Chung-Kwang Chou

Assessment of cellular telephone and other radio frequency exposure for epidemiologic research

Epidemiologists are now embarking on the evaluation of the hypothesis that exposure to radio frequency energy from low-power wireless communication devices, such as portable cellular telephones, causes brain cancer and other adverse health outcomes. Even in the laboratory, exposures from radio frequency sources are difficult to quantify; their measurement in large populations for epidemiologic study is challenging. In this paper, we outline the nature and magnitude of these exposures and discuss the prospects for obtaining useful measures of exposure for epidemiologic research.

Auditory perception of radio‐frequency electromagnetic fields

Absorption of pulsed microwave energy can produce an auditory sensation in human beings with normal hearing. The phenomenon manifests itself as a clicking, buzzing, or hissing sound depending on the modulatory characteristics of the microwaves. While the energy absorbed (∠10 μJ/g) and the resulting increment of temperature (∠10−6 °C) per pulse at the threshold of perception are small, most investigators of the phenomenon believe that it is caused by thermoelastic expansion. That is, one hears sound because a miniscule wave of pressure is set up within the head and is detected at the cochlea when the absorbed microwave pulse is converted to thermal energy. In this paper, we review literature that describes psychological, behavioral, and physiological observations as well as physical measurements pertinent to the microwave‐hearing phenomenon.

An efficient RF exposure system with precise whole-body average SAR determination for in vivo animal studies at 900 MHz

A radial electromagnetic cavity has been designed and optimized for the in vivo whole-body exposure of mice to 900-MHz RF fields. Parallel circular plates shorted around the perimeter form the cavity, which is fed at the center in order to excite a cylindrical TEM wave. Plastic housings allow the insertion and equidistant positioning from the exciter of 40 mice, with the electric field parallel to the body axis. The resulting exposure system is highly efficient, featuring more than 80% of the incident power dissipated in the mice. The whole-body average SAR can be determined with remarkable precision by means of straightforward power balance since the RF power leakage from the cavity is extremely low. Fairly uniform exposure of the mice, individually and collectively, has been achieved by means of the symmetric arrangement. This exposure system has been adopted in a replication study on transgenic mice currently being carried out in South Australia, and is being considered for upcoming animal studies in Europe.

Simulation of exposure and SAR estimation for adult and child heads exposed to radiofrequency energy from portable communication devices

Abstract Bit-Babik, G., Guy, A. W., Chou, C-K., Faraone, A., Kanda, M., Gessner, A., Wang, J. and Fujiwara, O. Simulation of Exposure and SAR Estimation for Adult and Child Heads Exposed to Radiofrequency Energy from Portable Communication Devices. Radiat. Res. 163, 580–590 (2005). The level and distribution of radiofrequency energy absorbed in a childs head during the use of a mobile phone compared to those in an adult head has been a controversial issue in recent years. It has been suggested that existing methods that are used to determine specific absorption rate (SAR) and assess compliance with exposure standards using an adult head model may not adequately account for potentially higher levels of exposure in children due to their smaller head size. The present study incorporates FDTD computations of locally averaged SAR in two different anatomically correct adult and child head models using the IEEE standard (Std. C95.3-2002) SAR averaging algorithm. The child head models were obtained by linear scaling of the adult head model to replicate the conditions of previous studies reported in the literature and also by transforming the different adult head models based on data on the external shapes of childrens heads. The tissue properties of the adult and corresponding child head models were kept the same. In addition, modeling and experimental measurements were made using three spheres filled with a tissue-equivalent mixture to approximate heads of increasing size. Results show that the peak local average SAR over 1 g and 10 g of tissue and the electromagnetic energy penetration depths are about the same in all of the head models under the same exposure conditions. When making interlaboratory comparisons, the model and the SAR averaging algorithm used must be standardized to minimize controversy.

A Review of Microwave Irradiation and Actions of Psychoactive Drugs

H. Lai irradiation on the action of barbiturates. Mice exposed to A. Horita continuous-wave (CW) 2450 MHz microwaves at 25 to 50 C. K. Chou mW/cm2 showed a dose (power density)-dependent reducA. W. Guy tion in the duration of hexobarbital anesthesia [5]. The effect University of Washington School of Medicine was claimed to be unrelated to stress, as plasma corticosterone level was lower in the irradiated animals than in the controls. Baranski and Edelwejn [61 reported that acute S IMILARITIES exist between microwave irradiation and pulsed microwave irradiation (20 mW/cm2) had little effect drugs with regard to their actions on biological systems. In on the EEG pattern of rabbits given phenobarbital. However, both cases, certain effects follow their absorption into the in chronically exposed animals (7 mW/cm2, 200 h), desynbodies of test animals. Power density and specific absorption chronization of the EEG pattern was seen after phenobarbital rate (SAR) of microwave irradiation are analogous to the administration, whereas synchronization was seen in the concentration of the injection solution and the dosage of drug controls [7]. However, Benson, et al. [81 demonstrated administration, respectively. Conceivably, SAR would be the decreased onset-time and prolonged duration of phenobarbimore pertinent indicator of the resulting effect; similar to the tal-narcosis in mice after irradiation with microwaves (CW, dose-response relationship of drug action, the effect of 10 mW/cm2, 10 min). These effects were caused by an microwave irradiation should be proportional to the SAR. increase in deposition of phenobarbital in the brain. Rabbits Furthermore, analogous to drug effects, the effect of microanesthetized with pentobarbital and then subjected to 5 min waves should be the sum of specific (direct) and nonspecific of microwave irradiation (CW, 0.7 to 2.8 mW/cm2) showed (indirect) effects on the physiological process being studied. periods of alternating EEG arousal and sedation and periods of A further corollary is that consequences similar to those of behavioral excitation [9]. The duration of arousal seemed to drug treatment, e.g., tolerance, sensitization, conditioning to correlate with the power density of the irradiation. Wangeenvironmental cues, and so forth, could occur after micromann and Cleary [10] have also reported that short-term wave irradiation. microwave irradiation (CW, 5-50 mW/cm2) decreased the However, additional properties of microwaves complicate duration of sodium pentobarbital-induced loss of righting this simplistic interpretation. First, in contrast to the relatively reflex in the rabbit. The investigators suggested that this homogeneous distribution of drugs in the body, microwaves effect could be related to the thermal effect of microwaves, have complex absorption patterns that depend on the paramwhich led to a decreased distribution of pentobarbital to the eters of the radiation. For example, differences in absorption central nervous system. Indeed, Bruce-Wolfe and Justesen rate are found even inregions of the brain only millimeters [11] have recently reported that warming an animal with apart [11. Different patterns of energy deposition could lead microwaves during anesthesia can attenuate the effects of to different effects and failure to replicate an effect observed pentobarbital. In a series of recent experiments we in another exposure condition. However, a dose (SAR)[Swearengen, Lai & Horita: Abst. Neurosci. Sci., 12:896, response relationship should be apparent when an effect is 19861 studied the effects of body temperature on pentobarbistudied in animals irradiated under the same exposure condital-narcosis. Hypothermia was prevented in pentobarbitaltions. A second consideration is doubt as to whether microinjected rats by warming with a heat lamp, which maintained waves have specific effects on body functions. The existence the colonic temperature at approximately 38°C. Such treatof specific microwave receptors, similar to drug receptors, is ment did not significantly affect pentobarbital-narcosis, as not likely. Thus, the major effect of microwaves could be judged by the duration of loss of righting reflex, as well as the nonspecific, e.g., as a consequence of changes in tissue concentration of pentobarbital in the brain. Thus, it is temperature, calcium efflux, etc. However, it is also possible interesting that micrQwaves could attenuate the narcoleptic that certain features of microwaves can trigger specific effects of pentobarbital [9-11]. Perhaps this effect of microneural responses; for instance, pulsed microwaves can affect waves is not caused by a generalized thermal effect but is the auditory system [21 and activate specific neural pathdependent on the localized pattern of heating in the body ways, and thermal effect on skin sensors could trigger a caused by the irradiation. specific pattern of thermoregulatory responses. These speWe exposed rats to 2450 MHz pulsed microwaves at 1 cific and nonspecific effects of microwaves can alter the mW/cm2 (2 As, 500 pps, whole-body average SAR 0.6 W/ functions of the nervous system and, in turn, modify the kg), which did not significantly affect the colonic temperature actions of psychoactive drugs. The objective of this paper is of the rat after 45 min of exposure. Effects of pentobarbital to review the research on the effects of microwave irradiation were studied after the exposure, and we found that microon the actions of psychoactive drugs, and to discuss the waves prolonged the narcolepsy and hypothermia induced by implications of the data regarding brain functions. the drug [12]. Interestingly, we also found that exposure of rats in two different orientations in our circular waveguide MICROWAVES AND THE ACTIONS OF (facing towards or away from the source) had different PSYCHOACTIVE DRUGS effects on the pentobarbital-induced hypothermia. In our In iew of the reported effects of low-level microwave exposure system the average whole bodySARs are similar in irradiation on brain functions and its complex effects on the two orientations of exposure, whereas localized absorpbehavior [3, 41, it is conceivable that microwave irradiation tion patterns are different [11. These data suggest that could also affect the action of psychoactive drugs. However, localized SARs are important considerations in determining little work has been done in this area, especially on the the effects of microwaves>.. effects of low-level microwaves (< 1 mW/cm 2). Drugs Affecting the Thermal Effect of Microwaves Barbiturates Studies on the effects of drugs on thermal responses to Several studies have investigated the effects of microwave microwaves have recently been reviewed by Jaucham [13].

Effects of low-level microwave irradiation on hippocampal and frontal cortical choline uptake are classically conditionable

In previous research, we found that sodium-dependent high-affinity choline uptake in the hippocampus and frontal cortex of the rat was lowered after acute (45 min) exposure to low-level 2450-MHz pulsed microwaves (power density 1 mW/cm2; average whole body specific absorption rate, 0.6 W/kg; 2 mu sec pulses, 500 pps). In the present experiment, we investigated developments of tolerance and classical conditioning to these effects of microwaves. Rats were exposed to microwaves in cylindrical waveguides in 10 daily sessions (45 min per session). In an 11th session, we subjected the rats to either microwave (study of tolerance) or sham exposure (study of conditioned effect) for 45 min, and immediately measured choline uptake in the hippocampus and frontal cortex. We found that tolerance, a decrease in response to microwaves, developed to the effect of microwaves on choline uptake in the hippocampus, but not in the frontal cortex. Conditioned effects were also observed: an increase in choline uptake in the hippocampus and a decrease in uptake in the frontal cortex. These data suggest that the effects of microwaves on choline uptake in the hippocampus and frontal cortex are classically conditionable, probably to cues in the exposure environment.

Long-Term 2450-MHz CW Microwave Irradiation of Rabbits: Methodology and Evaluation of Ocular and Physiologic Effects

AbstractIn order to assess the biological effects of long-term microwave radiation, special exposure systems were developed and used to expose four rabbits to 10-mW/cm2 microwave radiation (maximum 17 W/kg SAR) for 23 h per day for 180 days. Comparisons with four sham-exposed rabbits revealed no significant effects in terms of eyes, body mass, urinary output, rectal temperature, hematocrit, hemoglobin, white cell count, and basic blood-coagulation studies. After the experiment, the animals were sent to the National Institute of Environmental Health Sciences for additional analyses which revealed biochemical effects as reported in a companion paper in this issue.

Estimation of the SAR in the Human Head and Body due to Radiofrequency Radiation Exposure from Handheld Mobile Phones with Hands-Free Accessories

Abstract Bit-Babik, G., Chou, C. K., Faraone, A., Gessner, A., Kanda, M. and Balzano, Q. Estimation of the SAR in the Human Head and Body due to Radiofrequency Radiation Exposure from Handheld Mobile Phones with Hands-Free Accessories. Radiat. Res. 159, 550–557 (2003). It was reported by others that hands-free accessories increase the absorption of RF energy in a human head compared to a handset alone. The results of this study show that the opposite is observed when proper dosimetric methods are employed. It is pointed out that for correct estimation of the exposure level it is necessary to use appropriate physical and experimental models and measurement instrumentation, following internationally recommended standards. The human phantoms used for measurements involving the hands-free accessories should include the torso; i.e., measurements should not be performed on the head phantom alone. This has a significant impact on the results because the RF energy coupled into the leads of hands-free accessories is strongly attenuated by the body. Numerical simulations using the Finite-Difference Time-Domain (FDTD) method and experimental measurements with a miniature electric-field probe are in good agreement and show a decrease, not an increase, in RF energy exposure in the human head from hands-free accessories.

Microwave Effect on Rabbit Superior Cervical Ganglion

Rabbit superior cervical ganglia were exposed to continuous wave 2450 MHz fields within a temperature controlled waveguide environment. Absorbed power densities between 2 and 1000 W/kg failed to significantly influence conduction latencies of responses recorded from postganglionic fibers due to stimulation of either B (myelinated) or C (unmyelinated) fibers in the preganglionic trunk.

A System for Quantitative Chronic Exposure of a Population of Rodents to UHF Fields

A system has been developed for economically exposing a large portion of rodents on a long-term basis without disturbing their normal laboratory living patterns. The use of separate cells consisting of cylindrical wave-guide excited with circularly polarized guided waves provides relatively constant and easily quantifiable coupling of the fields to each animal, regardless of their position, posture, and moving patterns. The VSWR to each cell is sufficiently low that any number of cells can be coupled to a single source through a power splitter without the need for isolation circuitry.