TRANSURANICS IN TERRESTRIAL ENVIRONMENT 707 



Although, as mentioned, other sites in the world have been contaminated with 

 plutonium, I am not aware of any specific searches for ecological effects at these sites. 

 Competent ecologists have conducted studies on plutonium distribution and behavior 

 within many of these sites, however, and any readily apparent ecological changes would 

 likely have been reported. I am also not aware of any sites at which other transuranics 

 have been released at levels greater than existing plutonium levels. 



Another approach to the study of contaminated environments is to examine areas 

 containing above-normal amounts of the naturally occurring radionuclides. Many areas 

 contain substantial quantities of natural uranium and thorium. These primordial 

 radionuclides and many of their progeny are alpha emitters. Possibly some inferences to 

 the transuranics could be made from studies in areas of high natural alpha activity. For 

 instance, the rodents on Morro do Ferro in Minas Gerais, Brazil, which receive an 

 estimated lung dose of 10^ to 10^ rem/yr, might provide a good study opportunity 

 (Drew and Eisenbud, 1966). Major problems with such an approach include differences in 

 radiation schemes and chemical properties between the naturally occurring and 

 transuranium radionucHdes. We know something about the relative toxicities of ^^^Pu 

 and ^^^Ra (Thompson, 1976) but very little about the relative ecological and 

 physiological behavior and toxicities of transuranics with other naturally occurring alpha 

 emitters. Pochin (1976) points out some other difficulties inherent in trying to quantify 

 biological effects of environmental radioactivity at low levels. 



On the basis of data summarized by the United Nations (1972), I calculate that the 

 upper 3 cm of soil in the United States averages roughly 0.3 juCi of natural alpha activity 

 per square meter. A similar calculation applied to atypically high natural radiation 

 background areas yielded alpha activities of 7 juCi/m^ in the upper 3 cm near Central 

 City, Colo. (Mericle and Mericle, 1965), 50 /iCi/m^ in local areas in Brazil (Eisenbud et 

 al., 1964), and 200 /jCi/m^ in the USSR (Maslov, Maslova, and Verkhovskaya, 1967). 



A number of genetic and ecological studies have been done in some of these and 

 similar areas. Rats occupying a monazite sand area in Kerala, India, had no discernible 

 phenotypic effects (Gruneberg et al., 1966). There is, however, suggestion of radiation- 

 induced genetic damage leading to mental retardation of humans who occupy the same 

 region in India (Kochupillai et al., 1976). Furthermore, Gopal-Ayengar et al. (1977) 

 report genetic alterations in plants indigenous to the monazite belt in Kerala. Cullen 

 (1968) reported preHminary findings of a human cytogenetic study in Guarapari, Brazil, 

 in which an apparently increased incidence of somatic chromosome aberrations in 

 comparison to a control area was found. A high incidence of multiple-break aberrations 

 was noted which was thought to be compatible with the presence of internal alpha 

 emitters. These findings were apparently corroborated more recently by Barcinski et al. 

 (1975). 



Osburn (1961) observed an increased incidence of morphological anomalies and 

 flower abortion in Penstemon virens growing on the more radioactive sites near Central 

 City, Colo. However, the chemical toxicity of thorium and possibly other factors cannot 

 be ruled out as causal. In the USSR, Maslov, Maslova, and Verkhovskaya (1967) reported 

 various deleterious effects on reproduction, parasite infestation, and the general condition 

 of small mammals in areas of high natural radiation. Although radiation was implied as 

 the cause of such effects, it was not the only variable between experimental and control 

 populations. I am not convinced from these studies that naturally occurring alpha 

 emitters, even in the unusually high natural background regions of the world, cause 

 demonstrable ecological consequences. Potential genetic changes in local areas would 



