Each product was also tested for lead exposure (a common contaminant in botanical supplements), and researchers found traces in many of the products’ leaves. “Green tea leaves are known to be sponges for lead, and our research confirmed varying amounts in the brewed material,” says Cooperman. “However, the tea itself contained very little, meaning much was filtered out in the brewing process and any remaining levels pose no health threat.” So that’s good news, but it still makes you think.