will be more than 200 mSv, with no known measurable biologic effect Typical radiation exposures encountered during life and in medicine are listed in Table 90.11 Children generally have a higher relative risk of cancers (leukemia and thyroid, skin, breast, and brain cancer) following radiation exposure compared to adults, likely due to the increased radiosensitivity of their developing organs Also, since children are shorter than adults, they may be exposed to radioactive material deposited on the ground In addition, their shorter body diameters can lead to higher-dose exposures to their internal organs The hazard posed by a radionuclide depends on its quantity, decay scheme, the energies of its emissions, its half-life, and length of exposure For example, a radionuclide that decays by emitting only alpha particles is not a hazard if kept outside the body, since alpha particles cannot penetrate even the dead layers of the skin However, some radionuclides (e.g., 131Iodine) that are readily absorbed by the body and/or are concentrated by an organ can be a hazard in small amounts Although the radiation doses to personnel involved in the care of a victim contaminated by radioactive material are likely to be very small, simple protective measures should be employed to minimize the doses There are three methods of protection from radiation exposure: minimizing time of exposure, maximizing distance from the material to the extent practical, and using shielding as appropriate The amount of exposure received is directly proportional to the time spent near the source of radiation Distance is the most practical and effective method of reducing radiation exposure because the dose decreases by the square of the distance ( Fig 90.11 ) This is known as the inverse square law The lead aprons used in radiology departments, where the radiation comes from low-energy, scattered, nonparticulate radiation, are not generally useful in radiation event management Lead aprons not provide effective protection against the higher-energy radionuclide emissions likely to be encountered with radioactive contamination