Human Genetics Studies in Areas of High Natural Radiation: I. Methodology

Abstract

SummaryThis paper reviews the investigations in the field of the effect of natural radiations on human populations, and discusses a number of problems inherent to retrospective genetic studies of human populations living under high levels of natural radiation. The solutions to face, at least partly, such problems are presented and discussed with special reference to the Brazilian “Projeta Espírito Santo” (PES).In summary, the main PES subjects presented and discussed are as follows:1) The data, including about 7000 couples and 40000 pregnancy terminations, have been fully collected and are presently under analysis. They were gathered from January to October 1961 by a team of specially-trained female interviewers employing a standard questionnaire, making home visitations, and being directly supervised by the present author;2) The reporting has been practically consistent both within and between populations throughout the whole field work. Biased contribution both from the interviewers and the informants was probably negligible. The collection of the data was not subject to any subjective factor related to problems of radiation effect.3) The interviewers came from the same socio-economic level from which the majority of the people interviewed belong. They were rather familiar with the region and had a perfect understanding of the culture of the people.4) A checking survey was performed to estimate the reliability of the data, with good results.5) No propaganda or publicity has been made preceding or during the field work. This reduced the probability that people and the field work team knew o our interest in radiation problems.6) Although efforts were made to have good descriptions of the abnormalities, and good information on the causes of deaths, unfortunately accurate diagnosis was not possible.7) Cultural and religious practices probably do not affect differently reproduction in the radioactive and control areas, and socio-economic conditions seem to be roughly similar.8) It is difficult to know the cumulative radiation dose to the parents of the individuals analyzed (an attempt regarding this point will be made when the data are analyzed). The mean individuals living in the control, intermediate and radioactive areas are probably subject to minimal gonad-doses of about 2, 3, and 7 r in a 30-year period, respectively.9) No attempt was made to study the influence of radiation on the rate of mutation at specific loci, but an analysis will be made of the genetic characteristics of the populations assumed to be conditioned or influenced by mutations at many loci.10) As has been duly pointed out in this paper, the “Projeto Espírito Santo” (PES) was not specifically planned to demonstrate, with conclusive results, the genetic effect of natural radiation. Although some positive result is possible, it is highly improbable.