Human exposure to radiation is often measured in "rems" (roentgen-equivalent-man), or millirems. the cancer risk caused by exposure to radiation is thought to be approximately 1 fatal cancer per 8000 person-rems of exposure (e. g., 1 death if 8000 people are exposed to 1 rem each, or 10,000 people exposed to 0.8 rem, (a) natural radioactivity in the environment is thought to expose people to approximately 130 mrem/yr. how many cancer deaths in the united states (population 320 million) would be expected per year from this exposure? (b) a single 3000-mile, cross-country jet flight exposes an individual to approximately 4 mrem. how many flights would be required to increase an individual's cancer risk by one in one million?