I have to admit that I am fairly skeptical of today's niceties of environmental radiation (e.g. in tobacco). As a boy of about 10, living in Atlanta, I clearly recall watching a somewhat boring, stammering, academic discussion--in black and white--on our new (and only) UHF TV station of how strontium-90 from recent atmospheric testing of thermonuclear bombs over the Pacific Ocean was settling onto the landscape of the United States, and entering our food chain. But that was not long after the time when I could stick my feet into holes in a funny-shaped box at any shoe store, and see the bones of my feet via X-ray.
There is no doubt that cumulative radiation dose can be a biological problem. There is also no doubt that external vs internal exposure to various kinds of radiation are quite different. The radiation from alpha and beta particles is pretty much stopped by your skin and clothing--unless you inhale or ingest it. (Alpha and beta particles that are ingested, mostly end up in your sewer. But when you inhale them, angry cells lining the alveoli
entomb the particles--forever.) Gamma radiation zaps right on through your skin and clothes. And metal radiation barriers generate their own kind of secondary radiation.
What is the moral of all this? There are certainly risks of serious radiation exposure in certain industries, many medical imaging procedures, and low-ish probability events, such as nuclear weapon use. (Oh, and traveling to Mars.) But for the most part, everyday exposures to common environmental items and consumer goods represent a risk that is orders of magnitude smaller. And don't forget that "sun screen" is specifically a radiation barrier against that giant, thermonuclear ball in the sky.
“The end of man is knowledge, but there is one thing he can't know. He can't know whether knowledge will save him or kill him. He will be killed, all right, but he can't know whether he is killed because of the knowledge which he has got or because of the knowledge which he hasn't got and which if he had it, would save him.”
Bob