Mainstream news stories almost always confuse the very different terms Radiation (like x-rays) and Radioactive (physical materials; fallout), which are significantly distinct things.
- Radiation means visible light and all of its invisible cousins: electromagnetic waves including X-rays, gamma rays and radio waves. Radiation can also informally mean the physical things (Alpha and Beta particles and Neutrons) emitted from radioactive materials which are described next.
- Radio-active means those physical materials which emit particles that cause ionizing radiation, or they emit ionizing radiation itself.
Radiation (which is emitted From radioactive materials)
- only affects things locally, very locally. While —
Radioactive material (“fallout” in form of dust, water and air)
- can spread through the air, rivers and oceans emitting ionizing radiation all the way around the world.
Here are examples of correct and incorrect usage of the two terms:
- -The International Atomic Energy Agency
- -PBS News Hour, April 11, 2011, physicist, James Acton, of Carnegie Endowment for International Peace
While perhaps technically arguable as good enough for the general public, this second example is misleading.
The public is seriously concerned about release and spread of radioactive material as dust, in our air and water and soils. It is my experience they are not as concerned about releases of radiation from radioactive materials which only have a local effect.
Radioactive contamination occurs when physical materials emit radioactive materials or gamma rays. Those emitted particles are Helium4 (Alpha), Electrons (Beta), or Neutrons. All can cause ionization in other materials. What is key is that a solid piece of radioactive material does not spread or transfer contamination. Its only when the radioactive piece is turned into dust that it contaminates air, water and soils.
That’s not entirely true because some radioactive materials can transfer radioactivity called Neutron activiation by emitting Neutrons. Practically though, because those materials are common only during fission (in a nuclear reactor while it is operating (or melting down) and at the moment an atomic bomb explodes) these dangerous materials are only extremely rarely released or spilled.
There are many radioactive materials. You really don’t want to breathe or ingest any of them; some you never even want to get close to.
Mrs. Marie Curie was awarded TWO Nobel prizes for her work discovering and developing fundamental understanding of radioactive materials.
Yet Marie Curie died due to ignorance of the harm of those radioactive materials. This makes me seriously skeptical about people putting radioactive materials in our bodies with essentially no physics training, that means radiologic doctors and technicians.
While some materials like Plutonium and Cesium continue emitting radioactivity for tens of thousands of years, the radioactivity of other materials dissipates to trivial (background levels) in only a few weeks (e.g. most Iodines). Some materials’ radioactivity (some Plutonium isotopes) vanishes in less than a second.
This means it is critical to know which specific radioactive materials you are dealing with. Fukoshima has leaked Iodine 131 (half life = 8 days) and Cesium 137 (half-life = 30 years).
Because the Iodine dissipates relatively quickly, the the long lasting Cesium is the dangerous material to keep your eyes on. Cesium emits gamma rays – which damage, and even sort of melt, your DNA.
In Japan 2011, some 25,000 people are known dead from the 9.0 earthquake’s tsunami, but so far no one is yet known to have died from the nuclear plant’s radioactivity. (Curiously, I have not yet read a report of anyone dying directly from the earthquake.)
For more information please see “Understanding Radioactivity Harm Thresholds (in plain English)”
Ionizing radiation directly harms your DNA, enough of it will kill you. Lesser amounts can do serious damage.
Ionizing Radiation comes from X-rays, gamma rays and ultraviolet light. It is important because it changes the nature of atoms and molecules by knocking at least one electron out. This gives the atom an electrical charge, and results in a free electron flying around.
Ionizing Radiation does not comes from radio waves, microwaves or visible light because their photons are not strong enough. Their photons are called non-ionizing radiation. (While powerful radio waves can kill you too (think microwave oven), this section is only about Ionizing Radiation.)
The threshold is 318 nanometer wavelength – the energy where Cesium can ionize. (Visible light, Violet, begins with much less energetic photons at about 380 nanometers and extends to Red at about 740 nm.)