Extremely low frequency electromagnetic fields

The possible health effects of extremely low frequency electromagnetic fields have been studied for several decades, especially since the publication in 1979 of an epidemiological study in Colorado, USA (Wertheimer and Leeper, 1979), which found that children living in homes near high-voltage power grids were more likely to develop cancer.

Since then, several studies have been published around the world, from both an epidemiological perspective and regarding the effects of electromagnetic fields both in vitro and in vivo. Although several studies have found statistical associations between exposure to ELF electromagnetic fields and childhood leukaemia, no relationship of cause and effect has been clearly identified. The degree of uncertainty that still surrounds the issue of the health effects of extremely low frequency fields, especially over the long term, is still a question of public concern and debate, focusing particularly on power grids and their components. The fact that science has been unable to demonstrate that there is no health effect linked to exposure to ELF electromagnetic radiation, and the regular publication of studies whose results are sometimes difficult to interpret, only contribute to the general uncertainty and concern.

In 2002, the International Agency for Research on Cancer (IARC) placed ELF electromagnetic fields in Category 2B (possibly carcinogenic to humans), as a result of persistent uncertainties related to epidemiological studies suggesting an association between exposure to these fields and an excess risk of childhood leukaemia. This classification was a change in direction for risk assessments on this subject.

Since the publication in 2004 of a report submitted to the Directorate General for Health (DGS), other data concerning expert appraisals have appeared around the world. The WHO and Europe’s Scenihr are two of the authorities that have published their scientific positions on this question of possible health effects of ELF electromagnetic fields. In France, recent or current work on the subject has mostly concerned improving techniques for measuring exposure and the way it should be taken into account in epidemiological studies.

The work of the Agency

In 2008, the Ministries of Health, the Environment and Labour formally requested the Agency to carry out an expert appraisal concerning extremely low frequency electromagnetic fields. They especially asked the Agency to produce a summary of the findings of international expert appraisals and to issue recommendations for improving the quantification of population exposure to ELF fields.

The analysis of the literature carried out by the Agency shows that knowledge of human exposure to low frequency electromagnetic fields has progressed over the last few years. Nevertheless, although more is known about the sources responsible for these emissions, and despite the metrological instruments available today being capable of simulating the exposure caused, for example, by overhead power lines, there is still little published material on exposure.

The work of the Agency also shows that the short-term effects of ELF electromagnetic fields are known and well documented; exposure limits (100 µT for a magnetic field at 50 Hz, for the public) can provide protection.

Regarding potential long-term effects, there is notable convergence between the different international expert assessments (conducted by organisations, groups of experts or research groups). Various studies have observed a statistical association between exposure to ELF electromagnetic fields and childhood leukaemia. The studies in question even show good mutual consistency, statistically significant for residential exposure averaged over 24 hours, to electromagnetic fields at levels greater than 0.2 or 0.4 µT, depending on the different studies. However, to date, the studies carried out to determine a biological mechanism have reached no convincing conclusion. They have mostly been performed on animals or in human cellular systems in vitro.

Based on these data, in 2002 the IARC classified magnetic fields at frequencies of 50/60 Hz as possibly carcinogenic to humans (Category 2B).

This ongoing inability to identify a mechanism for biological action is an obstacle to the comprehension of the issues raised by the results of the epidemiological studies. This complex situation is a reason for encouraging the adoption of more precise epidemiological analytical techniques for improved characterisation of exposure.

 In 2013, the Agency was also asked to expand scientific knowledge on the consequences of ELF electromagnetic fields on animal health and zootechnical performance. The lack of bibliographic data assessing the exposure of livestock to electromagnetic fields incited ANSES to launch a campaign for measuring electrical and magnetic fields in the environment in a sample of thirty livestock farms, both near high-voltage power lines and otherwise. This study, while it is not representative of all French farm situations, made it possible to draw initial conclusions on the average levels found in fields in typical farm environments by identifying the sources of these fields. The magnetic field levels measured underneath high-voltage electrical power lines remained low (between 0.01 and 7.59 µT) and the electrical fields were around 46 to 5 060 V/m. The levels in livestock buildings were lower (< 3 µT and 43 V/m). While sources inside farms can generate fields reaching 25 µT near certain types of equipment (electrical cabinets in particular), animals were not directly exposed to these. A literature review showed that although effects have been observed on rare occasions in animals (deterioration of cognitive function in laboratory animals (exposure of > 100 µT), possible reduced milk production and milk-fat levels, and increased ingestion in dairy cows (magnetic fields of 30 µT for 30 days), etc.), it remains difficult to assess the direct health effects of extremely low frequency electromagnetic fields on livestock.

Recommendations

Based on these findings, the Agency recommends resuming or continuing the epidemiological studies based on a robust description of exposure to ELF electromagnetic fields, especially with the use of new techniques for measuring individual exposure.

The Agency also recommends reinforcing the research effort into the possible causes of childhood leukaemia. Beyond this, research into other potential effects of these fields should also be encouraged.

Lastly, studies are necessary that target workers exposed at higher doses. The Agency also advises associating local residents in studies to characterise exposure, by involving them in the definition of the objectives and informing them of the results.

In the meantime, the Agency recommends that no new establishments for young children (schools or kindergartens) be built or adapted in close proximity to very high voltage power lines, and that no new power lines should be installed over such establishments.