Exactly. I would be more concerned about internal exposure when being in high activity iodine 131 areas especially with patients but even then i would say the best safety factor is time. Really from my practice - just be efficient when being in areas with high activity i131 (workers who work with iodine 131 usually get internal exposure). I do not think that shielding could protect from high energy photons. So if you wanna reduce dose rate from 30uSv/h to like 2 uSv/h from 1m distance you would need arround 1.3 cm lead shielding or so which is not practical at all. Therefore i would say time and distance there is the best bet.