Acute Radiation Syndrome, more commonly known as radiation sickness, is one of the scarier threats out there, since it’s born of a force we can neither see nor readily detect and its symptoms can be varied and hard to identify. It can range in severity from an upset stomach to a long, painful death, and it often attacks people literally from the inside out. It seems like an almost spooky threat, but there is some very simple science radiation sickness. Essentially, it comes down to the type of radiation that can alter the electrical structure of atoms in the body.
We call such radiation “ionizing radiation” because it carries enough kinetic energy to knock an electron off of an atom it hits, giving that atom a non-standard number of electrons, turning it into an ion. It generally takes quite a bit of energy to achieve this, and ionizing radiation is almost exclusively the result of large and violent events (both manmade and cosmic). A nuclear reactor produces ionizing radiation that must be filtered out with shielding around the core which can — in the event of a disaster — contaminate whole communities, like Chernobyl (pictured above). The sun itself would shower the Earth with far too much ionizing radiation for life, were it not for our light-scattering upper atmosphere. Still, some forms of radiation get through, like ultra-violet radiation from the sun, or the super-powerful gamma radiation from supernovae and other stellar events.
When ionizing radiation creates an ion in the body, it releases a small but significant amount of heat, and the atom itself can, depending on its identity and environment, go on to steal or donate electrons to surrounding atoms in an effort to neutralize itself. This latter effect is not unlike the mechanism of free radical damage. Regardless, both forms of damage are caused by newly ionized atoms and molecules, and in large enough doses can wreak havoc on the body.
Certain organs and tissue types are more vulnerable to these kinds of damage. With a large enough dose of radiation, for instance, bone marrow will break down almost completely causing major problems with anemia and maintenance of the blood. When the damage occurs in a skin cell, either randomly or because the radiation is too weak to penetrate through the skin, this can result in radiation burns and other surface deformities.
Our bodies evolved for this environment, though, and can deal with it well, up to a point. Under a regular, non-toxic dose of radiation, the body can deal with the damage caused, and then repair it or simply shrug it off. Often, the body has mechanisms in place to filter out and remove damaged tissues so they can’t continue harming the body. However, this can only go so far — damage to everything from the intestinal walls to the bacteria which support our digestion make nausea one of the most reliable symptoms of radiation sickness. Once this progresses to symptoms in even more sensitive tissues (particularly the nervous system) fatalities start to mount. By the time radiation exposure leads to headache, dizziness, and trouble concentrating, death is all but assured.
The contaminant can be a physical substance as well as a major emissions source; nuclear catastrophes often result in the release of radioactive iodine. This isn’t strongly radioactive enough to cause damage unless it actually enters the body and its metabolic pathways, so its toxicity can be avoided through the use of gas masks and protective suits, along with iodine pills to make sure the body has plenty of healthy iodine to turn over, washing out the effect of any radioactive isotopes that might make their way into the bloodstream.
It’s worth noting that this problem is distinct from cancer as caused by radiation. Damage to DNA can occur due to ionizing radiation, and this can have direct effects due to crippling a cell’s ability to properly make certain proteins. However, only very specific and unlikely mutations will lead to cancer, specifically, and while the cause of those mutations may be radiation we do not consider such cancers to be within the scope of radiation sickness.