I wouldn't display my ignorance of science at the National Academy of Sciences, but Dr. Loewen didn't seem to have a problem with it (you can jump to 1:00 and just watch for a minute) last May:
He seems to think that because we've evolved in a bath of radiation, radiation doesn't cause cancer. That's fallacious. One of the contributors to gene mutations which allowed us to evolve to be humans is radiation. Radiation induces those same mutations in somatic (non-sex) cells and this leads to cancer. Humans get cancer, even those only exposed to background radiation.
Later on (around 4:20), when discussing nuclear waste he talks about how the NAS "is very clear" about what to do with radioactive. Well, they're also very clear that radiation causes cancer (see BEIR VII), but he is too biased to acknowledge it.