Ignorance Has a Long Half-life
Dental X-rays constitute most Americans’ experience with radiation. With every report from the Japan nuclear power plant, we remember the dental technician draping us with a lead apron and then leaving the room while their machine mysteriously zaps our jaws. It is all the more scary because we don’t hear or see the "radiation"—just the resulting photo of our teeth.
Meanwhile, those who do understand radioactive materials—science teachers, corporate and military safety officers, etc.—fortunately have spouses who are shielding the television from our wrath. My science colleagues correctly describe most media reports as "clueless," "sensationalized," " ignorant," or "nonsense."
Most Japanese citizens remain calm but Westerners line up at airports to leave in a panic. Media attribute this to a Japanese attitude of accepting fate. But some of it is their deeper knowledge from better science education. What do many Japanese understand about radiation that most Americans do not?
"Radioactive particle" is not the same as "radiation." The press is using these interchangeably but the difference is very important.
Radiation is energy in particle or wave form.
"Non-ionizing radiation" includes everyday visible light, radiant heat, radio waves, U-V light, etc.
"Ionizing radiation" has enough energy to remove electrons from atoms, forming ions. Large amounts of ionizing radiation can alter DNA and kill cells.
Nuclear power plants produce unstable atoms (radioisotopes) with extra neutrons. Unstable isotopes of uranium, radium, radon, and thorium are found in nature. Other radioisotopes are made in nature and in nuclear reactors. As these radioisotopes decay to stable elements, they emit ionizing radiation.
There are three forms of ionizing radiation. Understanding them is important.
"Alpha particles" are the largest emitted from the nucleus of an atom. They collide immediately with surrounding atoms and lose their energy. A sheet of paper easily stops them. In air, they only travel a few centimeters. Only if we eat, drink, or breathe in radioactive material that emits alpha particles—and then concentrate them in the body—do they pose a health hazard.
"Beta particles" are smaller. They are less likely to collide with atoms, so they can travel farther than alpha particles. But a thin sheet of metal or a few centimeters of wood or plastic stops them. Beta particles can be a health hazard if highly concentrated on skin, or when ingested or inhaled if they are concentrated in tissues. Iodine-131 is a beta emitter and we can concentrate it in our thyroid.
Alpha and beta emitters give off their radiation over time. An alpha or beta source is not going to be harmful to living tissue at a distance because neither travels with high energy over long distances. When we see images of Japanese health workers scanning people’s coats and telling them to wash the dust off, this washing carries the alpha and beta emitters into the soil and water where the radiation they will give off is shielded.
Gamma radiation is the radiation in the minds of most people due to our experience with medical and dental x-rays. It is pure energy with no mass or charge, and requires shielding by lead or concrete. So far, this is mainly a concern to the nuclear workers inside the power plant and storage areas.
A final factor is "half-life," the time it takes a radioisotope to decay half way toward its stable form. Of the three radioisotopes produced, Iodine-131 is the most common and has a half life of just over 8 days. That means half of the radiation will be emitted in 8-days, half of what remains (or one-fourth of the original) in 16 days, and so on. Strontium-90 and Caesium-137 are produced in much smaller amounts and have half-lives of under 29 years and over 30 years. Strontium is a beta emitter. Caesium emits both beta and gamma radiation upon decay.
So alert your spouse to protect the TV! You now know enough to throw objects at your television set as they continue to misreport the news.