Radiation causes genetic mutation and every (human) cell in our body have the same genes. But on Earth we don't get cancer as often in the foot as in the genitals or in the brain. Some parts of our physiology are more complex untested and sensitive than others.
- Could an astronaut be well protected by wearing only a (perfectly shielded) helmet and a hauberk, or even a backpack to cover half of her upper body?
- What happens to me if, say, my left foot was exposed to off the scale super radiation? Would I get acute radiation sickness? Would it give me brain cancer later on?
The idea here is that maybe we could do an 80/20 by shielding only the "upper" half of a spaceship. And of course by wearing funny clothes.