The task of estimating past environmental exposures to radioactive materials is a complex, multistep process. The first step is to collect data from historical records on the amount of material released. The second is to use records on weather, actual measurements of radioactivity in the environment, and computer models to reconstruct where this material went. The third step is to estimate how this distribution of material might result in radiation exposures to humans. Finally, these exposure estimates can be combined with mathematical models of radiation risks to estimate the resulting harm to people who were exposed.
Radioactive materials released into the environment can affect humans in two ways.
Second, they can enter the body from contaminated air, food, or water and provide an internal source of radiation. Of these environmental pathways to radiation exposure, the food pathway is by far the most complicated. Radionuclides can enter the food chain at many points, through contaminated air, water, and soil, resulting in contaminated fruits, vegetables, meat, and dairy products. The hazards from environmental exposures to radionuclides differ in important quantitative ways from those due to medical procedures or participation in biomedical research. The natural dilution of materials in the environment means that individual exposures even from massive releases are often quite small, although the chemical and biological processes involved in exposures through the food chain can lead to effects that counteract this dilution.