I'd say your claim of no health risk is premature. Backscatter X-ray focuses the ionizing radiation on the surface of your skin and immediately underlying tissue, so the effective local dose on your skin is much higher than other types of X-ray which are distributed evenly throughout your body. This is of particular concern to men, whose reproductive organs are located near the surface of the skin, as X-ray exposure to reproductive organs in parents is associated with leukemia in their children. For medical X-rays, measures are taken to limit exposure to reproductive organs.