Electromagnetic Radiation And Adverse Health Effects

With wireless and mobile communication technologies on the rise - especially 5G - people are worried about electromagnetic radiation and their personal health. This blog presents the latest data on safety levels with respect to human exposure to electromagnetic radiation. In addition, the blog shows evidence why radiation from mobile communication base station antennas should not worry you.

Mobile communication base station antennas.

1. Radiation Frequency Spectrum

1.1 Ionizing vs. Non-Ionizing

Electromagnetic radiation can be divided into the following two types:

• Non-ionizing radiation. Wireless communication, television and radio broadcast, microwave oven, radar, infrared heating, visible light.

• Ionizing radiation. X-rays, gamma rays from radioactive decay, cosmic rays.

In the following part of the blog, we are only discussing non-ionizing electromagnetic radiation. Non-ionizing radiation has not enough energy to remove electrons from atoms or molecules. This means that non-ionizing radiation does not affect the structure of atoms and molecules. On the other hand, ionizing radiation has the ability to ionize atoms or molecules by detaching electrons from them, and therefore, ionizing radiation can cause cancer.

The picture below shows how the frequency spectrum can be divided into non-ionizing radiation (f<3PHz, λ>1mm) and ionizing radiation (f>3PHz, λ<1mm).

Frequency spectrum and primary effects on the human body.

1.2 Health Effects vs. Frequency

Scientific data on the effect of exposure show, that time-varying electromagnetic fields (EMF) have two primary effects, depending on the frequency f [Hz] of the time-varying EMF [1]:

• 1Hz to 100KHz. Nerve stimulation is the primary effect of exposure.

• 100kHz to 10MHz. Transition region, where both, nerve stimulation and heating occur.

• 10MHz to 300GHz. Heating is the primary effect of exposure.

Mobile communication uses EMF of frequencies from around 0.4GHz (GSM-T) up to circa 71GHz (5G). Thus, in the following part of the blog, we only discuss exposure limits of the frequency range from 10MHz to 300GHz. This means, regarding health effects, we only focus on the heating effect of EMFs.

2. Adverse Health Effects f >10MHz

The health effects of electromagnetic radiation on the human body are still being studied. So far, based on scientific research, the only adverse health effect of electromagnetic radiation with frequencies f>10MHz is heating [3].

2.1 Field-Strength vs. Distance

In the following, we distinguish between whole-body adverse health effects and head/torso adverse health effects. And that is the reason for this distinction:

• Radiation from mobile station antenna = affects whole-body. The radiation from mobile communication base station antennas (e.g. on buildings or high masts) has an effect on the whole-body and does not have a specific local effect on the human body.

• Radiation from mobile phone = affects body locally. The radiation from a nearby mobile communication device (e.g. a mobile phone, hold close to the head) has a locally limited effect on the body.

The rapid decrease of field-strength E [V/m] with distance d [m] from a WiFi router [6].

But why does the radiation from your mobile phone primarily affect your head and the radiation from a mobile communication antenna on a building your whole body? Because of the rapid decrease of the field strength [V/m] with increasing distance from any electromagnetic radiation source. The picture above shows this fact based on the radiation of a Wireless Local Area Network (WLAN) router (WiFi router).

2.2 Whole-Body Adverse Health Effects

2.2.1 Minimum Whole-Body SAR [W/kg] For Adverse Health Effects

Studies in animals, including non-human primates, have consistently demonstrated a threshold effect for the occurrence of behavioral changes (decrease in food-reinforced memory performance) and alterations. According to the International Commission on Non-Ionizing Radiation Protection (ICNIRP), these effects occur with exposures to radiofrequency EMFs at a whole-body average Specific Absorption Rate SAR of >5W/kg for rats, and a whole-body average SAR>4W/kg (averaged over 30min) for non-human primates, which correspond to increases in body core temperatures of approximately 1°C [1][4].

For a SAR of <4W/kg, there is no scientific evidence that electromagnetic fields with frequencies of 10MHz to 300GHz could increase the probability of cancer, electrohypersensitivity, infertility, or other health effects [3].

2.2.2 Maximum Whole-Body SAR [W/kg] For Preventing Adverse Health Effects

From the chapter above, we know that the maximum SAR for a whole body, which is exposed to an electromagnetic field (100kHz to 300GHz), should be <4W/kg. Now, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) proposes the following safety margins for workers and the general public:

• Safety margin = 10 for workers. SAR<0.4W/kg for occupational exposure.

• Safety margin = 50 for general public. SAR<0.08W/kg for general public exposure.

The basic restriction values [W/kg] for EMF exposure from 100kHz to 300GHz and whole-body are summarized in the table below. The World Health Organization (WHO) does also recognize the ICNIRP basic restrictions [5].

Whole-body basic restriction and limit levels of electromagnetic radiation.

2.3 Head/Torso Adverse Health Effects

2.3.1 Minimum Head/Torso SAR [W/kg] For Adverse Health Effects

In addition to whole-body core temperature, excessive localized heating can cause pain and thermal damage. The present ICNIRP guidelines treat radiofrequency EMF exposure that results in local temperatures of 41°C or greater as potentially harmful [1]. Based on scientific studies, the ICNIRP came to the following minimum SAR [W/kg] and radiation power density S [W/m^2] levels, above which health effects in the form of local body temperature increase for head and torso of up to 41°C could occur [1]:

• SAR = 20W/kg for frequencies of 100kHz to 6GHz and head/torso

• Power density = 200W/m^2 for frequencies of 6GHz to 300GHz and head/torso

There basic restriction values above are primarily relevant for mobile phones because mobile phones are used close to the body (head).

2.3.2 Maximum Head/Torso SAR [W/kg] For Preventing Adverse Health Effects

From the chapter above, we know the maximum SAR [W/kg] and power density S [W/m^2] values, called basic restriction values, for head and torso. Now, the ICNIRP proposed the following safety margins for workers and the general public:

• Safety margin = 2 for workers.

  • 100kHz to 6GHz: SAR<20W/kg for head/torso and occupational exposure.

  • 6GHz to 300GHz: S<100W/m^2 for head/torso and occupational exposure.

• Safety margin = 10 for the general public.

  • 100kHz to 6GHz: SAR<2W/kg for head/torso and general public exposure.

  • 6GHz to 300GHz: S<20W/m^2 for head/torso and occupational exposure.

The maximum SAR value of 2W/kg is especially important for mobile phones because the vast majority of mobile communications happen at frequencies below 6GHz. The basic restriction values [W/kg] for EMF exposure from 100kHz to 300GHz are and head/torso summarized in the table below. The World Health Organization (WHO) does also recognize the ICNIRP basic restrictions [5].

Head and torso basic restriction and limit levels of electromagnetic radiation.

3. Exposure Reference Levels (ERL)

The basic restrictions, given in SAR [W/kg], refer to EMFs inside human bodies and are rather difficult to measure. Therefore, some effort was made to convert the basic restrictions in [W/kg] to reference levels in the form of electric fields [V/m], called the Exposure Reference Levels (ERLs), which can be measured in the environment with standard equipment. In this section, we focus only on exposure limits for radiation from mobile communication base station antennas and not for mobile phones. This is because, for mobile phones, there is usually not the ERL specified, but the SAR value, which should be <2W/kg, according to ICNIRP.

The graph below compares the health effect limits, the exposure reference levels (ERLs) - defined by the ICNIRP [1] with a safety margin - and some real-world measurement data from 4G and 5G antennas (maximum and mean values) [6][8][9][10]. It must be mentioned again, that this is valid for radiation in the far-field (from mobile communication base station antennas) and when considering adverse health effects for the whole body (not locally on head/torso). It can clearly be seen, that even the maximum real-world measurement data of electromagnetic radiation in public places are far below the radiation intensity limits where adverse health effects occur.

Electric field strength E [V/m] comparison: heath effect levels vs. exposure limits vs. real-world measurement data from mobile communication base stations [6][8][9][10].

The graph above compares the health effect levels, exposure limits, and real-world measurement data, for the electric field strength E [V/m]. In the far-field of an antenna, the power density S [W/m^2] of the mobile communication radiation can be calculated as S = E^2/η0=E^2/377Ohm. η0 =377Ohm is the intrinsic impedance of the vacuum. Therefore, it is possible to plot the health levels, exposure limits, and real-world measurement data for the power density S [W/m^2] vs. frequency f [Hz]. This is done in the plot below, where it gets even clearer that the radiation intensity from mobile communication base station antennas is far away from the adverse health effect limits. To be more explicit, the maximum measured real-word radiation power density from a mobile communication antenna is between 1000 and 5000 times smaller than the limits for adverse health effects (100W/m^2/0.1W/m^2 = 1000, 50W/m^2/0.1W/m^2 = 5000).

Power density S [W/m^2] comparison: heath effect levels vs. exposure limits vs. real-world measurement data from mobile communication base stations [6][8][9].

4. Mobile Phone vs. Base Station Antenna

The chapters above show that the safety margin for electromagnetic radiation, which affects the whole body, is more stringent than the safety margin for head/torso:

• Whole-body safety margin for basic restriction SAR [W/kg] in the general public: 50

• Head/torso safety margin for basic restriction SAR [W/kg] in the general public: 10

Now, remember that the whole-body basic restriction SAR [W/kg] values are relevant for mobile base station antennas (on buildings and towers) and that the local head/torso basic restriction SAR [W/kg] values are relevant for mobile phones. This fact, that the safety margin for whole-body - and therefore for mobile base station antennas - is larger than for head/torso, tells you that you should be more worried about the radiation from your mobile phone than from the mobile base station antenna.

"The primary source of radiation on the human body is one's own mobile phone." - Reto Keller

In addition, a study from Switzerland showed, that around 90% of the radiation does come from one's own wireless end device (e.g. the mobile phone) [7]. It is worst if the connection from the mobile phone to the mobile base station antenna (on buildings and towers) is poor. In such a case, the mobile phone has to radiate with full power. In case of a good connection, the mobile phone radiates with less power in order to reduce power consumption and therefore to increase battery life.

The graph below shows the average exposure to electromagnetic radiation for different locations and daily situations [6]. The radiation close to a mobile phone or a cordless phone is the most intensive.

Radiation exposure at different locations and in different situations [6].

In case you own a mobile phone, the radiation from mobile base station antennas on buildings and towers play only a minor role in daily exposure to electromagnetic radiation. However, if you don't own a mobile or cordless phone, the radiation from mobile base station antennas and mobile phones of other people are the primary source of daily exposure to electromagnetic radiation.

6. EMC and Exposure Reference Levels

This website is all about Electromagnetic Compatibility (EMC). So lets' compare the most common radiated immunity test levels and the most common radiated emission limits with the exposure limits (ERLs) for electromagnetic fields in the general public.

6.1. EMC Immunity Levels vs. Exposure Limits vs. Real-World Measurement Data

The EMC standard IEC 61000-4-3 is the most commonly applied EMC standard for radiated immunity. IEC 61000-4-3 defines four immunity test levels (from 1 V/m up to 30V/m). Product standards, e.g. for household appliances or medical devices, refer to the IEC 61000-4-3 standard and define the required immunity test level for that type of product, e.g. 1 (1V/m), 2 (3V/m), 3 (10V/m) or 4 (30V/m). The graph below compares the whole-body exposure limits (ERLs) defined by ICNIRP for public areas, the immunity test levels of IEC 61000-4-3 and some real-world measurement data. It can be seen that an immunity test level of 10V/m is well above the maximum measured field strength in public places (6V/m) and therefore, 10V/m seems to be a reasonable test level for electronic devices.

Electric field strength E [V/m] comparison: exposure limits vs. IEC 61000-4-3 immunity test levels vs. real-world measurement data from mobile communication base stations [6][8][9].

6.2 EMC Emission Limits vs. Exposure Limits

CISPR 11 and CISPR 32 are the most common EMC emission standards. CISPR 11 does only specify radiated emission limits from 30MHz to 1000MHz, whereas CISPR 32 specifies the limits from 30MHz to 6000MHz. The radiated emission limits for CISPR 32 are given in the two graphs below. The maximum radiated emission limit in CISPR 32 is given for the frequency range from 3GHz to 6GHz with a peak value of 80dBuV/m = 0.01V/m at a distance of 3m. This corresponds to 0.000000265W/m^2. The exposure limit at 6GHz is 10W/m^2. This means that the maximum unintended radiated power from an electronic device at a distance of 3m from this device is more than 37 million times smaller than the exposure limit (10W/m^2/0.000000265W/m^2 = 37.7Mio).

CISPR 32 radiated emission limits from 30MHz to 1000MHz.

CISPR 32 radiated emission limits from 1000MHz to 6000MHz.

7. Conclusion

We can conclude with the following points:

• Radiation from mobile base station antennas should not worry you. Radiation power from mobile communication base station antennas is more than 1000 to 5000 times smaller than the limits for adverse health effects.

• Your mobile phone is worse than every mobile base station phone antenna. Around 90% of the non-ionizing radiation that the average user is exposed to comes from its own end device (e.g. mobile phone) and not from the mobile phone antenna. Since electromagnetic radiation decreases rapidly with the distance from the transmitter (base station antenna, mobile phone), you should use a headset when making phone calls and not press the mobile phone at your head. The radiated power from the mobile phone decreases the better the mobile phone reception is. It is therefore better to make calls in places where the reception is good.

• Exposure limits protect from adverse health effects. The emission limit for electromagnetic radiation in public areas is at least 50 times lower than the threshold above which scientifically proven adverse health effects occur. Many countries apply an even larger safety margin than 50.

• 10V/m is a reasonable test level for radiated EMC immunity tests. The immunity test level of 10V/m (according to IEC 61000-4-3) is bigger than the expected maximum field strength in public areas of cities (6V/m). Thus, testing the radiated immunity of a product for 10V/m is expected to lead to robust product performance, even in places with exposure to intensive mobile communication radiation from mobile base stations.

• Radiated emission from electronic devices without wireless communication is negligible. The radiated emission, from electronic devices without wireless communication, is over 37Mio times smaller than the exposure limit for non-ionizing radiation.

The flow diagram below summarizes the maximum SAR [W/kg] and the maximum exposure levels in [V/m] for radiation on the whole body and local on the head and torso.

Electromagnetic radiation of mobile communication applications and their maximum exposure levels [1][2][3]..

About the Author

Reto Keller works as a principal electronic development engineer and is president of the Academy of EMC.

Author, Reto Keller, President Academy of EMC.

References

[1]ICNIRP. ICNIRP GUIDELINES FOR LIMITING EXPOSURE TO ELECTROMAGNETIC FIELDS (100 KHZ TO 300 GHZ). March 2020.

[2]IEEE Standard for Safety Levels with Respect to Human Exposure to Electric, Magnetic, and Electromagnetic Fields, 0 Hz to 300 GHz, in IEEE Std C95.1-2019 (Revision of IEEE Std C95.1-2005/ Incorporates IEEE Std C95.1-2019/Cor 1-2019), vol., no., pp.1-312, 4 Oct. 2019, doi: 10.1109/IEEESTD.2019.8859679.

[3]https://www.icnirp.org/en/publications/article/rf-guidelines-2020.html [09-Dec-2022]

[4]https://www.canada.ca/en/health-canada/services/publications/health-risks-safety/limits-human-exposure-radiofrequency-electromagnetic-energy-range-3-300.html [09-Dec-2022]

[5]https://www.who.int/teams/environment-climate-change-and-health/radiation-and-health/protection-norms [09-Dec-2022]

[6]https://cdn.beobachter.ch/sites/default/files/fileadmin/dateien/pdf/Infografiken/Infografik_Elektrosmog_BeoN_02-10.pdf [17-Dec-2022]

[7]https://www.newsd.admin.ch/newsd/message/attachments/59384.pdf [17-Dec-2022]

[8]https://www.spandidos-publications.com/10.3892/wasj.2022.157 [17-Dec-2022]

[9]https://www.imec-int.com/en/articles/massive-mimo-emf-exposure-estimation-tools-models-and-initial-measurements [17-Dec-2022]

[10] https://www.bakom.admin.ch/dam/bakom/de/dokumente/bakom/telekommunikation/Technologie/5G/Elektrische%20Feldst%C3%A4rken%20im%20Wirkbereich%20adaptiver%20und%20konventioneller%20Mobilfunkantennen.pdf.download.pdf/elektrische_feldstaerken_im_wirkbereich_adaptaiver_und_konventioneller_mobilfunkantennen.pdf [23-Dec-2022]