Non-ionizing radiation, discussed here, is associated with two major potential hazards: electrical and biological. Additionally, induced electric current caused by radiation can generate sparks and create a fire or explosive hazard.
The oscillating electric and magnetic fields in electromagnetic radiation will induce an electric current in any conductor through which it passes. Strong radiation can induce current capable of delivering an electric shock to persons or animals. It can also overload and destroy electrical equipment.
Extremely high power electromagnetic radiation can cause electric currents strong enough to create sparks when an induced voltage exceeds the breakdown voltage of the surrounding medium (e.g. air). These sparks can then ignite flammable materials or gases, possibly leading to an explosion. This can be a particular hazard in the vicinity of explosives or pyrotechnics, since an electrical overload might ignite them. This risk is commonly referred to as RadHaz or HERO (Hazards of Electromagnetic Radiation to Ordnance).
This heating effect varies with the frequency of the electromagnetic energy. The eyes are particularly vulnerable to RF energy in the microwave range, and prolonged exposure to microwaves can lead to cataracts. Each frequency in the electromagnetic spectrum is absorbed by living tissue at a different rate, called the specific absorption rate or SAR, which has units of watts per kilogram (W/kg). The IEEE and many national governments have established safety limits for exposure to various frequencies of electromagnetic energy based on SAR.
There are publications which support the existence of complex biological effects of weaker non-thermal electromagnetic fields (see Bioelectromagnetics), including weak ELF magnetic fields and modulated RF and microwave fields. Fundamental mechanisms of the interaction between biological material and electromagnetic fields at non-thermal levels are not fully understood.
The definite existence and possible extent of non-thermal effects is not fully established. The chairman of the United Kingdom's Health Protection Agency (HPA), Sir William Stewart, has said that "evidence of potentially harmful effects of microwave radiation had become more persuasive over the past five years." His report said that while there was a lack of hard information of damage to health, the approach should be precautionary. The HPA, however, disagrees with his assessment, and claims that there is no risk and no need for precaution. The official stance of the Health Protection Agency is that there is currently no proven risk from RF communication devices.
provides little evidence that living in homes characterized by high measured time-weighted average magnetic-field levels or by the highest wire-code category increases the risk of ALL in children.The NCI study was corroborated by a 1999 Canadian epidemiological study of leukemia in children. As a result of the NCI's findings, the US Department of Energy disbanded the EMF Research and Public Information Dissemination (RAPID) Program citing that its services were no longer needed.
In 2001, Ahlbom et al conducted a review into EMFs and Health, and found that there was a doubling in childhood leukemia for magnetic fields of over 0.4 µT, though importantly summarised that "This is difficult to interpret in the absence of a known mechanism or reproducible experimental support". In 2007, the UK Health Protection Agency produced a paper showing that 43% of homes with magnetic fields of over 0.4 µT are associated with overground or underground circuits of 132 kV and above.
Ahlbom's findings were echoed by Draper et al in 2005 when a 70% increase was found in childhood leukaemia for those living within of an overhead transmission line, and a 23% increase for those living between and . Both of these results were statistically significant. The authors considered it unlikely that the increase between and is related to magnetic fields as they are well below 0.4 µT at this distance. Bristol University (UK) has published work on a theory that could account for this increase, and would also provide a potential mechanism, being that the electric fields around power lines attract aerosol pollutants.
The World Health Organisation issued Factsheet N°263 in October, 2001 on ELF (Extremely low frequency) EMFs and cancer. It said that they were “possibly carcinogenic”, based primarily on IARC's similar evaluation with respect to childhood leukemia. It also said that there was “insufficient” data to draw any conclusions on other cancers. The WHO issued a new factsheet, N°322, in June, 2007 based on the findings of a WHO workgroup (2007), the IARC (2002) and the ICNIRP (2003), which reviewed research conducted since the earlier publication. The factsheet says “that there are no substantive health issues related to ELF electric fields at levels generally encountered by members of the public.” For ELF magnetic fields, the factsheet says “the evidence related to childhood leukaemia is not strong enough to be considered causal”, and “[as regards] other childhood cancers, cancers in adults, ... The WHO Task Group concluded that scientific evidence supporting an association between ELF magnetic field exposure and all of these health effects is much weaker than for childhood leukaemia. In some instances (i.e. for ... breast cancer) the evidence suggests that these fields do not cause them.”
Although a doubled risk may sound dramatic, childhood leukemia is a rather rare disease, and even at a doubled risk it would still be rare. In the US, the chance that a person develops leukemia during childhood is about one in 1,300 (based on 3,000 cases per year).
However, the California report concluded that they did not find there was a strong enough association between EMFs and birth defects and low birth weight, and were divided on the evidence for suicide and adult leukemia.
WHO Factsheet N°322 says that the scientific evidence for an association between ELF and “depression, suicide, cardiovascular disorders, reproductive dysfunction, developmental disorders, immunological modifications, neurobehavioural effects and neurodegenerative disease”, is weaker than for childhood leukemia, where no causal relationship was found, or even negative.
The first interim assessment of this group was released in April 2007, and found that the link between proximity to power lines and Childhood Leukemia was sufficient to involve a precautionary recommendation, including an option to lay new power lines underground where possible and to prevent the building of new residential buildings within of existing power lines.
The latter of these options was not an official recommendation to government as the cost-benefit analysis based on the increased risk for childhood leukemia alone was considered insufficient to warrant it. The option was considered necessary for inclusion as, if found to be real, the weaker association with other health effects would make it worth implementing.