activity allowance antisepsis artificial radioactivity color contamination curiage disinfection disinfestation extenuating circumstances extenuation extenuative fallout flash pasteurization fumigation gilding gloss half-life hygenics hygiene mitigation natural radioactivity nuclear radiation palliation palliative pasteurization qualification radiant energy radiation radioactive radiation radioactivity radiocarbon dating radiolucency radiopacity radiosensibility radiosensitivity sanitation saturation point softening specific activity sterilization varnish whitewash whitewashing