Concern over radiation exposure has led some local, state, and federal agencies to propose a zero dose limit above background radiation. A zero dose limit means that industry could not allow anyone to be exposed to radiation above the average background exposure per year. Why does background radiation change with altitude? Suggest a reason why the airline industry might oppose a zero dose limit.

Data from problem 14.71

An average person is exposed to about 360 millirem of background radiation per year from a variety of natural and man-made sources. About two-thirds of that typically comes from inhalation of ²²²Rn produced in soil by the decay of ²³⁸U. Given that ²²²Rn decays by alpha emission, estimate the absorbed dose in (a) joules and (b) grays for a 60-kg person from one year’s inhalation of radon.