I know that is confusing. Theoretically blacks and oolongs are oxidized through the catalytic actions of the leaves’ enzymes. However, fungal spores exist all around us. Their activities on the tealeaves basically cannot be avoided. No one has (as far as I know) done any quantitative study of the amount of biochemical changes caused specifically by these spores. However, the same thing can be said of almost anything that happens not in a totally sterilized environment. That should be 99% of human activities.
Fungal content and bacteria in tea are tested by a standard almost as demanding as vegetable used for your salad, so there should be no worry about it. A customer of mine used to eat oolong leaves (before steeping for tea) like potato chips as she watched tv. I worry more about caffeine overdosage for her more than anything else 😉
