Radon emission is part of the decay chains of Uranium and Thorium. It is produced in extremely small quantities, and usually only from older structures using rock foundations other that concrete. Personally, I think it was a media scare brought about by the makers of Radon removal systems. My house has one, but it was put in by the whacko who lived here before me. He was also afraid of microwave ovens.
Gluten sensitivity is a real thing. Coeliac or hypothyroidism, both can be impacted by gluten. If you don't suffer from either of those conditions, then it shouldn't bother you.
Basements are not common in California, but a lot of new "McMansions" around here are built with a basement floor that serves as a wine cellar, exercise room, and home theater. Even then I hear almost nothing about radon.
You get more radiation from eating a banana (K-40) or living near a highway (C-14) than from atmospheric radon.
This post was edited by Slartibartfast at November 26, 2017 3:48 PM MST
It was a big thing in the UK too. I think what happened was that many people thought it a country-wide problem when in fact it is confined to particular areas. One this was realised, people stopped panicking.
It did make some show-cave owners install ventilation-fans in their property in areas where the limestone is heavily-mineralised: the visitors are NOT at any real risk, but the guides may be as they work in the cave for some hours a day, most days of the week.
The most worrying areas in the UK are, I think, Cornwall and Edinburgh, due to being on granite masses and their associated mineral-rich geological surroundings, and using the rocks extensively as local building-stones. (Though I'm not sure if the granite itself is actually a problem.)
Perhaps the level of IQ in popular scares was neatly shown by my local paper, the Dorset Echo, at the time. Either it or some dim local councillor they might have interviewed - I forget exactly - reckoned without the slightest evidence or attempt to verify it, that radon would be a problem on the "Isle" of Portland due to its "granite"..... There is no granite anywhere around what is actually the type area for a limestone better known as "Portland Stone" (of Cenotaph and St. Paul's Cathedral fame, and even marking the Mason-Dixon Line); and I happen to know a small-scale study detected negligible levels of the gas. Local newspapers are not normally given to sensationalism, but if this level of lazy reporting is typical of journalism generally, it's hardly surprising that scares based on technical matters spread so easily.
BTW Radon not "poisonous" as such but radioactive.
Element 99 