Ionizing radiation has to do with the strength/volume/force of the energy, being sufficient enough to ionize an atom. The ionization of an atom is essentially the process of knocking an electron off the atom, generally resulting in a charged or reactive atom or molecule with unpaired electron(s) Low levels (often termed background) of radiation are inevitable and all humans on the planet are susceptible.
Our bodies are designed to repair the the damage quite easily. At higher levels, the damage, like that to DNA, is both vast and more difficult for the body to address. The body tries to eliminate potential genetic damage by initiating a process called apoptosis (programmed cell death). This basically kills off the abnormal cells before they spread. If this process is dysfunctional or too slow to handle the amount of damage to cells, mutations will continue to take place in all subsequent cell divisions. This can contribute to the formation of cancer.
Examples of use of ionizing radiation include x-ray machines, power stations and nuclear reactors. Radioactive iodine, strontium, platonium and cesium are all radioisotopes released during a radiologic or nuclear event. Substances in rocks and soil naturally give off a small amount of ionizing radiation, as does the environment outside of our solar system, otherwise known as cosmic radiation. Cosmic radiation far exceeds what we have the capacity to create ourselves. Airline flight crews are thought to receive a higher dose of radiation, on average, than individuals working in nuclear power plants due to cosmic radiation. Radon 222, a major contributor to "background radiation", is a colourless, odourless gas found in soil, water and air. It seeps from uranium containing soils, present in all areas of the world. High levels of radon exposure are associated with increased incidence of lung cancer.
X-ray machines are said to deliver 10 days worth of background radiation in one shot. In terms of sieverts (a measure that quantifies the amount of radiation absorbed by human tissues), an X-ray gives off 400-600 microsieverts, while a whole body CT scan is equal to 15-20 millisieverts, significantly more. That's roughly the same amount that nuclear industry employees and uranium miners are advised to limit their exposure to in the course of one year! Flying creates 3-9 microsieverts per hour. Over a one year period, natural sources of radiation, including radon from soil and radiation from the sun, totals approx. 1-5 millisieverts, depending on location. Radiation sickness, a life threatening illness characterized by nausea, fatigue, diarrhea, hair loss and destruction of white blood cells, occurs at levels of 1-2 sieverts in a one time dose. There is very little information or research dedicated to the overall health effects of long-term, low dose (or background levels) of radiation and its potential to accumulate in the body. 100 millisieverts/year is said to be the lowest at which increased incidence of cancer is clearly evident.
Non-ionizing radiation involves changing the position of atoms within a molecule, but not altering the structure, composition, and properties of the atom. Because the atoms are not altered, non-ionizing radiation is thought to be less dangerous. TV and radio waves, ultraviolet and infrared waves, cell phone, microwaves, electric blankets and visible light are all examples of non-ionizing radiation. Ultraviolet and visible light from the sun do cause physical damage, to both the skin and eyes. Some argue that the well-researched and damaging effects of the sun, being a form of non-ionizing radiation, bring to light questions about the damaging effects of other "safe" forms of radiation, like those given off during microwave and cell phone use. There are limits put on the amount of non-ionizing radiation that common household appliances like microwaves and cell phones can emit. Amounts well below the 'safety limits' have been shown to have damaging effects on genetic material. MRI devices, radar and satellite stations, as well as cell phone towers produce exponentially more than our in home devices and may be doing more long-term damage than we realize.
Food has been shown to have significantly decreased, if any, nutritional value when heated in a microwave. Some studies have shown food to posses carcinogenic property from radiation through microwave cooking methods. Individuals with a history of high cell phone use have been found in some studies to have a slightly increased incidence of glioma (a type of brain cancer). There has also been some evidence to suggest that long-term cell phone use is associated with acoustic neuroma, as well as tumour development on the same side of the head as phone use. More research needs to be done before any evidence based conclusions can be made. That being said, there are simple ways to decrease exposure to both ionizing and non-ionizing radiation. Using a convection oven as an alternative to microwaving, wearing a head set or hands free device when talking on a cell phone, driving instead of flying, when possible, and avoiding excess imaging, such as X-rays, CT and MRI, may all help to significantly lower exposure.
When radioactive iodine is present in the body, the thyroid gland will begin to rapidly absorb it/take it up. Accumulation of radioactive iodine has been directly linked to increased incidence of thyroid cancer, especially in younger populations. Potassium iodide competes with radioactive iodine at receptor sites. It fills these sites and prevents the thyroid from taking up any of the radioactive substance. Its action at these receptor sites lasts 24 hours, meaning the thyroid is unable to take up any more iodine â€“ stable or radioactive â€“ during that time. It is important to understand that potassium iodide does not protect the body as a whole from radioactive iodine, nor does it prevent any other body part from taking it up. It's actions are very specific to the thyroid. It has no effect on other radioactive elements, like cesium, nor the effects these elements may have on the body.