Without getting into details about my own personal medical history, I'll tell you this. The millimeter wave scanners emit nonionizing radiation that is not believed to produce DNA damage that would lead to cancer. However, they use a form of electromagnetic radiation in a spectral region that can produce thermal effects, that is, heat. It's believed that the exposure we're talking about here doesn't actually heat tissue, but no one has determined the long-term effects of exposure (if any). Since it's easy for me to opt out, I do.

I take lots of other known and unknown risks in my life. This one I skip. Happy to live in a world where I get to make that choice for myself, and you get to make that choice for yourself.