Not all types of radiation are created equal. This means that depending on its origin, radiation can be fairly benign or incredibly malignant. Many natural sources exist, such as sunlight, rocks, soil and food. There are also plenty of human-derived emitters, such as airport security screeners, medical procedures like X-rays, cell phones and nuclear weapons.
"We're all exposed to radiation on a daily basis," explains Kelly Classic, a radiation physicist at the Mayo Clinic, and public outreach coordinator for the Health Physics Society -- noting that small amounts of radiation can be found in fertilizers, some soils, building materials and even bananas, because of their naturally occurring potassium. "It's something that we live with every day and so rarely question it."
All forms of radiation, whether from sunlight or a computer, operate on the electromagnetic scale -- each with its own, varying frequency, wavelength and energy emitted. Depending on the amount of energy they have, the wavelengths can travel certain distances and penetrate certain objects. Longer wavelengths, like those used in cell phones, garage door transmitters and AM/FM radios, have lower energies and lack the ability to cause changes to atoms. People are exposed to low-intensity radiation throughout each day, giving it the name background radiation exposure. Most people in the U.S. are exposed to about 3 millisieverts (mSv) worth of natural radiation each year, an amount that is presumed harmless [source: Classic]. The mSv is a measure of the amount of radiation absorbed by the human body.
It's when one adds higher intensity radiation to this everyday exposure that health concerns begin. As wavelengths become shorter, their energy intensity continues to increase until it becomes ionizing, or causes changes to the cellular structure of atoms. Ionizing radiation is the most powerful form of radiation is, and it can be used to produce electricity, treat cancer, take X-rays and sterilize medical instruments. Ionizing radiation is more worrisome, especially when unborn babies come into contact with it, since it can have serious health ramifications.