Objective To examine the dissolution of rare earth elements (REEs) in Pu′er tea and its influencing factors under different brewing conditions and to assess health risk associated with rare earth element exposure due to Pu′er tea drinking.
Methods Based on studies conducted between 2013 – 2015 in Gaungzhou city, we identified 3 categories of market available Pu′er tea with the REEs concentration of 0 – 2.0, > 2.0 – 5.0, and > 5.0 mg/kg and collected 5 samples (50 g for each) for each of the three categories of Pu′er tea and blended all the 15 collected samples into a mixed Pu′er tea sample (750 g). Then we simulated the process of kungfu tea making and daily Pu′er tea consumption to make Pu′er tea infusion samples under various brewing conditions. The contents of REEs in tea leafs, water used, and infusion were determined with inductively coupled plasma-mass spectrometry (ICP-MS).
Results The mean percentage of Pu′er tea REEs dissolved in the infusions was 5.73% under the brewing condition in daily Pu′er tea consumption. The content of REEs dissolution in Pu′er tea infusion was mainly affected by the amount of tea used, water temperature, and brewing time; the percentage of REEs dissolved was correlated reversely with the amount of Pu′er tea used and positively with water temperature and time of brewing. The mean percentage of Pu′er tea REEs dissolved in the tea infusions was 7.01% under the brewing condition in kungfu tea making and the percentage was the highest for the infusion of third time brewing among the infusions of a total of seven brewings.
Conclusion The dissolution ratio of REEs in Pu′er tea is low in tea infusion under various brewing methods and the amount of REEs intake via drinking Pu′er tea is very small in general populations; therefore the probability for health risk due to Pu′er tea drinking is very low for populations having Pu′er tea drinking under general consumption pattern.
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