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?
The source document for this Digest states:
3.3.3. Symptoms
What was already known on this subject?
In the 2001 opinion it was concluded that the knowledge was insufficient for the implementation of measures aimed at the identification and protection of a highly sensitive sub-group of the population. With regard to reports of subjective symptoms from individuals (possibly “hypersensitive”), the limited number of studies on volunteers had found no connection between reported symptoms and exposure to electromagnetic fields. There was a lack of information on the role of conditions of exposure (frequency, concentration duration etc) and possible biological mechanism. While epidemiological studies had not shown any consistent evidence of effects on humans, it was pointed out that this could not be taken to mean that RF field exposure does not pose any hazard to human health.
What has been achieved since then?
A variety of non-specific self-reported symptoms (for example headache, fatigue, dizziness and concentration difficulties) have been suggested to be triggered by exposure to RF fields. These possible health effects have been discussed and studied mainly from two different aspects: 1) a possible increase in symptoms in populations living close to mobile communication base stations and 2) reports from individuals that exposure to RF from mobile phones (and sometimes also base stations) triggers symptoms. In the latter case, some individuals attribute their health problems to an increased sensitivity (hypersensitivity) to electromagnetic fields. The term “electromagnetic hypersensitivity” (EHS) has been used to describe such cases of non-specific medically unexplained health problems attributed by the afflicted individuals to electromagnetic fields (in many cases including ELF fields) or to being in the vicinity of electrical equipment (see also the section on ELF fields 3.5.3 Symptoms).
There have only been a few attempts to study symptom prevalence and symptom severity in relation to exposure to RF fields from base stations. The methodological limitations of these cross-sectional epidemiological studies preclude conclusions regarding a possible causal relationship between increase in symptoms and exposure to RF. One study by Hutter et al. (2006) performed measurements of RF fields in the bedrooms of the participants. In this Austrian study, inhabitants of homes in the vicinity (distance 20-600m) of ten selected base stations (five in Vienna and five in a rural area, Carinthia) were invited to participate in a study on environment and health. Mobile communication base stations were not mentioned in the invitation. Spot measurements were done after the questionnaires and computer based tests were completed. The participants were classified into three exposure groups based on calculations of the theoretical maximal power density from the selected base stations (i.e. when the base station is using 100% of its capacity). The mean power densities were 0.04, 0.23 and 1.3 mW/m2 in the respective groups. Three out of 14 self-reported symptoms (headache, cold hands or feet and difficulties to concentrate) were significantly more commonly reported in the highest exposure group. The results were adjusted for age, sex, region, regular use of mobile phone and fear of adverse effects of the base station, but not for socio-demographic factors. Exposure from other sources (e.g. other base stations) was not reported. The results should be replicated before any conclusions on a causal relationship between RF exposure and the reported effect on some symptoms may be drawn. Provocation studies on symptoms should also be considered. Compared to epidemiological studies provocation studies may have the advantage of better controlled exposure conditions and randomization. The focus is however somewhat different in provocation studies, which will assess only acute effects while epidemiological studies may include long term effects on well-being.
A relationship between RF and symptoms in healthy volunteers was investigated in one provocation study (Koivisto et al. 2001). No increase in symptoms was observed during RF exposure as compared to sham exposure. The limited number of studies on detection of RF at exposure levels relevant to mobile communication systems under blind conditions has not provided any consistent proof of ability to detect the fields, neither in healthy individuals nor in subjects who report EHS.
Health complaints described as EHS and reported to be triggered by mobile phones have also been studied in a limited number of provocation studies. A WHO Workshop on Electrical Hypersensitivity (WHO 2005) and recent reviews of the literature on subjective health complaints associated with electromagnetic fields of mobile phone communication (Seitz et al. 2005) and provocation studies including subjects reporting EHS (Rubin et al. 2005) have presented similar conclusions. The main conclusion is that although symptoms described as EHS are real and may be severe and disabling, a relationship between symptoms and RF field exposure has not been proven. Most likely, the health problems described as EHS are not related to the physical presence of EMF and more research is needed to learn more about the conditions inducing EHS.
The studies published after the WHO workshop and the reviews mentioned above have not provided any information that would contradict these conclusions. The influence of a base station-like exposure of 2140 MHz RF fields on well-being that was reported already in 2003 (Zwamborn et al. 2003) was not confirmed in a follow-up study (Regel et al. 2006). In a study published by the TNO-Institute23 (the so called TNO study), only available as grey cover report Zwamborn et al. (2003) found a decrease in well-being (based on an index of 23 items from subscales of anxiety, somatic symptoms, inadequacy, depression and hostility) during exposure to 2140 MHz RF fields (UMTS). The decrease in well-being was shown in the group of subjects who were recruited based on self-reported sensitivity to RF fields as well as in the non-symptomatic control group. No effect on symptoms was observed in any of the groups for 945 MHz or 1840 MHz RF fields (GSM). The study, while reporting an effect of UMTS exposure, thus failed to confirm the reported belief in the group with self-reported sensitivity that GSM exposure triggered symptoms. The TNO study was widely discussed since a possible health effect of UMTS might have large implications on the introduction and use of the third generation of mobile networks (UMTS). Follow-up studies were initiated in several countries and in 2006 the first results were published (Regel et al. 2006). The experimental protocol was improved as compared to the TNO-study, e.g. a larger study group, better dosimetry and longer intervals between the exposure sessions. Two exposure levels of RF fields (E-fields strength of 1 V/m –as in the TNO study- and 10 V/m) were applied, in order to assess any possible dose-response relationship. Peak spatial SARs in the brain (averaged over 10 g) were 45 and 4500 µW/kg. Well-being was assessed in two standard questionnaires (including the one used in the TNO study). No effect on symptoms was observed, neither in the group of subjects with self-reported RF- related symptoms nor in the non-symptomatic control group. There was no association between perceived field strengths and actual RF exposure.
Discussion
Scientific studies have failed to provide support for a relationship between RF exposure and self-reported symptoms sometimes referred to as EHS. Present knowledge suggests that symptoms are not correlated to RF field exposure, 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 where exposure is significantly lower than for mobile phone users is mainly driven by concern in the general population.
The symptoms attributed to ELF and RF fields are similar and in many cases the afflicted subjects report both ELF and RF fields to trigger symptoms. There are more studies on self-reported symptoms and exposure to ELF fields, but also in this case the scientific studies have failed to confirm a causal relationship (see also the section on ELF fields 3.5.3 Symptoms).
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Section 3.3 Radio Frequency Fields, 3.3.3 Symptoms, p.23-25
4.2 Can mobile phones affect the brain?
The source document for this Digest states:
3.3.4. Nervous system effects
What was already known on this subject?
Due to the proximity of mobile phones to the head, public concerns were raised regarding a potentially toxic effect of RF on the central nervous system. Five aspects are usually considered in toxicology regarding the nervous system: morphology, brain function, electrophysiology, behaviour and development (which is addressed in a later paragraph).
Several studies had been published concerning the potential neurotoxic effects of radiofrequencies emitted by the mobile phones. Transient minor effects were observed on the electroencephalogram (EEG), sleep structure, and on cognitive processes in human subjects (Mann and Röschke 1996, Preece et al. 1999, Huber et al. 2000, Koivisto et al. 2000a, Koivisto et al. 2000b, Krause et al. 2000). Some of the observations could not be replicated (Wagner et al. 1998, Wagner et al. 2000), and studies with negative outcomes were also published (Röschke and Mann 1997).
In animals, some previous studies did show disturbance of work memory in rats exposed to RF (Lai et al. 1994, Wang and Lai 2000). However, the most surprising effect was that very low SAR values (mW/kg) caused increased permeability of the blood-brain-barrier
(BBB) in rats (Salford et al. 1994, Persson et al. 1997). Alterations of the BBB had also been found in another study (Neubauer et al. 1990), but not by Tsurita et al. (2000). In rats exposed to 2 W/kg Fritze and co-workers demonstrated effects on the BBB only at SAR levels above 7.5 W/kg (Fritze et al. 1997). The BBB isolates the CNS from the rest of the organism, controls molecule fluxes, and protects the brain (Purves et al. 2001). Increased permeability of the BBB can allow unwanted substances to reach the CNS, with possible pathological consequences (inflammation, neurone death).
What has been achieved since then?
Human studies
In humans, transitory minor effects (both positive and negative) have been observed on EEG patterns, sleep structure, and cognitive processes (D’Costa et al. 2003, Cook et al. 2002, Hossmann and Hermann 2003, Sienkiewicz et al. 2005). Also studies where no effects were documented have been published, even after a repeated exposure (Besset et al. 2005).
Since the ear is very close to the exposure source, some studies have checked the auditory system under or after exposure, and even after repeated cumulative exposure. No effect has been observed (Ozturan et al. 2002, Arai et al. 2003, Bak et al. 2003, Parazzini et al. 2005, Uloziene et al. 2005).
Animal studies
Slight changes in EEG activity and neurotransmitters have been observed in animals at low SARs (reviewed by Sienkiewicz et al. 2005). Regarding cognitive functions, a recent report showed that a disturbance of learning and memory in rats exposed at 2.45 GHz CW could be inhibited by a magnetic field (incoherent noise) (Lai 2004a). Results from earlier studies on learning and memory at non-thermal RF levels have not been corroborated (Dubreuil et al. 2003, Yamaguchi et al. 2003, Cobb et al. 2004, Cassel et al. 2004). No morphological effects have been observed below thermal thresholds (D’Andrea et al. 2003).
Salford and co-workers published another work showing changes in BBB permeability at low SAR (Salford et al. 2003), whereas others did not find any such alteration (Finnie et al. 2001), even with repeated exposures up to 2 years (Finnie et al. 2002).
No effects have been seen on auditory system function (Aran et al. 2004) or on development of multiple sclerosis in rats (Anane et al. 2003b).
What are the overall conclusions?
Those changes do not act on cognitive processes, behaviour or memory and do not suggest pathological hazards. Furthermore, no clear role of modulation has appeared Although extrapolation from animals to humans raises some difficulty, the rat or the mouse are common models to look for toxicity and the few studies showing significant alterations are to be considered carefully. For all cognitive experiments in animals, stress effects due to restraint must be clearly identified and prevented when looking at effects of RF fields.
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Section 3.3 Radio Frequency Fields, 3.3.4 Nervous system effects, p.25-27
4.3 Have other health effects of mobile phones been reported?
The source document for this Digest states:
3.3.5. Miscellaneous human
Initial observations of a blood pressure decrease after mobile phone exposure have not been replicated (Braune et al. 1998, Braune et al. 2002). The only effects on cardio-vascular functions that have been replicated are increased blood-flow in the external ear (Monfrecola et al. 2003, Roelandts 2003). Local temperature increases during exposure have been reported (Paredi et al. 2001, Curcio et al. 2004), possibly related to vasodilation caused by heating of mobile phone electronics and battery.
3.3.6. Reproduction and development
Epidemiological studies of adverse pregnancy outcomes following exposure to RF fields have been reviewed by Verschaeve and Maes (1998), Heynick and Merrit (2003) and Feychting (2005a). The evidence on possible effects of RF fields on pregnancy outcomes is virtually limited to occupational exposures among physiotherapists. The endpoints studied include spontaneous abortions, birth weight, gender ratio, and congenital malformations. Although some positive findings have been reported, no specific type of malformation or other adverse outcome has been consistently reported. Several of the studies have limited statistical power, especially for rare outcomes such as malformation, and there is a potential for recall bias. The available results do not allow any definite conclusions.
Numerous studies have evaluated developmental effects of RF fields on mammals, birds, and other non-mammalian species. These studies, reviewed recently by Heynick and Merritt (2003) and Juutilainen (2005), have clearly shown that RF fields are teratogenic at exposure levels that are sufficiently high to cause significant increase of temperature and exceed reference levels from exposure guidelines. There is no consistent evidence of effects at nonthermal exposure levels. However, only a few studies have evaluated possible effects on postnatal development using sensitive endpoints, such as behavioural effects.
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Section 3.3 Radio Frequency Fields , p.27
4.4 Are children more vulnerable to possible effects of mobile phones?
The source document for this Digest states:
3.3.7. Sensitivity of children
Concerns about the potential vulnerability of children to RF fields have been raised because of the potentially greater susceptibility of their developing nervous system; in addition, their brain tissue is more conductive than that of adults since it has a higher water content and ion concentration, RF penetration is greater relative to head size, and they have a greater absorption of RF energy in the tissues of the head at mobile telephone frequencies. Finally, they will have a longer lifetime exposure.
Few relevant epidemiological or laboratory studies have addressed the possible effects of RF field exposure on children. Owing to widespread use of mobile phones among children and adolescents and relatively high exposures to the brain, investigation of the potential effect of RF fields in the development of childhood brain tumour is warranted. The characteristics of mobile phone use among children, their potential biological vulnerability and longer lifetime exposure make extrapolation from adult studies problematic.
There is an ongoing debate on possible differences in RF absorption between children and adults during mobile phone usage, e.g. due to differences in anatomy (Wiart et al. 2005, Christ and Kuster 2005). Several scientific questions like possible differences of the dielectric tissue parameters remain open.
The anatomical development of the nervous system is finished around 2 years of age, when children do not yet use mobile phones although baby phones have recently been introduced.
Functional development, however, continues up to adult age and could be disturbed by RF fields.
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Section 3.3 Radio Frequency Fields, 3.3.7 Sensitivity of children, p.27
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