Hmmmm....... I never worry about this kind of thing. Oxygen is a carcinogen and I breathe that every day. Smokers generally get through 30 to 50 years of a dangerous mix. I reckon tea and coffee are way, way, way down the list.
In the 19th century, Europeans in the Orient who drink water
got very ill. The locals drank tea and stayed healthy. In Europe
our ancestors drank wine and beer
before tea came along as alcohol sterilised the water
and killed off the organisms in it. Boiling water for tea does the same.
Having said all that, there's nothing like a glass of chilled grapefruit juice first thing in the morning to clear the mouth of the nighttime fuzz.