Is granite countertops still found to be radioactive or are they doing things differently now to prevent that issue (or perhaps they are tested before they are installed?) My parents are having a house built and are getting granite counter tops so now you have me worried.
Nothing changed at all. A few importers bought radiation survey equipment and started weeding out the worst slabs. But it remains legal to import, fabricate, sell, and install extremely radioactive materials as countertops because it is a "natural" product.
During all of this interest and testing I sent an email to the NRC asking if it was legal to fabricate a product that was around ten to twelve times background radiation levels. Gave them a video of the meter readings. The response back was no, it was a federal crime to work such material outside a properly designed facilty that was monitored by a qualified expert in measuring radiation and protecting employees. I sent back the pictures of the source, a granite slab for sale at a slab yard here in OKC and was told of the natural product exception.
The radon industry is an unwanted step child of the U.S. radiation community. They are tolerated and sanctioned by the larger radiation community but just barely so and only because they can keep the radon folks muzzled and under control. Why? Because groups like the Health Physics Society are mostly funded and mostly employed by the nuclear power companies or nuclear medicine. So if you make people afraid of extra radiation you cut into their profits.
Bottom line is this. When a site is cleaned up it has to be over 25 mrem (4 to 10 mrem is average background in most places) and it needs to be cleaned to below 25mrem. Yet we found granite slabs that averaged over 50 mrem, usually one quarter to one third of the slabs in a slab yard, and it was not uncommon to find 500 and even 1000 mrem hot spots in slabs.
China and Europe have limits on radiation levels of building material, the U.S. doesn't. When we tried fixing that the stone industry spent over a million dollars a year fighting back and they even attacked the scientists that were helping pro bono, getting a few of them de certified. The reason was not that these experts were wrong, the reason was they advanced an opinion before the testing was 100% completed and thus could have been wrong. The final studies were presented at the national conventions of the Health Physics Society and at several conventions for the Radon industry. All the experts read, listened, and commented "Huh, we got a problem." and nothing was done.
I would purchase a good radiation meter before purchasing any granite. You need a low level device, not the standard geiger counter. Find one for testing food or water as they are more sensitive or one of the belt loop pager looking devices used to protect x ray techs. You can also get fairly cheap Russian models or find a used PM1703. Those things can spot a nuclear patient (radioisotopes used for screening) passing you in a car on a freeway. Most of the units on
Amazon are set to go off too high, 100 mrem, find one that measures down to at least 10 mrem.
https://www.amazon.com/dp/B004SZ2HXQ/?tag=backy-20
Here is a better one but it reads in mcSv/hr so you will need to either use that standard or do the math to mrems.
https://www.amazon.com/dp/B07PMNKX6M/?tag=backy-20
There is radiation everywhere but there is no reason to bring more into your home. ALARA, As Low As Reasonably Achievable is the standard.