THE NATIONAL MEDICAL JOURNAL OF INDIA
VOL.
15, No.5,
275
2002
Cellular phones and their hazards: The current evidence
ANUS HEEL MUNSHI,
RAKESH JALALI
ABSTRACT
The past decade has seen an exponential increase globally in the
use of cellular phones (popularly known as mobile or cell
phones). These phones are convenient and trendy. Discarding
the wire means that the communication is through electromagnetic waves, which could have potential hazards. Alarmist reports
in the lay press and high profile lawsuits, particularly in the West,
have attracted attention to the possible harmful effects of cellular
phones. Adverse effects investigated by various clinical trials
include the possible link to increased risk of vehicular accidents,
leukaemias, sleep disturbances and the more serious brain
tumours. Available level II evidence suggests that the only proven
side-effect is an increased risk of vehicular accidents. So far, all
studies have consistently negated any association between cellular
phones and brain tumours. Yet, the final word remains to be said.
Natl Med
J India 2002;15:275-7
INTRODUCTION
Cellular phones are normally held against the ear during a phone
call and do not use landlines. These need to be distinguished from
cordless telephones which operate at a lower frequency and power
and, therefore, are not classified as a type of cellular phone. IWhile
the basic concept behind cellular technology has existed since
1947, the Federal Communications Commission in the USA
delayed its development until 1982. A prototype cellular system
was constructed and operated by AT&T Bell Laboratories in 1977
and the first commercial cellular phone system began operations
in Tokyo in 1979. Initially, cellular phones were installed in cars
or were generally large handheld units. The past decade has seen
tremendous technological innovations which have made cellular
phones as common as conventional telephones in several parts of
the world. A similar revolution in their use is taking place in India,
especially in urban areas. It has been estimated that more than 500
million people in the world are currently using pocket-sized
cellular phones.'
WHY STUDY CELLULAR PHONES?
The potential hazards of cellular phones were brought to light in
1993, when a man in Florida filed a lawsuit claiming that his
wife's cellular phone had caused her brain tumour. Since then, the
possible causal role of cellular phones in the development of brain
tumours has been a subject of intense study. Probing into the
adverse effects of cellular phones is important because of their
rapid use especially among the young. Consequently, there is a
need to analyse long term effects as good and reliable evidence
(level I) is still not available.
Tata Memorial Hospital, Parel, Mumbai 400012, Maharashtra, India
ANUS HEEL MUNSHI, RAKESHJALALI
Department of Radiation Oncology
Correspondence
to RAKESH JALALI; [email protected]
© The National Medical Journal of India 2002
BASIS OF HARMFUL EFFECTS
Cellular phones work on the principle of communicating through
microwaves, typically of 1000 MHz frequency. Microwaves are a
form of electromagnetic radiation which have a large spectrum,
with gamma rays at one end and radio waves at the other.
Radiation from X-rays and gamma rays are well known to cause
harmful effects because of their ionizing properties. Microwaves
lie between the radio waves and infrared region of the electromagnetic frequency spectrum. It has not yet been proven if microwaves
have any ionizing potential. However, it has been postulated that
they may produce some effects due to generation of heat locally,
direct genotoxic effects and through some other unknown mechanisms.
The extent of exposure to radiofrequency radiation from a
cellular phone depends on the power of the signal the device
transmits, duration of its use and the distance ofthe critical part or
organ from the emitting source (this may be an important consideration in children whose skull bones are thinner). While using a
cellular phone, the head of the user is in the near- field of the source
because the distance from the antenna of the phone to the head is
only a few centimetres. The energy emitted by cellular phones
produces minimal local heat in the brain (about 0.1 0C).3Most
people use phones on the same side and against the same spot over
the pinna. Heavy users may, therefore, have exposures of up to
several hours a day. It is not known as yet if these effects are
cumulative as with ionizing radiations."
A literature review reveals that cellular phones have been
implicated in causing several adverse effects such as brain tumours
and leukaemias and more benign ones such as vehicular accidents, headache, psychological effects, sleep disturbance and
pacemaker dysfinction (Table I).
MALIGNANT EFFECTS
All studies reported so far have been case-control studies and
therefore retrospective (Table II). One of the foremost studies
reported was by Hardell et al.5 among the Swedish population,
which happens to be one of the heaviest users of cellular phones
in the world. People diagnosed with brain tumours, between 20
and 80 years of age and still alive, were studied retrospectively.
Seventy-eight cases (37.3%) among brain tumour patients reported using cellular phones as compared to 161 controls (37.9%)
who did not have brain tumours. However, the alarming fact was
that there was a marginal increased risk for cases with right-sided
brain tumours who used the phone on their right ear (odds ratio
TABLE1. Conditions suspected to be associated withcellular
phone use
Benign
Malignant
Motor vehicle accidents
Headache
Sleep disturbance
Behavioural changes
Brain tumours
Leukaemias
THENATIONAL
MEDICALJOURNALOF INDIA
276
TABLEII. Trials of cellular phone use and brain tumours
Study (year)
Subjects
Hardell et al.' Cases 78
Controls 161
(1999)
Inskip et al"
(2001)
Cases 782
Controls 799
Muscat et al.' Cases 469
(2000)
Controls 422
Johansen et al.8 420 095 cellular
(2001)
telephone users
Result
Shortcomings
Insignificant
Small number of
subjects
Bias of case-control
studies
No objective exposure measurement
Dependent on
patients recall
Retrospective study
with bias
Based on questionnaires
increase in brain
tumours on the
sideofuse
No significant
difference in
relative risk for
brain tumours
No significant
difference in use
in two groups
No increase
in brain
tumours
Based on cellular
company data
No actual controls
1.28, CI: 0.68-2.38). The authors concluded that an insignificant
increased risk for brain turnours located in the temporal or occipital lobe was found in people who had held a cellular phone on that
side of the head.
The most recent and perhaps the most important study was from
the National Cancer Institute (NCI).6In this study done from 1994 to
1998, 782 patients with brain tumours and 799 controls were
compared for average daily use, duration of regular use, cumulative
use and the total years of use. The control population consisted of
patients admitted to the same hospitals with non-neoplastic conditions such as circulatory disorders, trauma, etc. The relative risk (RR)
associated with cumulative use of the cellular phone for more than
100 hours were 0.9 for glioma, 0.7 for meningioma, 1.4 for acoustic
neuroma and 1.0 for all types of tumours combined. No difference in
RR was found for any tumour subtype. Also, tumours did not occur
disproportionately often on the side of head on which the phone was
usually used. It was concluded that there was no evidence that the risk
of developing brain tumour was higher among those who used
cellular phones for 360minutes per day or regularly for 35years.
This study had a few drawbacks. The assessment of exposure
relied on interviews with patients (who had been operated for
brain tumour) rather than on an objective measurement. The
sample size was not large enough to exclude a small increase in the
risk of brain tumours in general and larger increases in the risk of
tumours in certain anatomical sites or of certain histological
SUbtypes. The study dealt with subjects using analogue phones
which emit microwaves in pulses instead of the currently used
digital phones in which these waves are emitted continuously.
Most of the patients in the study were recent cellular phone users
and so the study could not have analysed the late effects of the use
of these devices. Subjects < 18years of age were excluded whereas
this group is one of the heaviest users and in whom the late effects
would be of particular importance.
The correlation between the duration of cellular phone use and
the development of brain tumour has also been investigated.' A
case-control study reported median monthly use of2.5 hours for
a median duration of2.8 years for cases and a median monthly use
of 2.2 hours for a median duration of 2.7 years for controls,
respectively. No association with brain tumours was observed
related to the duration of use (p=0.54). A large, nationwide survey
in Denmark also failed to show any increase in the incidence of
brain tumours and other cancers with the use of cellular phones,
although the study lacked controls." Cellular phone use has also
been investigated in the causation of specific tumour types such as
VOL. 15, NO.5, 2002
acoustic neuromas? and malignant melanomas 10 of the eye with no
clear increase in their incidence.
While the fear that the use of cellular phones causes brain
tumours appears to be ill-founded, at least for the time being, it
certainly requires more prospective studies with a larger cohort of
subjects. The International Agency for Cancer (IARC) is currently
launching a multinational case-control study of brain tumour and
its relation to cellular phone use. The study will include about
6000 cases from 13 countries. The results are likely to be available
around 2004. Another recently launched multicentric study is
designed to assess the risks associated with long induction periods
and use of cellular phones. 11These results will be applicable to the
currently used digital phones.
Another concern in cellular phone use is the possible link
between cellular phone use and the development of leukaemia. No
study has examined the direct relationship of leukaemia with
cellular phone use. However, studies implicating radiofrequency
(RF) waves have been reported. Hocking et al:'? reported an elevated incidence of leukaemia in populations residing in municipalities near television towers with obvious radiofrequency exposure than in populations living away, although RF radiation exposures were actually not measured. In 1998, another group repeated
the work in the same location and made more accurate estimates of
the exposure to RF radiation people might have received." No
significant correlation between RF exposure and the rate of childhood leukaemia was established in this study, which concluded
that much of the excess childhood leukaemia reported by an earlier
study occurred before high-power broadcasting had started and
could have been because of erroneous interpretations.
Since the inverse square law influences the exposure in electromagnetic radiation including microwaves, the distance of the
cellular phone from an indi vidual's head or body could also play
a role in the occurrence of adverse effects. Cellular phones are
handheld and therefore kept close to the head. However, nonhandheld phones (car phones, bag phones) are also available. One
of the largest studies reported so far evaluated nearly 300 000
users of handheld and non-handheld telephones in several American cities. 14Theinvestigators found no difference in overall cancer, leukaemia or brain tumour rates between the users of hand held
portable phones and the users of cellular phones.
BENIGN EFFECTS
Vehicular accidents, as a by-effect of cellular phone use has been
an area of active investigation. One hypothesis proposes that
talking while driving could adversely affect the reaction time of
the driver and hence impair his/her ability to avoid an accident.
Redelmeier et al. 15studied 699 drivers who used cellular phones
and were involved in motor vehicle collisions. They found that the
risk of a collision using a cellular phone was 4 times higher than
the risk when a cellular phone was not being used (RR: 4.3; 95%
CI: 3.0-6.5). Phones that allowed hands-free use (RR: 5.9) offered
no safety over handheld ones (RR: 3.9; p not significant). However, the study dealt with minor traffic accidents only and it is
possible that the relationship between cellular phone use and
serious accidents may be different. Another large study comparing
handheld and non-handheld phone users showed an increase in
the motor vehicle collision and mortality with no difference
between the two groups. 14
Electromagnetic radiation can interfere with the functioning of
many electronic gadgets. This may become critical with devices
such as cardiac pacemakers. It has not been proven that cellular
phones interfere with cardiac pacemakers or other implanted
MUNSHI, JALALI:
277
CELLULAR PHONES AND THEIR HAZARDS
medical devices as long as exposure levels are kept within the
guidelines. However, it is possible that digital cellular phones
might interfere with pacemakers if they are placed directly over the
pacemaker. 16
Headaches have also been reported in cellular phone users.":"
In a cross-sectional community study, headaches were noticed to
be significantly more common among users of handheld cellular
phones than among non-users (65% v. 54%).19The prevalence of
headache has been shown to increase significantly with duration
of use, and the use of hands-free equipment eliminated this
increase. 19,20
However, the exact time of onset, duration and acute
and chronic effects of headaches need to be clarified. Cellular
phone use triggering a migraine attack has also been speculated
but remains largely unproven.
Braune et al. 21reported that human volunteers using a cellular
phone for 35 minutes showed a 5-10 mmHg rise in blood
pressure. The study was small and not blinded, and a rise in
blood pressure of this magnitude is unlikely to have any major
health consequences. There have been unreplicated reports of
physiological or behavioural changes from RF radiation of
handheld cellular phones. Exposure to a cellular phone signal at
0.05 mWzcm? has been demonstrated to cause slight changes in
sleep patterns but subsequent studies by the same group found
no significant effect when the power density was lowered to 0.02
mW/cm2.22.23
Based on the available epidemiological evidence, the main
public health concern clearly proven to be a result of cellular phone
use is motor vehicle collisions. However, it appears to be a
behavioural effect rather than a direct effect of exposure to electromagnetic radiation per se.
REDUCING THE RISK
The Federal Drug Authority (FDA) of the USA has stated that it
cannot conclude whether cellular phones are safe or not, but so
long as it is not certain that there are no ill-effects, future research
must continue. The FDA, however, does set limits to the amount
of radiation a phone can emit. We feel that even a small increase
in risk may have large implications for public health, as the use of
cellular phones and the exposure related to their use is likely to
increase rapidly in the future. While it may be premature to lay
strict guidelines on the basis of current evidence, the following
recommendations may be useful especially for heavy users:
1. Use a hands-free set, which would reduce exposure in accordance with the inverse square law governing electromagnetic
radiation;
2. Alternate phone use between right and left ears;
3. Avoid speaking for long periods on the cellular phone;
4. Plan calls so that ordinary phones are used for long conversations;
5. Use a plug-in earpiece.
In summary, the evidence regarding the use of cellular phones
vis-a-vis health hazards is largely reassuring. No serious effects
other than vehicular accidents have been proven so far. However,
caution needs to be observed till the final verdict is delivered.
While the evidence to link cellular phones to malignancies is
weak, results from large ongoing studies are awaited.
ACKNOWLEDGEMENT
We would like to acknowledge
Mumbai.
the support of Brain Tumour Foundation,
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