2001 review of cancer

In a major review of the evidence for a possible association between exposure to power-frequency electric and magnetic fields and the incidence of cancer published in March 2001, the NRPB Advisory Group on Non-Ionising Radiation concluded:

“Laboratory experiments have provided no good evidence that extremely low frequency 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 a 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.”

The context of the Report makes clear that “prolonged exposure to higher levels of power frequency magnetic fields” and “intense and prolonged exposures to magnetic fields” refer to magnetic fields, in the home and often specifically in the child’s bedroom, assessed in epidemiological studies as having average values over 24 hours or longer of 0.4 microtesla (µT) or greater. The figure of 0.4 µT arises because it is a cutpoint that has been used in certain analyses of epidemiological studies. However, it would be wrong to regard 0.4 µT as a precise threshold above which there is a possibility of a risk and below which there is no possibility of a risk. More on fields of 0.4 µT

The conclusion of the Report concerning occupational exposure is, in part (pp163-164):

“Study of populations exposed occupationally to electromagnetic fields can include groups exposed generally at much higher levels than members of the public. They may therefore have a greater potential to detect any adverse health effects. Although recently published studies of occupational exposure to electromagnetic fields and the risk of cancer are, in the main, methodologically sound, and some of them have considerable statistical power, causal relationships between such exposure and an increase in tumour incidence at any site are not established.”

The NRPB, in responding to this Report from their Advisory Group, stated in part:

“Guidelines for limiting exposure to electromagnetic fields are presently based on preventing established health effects, which for ELF EMFs are those related to induced currents in the tissues of the central nervous system. Epidemiological studies are also taken into account. The Board considers that the AGNIR report provides no additional scientific evidence to require a change in exposure guidelines"

2001 review of neurodegenerative disease

In November 2001 the NRPB’s Advisory Group published a further Report on electromagnetic fields and neurodegenerative disease. The conclusion was:

“There is no good ground for thinking that exposure to extremely low frequency electromagnetic fields can cause Parkinson’s disease and only very weak evidence to suggest it could cause Alzheimer’s disease. The evidence that people employed in electrical occupations have an increased risk of developing amyotrophic lateral sclerosis is substantially stronger, but this could be because they run an increased risk of having an electric shock rather than any effect of long-term exposure to the fields per se.”

 

2002 comments on miscarriage

A statement by the Advisory Group on “Magnetic fields and miscarriage”, April 2002 discusses two papers on magnetic fields and miscarriage from California. It concludes:

"Conclusion
Neither study provides substantial evidence of increased risk of miscarriage attributable to exposure to above average magnetic fields and neither justifies regulatory action. It would be expensive and difficult to carry out further epidemiological investigation that would address the issue robustly and, in the absence of a plausible biological mechanism that would link such exposure to miscarriage, it is arguable whether it would be justifiable to support research of this type. If further study is required, it would be worth financing only if a large cohort of (say) 2000 women could both be interviewed and have measurements made of their exposures over a period of at least 24 hours less than 8 weeks after their last menstrual period and have repeat measurements made on at least two further occasions within the next 8 weeks to determine the consistency of the exposures throughout early pregnancy and their temporal relationship to miscarriage."

The NRPB’s Advisory Group had previously published a major review of power-frequency electric and magnetic fields and the risk of cancer in 1992, with supplementary reports in 1993, 1994 and 1997.

2003 Consultation on exposure guidelines

The NRPB consultation document on proposals for limiting exposure to EMFs included reviews of a wide range of epidemiological and biological findings. The conclusion on epidemiology was:

"There is little evidence to suggest that the risk of childhood leukaemia might be increased by exposure to ELF magnetic fields of time-weighted average flux density below 0.4 µT, or that raised cancer risks of other types, in children or adults, might arise as a result of exposure to EMF magnetic fields. Information specifically on electric fields is more sparse.

There is some epidemiological evidence that prolonged exposure to ELF magnetic fields of time-weighted average exposure above 0.4 µT is associated with a small raised risk of leukaemia in children. This evidence is not strong enough to justify a firm conclusion that such fields cause leukaemia in children.

The findings from studies of health outcomes other than cancer have generally been inconsistent or difficult to interpret.

Workers in electrical occupations do appear to have an increased risk of developing amyotrophic lateral sclerosis, but this may be due to effects of electric shocks rather than any effect of long-term exposure to ELF EMFs per se.

Whilst skin diseases do not appear to be caused by EMFs from VDUs, existing skin conditions may be aggravated by the associated electrostatic fields."

Although the various reports of the NRPB Advisory Group so far have concentrated on cancer, neurodegenerative disease and miscarriage, the studies which the Board take into account when setting exposure guidelines include other suggested health effects. For example, the 1993 NRPB exposure guidelines state (p11):

“Epidemiological studies of general health and birth outcome in populations exposed to electromagnetic fields have been reviewed in a Board report. These studies do not appear to show long-term health effects from the levels of electromagnetic fields to which people are normally exposed.”

The 2003 NRPB consultation document on exposure guidelines considers epidemiological studies on cancer, neurodegenerative diseases, suicide and depression, cardiovascular disease, other diseases, and reproductive outcome, and biological studies on, among other things, cancer, reproduction and development, and neurobehavioural effects, including cognitive effects, sleep, and hypersensitivity.

2004 Report on particle deposition in the vicinity of power lines

A Report by AGNIR into the suggested mechanisms whereby power lines might have an effect on airborne particles concluded:

“…it seems unlikely that corona ions would have more than a small effect on the long-term health risks associated with particulate air pollutants, even in the individuals who are most affected. In public health terms, the proportionate impact will be even lower because only a small fraction of the general population live or work close to sources of corona ions.”

and

“Any health risks from the deposition of environmental particulate air pollutants on the skin appear to be negligible.”

More on this report or more information generally on these suggested mechanisms.