A discussion of potential exposure metrics for use in epidemiological studies on human exposure to radiowaves from mobile phone base stations

There is currently it high level of concern in many countries that exposure to radiowaves from mobile phone base stations may be hazardous to health, When investigating such suggested risks, epidemiologists need to define an exposure metric that can reliably discriminate between exposed and unexpose d groups of people. We conducted a feasibility study to investigate if eith er short-term measurements of electric field strength, calculations of elec tric field strength, or distance from nearby mobile phone base stations cou ld be used to develop a metric reflecting an individual's exposure to radio waves. With electric field strengths in the range of 0.012-0.343 V/m, radio waves from mobile phone base stations were found to give a material contrib ution to total exposure; however. stronger signals were frequently measured from other sources such as broadcast radio and television transmitters. Th eoretical considerations and the measurements made during this work demonst rated that studies at the population level on suggested adverse effects of radiowaves from mobile phone base stations are not feasible since no valid metric for estimating historical exposures is currently available. The pace of radio infrastructure development is also such that today's measurements am unlikely to be good proxies for either past or future exposures. The co mplex propagation characteristics affecting the beams from base station ant ennas include shielding effects and multiple reflections from house walls a nd other buildings. These factors, combined with the presence of other envi ronmental sources of radiowaves, cause distance from a base station to be a poor proxy for exposure to radiowaves indoors. It may be possible to adapt computer models developed by network providers to predict network coverage for epidemiological purposes; however, this has yet to be investigated. Fu rthermore, there is little evidence that presently justifies epidemiologica l studies being restricted to adverse effects of radiowaves from mobile pho ne base stations while neglecting radiowaves at other frequencies produced by different transmitters.