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/.
