CSIRO - June 1994
BIOLOGICAL EFFECTS AND SAFETY OF EMR

 

 

PREFACE

The CSIRO Report presents the current status of research on health effects of electro-magnetic radiation at frequencies relevant to telecommunications.

Because of constraints on time and resources, this report does not claim to be a comprehensive evaluation of the many hundreds of published papers and conference reports on the subject of biological effects of EMR. Rather than attempt to cover every aspect of biological effects research that has been published, it highlights what are considered to be important issues relative to human health. Because of the uncertainties in dosimetry and experimental procedures in many early studies this report has focused on relatively recent (within 10-15 years) studies to improve the chance of achieving consistency. There are a number of review articles that deal with pre-1980 research.

The CSIRO Report has been prepared in a way that will allow it to be read and understood as a single entity. Thus, it includes supporting information (in text and table format) for the summary statements thereby obviating the need to refer to other reference texts except for detailed information. The bibliography is provided as a means of identifying sources of information and a data base is being compiled. However, it should not be taken that this list is either comprehensive, or that every report has been scrutinised for its scientific validity. It was considered to be ethically appropriate to make comment on issues and to try to avoid overt criticism of publications that have presumably already passed some scientific peer-review process. Much of the recent data that was presented at the BEMS conference is not published in peer review journals and was not reviewed for acceptance at the conference. The relevance of certain fields of study has been questioned in some instances.

This CSIRO Report on the status of research on biological effects and safety of electromagnetic radiation was prepared by the Division of Radiophysics. A contribution to the cost of this project was provided by Spectrum Management Agency.

SCOPE OF REPORT

The possible adverse effects on human health of exposure to radiofrequency (RF) and microwave electromagnetic fields and radiation are of public concern. As the ambient electromagnetic environment continues to intensify (e.g. cellular and portable phones, wireless communications, LANs, PCNs) the effects of exposure from cumulative sources and prolonged exposure to low levels needs to be addressed. Advice is based on the assessment of risks to health resulting from these exposures as derived from studies on the effects of RF radiation on animals and volunteers and from epidemiological studies of exposed populations. This review considers RF and microwave radiation above 100 kHz. It is acknowledged that there are several possible areas of biological interaction which have health implications and about which current knowledge is limited.

The CSIRO Report draws information from: major reviews by scientific bodies (EPA 1984; NCRP 1986; NRPB 1991; NRPB 1992; NRPB 1993; WHO 1993), and the extensive scientific literature; interviews with prominent scientists in the USA, UK, Europe and Australia; interviews with government agency representatives in the USA and UK. Information was also obtained through attendance at the conference of the Bioelectromagnetic Society, 1994. The CSIRO Division of Radiophysics research program includes investigation of the biological effects and safety of microwave radiation. The CSIRO Report was prepared with support and resources provided by the Division of Radiophysics and a financial contribution from Spectrum Management Agency. Contributions from the Australian Radiation Laboratory constitute sections 11 and 12 of the report on dosimetry and epidemiology.

Because of the lack of information on the responsible mechanisms it is difficult to ignore the effects at low frequencies when reviewing the literature on frequencies used for telecommunications. However, this is beyond the scope of this report.

Microwave and Radiofrequency Radiation

This report refers to microwave and RF radiation. Microwave radiation borders on the optical part of the non-ionizing electromagnetic spectrum, ranging in wavelength between 1 mm (300 GHz) and 1 metre (30 MHz). Most of the animal experiments have been carried out at commonly used frequencies such as 27, 915, or 2450 MHz. Exposure are often carried out in the far-field (at distances greater than one wavelength from the antenna), where the magnetic and electric components of the radiation are in-phase. Assessment of applied dosimetry is relatively straightforward compared to near-field conditions (as applied in the use of cellular telephones) although in situ tissue dosimetry is not fully understood. Radiofrequency radiation encompasses the microwave region and additionally extends to ELF frequencies where pulse modulation systems are employed.

Sources of human exposure to RF and microwave radiation include microwave communication links, radar, radio and TV transmitters and domestic microwave ovens. The strongest RF fields likely to be encountered by members of the public are those used in clinical magnetic resonance diagnosis which may involve patient exposure for short periods (less than 1 h) at whole-body SARs of up to about 4.0 W/kg.

RF and microwave radiation emits a waveform as oscillating electric fields (measured in volts per metre, V/m) and magnetic fields (amperes per metre, A/m). The intensity (or power flux density) of a beam of radiation is expressed in watts per square metre (W/m2), equal to the product of the electric and magnetic field strengths. The rate of absorption of energy by biological tissue in animals or humans is conventionally described in terms of the specific energy absorption rate (SAR) expressed in watts per kilogram (W/kg) for the whole body or parts of the body. The time-integral of this (watts multiplied by seconds, per kilogram) gives the specific energy absorption in joules per kilogram (J/kg).


 

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