Electromagnetic waves from the lower radio frequencies up through the optical spectrum can generate a myriad of effects and responses in biological specimens. Some of these effects can be harmful to man at high radiation intensities, producing burns, cataracts, chemical changes, etc. Biological effects have been reported at lower radiation intensities, but it is not now known if lowlevel effects are harmful. Even behavioral changes have been reported. Most of the effects are not harmful under controlled conditions, and can thereby be used for therapeutic purposes and to make useful diagnostic measurements. The problem of microwave penetration into the body with resultant internal power absorption is a p proached from both the theoretical and the experimental viewpoints. The results are discussed in terms of therapeutic warming of tissues and possible hazards caused by internal "hot spots." The absorption and scattering effects of light in biological tissues are reviewed. Molecular absorption peaks in the optical spectrum are useful for making molecular concentration measurements by spectroscopy. Much of the related work in the literature is summarized, some new results are presented, and several useful applications of wave energy and medical instruments are di scussed. Mi I. INTRODUCTION EALTH OFFICIALS and medical personnel have recently been confronted with several problems associated with wave propagation effects in tissues and living systems such as man. They have turned to the engineering profession for help, but have found engineers generally unable to provide the needed guidance. Physiologists and biologists have attempted to fill this void, with results that clearly demand an informed engineering critique. I t seems curious indeed that although some of the early fundamental experiments with light and electromagnetic waves were performed over 100 years ago, the application of these energy forms to man himself is pitifully inadequate. This .paper is presented in an attempt to define the overall problem in some small measure, and illustrate the new applications methodology and techniques. It quite frankly represents an attempt to stimulate the engineering profession to respond to this urgent medical and social need. The paper consists of two basic parts. Section I1 describes electromagnetic radiation from, say, 1 MHz to 300 GHz, where the wavelength is large compared to cell sizes. There is little scattering, thus most of the wave reflection and transmission line concepts are applicable. Section I11 describes invited paper is om of a series planned on tap& of general inUTest-Tk Manuscript received February 24, 1972; revised March 20, 1972. This E d h. Facilities and administrative supporf for the research described were provided by Social Rehabilitation Service Research and Training Grant l&P-56818/0-09; Bureau of Radiological Health Grant 8-R01

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As part of a comprehensive investigation of the potential genotoxicity of radiofrequency (RF) signals emitted by cellular telephones, in vitro studies evaluated the induction of DNA and chromosomal damage in human blood leukocytes and lymphocytes, respectively. The signals were voice modulated 837 MHz produced by an analog signal generator or by a time division multiple access (TDMA) cellular telephone, 837 MHz generated by a code division multiple access (CDMA) cellular telephone (not voice modulated), and voice modulated 1909.8 MHz generated by a global system of mobile communication (GSM)-type personal communication systems (PCS) cellular telephone. DNA damage (strand breaks/alkali labile sites) was assessed in leukocytes using the alkaline (pH>13) single cell gel electrophoresis (SCG) assay. Chromosomal damage was evaluated in lymphocytes mitogenically stimulated to divide postexposure using the cytochalasin B-binucleate cell micronucleus assay. Cells were exposed at 37+/-1 degrees C, for 3 or 24 h at average specific absorption rates (SARs) of 1.0-10.0 W/kg. Exposure for either 3 or 24 h did not induce a significant increase in DNA damage in leukocytes, nor did exposure for 3 h induce a significant increase in micronucleated cells among lymphocytes. However, exposure to each of the four RF signal technologies for 24 h at an average SAR of 5.0 or 10.0 W/kg resulted in a significant and reproducible increase in the frequency of micronucleated lymphocytes. The magnitude of the response (approximately four fold) was independent of the technology, the presence or absence of voice modulation, and the frequency (837 vs. 1909.8 MHz). This research demonstrates that, under extended exposure conditions, RF signals at an average SAR of at least 5.0 W/kg are capable of inducing chromosomal damage in human lymphocytes.

After 45 min of exposure to pulsed 2450 MHz microwaves (2 microseconds pulses, 500 pps, 1 mW/cm2, average whole body SAR 0.6 W/kg), rats showed retarded learning while performing in the radial-arm maze to obtain food rewards, indicating a deficit in spatial "working memory" function. This behavioral deficit was reversed by pretreatment before exposure with the cholinergic agonist physostigmine or the opiate antagonist naltrexone, whereas pretreatment with the peripheral opiate antagonist naloxone methiodide showed no reversal of effect. These data indicate that both cholinergic and endogenous opioid neurotransmitter systems in the brain are involved in the microwave-induced spatial memory deficit.

The dielectric properties of various test samples of phantom tissue were measured using an automated and temperature-controlled slotted line. The ingredients for phantom materials were determined for simulating high-water content tissue at 13.56, 27.12, 40.68, 70, 100, 200, 300, 433, 750, 915, and 2,450 MHz. The ingredients consisted of water, TX-150 (a gelling agent), sodium chloride, and polyethylene powder (200-2,450 MHz) or aluminum powder (13.56-100 MHz). The dielectric constant and conductivity of these materials at different temperatures (15, 22, 30 degrees C) were characterized.