CSIRO - June 1994 BIOLOGICAL EFFECTS AND SAFETY OF EMR |
1.0 INTRODUCTIONA by-product of technological development is the recent rapid increase in environmental exposure to electromagnetic radiation, whether in the home, or in the workplace, or in public areas. The polluting signs of industrial development are visibly obvious air-borne or water-borne particles that obscure the air and clearly damage the environment. Electromagnetic radiation is even more pervasive and is unseen and unrecognised. Public concern is easily activated by a fear of the unknown. Terms such as “electromagnetic smog” have been coined which express concerns about its potentially polluting effects. Because of public community awareness and industry concern of the risk of litigation there is an apparent urgency to provide an answer to the question of safety of handheld mobile and cellular telephones . The use of these devices is unique in that the power transmitter is held against the head of the user. Media attention has focused on the legal claims for damages due to alleged cause of brain tumours. Public concern is aggravated by the appearance of multitudes of cellular transmitter antennas on towers adjacent to school playgrounds and on office buildings. Electromagnetic interference is already recognised as an important problem and work has begun to address issues on compatibility of electronic equipment. There are vital health issues associated with EM interference of medical equipment, but these are outside the scope of this document. Issues that are critical for an assessment of human health effects are: teratogenic, mutagenic, carcinogenic/tumour production, ophthalmic, immunologic and neurologic effects. There have been suggestions, based on some epidemiological studies at low (power line) frequencies that chronic exposure to EM fields may increase the risk of developing certain types of cancer. Although there has been no epidemiological study completed specifically addressing the higher frequency range used for telecommunications there have been some reports of increased incidence of tumours in animals exposed to microwaves together with a known carcinogen. However, there was a recent report of increased breast cancer in a very small group of female radio-operators on Norwegian ships (Tynes et al 1994) who were exposed to a combination of ELF and RF radiation. The recent legal claims in the USA that brain tumours may be caused by the use of digital cellular telephones has focussed the debate on the 450-915 MHz frequency. For the development of cancer to be a significant issue it requires critical changes in development of certain cells that can be detected with appropriate tests. There are two aspects to cancer development; the production of aberrant cells and the depression of the body’s natural immunological defences. Abnormal cell growth and behaviour may be detected as altered enzymatic activity, altered gene expression, peculiar growth patterns and changes in the ability of transformed cells to form colonies with in vitro tests. In cell biology, calcium plays an important role as a biochemical regulator that helps to relay signals from the cell surface (receptor site) to its interior. One effect of altered calcium function may be the increased activity of growth enzymes leading to uncontrolled cell proliferation and cancer. Therefore, research has focussed on this issue. Cells that are actively dividing are at the greatest risk of induced abnormalities, hence the bone marrow and blood-forming system and the developing central nervous system are considered to be the most sensitive targets. Claims of cancers in these biological systems have been associated with most forms of energy deposition. High rates of cell division occur in the development of sperm cells and effects could produce either tumours or abnormal cells with subsequent impairment of normal fertilization processes. The normal status of circulating lymphocytes, natural killer cells and macrophages is important in the control of disease processes, in general. Therefore, a number of studies has been directed towards the possible interference in the haematopoietic and immunologic systems by exposure to electromagnetic radiation. The cell membrane is considered to be sensitive to EMR interaction and, therefore, one would expect to see bioeffects in the immune response and gene expression. Research methodologies in medical and biological sciences have gradually evolved from studies of entire organisms or organ systems and tissues, cells and the molecules that comprise living tissue. The move away from reporting phenomenological effects on a gross scale in living tissues has presented a far greater challenge to scientists to understand the chemistry of molecular and sub-molecular composition and interactions. This has led to the emergence of a new field of science, bio-electromagnetics, that proposes that biological organisation is based on physical processes at the atomic level that regulate the products of biochemical reactions. Cells grown in culture exhibit characteristic abnormal behaviours and appearance that can be readily identified. The use of in vitro test systems allows manipulation of the environmental conditions in which the cells grow and provides an accepted vehicle for investigation of the mechanisms responsible for physiological and morphological abnormality. Animal models are also frequently used to identify potential carcinogens. The disadvantages of animal studies are that they are long-term, expensive, and results can be influenced by species or strain sensitivity to certain tumours. Mapping the in situ dosimetry in whole animals is far more complex than for in vitro exposures in radiation transparent cell chambers. The importance of animal studies is that they provide a complete biological system with which to evaluate the overall effect of subtle changes observed in cell systems. They allow closer relationship to the human’s whole organism physiology with the advantage that their environmental conditions can be controlled to isolate the effects of an individual physical or chemical agent. Clearly no single biological system will provide the answer to a problem as complex as the possible development of cancer from exposure to EMR. Any report, whether positive or negative, needs to be independently verified in a laboratory with similar scientific credentials before the result can become part of a reliable data base. Phenomenological approaches that report cause-and-effect events have limited usefulness. Predictions about safety can only be made with confidence when the responsible mechanisms are understood and demonstrated. The issue of safety of EMR in telecommunications is extremely important, socially and economically, however, it would be unrealistic to expect a definitive answer in the short term. The purpose of this CSIRO Report is to review the existing literature and identify issues that are directly relevant to human health. It includes conclusions on the current status of international research and make recommendations on the direction of future research.
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