Microwave News ~ FDA Workshop 1997

Physical Characteristics and Possible Biological Effects of Microwaves Applied in Wireless Communication

Workshop held in Rockville, MD, February 7, 1997

Abstracts:

DOSIMETRY FOR IN-VITRO AND IN-VIVO EXPOSURES AT CELLULAR TELEPHONE FREQUENCIES. Christopher C. Davis, Electrical Engineering Department, University of Maryland, Colllege Park, MD 20742.

The measurement of SAR at cellular telephone frequencies duning in-vitro experiments will be discussed. Important design issues that should be considered in performing such experiments will be reviewed. The temperature rises that occur in such experiments must be known. For in-vivo exposures, especially of humans, only indirect dosimetry is practicable and utilizes accurate anatomical models, reliable dielectric data, and numerical modeling of energy absorption.

EFFECTS OF RADIOFREQUENCY ELECTROMAGNETIC RADIATION ON CELL PROLIFERATION. Ewa M. Czerska, Jon Casamento, Center for Devices and Radiological Health, Food and Drug Administration, Rockville, Maryland 20857, U.S.A.; John T. Ning, Indian Health Service, Rockville, Maryland 20857 and Brown University, Providence, Rhode Island 02905, U.S.A.; and Christopher Davis, Electrical Engineering Department, University of Maryland, College Park, Maryland 20742, U.S.A.

Associated with the popularity of wireless communication is the issue of possible biological effects caused by microwave exposure. Human exposure to cellular phone radiation is likely to be localized to part of the head and repetitively applied for various lengths of time. The actual field may vary in frequency and intensity, depending on the type of phone. Some phone types utilize microwaves modulated at extremely low frequencies. This may be the basis for additional concerns because of reports of biological effects from exposure to extremely low frequency electromagnetic fields, including reports (1, 2) of stimulation of cell proliferation in vitro under temperature controlled conditions.

In the present experiment, cells of the human glioblastoma cell line T98G were exposed to 827 MHz frequency modulated radiation, with a waveform identical to that used in digital cellular phones. Each cell culture was exposed in a Crawford cell at either a SAR of 1.6 W/kg (the maximum spatial peak exposure level recommended for the general population in the ANSI C95.1-1991 standard) or at 4.767 W/kg (the maximum exposure level available from our system, which lead to a temperature rise of 1oC). The SAR was determined from temperature/time heating curves produced by exposure to the maximum power available from our system (8.8W forward power). Control cultures were simultaneously placed in a non-activated Crawford cell in the same incubator. Cultures were exposed or sham-exposed for 24 hours continuously. Minimally invasive temperature probes were placed in the tissue culture flasks in both Crawford cells, and temperatures were recorded by computer at 10 min. intervals.

Because of reported associations between cellular phone exposure and the occurrence of a brain tumor, glioblastoma, a human glioblastoma cell line, T98G, derived from a glioblastoma multiforma tumor, was used in line, T98G, derived from a glioblastoma multiforma tumor, was used in this study. The line has an indefinite life span, is anchorage independent, and can be arrested in G1 (before DNA synthesis) when crowded or deprived of serum. The G1 arrest also provides a synchronized cell population in which changes in proliferation are convenient to observe. To start proliferation, G1 cells were trypsynized, resuspended and subdivided into identical aliquots in T25 T-flasks. Flasks were placed in the sham and exposure Crawford cells inside a CO2 incubator. After the 24-hour exposure, cells were examined for DNA content by flow cytometry in the cell cycle analysis program. The percentage of cells in G1, S and G2+M phase in the exposed vs. sham exposed tissue cultures was compared. Statistically significant increases in cell proliferation were observed at both exposure levels. The increase also appeared to be dose dependent. Recordings of temperature probes showed minimal heating at SAR 1.6 W/kg, and 1oC at SAR 4.767 W/kg. The 1oC increase may be responsible for part of the observed increase in cell proliferation at the higher SAR. However, a conventional heating temperature increase of 1oC did not stimulate cell proliferation to the same extent.

1. E.M.Czerska, E.Elson, C.C.Davis, M.L.Swicord, and P.Czerski: Effects of Continuous and Pulsed 2450-MHz Radiation on Spontaneous Lymphoblastoid Transformation of Human Lymphocytes in Vitro. Bioelectromagnetics, 13, No 4, 1992, pp.247-259.

2. Stephen F. Cleary, Guanghui Cao, Lo, Li-Ming Liu: Effects of Isothermal @.45 GHz microwave radiation on the mammalian cell cycle: comparison with the effects of isothermal 27 MHz radiofrequency radiation exposure. Bioelectrochemistry and Bioenergetics 39 (1966) 167-173.

NONTHERMAL EFFECTS OF MICROWAVE RADIATION ON MAMMALIAN CELLS: EXPERIMENTAL AND THEORETICAL RESULTS. Stephen F. Cleary, Ph.D., Bioelectromagnetic Laboratory, Department of Physiology and Biophysics, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298.

The precise degree of experimental control afforded by in vitro exposure systems has permitted investigation of direct cell physiological responses to microwave radiation under nonthermal exposure conditions. A variety of cellular alterations have been attributed to nonthermal microwave interactions. Such effects include: 1) altered cation transport and binding; 2) ion channel kinetic changes; 3) biochemical alterations; 4) effects on the mitotic cycle; and 5) modulation of cell proliferation and transformation. Whereas such effects are generally consistent with microwave-induced alteration of signal transductive pathways at the membrane surface detailed mechanistic has been elusive. Recent theoretical studies indicate spatially nonuniform microwave energy absorption on cell membrane surfaces due to field coupling with cell membrane bound water molecules. Predictions based on this interaction model will be described together with supporting experimental data derived from studies of microwave and radiofrequency radiation effects on cytikine/ receptor binding.

HEADACHES FROM CELL PHONES: ARE THEY REAL?, Allan H. Frey, 11049 Seven Hill Lane, Potomac, MD 20854, USA, voice 301.299.5181, E-mail:

The users of handheld cell phones seem to be increasingly reporting headaches associated with their use of the phones. It appears from the reports that it may be digital rather than analog phones that are associated with headaches. I did a series of experiments with human subjects years ago in which I used a band of frequencies that included the cell phone frequency. An incidental outcome of those experiments, in which headaches were encountered, indicate that the association of headaches with cell phone use is real. I am now starting experiments to determine if there is a causal effect and, if so, the mechanism.

EFFECTS OF RADIOFREQUENCY ELECTROMAGNETIC RADIATION ON THE NERVOUS SYSTEM, Henry Lai, Ph.D., Bioelectromagnetics Research Laboratory, Center for Bioengineering, University of Washington, Seattle, WA.

Because of an increase in the use of wireless communication devices such as cellular telephones in recent years, there is a concern on the possible hazardous health effects of exposure to radiofrequency electromagnetic radiation (RFR). Unlike the conditions in previous research on the biological effects of RFR, cellular telephone-related exposure involves intermittent exposure of variable durations of a relatively constant amount of body tissue (i.e., part of the head) to the radiation. In considering the biological effects of RFR, the intensity and frequency of the radiation and exposure duration are important determinants of the responses. For repeated exposure, as in the case of the use of cellular telephones, homeostatic compensatory response can occur. On the other hand, since a relatively constant response can occur. On the other hand, since a relatively constantamount of body tissue is exposed, cumulative effect could occur and lead to eventual break down of homeostasis and adverse health consequences. In addition, exposure could also involve RFR amplitude-modulated at low frequencies. This adds to the concern because extremely low frequency electromagnetic fields have been reported to cause biological effects.

Most of the energy from a cellular telephone antenna is deposited in the skin and the outer portion of the brain. From theoretical calculations (e.g., references 1-3), peak specific rate of energy absorption (SAR) in head tissue of a user can range from 2-8 W/kg per watt output of the device. A natural concern is whether the deposited energy could locally affect brain functions. Possible morphological, metabolic, and physiological changes in neural tissue should be considered. These effects could lead to temporary or permanent functional changes in the nervous system. A temporary change in brain functions after RFR exposure also could alter the behavior of an animal.

A review of the literature on the effects of RFR shows that exposure at relatively low specific absorption rate (SAR less than exposure at relatively low specific absorption rate (SAR less than 2 W/kg) under certain conditions could affect the nervous system [references 4 and 5]. This include effects on the blood-brain barrier, morphology, electrophysiology, neurotransmitter activity, and metabolism. However, great caution should be taken in applying the existing research results to evaluate the possible effect of exposure to RFR during cellular telephone use. It is apparent that not enough research data is available to conclude whether exposure to RFR during the normal use of cellular telephones can lead to any hazardous health effect. Since the parameters of RFR exposure, such as frequency, intensity, duration, waveform, etc, are important determinants of biological responses, research is needed to investigate the interaction of these parameters. Particularly, studies using RFR frequencies emitted from cellular telephones and intermittent exposure schedule resembling the normal pattern of phone use are needed.

References

[1] Dimbylow, P.J., FDTD calculatiuons of SAR for a dipole closely coupled to the head at 900 MHz and 1.9 GHz, Phys Med Biol 38:361-368, 1993.

[2] Dimbylow, P.J. and Mann, J.M., SAR calculations in an anatomically realistic model of the head for mobile communication transceivers at 900 MHz and 1.8 GHz. Phys Med Biol 39:1527-1553, 1994.

[3] Martens, L., DeMoerloose, J., DeWagter, C. and DeZutter, D., Calculation of the electromagnetic fields induced in the head of an operator of a cordless telephone. Radio Sci 30:415-420, 1995.

[4] Lai, H. Research on the neurological effects of nonionizing radiation at the University of Washington. Bioelectromagnetics 13:513-526, 1992.

[5] Lai, H. Neurological effects of microwave irradiation. In: "Advances in Electromagnetic Fields in Living Systems, Vol. 1", J.C. Lin (ed.), Plenum Press, New York, 1994, pp. 27-80.

References

SPONTANEOUS AND CHEMICALLY INDUCED BRAIN TUMORS IN RATS CHRONICALLY EXPOSED TO DIGITAL CELLULAR PHONE FIELDS; A POSSIBLE BALANCE BETWEEN DAMAGE AND REPAIR IN MOLECULAR REGULATION OF CELL GROWTH. Ross Adey, VA Medical Center, Loma Linda CA 92357

We have reported (Proc. Bioelectromagnetic Soc., 18th Annual Meeting, 1996) incidence of spontaneous and chemically initiated brain tumors in Fischer rats, chronically exposed to cellular telephone fields conforming to the North American Digital Cellular (NADC) standard (carrier frequency 836.55 MHz, near field density at skin surface 1.0 mW/cm2, 3:1 multiplexed TDMA (Time-Division-Multiple-Access) modulation, 33% duty cycle). We sought evidence of brain tumor promotion by digital phone fields In rats exposed in utero to a single dose of the short-lived carcinogen ethylnitrosourea (ENU), and thereafter, exposed intermittently to digital phone fields for 24 months (mean life span, 26 months). Rats were in 4 groups: ENU/Field (EF); ENU/Sham (ES): Sham/Field (SF): and Sham/Sham(SS). The TDMA field had no enhancing effect on incidence, type, or location of spontaneous nervous system tumors. At experiment termination. with 182 of 236 rats surviving (77%), the TDMA field appeared to reduce incidence of brain malignant glial tumors in Groups EF vs. ES (4 vs 13) that had received the drug ENU. The TDMA field also appeared to reduce incidence of spontaneous glial tumors In Groups SF vs SS (2 vs 7). The TDMA field appeared to prolong latency of appearance of both spontaneous and ENU-induced glial tumors; and to favorably influence survival rates, with consistently higher death rates throughout the experiment in the following progression across groups: SF-SS-EF-ES. Trends were consistent but only approached statistical significance, due to small numbers.

Other animal studies with microwave exposures in utero have reported either delayed tumor appearance, (Preskorn et al., 1978) or prolonged survival (Preskorn et al., 1978; Prausnitz and Susskind, 1958). X-ray exposure in utero at the time of ENU dosage has also reduced subsequent brain tumor Incidence (Warkany et al., 1976), through activation of AT enzymes that participate in DNA repair (Stammberger et al., 1990). Consistent with that in DNA repair (Stammberger et al., 1990). Consistent with that model, our study suggests a possible enhancing action of TDMA fields in mechanisms of DNA repair. Single-strand DNA breaks occur normally in all cells, and observed incidence is a balance between damage and repair. Thus, raised oxidative damage in cancer, as through actions of reactive nitrogen and reactive oxygen species, may arise in increased damage or decreased repair (Wiseman et al., 1995). Failure of lymphocyte DNA repair after X-ray challenge has been reported in blood from a cluster of mid- life cases of breast cancer, where heavy juvenile chest X-ray dosage was implicated (Helzlsouer et al, 1995).

Both ELF and ELF-modulated RF fields act jointly with chemicals at cell membrane receptors that activate growth regulating enzymes inside cells. Ukin, Luben et al. (1995) have reported that 6OHz, 1G magnetic fields modulate a receptor-mediated enzyme cascade in pre-B lymphocytes. They conclude that the fields may interfere with programmed-cell-death (apoptosis), with surviving clones eventually participating in B-cell leukemia of childhood. Apoptosis is triggered (anoikis) when extracellular matrix proteins lose their binding to cell surface receptors (integrins). Apoptosis resistance, rather than cell at cell membrane receptors that activate growth regulating enzymes inside cells. Ukin, Luben et al. (1995) have reported that 6OHz, 1G magnetic fields modulate a receptor-mediated enzyme cascade in pre-B lymphocytes. They conclude that the fields may interfere with programmed-cell-death (apoptosis), with surviving clones eventually participating in B-cell leukemia of childhood. Apoptosis is triggered (anoikis) when extracellular matrix proteins lose their binding to cell surface receptors (integrins). Apoptosis resistance, rather than cell proliferation, is the major defect causing unchecked growth (Fritsch at al., 1994). It is seen in carcinoma cells, leading to chemo- and radiation therapy resistance.

Concepts of DNA damage as a sole and sufficient basis for tumor formation (genotoxic carcinogenesis) are challenged by evidence that tumors may result from factors not acting directly on nuclear DNA (epigenetic carcinogenesis). Their sites of action may be at cell surfaces (Pilot and Dragan, 1990) and in the intercellular matrix (Fritsch et al.. 1994). (Supported by the Motorola Corporation)

MOBILE PHONES AND HEALTH EFFECTS: PROPOSAL FOR A RESEARCH PROGRAMME BY EU EXPERT GROUP, Kjell Hansson Mild, National Institute for Working Life, P. O. Box 7654, S-907 13 Umea, Sweden, Tel: (46+90) 16 50 98, Fax: (46+90) 16 65 08.

October 1995 the Commission asked a group of expert to prepare an action plan for research into possible health effects related to the use of mobile telephony. The expert group recently presented their work. The Group agreed with the European Commission in recognising the need to address public concern about possible health effects, but pointed out that only a few investigations have been carried out that address the question of exposure to emissions from mobile phones or base stations. Relevant epidemiological studies are sparse and incomplete where results so far remain inconclusive. In arriving at its conclusions and recommendations the Group examined the technology of the mobile phones; the exposure levels to which people may be exposed, and relelvant published biophysical, biological and epidemiological research. The Group makes concrete recommendations for further research and this includes studies on possible mechanisms of interaction of radiotelephne emissions with living tissues; genetic, cancer induction, immune and nervous system related effects and epidemiology.

MEASUREMENT OF DNA DAMAGE FOLLOWING IN VITRO EXPOSURE TO 835 MHz OR 2450 MHz ELECTROMAGNETIC RADIATION.R.S. Malyapa, E.W. Ahern, W. Straube, E. Moros, W. Pickard and J.L. Roti Roti, Radiation Oncology Center, Washington University School of Medicine, St. Louis, MO 63108

Recent reports suggest that exposure to 2450 MHz caused DNA ssb and dsb in rat brains (Bioelectromagnetics 3:207. 1995; Int. J. Radiat. Biol. 69:513, 1996). Therefore, we endeavored to determine if exposure of cultured mammalian cells to microwaves (MW) or radiofrequency radiation (RFR) causes DNA damage detectable by the alkaline comet assay. The alkaline comet assay (single cell gel electrophoresis). A sensitive method to assay DNA single strand breaks (ssb) and alkaline labile sites in individual cells, was used to measure damage after in vitro MW and RFR irradiation. C3H 10T1/2 mouse fibroblasts and U87MG human glioblastoma cells were used in this study. The cells were irradiated with either 835 MHz MW (either frequency modulated, FMCW, or code domain multiple access, CDMA modulated) or 2450 MHz continuous waves in specially designed radial transmission lines (RTL) that provided relatively uniform absorption of MW. SAR was calculated to be 0.16 W/kg for the 835 MHz and 0.7 and 1.9 W/kg for the 2450 MHz MW radiation. Each experiment included sham exposure(s) in a RTL. Temperatures in the RTLs were monitored in real time and were maintained at 37oC + 0.2oC. Irradiations were carried out for 2, 2 h+4 h incubation at 37oC, 4, or 24 h with 835 MHz MW or 2450 MHz. Cells were subjected to single cell gel electrophoresis, stained with propidium iodide and viewed under a fluorescence microscope. The images were digitized and analyzed using a PC-based image analysis system. The "comet moment" and "comet length" were determined as described by Kent et al (Int. J. Radiat. Biol. 67:655, 1995). No significant differences were observed between the test groups and the controls after exposure to either 835 MHz or 2450 MHz radiation. In contrast, DNA damage was detected after irradiation with 0.3 - 0.6 cGy of gama-rays, after 24 hr of post irradiation incubation following a 2 Gy dose, after ~ 1 sec exposure to a 10 mW UV laser, and for BrdU labeled cells following exposure to fluorescent light. Thus, these radiations do not appear to cause DNA damage in cultured mammalian cells. (Support: Motorola Corporation)