Re Bra phone transport and breast cancer, clearly there will be an association, as the woman is frequently doing breast self examination! There was, for a brief period of time, an association (NOT causal ) with breast trauma and cancer from precisely the same issue.
Causality is best determined by
1. Randomised Intervention study, preferably double blind, NOT a cross sectional study.
2. Demonstration of a dose response curve/association
High power RF is good at cooking things, intended or not. My homebrew EME 1296MHz transmitter puts out about 400W, I am careful but not paranoid.