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STANDARDS AND GUIDELINES FOR EXPOSURE TO RADIOFREQUENCY AND EXTREMELY-LOW-FREQUENCY ELECTROMAGNETIC FIELDS

Many countries and several international organizations have adopted guidelines or standards for exposures to electromagnetic fields (EMFs) in occupational environments and for exposures of general (nonoccupational) populations. Such guidelines and standards are based on evaluation of the established scientific literature, including an evaluation of the consistency of the findings that have been reported. Preliminary data or unproven hypotheses are often difficult to convert into recommended limits, and their use could result in the need for frequent changes in limits as research develops. Guidelines are usually based on effects observed in organisms, and laboratory effects are often difficult to interpret for deriving limits for protection of human beings. Many guidelines consider exposures of occupational groups and the general population separately, in view of their differences in length of exposure and distribution of states of health and physiological reserve capacities.

Standards and guidelines are based on dosimetric considerations combined with absorption characteristics of the body at different frequencies of EMFs. The basic premise is that any adverse effects are proportional to the rate of radiofrequency (RF) energy absorbed, and the specific absorption rate (SAR) is a common measure for characterizing the prescribed limits. Several authors have reviewed the different RF standards and guidelines.1,2,3

Earlier standards and guidelines addressed limited frequency ranges, such as 300-300,000 MHz, but more recent standards and guidelines include the lower frequencies, down to 300 kHz or even 10 kHz. There are several standards and guidelines for electric-power frequencies of 50 and 60 Hz in the extremely-low-frequency (ELF) range.4,5,6

Many standards and guidelines are based on a conclusion from the relevant literature that, at a threshold RF exposure of about 4 W/kg, animals will show a change in their behavior when exposure conditions are well controlled. That threshold is reduced to 1 W/kg at high ambient temperatures. Most standards require that exposures be kept at or below one-tenth of the observed threshold SAR (0.4 W/kg). The recommended limits for the general population are reduced by a safety factor of 5 to an SAR of 0.08 W/kg, to allow for a greater range of physiological reserve capacity. For different frequency ranges, the recommended limits for unperturbed field strength and equivalent plane-wave power density are then adjusted for the different absorption characteristics of the human body. In the lower frequency ranges, further reductions in field strengths might be recommended to reduce the danger of RF burns from direct contact with metal objects.



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ASSESSMENT OF THE POSSIBLE HEALTH EFFECTS OF GROUND WAVE EMERGENCY NETWORK 10 STANDARDS AND GUIDELINES FOR EXPOSURE TO RADIOFREQUENCY AND EXTREMELY-LOW-FREQUENCY ELECTROMAGNETIC FIELDS Many countries and several international organizations have adopted guidelines or standards for exposures to electromagnetic fields (EMFs) in occupational environments and for exposures of general (nonoccupational) populations. Such guidelines and standards are based on evaluation of the established scientific literature, including an evaluation of the consistency of the findings that have been reported. Preliminary data or unproven hypotheses are often difficult to convert into recommended limits, and their use could result in the need for frequent changes in limits as research develops. Guidelines are usually based on effects observed in organisms, and laboratory effects are often difficult to interpret for deriving limits for protection of human beings. Many guidelines consider exposures of occupational groups and the general population separately, in view of their differences in length of exposure and distribution of states of health and physiological reserve capacities. Standards and guidelines are based on dosimetric considerations combined with absorption characteristics of the body at different frequencies of EMFs. The basic premise is that any adverse effects are proportional to the rate of radiofrequency (RF) energy absorbed, and the specific absorption rate (SAR) is a common measure for characterizing the prescribed limits. Several authors have reviewed the different RF standards and guidelines.1, 2, 3 Earlier standards and guidelines addressed limited frequency ranges, such as 300-300,000 MHz, but more recent standards and guidelines include the lower frequencies, down to 300 kHz or even 10 kHz. There are several standards and guidelines for electric-power frequencies of 50 and 60 Hz in the extremely-low-frequency (ELF) range.4, 5, 6 Many standards and guidelines are based on a conclusion from the relevant literature that, at a threshold RF exposure of about 4 W/kg, animals will show a change in their behavior when exposure conditions are well controlled. That threshold is reduced to 1 W/kg at high ambient temperatures. Most standards require that exposures be kept at or below one-tenth of the observed threshold SAR (0.4 W/kg). The recommended limits for the general population are reduced by a safety factor of 5 to an SAR of 0.08 W/kg, to allow for a greater range of physiological reserve capacity. For different frequency ranges, the recommended limits for unperturbed field strength and equivalent plane-wave power density are then adjusted for the different absorption characteristics of the human body. In the lower frequency ranges, further reductions in field strengths might be recommended to reduce the danger of RF burns from direct contact with metal objects.

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ASSESSMENT OF THE POSSIBLE HEALTH EFFECTS OF GROUND WAVE EMERGENCY NETWORK Some countries in Eastern Europe have adopted standards based on medical evaluations of workers in RF fields and on epidemiologic data on larger populations working or living in RF environments. That has resulted in the adoption of low limits that incorporate substantial safety factors. Standards abstracted from several sources are summarized in Table 10-1 and Table 10-2. Table 10-1 contains occupational exposure guidelines; Table 10-2 contains guidelines for the general public. In both tables, the guidelines are presented to represent frequencies as close as possible to those used by the GWEN system. The electric and magnetic fields induced in the human body by low-frequency and ultra-high-frequency radiation from the GWEN transmitters at locations outside the perimeter fence (see Chapter 3) are less than the accepted limits for general-public exposures stated in all the standards or guidelines, except those promulgated in the former Soviet Union.

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ASSESSMENT OF THE POSSIBLE HEALTH EFFECTS OF GROUND WAVE EMERGENCY NETWORK TABLE 10-1 OCCUPATIONAL EXPOSURE STANDARDS OR GUIDELINES FOR SEVERAL COUNTRIES OR AGENCIES Country or Agency Frequency (MHz) Electric Field (V/m) Magnetic Field (A/m) Power Density (W/m2) International Radiation Protection Association 0.1-1.0 614 1.6/f * --   > 1.0-10 614/f 1.6/f -- Australia 0.3-9.5 194 0.51 100   > 9.5-30 1,841/f 4.89/f 95/f Austria 0.01-0.03 1,500 350 --   0.03-2.0 1,500 7.06/f1.113 -- Canada (proposed) 0.01-1.2 600 4 --   1.2-3.0 600 4.8/f -- Germany 0.01-0.03 1,500 350 --   0.03-2.0 1,500 7.5/f -- Italy 0.3-3.0 194 2 --   0.3-3.0 (peak) 300 4 --   3.0-1500 61 0.16 10 United Kingdom 0.05-0.3 2,000 5/f --   0.3-10 600/f 5/f -- United States (ANSI) 0.3-3.0 614 1.58 1,000   3.0-30.0 1,892/f 4.74/f 9,000/f2 IEEE for controlled environments 0.003-0.1 614 163 --   0.1-3.0 614 16.3/f -- United States (ACGIH, 1991) 0.01-3.0 614 1.63 1,000   3.0-30 1842/f 4.89/f 9,000/f2 Former Soviet Union 0.06-1.5 50 5 --   1.5-3.0 50 -- -- * f = frequency in MHz

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ASSESSMENT OF THE POSSIBLE HEALTH EFFECTS OF GROUND WAVE EMERGENCY NETWORK TABLE 10-2 GENERAL PUBLIC EXPOSURE STANDARDS OR GUIDELINES FOR SEVERAL COUNTRIES OR AGENCIES Country or Agency Frequency (MHz) Electric Field (V/m) Magnetic Field (A/m) Power Density (W/m2) International Radiation Protection Association 0.1-1.0 87 0.23/f0.5* --   > 1.0-10 87/f0.5 0.23/f0.5 -- Austria 0.01-0.03 670 157 --   0.03-2.0 670 3.16/f1.113 -- Canada (proposed) 0.01-1.2 280 1.8 --   1.2-3.0 280 2.1/f -- Germany 0.01-0.03 1,500 350 --   0.03-2.0 1,500 7.5/f -- Italy 0.3-3.0 60 0.2 --   3.0-1500 20 0.05 1 United Kingdom 0.05-0.365 800 2 × 106/f --   0.365-0.475 800 5.5 -- United States (ANSI) 0.3-3.0 632 1.58 1,000   3.0-30.0 1,897/f 4.74/f 9,000/f2 Former Soviet Union 0.03-0.3 25 -- --   0.3-3.0 15 -- -- * f = frequency in MHz

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ASSESSMENT OF THE POSSIBLE HEALTH EFFECTS OF GROUND WAVE EMERGENCY NETWORK REFERENCES 1. Grandolfo, M., and K. H. Mild. 1989. Worldwide public and occupational radiofrequency and microwave protection guides. Pp. 99-134 in Electromagnetic Biointeraction, Mechanisms, Safety Standards, Protection Guides, G. Franceschetti, O. P. Gandhi, and M. Grandolfo, eds. New York, NY : Plenum Press. 2. Repacholi, M. H. 1990. Radiofrequency field exposure standards: Current limits and the relevant bioeffects data. Pp. 9-27 in Biological Effects and Medical Applications of Electromagnetic Fields , O. P. Gandhi, ed. Englewood Cliffs, NJ : Prentice Hall. 3. Szmigielski, S., and T. Obara. 1989. The rationale for the Eastern European radiofrequency and microwave protection guides. Pp. 135-151 in Electromagnetic Biointeraction, Mechanisms, Safety Standards, Protection Guides. G. Franceschetti, O. P. Gandhi, and M. Grandolfo, eds. New York, NY : Plenum Press. 4. American Conference of Government and Industrial Hygienists. 1990-1991. Threshold limit values and biological exposure indices. Am. Conf. Gov. Ind. Hygienists, Cincinnati, Ohio. 5. International Radiation Protection Association. 1990. Interim guidelines on limits of exposure to 50/60 Hz electric and magnetic fields. Health Phys. 58 : 113-122. 6. Grandolfo, M., and P. Vecchia. 1988. Standards on extremely low-frequency (ELF) electric and magnetic fields and their rationales. In Non-Ionizing Radiations: Physical Characteristics, Biological Effects and Health Hazard Assessment, M. H. Repacholi, ed. Proc. Int. Non-Ionizing Radiation Workshop, Melbourne, Australia, April 5-8, 1988.

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