Campos electromagnéticos Actualización 2009

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 effects of mobile phones on reproduction and development 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?

Some people complain of headaches, fatigue, dizziness or concentration difficulties, symptoms which have been suggested to be triggered by exposure to radio frequency (RF) 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). Although some new studies provided some indications of a link between radio frequency exposure and single symptoms, taken together, the findings are not consistent. Therefore, the conclusion that scientific studies do not support an effect of radiofrequency fields on symptoms still holds.

The way symptoms are reported varies depending on whether the subjects are aware of being exposed to radio frequency fields or not. Subjects who know they are exposed to some radio frequency fields, e.g. because they use a mobile phone or live near a transmission tower, tend to report more symptoms, whereas double-blind provocations studies where subjects do not know whether they are exposed to radio frequency fields or not do not find a consistent link between radio frequency fields and symptoms.

These results indicate a “nocebo” effect, an effect caused by the expectation or belief that something is harmful (a negative placebo effect).

There is no scientific evidence that humans - be it so-called sensitive groups or healthy control groups - can perceive radio frequency fields better than would be expected by chance. 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 these do not suggest any harmful consequences.

With the exception of a few findings in otherwise negative studies, there is no evidence that short or long-term radio frequency exposure at levels relevant for mobile telephony can influence processes linked to thought and memory in humans or animals. There is some evidence that radio frequency exposure might influence brain activity or sleep as seen by tests that recorded the electrical impulses in the brain of humans (electroencephalogram). However, certain findings are contradictory and there is a need for further studies into mechanisms that might explain possible effects on sleep and brain activity.

There is no evidence that exposure to radio frequency fields at the levels relevant for mobile telephony have effects on hearing or vision. Furthermore, there is no evidence that this kind of exposure has direct harmful effects on the brain and nervous system. Most studies show the absence of effects on cells that support or surround brain cells and on the blood-brain-barrier. Those that showed effects did not find a dose-response relationship and need to be repeated independently using improved methods.

A number of studies on animals find that relatively strong radio frequency fields can activate glial cells that surround and support brain cells, which could indicate neurological damage after exposure, but exposures at lower levels did not reveal any such effects. More...

4.3 Have effects of mobile phones on reproduction and development been reported?

Numerous studies have investigated the potential effect on development of animals, including mammals and birds. These studies, reviewed recently, clearly show that radio frequency 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 exposure levels that do not cause heating of the tissues.

A large recent Danish study found that seven-year-old children whose mothers had used mobile phones either during or after pregnancy had worse overall scores for behavioural problems. In light of the very low exposure to the children that would occur as a consequence of the mothers’ use of the phone during or after pregnancy it is doubtful that radio frequency exposure from mobile telephony could have anything to do with the observed association. Yet, the association remains unexplained at this time. Recent studies have evaluated possible effects of radio frequency fields on the development of animals in the womb at exposure levels associated with the use of mobile phones. However, it is not possible to draw conclusions from these studies because of methodological limitations.

Two studies examined fertility among men exposed to radio frequency fields in the Norwegian Navy. One of these studies used questionnaires to assess various self-reported health problems, including infertility, and expert assessments of exposure to radio frequency exposure. Self-reported infertility was more frequent among men working in telecommunications and with radars or sonars who are expected to be more exposed, however objective measures of fertility did not confirm such difference. The other study compared self-reported infertility to self-reported exposures and found a link between the two. However, the self-reported nature of these studies greatly limits their usefulness in drawing conclusions about the potential causal role of radio frequency fields.

A number of other studies have addressed the effects of radio frequency fields on male fertility and male reproductive organs. However, methodological problems prevent any conclusions to be drawn from those.

There are still no substantiated indications of any other health effects. 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 might 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. Children can also be exposed through other sources, such as the recently introduced DECT baby 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.

The rate at which children and adults absorb energy is known as the Specific Absorption Rate (SAR), and it varies throughout the body.

International guidelines aim to protect the population against adverse effects by setting maximum SAR values not to be exceeded (referred to as basic restrictions). Because the measurement of the actual SAR within the body is very challenging, reference levels in terms of electric and magnetic field strength were defined, which should ensure compliance.

Computer models were used to estimate internal exposure at field strengths equivalent to reference levels showing that it cannot be ruled out that children could exceed maximum SAR values.

In practice, it is important to realise that actual exposure levels are orders of magnitude below these reference field strengths. More...