IEEE EMF HEALTH & SAFETY STANDARDS

Transcription

1 IEEE EMF HEALTH & SAFETY STANDARDS Patrick A. Mason 1), Michael R. Murphy 1), and Ronald C. Petersen 2) Air Force Research Laboratory Human Effectiveness Directorate 1) Radio Frequency Radiation Branch Brooks Air Force Base, Texas, Independent Consultant Bedminster, New Jersey, ) Tel: , Fax: , ABSTRACT With roots dating back to 1884, the Institute of Electrical and Electronics Engineers (IEEE) is the world s largest technical professional society, with more than 325,000 members, 1/3 from outside the United States. The development of internationally recognized voluntary standards, through an open consensus process, has long been a major effort of the IEEE. In 1966, IEEE co-sponsored the first US radio frequency (RF) standard (C ). In 1982, C was the first national standard in which field limits were derived from the frequencydependent dosimetric quantity specific absorption rate (SAR). Dosimetry and a threshold SAR of 4 W/kg are now the bases for most of the world s RF safety standards and guidelines, including those of National Radiological Protection Board (NRPB), International Commission on Non-Ionizing Radiation Protection (ICNIRP), North Atlantic Treaty Organization (NATO), and the United States Department of Defense. INTRODUCTION The IEEE is one of the largest professional organizations and is composed of a number of professional societies (e.g., Engineering in Medicine and Biology Society; Microwave Theory and Techniques Society). Exposure standards pertaining to subjects that are of interest to more than one society (e.g., radio frequency safety standards) are developed by Standards Coordinating Committees (e.g., SCC-28, SCC-34) that are sponsored by the IEEE Standards Board. The history of the American National Standard Institute (ANSI)/IEEE RF/Microwave exposure standards is certainly impressive. There are several recent reviews of the ANSI/IEEE history and process [1-4]. In 1953, the 10-mW/cm 2 exposure standard was recommended to the United States Navy and this standard was based on simple thermal models. In 1959, the United States America Standards Institute (USASI) C95 project was chartered and sponsored by the United States Department of the Navy and IEEE. On November 9, 1966, the ANSI C standard was approved and was based on simple thermal models. This standard covered 10 MHz to 100 GHz, the exposure limit was 10 mw/cm 2, and the 0.1-hour (6 minute) averaging time was introduced. Remarkably, the entire standard was only 1.2 pages in length and the cover page is shown below: In 1971, the ANSI C standard was approved and limits were established for E 2 and H 2. In 1982, ANSI C was approved and this was the first national standard to incorporate dosimetry, was frequency dependent, and based on threshold SAR for behavioral disruption. The incorporation of limits based on SAR was critical since the incident and internal electromagnetic fields can be very different depending upon the size, shape, and composition of the object. As we know today, SAR is the common unit for comparing and extrapolating laboratory results from bioeffects studies. In 1986, the National Council on Radiation Protection and Measurements (NCRP) published exposure recommendations that were SAR based, set occupational exposure limits the same as ANSI C , and set lower limits for the general public. In 1988, the C95 committee became the IEEE SCC-28. In 1991, the IEEE Standards Board approved the C standard. This standard was two tiered, was based on SAR values, provided relaxation of limits for partial-body exposures, contained rules and definitions necessary for implementation, and was developed after an extensive evaluation of the scientific literature (see Attachment 1). During the literature assessment,

2 classifications of findings were made without prejudgement of the mechanisms of effects. The intent was to protect exposed humans from harm by any mechanism, including those from excessive elevation of body temperature. The Biological Validiation Working Groups were as follows: Behavior, Biorhythms, Cardiovasculature, Central Nervous System, Combined Effects, Development and Teratology, Endocrinology, Genetics, Hematology-Immunology, Metabolism and Thermoregulation, Modulation, Oncology, Physiology, and Visual Systems. The finding of these groups was that the most sensitive measures of potentially harmful biological effects were based on the disruption of food-motivated behavior in several animal species under wide-ranging field parameters (see Attachment 2). The Maximum Permissible Exposure (MPE) values are based on limiting the SAR to: Controlled/ Occupational Uncontrolled/ General Public Whole-Body 0.4 W/kg 0.08 W/kg Average Spatial Peak* 8.0 W/kg 1.6 W/kg * Per gram of tissue in the shape of a cube Controlled environments are locations where there is exposure that may be incurred by persons who are aware of the potential for exposure as a concomitant of employment, by other cognizant persons, or as the incidental result of transient passage through areas where analysis shows that the exposure levels may be above the MPEs for the uncontrolled environment, but do not exceed the MPEs for the controlled environment. Uncontrolled environments are locations where there is exposure of individuals who have no knowledge or control of their exposure. The exposures may occur in living quarters or workplaces where there are no expectations that the exposure levels exceed the MPEs for the uncontrolled environment. The exposure values (the values that are compared with the appropriate MPEs) in terms of electric and magnetic field strengths are the mean values obtained by spatially averaging the squares of the fields over an area equivalent to the vertical cross-section of the human body. The spatial averaging can be obtained by scanning (with a suitable measurement probe) a planar area equivalent to the area occupied by a standing adult human. An approximate method for spatial averaging is to make measurements at equal intervals (at least ten) along the axis of the projected area of the exposed subject. The spatial average is equal to the sum of the squares of the measured fields divided by the number of measurements. Above 15 GHz, the averaging time decreases with increasing frequency from 6 and 30 minutes for the controlled and uncontrolled environments, respectively, to 10 seconds at 300 GHz. The 10 second averaging time at 300 GHz (1 mm wavelength) is consistent with the ANSI Z (safe use of lasers) at 1 mm (where the two standards meet). The averaging time was reduced in the 1991 standard to preclude second degree (partial thickness) skin burns associated with short exposures at frequencies where the energy is absorbed in superficial tissues. For example, a 6-minute averaging time and a 5-mW/cm 2 MPE would allow exposure to a peak power density of 3.6 W/cm 2 for a 0.5 sec exposure (once every 6 minutes), which would be above the threshold for skin burn from a white light or infrared source. Overall, the recommendations made in the IEEE C standard are designed to prevent harmful effects in humans being exposed to electromagnetic fields in the frequency range of 3 khz to 300 GHz. These exposure limits are biologically based and reflect a consensus interpretation of relevant studies from the bioelectromagnetics literature by qualified scientists, physicians, and engineers. Adjustme nts to the recommendations as a convenience to special interest groups are not part of the process. In 1997, the literature evaluation began for the next revision of the exposure standard. This will be the most comprehensive literature evaluation ever take for a RF/microwave safety standard. Currently, there are approximately 1400 citations in the database ( and non-peer-reviewed publications, book chapters, and reports are included in the database. Evaluations are being completed by topic (engineering, epidemiology, in vivo, in vitro, peripheral). Some of the issues to be addressed in revising the standard are: microwave/millimeter wave averaging time, the need for two tiers, and spatial-peak SAR values and averaging volume. The IEEE SCC-28 is one of the several international organizations that develop safety criteria for RF/microwave exposure. For standards harmonization, it is important that members of these international organizations interact with one another to understand the rationale for exposure limits.

3 IEEE SCC PROCEDURES IEEE Standards are developed through an open consensus process (see Attachment 3). Approval of an IEEE Standard (at the subcommittee level and at the main committee level) requires a balance of interests on committees, 75% return of ballots (including abstentions), approval of 75% of returned ballots (excluding abstentions), attempts to reconcile all negative ballots, circulation of unreconciled ballots to allow voters to reaffirm, comment, or change their vote, and coordination with other societies and organizations. Currently in IEEE/ICES SCC-28, there are over 100 members from 13 countries. In recognition of the growing international membership of SCC-28, IEEE established the International Committee on Electromagnetic Safety (ICES) in March 2001 as an umbrella organization for SCC-28 and in the future for SCC-34 and any other SCC involved in developing standards for the safe use of electromagnetic energy. Members of the IEEE/ICES SCC-28 Executive Committee are: Chair: Dr. Eleanor Adair, Past Chair: Dr. John Osepchuk, Executive Secretary: Ronald Petersen, Treasurer: Arthur Varanelli, Membership: Dr. Tom McManus, and International Liaison: Dr. Michael Murphy. The Executive Committee is responsible for policy, procedures, broad direction, and administration, as well as, adherence to process. The five subcommittees and Chairs are: SC1: Techniques, Procedures, and Instrumentation; Howard I Bassen (hib@cdrh.fda.gov) SC2: Terminology, Units of Measurements, and Hazard Communication; Richard A. Tell (rtell@radhaz.co) SC3: Safety Levels with Respect to Human Exposures, 0 3 khz; Kent C. Jaffa (kent.jaffa@pacificorp.com) SC4: Safety levels with Respect to Human Exposures, 3 khz 300 GHz; Dr. C. K. Chou (ck.chou@motorola.com) and Dr. John A. D Andrea (john.dandrea@navy.brooks.af.mil) (john.defrank@amedd.army.mil) and G. Drew Koban (gkoban@relay.nswc.navy.mil) HOW TO JOIN SCC28 IEEE/ICES is an International Consensus Standard Setting Body. All are welcome to participate in the meetings and deliberations of SCC28 and to vote and participate fully on the Subcomittees. To apply for voting membership on SCC28, please send an or letter containing your resume to: Dr. Tom McManus, Membership Committee Chair, IEEE/ICES SCC28, Department of Public Enterprise, 44 Kildare Street, Dublin 2, Ireland (tommcmanus@dpe.ie). INFORMATION ON IEEE SCC34 SCC34 develops performance standards for products using or producing electromagnetic energy. For further information, contact the Chair: Ronald C. Petersen (r.c.petersen@ieee.org). REFERENCES [1] J.C. Lin, ANSI/IEEE Exposure Standards for Radiofrequency Fields, in Radiofrequency Radiation Standards Biological Effects, Dosimetry, Epidemiology, and Public Health Policy, B. Jon Klauenberg, M. Grandolfo, and D.N. Erwin, Eds., New York, Plenum Press, 1995, pp [2] J.M. Osepchuk and R.C. Petersen. Safety Standards for Exposure to RF Electromagnetic Fields, IEEE Microwave Magazine, 2: 57-69, 2001 [3] R.C. Petersen, New IEEE Standards on Measurement of Potentially Hazardous Radiofrequency/Microwave Electromagnetic Fields, in Radiofrequency Radiation Standards Biological Effects, Dosimetry, Epidemiology, and Public Health Policy, B. Jon Klauenberg, M. Grandolfo, and D.N. Erwin, Eds., New York, Plenum Press, 1995, pp [4] R.C. Petersen, Radiofrequency Safety Standards- Settings in the United States, in Electricity and Magnetism in Biology and Medicine, F. Bersani, Ed., London, Plenum Publishing, 1998, pp SC5: Safety Levels with Respect to Electro- Explosive Devices; John DeFrank

4 Attachment 1 LITERATURE SURVEILLANCE Engineering Evaluation In vivo and In vitro Biological Evaluation Mechanism s Epidemiology Statistical Validation WHERE APPLICABLE Evaluation of Exposure Risk Working Group THRESHOLD SAR

5 Attachment 2 Species and Conditions CW 225 MHz Pulsed 1.3 GHz CW 2.45 GHz Pulsed 5.8 GHz Norwegian Rat Power Density: SAR: 10 mw/cm W/kg 28 mw/cm W/kg 20 mw/cm W/kg Squirrel Monkey Power Density: SAR: 45 mw/cm W/kg 40 mw/cm W/kg Rhesus Monkey Power Density: SAR: 8 mw/cm W/kg 57 mw/cm W/kg 67 mw/cm W/kg 140 mw/cm W/kg

6 Attachment 3 IEEE SCC-28 Standard-Setting Process IEEE Standard American National Standard Subcommittee 4 working groups Main Committe e IEEE Standards Board American National Standards Institute Public Comment