Over the years, national and international experts and authorities have evaluated the research conducted. The most recent evaluation comes from the World Health Organization (WHO).
One or a few studies are not sufficient to establish whether magnetic fields pose a health risk. One of the reasons why it is so difficult is that statistical studies must go way back in time to obtain a sufficient amount of data. This in itself gives rise to uncertainty. Another reason is that national studies are based on relatively limited data material. Childhood leukaemia, for example, is a relatively rare disease, and only relatively few people are exposed to fairly strong magnetic fields.
In order for the result to be fairly certain, science demands that testing on animals and cells can be repeated with the same result in different laboratories. This has not been possible so far.
Over the years, a substantial number of national authorities and international organisations have at intervals prepared a status of the collective research results. The latest and most authoritative international evaluation of magnetic fields and health risks was published in 2007 by the World Health Organization (WHO). It is based on the work conducted by internationally recognised researchers over a period of 10 years, which reviewed existing research and provided new studies.
WHO is of the opinion that the research results for childhood leukaemia do not justify the setting of actual exposure limits for magnetic fields and instead recommends a precautionary approach.
In 1993, the Danish health authorities came down in favour of a precautionary approach, and even though much research has been conducted since then, the latest WHO recommendations do not as a whole differ very much from the ones presented by the Danish health authorities 15 years ago. In 2007, the Danish National Board of Health reviewed the most recent WHO publications and came to the conclusion that it is not necessary to change the previous recommendations.
Although it is not necessary to change the previous recommendations, much more is known about magnetic fields today. The most significant difference from previously is that today it is possible to say about more diseases that they do not appear to be linked with magnetic fields. Also, some of the earlier theories about the mechanism that supposedly make magnetic fields cause diseases such as, for example, cancer, can be refuted today. The most important questions revolve around childhood leukaemia. They aim to determine whether magnetic fields are the cause of the increased incidence of childhood leukaemia which demographic investigations have demonstrated, or whether other factors are to blame.