[en] A summary is given of a three-day meeting held in Taishan in November 1988 to review the results obtained in a comparison between two areas in Southern China, of widely different radiation rates from natural sources. Both the internal and external dose rates of the inhabitants of the two areas have been studied in detail since 1975 and these results are discussed in relation to cancer mortality rate, congenital malformations, reproductive disorders and chromosomal aberrations in the two areas. (UK)

[en] This lecture discusses the basis for estimating the risks of radiation exposure, both occupational and general, and the possible risks from exposures too low to give any readily detectable increases in malignancies or other effects

[en] The report gives a survey of radiation dose (to the whole body or to certain organs) to the Norwegian population, caused by various radiation sources. It also estimates the probable number and category of injuries caused by these doses. Comparative evaluations of occupational radiation health hazard and other occupational health hazards are given

[en] Estimates are given of the total radiation dose from all forms of ionizing radiation resulting from nuclear power reduction. A power consumption of 1kW per head of population, derived entirely from nuclear energy, would increase the average radiation exposure of the whole population from 100mrem per year from natural sources (plus about 40mrem per year from medical procedures and other artificial causes) by about 6mrem per year. The genetically signifificant component of this increase would be about 4mrem per year. Available estimates of harm from radiation would indicate that this would give a risk per year per million of population of about 1 fatal induced malignancy, about the same number of malignancies fully treatable by operation, and, after many generations, about the same number of inherited defects, of greater or less severity, per year. Accidental injuries, particularly in constructional and mining work, would cause an estimated 1 fatality and 50 other accidents annually. Indications are given of the number of fatalities and accidents involved in equal power production by alternative methods, and of the value and limitations of such numerical comparisons in reaching decisions on the development of future power programmes

[en] Due to the epidemiological records of populations exposed to radiation it is now practical to make good numerical estimates of the risks of radiation at moderate doses and influences of the low-dose risk. Estimates of the effects of radon and radon daughters on induction of lung cancer is discussed. Specific topics addressed are: types of radiation effect, requirements in radiation epidemiology, specification of dose, sensitivity of different organs, needs with regard to population size, conditions needed in a comparison population, and the significance of latent intervals

[en] In an increasing number of situations, it is becoming possible to obtain and compare numerical estimates of the biological risks involved in different alternative sources of action. In some cases these risks are similar in kind, as for example when the risk of including fatal cancer of the breast or stomach by x-ray screening of a population at risk, is compared with the risk of such cancers proving fatal if not detected by a screening programme. In other cases in which it is important to attempt a comparison, the risks are dissimilar in type, as when the safety of occupations involving exposure to radiation or chemical carcinogens is compared with that of occupations in which the major risks are from lung disease or from accidental injury and death. Similar problems of assessing the relative severity of unlike effects occur in any attempt to compare the total biological harm associated with a given output of electricity derived from different primary fuel sources, with its contributions both of occupation and of public harm. In none of these instances is the numerical frequency of harmful effects alone an adequate measure of total biological detriment, nor is such detriment the only factor which should influence decisions. Estimations of risk appear important however, since otherwise public health decisions are likely to be made on more arbitrary grounds, and public opinion will continue to be affected predominantly by the type rather than also by the size of risk. (author)

[en] As a basis for establishing radiation protection standards, a substantial amount of quantitative information is now available on the frequency with which malignant diseases are induced in man by moderately high doses of radiation. Such estimates can now be made not only for irradiation of the whole body but also for exposure of a number of body organs individually. The frequency with which cancers might follow the much lower doses involved in occupational or environmental exposure to radiation, however, cannot be derived from any available epidemiological surveys. It can at present only be inferred by the (probably pessimistic) assumption that the frequency of such effects is linearly proportional to the size of dose received, even down to the lowest doses. Increasing information as to the probable form of the actual dose--effect relationship for radiation is indicating the extent to which the use of this ''linear hypothesis'' may overestimate the risk of low doses as inferred from the observed risk of higher doses. A linear hypothesis has been used in the same way for estimating the likely frequency of harm from low doses of chemical substances which have defined harmful effects at high dose. The appropriateness of this procedure depends critically upon the way in which chemical pollutants, or the relevant products of their metabolism in the body, are likely to become distributed through body tissues and cause the relevant harmful effects on cells

[en] It is an essential requirement of good radiation protection that all unnecessary exposure of people should be avoided and that any necessary exposure, whether of workers or of members of the general public, should be minimized. It is, however, an additional requirement that such necessary exposures should not exceed certain stated limits. These principles are based on the possibility that even the smallest exposures may involve some risk of harm, that any risk of harm should be justifiable by the circumstances necessitating it, and that risk should always be limited to an appropriately low level. The bases for establishing exposure limits must therefore involve an assessment of the risk involved in any form of radiation exposure, and an opinion as to the degree of safety that should be ensured in circumstances which necessitate any occupational or public exposure to radiation. There is increasing quantitative evidence on the frequency on which harm, and particularly the induction of malignancies, may be caused in people exposed to radiation at high doses; and somewhat clearer bases than previously for inferring the possible frequencies at low doses. It is therefore easier to assess the degree of safety ensured by restricting radiation exposure to particular levels. It is clear also that a comparable degree of safety should be ensured whether the radiation exposure involves the whole body more of less uniformly, or individual tissues or organs selectively. The ''weighting'' factors appropriate to irradiation of particular tissues from internal emitters can thus be defined in terms of their likely individual contributions to the harm of whole-body irradiation. In this way the limits for different modes of exposure by external or internal radiation can be related so as to ensure that protection should be equally effective for different distributions of absorbed dose in the body. In particular, the over-simplified concept of a single critical organ determining the permissible intake of an internal emitter can be replaced by a limitation based upon the levels of exposure of all tissues in relation to their estimated sensitivity to the induction of radiation effects. (author)

[en] The author presents an outline review of his twenty five years' experience as a founder delegate and UK representative of UNSCEAR, from which post he retired in 1982. (U.K.)

[en] In its Publication 26, ICRP recommends a system of radiation dose limitation that is designed to ensure adequate protection from the harmful effects of radiation in conditions both of occupational and of environmental exposure. Clearly, however, no such system can be recommended or accepted as sufficiently safe unless the risks of the resultant exposures have been quantitatively assessed. Publication 26 reflects the increasing quantitative information that is now available on (a) carcinogenic risks of radiation in man, both from exposure of the whole body and from that of individual organs, at moderate exposures; (b) theoretical bases for inference of risk, from moderate to lower exposures; (c) genetic risks in the mouse, and inferences from such risks to those in man; (d) the dose equivalent levels at which certain non-stochastic effects may be induced. Despite a number of uncertainties, substantially improved estimates can therefore be made of the levels of safety that are likely to be achieved by observing the Commission's recommended dose limits, and the associated system of limitation of exposures to levels as low as reasonably achievable below these limits. Both for occupational exposure and for the exposure of the members of the public, these estimates are expressed in Publication 26 in terms of the risk of inducing fatal malignancies or serious hereditary ill health. These frequencies are compared with those of occupational fatalities in other industries or with accidental fatalities amongst the general public. The comparison between harm from radiation and from other agents in different industries is extended in ICRP-27 (on ''Problems Involved in Developing an Index of Harm'') in a review of the time lost through occupational diseases and non-fatal accidents, as well as from fatal diseases and accidents, so that the levels of safety achievable by the Commission's recommendations can be reviewed in the general perspective of occupational safety. (author)