White tea was found to inhibit DNA mutation more effective than green tea. This is why Chinese white tea becomes popular in USA and Europ, for its benefit effect of cancer prevention.
White tea is produced in China only. It is a rare strain of tea plant, and processed by simply steaming and drying. White tea leaf is so light that it won't drop down from the outlet of tea bag packaging machine. So, real white tea is leaf tea, but not in tea bag. Due to popular interest, however, some manufacturers take green tea, processed in way of making white tea, sell them as white tea. So, what ever white tea in tea bag you see in market is green tea in nature.