No abstract

Up to now the names of about 6OOO patients of the Thorotrast group and 6OOO patients of the control group were obtained from records in different hospitals of West Germany. The control group consists of pseudorandomly selected patients from the same hospitals who were admitted at about the same time.The causes of death were ascertained from 1162 patients of the Thorotrast group and 883 persons of the control group, who died before they could be examined in our study, which began in 1 W . Not included are those patients who died within 3 yr after Thorotrast injection respectively after hospitalization. The age at injection was 40 yr, and the survival time 17 yr on the average in the Thorotrast group. The recorded. volumes of injected Thorotrast averaged 30ml. The neoplastic diseases of the organs of interest in these groups had the following distribution (Thorotrast group to control group): liver 88/6; bone marrow 16/1; skeleton 2/0; lungs 25/24; spleen OlO.To date (September 1975) we have examined clinically and biophysically 802 living Thorotrast patients and 622 members of the control group. The mean value of the age at injection in this Thorotrast group was 28yr. and of the time from injection to first examination 26 yr. The mean injected volume of Thorotrast as calculated by the results of whole body counting was 22 ml.Since the beginning of these examinations 171 Thorotrast carriers have died. From the hospital records of these patients it is remarkable to note the excessive large number of liver tumors (51) and the high incidence of leukaemias (5). The patients who developed malignant neoplasias of the liver were injected on the average with 33ml Thorotrast. Patients who suffered from leukaemia received only about 17 ml. Thorotrast. The accumulated radiation dose (mean exposure time 30 yr) in liver, spleen, lungs, bone marrow and skeleton are calculated from the results of the whole body measurements.Final conclusions concerning the frequency of late effects and its relation to the tissue dose depend on further results of follow up studies.

This paper discusses different possibilities of deriving reference values for the natural radioactivity concentrations in building materials to estimate possible additional radiation exposure for the population. Based on comprehensive experimental and theoretical investigations the consequences of the resulting hypothetical reference activity concentrations in building materials, applying different dose limits, were examined. The calculation of the activity concentration standards was performed for standard conditions obtained by earlier studies on exhalation of Radon-222 and Radon-220 from building materials.

Tissue equivalent proportional counters (TEPC) operated at low gas pressures can be used to measure simultaneously ionisation distributions induced by single events and, with a low overall uncertainty, absorbed dose or kerma. TEPC measurements were performed in a low scattering environment for monoenergetic neutrons with energies of 13.9, 15.0, 17.0 and 19.0 MeV. Neutron Auence and spectral neutron fluence were determined with a proton recoil telescope and an NE 213 scintillation counter. Control measurements permitted detailed analysis of and correction for scattered and parasitic neutrons. The kerma factors for A-l50 plastic at 13.9, 15.0 and 17.0 MeV obtained from the TEPC measurements agree very well with calculated values.At 19 MeV the measured kerma factors are significantly lower. The ionisation spectra provide information on kerma fractions due to different types of secondary charged particles. The measured spectra suggest that the difference in kerma factors at 19.0 MeV is mainly due to differences in kerma related to alpha particles, especially by the '*C(n, n' 3 a ) reaction. The results show that the combination of accurate fluence and TEPC measurements enables the determination of basic data for fast neutron dosimetry and neutron interactions.

Measurements of the concentrations of 222Rn, its short-lived decay products and of 212Pb - 212Bi were performed in 150 dwellings and in the open air in the Federal Republic of Germany. The concentrations of 222Rn was measured by electrostatic deposition of 218Po. The concentration of the short-lived decay products were measured by air sampling and alpha-spectroscopy. It was found that inside dwellings the average potential alpha-energy concentration of the short-lived daughters is about three times higher than in the open air. The total potential alpha-energy concentration indoors amounts to 2.6 . 10(-3) Working Level (W.L.). Direct measurements of the equilibrium factor inside dwellings gave a mean value of 0.3. A strong dependence of the potential alpha energy concentration on the ventilation rate in dwellings has been observed. These ventilation effects exceed the effects caused by differences in the activity concentrations due to different building materials. The dose calculation results in an average dose to the whole lung due to the inhalation of short-lived radon daughters of about 0.05-0.2 m/Gy/a. An estimate of risk - based on the risk factors for uranium miners - shows an average lifetime risk of about 6 . 10(-4) for the incidence of lung cancer caused by inhalation of radon and thoron daughters in dwellings in the Federal Republic of Germany.