alpha particles (think doubly ionized helium atoms) do carry a fair amount of energy but in general unless they are inhaled or ingested they are not a concern. they won't penetrate a piece of paper. now if you ingest or have trapped in your lungs etc a particle that as it decays emits alpha, that would suck, however, alpha emitters are not likely to be throughout environment. yeah gamma particles have high energy and pass through the body very little you can do to shield and this represents most of the radiation that reactor operators on operating plants are exposed to from a reactor itself. though they pass through the body their high energy rips the hell out of your cells. i was a former nuclear submarine officer and worked in the civilian nuclear industry before getting tired of it and changing careers. i don't think the physics changed when i left.