4. Can mobile phones or base stations trigger headaches or other health effects?
- 4.1 Have headaches and other symptoms been linked to mobile phones?
- 4.2 Can mobile phones affect the brain?
- 4.3 Have other health effects of mobile phones been reported?
- 4.4 Are children more vulnerable to possible effects of mobile phones?
4.1 Have headaches and other symptoms been linked to mobile phones?
Mobile phone base station
Some people complain of headaches, fatigue, dizziness or concentration difficulties, symptoms which have been suggested to be triggered by exposure to radio frequency fields. Such complaints have raised concern that certain individuals may be more sensitive than others to electromagnetic energy. This self-reported condition has been referred to as electromagnetic hypersensitivity (EHS).
Studies on electromagnetic hypersensitivity fall mainly into two categories. Some focus on reports from people who say radio frequency fields are making them ill. Others look for an increase in symptoms among populations near mobile phone base stations.
The latter include a 2006 Austrian study that measured radio frequency fields in bedrooms of homes within 600 meters of mobile phone base stations. The residents, who did not know the exact nature of the study, were divided into three groups based on their level of exposure and questioned about 14 symptoms. Reports of three symptoms – headaches, cold hands and feet and trouble concentrating – were significantly more common in the highest exposure group.
Another study compared a group of healthy people exposed to radio frequency fields with a group who were not exposed and found no increase in symptoms. The participants did not know which group they represented. Similar studies found no consistent proof of ability to detect fields, neither in healthy people nor in people reporting symptoms.
In 2005, the World Health Organization conducted a workshop on radio frequency exposure. The consensus was that although symptoms described as electromagnetic hypersensitivity are real and may be severe and disabling, a relationship between symptoms and radio frequency field exposure has not been proven.
A 2003 study that received considerable attention found people more likely to suffer anxiety, depression, insomnia and other mental distress when they are exposed to radio frequency fields similar to those generated by base stations used in third-generation mobile networks (UTMS). The study was widely discussed because of the implications for the new technology. Follow-up studies were initiated in several countries including one published in 2006 that used a larger study group and better methods and found no effect on symptoms. There was no link between perceived field strengths and actual radio frequency exposure.
Overall, scientific studies have thus failed to provide support for a relationship between exposure to radio frequency fields and self-reported symptoms. Present knowledge suggests that symptoms are not linked to exposure to radio frequency fields, but few studies have addressed this issue directly. The exposure levels from base stations are very low compared to the exposure during the use of a mobile phone. Research regarding health effects from base stations is mainly driven by concern in the general population.
The symptoms attributed to radio frequency fields (RF) and extremely low frequency (ELF) fields– such as those generated by power lines – are similar and in many cases the individuals complain that both fields trigger symptoms. There are more studies on self-reported symptoms and exposure to ELF fields, but as for radio frequency fields the scientific studies have failed to confirm a causal link (See question 7.3). More...
4.2 Can mobile phones affect the brain?
Because mobile phones come in contact with the head, there have been concerns they could affect the brain. Some scientists have observed small but fleeting changes in the brain functions of people exposed to radio frequency fields, but studies disagree on the subject, with some finding transitory minor effects and others reporting no effect whatsoever.
Since the ear is very close to the exposure source, a number of recent studies have checked the hearing system during or after exposure. No effect has been observed, neither in people nor rats.
In animals, some studies found learning disturbances among rats exposed to radio frequency fields, but further research has not confirmed such effects. The most surprising effect observed among rats was increased permeability of the blood-brain-barrier, the membrane-like structure that acts primarily to protect the brain from many chemicals in blood, while allowing access to essential components (e.g., oxygen, glucose). Such increased permeability could allow harmful substances to reach the brain. The first research group to report increased permeability of the blood-brain-barrier at low exposure levels (SAR rates) observed similar changes in subsequent research. Other studies found no such changes, even with repeated exposure.
4.3 Have other health effects of mobile phones been reported?
Some scientists had observed blood pressure drops after mobile phone exposure but no other studies have confirmed these results. Studies pointing to an increased blood flow in the external ear have been replicated, however. Local temperature increases during exposure have been reported, possibly linked to the heat generated by mobile phone electronics and batteries.
Much of what scientists know about how radio frequency energy affects pregnancy comes not from mobile phone use but rather from research on physical therapists exposed to radio frequency fields while on the job. Studies focused on possible effects on the number of miscarriages, birth weight, gender ratio, and birth defects. Some studies have observed measurable effects, but no harmful effect has been consistently reported.
Numerous studies have investigated the potential effect on development of animals, including mammals and birds. These studies, reviewed recently, clearly show that RF fields can cause birth defects when the exposure is high enough to significantly raise temperatures in tissue; such exposure would be well above safety guidelines. No consistent evidence of effects has been found at an exposure level that does not cause heating of the tissues. More...
4.4 Are children more vulnerable to possible effects of mobile phones?
With so many children using mobile phones, there is growing concern about how radio signals may affect them. Some people worry that children could be more vulnerable than adults because their nervous systems are still developing, their brain tissue is more conductive, and their heads absorb more energy from mobile phones. Also, children who start using mobile phones will have a greater lifetime exposure than people who were adults when they began using mobile phones.
Few studies have addressed the possible effects of radio signals on children, and extrapolating from adult studies is problematic. One area that deserves investigation would be whether radio frequency radiation can cause childhood brain tumours. More...