This article is an addendum to The Fear of Electromagnetic Radiation
We can easily contrast the non-ionizing electromagnetic sources with the obvious danger of ionizing radiation.
For example, if ultraviolet radiation is 4% of sunlight, then the ultraviolet exposure to our "10 square foot" person is 40 Watts, and 40 Watts / 1440 = 0.028 Watts per square inch. This 0.028 Watts per square inch is able to cause severe sunburn in a fair-skinned, un-tanned person in about 3 hours of exposure time. But the rest of the 1000 Watts, or 0.7 Watts per square inch, after applying sunscreen lotion, will not burn the skin at all, but only warm it.
Moving up in frequency, X-rays range from about 30,000,000,000,000,000 cycles per second (30 Petahertz) to about 30,000,000,000,000,000,000 cycles per second (30 Exahertz). This is about 50 to 50,000 times the frequency of visible light, where visible light is about 200,000 times the frequency of a microwave oven, WiFi, or cell phone.
Let us consider the power of a chest X-ray.
Chest X-ray dosage is around 0.0001 Sieverts (http://www.radiologyinfo.org/en/info.cfm?pg=safety-xray)
Chest X-ray duration is about 0.5 seconds (http://www.theenergycollective.com/willem-post/53939/radiation-exposure)
The human thorax is about 20% of the total body weight (http://www.exrx.net/Kinesiology/Segments.html)
A 180 pound man is 82 KilogramsTherefore,
The thorax of a 180 pound man is 16.4 Kilograms
1 Sievert = 1 Joule/Kilogram = 1 Watt-second/Kilogram
Sieverts * Kilograms / seconds = WattsFor the chest X-ray, then, the thorax of a 180 pound man receives:
0.0001 Sieverts * 16.4 Kilograms / 0.5 seconds = 0.003 WattsAt this power level there is a concern about repeated, cumulative exposure, although a single, half-second chest X-ray is not of concern, since you get that same dosage from normal background radiation in 10 days from natural sources, anyway.
By contrast, a 100% fatal (i.e. medically hopeless) radiation dose is considered to be 8 Sieverts (http://xkcd.com/radiation/).
For example, the X-ray and gamma radiation level in the vicinity of Chernobyl reactor core after the 1986 accident in the Ukraine was 300 Sieverts/hour (http://en.wikipedia.org/wiki/Chernobyl_disaster). 180 pound man would therefore be exposed to:
300 Sieverts * 82 Kilograms / (60 min./hour * 60 sec./min.) = 6.8 WattsTherefore, Chernobyl was 100% fatal (i.e. medically hopeless) at that power level at an exposure time of
8 Sieverts / 300 Sieverts/hour * 60 minutes/hour = 1.6 minutes.Scaling it a different way, for the 180 pound man,
8 Sieverts * 82 Kilograms / (3 hours * 60 min./hour * 60 sec./min) = 0.06 WattsSo, an 180 pound man exposed to 0.06 Watts of ionizing radiation in the form of X-rays and beyond, for 3 hours, will receive such extensive cellular damage that it would be fatal (i.e. medically hopeless).
To recap, 40 Watts of ultraviolet radiation from the sun can cause a severe sunburn to our "10 square foot" man after 3 hours, whereas 0.06 Watts of X-ray and gamma radiation to a 180 pound man for 3 hours is 100% fatal (i.e. medically hopeless). On the other hand, 1000 Watts of radiation from sunlight, after applying sunscreen lotion, does nothing more than warm the skin. What do you expect that 1000 Watts of microwave radiation (200,000 times lower in frequency and that much less energetic than visible light, and 10,000,000 to 10,000,000,000 times lower in frequency and that much less energetic than X-rays) will do, or 2 Watts from a cell phone, or 0.1 Watts from a WiFi hotspot?
[Technical note: The Sievert is a derived measure of the biological effect of absorbed energy from incident ionizing radiation, which is the best measure to use for the purposes of this article. Due to weighting factors having to do with the different types of ionizing radiation and the susceptibility of different parts of the body to each type, the power calculations I have made do not exactly represent the radiated power, and are therefore much more approximate. The point in using the same metric (Watts) is to show the gross disparity between the effect of the power levels of ionizing radiation and those of non-ionizing radiation.]
I grant this work to the public domain.