spaceSpace and Physics

Your Cherished Family Heirloom Could Be Slowly Killing You

A collection of radium painted clocks. Photo credit the United States Environmental Protection Agency.

Researchers from the University of Northampton and Kingston University have discovered that the glow-in-the-dark wristwatches that were popular in the first half of the 20th century – and widely given out to British and American servicemen – emit an extremely carcinogenic radioactive gas at concentrations up to 12 times higher than the maximum safe level.

The startling revelation about radium dial watches came from an analysis of 30 specimens by Dr Robin Crockett and professor Gavin Gillmore as part of an international report about radon exposure.


The two note that although it has been known for some time that the radium in these timepieces continually decays into radon, very few studies have quantified it.

“These results show that the radon emitted from individual watches can potentially pose a serious cancer risk,” Dr Crockett said in a statement, alluding to the established link between radon and lung cancer. “This is of concern because in addition to military watches being particularly prized by collectors, many individual radium-dial watches are kept as mementos by ex-servicemen and their descendants.”

Radon is a colorless and odorless gas continually present in the environment due to the decay of naturally occurring uranium and thorium ore into radium, which in turn – with a half-life of 1,600 years – undergoes alpha decay into radon, producing ionizing radiation in the process. Because such ores are more abundant in certain regions and get transported during industrial processes, public health organizations recommend that homes and buildings should have their radon levels periodically tested.

Using radiation detectors, Crockett and Gillmore determined that the radon emitted by the entire collection of watches produced approximately 13,400 becquerels per meter cubed (Bq/m3) of radiation when placed in a space of similar size as a storage room or small bedroom. Public Health England recommends that indoor spaces should aim for no more than 100 Bq/m3.


The three watches that were in the worst physical condition, and thus had the least shielding around the radium paint, emitted between 200 and 1,200 Bq/m3 each.

Crockett and Gillmore stress that the proper handling and storage of these watches is critical in order to protect one’s health. The scientists estimate that millions of radium dial watches remain in circulation in antique shops or sitting in family jewelry boxes and private collections, despite their sordid history.

These luminous watches were made infamous in the 1940s by the plight of the “Radium Girls” – the groups of working women who hand painted the glowing dials at American watch factories beginning before WWI and continuing up until the outbreak of WWII.  

Believing the radium was not only safe but actually beneficial to their health (at the time it was seen as a miraculous cure-all and added to beauty products and food), the women would wet and shape the brush tips with their mouths and lips in between dips into the radium paint. They quickly began to develop a host of horrifying health problems; the first and most common was rapid tooth loss accompanied by chronic, unhealable gum ulcers. In many cases, the jawbone eventually crumbled away, and a large number died young from internal hemorrhaging.


All in all, it might be time to downgrade these objects from beloved family heirloom to carefully disposed of waste.

The radium girls hard at work painting watch faces at an American company. Wikimedia Commons


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