This information has accumulated during the last 30 years, as a result of detailed epidemiological surveys on groups of people who have been exposed to ionizing radiation in various ways, and whose records have been examined over the long periods of time during which effects of radiation may be expressed. In consequence it is now practicable to make good numerical estimates of the risk of radiation exposures at moderate dose, and inferences of the risk at low dose. This is true particularly for the effects of radon and its radioactive daughter products, for which numerous and reasonably consistent estimates have been made of the induction of lung cancer; and any 'genetic' effects in causing inherited disease are likely to be negligible since the doses delivered to the germinal tissues are so small.
