Definitions

Non-ionizing electromagnetic fields are fields producing radiation with insufficient energy to ionize molecules or atoms and so do not release active and potentially damaging agents within cells (Figure 1 in 16.5). Electromagnetic fields surround us everywhere, there is the normal static natural magnetic field of the earth, electric fields in the air, heat radiation from ovens, the sun and light bulbs. Radio frequency fields come from power lines, cellular phone base stations, high frequency communication devices, radars, global position services and broadcasting signals. These electromagnetic fields have physical parameters as ionizing electromagnetic fields.

Limit values

The International Commission on Non-Ionizing Radiation Protection (ICNIRP) is an international, non-governmental organization that collects and reviews current scientific knowledge on electromagnetic fields and produces guidelines for exposure to such fields on a regular basis. Their guidelines differ for exposures to different frequencies of field. They are based on scientifically established health effects relevant for the different frequencies of field.

 

Field/ frequence

Recommended occupational exposure limit

Magnetic field

Electric field

B = magnetic flux density

microTesla (µT)

H = magnetic field Ampere/meter, (A/m)

Volt/meter (V/m)

Static magnetic field

200

 

 

50 Hz

500

 

10000

82-65 Hz

30.7

24.4

610

100 kHz

 

16

610

1 MHz

 

1.6

610

10-400 MHz

 

0.16

61

900 MHz

 

0.24

90

2-300 GHz

 

0.36

137

Health effects: scientific established

  • Induced currents: strong low frequency electric fields (> 10 kVolt/m) and powerful magnetic fields (>1000-10000 microTesla) can induce currents in the human body, which are powerful enough to cause nerve and muscle activation.
  • Thermal effects: electromagnetic fields contain energy which is deposited in the tissues. Heating due to this deposition is strongly connected to the frequency and power of the field and the volume and electromagnetic properties of the tissue which is being radiated. If heating occurs this can lead to cellular and tissue burns, damage to the retina and genotoxic damage to the cells.
  • Vulnerable groups: people with metal joint and other prostheses are more vulnerable for exposure to NIR, due to induced currents and magnetic effects. In addition is cardiac pacemakers may be vulnerable to incorrect triggering if they are in an area with exposures above given limits for these devices.

Health effects: controversial or not validated

There is no existing consistent scientific evidence of other adverse health effects caused by non-thermal exposure to electromagnetic fields. However, several studies have investigated this and several are still being conducted. These have conflicting findings, and the quality of exposure assessment is varying. These conflicting results and the limitations of methodologies used are one of the reasons why the question of health effects coming from non-thermal electromagnetic fields still is open for discussion.

There are two main health effects that have been discussed:

  • Environmental hypersensitivity attributed to electromagnetic fields.

This topic has been investigated several times in many different research environments. The studies generally have very good protocols and designs. These studies have not led to the presenting symptoms being classified as caused by electromagnetic fields.

  • Brain cancer caused by cellular phones

Some years ago the World Health Organization (WHO) classified radiofrequency electromagnetic fields as a possible cancer inducer in humans. This classification is mainly based on two large multi-centre studies, the Hardell study and the Interphone study. The studies were conducted on persons who used cellular phones in the 1980’s and 1990’s, most users had cellular phones with the GSM or NMT technologies. These were very different from the technology that is being used today in more recent GSM-, 3 G and 4 G mobile phones. Today’s technology emits considerably less radiation than the older phones. For example a new cellular phone using 3 G technology emits in the order of 0.01 – 1 Watt, while the old NMT technology could emit as much as 15 Watts. 

  • Interphone study.[14]

These is a case-control study mainly based on interviews of brain cancer patients and controls concerning cellular phone use. The combined results show a 1.5 times increased risk for glioma brain cancers among persons who used their phones for more than 10 hours per day and for a duration of more than 10 years.

  • Hardell study.[15]

This study was conducted in Sweden. It is interview based case-control study of brain cancer patients and controls. This study also concludes that there is an increased risk for glioma brain cancers among persons who have similar high levels of use as found in the Interphone study.

Several major reviews have been published on the current status of scientific knowledge about health risks from electromagnetic fields.[16] Their conclusions are similar:

There is no consistent evidence for any adverse health effect from exposure to electromagnetic fields below the thermal exposure limit. However, many of the studies that have been conducted have limitations and also many aspects have not yet been investigated, making a conclusion difficult to draw. 

Exposure in the maritime environment

On board vessels and in shore-based maritime installations most exposure to these fields comes from the communication and navigation devices on board the vessel and from surrounding vessels and in close proximity to large scale generating equipment. In addition it is important to remember the risk of electric shock from installations on board and the guidelines and safety rules concerning these. When monitoring fields on board vessels and in the maritime environment it is important to assess the actual exposure. Such measurements are relatively easy to conduct. Specialist firms and public institutions usually have the equipment and skills.

Especially when there are worries that potential overexposure incidents might have occurred, mapping of the actual exposure is very important. A proper exposure assessment and dose-estimate for the exposure will be important when answering workers’ questions on potential risks from the exposure. The frequency of exposure, amount of energy deposited and length of exposure will all determine the likelihood of health risks from exposure.

Treatment of those who may have been overexposed or may have concerns about this is individual and symptomatic, but some guidelines can be followed.  If possible try to get an assessment of the actual exposure before assessing individuals:

  • Proper information. What happened? In terms of type of exposure, duration in time – position of the exposed person. Were there any acute symptoms (heat sensation, tingling sensation, nausea etc.)? Has there been any development of the acute symptoms, or any new symptoms, since the exposure?
  • Medical history and clinical examination must be done. In the acute phase it is very important to look for skin burns or red markings in the skin. Also examination of the visual function and of the retina can be useful. Extensive eye-examination by specialist may be necessary.

There have been many incidents with overexposure to these fields. These have given us much information about possible symptoms and on health consequences arising from such exposures.

Damage has only been seen when the exposure has been sufficient to cause thermal effects, that is, the person exposed would normally would feel a temperature increase in the skin, and if the this exposure has been extreme, it causes much pain. There are a number of articles discussing this topic and providing helpful advice for such situations.[17]

Chronic exposure

Generally exposure to these fields is not large on board vessels and maritime installations. Some studies have investigated the field levels on board certain vessels. Two vessels in the Royal Norwegian Navy have been measured during normal activity using personal measurements. The results showed low levels of electric fields on board these vessels.[18] Also there have been investigations of the personnel working inside radio rooms on board vessels. The results are conflicting, and studies often lack exposure assessments.[19]

Acute exposure

In addition to the chronic exposure, acute exposures can also happen due to malfunctions in equipment or disregard of precautions. One example is an episode from the Barents Sea in the autumn of 2012. A Coastal Guard vessel was caught in the radar beam of a frigate during a military exercise. In the weeks following the incident personnel on board the Coastal Guard vessel became ill with diverse symptoms, ranging from difficulties in seeing, changes in sensation and in cognitive skills. A research project is currently taking place to map the different symptoms and the follow up of the personnel.

Type of exposure in the maritime environment

  • Natural solar ultraviolet radiation:

Outdoor work, normally recommended to not exceed 30 Joule/m2 during an eight hour work day if the worker is not protected. Can cause skin burns, and increases the risk of malignant melanoma and other skin cancers.

  • Low frequency electromagnetic fields and static magnetic fields:

Exist surrounding electric installations, can cause nerve activation and give uneasiness if the exposure is large.

  • Radio frequency electromagnetic fields: 

Produced by communication devices and radar facilities, the exposure is normally reduced through restrictions on the distance between emitting aerial and crew access areas, as well as safety guidelines on the operation of the installation. Large exposures can cause thermal damage to cells and tissues. 

  • Magnetic fluxes:

Produced in the vicinity to large scale generating equipment.

Laws and regulations

National governments regulate the use of and protection from these fields through national protective agencies, and base their regulations on the international guidelines given by WHO and the International Commission on Non-Ionizing Radiation Protection.

Skotte J. Exposure of radio officers to radio frequency radiation on Danish merchant ships. AmIndHygAssocJ. 1984;45(12):791-5.