A possible association between extremely low-frequency magnetic fields and the incidence of cancer has been examined in numerous epidemiological studies for more than 35 years. No evidence was observed in adults that long-term exposure to extremely low-frequency magnetic fields increases the risk of developing cancer (e.g. leukemia, breast cancer or brain tumor) (German Commission on Radiological Protection 2008). In contrast, in children, the results of epidemiological studies indicated an increased risk of developing childhood leukemia when exposed to magnetic flux densities of more than 0.3-0.4 µT. Based on these studies, the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) classified extremely low-frequency magnetic fields as class 2B "possibly carcinogenic to humans" (2002 and 2007). However, the evidence of epidemiological studies is limited due to methodical problems such as selection bias (c.f. background information on study types). Moreover, no underlying mechanism of action has been found to date, which could explain the development of leukemia due to weak magnetic fields. The results of these epidemiological studies could not be verified by animal studies, either (WHO 2007).
Childhood leukemia is a relatively rare disease (ca. 49.000 new cases per year worldwide, in Germany ca. 600 new cases per year). The risk factors of childhood leukemia are largely unknown. Residential exposure to magnetic flux densities of more than 0.3 µT is also very rare (applies only to 1-4% of children). External exposure sources (e.g. high-voltage power lines) contribute one third to the residential exposure and sources at home like household appliances add two thirds to the residential exposure. In 2007, WHO classified, as high priority projects (WHO 2007), pooled analyses including the recent epidemiological studies on childhood leukemia and magnetic fields, the development of transgenic animal models for examination of childhood leukemia with exposure to extremely low-frequency magnetic fields and the possibly co-carcinogenic effects of magnetic fields.
The German Commission on Radiological Protection (SSK) concluded in its recommendation from 2008 that there is, even after the evaluation of the newer scientific literature, no evidence of possible adverse health effects due to extremely low-frequency electric and magnetic fields which would be reliable enough to justify a change in the existing limit value regulation 26th BImSchV. Additionally, there is no sufficient proof from the analysis of the present scientific literature to recommend lower precautionary values, which would promise a quantifiable health effect. However, the German Commission on Radiological Protection acknowledges the need for further experimental and dosimetric research (German Commission on Radiological Protection 2008).
Current research is, for example, conducted within the European community project ARIMMORA (Advanced Research on Interaction Mechanisms of electroMagnetic exposures with Organisms for Risk Assessment), which is supported with the 7th Research Framework Program of the European Commission. The aim of the project is to scrutinize the possible mechanism for the development of cancer, especially childhood leukemia, by extremely low-frequency magnetic fields. This could be achieved by novel experimental and computer-based methods and improved cell- and animal-experimental studies under precisely defined exposure conditions. Research groups from Germany, Switzerland, France, Italy, Spain and Israel participate at this project (start: October 2011) (ARIMMORA).