Human exposure to radio fields from police radar guns.
We recognize public concern about the safety of exposure to electromagnetic fields. Recent allegations in the media link cancer with exposure to police radars, one of the lowest power microwave systems in our modern society -- typically between 10 and 100 milliwatts.
Guidelines for safe limits of exposure to microwaves have been published by the Institute of Electrical and Electronics Engineers (IEEE C95.1, 1991) and the American National Standards Institute (ANSI C95.1, 1982). These guidelines were developed to protect human beings from harmful exposure to radio frequency electromagnetic fields. Our Committee on Man and Radiation (COMAR) has stated that prolonged exposure at or below the levels recommended in ANSI C95.1-1982 is not hazardous to human health based on present knowledge (IEEE-USA COMAR, 1990).
Measurements and analysis of microwave exposures near properly operating police radar units have shown that even maximal exposure levels are well below these recommended safety limits. In addition, human exposures near police radar are substantially below the limits set by other national and international standards. Therefore, it can be concluded that microwave exposures near police radar are safe by existing standards and that there is no scientific basis for the alleged link of police radar with cancer.
This statement was developed by the Committee of Man and Radiation of the United States Activities Board of The Institute of Electrical and Electronics Engineers, Inc. (IEEE), and represents the considered judgment of a group of U.S. IEEE members with expertise in the subject field. The IEEE United States Activities Board promotes the career and technology policy interests of the 250,000 electrical, electronics, and computer engineers who are U.S. members of the IEEE.
Police radar was first introduced in the late 1940s as an offshoot of World War II radar technology. From time to time, there has been controversy over the accuracy of police radar in speed limit enforcement. Nevertheless, police radar has evolved into an accepted means of traffic control, with more than 75,000 radar units in use in the United States.
The microwave properties of speed radars have been known for years. In 1981, tests on 22 radar units showed that power densities were less than 3 mW/cm2 at the aperture and that exposure decreased with separation from the radiating horn (Baird, 1981). Police radar operates at X and K-band frequencies (i.e., 10-35 GHz), with a continuous-wave signal (no modulation), and with output power in the range of 10 to 100 milliwatts. The vast majority of police radars operate between 10-25 milliwatts, although a small number of 100 milliwatt devices are still in service. By comparison, the power output of a child's walkie- talkie is 35 milliwatts, and cellular hand-held radio-telephones operate at power levels of hundreds of milliwatts. In today's society, many products utilize similar technology and similar frequencies: alarm systems, automatic door openers, motion detectors, and various personal communications networks and inter-computer network systems. Thousands of products produce environmental radio-frequency fields at similar or higher intensities and in a broad range of frequencies (e.g., microwave ovens, mobile radios, electronic news gathering systems, broadcasting, amateur radio, and other devices).
Police radar is a low-power system when compared against today's inventory of existing radio-frequency systems. The total power, even if concentrated at a point as in a coaxial connector, is insufficient to produce pain or skin burn (Osepchuk, 1983). Microwaves at police radar frequencies are absorbed almost wholly in the skin, and the power densities near a police radar are well below the threshold for thermal sensation at X-band (Hendler, 1968).
Biological research with animals at these frequencies has shown biological effects only at much higher powers (Rosenthal, et al, 1976 and Hagan, et al, 1976). At least 1 watt of power is necessary to produce a cataract in irradiated rabbits at X-band. At 35 GHz, no cataracts result for less than 600 milliwatt contact application to the rabbit eye. Minimal corneal damage under contact conditions occurs only for at least 50 milliwatts delivered continuously for 0.5 hours to a small area in the eye.
Concerns about health effects (e.g., alleged cataracts) from police radar apparently first surfaced in 1987 in a letter distributed by Silicron Technologies (Tunnell, 1987). This claim received no scientific support and in time disappeared. In 1990, a police officer from Ohio, Gary Poynter, published a report (Poynter, 1990) that alleged a link between police radar exposure and cancer. As a prime example of biological effects of microwave energy at X-
band, Poynter selected the series of experiments on Tenebrio molitor reviewed by Heynick and Polson (1983). They, however, did not interpret these experiments as contradictions to ANSI C95.1-1982. Furthermore, some of the early work on Tenebrio molitor suggested effects of low power levels, which later were found not to exist (Olsen, 1981). The allegations of Poynter have been expanded in a series of media events -- particularly a series of articles in Law Enforcement News (1990-1991).
Recently, Fisher (1991) measured police radar units and confirmed the results of Baird (1981). Fisher concluded that maximum exposure during normal use of a hand-held radar device is less than 0.05 mW/cm2. The newer radars tend to be at lower power than older ones included in the 1981 tests. As a low power device, police radar is exempt from the requirement of providing evidence of compliance with ANSI C95.1-1982. This exemption was recently confirmed to our Committee on Man and Radiation by the Federal Communications Commission (Cleveland, 1991). Police radar has been examined by the Food and Drug Administration (FDA), and no action by the FDA relative to its responsibilities under the Electronic Product Radiation Control for Health and Safety Act of 1968 was deemed warranted (Anderson, 1991). THE FDA STATED THAT IT KNOWS OF "NO CONVINCING EVIDENCE OF A RISK OF CANCER OR OTHER HAZARDS FROM EXPOSURE TO THE LEVEL AND TYPE OF MICROWAVE RADIATION PRODUCED BY POLICE RADAR UNITS." As an extra precaution to "ensure that no violations of existing standards can occur," the FDA recently suggested that the radar antenna be kept at least six inches from the body while transmitting. The FDA also stated that "emissions from police radar units contain no ELF modulation and have not been associated with the present ELF-cancer controversy."
There is no scientific basis for worry that exposure to police radar may cause or promote cancer. Underlying our position is its reliance on the validity of existing science-based safety standards. Exposure to police radar satisfies the limits of not only IEEE and ANSI standards but also other standards both in the U.S. (NCRP, 1986) and elsewhere in the world (IRPA, 1988). We believe that continuing research on biological effects is necessary across the whole electromagnetic spectrum, in order to ensure an up-to-date refinement and improvement of existing safety standards.
1. Andersen, F. (1991), Letter to COMAR dated June 20, 1991. DCRH, FDA, Rockville, MD.
2. ANSI C95.1 (1982), American National Standard: SafetyLevels with Respect to Human Exposure Radio Frequency Electromagnetic Fields, 300 kHz to 100 GHz, IEEE Standards Dept., Piscataway, NJ.
3. Baird (1981), Field Strength Measurements of Speed Measuring Radar Units, NBSIR 81-2215, NBS, Washington, DC.
4. Cleveland, R. (1991), Letter to COMAR dated May 13, 1991. FCC Office of Engineering and Technology, Washington, DC.
5. Fisher, P.D. (1991), Microwave Exposure Levels Encountered by Police Traffic Radar Operators, Technical Report MSU-ENGR-91-007, Michigan State University, East Lansing, MI.
6. Hagan, et al, (1976) in Biological Effects of Electromagnetic Waves, C.C. Johnson and M.L. Shore, editors, Department of Health, Education and Welfare, pp. 143-153.
7. Hendler, E. (1968), "Cutaneous Response to Microwave Irradiation" in Thermal Problems in Aerospace Medicine, J.D. Hardy, editor. Surrey, Unwins Ltd.
8. Heynick, L. and Polson, P. (1983), "Bioeffects of Radio Frequency Radiation: A Review," USAF School of Aerospace Medicine, Brooks AFB, TX.
9. IEEE C95.1 (1991), Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz, IEEE Standards Dept., Piscataway, NJ.
10. IEEE-USA Entity Position Statement (1990) "Human Exposure to Microwaves and Other Radio Frequency Electromagnetic Fields," IEEE-USA COMAR, Washington, DC.
11. IRPA (1988), "Guidelines on Limits of Exposure to Radio Frequency Electromagnetic Fields in the Frequency Range from 100 kHz to 300 GHz," Health Physics, Vol. 54 (1) pp. 115-123.
12. Law Enforcement News, (1990-1991), a series of articles beginning Nov. 15, 1990 to March 15, 1991 on "Police Radar and Health Problem Allegations."
13. NCRP (1986), Biological Effects and Exposure Criteria for Radio Frequency Electromagnetic Fields, Report No. 86. National Council on Radiation Protection and Measurement, Bethesda, MD.
14. Olsen R. (1981), Microwave Induced Developmental Effects in the Common Mealworm (Tenebrio Molitor) - A Decade of Research, NAMRL Report No. 1283, U.S. Navy, Pensacola, FL.
15. Osepchuk, J.M. (1983), "The Microwave Stimulus," in Microwaves and Thermoregulation, E.R. Adair, Editor, Academic Press, NY, pp. 33-56.
16. Poynter, G. (1990), Traffic Radar: Human Experimentation Without Informed Consent available for $40.00 from Priority-One Consultants, 4535 West Sahara Ave., Suite 105-126M, Las Vegas, NV 89102.
17. Rosenthal, et al (1976) in Biological Effects of Electromagnetic Waves, C.C. Johnson and M.L. Shore, editors, Department of Health, Education, and Welfare, pp.110-125.
18. Tunnell, J., (1987) Letter on Police Radar from Silicron Technologies dated Jan. 7, 1987.