Biological Correlates of Low-Level Electromagnetic-Field Exposure

Biological effects of electromagnetic-field exposure have been a subject of continuing concern for a number of reasons. The effects have been broadly divided into two parts: thermal and nonthermal, though the demarcation between the two is not well defined. Recently, a large amount of experimental data has accumulated, indicating a variety of biological effects much below the accepted criteria for safe exposure. The biological effects, which may or may not involve health implications, are many. This includes the blood-brain barrier, ornithidine decarboxylase, the role of Ca2+, melatonin, DNA strand breakage and free-radical formation. Some of these parameters are often implicated in tumour promotion. Propagation of the signal through plasma membrane has raised questions regarding the modality of its amplification. While a number of mechanisms have been proposed (e.g. stochastic resonance, cooperativism, etc.), they may be active separately or in unison to bring about the desired amplification and control the cellular function. The formulation for setting the criteria for safety standards then needs further scrutiny, particularly for health risks from microwave exposure from wireless communication. The role of other exposure parameters, such as frequency, modulation, polarization and intermittence of exposure, may also be considered. This then suggests the necessity to have a re-look at the concept of specific absorption rate (SAR) defining dosimetry and criteria for safety standards. The possibility of application of cross fields to restrict the formation of free radicals, and possibly cancer promotion, is also presented. Keywords: electromagnetic field; mobile phone; dosimetry; biomarkers; infertility; stochastic resonance; tumour promotion; DNA strand break; free-radical formation; calcium efflux