A
study from Sweden examined 209 people with brain tumours and
compared them with 425 control subjects. Exposure
to cell phone use and to other radiofrequency sources was assessed
by questionnaire, and by follow-up telephone interviews in some
cases. Of the people examined, 78 (37.3%) brain tumour patients
and 161 (37.9%) participants from the control group reported
cell phone use. The research found no association
between the occurrence of brain tumours and cell phone use or
between the occurrence of a tumour and the duration of cell
phone use.
The study found a "somewhat increased risk,"
which was not statistically
significant, for tumours in the temporal
or occipital lobe
of the brain that appeared on the same side of the head the
cell phone was used. The greatest RF exposure from cell phones
occurs in these areas of the brain. The "somewhat increased
risk" was found only for users of the analogue NMT system.
The risk increased 2.56 times for the right side of the head
and 2.10 for the left side. However, the calculations were
only based on 7 cases for the right and 5 cases for the left.
The authors state that due to the low numbers "the results
must be interpreted with caution." For digital GSM use the
observation time was too short for definite conclusions.
Muscat's study reported a low/moderate correlation between
the location of the tumor on the brain and the side of the
head the cell phone was used. Again this was not statistically
significant.
The study found 13 cases of acoustic
neuroma. In these instances, the prevalence of cell phone
use was less than the control group and only one case had
the tumour on the same side of the head as the cell phone
was used.
The main weakness of this study, as with most case-control
studies, is that it might be subject to recall bias
(i.e., it is more likely that people with a brain tumour remember
past cell phone use, as opposed to those in the control group).
The authors state that "validation of exposure to cellular
phones from telephone companies would have been desirable.
However, it turned out to be impossible to get such data."
Reference:
Hardell L, Nasman A, Pahlson A, Hallquist A, Hansson Mild
KH (1999). Use of cellular telephones and the risk of brain
tumours: A case-control study. Int J Oncol 15: 113-6.
Note:
A further question about this study is reported in Microwave
News, July/August edition, 1999. Dr. Maria Feychting of Karolinska
Institute in Stockholm comments that Hardell's study should
have included many more cases than it did. Feychting identified
862 cases of brain cancer from the study area, while Hardell
only identified 270. Some of the differences may be due to
the fact that Hardell only included cases that were still
alive, although Feychting estimated that about two thirds
of the 862 cases should have been still alive.
A Critical Review of Epidemiological
Studies
Elwood provides an extensive review of epidemiological
studies of radiofrequency exposure and human cancer. The review
concentrates on studies published during the years 1988 to
June 1998, and includes those where the main exposure was
radiofrequency radiation.
Four groups of studies were reviewed: Studies of clusters
of cases (three studies); studies of general populations exposed
to TV, radio and, similar emission (five); studies of occupational
groups with exposures to such emissions (five), and case-control
studies (six). None of these studies deals specifically with
cell phones or transmitters.
Elwood concluded that "the epidemiologic evidence falls short
of the strength and consistency of evidence that is required
to come to a reasonable conclusion that RF emissions are a
likely cause of one or more types of cancer."
Reference:
Elwood JM (1999). A critical review of epidemiologic studies
of radiofrequency exposure and human cancer. Environ Health
Perspect 107 (Suppl 1): 155-168.
A Review of Cell Phones and Cancer
Moulder and his colleagues review the literature on cellular
and animal studies as well as epidemiological studies. They
report that the epidemiological evidence for an association
between RF radiation and cancer is "weak and inconsistent,"
and that the laboratory studies do not suggest that cell phone
RF radiation causes adverse effects on genes or cancer-promoting
effects.
Reference:
Moulder JE, Erdreich LS, Malyapa RS, et al. Cell phones and
cancer: what is the evidence for a connection? Radiation Research
1999;151:513-531.
Negative Effects of Radiofrequencies
on Central Nervous System Tumours in Rats
This study exposed rats to a radiation within the cellular
phone range. The animals used in the study spontaneously develop
brain tumours at an increased rate, and were also subjected
to a dose of a chemical ethylnitrosurea - a cancer-promoting
agent, during fetal life. Intermittent digital-phone field
exposure was continued for 24 months, and was designed to
simulate maximum exposure to localised areas of the brain
in a cell phone user. The exposed animals were compared to
controls.
The study indicated no evidence that the exposed groups developed
more tumours than the non-exposed groups. The authors state
that there was a trend toward increased survival in animals
exposed to microwaves. This was due to a decreased incidence
of brain tumours in the exposed group. However, the number
of animals affected was small, and the results were not statistically
significant.
Reference:
Adey WR, Byus CB, Cain CD, Higgins RJ, et al. Spontaneous
and nitrosurea-induced primary tumours of the central nervous
system in Fischer 344 rats chronically exposed to 836 MHz
modulated microwaves. Radiation Research 1999;152:293-302
Current or Planned Research in Humans
Studies that are ongoing include the following:
The National Cancer Institute of the USA: This is a
case-control study of approximately 800 cases of brain tumour
(glioma, acoustic
neuroma, and meningioma),
and a similar number of controls. Exposure to cellular telephones
will be assessed by questionnaires.
International
Association of Research on Cancer (IARC): This agency
plans to coordinate an international case-control study, which
will examine a variety of malignant tumours. Participating
countries will likely include Australia, Canada, Denmark,
Finland, France, Israel, Italy, Sweden and the UK. Cellular
telephone company records will be used to assess exposure.
Denmark:
A cohort study is expected to produce results in 2000. Data
from telephone company records from 1981-1995 are being linked
with cancer registry and death registry information. Cases
of brain cancer, salivary gland cancer, and leukaemia are
being identified amongst 800,000 individuals followed.
Human
laboratory studies: A large number of studies are planned
or ongoing. These examine whether or not exposure to RF in
the cellular phone range has an effect on parameters such
as behaviour, hormonal patterns, and brain activity. Details
of these studies can be found at www.who.int/peh-emf/.
