Radiation is present throughout the universe. The decay of atoms is called radioactivity. Radiation is the energy produced by this decay, and the type that is dangerous to us is ionizing radiation. When the electrical ions produced by this decay pass through living tissue, they can influence biological functions [source: IAEA].
Ever since humans first appeared, we've been bombarded by radiation from outer space and exposed to radioactive materials in the Earth itself. Scientists estimate that about 80 percent of the radiation we're exposed to comes from natural sources. While those are by far the most common sources of radiation, they are not the ones that worry most people. We're concerned about the impact of medical scans, X-rays and radiation therapy. These procedures account for about 15 percent of our exposure to radiation [source: HPS]. The remainder comes from lesser sources such as glow-in-the-dark watch faces, microwave ovens, cell phones and even antique glass.
Some of our fears about exposure to radiation are justified. Others can be dismissed. In this article, we'll examine some common sources of radiation and see what we can do to keep ourselves safe.
Nuclear plants and atomic bombs aren't the only sources of radiation. It's all around us, emanating from some common household objects and even the Earth itself.
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10. Wireless Technology
We've all heard the warnings: "Keep that cell phone stuck to your ear, and you'll get cancer." But does it really pose a danger? What about wireless networks in schools, workplaces, your home, even coffee shops? Radio frequency is the energy used in wireless technology. While it can hurt you through heat -- it's the same technology that cooks your burrito in the microwave -- radio waves are non-ionizing radiation.
While wireless computer networks don't seem to be a real threat, some scientists say cell phones may increase your risk of cancer [source: National Cancer Institute]. When you use your phone, you're putting the antenna that generates the radio frequency right next to your head; a study published in February 2011 in the Journal of the American Medical Association said such positioning could alter brain activity [source: New York Times]. The study used a flip phone; smart phones emit even more radiation. Is this dangerous? No one knows, because cell phones have only been in widespread use since the 1990s, not long enough to see long-term effects. Still, researchers advise you to play it safe: Since most radiation is generated while the call is connecting, don't put it to your ear until the connection is made. Use the speaker feature when possible, and wear a wireless earpiece if you can't use a speaker.
9. Tobacco
You know tobacco use can cause cancer, but do you know why? It's not from just from burning tobacco, -- it's from inhaling radiation absorbed by the tobacco plant while it grows in the field. Even if you don't smoke, you're not safe; secondhand smoke carries a toxic dose of these carcinogens, too. Radioactive materials in the atmosphere adhere to sticky tobacco leaves. The materials remain on the plant throughout the manufacturing process. The use of Apatite--a phosphate fertilizer--increases the radiation absorbed by the tobacco plant. The lead-210 and polonium-210 radiation emitted by the tobacco smoke is trapped in the lungs of the people exposed to it. Tar from the smoke also builds up in the lungs and enables them to trap the radiation more efficiently. Over the course of decades of inhaling tobacco smoke, the smoker's lungs are damaged, and the smoker -- and folks exposed to the second-hand smoke -- may develop lung cancer [source: EPA].
On the subject of smoke, next we'll see if something designed to detect a fire could actually do more harm than good.
8. Smoke Detectors
They'll save your life, but some people are convinced that smoke detectors can also hurt you through radiation. Two types of smoke detectors are in common household use: Ionization smoke detectors detect smoke particles through a radionuclide sealed inside them, while photoelectric smoke detectors utilize a light sensor. Ionization detectors are better at detecting flash fires; photoelectric detectors are good for smoldering blazes. Many smoke detectors use a combination of both methods. An ionizing smoke detector does not pose a danger to you as long as you don't take it apart. The detector uses radioactive americium-241 bonded to foil and sealed in a chamber. Americium-241 emits alpha particles and gamma rays. Ionizing smoke detectors work by sounding an alarm when smoke interrupts the flow of alpha particles.
7. Security Scans
Airport security systems have changed dramatically since 9/11. Now two different types of scanners check you and your bags for weapons and other contraband. These machines are not metal detectors -- they 're X-ray machines. If you've flown in the past few years, you're familiar with the routine before entering the boarding area -- take off your shoes, belt, jacket and place any bags on a conveyor belt so they may be run through a cabinet X-ray machine. Thick walls prevent X-rays from penetrating the surrounding area. The government regulates the amount of radiation the machine can emit and requires alarm systems and locks to prevent mishaps. People pass through an X-ray scanner, called the backscatter system, which uses a low amount of radiation.
In October, 2001, envelopes containing anthrax spores passed through the U.S. Postal Service, so the government subsequently ordered the irradiation of all mail to federal offices in the Washington area. This is done by running it through an electron beam or an X-ray. A thick concrete barrier protects postal workers. The result is mail that is not radioactive, but may seem brittle or have an odd smell.
6. Microwaves
Many of us would be lost without microwave ovens, but how do they work? Will we pay for our afternoon bag of popcorn with a deadly disease from radiation exposure? Microwaves use radio frequency waves to vibrate the molecules of the food and generate heat. The energy is not radioactive and does not alter the food. The danger from microwave radiation comes if the door does not completely seal. Microwaves will heat your body just like they warm that cup of coffee, so standing near a microwave with a faulty door seal can be dangerous. Repeated slamming or simple deterioration due to age can damage door seals. You cannot see or smell radiation leakage, so the Food and Drug Administration advises you to be cautious. Don't stand in front of or lean on the oven while it is in use.
5. Power Lines
After several decades of research, scientists still don't know a whole lot about the dangers of the electric and magnetic fields produced by high-voltage power lines. The electric charges produce electric fields and the flow of current through the wires produces magnetic fields. In the 1990s, many families and farmers who lived or who had animals near or underneath large power lines came forward to say they believed the electric and magnetic fields had negative effects on their health. The National Institute of Health conducted a study of incidences of childhood leukemia in 1998 and determined that living near power lines was a possible cause, but had no conclusive results [source: EPA].
While power lines emit their fields in the sky, another danger is lurking underground. Keep reading to find out about radon, a radioactive threat to your health that comes from underneath your home.
Radiation from high-voltage power lines has been accused of being a health hazard, but the evidence is inconclusive.
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4. Radon
Radon is a radioactive gas generated by the decay of uranium in rock and soil. As the uranium decays, the radon it produces can seep into buildings, accumulate and become a health hazard. More than half of our exposure to radiation comes from radon, and only smoking tobacco causes more cases of lung cancer. The EPA estimates that about one in 15 homes has elevated radon levels [source: EPA]. Professionals can come to your home and test the air, then advise you as to what kind of action to take. You can also buy a kit and test yourself. The most common way to eliminate radon seeping into a home is by installing an activated soil depressurization system, which is a pipe with a fan that vents radon from underneath the house. The professional will also seal all entry points to prevent radon from entering your home.
3. Medical/Dental Exposure
Over the page few decades, doctors have employed an alphabet soup of scans --MRI, CT and PET scans, among others --to detect abnormalities. They use small amounts of radioactive isotopes in nuclear medicine to check for abnormalities in organ systems. All of this is in addition to the old standby, X-rays. While none of these tests have enough radioactivity to pose a threat on their own, many people are worried about the cumulative exposure over a lifetime of medical care. Some experts advise patients to make sure they wear a lead shield over their chests and necks when taking dental X-rays. They also might want to ask their doctor and dentist if regular scans and X-rays are truly necessary, and if the period of time between them could be lengthened.
More serious are treatments for disease. Therapeutic radiation treatments for cancer are different from low-dose diagnostic treatments and may cause permanent harm, but that is minor compared to what will happen if the cancer is not treated. Patients dosed with internal radiotherapy are radioactive for a time and must stay away from other people.
2. Cosmic Radiation
Like characters in a science fiction movie, we are constantly bombarded by cosmic radiation. About 8 percent of our annual dosage of radiation comes from outer space [source: EPA]. Subatomic particles from the sun, our galaxy and even galaxies far away mingle with the Earth's atmosphere to create radiation. Most of this cosmic radiation is low energy, but some high-energy radiation does get through. This radiation interacts with our bodies, but it is at such low doses that it does not harm.
The atmosphere protects us from most cosmic radiation, but the higher the altitude, the more radiation you are exposed to. If you live in Denver, you are getting a bit more cosmic radiation than someone who lives in Orlando, but the difference is miniscule. The same principle applies to airplane flights. By getting closer to outer space in a plane, you are increasing your cosmic radiation exposure. The amount of radiation you absorb on a cross-country flight is only about half the amount you'd get from a chest X-ray.
Almost a tenth of our annual dose of radiation arrives from space, whether from our sun or stars in distant galaxies.
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1. Earth Itself
Radiation is not some new creation that industrialized humans invented over the last century. It's always been with us and even in us. In fact, the Earth itself generates much of the radiation we're exposed to. All sorts of radioactive material occur in the soil beneath our feet. These natural sources of radiation can leave the soil, and we inhale the particles. Our muscles, organs and bones are radioactive to some degree. Humans also take in this soil-borne radiation by eating crops grown in the Earth and drinking water from underground wells.
For more on everyday radiation, peruse the links on the following page.
Canadian Centre for Occupational Health and Safety. "Microwave Ovens and Their Hazards." (Accessed April 3, 2011) http://www.ccohs.ca/oshanswers/phys_agents/microwave_ovens.html
Health Physics Society. " Where can you find radiation in everyday life?" (Accessed April 3, 2011) http://www.hps.org/publicinformation/ate/q824.html
International Atomic Energy Agency. " Radiation in Everyday Life." (Accessed April 2, 2011) http://www.iaea.org/Publications/Factsheets/English/radlife.html
Murphy , Kate. "Cellphone Radiation May Alter Your Brain. Let’s Talk." The New York Times. (Accessed April 3, 2011) http://www.nytimes.com, 2011/03/31/technology/personaltech/31basics.html?_r=2&smid=fb-nytimes&WT.mc_id=TE-SM-E-TW-SM-LIN-CRM-033111-NYT-NA&WT.mc_ev=click
National Cancer Institute. "Cell Phones and Cancer Risk." 5/19/2010. (Accessed April 2, 2011) http://www.cancer.gov/cancertopics/factsheet/Risk/cellphones
United States Environmental Protection Agency. "A Citizen's Guide to Radon." (Accessed April 02, 2011) http://www.epa.gov/radon/pubs/citguide.html
United States Environmental Protection Agency. "Electric and Magnetic Fields (EMF) Radiation from Power Lines." (Accessed April 02, 2011) http://www.epa.gov/radtown/power-lines.html
United States Environmental Protection Agency. "Mail Irradiation." (Accessed April 02, 2011) http://www.epa.gov/radtown/mail-irradiation.html
United States Environmental Protection Agency. "Microwave Ovens." (Accessed April 02, 2011) http://www.epa.gov/radtown/power-lines.html
United States Environmental Protection Agency. "Radioactive Materials in Antiques." (Accessed April 02, 2011) http://www.epa.gov/radtown/antiques.html
United States Environmental Protection Agency. "Radon in Homes and Buildings." (Accessed April 02, 2011) http://www.epa.gov/radtown/home-radon.html
United States Environmental Protection Agency. "Smoke Detectors." (Accessed April 02, 2011) http://www.epa.gov/radtown/smoke-detector.html
United States Environmental Protection Agency. "Wireless Technology." (Accessed April 02, 2011) http://www.epa.gov/radtown/power-lines.html
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