First centennial history of the concepts on radiation dose was reviewed. In principle, investigations were made on the original texts. Inevitabilities of the history were searched for and morals from the history were discussed. Underlying problems were extracted and directions to improve the system of radiation dosimetry were suggested. In this Part I, the fundamental dose is treated, while in Part II, which will appear in near future, the protection dose will be discussed.

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Aerosolization of the chelating agent, Ca-DTPA (diethylenetriaminepentaacetic acid), was studied for removal of inhaled radioactive particles. Four methods of generating aerosols from the powder and from the solution were examined. The particle size and concentration of the Ca-DTPA aerosols were measured by the API Aero-Sizer. The aerosol particles generated by the dry powder inhaler were over 40μm in MMAD (Mass Median Aerodynamic Diameter) and might be too large for administration to the deep lung. The sizes of aerosol particles generated by other three methods (dispersion dust generator, compressed air nebulizer and ultrasonic nebulizer) ranged from 2 to 15μm in MMAD, and those concentrations were over 10mg/m³ at maximum. The generated chelate aerosols were evaluated as inhalable and applicable for inhalation therapy.

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The health effects of low doses and low dose rates exposure to human bodies have not been clarified yet. Under this situation, the Radiation Effects Association entrusted by the Science and Technology Agency of the Japanese Government began a survey entitled “The Epidemiological Study on Nuclear Industry Workers.”
The study population consisted of 114, 900 workers in the nuclear industry. Their vital status and identification of cause of death were confirmed by residence registration records and by magnetic tapes of National Vital Statistics, respectively. Their dose information was obtained from the Radiation Dose Registration Center for Workers. The total population dose of the study population was 1, 598.5 person-Sv, and the mean cumulative dose per individual was 13.9mSv. The study period was between 1986 and 1992, average follow-up period being 4.6 years. There were 1, 758 deaths including 661 of all malignant neoplasms among the population.
The SMR was used to compare mortality among members of the study population and that of Japanese males in general after adjustment for age distribution. Furthermore, members of the population were grouped by cumulative dose groups, and the O/E was calculated to test whether there is a trend for the death rate to increase with dose.
The present study demonstrated no evidence of any effect of low level radiation upon health, particularly upon the cancer mortality.

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The time dependency of filter performance across a high-efficiency particulate air (HEPA) filter was experimentally studied. The experimental study was carried out using a HEPA filter (203×203×150mm) clogged with liquid particles (mosquito stick aerosol). The aerosol concentration for filter loading was 0.84mg/m³ and the size distribution was similar to lognormal distribution (CMD=0.21μm, δg=1.65). The mass loading was about 60g/m² when the pressure drop across the HEPA filter reached twice the initial pressure drop. The DOP particle penetrations through the HEPA filter were evaluated when relative pressure drops (ΔP/ΔP₀) were nearly 1.0, 1.3, 1.4, 1.6, 1.8 and 2.1. The most penetrating particle size (MPPS) was almost independent of the mass loading if the face velocity was constant. However, the DOP particle penetration increased remarkably with mass loading, and the tendency of increase was not affected by particle size or face velocity.

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Based on the results from an analysis of the fallout collected in Fukuoka Prefecture in fiscal years 1965-1994, further analysis was carried out to determine the relation between gross β activity and some radionuclides, such as ⁴⁰K, ⁹⁰Sr, ¹³⁷Cs and so on, which are regarded as key nuclides in assessing radiological impact on human health. Gross β activity in fiscal years 1964-1984 decreased in accordance with a regression curve given by F(x)=2.58×10⁶e^-0.126x, where r=0.655. The gross β activity during the period of fiscal years 1965-1981, when the influence of atmospheric nuclear explosion tests prevailed, was found to be in the range of 3.70-61, 700MBq/km², among which 64% of the data was lower than 200MBq/km². The mean contributions of ⁹⁰Sr and ¹³⁷Cs to gross β activity were estimated to be only 1.9% and 3.4%, respectively. No significant correlation was found between the radioactivities of these two nuclides and gross β activity.
After 1982, gross β activity decreased to a level ranging from ND to 666MBq/km², in which 50% of the data was evaluated to be ND. In recent years, natural ⁴⁰K is found to be the major contribution to gross β activity.

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Electromagnetic devices such as superconducting magnets, magnetically levitated vehicles and magnetic resonance imaging (MRI) create high magnetic fields within their immediate vicinity. This has generated some concerns over the effects that these fields may have on the outside environment and in particular on living organisms. 50/60Hz magnetic fields are of special concern because living organisms are exposed to them on our environment. The measurement of low frequency magnetic field on our environment is important to find out a possible relationship between magnetic field and health hazards. The low frequency magnetic field measurements in urban locations are presented. We investigated the influence of a strong 60Hz AC magnetic field of about 1.0T on organisms. The high AC magnetic field is generated by using a multilayer eddy-current type AC magnetic generator developed in our laboratory. In this paper, the generation of heat shock protein by magnetic stimulus is discussed in nematode, and in vitro experiments were performed with biochemical reactions, enzyme and DNA synthesis.

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