Yes it is true. When radioactivity was relatively new in the early twentieth century and poorly understood, there were literally hundreds of devices on the market promoting radiation exposure for its beneficial uses in curing just about anything that ails you.
Radon is a colorless and odorless, naturally occurring radioactive gas that is formed by radioactive decay of the element radium. This gas can dissolve in groundwater and volatilize when water is released from a faucet or showerhead. The U.S. Environmental Protection Agency recommends that public water suppliers remove radon from their water if levels exceed 300 picocuries per liter.
The two principal concerns for radon are stomach cancer from ingesting radon and lung cancer from inhalation of radon byproducts. The health risk of radon inhalation is believed to be many times greater than the risk resulting from direct ingestion of radon contained in water. It has been estimated that there is an increased lifetime stomach cancer risk of between 0.25 to 1.0 percent per 100,000 pCi/L in a water supply, although there is no direct evidence of this. Radon in water is emitted into the air, especially where water is agitated or sprayed (shower, washing machine). The EPA has not set a Maximum Contaminant Level (MCL) for radon in drinking water at this time but recommends that any level of radon above 300 pCi/L should be a concern.
In the past, a number of radon devices were designed to use radium to inject its degradation product of radon gas into water, creating what was called radium water or radon water. A popular slogan of the times was, FOR A HEALTHY GLOW, DRINK RADIATION.
In fact, the American Medical Association (AMA) was very concerned about charlatans fleecing the public by marketing devices that did not produce suitable radioactivity. Therefore, the AMA established certification guidelines that were in effect from 1916 through 1929. The crocks and emanators that could not generate water that had more than 2 microcuries of radon per liter within a 24-hour period did not get AMA approval. This radon level is over 6,000 times the level that EPA now considers being safe in drinking water. While we no longer use slogans such as "for a healthy glow, drink radiation," the water drinking community is setting recognizable standards for the once-popular radon.