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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy Appendix A Interim Letter Report THE NATIONAL ACADEMIES Adviser to the Nation on Science, Engineering, and Medicine National Academy of Sciences National Academy of Engineering Institute of Medicine National Research Council DIVISION ON EARTH AND LIFE STUDIES Board on Radiation Effects Research November 15, 2002 Lt. Col. Richard Ashworth, Chief Bioenvironmental Engineering Office of the Command Surgeon Headquarters Air Force Space Command 150 Vandenberg Street, Suite 1105 Peterson AFB, CO 80914-4550 Dear Col. Ashworth, The National Research Council has been asked to update its 1979 report on the analysis of exposures to and potential biologic effects of the PAVE PAWS radar system. This update will be completed at a later date after an extensive review of available data. The committee is to first determine whether available research data on continuous and pulsed radiofrequency (RF) energy are adequate for determining the biologic and potential health effects of the PAVE PAWS phased-array system (see Appendix, lines 1–3 of Statement of Task). The Air Force has asked that this determination be communicated as a letter report. The committee’s initial assessment is that the data on continuous and pulsed RF energy are not adequate for determining the biologic and potential health effects of the PAVE PAWS phased-array system at this time. This conclusion is based on two observations. First, issues related to the rise and fall portions of the PAVE PAWS waveform have been raised, but cannot be addressed, because we have available only
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy preliminary, but inadequate, measurements of the PAVE PAWS waveform. These measurements are important to characterize transient aspects of PAVE PAWS radiation and to answer a question raised by others about the comparability of the PAVE PAWS phased-array radiation with radiation emitted by non-phased array systems. Hopefully, the significance of the PAVE PAWS wave shape will be clarified by the Phase IV measurement data . Second, although more than 2 decades of exposure to PAVE PAWS phased-array radiation has been experienced by the Cape Cod population which should allow a direct evaluation of any adverse health effects, there are currently inadequate data about the distribution of population exposures in the Cape Cod region. Adequate exposure data would be necessary to carry out this direct evaluation of the effects of the PAVE PAWS waveform. The 1978 and 1986 PAVE PAWS power-density measurements are limited to 37 locations in proximity to the PAVE PAWS site. Apparently these measurements were not designed to cover a wide range of census tracts for epidemiologic purposes. Use of epidemiologic methods is considered by this committee to be important to the determination of possible health effects of the PAVE PAWS radar. Accordingly, adequate power-density measurements that discriminate the PAVE PAWS emissions and that cover relevant census tracts are deemed necessary to facilitate the determination of possible health effects. It is our understanding that power-density measurements will be commissioned by the PAVE PAWS Steering Group for use in their epidemiology effort and that this information may be available to our committee as well. The committee considers access to these data to be important to items 2 and 3 of the committee’s Statement of Task (see Appendix, items 2 and 3 of the Statement of Task). After the phase IV data are evaluated and during the committee’s update of the 1979 National Research Council report, the committee will re-evaluate the adequacy of the existing RF energy literature for determining the potential biologic and health effects of the PAVE PAWS phased-array system. The committee further expects that the Phase IV measurement data, additional power density measurements, and computed exposure estimates that include a propagation model will be extremely useful in its attempts to evaluate the potential health effects of the PAVE PAWS radar on the Cape Cod population. The committee recognizes that much research has been conducted over the past 23 years that may provide insight into the possible biologic and health effects of PAVE PAWS radiation, and the committee will be reviewing the cellular, animal, and epidemiologic RF exposure and health effect data in detail. To this end the committee has constructed a set of potentially relevant RF field characteristics that will be used as guidelines in the identification of experiments in the literature that could be relevant to the update of the 1979 Research Council report (see Table). The ranges described are to indicate the focus of the committee’s review, though the committee may determine that certain data obtained under other exposure conditions are relevant to its task. It is beyond the scope of this letter report
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy Characterization of the PAVE PAWS Waveform and Identification of Waveform Characteristics Suitable for the Evaluation of Biologic and Potential Health Effects of PAVE PAWS Radar Characteristic PAVE PAWS Relevant Range of Data to Be Considered by the Committee Comments Frequency 420-450 MHz 10 MHz-2 GHza There are common mechanisms of interaction in the 10 MHz-2 GHz frequency range Incident Average Power Density <280 µW/cm2b <1 mW/cm2 or SAR <1 mW/g (<1 W/kg) Specific Absorption Rate increases for a given incident power with increasing frequency Modulation Pulse Pulse (CDMA, TDMA, IDEN, GSM, etc.) To include all existing RF pulse-modulation technologies Pulse Width 0.25-16 ms 0.001-100 ms Pulse Repetition Rate 0.02-20 Hz 0.01 Hz-10 kHz Pulse Rise Time (τR) >20 ns 10 ns < τR < 10 µs τR should be less than the charge relaxation time (ε/σ for biologic tissue, where ε is the dielectric permittivity of tissue, and σ the conductivity. Max estimated relaxation time is 10 ms. Exposure Duration Continuous Continuous-1 hr/day aUpper limit is intended to include cell-phone-frequency research (which goes as high as 1.9 GHz). The 2.45 GHz research in the literature is continuous RF energy and would be excluded by the modulation criteria (pulsed exceptions will be considered). bThe MITRE report on PAVE PAWS (2000) indicates that at the perimeter fence line the energy level does not exceed the IEEE thirty-minute average limit for human exposure. The IEEE limit is 280 microwatts per square centimeter. to list all possible sources of data that fall within the committee’s proposed criteria to be reviewed. The committee is using a database with more than 37,000 references in addition to the information that various members have acquired in working in the field of bioelectromagnetics for many years. It should be further noted that the extensive literature on power-frequency fields is not considered relevant to the evaluation of PAVE PAWS health effects in our study because the physical mechanisms of interaction between power-frequency fields and tissue,
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy on the one hand, and RF energy and tissue at low field strengths, on the other, are expected to be different. Furthermore, studies of power-frequency fields tend to concentrate on the effects of magnetic fields whereas studies on the effects of RF energy focus on power-density measurements or SAR’s. In addition, the committee proposes to focus on pulsed modulated fields rather than continuous wave fields. Continuous wave RF exposure experiments do not involve the same broad spectrum of energy and also utilize far lower peak exposure levels to attain the same average exposure levels. As a result, inclusion of continuous wave studies in the literature review may unfairly bias the observed results against any potential effects of exposure. References Cited MITRE. 2000. Kramer, A.G., B.P. Nelson, and R.E. Wakefield. RF Power Density Exposure at Ground Level for the PAVE PAWS Radar at Cape Cod - Questions and Answers. Bedford, MA. NRC (National Research Council). 2002. Letter Report to the Department of the Air Force from the Committee to Assess Potential Health Effects from Exposure to PAVE PAWS Low-level Phased-array Radiofrequency Energy: Recommendations for Phase IV Measurements. Washington, D.C.: National Academy Press http://www.nap.edu/books/NI000468/html/ Sincerely, Frank Barnes, Ph.D. Chairman Committee to Assess Potential Health Effects from Exposures to PAVE PAWS Low-level Phased-array Radiofrequency Energy
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy COMMITTEE TO ASSESS POTENTIAL HEALTH EFFECTS FROM EXPOSURES TO PAVE PAWS LOW-LEVEL PHASED ARRAY RADIOFREQUENCY ENERGY FRANK E. BARNES (Chair), University of Colorado at Boulder, Boulder, CO ROBERT C. HANSEN (Vice Chair), R. C. Hansen, Inc., Tarzana, CA LARRY E. ANDERSON, Battelle Pacific Northwest National Laboratories, Richland, WA GRAHAM A. COLDITZ, Harvard Medical School, Boston, MA FRANCESCA DOMINICI, Johns Hopkins University, Baltimore, MD KENNETH J. McLEOD, State University of New York, Binghamton, NY KEITH D. PAULSEN, Dartmouth College, Hanover, NH LESLIE L. ROBISON, University of Minnesota Cancer Center, Minneapolis, MN SUSAN L. SANTOS, University of Medicine and Dentistry of New Jersey and East Orange, War Related Illness and InjuryStudy Center, Medford, MA JAN A. J. STOLWIJK, Professor Emeritus, Yale University, New Haven, CT GAYLE E. WOLOSCHAK, Northwestern University, Chicago, IL NATIONAL RESEARCH COUNCIL STAFF EVAN DOUPLE, Study Director RICK JOSTES, Study Director TAJUANA CLAYTON, Project Assistant DORIS E. TAYLOR, Staff Assistant SPONSOR’S PROJECT OFFICER LT. COL. RICHARD ASHWORTH, U.S. Air Force
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy APPENDIX An Assessment of Potential Health Effects from Exposures to PAVE PAWS Low-level Phased-array Radiofrequency Energy Statement of Task The committee will first determine whether continuous and pulsed radiofrequency (RF) energy research data are adequate for determining the biological and potential health effects of the PAVE PAWS phased-array system. This determination will be communicated to the sponsor as a letter report. If the research data from continuous and pulsed RF energies are considered to be applicable for the determination of possible health effects of phased-array RF energy, the committee will use this information to update the 1979 National Research Council analysis of the exposure levels and potential biologic effects of the PAVE PAWS Radar System. If the data are not applicable, the committee will use other information that it determines to be relevant to phased array health effects to update the 1979 report. In this update the committee will evaluate potential biological and health effects, evaluate exposures of the public to electromagnetic energy from the PAVE PAWS system, and make recommendations for the need for, and focus of, additional scientific studies to address continued scientific uncertainty related to health outcomes and exposure to low-level radiofrequency energy emitted by the PAVE PAWS Radar System. At the completion of its work, the committee will provide an update of the 1979 Research Council report that includes a discussion of: The applicability of, and the level of uncertainty associated with, using data derived from cell, animal, and epidemiological studies employing continuous-wave exposure for evaluation of potential adverse health effects following phased-array exposures; The extent of the exposure of the public to electromagnetic energy from the PAVE PAWS system; Potential biological and health effects of the PAVE PAWS Radar System, and Recommendations for appropriate follow-on study design issues, including the strengths and limitations of the approaches suggested and the potential value of the proposed work. REFERENCE NRC (National Research Council). 1979. Analysis of the Exposure Levels and Potential Biologic Effects of the PAVE PAWS Radar System. Washington, DC: National Academy Press.
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