Green tea plants are known to be especially effective at absorbing lead from the soil, which is then taken up into the plant's leaves. Areas with excessive industrial pollution, such as China (where nearly 90% of the world's green tea is produced),3 may therefore contain substantial amounts of lead.4
According to the ConsumerLab.com analysis, tea from brands like Lipton and Bigelow contained up to 2.5 micrograms of lead per serving compared to no measurable amounts in Teavana brand, which gets its tea leaves from Japan.
While the lead in the tea leaves is not thought to leach very effectively into the tea you end up drinking, if you're consuming Matcha green tea, one of my favorites, it's especially important that it comes from Japan instead of China. Matcha tea contains the entire ground tea leaf, and can contain over 100 times the EGCG provided from regular brewed green tea.
That said, because you're consuming the entire leaf, you want to be sure it comes from a non-polluted, high-quality source. The best Matcha green tea comes from Japan and is steamed, rather than roasted or pan-fried. As a result, Matcha green tea retains all the nutrient-rich value possible from the tea leaf, without additives or contaminants.