What effects do mobile phones have on people’s health?
The issue
During recent years, the use of mobile phones has increased substantially and has been paralleled by a
growing concern about the effects on health attributed to exposure to the electromagnetic fields
produced by them and their base stations. Demonstrating that radiation causes adverse effects on
health would signal a widespread public health problem.
Findings
Mobile phones have been in extensive use for a relatively short period of time, and their technology
has progressively changed, from analogue to digital systems. Mobile phones and base stations emit
radio frequency or microwave radiation. Exposure to such a radiation could affect health directly. The
use of mobile phones also results in indirect effects, such as car accidents and interference with health
equipment.
Experimental research on the effects of radio-frequency radiation is very broad and heterogeneous. It
includes both studies of cell cultures and tissues (in vitro) and of laboratory animals (in vivo), as well
as of people (volunteers). On one hand, these studies focus on functional changes in the brain and the
resulting effects on cognition, and (to some extent) well-being – that is, the influence of exposure to
radiation on the head. On the other hand, these studies focus on the possibility of a relationship
between mobile phone use and carcinogenic processes, reproduction and development, the
cardiovascular system and longevity – that is, exposure of the whole body. These studies found very
small and reversible biological and physiological effects that do not necessary lead to diseases or
injuries. Also, the research findings on the changes at the molecular level associated with the
development of cancer are inconsistent and contradictory.
Epidemiological studies in general populations, such as communities, concentrate on a possible causal
relationship between mobile phone use and the occurrence of brain tumours, acoustic neuromas,
tumours of the salivary glands, and leukaemia and lymphomas. Although weak and inconclusive, most
of the evidence available does not suggest that there are adverse effects on health attributable to longterm
exposure to radio-frequency and microwave radiation from mobile phones. However, recent
studies have reported an increased risk of acoustic neuroma and some brain tumours in people who use
an analogue mobile phone for more than 10 years. Also, no data is available on the reproduction of
these effects when digital mobile phones are used. Finally, there is good evidence that the use of
mobile phones while driving translates into a substantially increased risk of an accidental collision.
Policy considerations
For the majority of tumours studied so far, a long latency period might exist, and the finding of any
link to the use of mobile phones is complex. Consequently, most of the published research cannot
elucidate the risk of long-term effects. If there is a risk, the current evidence suggests it is small.
Since there are still gaps in knowledge, continued research and better health risk analyses are needed.
Moreover, without scientifically recognized adverse effects on health, it is not possible to produce
evidence-based recommendations.
Therefore, a precautionary approach to the use of this communication technology should be adopted
until more scientific evidence on its effects on health becomes available. Such an approach includes
restricting exposure (according to existing guidelines and the European Union (EU) Directive) and
providing the public with information and options.
Introduction
In recent years, mobile telecommunication systems have grown significantly, to the point where more
than a sixth of the world’s population use mobile phones. By the end of 2004, more than a billion
subscribers across more than 200 countries were estimated to be using mobile phones (1, 2).
The development of mobile communications has moved rapidly. In the 1980s, first generation mobile
phones, using analogue technology, allowed the transmission of sound only. Digital transmission, and
the global system for mobile communication, started in 1991 and includes such new developments as
data and image transmission. Third generation mobile phones currently in the market offer additional
services to the users (such as fax, e-mail and Internet access). For both analogue and digital mobile
phones, the signals transmitted and received are in the form of waves in the radio frequency (RF)
(analogue) and microwave parts of the electromagnetic spectrum. RFs are non-ionizing radiation with,
wavelengths that range from 3 kHz to 300 MHz, and microwaves range from 300 MHz to 300 GHz1.
The frequencies that mobile phones and telecommunication networks use range from 900 MHz to
1.8 GHz and up to 2.1 GHz, although it should be noted that the wavelength of the different types of
mobile phones varies. This applies to both mobile phones and their base stations, which send and
receive calls.
People have welcomed the technology, as indicated by the widespread use of mobile phones, which
suggests that they do not perceive it as a potential health hazard. However, concerns about the possible
adverse effects on health, as a result of the exposure to RF and microwave electromagnetic fields, have
been expressed since the introduction of mobile phones.
Since the year 2000, several reports have reviewed relevant studies and summarized current
knowledge about mobile phones and health, particularly that related to the commonly accepted
carcinogenic effects of RF and microwave energy. The aim of this synthesis is to combine the
available epidemiological evidence, to learn whether exposure to RF and microwave radiation from
mobile phones and their base stations might affect health. This synthesis does not aim to analyse the
effect of other man-made sources of electromagnetic fields, nor does it aim to develop safety
standards. The WHO International EMF Project is currently producing this information (3).
Sources for this review
This synthesis assesses the clinical effects of day-to-day exposure to mobile phones in general
populations, such as communities – specifically, the impact on developing head and brain tumours
(benign and malignant). It also addresses other morbidity related outcomes and summarizes the
biological effects of RF and microwave radiation.
Two main sources of information were considered and reviewed. A search of scientific and biomedical
databases was performed until March 2006. Observational studies that assessed the effects of mobile
phones on general populations were included in the synthesis. Experimental studies that assessed
clinical effects were excluded, as were those of occupational settings. The quality of the studies was
assessed by using the grading system developed by the Scottish Intercollegiate Guidelines Network. Also, a review of documents and web sites of governments, health councils, radiological
protection boards, advisory and expert groups, and the like, was undertaken. Annex 1 gives details
about the literature search strategy.
Findings
Scientific literature
Biological and physiological effects
Experimental research on the biological effects of RF and microwave fields is very broad and includes
studies of volunteers, animals and in vitro, cell-based techniques (5, 6). The studies cover the effects
of RF and microwave radiation between 100 MHz and 60 GHz and focus both on the functional
changes in the brain (influence of exposure to RF and microwave fields on the head) and on
carcinogenic processes, reproduction and development, the cardiovascular system and longevity (as a
result of whole body exposure to RF and microwave fields).
The biological effects observed on the cardiovascular, endocrine and immune systems and on the
behaviour of animals studied seem to be thermal effects of acute exposure to RF and microwave
radiation, with increases of at least 1 °C or 2 °C in temperature needed to produce these effects. As to
the increased risk of developing cancer after exposure to RF or microwave fields, the evidence for
such an association is extremely weak. Since the radiation from mobile phones and signal stations
does not have enough energy to break chemical or molecular bonds directly, there is no basis in theory
to suggest that they can damage DNA. Moreover, a biological mechanism that explains any possible
carcinogenic effect from RF or microwave fields has yet to be identified. Because of the difficulties in
interpreting findings from laboratory studies, the hypothesis that RF or microwave radiation is harmful
and could have effects on health that have not yet been recognized cannot be rejected.
Indirect experimental results are difficult to extrapolate. In vitro experiments that show abnormal cell
proliferation, changes in cell membranes, and movement of ions and substances across membranes are
difficult to extrapolate to people. It is also difficult to extrapolate to people the observed effects on
cerebral functions that relate to the behaviour of rodents since, among other reasons, the whole brain
of these small animals is exposed to radiation whereas the brains of people who use mobile phones,
although being exposed, receive the highest exposure in the part closest to the handset. Moreover, the
thermal effects of radiation are unlikely to be seen in people, as the increase in the local temperature of
the brain induced by the microwaves generated by mobile phones is negligible (it has been estimated
to be up to 0.1 °C) (7). Finally, there is no evidence of non-thermal effects on human health.
It is important to distinguish between biological (or physiological) effects and psychological and
health effects. The demonstration of an RF or microwave radiation effect in experimental research
does not necessarily mean that such exposure will lead to harmful effects on human health. Human
bodies, with the aid of their immune, nervous or endocrine systems, can effectively resist some
external pressures, adapt to them and maintain the stability (homeostasis) disrupted by those changes.
Clinical effects
Within human population studies, epidemiological studies provide the most direct information on the
long-term effects on health of any potential harmful agent. To assess the adverse effects on health that
may result from the use of mobile phones, research with a specific focus on cancer has been carried
out. By the end of the 1990s, the number of studies was small and the works presented major
methodological limitations, the most outstanding one being the lack of enough people with an
exposure time long enough to accurately assess the potential adverse late effects on health of mobile
phone use.
The majority of those studies suggested the need for additional, high-quality research. As a result of
these recommendations, a series of multinational case-control studies, coordinated by the International
Agency for Research on Cancer (IARC), were set up after a detailed feasibility study was carried out
in 1998 and 1999.
Overall, these studies are named the INTERPHONE Study (8), and their primary objective is to assess
whether exposure to RF or microwave radiation from mobile phones is associated with a risk of
cancer. Priority is given to epidemiological studies of the relationship between the use of mobile
phones and the incidence of:
• brain tumours;
• salivary gland tumours, acoustic neuromas and other head and neck tumours; and
• leukaemia and lymphomas.
If the risk of developing a brain tumour exists at all, the wider use of mobile phones and the expected
number of people who will develop a brain tumour will be sufficient to detect a potential 1.5-fold
increase in risk 5–10 years from the start of use.
Participant countries, with the longest and highest use of mobile phones, are Australia, Canada,
Denmark, Finland, France, Germany, Israel, Italy, Japan, New Zealand, Norway, Sweden and the
United Kingdom. Initially, the study expected to find about 6000 cases of glioma and meningoma
(both benign and malignant), 1000 cases of acoustic neuroma, 600 cases of parotid gland tumour and
their respective controls. The first results of the INTERPHONE Study were available in 2004 (9, 10)
and, since then, four additional papers have been published (11–14). It should also be noted that these
studies evaluated the impact on health of exposure to RF and microwave radiation emitted by mobile
phones, and not by antennas and base stations.
With regard to brain tumours, most of the studies yielded negative results, although a few of them
suggested an increased risk for mobile phone users. Because of these results, it is not possible to
establish an association between the use of mobile phones and an increased risk of brain tumours.
With regard to acoustic neuroma – a rare, benign tumour on the auditory nerve – the studies available
reported inconsistent results, except for the most recent ones, which found an association between an
increase in the risk of this type of tumour and 10 years or more of mobile phone use; moreover, the
increased risk is confined to the side of the head where the phone was usually held. No indications of
an increased risk for less than 10 years of mobile phone use were found. Before definite conclusions
can be drawn, the results of these studies have to be confirmed by additional research.
This type of research, however, faces several problems. One is that long-time users first used analogue
phones, and then digital phones. No risk has been found for digital phone use only, but then the
follow-up time is shorter. Other methodological problems, such as recall bias, have been identified:
people, especially patients, might have a selective memory on the side of the head where the telephone
was used (15).
A number of clinical complaints related to the use of mobile phones are reported in the scientific
literature. They include headache, fatigue, sleep disorders, loss of memory, dizziness, feelings of heat
or tingling in the auricular (or auditory) area or in the head, vertigo, deafness and blurred vision. Very
few studies are available, and their results provide no evidence of an association between these
symptoms and the use of mobile phones. It should be noted, however, that these are general,
nonspecific symptoms that may be induced by a wide range of causes. Since they represent a problem
for those suffering, the cause should be elucidated.
In summary, the evidence available does not support the hypothesis that mobile phone use is
associated with an increased risk of malignant brain tumours, but an increase in the risk of acoustic
neuroma after 10 years or more of mobile phone use has been found. Therefore, it seems that neither
acoustic neuroma nor brain tumours are related to mobile phone use of less than 10 years.
Nevertheless, those studies were conducted with data from the time when only analogue mobile
phones had been in use for more than 10 years, and they cannot determine if the results would be similar after long-term use of digital mobile phones. Likewise, a carcinogenic effect after a very long
period of exposure would remain undetected.
The most important and clearly defined effect of mobile phones on health, and the only clearly
established risk from an epidemiological perspective, is motor vehicle accidents, which obviously are
not related to exposure to RF or microwave radiation. The results of some studies show that the use of
a mobile phone up to 10 minutes before a crash is associated with a fourfold increase in the risk of
having a collision that results in injury. The risk increases irrespective of whether or not a hands-free
phone is used (16, 17).
Table 2 describes the characteristics of the design of epidemiological studies and the outcomes of
these studies.
Reports (grey literature)
Since the year 2000, a significant number of reports and reviews on the connection between mobile
phone use and health have been issued by committees, institutions, expert groups and agencies of
worldwide prestige, to appraise relevant literature, draw up guidelines and make recommendations to
limit exposure to RF and microwave radiation.
The National Radiological Protection Board summarized (18) the information from several sources,
from the publication of the Stewart Report, in May 2000, to the end of 2004. The Board, an
independent body that is now part of the Health Protection Agency, has responsibility for advising
government departments and others in the United Kingdom on standards of protection for exposure to
ionizing and non-ionizing radiation, which includes electric and magnetic fields.
The Stewart Report (5) is a widely quoted review on mobile phones and health. The Government of
the United Kingdom commissioned the Independent Expert Group on Mobile Phones, which was
chaired by Sir William Stewart, to prepare the Report. The Report concluded that the balance of
evidence did not suggest that exposure below international guidelines could cause adverse effects on
health. However, it recommended that a precautionary approach – that is, limiting exposure to RF and
microwave radiation, planning the location and setting of base stations and encouraging a selective use
of mobile phones – be adopted until more detailed and scientifically robust information on any adverse
effects on health becomes available. Besides health issues, the Report offered advice on exposure
standards and planning to government, industry and others and on public information and consumer
choices. It also proposed setting up a research programme.
According to the National Radiological Protection Board summary report (18), most of the 26 reports
examined reached similar conclusions and made comparable recommendations. Overall, the reports
acknowledge that exposure to low-level RF and microwave fields may cause a variety of slight
biological effects on cells, animals or people, particularly on brain activity during sleep, but the
possibility of exposure causing adverse effects on health remains unproven. The reports also present
guidance on public policy to decision-makers and legislators, and some of them favour any form of
precautionary or prudent approach to reducing personal exposure to the fields produced by mobile
phones.
Specifically, most reports recommend limiting the use of mobile phones by children. This has been
recommended in the absence of explicit scientific data. However, ethical and practical concerns limit
or prevent experimental studies on children. Because of a much higher cumulative exposure than
today's adults when they were at the same age, children might be more vulnerable to any effects of RF
and microwave radiation. As long as adverse effects on health cannot be ruled out with some degree of
certainty, it appears to be appropriate to instruct children and their parents about a prudent use of
mobile phones. Moreover, in the absence of new scientific evidence, WHO is focusing attention on the
potential effects of exposure to electromagnetic fields on children (19). Finally, many reports agree
that the distraction caused by mobile phone use while driving represents a serious threat to health.
Table 3 contains a selection of national and international reports on mobile phone use and its effects
on health, along with the links to the corresponding web pages.
Discussion
Results among investigations were inconsistent, and these investigations indicated little or no
association between exposure to RF and microwave radiation and cancer. It should be noted that the
weak evidence on carcinogenicity obtained from several epidemiological studies applies only to the
type of cancer studied and to the time intervals observed between exposure and occurrence of disease.
Also, experience with cancer in people indicates that, in some cases, the period from first exposure to
the development of clinical cancer is seldom less than 20 years; moreover, latency periods
substantially shorter than 30 years cannot provide evidence for lack of carcinogenicity (20).
Progress and changes in mobile phone technology (such as analogue to digital signals) make it
difficult to assess exposure in the people studied. Furthermore, because the use of mobile phones is
relatively recent, it may be premature to conduct an exhaustive epidemiological assessment of its
impact on health. In the case of cancer, for example, the information available does not rule out the
possibility of an association between the use of mobile phones and the occurrence of this disease.
Thus, it is advisable to monitor the incidence of tumours supposedly associated with exposure to RF
and microwave radiation, to assess possible changes in trends.
Conclusions
The evidence available does not provide a clear pattern to support an association between exposure to
RF and microwave radiation from mobile phones and direct effects on health (such as increasing the
risk of cancer). However, the quality of this research and the relatively short-term data do not allow
ruling out adverse effects on health completely. In other words, the absence of evidence of detrimental
effects on health associated with mobile phone use is not evidence of absence of such effects. At the
moment, it is impossible to state that exposure to RF or microwave radiation (even below the
permitted levels) does not have adverse effects on the health of the general population. The current
evidence, however, does suggest that if there is a risk, it is small. Therefore, a precautionary approach
(as recommended by the EU (21)) to the use of this communication technology should be adopted
until more scientific evidence on effects on health becomes available.
Finally, evidence shows that the use of a mobile phone while driving translates into a significantly
increased risk of a traffic accident.
Annex 1. Sources of information and methods
Scientific and biomedical literature
The review was done after a bibliographic search (up to March 2006) of databases, using relevant key
words, selection (inclusion/exclusion) criteria and a grading scale.
Databases
The following databases were searched:
• MEDLINE
• EMBASE
• The Cochrane Library
• ENVIROLINE
• INSPEC
• PASCAL
• SCISEARCH.
Key words
The following keywords were used in the search: telephone, phone, cell phone, cellular phone, mobile
phone, cell telephone, cellular telephone, mobile telephone, antenna, station, hazards, risks, health
electromagnetic fields, radio waves, microwaves.
Selection criteria
The following inclusion and exclusion criteria were used in this synthesis:
• inclusion criteria: papers about the effects of RF from mobile phones and their base stations
on the general population published in English, French and Spanish.
• exclusion criteria: papers about the effects of RF from mobile phones and their base stations
in experimental studies and occupational settings; however, a summary of experimental
research findings is provided.
In an experiment, the exposition to the agent or putative cause is due because the investigator has
assigned the exposure to the subject in order to comply with a study protocol. Because the goals of the
study rather than the subject’s needs determine the exposure assignment, ethical constraints limit the
circumstances in which these types of studies are feasible. Experiments are ethically permissible only
when adherence to the scientific protocol does not conflict with the subject’s best interests.
Grading scale
The grading system used for the evidence is that developed by the Scottish Intercollegiate Guidelines
Network (SIGN) (4). Table 1 shows the SIGN levels of evidence for this system.
Grey literature
A review was undertaken of major documents and web sites of governments, health councils,
radiological protection boards, advisory and expert groups, and the like, since the year 2000.
Most of the epidemiological studies from which the reviewed evidence comes are case-control studies.
In case-control studies, subjects are selected according to their disease status (in the case of this synthesis, it was presence or absence of a brain tumour) and further classified according to their
exposure status (in the case of this synthesis, it was exposure to mobile phones). This type of design
provides mid- to low-level evidence, according to the grading system used (4), since the methodology
is less strong. Nevertheless, for the ethical reasons mentioned above, which relate to experimental
studies, cohorts – that is, studies in which subjects are classified according to their exposure status and
followed over time to ascertain disease incidence – and case-control studies are considered the best
designs to study potential risk factors for human health due to the inability to use intervention studies.
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References
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7. Dimbylow PJ, Mann SM. SAR calculations in an anatomically realistic model of the head for
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WHO Regional Office for Europe’s Health Evidence Network (HEN)
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The issue
During recent years, the use of mobile phones has increased substantially and has been paralleled by a
growing concern about the effects on health attributed to exposure to the electromagnetic fields
produced by them and their base stations. Demonstrating that radiation causes adverse effects on
health would signal a widespread public health problem.
Findings
Mobile phones have been in extensive use for a relatively short period of time, and their technology
has progressively changed, from analogue to digital systems. Mobile phones and base stations emit
radio frequency or microwave radiation. Exposure to such a radiation could affect health directly. The
use of mobile phones also results in indirect effects, such as car accidents and interference with health
equipment.
Experimental research on the effects of radio-frequency radiation is very broad and heterogeneous. It
includes both studies of cell cultures and tissues (in vitro) and of laboratory animals (in vivo), as well
as of people (volunteers). On one hand, these studies focus on functional changes in the brain and the
resulting effects on cognition, and (to some extent) well-being – that is, the influence of exposure to
radiation on the head. On the other hand, these studies focus on the possibility of a relationship
between mobile phone use and carcinogenic processes, reproduction and development, the
cardiovascular system and longevity – that is, exposure of the whole body. These studies found very
small and reversible biological and physiological effects that do not necessary lead to diseases or
injuries. Also, the research findings on the changes at the molecular level associated with the
development of cancer are inconsistent and contradictory.
Epidemiological studies in general populations, such as communities, concentrate on a possible causal
relationship between mobile phone use and the occurrence of brain tumours, acoustic neuromas,
tumours of the salivary glands, and leukaemia and lymphomas. Although weak and inconclusive, most
of the evidence available does not suggest that there are adverse effects on health attributable to longterm
exposure to radio-frequency and microwave radiation from mobile phones. However, recent
studies have reported an increased risk of acoustic neuroma and some brain tumours in people who use
an analogue mobile phone for more than 10 years. Also, no data is available on the reproduction of
these effects when digital mobile phones are used. Finally, there is good evidence that the use of
mobile phones while driving translates into a substantially increased risk of an accidental collision.
Policy considerations
For the majority of tumours studied so far, a long latency period might exist, and the finding of any
link to the use of mobile phones is complex. Consequently, most of the published research cannot
elucidate the risk of long-term effects. If there is a risk, the current evidence suggests it is small.
Since there are still gaps in knowledge, continued research and better health risk analyses are needed.
Moreover, without scientifically recognized adverse effects on health, it is not possible to produce
evidence-based recommendations.
Therefore, a precautionary approach to the use of this communication technology should be adopted
until more scientific evidence on its effects on health becomes available. Such an approach includes
restricting exposure (according to existing guidelines and the European Union (EU) Directive) and
providing the public with information and options.
Introduction
In recent years, mobile telecommunication systems have grown significantly, to the point where more
than a sixth of the world’s population use mobile phones. By the end of 2004, more than a billion
subscribers across more than 200 countries were estimated to be using mobile phones (1, 2).
The development of mobile communications has moved rapidly. In the 1980s, first generation mobile
phones, using analogue technology, allowed the transmission of sound only. Digital transmission, and
the global system for mobile communication, started in 1991 and includes such new developments as
data and image transmission. Third generation mobile phones currently in the market offer additional
services to the users (such as fax, e-mail and Internet access). For both analogue and digital mobile
phones, the signals transmitted and received are in the form of waves in the radio frequency (RF)
(analogue) and microwave parts of the electromagnetic spectrum. RFs are non-ionizing radiation with,
wavelengths that range from 3 kHz to 300 MHz, and microwaves range from 300 MHz to 300 GHz1.
The frequencies that mobile phones and telecommunication networks use range from 900 MHz to
1.8 GHz and up to 2.1 GHz, although it should be noted that the wavelength of the different types of
mobile phones varies. This applies to both mobile phones and their base stations, which send and
receive calls.
People have welcomed the technology, as indicated by the widespread use of mobile phones, which
suggests that they do not perceive it as a potential health hazard. However, concerns about the possible
adverse effects on health, as a result of the exposure to RF and microwave electromagnetic fields, have
been expressed since the introduction of mobile phones.
Since the year 2000, several reports have reviewed relevant studies and summarized current
knowledge about mobile phones and health, particularly that related to the commonly accepted
carcinogenic effects of RF and microwave energy. The aim of this synthesis is to combine the
available epidemiological evidence, to learn whether exposure to RF and microwave radiation from
mobile phones and their base stations might affect health. This synthesis does not aim to analyse the
effect of other man-made sources of electromagnetic fields, nor does it aim to develop safety
standards. The WHO International EMF Project is currently producing this information (3).
Sources for this review
This synthesis assesses the clinical effects of day-to-day exposure to mobile phones in general
populations, such as communities – specifically, the impact on developing head and brain tumours
(benign and malignant). It also addresses other morbidity related outcomes and summarizes the
biological effects of RF and microwave radiation.
Two main sources of information were considered and reviewed. A search of scientific and biomedical
databases was performed until March 2006. Observational studies that assessed the effects of mobile
phones on general populations were included in the synthesis. Experimental studies that assessed
clinical effects were excluded, as were those of occupational settings. The quality of the studies was
assessed by using the grading system developed by the Scottish Intercollegiate Guidelines Network. Also, a review of documents and web sites of governments, health councils, radiological
protection boards, advisory and expert groups, and the like, was undertaken. Annex 1 gives details
about the literature search strategy.
Findings
Scientific literature
Biological and physiological effects
Experimental research on the biological effects of RF and microwave fields is very broad and includes
studies of volunteers, animals and in vitro, cell-based techniques (5, 6). The studies cover the effects
of RF and microwave radiation between 100 MHz and 60 GHz and focus both on the functional
changes in the brain (influence of exposure to RF and microwave fields on the head) and on
carcinogenic processes, reproduction and development, the cardiovascular system and longevity (as a
result of whole body exposure to RF and microwave fields).
The biological effects observed on the cardiovascular, endocrine and immune systems and on the
behaviour of animals studied seem to be thermal effects of acute exposure to RF and microwave
radiation, with increases of at least 1 °C or 2 °C in temperature needed to produce these effects. As to
the increased risk of developing cancer after exposure to RF or microwave fields, the evidence for
such an association is extremely weak. Since the radiation from mobile phones and signal stations
does not have enough energy to break chemical or molecular bonds directly, there is no basis in theory
to suggest that they can damage DNA. Moreover, a biological mechanism that explains any possible
carcinogenic effect from RF or microwave fields has yet to be identified. Because of the difficulties in
interpreting findings from laboratory studies, the hypothesis that RF or microwave radiation is harmful
and could have effects on health that have not yet been recognized cannot be rejected.
Indirect experimental results are difficult to extrapolate. In vitro experiments that show abnormal cell
proliferation, changes in cell membranes, and movement of ions and substances across membranes are
difficult to extrapolate to people. It is also difficult to extrapolate to people the observed effects on
cerebral functions that relate to the behaviour of rodents since, among other reasons, the whole brain
of these small animals is exposed to radiation whereas the brains of people who use mobile phones,
although being exposed, receive the highest exposure in the part closest to the handset. Moreover, the
thermal effects of radiation are unlikely to be seen in people, as the increase in the local temperature of
the brain induced by the microwaves generated by mobile phones is negligible (it has been estimated
to be up to 0.1 °C) (7). Finally, there is no evidence of non-thermal effects on human health.
It is important to distinguish between biological (or physiological) effects and psychological and
health effects. The demonstration of an RF or microwave radiation effect in experimental research
does not necessarily mean that such exposure will lead to harmful effects on human health. Human
bodies, with the aid of their immune, nervous or endocrine systems, can effectively resist some
external pressures, adapt to them and maintain the stability (homeostasis) disrupted by those changes.
Clinical effects
Within human population studies, epidemiological studies provide the most direct information on the
long-term effects on health of any potential harmful agent. To assess the adverse effects on health that
may result from the use of mobile phones, research with a specific focus on cancer has been carried
out. By the end of the 1990s, the number of studies was small and the works presented major
methodological limitations, the most outstanding one being the lack of enough people with an
exposure time long enough to accurately assess the potential adverse late effects on health of mobile
phone use.
The majority of those studies suggested the need for additional, high-quality research. As a result of
these recommendations, a series of multinational case-control studies, coordinated by the International
Agency for Research on Cancer (IARC), were set up after a detailed feasibility study was carried out
in 1998 and 1999.
Overall, these studies are named the INTERPHONE Study (8), and their primary objective is to assess
whether exposure to RF or microwave radiation from mobile phones is associated with a risk of
cancer. Priority is given to epidemiological studies of the relationship between the use of mobile
phones and the incidence of:
• brain tumours;
• salivary gland tumours, acoustic neuromas and other head and neck tumours; and
• leukaemia and lymphomas.
If the risk of developing a brain tumour exists at all, the wider use of mobile phones and the expected
number of people who will develop a brain tumour will be sufficient to detect a potential 1.5-fold
increase in risk 5–10 years from the start of use.
Participant countries, with the longest and highest use of mobile phones, are Australia, Canada,
Denmark, Finland, France, Germany, Israel, Italy, Japan, New Zealand, Norway, Sweden and the
United Kingdom. Initially, the study expected to find about 6000 cases of glioma and meningoma
(both benign and malignant), 1000 cases of acoustic neuroma, 600 cases of parotid gland tumour and
their respective controls. The first results of the INTERPHONE Study were available in 2004 (9, 10)
and, since then, four additional papers have been published (11–14). It should also be noted that these
studies evaluated the impact on health of exposure to RF and microwave radiation emitted by mobile
phones, and not by antennas and base stations.
With regard to brain tumours, most of the studies yielded negative results, although a few of them
suggested an increased risk for mobile phone users. Because of these results, it is not possible to
establish an association between the use of mobile phones and an increased risk of brain tumours.
With regard to acoustic neuroma – a rare, benign tumour on the auditory nerve – the studies available
reported inconsistent results, except for the most recent ones, which found an association between an
increase in the risk of this type of tumour and 10 years or more of mobile phone use; moreover, the
increased risk is confined to the side of the head where the phone was usually held. No indications of
an increased risk for less than 10 years of mobile phone use were found. Before definite conclusions
can be drawn, the results of these studies have to be confirmed by additional research.
This type of research, however, faces several problems. One is that long-time users first used analogue
phones, and then digital phones. No risk has been found for digital phone use only, but then the
follow-up time is shorter. Other methodological problems, such as recall bias, have been identified:
people, especially patients, might have a selective memory on the side of the head where the telephone
was used (15).
A number of clinical complaints related to the use of mobile phones are reported in the scientific
literature. They include headache, fatigue, sleep disorders, loss of memory, dizziness, feelings of heat
or tingling in the auricular (or auditory) area or in the head, vertigo, deafness and blurred vision. Very
few studies are available, and their results provide no evidence of an association between these
symptoms and the use of mobile phones. It should be noted, however, that these are general,
nonspecific symptoms that may be induced by a wide range of causes. Since they represent a problem
for those suffering, the cause should be elucidated.
In summary, the evidence available does not support the hypothesis that mobile phone use is
associated with an increased risk of malignant brain tumours, but an increase in the risk of acoustic
neuroma after 10 years or more of mobile phone use has been found. Therefore, it seems that neither
acoustic neuroma nor brain tumours are related to mobile phone use of less than 10 years.
Nevertheless, those studies were conducted with data from the time when only analogue mobile
phones had been in use for more than 10 years, and they cannot determine if the results would be similar after long-term use of digital mobile phones. Likewise, a carcinogenic effect after a very long
period of exposure would remain undetected.
The most important and clearly defined effect of mobile phones on health, and the only clearly
established risk from an epidemiological perspective, is motor vehicle accidents, which obviously are
not related to exposure to RF or microwave radiation. The results of some studies show that the use of
a mobile phone up to 10 minutes before a crash is associated with a fourfold increase in the risk of
having a collision that results in injury. The risk increases irrespective of whether or not a hands-free
phone is used (16, 17).
Table 2 describes the characteristics of the design of epidemiological studies and the outcomes of
these studies.
Reports (grey literature)
Since the year 2000, a significant number of reports and reviews on the connection between mobile
phone use and health have been issued by committees, institutions, expert groups and agencies of
worldwide prestige, to appraise relevant literature, draw up guidelines and make recommendations to
limit exposure to RF and microwave radiation.
The National Radiological Protection Board summarized (18) the information from several sources,
from the publication of the Stewart Report, in May 2000, to the end of 2004. The Board, an
independent body that is now part of the Health Protection Agency, has responsibility for advising
government departments and others in the United Kingdom on standards of protection for exposure to
ionizing and non-ionizing radiation, which includes electric and magnetic fields.
The Stewart Report (5) is a widely quoted review on mobile phones and health. The Government of
the United Kingdom commissioned the Independent Expert Group on Mobile Phones, which was
chaired by Sir William Stewart, to prepare the Report. The Report concluded that the balance of
evidence did not suggest that exposure below international guidelines could cause adverse effects on
health. However, it recommended that a precautionary approach – that is, limiting exposure to RF and
microwave radiation, planning the location and setting of base stations and encouraging a selective use
of mobile phones – be adopted until more detailed and scientifically robust information on any adverse
effects on health becomes available. Besides health issues, the Report offered advice on exposure
standards and planning to government, industry and others and on public information and consumer
choices. It also proposed setting up a research programme.
According to the National Radiological Protection Board summary report (18), most of the 26 reports
examined reached similar conclusions and made comparable recommendations. Overall, the reports
acknowledge that exposure to low-level RF and microwave fields may cause a variety of slight
biological effects on cells, animals or people, particularly on brain activity during sleep, but the
possibility of exposure causing adverse effects on health remains unproven. The reports also present
guidance on public policy to decision-makers and legislators, and some of them favour any form of
precautionary or prudent approach to reducing personal exposure to the fields produced by mobile
phones.
Specifically, most reports recommend limiting the use of mobile phones by children. This has been
recommended in the absence of explicit scientific data. However, ethical and practical concerns limit
or prevent experimental studies on children. Because of a much higher cumulative exposure than
today's adults when they were at the same age, children might be more vulnerable to any effects of RF
and microwave radiation. As long as adverse effects on health cannot be ruled out with some degree of
certainty, it appears to be appropriate to instruct children and their parents about a prudent use of
mobile phones. Moreover, in the absence of new scientific evidence, WHO is focusing attention on the
potential effects of exposure to electromagnetic fields on children (19). Finally, many reports agree
that the distraction caused by mobile phone use while driving represents a serious threat to health.
Table 3 contains a selection of national and international reports on mobile phone use and its effects
on health, along with the links to the corresponding web pages.
Discussion
Results among investigations were inconsistent, and these investigations indicated little or no
association between exposure to RF and microwave radiation and cancer. It should be noted that the
weak evidence on carcinogenicity obtained from several epidemiological studies applies only to the
type of cancer studied and to the time intervals observed between exposure and occurrence of disease.
Also, experience with cancer in people indicates that, in some cases, the period from first exposure to
the development of clinical cancer is seldom less than 20 years; moreover, latency periods
substantially shorter than 30 years cannot provide evidence for lack of carcinogenicity (20).
Progress and changes in mobile phone technology (such as analogue to digital signals) make it
difficult to assess exposure in the people studied. Furthermore, because the use of mobile phones is
relatively recent, it may be premature to conduct an exhaustive epidemiological assessment of its
impact on health. In the case of cancer, for example, the information available does not rule out the
possibility of an association between the use of mobile phones and the occurrence of this disease.
Thus, it is advisable to monitor the incidence of tumours supposedly associated with exposure to RF
and microwave radiation, to assess possible changes in trends.
Conclusions
The evidence available does not provide a clear pattern to support an association between exposure to
RF and microwave radiation from mobile phones and direct effects on health (such as increasing the
risk of cancer). However, the quality of this research and the relatively short-term data do not allow
ruling out adverse effects on health completely. In other words, the absence of evidence of detrimental
effects on health associated with mobile phone use is not evidence of absence of such effects. At the
moment, it is impossible to state that exposure to RF or microwave radiation (even below the
permitted levels) does not have adverse effects on the health of the general population. The current
evidence, however, does suggest that if there is a risk, it is small. Therefore, a precautionary approach
(as recommended by the EU (21)) to the use of this communication technology should be adopted
until more scientific evidence on effects on health becomes available.
Finally, evidence shows that the use of a mobile phone while driving translates into a significantly
increased risk of a traffic accident.
Annex 1. Sources of information and methods
Scientific and biomedical literature
The review was done after a bibliographic search (up to March 2006) of databases, using relevant key
words, selection (inclusion/exclusion) criteria and a grading scale.
Databases
The following databases were searched:
• MEDLINE
• EMBASE
• The Cochrane Library
• ENVIROLINE
• INSPEC
• PASCAL
• SCISEARCH.
Key words
The following keywords were used in the search: telephone, phone, cell phone, cellular phone, mobile
phone, cell telephone, cellular telephone, mobile telephone, antenna, station, hazards, risks, health
electromagnetic fields, radio waves, microwaves.
Selection criteria
The following inclusion and exclusion criteria were used in this synthesis:
• inclusion criteria: papers about the effects of RF from mobile phones and their base stations
on the general population published in English, French and Spanish.
• exclusion criteria: papers about the effects of RF from mobile phones and their base stations
in experimental studies and occupational settings; however, a summary of experimental
research findings is provided.
In an experiment, the exposition to the agent or putative cause is due because the investigator has
assigned the exposure to the subject in order to comply with a study protocol. Because the goals of the
study rather than the subject’s needs determine the exposure assignment, ethical constraints limit the
circumstances in which these types of studies are feasible. Experiments are ethically permissible only
when adherence to the scientific protocol does not conflict with the subject’s best interests.
Grading scale
The grading system used for the evidence is that developed by the Scottish Intercollegiate Guidelines
Network (SIGN) (4). Table 1 shows the SIGN levels of evidence for this system.
Grey literature
A review was undertaken of major documents and web sites of governments, health councils,
radiological protection boards, advisory and expert groups, and the like, since the year 2000.
Most of the epidemiological studies from which the reviewed evidence comes are case-control studies.
In case-control studies, subjects are selected according to their disease status (in the case of this synthesis, it was presence or absence of a brain tumour) and further classified according to their
exposure status (in the case of this synthesis, it was exposure to mobile phones). This type of design
provides mid- to low-level evidence, according to the grading system used (4), since the methodology
is less strong. Nevertheless, for the ethical reasons mentioned above, which relate to experimental
studies, cohorts – that is, studies in which subjects are classified according to their exposure status and
followed over time to ascertain disease incidence – and case-control studies are considered the best
designs to study potential risk factors for human health due to the inability to use intervention studies.
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