Radium dial

Geiger counters could pick up readings from pants returned from a dry cleaner and from clothes stored away in a cedar chest.

"[5] According to the United States Environmental Protection Agency, "radioactive antiques [including watches] are usually not a health risk as long as they are intact and in good condition.

"[6] However, radium is highly radioactive, emitting alpha, beta, and gamma radiation — the effects of which are particularly deleterious if inhaled or ingested since there is no shielding within the body.

Inhaled or ingested particles may deposit a high local dose with a risk of radiation-caused lung or gastrointestinal cancer.

Chronic exposure to high levels of radium can result in an increased incidence of bone, liver, or breast cancer.

[8] A 2018 study by researchers from the University of Northampton found that a collection of 30 vintage military watches with radium dials kept in a small, unventilated room produced a radon concentration 134 times greater than the UK's recommended "safe" level.

It was only with the passage of the Energy Policy Act of 2005 that the United States Nuclear Regulatory Commission (NRC) was given oversight of the use of radium.

A 1950s radium clock, exposed to ultraviolet light to increase luminescence
November 1917 ad for an Ingersoll "Radiolite" watch, one of the first watches mass marketed in the USA featuring a radium-illuminated dial.
Wristwatch produced for the US Army during World War II showing characteristic sandy deterioration of radium–zinc sulfide painted hands and numbers. Such a watch should not be opened due to the danger of inhalation of airborne particles.
Three radium dials and a radon detector are placed in a sealed plastic container. After 6 hours, the radon level was 446 pCi/L.
Radium was initially touted as a positively salutary substance, as this January 1922 ad from the Buffalo Times illustrates.