Radiation - FAQ
What is radiation?
The word "radiation" conjures up frightening images of mushroom clouds and Chernobyl, but in reality, it's just a form of energy which we are exposed to every day. Radiation can be produced by technology through nuclear reactions, but it also comes from natural sources, like the sun and the earth. In "normal" amounts, it is generally safe - it's when we are exposed to radiation in unusually high doses - either all at once or over time - that it becomes a problem.
Are there different types of radiation?
Short answer: Yes.
Radiation falls into either of two divisions of the electromagnetic spectrum, depending upon how much energy it generates:
- Non-ionizing radiation - lower frequency radiation like power lines, microwave ovens, radio, TV, infrared heat sources - generally harmless
- Ionizing radiation - higher frequency and higher energy, short wavelengths. Ionizing radiation has the power to break chemical bonds between atoms (i.e. it mutates and destroys things). This is the dangerous kind.
According to the Health Physics Society, there are 5 different types of ionizing radiation:
- Alpha Radiation - these are heavy particles which only travel a short distance and can't penetrate human skin or clothing. They are however, a hazard if inhaled or ingested, or if they come in contact with an open wound.
Radon (a silent health hazard in many homes), Radium (found in the paint used to make "glow-in-the-dark" watch hands in the first half of the 20th century), and Uranium emit alpha radiation.
- Beta Radiation - Lighter particles which can travel through the air for several feet. Beta radiation can only penetrate the top layer of skin and usually can't penetrate clothing. If your skin comes in contact with beta radiation, you should wash it off promptly to avoid injury.
Beta radiation is emitted by strontium-90 (used in medicine and industry, but also found in nuclear fallout) and tritium - a radioactive isotope (form) of hydrogen (produced by nuclear fission and in trace amounts by cosmic rays interacting with our atmosphere.)
- Gamma Radiation and X Radiation (X-rays) - Gamma radiation is a form of electromagnetic radiation which is capable of traveling great distances and penetrating skin. Although used safely in diagnostic medicine, it has the potential to be the most hazardous form. Only very dense substances, like lead, can shield against gamma radiation or x-rays.
Some substances which emit gamma rays include iodine-131 (used in medicine, but also a by product of nuclear fission in power plants or weapons), cesium-137 (found in nuclear reactors and nuclear weapons) and cobalt-60
(used in medicine, industry and in food irradiation.)
- Neutron Radiation - Neutron radiation is better described as "indirect ionizing" radiation. While not radioactive in itself, it is made up of free neutrons, which interact with other atoms in a process called neutron activation to form new radioactive isotopes. In simple terms, it has the power to make most other substances it comes in contact with radioactive.
Neutron radiation can be created by nuclear fission or nuclear fusion and is produced in nuclear power plants, by nuclear explosions, and by some forms of industrial radiography and radioscopy. Due to its unique properties, shielding equipment from the effects of this type of radiation is an ongoing issue in the industry. Effective shielding materials include water, paraffin wax and hydrocarbons.
Where is it found in our daily lives?
Some sources and everyday uses of radiation include:
- Light and heat from the sun
- Cosmic rays (mostly filtered out by our atmosphere). You get more exposure to these near the earth's poles and at higher elevations.
- Minerals in the earth (terrestrial radiation)
- Electromagnetic Field radiation from power lines
- Coal power plant emissions
- Airport security scans
- Accidents during transportation of radioactive materials
- Ionizing Smoke Detectors - this type of smoke detector uses radioactive material to detect particles of smoke. They are perfectly safe as long as they are intact, since the radioactive material is sealed into the unit, but never tamper with an ionizing smoke detector or try to take it apart.
- Phosphogypsum - a by-product of manufacturing phosphorus-based fertilizer
- Mail irradiation - Some mail, particularly government mail, may be irradiated for security purposes. Individuals who handle large amounts of irradiated mail, such as postal workers, follow strict procedures to avoid health hazards. This process does NOT make mail radioactive - radiation doesn't remain on the mail so recipients are not at risk.
- Food irradiation - Some food is irradiated to kill bacteria and inhibit spoilage. Precautions need to be followed to avoid a health hazard to the workers performing the irradiation. Consumers are safe, and this does NOT make your food radioactive. It may make it harder to detect when food has gone bad by eliminating the source of the tell-tale odor.
- Industrial particle accelerators
- Nuclear weapons, power plants and submarines
- Microwave Ovens - Can leak radiation around damaged or broken door seals. Microwaves do NOT make your food radioactive.
- Wireless technology
- Uranium mining
- UV Tanning
- Radiation therapy and nuclear medicine
- Contamination from cleanup sites
- Tobacco - You knew smoking wasn't good for you, did you also know it was a source of harmful radiation? During cultivation, natural radioactive substances adhere to the sticky tobacco leaves and the plant roots absorb radioactive residue from phosphate fertilizers. These remain in the tobacco through processing and are inhaled by the smoker or via second-hand smoke.
- Radioactive materials in drinking water (from minerals in the earth)
- Nuclear fallout from tests and accidents
- Wastes from oil and gas drilling - the highest risk is to workers at the site.
- Industrial gamma rays
- X-rays, CT scans, mammograms, colonography, and other medical diagnostics
- Sterilization of medical equipment
- Radioactive waste
How is radiation measured?
Different units of measure are used to measure radiation, depending upon the context.
A dose of radiation absorbed by a person's body is measured in rads or grays (Gy.) One rad = 100 grays. A centigray (cGy) is 1/100 of a gray.
The biological risk of being exposed to radiation is measured using rems or sieverts (Sv). 1/1000 sievert is a millisievert (mSv).
Learn more - http://www.sievert-system.org/WebMasters/en/mesure.html
How much exposure is considered "safe?"
Being exposed to over 100 mSv of radiation a year increases a person's cancer risk. Being exposed to over 1000 mSv in a year elevates your risk of developing a fatal, radiation-related cancer to 20%.
Under normal circumstances, our annual exposure to harmful radiation is far less. The average person living in the US is exposed to about 6.2 mSv per year, the average worldwide is only 2.8 mSv per year. On average, just 14% of our total annual radiation exposure is from medical tests (like x-rays and CT scans) and only about 0.25% is from nuclear sources. Most of the radiation we are exposed to is "background radiation" - natural radiation from radon, cosmic and external sources.