46 BIOLOGICAL EFFECTS OF ATOMIC RADIATION 



The prediction of future C" levels in the atmosphere is more complicated because of 

 uncertainties in the rate of mixing of atmospheric carbon with the oceans. It is estimated that 

 about 25 X 10"' atoms of C have been added to the atmosphere by all atomic tests to date. 

 At most, the concentration of C* in ground level air will increase by about 70% of natural 

 background in the next few years. However, complete mixing with the surface waters of the 

 oceans should reduce this excess to about i of the natural background within a few decades; 

 eventually mixing with the deep ocean layers will cause a reduction to 1% or less of the 

 natural background, since deep ocean layers contain over 50 times more exchangeable carbon 

 than the atmosphere. 



VI. Conclusion 



Although the prediction of future levels of artificial radioactivity given here is uncertain 

 in detail, it is believed that the overall picture is becoming clearer. The next few years should 

 see even more improvement in our understanding of world-wide fallout, particularly if no 

 further testing takes place. Such phenomena as the postulated spring maximum in strato- 

 spheric fallout, the apportionment of debris between the northern and southern hemispheres, 

 and the locations and intensities of stratospheric-tropospheric exchange processes will become 

 better understood as observations now being made are processed and evaluated. Study of the 

 distribution of tungsten-185 and rhodium-102 from the 1958 Pacific test series and additional 

 soil and air concentration data will serve to clarify further many of the points of uncertainty, 

 adding a new fund of knowledge to our understanding of atmospheric circulations. 



Harry Wexler, Chairman H. G. Houghton 



Lester Machta, Rapporteur W. W. Kellogg 



Charles E. Anderson Heinz Lettau 



R. R. Braham, Jr. Robert J. List 



Merril Eisenbud N. M. Lulejian 



D. Lee Harris E. A. Martell 

 B. G. Holzman 



