11

Introduction

new generation networks (e.g., 5G) and for wireless power transfer. As new frequency bands of millime­

ter and terahertz waves begin to food our living environment, it will be necessary to conduct further

research to assess the exposure to electromagnetic feld generated from the new generation technologies

and their impact on human health and global environment. Terefore, the safety study of non-ionizing

radiation to humans, nature and the global environment is being called for. Te efective use of non-

ionizing radiation in the feld of biotechnology is also expected to become increased. For this purpose

and owing to the rapid development of new technologies, it is necessary to conduct basic research on

various forms of non-ionizing radiation from the viewpoint of bioelectromagnetism and to promote

and discuss the possible human risks for humans and also their benefcial use.

Here, a brief overview on the health issues of non-ionizing radiations will be presented. To start with,

several reviews have been published on the biological and health efects due to the exposure to static

electric and magnetic felds (IARC, 2002; ICNIRP, 2009b; Ueno and Okano, 2012; Ueno and Shigemitsu,

2007; WHO, 2006, 2007). Static electric and magnetic felds originate from both natural and man-made

sources. Static electric felds are derived from the earth’s atmosphere as a part of the global electric cir­

cuit. Te naturally originated static electric feld on earth is highest near the surface, ranging from about

100 to 150 V/m during fair weather to several thousand V/m beneath thunderclouds. Static electric feld

depends on temperature, relative humidity, altitude and other weather conditions. Te natural static

magnetic feld of earth originates from the electric current fow in the liquid outer core of the earth.

Tis feld is called the geomagnetic feld. Te geomagnetic feld is described by three components: total

magnetic intensity, declination and inclination. Te geomagnetic feld fuctuates according to diurnal,

lunar and seasonal variations. Te total feld intensity in Japan is around 50 μT. On the other hand,

man-made sources of static electric and magnetic felds are found everywhere in our day life, indus­

trial facilities, medical equipment and through power transmission systems (WHO, 1987, 2006). Static

electric felds do not penetrate the human body but can induce a surface charge. Tis charge may be

perceived through its interaction with body hair and by other phenomena such as discharge (micro-

shock) at sufciently high felds. Teir perception in humans is dependent on various factors and can

range from 10 to 45 kV/m. Static magnetic felds are not perturbed by the human body. Tere are three

well-known mechanisms by which a static magnetic feld interacts with biological systems: magnetic

induction, magneto-mechanical efects and electron spin efects (ICNIRP, 2009a). Based on the evalua­

tion of biological efect research, the WHO carried out a human health assessment of static electric and

magnetic felds (WHO, 2006).

From the ICNIRP defnition, low frequency (LF) is used to describe the felds with a frequency range

from 1 Hz to 100 kHz (ICNIRP, 2003, 2010a, b). In this frequency range, the interaction of electric and

magnetic felds with the human body induces electric felds and currents in the tissues. Te demon­

strated efect is the induction of magnetophosphenes, a perception of a faint fickering light in the

periphery of the visual feld. Tey are thought to result from the interaction of the induced electric feld

with electrically excitable cells in the retina. Te threshold for induction of magnetophosphenes has

been estimated to be low between 50 and 100 mV/m at 20 Hz. Epidemiological studies have suggested

that long-term exposure to 50/60 Hz magnetic felds might be associated with an increased risk of

childhood leukemia. Two pooled analyses indicate that an excess risk may exist for average exposures

exceeding 0.3–0.4 μT. However, there is some degree of confounding and chance that could possibly

explain these results. No biophysical mechanism has been identifed, and results from animal and cel­

lular studies do not support the observation that exposure to 50/60 Hz magnetic felds cause childhood

leukemia. Tere is no substantial evidence for an association between LF magnetic feld exposure and

Parkinson’s disease, multiple sclerosis and cardiovascular diseases. Te evidence for an association

between LF magnetic feld exposure and Alzheimer’s disease and amyotrophic sclerosis has not yet

produced clear conclusion. Overall, research has not shown that long-term exposure to low-level LF

magnetic felds has adverse efects on health. So, ICNIRP’s analysis is that the currently existing scien­

tifc evidence that prolonged exposure to LF magnetic felds is directly related with an increased risk

of childhood leukemia is too weak to form the basis for exposure guidelines. Te perception of surface