Revision 1
March 19, 1998
by Radiation, Science, and Health, Inc.,
Edited by J. Muckerheide

1.2.6
Natural Radiation and Radioactivity

1.2.6.2
Natural Background: Populations

"During its first phase of epidemiological studies in the 1970s BARC could not find any significant difference between the groups exposed to different radiation levels. The indicators of genetic change employed by BARC were: sex ratio among offspring; fertility index; infant mortality; pregnancy terminations; multiple births; gross abnormalities."

"The fact that per capita daily intake of gross alpha, gross beta, 85 keV gamma, radium-228 and potassium-40, activity are estimated to be 215, 3648, 96, 162 and 3551 pCi, respectively (Mistry et al 1965) and that urinary excretion of thorium and Ra-228 in male adults residing at Chinnavilai village (HBRA) are at least an order of magnitude higher than those collected from subjects residing at normal background radiation level areas (Paul et al 1994) emphasizes the urgent need to assess the body burden of the radionuclides in the individuals of the HBRA inhabitants who have significantly greater incidence of dicentrics and rings than the normal frequency expected in relation to their age."

"At the outset, it is pointed out that Verma et al. (1975) reported a substantially increased frequency of chromosomal aberrations in the HBRA populations as compared to that in the normal (control) populations. The most common types of chromosomal aberrations observed by them were deletions and acentric fragments. They had however, noted that the frequency of dicentrics and rings was considerably lower. These authors from the All India Institute of Medical Sciences, New Delhi had also published (Kochupillai 1976) a paper claiming a higher incidence of Down syndrome births in the HBRA of Kerala; however this had met with a great deal of criticism including the total absence of any Down syndrome case in the control population. Today, their own data base for Down syndrome collected from various parts of India (Normal background levels of radiation) render their earlier report in Nature of greater incidence of Down syndrome in the HBRA population invalid. The point is that the reported incidence of Down syndrome in the HBRA population is just not different from its incidence elsewhere in India.

"So far as the human cytogenetic data of BARC is concerned, the studies at this point (meaning that these studies are still going on) suggest the following:

"(i) With reference to the unstable aberrations (dicentrics and rings), an increased frequency becomes somewhat discernible only in the adult populations. However, the data are quite scattered and no precise conclusions could be drawn at this juncture. Therefore, the studies are still in progress to clarify the situation.

"(ii) In the newborns, there is no significant difference in the incidence of chromosomal aberrations (dicentrics + rings) and micronuclei in peripheral lymphocytes between the control and HBRA populations. While the BARC data on the adult populations do not yet allow an unequivocal conclusion that dicentrics + rings are significantly greater among the inhabitants of the HBRAS, the Chinese data (DeQing and Wei 1991) are significant (P < 0.05) in this regard. If further studies establish that the inhabitants above a certain age in the HBRAs have indeed significantly higher frequencies of dicentrics and rings and/or translocations, then the role of body burden of radionuclides would have to be considered. It has been reported (8) that the mean daily intake of Ra-228 by the population living in the monazite area of Kerala is about 162 pCi which is about 40 to 50 times the normal daily intake of this radionuclide."

"The HBRA studies so far carried out, within the scope of their resolving power, have not revealed any adverse biological effects...

"Cytogenetic studies with plants which accumulate considerable quantities of radionuclides and which do not have such mobility and excretory processes as animals implicate internal radiation to be largely responsible for meiotic abnormalities. In fact, external radiation doses up to 8.7 cGy do not induce somatic mutations in the sensitive stamen hair system of Tradescantia."

"More recently, the data base for Down syndrome for different parts of India has become more reliable and acceptable. These are based on about 90,000 births during the past three years. It turns out that the incidence of Down syndrome in the HBRAs of Kerala earlier reported by N. Kochupillai et al. (1976) is not different from that elsewhere."