What causes boob cancer? i've heard it's the pill, but what about chest x-rays, or other chemicals?

Yes: Carrier of genetic mutation, postmenopausal hormone replacement, chest radiation, obesity, nulliparity.

No one knows: Almost certainly not the pill. One theory that i like links the increase in breast cancer to pesticides that were used so much in the 50's and 60's. Chemically many of these pesticides resemble estrogen. It is notable that puberty is occuring at younger ages in the us. Hormones in food is another interesting theory. A regular chest xray probably ok - frequent exposure definitely not ok.