Genetic risk assessment for potential hazard from environmental tritium to man becomes important with increasing nuclear-power industry. The purpose of this short review is to discuss the possible genetic effects of tritium from a view of genetic risk estimation. The discussion is based mainly on our experimental results on the chromosome aberrations induced in human lymphocytes by tritium at the very low-level. The types of chromosome aberrations induced by radiation from tritium incorporated into the cells are mostly chromatid types. The most interesting finding is that the dose-response relationship observed in both tritiated-water and tritiated-thymidine is composed of two phases. The examination on the nature of two-phase dose-response relationship is very important not only for the mechanisms of chromosome aberrations, but also for the evaluation of genetic risk from low-level radiation.
Coagulation property of particle on the treatment of radioactive waste water by floculation method is varied with its electrical potential and mixing condition. The surface state of the particle is influenced by contents of coexistent materials in the waste water and added materials at the treatment process. In the case of using ferric hydroxide as coagulant, assuming the ions which decide the potential of the particle surface are Fe(OH)2+ and Fe(OH)4-, calculated values of the potential agree with zetapotential of ferric hydroxide particle which is formed from FeCl3 and NaOH in demineralized water. When Na2CO3 is in the waste water as coexistent materials, anion HCO3- or CO32- adsorbs on the particle surface in connection with pH variation and thus the surface charge is being minus. If Ca2+ ion is present in the waste water, the surface charge plus. ABS acts as single molecule anion at low concentration, but it forms micell at high concentration and influences zeta-potential of the particle. The potential of the particle is correlated to the coprecipitation rate of 90Sr in the waste water.
The method of the determination of gross α activity in urine by adsorption on glass fibre filter paper (EAKINS et al.; Health Phys., 14, 461) is considered suitable as a routine procedure. The method was re-examined for both procedure and recovery of some actinoids from standpoint of routine assay. As a result, it turned out that an initial concentration step for the separation of actinoids from urine with coprecipitation with calcium and magnesium phosphate can not be omitted. Recoveries observed by the present study are generally compatible with that of reported by EAKINS et al., for uranium, neptunium and americium, but considerably lower recovery was observed for plutonium. In some cases, very low recoveries were observed for all of actinoids examined, however, the method can be compared advantageously with a gross α activity determination method using coprecipitation. Practically, it is concluded that it requires further investigation specially on the fluctuation of the recovery for actinoids.
It was described in the preceding paper that the recovery of actinoids were sometimes unsatisfactory. In this paper, some experiments on the recovery were carried out. Dependence of pH on adsorption (uptake) with glass fibre filter paper, influence of the presence of ammonium nitrate and calcium magnesium phosphate on the uptake were examined for uranium, neptunium, plutonium and americium. Centrifugation of the solution were also examined. In the case of solution containing calcium magnesium and phosphate, centrifugal experiments revealed that a very small amount of precipitate was formed at pH less than 5.0, and a close relation was found between precipitate formation and uptake or centrifuged out of the actinoids. As the results, it is thought that the actinoids are first coprecipitated with phosphate precipitate, then it is separated by the glass fibre filter paper. The amount of the precipitate may be influenced by the calcium magnesium contents in the sample, or by the conditions of the pH adjustment, and it has an effect on coprecipitation or counting efficiency of the actinoids. Consequently, it seems that some extents of the recovery fluctuation is unavoidable.
The performance of a respirator is governed mostly by the leakage through between mask and face. The leakage has been measured for three types of half mask and two types of full-face mask, worn by about forty persons, in order to examine the usefullness in actual application of the test method using NaCl particles. The particles generated with a nebulizer were fed into the hood in which the subject wore his respirator, and the concentration of NaCl in exhaled air was measured by a flame photometer. The measured values were corrected for the deposition of NaCl particles in the respiratory tract. The leakage of full-face masks differed largely with experience of the wearer. However, a few of persons tested could not be adjusted so as to avoid serious leakage. The problems in application of the present method to field test are also discussed.
A mechanical breathing simulator has been developed to produce the human respiration for use in respirator test. The respirations were produced through the strokes of piston controlled by a rockerarm with adjustable fulcrum. The respiration rate was governed by motor-speed control, independent of the tidal volume achieved by adjustment of the piston stroke. By the breather, the simulated respirations for work rate 0, 208, 415, 622 and 830kg-m/min could be produced through the typical dummy head.
The consumption of marine foods such as fish, cephalopod, crustacea, shellfish, algae and processed was surveyed on three kinds of families in Kuji town and Tokai village. The average daily intake through a year was 224g/d/p for fisherman's families in Kuji, 131g/d/p for native's families in Tokai and 89g/d/p for immigrant's families from city to Tokai village, respectively. Fish accounted for about one-half of whole consumption of marine foods. Fisherman's families showed the highest consumption of all kinds of marine foods except algae through a year. Algae was consumed much by the natives in Tokai.