Mobile Phones/Smartphones

Mobile phones are indispensable tools in modern daily life, and everyone carries a smartphone. Originally, mobile phones started becoming popular as portable phones, but mobile phones have evolved into highly multifunctional devices, with cameras, video viewing, cashless payments, and more.

1. Radio Waves from Mobile Phone/Smart Phone

Mobile phones use electromagnetic fields (radio waves) in the 700 MHz (megahertz) to several tens of GHz (gigahertz) range for communication. Radio waves in this frequency range carry a large amount of information and are used not only for mobile phone communication but also in a wide variety of communication and industrial equipment.

2. Effects of Radio Waves on Human Body

2.1 Scientifically Established Effects on Human Body (Short-Term Exposure Effects of High Levels of Radio Waves)

When human body is exposed to very strong radio waves, some of the energy is absorbed to the body and converted into heat, leading to an increase in body temperature. This phenomenon is known as the thermal effect.
If the intensity of the radio waves remains below a certain threshold, body temperature will not increase due to the human body’s thermoregulatory function, which maintains a constant body temperature through adjustments in blood flow, sweating, and other mechanisms.
The Specific Absorption Rate (SAR) is used as the index for assess the thermal effect. SAR quantifies the amount of energy absorbed by 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, with radio waves from mobile phone handsets, only specific parts of the body (such as the head) are locally exposed. As a result, the quantities of whole-body exposure and local exposure are separately evaluated using the indices of whole-body averaged SAR and local SAR, respectively.

2.2 Scientifically Unestablished Effects on Human Body (Long-Term Exposure Effects of Low Levels of Radio Waves)

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

3. Regulations on Radio Waves in Japan

The Ministry of Internal Affairs and Communications (MIC) has established radio waves protection guidelines as safety standards for the use of radio waves generated by mobile phone base stations, mobile phone/smart phone, and other sources. These guidelines include standard values for radio wave strength that are considered safe for the human body, as outlined in the Radio Law, Radio Law Enforcement Regulations, and Radio Equipment Regulations. Detailed information about the institutionalization of these radio wave protection standards is available on the MIC Radio Use Website.

3.1 Regulations on Radio Waves from Mobile Phone Base Stations

The strength of radio waves from mobile phone base stations is regulated by the whole-body average SAR. Because the antennas are made to designed to be directional to transmit radio waves farther, the strength tends to be higher at points several hundred meters away than near the base station. However, the strength at all points is much lower than the standard value specified in the radio wave protection guidelines (whole-body average SAR 0.08W/kg). Additionally, telecommunications carriers are required to implement fences or other measures to prevent the general public from easily entering areas very close to mobile phone base station antennas where the standard value might be exceeded.
According to a brochure from the MIC, radio waves are generally strongest at a distance of about 200 meters from a mobile phone base station, where the strength is approximately 1/1,000 of the standard value. Moreover, it has been found that the strength of radio waves from mobile phone base stations is low compared to that of TV and radio waves.

MIC brochure [only in Japanese]

3.2 Regulations on Mobile Phones/Smart Phones Radio Waves

The strength of radio waves from mobile phones/smart phones is regulated by local SAR. The MIC has established a limit (local SAR 2W/kg) in its radio wave protection guidelines to prevent thermal effects on the human body, ensuring that people are not exposed to radio waves strong enough to increase body temperature in their living environment. The local SAR for each mobile phone model can be checked on the website of each telecommunications carrier.

3.3 Regulations on Wireless LANs Radio Waves

Radio waves are also used for communication between wireless LAN access points and terminals such as PCs. All devices that generate radio waves, including wireless LANs, are regulated by the Radio Law, which is based on radio wave protection guidelines to ensure that the strength of radio waves does not exceed the standard value (whole-body average SAR of 0.08 W/kg).