Exposure to even minuscule amounts of radiation is enough to spark deep, gut fear in most people in the modern world. Our fear of radiation is not
unfounded. In the wrong doses, it does heinous things to people. We have seen this in the bombing of Hiroshima and Nagasaki, in various nuclear
accidents, in the Chernobyl disaster, and in the effects on the natives of Rongelap and their descendants.
This has been embedded in our subconscious over the last century, and for good reason... It makes us take precautions which typically allow us to play
with god's building blocks and not fatally irradiate ourselves. That instinct is also a contributing factor to our lack of a nuclear holocaust,
despite having the required number of weapons and vicious primate urges to create one. However, as evidenced in the previous days with the Fukushima
nuclear accident, sometimes the worst does happen, and all of our well engineered precautions fail.
After that point, most people are still in the dark about what radiation is, how it damages tissue, and how to avoid or mitigate exposure.
To quote the dictionary, radiation in the broadest sense is "the process in which energy is emitted as particles or waves." That's pretty simple.
Turn on a lightbulb to witness a form of radiation, if you'd like.
Further, radiation comes in two flavors: ionizing, and non-ionizing. Ionizing radiation is radiation which is powerful enough to rip electrons off of
atoms. This is the bad and dangerous kind of radiation, and it can destroy body tissues on a microscopic level. When most people say radiation, this
is the kind they're talking about. For the rest of this post, you can assume that I'm of the same mind.
Non-ionizing radiation is typically less dangerous. I say typically, because major contenders in the non-ionizing radiation class are sunlight and
radio waves, both of which are (mostly) our friends. It will not be dealt with here.
Ionization occurs when radiation rips off an electron from an atom.
Ionizing radiation comes in several further flavors. The ones of concern in the context of this post are alpha, beta, gamma, and neutron radiation.
Alpha and beta radiation are similar in that they are a byproduct of radioactive decay in which high energy, short-ranged (milimeters or less)
particles are emitted. Alpha decay releases alpha particles, which are identical to helium nuclei. Beta decay releases electrons and certain
antimatter particles. Alpha radiation is less dangerous than beta radiation, as an external source does not penetrate the skin. An external source of
beta radiation can cause burns if it makes contact with skin. Both can be harmful or fatal if the sources of radiation are in some way ingested, as
the radioactive material can become concentrated in the tissues of vital organs.
Gamma radiation is different from Alpha and beta radiation in that it is not a particle per se, but a wave frequency in the electromagnetic spectrum,
similar to x-rays. In nuclear bombings and accidents, gamma radiation is released after radioactive materials have undergone alpha or beta decay. High
energy gamma radiation is more penetrating than alpha and beta radiation, which means that the whole body and its tissues can be irradiated by an
High energy neutrons can make other matter into sources of radiation via a process called neutron activation, which can turn otherwise
well-intentioned matter into unstable, radioactive matter. They also have the ability to ionize atoms. Neutron radiation is more penetrating than
alpha and beta radiation. It is sometimes more penetrating than gamma radiation as well.
How Radiation Harms
Radiation does damage to tissue by ionizing some of the atoms in the tissue cells' molecular structures. It is kind of like the cell is being shot up
with an atomic machine gun with radiation bullets. As the energetic particles and rays bombard a cell, bonds in the cell's molecular structures are
ripped apart and the molecules come unglued; molecule mangling free radicals can also be produced by ionization of water molecules in cells with the
Many structures in the cell can be repaired, even if damaged by radiation. However, some damage done to the cell's vital structures (including DNA)
cannot be repaired or there is too much damage, and this is where the problems start.
When damage occurs to a part of the cell, the cell either repairs the damage to the best of its ability, or it dies. If the cell survives to divide
again, incorrectly repaired DNA can lead to cancers and abnormal tissue growths in the irradiated organism, or deformities in the organism's
offspring. Most of the time, the cell can successfully repair radiation damage without mutations. This is the common effect of low occupational and
Due to a process called apoptosis, highly damaged cells essentially self-destruct. Apoptosis is activated by damage to DNA and certain other cellular
structures. This is of particular concern in tissues which require rapid cell division and production to maintain functionality, such as the bone
marrow. This is the type of cell damage that leads to acute radiation sickness and often death after exposure to high doses of radiation. On the other
side of the coin, it is this very process by which many cancers are destroyed using radiation therapy.
Modes of Exposure, Measurements, and Harmful Levels
Radiation exposure can occur from an external source, such as unshielded nuclear fuel or the radioactive isotipes found in fallout. External sources
become internal sources of radiation if the unshielded source is somehow ingested. Internal exposure to radiation is more dangerous than external
Radiation is measured in a few different ways, each measure quantifying a different attribute of the radiation. The grays & rads and sieverts and rems
are of primary focus in this post, as they are the measurements used when referring to how much radiation a person is getting.
Grays and rads measure the amount of energy absorbed by matter from radiation (absorbed dose). Sieverts and rems quantify the amount of damage done by
the absorbed dose of different types of radiation (equivalent dose).
1 gray of radiation is equivalent to 100 rads. 1 sievert is equivalent to 100 rems.
The sievert is arrived at by multiplying the absorbed dose in grays by two different weighting factors. The first is the weighting factor that deals
with the type of radiation. The other is the weighting factor that deals with the part of the body exposed to radiation.
weighting factors for converting grays to sieverts
Rem stands for roentgen equivalent in man. The rem is arrived at by multiplying the absorbed dose in rads by one weighting factor which deals with the
type of radiation.
weighting factors for converting rads to rems
The following outlines various doses of radiation and their effects on a person if the person recieves a full body dose: