|Ray Don is Fleischers crash test dummy for radons effect on eyeglass lenses.|
Ever wondered what to do with those old eyeglasses? They may turn out to be useful for measuring radon exposure.
Researchers at Union College in Schenectady, NY, are using plastic eyeglass lenses as personal radon monitors to measure how much radon people are exposed to wherever they go.
How does it work?
Plastic eyeglass lenses are normally made of a material called allyl-diglycol carbonate, or CR-39. It so happens that CR-39 can detect alpha-particles, which are formed when radon breaks down. "They [alpha particles] make little trails of damage, little needle-like, tiny, narrow trails" in the lenses, explains geologist Robert Fleischer, lead researcher of the Union College study. By chemically treating the lenses, Fleischer and his colleagues were able to reveal the trails and then count them using an ordinary microscope. Counting the trails in the lenses gives a measure (based on how long the wearer has had them) of the number of alpha particles that hit the lenses, and therefore an estimate of the amount of radon gas the wearer was exposed to.
Researchers used the side of the lenses that face the eyes to take measurements because the blanks used to make lenses can accumulate radon tracks while they’re being stored. But when they’re ground for prescription, the inside surface is used, thus removing the radon record and "turning on" the radon-detecting capability.
"The use of eyeglasses as personal monitors, I think, is very useful," says epidemiologist Bill Field, one of the lead researchers of the Iowa Radon Lung Cancer Study (see STN2s "Radon Risk"). "I think Dr. Fleischer’s work is really novel and inventive, and the utility of it is that it gives us another device or another way to measure retrospective exposure."
What is the radon risk?
Although completely natural, radon is a known cause of lung cancer. The Environmental Protection Agency (EPA) estimates that radon exposure is responsible for approximately 15,000 to 22,000 lung cancer deaths each year. Aside from cigarette smoking it is the leading identifiable cause of lung cancer in the United States.
The link between radon and lung cancer was discovered when large numbers of uranium miners began suffering from the disease. Radon is a breakdown product of uranium and is found at high levels in uranium mines. But residential radon exposure can also be dangerous. The Iowa study recently showed that radon found in homes may increase the lifetime risk of getting lung cancer by 50 percent.
A colorless, odorless gas, radon seeps up from the ground. It creeps into homes—typically into basements—through cracks in walls and foundations, places where pipes come in, or sometimes right through porous building materials.
Radon itself isn’t actually whats harmful—its by-products are. As radon decays, it produces radioactive particles that can get stuck to the surfaces of the lungs when they’re inhaled. This damages the cells there, and can eventually lead to cancer.
Why test with eyeglasses?
|image: National Academy of Sciences|
According to Fleischer, using lenses as radon meters makes sense because eyeglasses stay with the wearer throughout the day, and are often nearby during the night. "The EPA has suggested that you measure radon in your basement, and that is only meaningful if you spend a lot of time in your basement," notes Fleischer. But radon exposure can occur anywhere—on the first or second floor of houses, outside, or at work. By using eyeglasses to measure radon’s byproducts, Fleischer hopes to create radon risk profiles for individuals rather than simple household readings.
"Hopefully we can be of some help in that we will, after some experience here, say that the typical person spends 60 percent of their time at home on the first floor and 40 percent on the second floor and we’ll know how to weigh those," he says.
Testing eyeglass lenses—which are destroyed in the process—does have limitations. Not everyone wears glasses, and even if a person does he or she doesnt necessarily wear them all day long. Also, each set of lenses requires separate calibration, adding to the time and cost of the process.
So, while using eyeglasses as personal radon detectors may have some benefit, Field cautions that eyeglass wearers shouldn’t rely on it. "The bottom line is to get your home tested," he said.
Elsewhere on the web:
Research in Belgium on using CR-39 as a personal radon detector
Indoor radon variation
Frequently asked questions about radon
Radon outside the home
Health risks and radon
Questions and answers about radon and cancer from the National Cancer Institute