Does bha and/or bht cause cancer? if yes, in what quantities?

No: These are food preservatives that prevent fat spoilage. Since they do not mutate dna, any claims that they "cause cancer" are almost certainly rubbish. Every chemical known to humankind has been accused of causing cancer, attention deficit disorder, and whatever else -- there's big money in peddling fear -- and the iron is that bht has also been sold in health food stores as a supplement.

Possible no conclusi: Bha (butylated hydroxyanisole ) bht ( b. Hydroxy touline ) are synthetic hydro carbons, widely used as fat preserves, cosmetics, & anti viral as in herpes simplex there are proponents and opponents for the use ( in low concentration of less than quarter % or less) not considered overly toxic , anti oxidants & chemo-protective agents in cancer. Opponents argue they cause cancer of lung etc.