I take 4 antioxidants and sometimes about selenium. What do you think?

I take four antioxidants (beta-carotene, vitamin E, vitamin C and selenium). I wonder sometimes about the selenium. I have broken my organic selenium tablets in half and take a half a day, which is about 30 micrograms. What do you think? After hearing researchers report on various cancers (gastrointestinal and skin), I found the evidence...