Putrid shambling blogs, GIANT overgrown flies, crazy superpowers, what hasn't been attributed to mutation in scifi, and how much of it is really true?
First off, radiation is the energized phase of all matter. Anything can become radiation if sufficient energy is applied to it (i.e. disintegration ). Most radiation can be categorized into two groups, artificial and natural. Radiation doesn't necessarily mean radioactive decay. Light is considered radiation and so are radio waves, but neither of those cause geiger counters (a tool used for detecting radioactive decay) to go off or cause cancer in people.
Natural Radiation: Radiation isn't an entirely artificial process and has existed in the universe since the beginning of time. People are constantly exposed to radiation from many of these sources and most of it isn't harmful.
Solar Radiation: Our sun and other stars are huge sources of radiation. Stars are colossal sources of fission, fusion, and burning and can easily provide enough radiation to kill a person billions of times over every second and keep emitting that level of energy for millions (or even billions) of years. However, most stars are far enough away that the level of radiation that reaches us isn't strong enough to hurt.
The Earth: Our planet itself is moderately radioactive in its core, which is a byproduct of its formation as a planet. However since we live here, it obviously isn't radioactive enough to be lethal and the amounts of radiation released by our planets core is rather small and shielded from us by rock.
Elements in the Environment: Many elemental substances are innately radioactive or have radioactive forms. Examples of this that are common are Carbon-13 (also known as C13, C-13, etc.) which is a radioactive form of normal carbon which is Carbon-12. Carbon isn't particularly radioactive but it is very common, in fact Carbon 13 is so common that it is what is used to date how old pottery, artifacts, bones, and fossils are and is very useful because it is so common and radioactive.
Uranium: This renown metal is actually rather rare and even if you live in an area in which there are Uranium mines or deposits, you have little to fear as it is usually buried underground and isn't concentrated enough to cause harm.
Plutonium: Just as uranium, this renown metal is also very uncommon and only those who work around it ore itself have any threat of becoming contaminated by it.
Radon: This radioactive gas can be a severe health hazard to many people world-wide as it seeps up from the bedrock and through the soil, entering peoples basements and filling it with radioactive decay. If you live in an area where you suspect Radon may be present in the topsoil or bedrock, you can purchase or rent a Geiger Counter and test the area. This machine will tell you how much radioactive decay is occurring near it and you can see if there is invisible Radon gas in your basement.
Artificial Sources of Radiation:
Light Bulbs: Passing electricity through a metal filament in these glass bulbs causes light to fill a room (radiation). Light bulbs are very common, but since the light they generate doesn't involve any radioactive metals you can't get cancer from them.
Laser: Be it a laser pointer or an industrial grade metal cutting laser, the light that is released from a laser is radiation, though not cancerous it is quite powerful and can cause blindness
Microwaves: Microwaves are machines that use a form of radiation known as micro-waves that penetrate into food and cause it to heat up. You cannot get cancer from standing near a microwave, as they don't release that kind of radiation and they are surprisingly safe to be around.
Jewelry: Some green jewelry back in the 60's used to glow in the dark. It turns out that the green paint used in these pieces was actually Radium, a radioactive green metal. No american jewelry and very little foreign jewelry nowadays uses radioactive substances.
X-Ray Machines: These machines fire a powerful focused burst of x-ray radiation. This radiation can penetrate through flesh easily, but are deflected or absorbed by bones. This allows doctors to see the bone structure without having to do surgery to see the bones. X-Ray machines are a very focused device and are not harmful because they are infrequently used.
Nuclear Power Plants: These facilities employ rods of radioactive metals to heat up water and generate steam, producing electricity. Nuclear Power plants are quite safe and there is no contamination to the outside environment unless the reactor room is breached, in which case radioactive water or energy can leak out.
Effects of Radiation:
Since radiation constantly hits us in many different forms and giant bugs or lizards aren't terrorizing cities or devouring people whole, what does radiation do to us?
Radiation such as Light, Ultraviolet Light, Microwaves, and Radio Waves are not powerful enough to damage our bodies and cause virtually no effects to a person.
Radiation such as a radioactive metal decaying or a nuclear bomb going off can cause mutations and cancer.
Radioactive dose is measured in Centigrays (or Grays) and is abbreviated as Gy. Here is a list of the levels of Gy and what happens to a human when exposed to it.
70 Gy Nausea, Vomiting, no sig. risk of cancer 0% fatalities
150 Gy Moderate Vomiting, 33% Infertility, Long-Term Cancer hazard 0% fatalities
250 Gy Severe Vomiting, 50% Infertility, Fatigue 50% in >15 days
2000 Gy All above signs within 5 minutes 75% in >15 days
5000 Gy All above signs within 5 minutes 100% in >48 hours
18,000 Gy Immediate symptoms 100% in >25 hours
Radioactive mutation is a very common, but subtle occurrence. Though cancer is very common, most cancer is not malignant and is merely benign. Examples of this are moles on skin. It takes millions of years for these tiny mutations to affect evolution and create changes in a species. Simply exposing a creature to a large amount of energy will not make it mutate, grow, or evolve. It will almost assuredly kill it if the dose is high enough.