9. What is known about environmental effects of electromagnetic fields?
- 9.1 Are there new findings on environmental effects of radiofrequency fields?
- 9.2 Are there new findings on environmental effects of extremely low frequency fields?
Migratory birds rely on magnetic fields for orientation
Credit: Michael Hatherly
Field studies on individual animal and plant species living in close proximity to sources of electromagnetic fields are important to determine whether ecosystems might be substantially affected. In addition, such studies may provide information on the potential of electromagnetic fields to cause adverse effects in humans.
Past field studies have mainly focused on wild birds and on potential effects on reproduction and orientation as certain species use magnetic fields for navigation purposes.
Though some new study results have recently been published, overall, the available data remains inadequate for the assessment of possible risks due to environmental exposure to radio frequency, intermediate frequency and extremely-low frequency fields. More...
9.1 Are there new findings on environmental effects of radiofrequency fields?
Studies indicate that exposure of wild birds to radio frequency fields can, under certain circumstances, change their behaviour, reproductive success, growth and development, physiology, and other parameters. However, the changes observed are neither all in the same direction, nor consistent.
Two independent field studies carried out in Spain and Belgium suggest a link between the reduction in house sparrow population in urban areas and exposure to radio frequency fields. However, there are a number of other possible contributing factors, including pollution and loss of preferred food sources, and further investigations are needed. A study showed that there were differences in the relative numbers of two varieties of tits breading near a radar station, a strong source of radio frequencies. One interpretation is that the radio frequency fields may discourage some bird species or encourage others. Another possible explanation is that RF fields modify the reproductive behaviour of insects that serve as food sources for various bird populations.
One study found that adult tufted puffins carrying radio transmitters – so that they may be tracked in the wild – tended to have poorer breeding success and their offspring lower growth rates than puffins without transmitters. The cause of this difference was attributed to the radio frequency fields of 2 to 5 W/m2 from the transmitters. More...
9.2 Are there new findings on environmental effects of extremely low frequency fields?
A number of field studies have considered birds of prey living around overhead power lines – that produce extremely low frequency fields – and the birds ability to reproduce. Findings vary widely, and no clear overall conclusion can be drawn. A field study on the effects of the ELF magnetic field of a buried electricity transmission cable showed a reduction of the biological activity in the surrounding soil. The environmental significance of these field studies is uncertain.
Studies on plants, particularly on the potential use of extremely low frequency fields to promote plant growth in nurseries, have shown that ELF magnetic fields can promote the growth of certain plant species. Optimum growth was observed at levels of around 100-150 mT. It is however unclear what the effects are on different plant species, and if it only affects plant growth.
Several laboratory studies on cell cultures have shown detectable effects of extremely low frequency fields in the millitesla range on bacteria, small freshwater crustaceans (Daphnia) as well as bird and chicken tissues. More...