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EMF and cancer FAQs

 

Why is there concern about a possible risk of cancer from exposure to ELF electric and magnetic fields

The concern about the possible role of electromagnetic fields in cancer has its origin in an epidemiological study carried out in 1979 in the USA by Wertheimer and Leeper. In this study a statistical correlation between the incidence of childhood leukaemia and proximity to electricity supply wiring was demonstrated. The study prompted many other epidemiological studies to examine cancer incidence and exposure to electromagnetic fields. Since then, extensive programmes of experimental and epidemiological research have been undertaken to search for scientific evidence of possible health effects. Some of these studies were examined in earlier reports by AGNIR and more recent studies are reviewed in the present report. Most studies have been concerned with exposure to magnetic fields.

 

How does AGNIR assess the research on the possible risk of cancer from exposure to ELF electric and magnetic fields?

The AGNIR assessment is based mostly on the information available from experimental studies on tissues, living cells and animals, and human volunteer- and epidemiological studies. The epidemiology is normally used to demonstrate whether an association exists between exposure and disease. The interpretation of an association, such as whether it reflects causality, also depends on other factors such as the quality of the research or whether findings from other scientific disciplines are supportive or not. Biological plausibility refers to whether an association is supported by scientific research other than epidemiology. For instance an epidemiological association is more likely to be interpreted as causal if the experimental biology shows a strong dose-response relationship or demonstrates a mechanism for damage. In reviewing the laboratory evidence it is also necessary to take experimental design into account.

 

What is the main conclusion of the recent report from AGNIR?

AGNIR concluded:

Laboratory experiments have provided no good evidence that ELF electromagnetic fields are capable of producing cancer, nor do human epidemiological studies suggest that they cause cancer in general. There is however some epidemiological evidence that prolonged exposure to higher levels of power frequency magnetic fields, is associated with a small risk of leukaemia in children. In practice, such levels of exposure are seldom encountered by the general public in the UK. In the absence of clear evidence of a carcinogenic effect in adults, or of a plausible explanation from experiments on animals or isolated cells, the epidemiological evidence is currently not strong enough to justify the firm conclusion that such fields cause leukaemia in children. Unless, however, further research indicates that the finding is due to chance or some currently unrecognised artefact, the possibility remains that intense and prolonged exposures to magnetic fields can increase the risk of leukaemia in children.
(AGNIR Report, page 164, paragraph 15.)

 

How do the conclusions of the present report differ from those expressed previously by AGNIR?

In general there have been considerable advances in methods for assessing exposure, both in the case of experimental studies and in the epidemiological studies. The most recent review concludes that the epidemiological studies, in particular the pooled analysis of Ahlbom et al., have provided a firmer base for the possibility of a risk of leukaemia in children, but at higher average exposures (0.4 µT and above) than originally thought (0.2 µT and above). The evidence, however, is not conclusive (page 163, paragraph 13) and chance, bias and confounding may explain some of the more recent results. The conclusions about the experimental studies are similar to those expressed previously by AGNIR – they do not establish any biologically plausible mechanism whereby carcinogenic processes can be influenced by exposure to low levels of electromagnetic fields.

 

How many studies did AGNIR review in coming to these conclusions and how were they selected?

AGNIR referred to approximately 300 studies in the present report. The studies are mainly published in the peer-review scientific literature, that is studies normally in prominent research journals. Focusing on the peer-review studies has provided a firm scientific basis from which to draw conclusions. Included amongst those studies are the pooled epidemiological study analyses that were published in 2000.

 

What is the view of AGNIR on the experimental studies?

The AGNIR view is that a large number of cellular and animal studies have been published since the earlier reports. Cellular studies have played an important role in the early identification of chemicals and other agents to which humans may be exposed and which have the potential to play a part in the causation of cancer. At the cellular level, there is no clear evidence that exposure to power frequency EMF at levels likely to be encountered can affect biological processes that are implicated in causing cancer. Medium- and long-term animal studies have examined tumour incidence after exposure either to electromagnetic fields alone or following application of known carcinogens and tumour promoters. Overall no convincing evidence was seen from a review of a large number of animal studies to support the hypothesis that exposure to power frequency electromagnetic fields increases the risk of cancer.

 

What is the view of AGNIR on the possible risk of residential exposure to power frequency EMF in the UK?

The AGNIR view is that recent large and well-conducted studies have provided better evidence than was available in the past on childhood leukaemia and exposure to EMF. Taken together they suggest average exposures of 0.4 µT or more are associated with a doubling of the risk of leukaemia in children under 15 years of age. The evidence is however, not conclusive. In relation to adults AGNIR says that there is no reason to believe that residential exposure to EMF is involved in the development of cancer.

 

What is the view of AGNIR on the possible risk of occupational exposure to power frequency EMF?

The AGNIR view is that studies of occupationally exposed populations may have greater potential to detect any adverse effects because they can include groups exposed at much higher levels than members of the public. The evidence is at present conflicting even in the most powerful of the studies. Excess risks, where they exist, are principally restricted to leukaemia and brain cancer. Although recently published studies are in the main methodologically sound and some have considerable statistical power, causal relationships between occupational EMF exposure and cancer incidence are not established. AGNIR recommends that more occupational studies should be carried out where exposures are high as they have greater potential to detect any effects.

 

Does the AGNIR review address any other potential health effects?

No, the current AGNIR report is only concerned with possible effects on cancer.

 

Why is there little mention of electric fields, which have been reported widely in the media?

There is little mention of electric fields in the AGNIR report because little research has been done on them. Most of the EMF research has been concerned with exposure to magnetic fields. Where electric field information was available, for instance in occupational epidemiology or in the recent publications on the possible influence of corona ions, AGNIR has taken this into account.

A pilot study conducted as part of the UK Childhood Cancer Study (UKCCS) has provided no support for the hypothesis that residential exposure to extremely low frequency electric fields is associated with childhood cancer, either by disease category or in total. NRPB issued a statement when the study was published.

What does AGNIR and the HPA recommend?

The Board of NRPB has supported the view of AGNIR. AGNIR and the Board of NRPB considered that residential epidemiological studies in the UK would be unable to provide any better information. These views have been adopted by the Board of the Health Protection Agency.  The low levels of exposure generally in the UK do not provide a population that is large enough to detect any effect on childhood leukaemia incidence at average exposures at or above 0.4 µT. More conclusive results may come from residential studies in other countries where exposures may be higher as a consequence of differences in the electricity supply and distribution systems. International collaboration might help to explain the observed association at higher levels of exposure with an increase in the leukaemia risk in children. Further information is needed on any factors that may result in bias or confounding in the published residential studies. In the UK the factors that result in high levels of residential exposure to magnetic fields need to be better understood, and this may help to identify ways to reduce exposures. There is also a need for epidemiological studies on groups that are occupationally exposed since the higher exposures encountered in some industries offer greater opportunity to identify potential health effects.

 

What will be the future work of AGNIR in relation to ELF exposure?

The future work of AGNIR will be to continue to keep the results of more recent studies related to health effects and ELF electromagnetic field exposure under review, and report as necessary.

 

Does Residential Exposure to Power Frequency Electromagnetic Fields Cause Cancer?

The residential epidemiology has suggested that there may be a small risk related to leukaemia in children and young persons and in particular to those exposed at levels of average domestic exposure to magnetic fields at or above 0.4 µT (400 nT). However the evidence is inconclusive. The epidemiological association may be due to chance, confounding factors or some unrecognised artefact related to the way the data have been collected. The review of experimental studies gives no clear support for a causal relationship between exposure to ELF EMF and cancer. AGNIR also concluded that there is no reason to believe that residential exposure to EMF is involved in the development of cancer in adults, and in particular of leukaemia or brain cancer.


Last reviewed: 8 September 2008