Lead contamination is a concern
Even organically grown green teas have been shown to contain lead, which is absorbed by the plant from the environment, particularly tea grown in China. When traditional green tea is steeped, about 90% of the lead stays in the leaf, which is discarded. With matcha, since the whole leaf is consumed, you will ingest more lead. One independent group, ConsumerLab.com, which tested teas, estimates that a cup of matcha may contain as much as 30 times more lead than a cup of green tea. Therefore, they recommend drinking no more than one cup daily, and not serving it to children.