[Limit values, the philosophy of establishing limit values]

Both determination and significance of radiation exposure limits are dependent on the respective situation. The simplest case is the determination of limits for direct effect of a clearly defined radiation dose upon organism, which occurs at doses above a value of about 25 rem. Determination and significance of a limiting value for the maximum permissible dose for radiation workers are also obvious; it indicates the calculated increase of risk and its value (5 rem/a) refers to the "tolerated risk" in other professions. An essentially different situation occurs if the radiation doses in question are far below 5 rem/a, as it is the case in consequence of the Chernobyl nuclear accident. In this case there is no opportunity of determining a relation between radiation dose and its effect in a scientific and objective way: the relation is postulated by extrapolation of the calculated values. There are two possible solutions: either determination of the limit as a certain fraction of the limiting value for professional exposure (as it has been practiced in France and Switzerland), or consideration of the ICRP recommendation to keep the limits "as low as reasonably achievable" with regard to social, economical and psychological factors. Austria has chosen this solution. Public information about origin and meaning of these limiting values is a necessary condition to avoid that a value above the limits is considered necessarily harmful.