Health Effects

1. Effects of Low-Frequency Electromagnetic Fields on Human Body

1.1 Effects of Low Frequency Electric Fields on Human Body

In the strong electric field environment, individuals may recognize and feel discomfort (tingling sensation); however, electric field itself is mostly shielded by surface (e.g. skin) and does not penetrate into the body.

The exposure limit values recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) are determined to prevent effects of electric fields in human body induced by the external electric fields.

Effects of electric field to human body have been studied since 1950s. The World Health Organization (WHO) published Fact sheet No.322 titled “Exposure to extremely low frequency fields” concluding that “there are no substantive health issues related to ELF [extremely low frequency] electric fields at levels generally encountered by members of the public.”

1.2 Effects of Low Frequency Magnetic Fields on Human Body

1.2.1 Scientifically Established Effects on Human Body (Short-Term Exposure Effects)

When the human body is exposed to very strong low-frequency magnetic fields, electromagnetic induction induces electric currents in the body by, and potentially stimulating nerves and muscles. This phenomenon is referred to as a stimulating effect.

Within the human body, endogenous physiological electric currents flow as a result of brain neuronal activities, heart functions, and muscle activities, observed through electroencephalogram (EEG), electrocardiogram (ECG) and electromyogram (EMG), respectively). If low-frequency magnetic fields were to induce electric currents in the body comparable to or stronger than these endogenous currents, it is considered that they might have adverse health effects due to their stimulating effect.

The retina of eye is considered the most sensitive tissue in human body to the induced currents. For example, exposure of the human head to extremely strong low-frequency magnetic fields, several hundred times greater than the levels encountered in daily life, may lead to a phenomenon like perception of faint flickering lights (magnetic phosphenes).

Although this phenomenon is not an adverse health effect, the exposure limit values of the international guidelines are based on the threshold (the lowest value of causing response) of magnetic phosphenes. This precaution is taken because the retina is a part of central nerve system within the head. From the viewpoint of safety aspect, ensuring that any effects on brain functions are avoided becomes crucial when preventing this phenomenon.　

1.2.2 Scientifically Unestablished Effects on Human Body (Long-Term Exposure Effects)

Large number of studies have examined the effects of daily exposure to low-frequency magnetic fields, falling below the exposure limit values set by international guidelines (effects of long-term exposure). The WHO evaluated huge amount of published scientific papers regarding health effects of extremely low frequency magnetic fields. These findings were published as Fact sheet No.322 “Exposure to extremely low frequency fields”, with the conclusion that “the evidence related to childhood leukemia is not strong enough to be considered causal.” Moreover, WHO added that “scientific evidence supporting an association between ELF magnetic field exposure and all of these health effects” (including other childhood cancers, cancers in adults, depression, suicide, cardiovascular disorders, reproductive dysfunction, developmental disorders, immunological modifications, neurobehavioral effects and neurodegenerative disease) “is much weaker than for childhood leukemia.”

WHO Fact sheet No.322 “Exposure to Extremely Low Frequency Fields”

2. Effects of High-Frequency Electromagnetic Fields on Human Body

2.1 Scientifically Established Effects on Human Body (Short-Term Exposure Effects)

When human body is exposed to very strong high-frequency electromagnetic fields (radio waves), some portions of the energy are absorbed to the body and converted into heat, resulting in an increase in body temperature. This phenomenon is referred to as the thermal effect.
However, if the intensity of radio waves remains below a certain threshold, body temperature will not increase due to the thermoregulatory function of human body (function that maintains body temperature constant through adjustments in blood flow, sweating, etc.).

The Specific Absorption Rate (SAR) is used as the index for assess the thermal effect. SAR quantifies the amount of energy absorbed to body tissue per unit mass over a specific period due to exposure to radio waves.

For radio waves emitted from radio towers and mobile phone base stations, since the sources are distant from human body, whole body is exposed almost uniformly. Conversely, the radio waves from mobile phone handsets, only specific parts of the body (such as the head) are locally exposed. As a result, quantities of whole-body exposure and local exposure are separately evaluated with the indices of whole-body averaged SAR and local SAR, respectively.

2.2 Scientifically Unestablished Effects on Human Body (Long-Term Exposure Effects)

Epidemiological studies investigating potential long-term effects of exposure to radio waves have mainly pursued relationship between brain tumors and mobile phone use. However, as of now, no conclusive evidence has confirmed a causal relationship. Presently, the WHO is undertaking a comprehensive health risk assessment, including other than cancer, of radio waves including frequency bands used for mobile telecommunications from 2023 onwards.

3. Effects of Static Electromagnetic Fields on Human Body

Among static electromagnetic fields [0 Hz (hertz)], static electric fields may cause discomfort and the perception of electric shock (pain) due to electric discharge. The strength of electric fields is estimated to be within the range of 10 to 45 kV/m (kilovolt per meter).

Concerning static magnetic fields, it is recognized that head movement within very strong static magnetic fields of magnetic flux density more than 2 to 4 T (tesla) may result in symptoms such as vertigo, nausea, metallic taste and phosphenes.

Regarding health effects of static electromagnetic fields, the WHO published its assessment findings in Fact sheet No.299 titled “Static Electric and Magnetic Fields”, concluding that “the carcinogenicity of static magnetic fields to humans is not at present classifiable.”

WHO Fact sheet No. 299 “Static Electric and Magnetic Fields”