To assess the possibility of application of H₅-DTPA for the chelating treatment in the accidental contamination with radioactive metal elements, the experimental treatments with Ca- and H₅-DTPA were carried out in rats of which lungs were instilled with ⁵⁹Fe-iron dextran. After the instillation, the animals were treated by DTPA on the 2nd day and sacrificed on the 7th day. The lung retention of ⁵⁹Fe was significantly decreased and the urinary excretion was remarkably increased by the intratracheal instillation of Ca-DTPA at doses of 30 and 300μmol/rat. While the intratracheal instillation of H₅-DTPA of 30, 100 and 150μmol/rat significantly increased the urinary excretion of ⁵⁹Fe, its effectiveness was about half that of Ca-DTPA. On the other hand, no significant change was observed after either the subcutaneous implantation of H₅-DTPA or intraperitoneal injection of Ca-DTPA at the same dose level.

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⁶⁰Co, ¹⁰⁶Ru (ニトロシルニトロ錯体, ニトロシルニトラト錯体, ニトロシル複核錯体ならびにクロロ錯体) および¹⁴⁴Ceの各放射性核種について, 海水中における時間経過による物理化学形の変化をイオン交換膜を通した電気透析法, あるいは一次元高電圧濾紙電気泳動法により検討するとともにニトロシルルテニウム錯体についてはペーパークロマトグラフ法によっても研究した。
⁶⁰Coは海水中において, 電気透析法ならびに濾紙電気泳動法によって時間経過に伴って加水分解によるハイドロオキシ錯体を含めて単一な陽イオン形ではなく, また海水中に存在する陰イオン, とくにSO^2-と結合した電気的中性のイオン対 (CoSO₄^2-) の生成が認められた。
¹⁰⁶Ru-クロロ錯体は, 海水中において主として陰イオンおよび電気的中性形からなり, 陽イオン形はむしろ少なかった。しかし, 電荷をもっているものもコロイド形あるいは粒子形で存在するものが多かった。
ニトロシルルニテウムのニトロ, ニトラトおよび複核の各錯体の調製原液を濾紙電気泳動法によって調べた結果, 各錯体の化学形によってその存在状態に特徴がみられたが, また海水中投入後においては高次のニトロ, ニトラトおよび複核の各錯体は加水分解されて, それぞれ低次の錯体となることが示された。
¹⁴⁴Ceについて電気透析法によって調べた結果, 海水中においても当初陽イオン形を示していたが, 時間経過とともに電気的中性形および陰イオン形がつくられ, 比較的大きなガラス器壁への吸着性を示した。

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Based on the prescribed diffusion model we estimate yields of water radicals by ³H β rays. A radical in a spur reacts with radicals in the same spur and in the nearest neighbour spurs according to the track structure of electrons and to the process of diffusion. The basic idea of the model is that 1) a concept of interspur distance in an electron path segment is introduced to take into account the track structure in the differential equations for many-radical system, 2) the differential yields for each path segment are summed up to give the integral yields by averaging over electron energy degradation spectrum, and 3) G-values of the species formed by ³H β rays are obtained by integration over the primary β spectrum. Optimum values for the parameters in the model were determined by comparison with experiments for Fricke dosimeter. The result indicates that the ratios for H₂ and H₂O₂ exceed one among the ratios of yields of species by ³H β rays to those by ⁶⁰Co γ rays.

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According to the method developed by US National Institute of Health, probability of causation of cancer (PC) by radiation which evaluates numerically how previous exposure to radiation contributed to the occurrence of cancer was calculated for Japanese population using appropriate data for cancer incidence and life table in Japan. In this study, PC estimates were obtained for cancers of esophagus, stomach, colon, liver, pancreas, lung, breast and thyroid, and leukemia.
For cancers other than leukemia, the relationship between PC estimates and age at exposure was classified into the following three types:
1) cancers of esophagus, liver and breast for which PC estimates decrease with increasing age at exposure;
2) cancers of stomach, colon, pancreas and lung for which PC estimates decrease to a certain age and then increase;
3) thyroid cancer for which no clear relation between PC estimates and age at exposure is observed.
For leukemia, for which time from exposure to diagnosis was assumed to have a log-normal distribution, PC estimates reach their maximum several years after exposure and then decrease with age.
Differences were found in PC estimates between Japanese and US populations due possibly to the differences of baseline cancer incidence. The temporal pattern of PC estimates was, however, found to be similar, reflecting the similarity of the temporal pattern of cancer incidence with age in the two populations.

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