Just as the “inverse square” law applies to photography lighting, it also applies to radiation.
Double the distance to get 1/4 the light or radiation.
What if the distance is halved? Exposure quadruples.
What if a radioactive isotope is IN CONTACT with tissue? Reverse inverse-square?
Comparing the energy of prolonged, direct contact with inhaled or ingested radioactive isotopes with bananas, x-rays or a flight in an airplane is a sleight of hand diversion.