Ionizing electromagnetic fields are fields producing radiation with sufficient energy to cause ionization of molecules or atoms which result in the release of active and potentially damaging agents within cells.

Ionizing radiation is divided into x-rays and γ-rays based on the energy of the rays (Figure 1). Ionizing radiation is mainly described in terms of:

- The number of emitted particles:     Becquerel = 1 disintegrated atom per second

- The effect of the radiation:              Gray = 1 Joule absorbed energy per kilogram

- The effective dose:                        Sievert = Gray  x the tissue factor*.

* The tissue factor is a measure of the potential of a particular form of ionising radiation to cause tissue damage.

Exposures can arise from natural sources, such as radioactive materials in the soil and from cosmic sources. Workers can also be exposed to radiation from sources that result from human activities.













Figure 1. The spectrum of electo-magnetic radiation

Limit values

The International Commission on Radiation Protection (ICRP) 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. These guidelines are used by the World Health Organization (WHO) and by the most governmental authorities. To assess the levels in the different possible occupations the workers can wear a personal dosimeter. All areas with exposures between 1 – 6 mSievert per year are defined normally as a supervised and controlled area. All persons working in such areas are required to wear personal dosimetry. 


Type of exposure

Recommended occupational exposure limit

mSievert per year

Whole body


Equivalent dose to skin, hands, feet


Equivalent dose to lens of eye


 Table 1.  Recommended dose limits. Statens strålevern.[11] 


Figure 2:  Ionising radiation risks. modified by Ole Jacob Møllerløkken                              

Health effects

Exposure to ionizing radiation can occur from external sources or internally (swallowing, breathing or contamination of wounds with materials that emit ionising radiation). The health effects associated with exposure to ionizing radiation will vary depending on the total amount of energy absorbed, the time period, the dose rate and the particular organ exposed (Figure 2). Ionizing radiation affects individuals by depositing energy in the body which can damage cells or change the cell’s chemical balance. The tissues that have a high rate of regenerating are most vulnerable to radiation.

Small doses (whole body exposure < 0.1 Gray)

  • Local acute radiation injury in the intestine will give diarrhoea, constipation, haemorrhages and pain
  • Cataract
  • Permanently or temporarily sterility
  • Cancer induced by ionizing radiation

Different forms of cancer have been identified where radiation has been found to be a contributing cause. In common with other causes of cancer these effects also have a relatively long latency time, often10 – 20 years and more.

  • Leukaemia (findings from Hiroshima and Nagasaki)
  • Breast (findings from women treated for tuberculosis and monitored with very many x-rays to follow the development)
  • Liver (findings after use of radioactive medications)
  • Bone (findings in workers who ingested radioactive paint in their work).
  • Thyroid (findings from the Chernobyl accident)

Large doses (whole body exposure exceeding 1 – 2 Gray).  With increasing dose of exposure failure of the immune system occurs, with a duration depending on the level of exposure. Survival has occurred up to a dose of 4-5 Gray, but doses exceeding this have not been seen to be survivable. Experience from such exposures has mainly been gathered during war and from accidents.

The acute radiation syndrome:depending on the radiation dose there may be outer signs from the radiation, if the radiation is external. The exposed area can have erythema, oedema, dry or wet desquamation, blisters and sometimes necrosis which can be painful. Ionizing radiation in large doses has an immediate effect on the rapid regenerating cells of the human body, typically immune cells, blood cells, epithelial cells. The influence and destruction of these cells leads to haemorrhages, diarrhoea and vomiting which leads to an unbalanced liquid-balance in the body. In addition, because of an increased susceptibility for infection, this can be lethal when the immune system is not functional. The syndrome is characterized by the following:

  • The prodromal phase:       Nausea, vomiting, tiredness, fever and diarrhoea.
  • The latency period:           This period is of varying length.
  • The sickness phase:          Infections, hemorrhages and gastrointestinal symptoms is increasing due to the lack of blood cells and other rapid regenerating cells.

Exposure in the maritime environment

On vessels, ionizing radiation exists on nuclear powered vessels, vessels transporting nuclear materials, in some gauges and fire detection systems and when vessels are accidental contaminated, as with the Fukushima nuclear power station release in 2011. Exposures may also occur with certain cargoes, see  chapter 16. 7: Naturally Occurring Radioactive Material (NORM) in oil & gas shipping.

Guidance on prevention and on risks as well as on on how to assess and treat personnel who experience overexposure or contamination is complicated and depends on numerous factors. The Department of the Navy, Bureau of Medicine and Surgery in Washington U.S. have made an extensive guideline on radiation health protection, which can be useful for additional information and for health and safety work.[12] This manual includes information on how workers should be followed up prior to, during and after service, which include potential exposure to ionizing radiation. It includes recommendations on standardised medical testing for use before, during and after service, and also on the tests to be performed in case of any excess exposures, such as after accidental radiation releases. It also has sections on administrative follow up and on the importance of full documentation of findings.

The same department has also produced guidance on the evaluation and treatment of irradiated or contaminated personnel.[13] In this guideline they provide protocols for initial exposure assessment, management and treatment of individuals who are irradiated or externally or internally radioactively contaminated. In addition it also includes guidelines for treatment of potentially contaminated personnel and materials.

The following principles apply to the treatment of radiation-exposed personnel:

  • Radiation does not rapidly produce life-threatening symptoms
  • Normally does a radiated person not pose any risk for the helping personnel, but if there is suspicion of massive contamination or exposure protective garments incorporating lead shielding can be used
  • Do not touch any unidentified objects that the patient/ or contaminated personnel has. Leave such objects for identification by a radiation specialist
  • Move the patient and cleaning personnel to a room free of unidentified objects
  • In case of suspected contamination, isolation procedures must be initiated

Laws and regulations

 National governments regulate the use of and protection from this type of radiation through very strict guidelines. The regulations are based on the international guidelines given by WHO and the International Commission on Radiological Protection.