Recently, significant interest has developed regarding the effects of exposure of the human body to electromagnetic fields, especially related to the issue of whether or not electromagnetic fields have carcinogenic potential. In today's living environment, there are many devices that generate electromagnetic fields, such as MRI machines used in medical care, electrical power transformer stations and power lines, which generate alternating magnetic fields, electric household appliances and, in the future, linear motor cars. In addition, exposure to high-frequency electromagnetic fields has increased due to the recent growth in the use of mobile phones—more than 90 million mobile phones being used in Japan alone. Therefore, human beings are exposed to electromagnetic fields much more frequently than in the previous natural environment. Here, I review the present status of investigations regarding the effects of extremely-low-frequency (ELF) and radio-frequency (RF) electromagnetic fields on living organisms; especially on the response of cells and genes to these electromagnetic fields, including studies conducted at my institution. Animals and epidemiological studies on the effects of ELF electromagnetic fields are also reviewed. I also introduce an evaluation on carcinogenic effects of electromagnetic fields conducted by the International Agency for Research on Cancer (IARC), where I was a member of a working group and participated in the evaluation meeting at IARC.
The International Commission on Radiological Protection is composed of a main commission and four standing committees: Committee 1 on Radiation Effects, Committee 2 on Doses from Exposure, Committee 3 on Protection in Medicine and Committee 4 on the Application of the Commission's Recommendations. Committee 2 used to be responsible for Derived Limits, but is currently responsible for Doses. From 1993 to present, Committee 2 has discussed a wide range of subjects including age-dependent doses for members of the public, dose coefficients for embryos and fetuses, doses for newborns from radionuclides resulting from ingesting mother's milk, basic anatomical and physiological data for use in radiological protection—reference values, human alimentary tract models for radiological protection, and dosimetric quantities used in radiological protection. Some of the subjects have been already published as ICRP reports.
The authors studied the feasibility of utilizing ebonite as a personal neutron dosemeter in criticality accidents. A disc-shaped ebonite, a hard rubber containing 30wt% sulfur, can be used as a highly effective criticality neutron dosemeter because of a simplicity of measurements of beta activity arising from 32S(n, p)32P reactions. The counting efficiency of beta particles with an end-window GM counter for an ebonite disc in 50mm diameter and 3mm thick was determined by 252Cf neutron irradiation. The neutron spectrum dependency of 32P activity per neutron dose was computed using Monte-Carlo calculations of various neutron spectra that could be encountered in criticality accidents, and the results were tabulated as a set of spectrum correction factors. Performance tests using the SILENE reactor indicated that neutron doses could be evaluated within ±15% with the application of suitable correction factors.
Indoor radon has been determined to be the second leading cause of lung cancer after tobacco smoking. There is an increasing need among radiation practitioners to have numerical values of lung cancer risks for men and women, smokers and non-smokers exposed to radon in homes. This study evaluates individual risks for the Japanese population exposed to indoor radon at different radon concentrations and for different periods of their lives. Based on the risk model recently developed by U. S. Environmental Protection Agency (EPA), individual risks of radon induced lung cancers are calculated with Japanese age-specific rates for overall and lung cancer mortalities (1996-2000) as well as the Japanese smoking prevalence data in 2002. Convenient tables of lifetime relative risks are constructed for lifetime exposures and short exposures between any two age intervals from 0 to 110, and for various radon concentrations found in homes from 25 to 600Bq/m3. The risk of developing lung cancer from residential radon exposure increases with radon concentration and exposure duration. For short exposure periods, such as 10 or 20 years, risks are higher in middle age groups (30-50) compared especially to the later years. Individuals could lower their risks significantly by reducing their radon exposure levels earlier in life. The tables can help radiation protection practitioners to better communicate indoor radon risks to members of the public.
Reacting upon the increasing concern of possible harmful effects due to radon, more and more countries established, or intend to establish in the near future, legislation for the radon level both for homes and workplaces. The dose due to radon seems to be more complicated to assess for workplaces than for homes, although the basic principles of dose estimation are the same. The doses at workplaces need to be estimated by individual approaches, but such requirement is usually not reflected in the legislations. The present study deals with characteristic situations and refers to findings and considerations in the cases of offices, schools, underground workplaces, and open air working situations with relatively high radon level. It discusses the possible inaccuracies caused by the improper selection of time periods and methods in the measurements of the average radon concentration. The purpose of this paper is to provide some examples (mainly based on the authors' experiences) to show difficulties that might emerge in the determination of average radon concentrations in various workplaces. This will help choose the proper measurement methods for each case and contribute to the regulator's work in the precise and unambiguous legislation phrasing.