therefore necessary to wash and remove the radioactivity from the boat, clothes and the human body. For reference, the radioautograyphs of the letters written by the oil which was on the deck of the Koei Marw and the gloves of the crew are shown in Figure 5. 4i. About the Tuna. Since different people have different interests in this subject, it involves many intricate problems. I will simply refer to the medical aspect of this problem. The question is then how much of the radioactive - ash can be eaten together with the tuna without violating the safety of the human body. This is again not a simple problem. First of all, the ash itself consists of various elements and they are absorbed in the Tuman body at various rates. Even the same element will be absorbed differently according to the form of compounds they constitute. Furthermore, they deposit in various organs such as the bone, kidney, liver and thyroid. Different elements have different half-lives both physical and biological. To simplify the argument, we shall assume for the mrent that the ash consists of only the most dangerous element Sr?9, In the usual form of compounds, about 60% of Sr90 is absorbed by the body through digestive orgens and about ho’ deposits in the bones, Its physical half- life is about 20 years, while the biological and effective half~—lives are 3.9 x 10? days (about 10 years) and 2.7 x 103 days (edout 7.4 years), respectively. It is therefore very difficuit to discharge once it dcposits in the bones, The permissible dose of deposit in the body is 1 micro- curie. Since hOZ of the absorbed strontium deposits in the bones, it is to eat more than 2.5 microcuries. It is not unambiguous how much radioactivity of 2.5 microcuries will give to the G.M. counter since it depends on the geonetry, measuring instruzent, the of the mice window of tne G.lf. counter, etc. But, roughly it may be about 5000 ct/min. Since the sefety limit adopted today is 100 ct/min at the distance 10 cm, it may be concluded thet it is not dangerous at all to eat the tuna though the above calculation270°, ok ann pis _ pet based on several assumptions. ae dangerous count the at 10 cm, thickness speaking, Wnet ceeSure should be teken when the redicaciive substance entered wne body or cne is exposed to the external radietion to such an extent that certain injury is expected? Tne first thing to do is io have the biood-counting several times. checked carefully. If eny encnaly is found, one hes to be Next, the radioactivity in the urine should be neesured. We shall not discuss it in deteils here. he aioactive rein, etc. uw iii. Pail of esh, rain end snow with the redicactivity have been observed at several places in Jepan. Tne cGevail is not available yet. Bat it may not be dangerous to the huzan body end others as fer es the intensity cf naturel and artificial racicactivities re=mzins to be of the present order of magnitude. Conclusion. (onitted) JS §.