Radiation is a constant presence in our lives

year. The key factor here is modern, well insulated housing which allows the radon to accumulate. People living in more primitive shelter have little to fear from radon gas.

Strategy Page says that the most rapidly growing source of radiation is medical procedures. People are getting more X-Rays and CT scans. The latter really pump out the mrem (1,200 for an abdomen scan, 760 for the chest). PET scans give you 600 mrem. Using radiation to treat cancer can deliver even higher levels, while other radiation treatments tend to deliver much less.

Nevertheless, the increased use of radiation based medical treatments in some industrialized countries has nearly doubled individual mrem exposure. This medical use, however, tends to create a net reduction in deaths because of disease being caught early and cured.

Nuclear weapons are noted for longer-lasting radioactivity as well as instant blast and heat damage. The unit of radiation for nuclear weapons is the rad, which is equal, for our purposes, to 1,000 mrem. Radiation kills over time. If enough radiation is received in a short period, it can kill immediately or within days, weeks, or months, depending on the dose. Six hundred or more rads can kill within hours and disable immediately; 500 to 600 rads are always fatal, often within days. About 50 percent will die with 200 to 500 rads. At levels of 100 to 200 rads, 5 percent will die, although long term effects (cancer) become a major factor. A 50 rad dose will induce nearly 2 percent early deaths from cancer and genetic defects.

These high levels of radiation exist very briefly, seconds in some cases. In the area closest to a ground level explosion, which is preferred for destroying missile silos, there will be hot spots of intense, longer lasting radiation. One year after the explosion of a one megaton bomb on the surface, the 100 rad zone will be a circular area of 46 square kilometers (7.6 kilometers in diameter). Nearly 4 percent of the population in that area will die prematurely. Many others will suffer radiation sickness. This area should be a forbidden zone, even though it will be teeming with vegetation and small animals. The point of highest radiation in this zone will be the explosion crater, 360 meters wide and 120 meters deep. The next zone as an average of 50 rads and covers 67 square kilometers (9 kilometers in diameter). There will not be as much radiation sickness, but 2 percent of inhabitants will die early. The 10 rad zone covers 300 square kilometers (20 kilometers in diameter). This could be lived in, although there would be three or four early deaths per thousand population. Within a few years, even the crater will be under the 10 rad level.

You can also forget about giant spiders and two-headed mutants. Insects are far more resistant to radiation than mammals. Mutations are generally either fatal or unnoticeable. Natural radiation has been responsible for more mutation than any nuclear war could ever produce.

Radiation may not be our friend, but it is our constant companion.