both total and inorganic arsenic than black teas. Contamination of black teas total and inorganic arsenic was mean: 0.058 mg/kg (median: 0.042 mg/kg, 90th percentile: 0.114 mg/kg), and 0.030 mg/kg, (median: 0.025 mg/kg, 90th percentile: 0.030 mg/kg) respectively. Whilst for the green teas, these were correspondingly mean total arsenic content: 0.134 mg/kg (median: 0.114 mg/kg, 90th percentile: 0.234 mg/kg) and inorganic arsenic, mean: 0.100 mg/kg (median: 0.098 mg/kg, 90th percentile: 0.150 mg/kg). The estimated average adult exposures to inorganic arsenic in black and green tea were less than 1% of the BMDL05. Green tea samples, with the highest measured inorganic arsenic, were found to cause an intake exceeding 0.5% of the BMDL05 value. However when the drinking water is also accounted for when teas are prepared, then the exposure from black and green tea becomes exceeding 0.7% and 1.3% of the BMDL05 value respectively.

Conclusions: Findings thus demonstrate that drinking black or green teas does not pose a significant health threat to consumers, even though contaminations in some individual samples were significant.

Key Words: total arsenic, inorganic arsenic, tea consumption, exposure assessment.