November 1999

Cell Phones and the Risk of Brain Cancer

  1. Dr. Joshua Muscat reported the results of his study, on cell phones and the risk of brain cancer, at the Second State of the Science Colloquium sponsored by Wireless Technology Research in June, 1999. Information on self-reported cell phone history and billing information was collected from 466 men and women with brain cancer and 422 control subjects who were hospitalised for conditions other than brain cancer. The study found no correlation between cell phone use and brain cancer, nor was there any increase in risk with increased frequency or duration of cell phone use.

    This research has not yet been published in a peer-reviewed journal.

  2. 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/.

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