Radiofrequency and Microwave Radiation
Hazard Locations and Solutions
In recent years there has been considerable discussion and concern about the possible hazards of RF/MW radiation. Extensive research on this topic is underway in many countries. Natural low-frequency EM fields come from two main sources: the sun, and thunderstorm activity, but man-made fields at much higher frequencies have altered this natural EMF. At sufficiently high power densities, RF/MW energy can cause thermal effects that can cause blindness, and sterility. Non-thermal effects, such as alteration of the human body's circadian rhythms, immune system and the nature of the electrical and chemical signals communicated through the cell membrane have been demonstrated. However, none of the research has conclusively proven that low-level RF/MW radiation causes adverse health effects.
- Radio-Frequency and Microwave Radiation, Third Edition. American Industrial Hygiene Association (AIHA), (2004). Provides a detailed look at the physical characteristics of radio-frequency and microwave radiation, its generation and sources, how it interacts with matter, and its biological effects. Existing standards and guidelines are discussed, as are instrumentation and controls. A handy glossary provides definitions of important terms, and an appendix presents a list of problems industrial hygienists and other health professionals might face.
- Radiofrequency and Microwave Radiation in the Workplace. Ministry of Labour, Ontario, Canada, (June 2009). Describes health effects, exposure limits and ways to control RF/MW radiation.
Interference with Medical Devices
- Human Exposure to Radio Frequency and Microwave Radiation from Portable and Mobile Telephones and Other Wireless Communication Devices. Institute of Electrical and Electronics Engineers (IEEE) Committee on Man and Radiation (COMAR), (September 2000). Reports that sufficiently high levels of RF energy can interfere with other electronic equipment. This problem is more likely to occur with pulsed energy, which characterizes digital cellular telephones. Studies have shown that handheld cellular phones can affect the operation of heart pacemakers or defibrillators if the phone is placed directly over the device, and there have been reports of interference between cell phones and hearing aids. Individuals with pacemakers, implantable defibrillators, or other body-mounted medical electronic devices, should consult with their physician and/or the phone manufacturer to determine what precautions, if any, should be taken. Some manufacturers recommend that cell phones be used on the other side of the body from the implanted pacemaker.
- "Radio frequency interference with medical devices: a technical information statement." Institute of Electrical and Electronics Engineers (IEEE) Engineering in Medicine and Biology Magazine 17.3(May-Jun 1998):111-4.
- Hayes DL, Wang PJ, et al. "Interference with cardiac pacemakers by cellular telephones." New England Journal of Medicine 336(May 22, 1997):1473-9. (see also New England Journal of Medicine 336(May 22, 1997):1518-9; 337(October 1997):1006-7.)
- Electromagnetic Compatibility (EMC). U.S. Food and Drug Administration (FDA), Center for Devices and Radiological Health (CDRH).
- American Radio Relay League (ARRL)
- ARRL Handbook for Radio Amateurs. Newington CT: American Radio Relay League (ARRL), 1997.
- RF Radiation and Electromagnetic Field Safety. Presents thermal and non-thermal effects, safe exposure levels, cardiac pacemakers, typical RF field strengths, and RF awareness guidelines developed by the ARRL RF Safety Committee, based on the FCC/EPA measurements and other data.
- Amateur Radio RF Safety Calculator. Provides a main beam power density estimation program intended for use as part of a routine evaluation of RF safety compliance with FCC regulations. This is a World Wide Web front end for a public domain C program written by Ken Harker WM5R using the cgic library. This program has been derived directly from a public domain BASIC program written and published by Wayne Overbeck N6NB in the January, 1997 issue of CQ VHF, p. 33.
- ARRL Handbook for Radio Amateurs. Newington CT: American Radio Relay League (ARRL), 1997.
Cellular Phone Base Stations and Hand Held Cell Phones
- Cell Phones. U.S. Food and Drug Administration (FDA).
- How can I obtain the Specific Absorption Rate (SAR) value for my wireless phone? Federal Communications Commission (FCC). Indicates the SAR for a specific phone model can be obtained for many recently manufactured phones using the FCC identification (ID) number for that model. The FCC ID number is usually printed somewhere on the case of the phone. Sometimes it may be necessary to remove the battery pack to find the number. Once you have the ID number, go to the following Web address: Equipment Authorization (EA).
- What steps can I take to reduce my exposure to radiofrequency energy from my wireless phone? Federal Communications Commission (FCC). Recommends that users who conduct extended conversations by wireless phone every day, place more distance between their bodies and the source of the RF, since the exposure level drops off dramatically with distance. For example, use a headset and carry the wireless phone away from the body or use a wireless phone connected to a remote antenna.
- "Use Of "Protective Devices" For Cellular Telephones Technical Information Statement." Institute of Electrical and Electronics Engineers (IEEE) Engineering in Medicine and Biology Magazine 21.3(2002):105-6. If a mobile-phone user wants to reduce his or her exposure to RF energy, for whatever reason, he or she can:
- Limit the duration of calls
- Use a digital handset instead of an older analog model. In most, but not all cases, digital handsets operate at lower power levels than analog models. (The actual power level, however, depends on local conditions and can vary greatly.)
- Use "hands-free kits", which move the handset away from the body.
- Human Exposure to Radio Frequency and Microwave Radiation from Portable and Mobile Telephones and Other Wireless Communication Devices. Institute of Electrical and Electronics Engineers (IEEE) Committee on Man and Radiation (COMAR), (2000, September). Indicates that local SARs produced by hand-held, transportable, and mobile transceivers and cellular telephones normally do not exceed FCC and other safety limits. Present scientific evidence, as reviewed by standards setting organizations and other expert groups, does not demonstrate health or safety risks from cellular and other communications transceivers. A potential exists for interference between hand-held units and some medical devices that may be located in close proximity to them (within a few centimeters).
- Physical Agents Data Sheets (PADS) - Radiofrequency/Microwave Radiation. Alaska Department of Labor and Development. Requires employers who have people working around devices which produce radiofrequency/microwave radiation ensure that those devices are properly shielded to prevent leakage of radiation. The State of Alaska in its Alaska Occupational Safety and Health Standards has specified for incident electromagnetic energy frequencies from 10 MHz to 100 GHz, a Permissible Exposure Limit (PEL) of 10 mW/cm as averaged over any possible six-minute period.
Heating and Sealing Devices
- Radiofrequency (RF) Sealers and Heaters. U.S. Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 80-107, (December 1979). Reports that workers near RF sealers may be unaware of their exposure to RF emissions, because the RF energy from sealers and heaters can penetrate deeply into the body without activating the heat sensors located in the skin. The results of a NIOSH study indicate that the majority of the workers surveyed were exposed to RF energy at levels exceeding values citable by OSHA. The following controls are recommended:
- Properly design and install shielding material.
- Maximize the distance between the worker and the source of RF energy emission should be maximized. Examples of means to accomplish this include the use of automatic feeding devices, rotating tables, and remote materials handling.
- Tune the equipment electronically to minimize the stray power emitted.
- Whenever possible, equipment switch off equipment when it is not being used. Maintenance and adjustment of the equipment should be performed only while the equipment is not in operation.
- After the performance of maintenance or repair, all machine parts, including cabinetry, should be reinstalled so that the equipment is intact and its configuration is unchanged.
- Post warnings and information.
- Develop a medical surveillance program tailored to the expected degree of employee use of RF equipment and potential for exposure to RF energy.
- Take exposure measurements at regular intervals.
- Physical Agents Data Sheets (PADS) - Radiofrequency/Microwave Radiation - Safety and Health Precautions. Alaska Department of Labor and Workforce Development. Reports radiofrequency sealers and heaters have been among the major sources of employee exposure to radiofrequency/microwave radiation.
- When these machines are used, employees should use mechanical or electrical devices that allow them to stay as far away form the source of radiation as possible.
- Whenever possible, these sealers should be turned off when not being used. Maintenance and adjustment of this type of equipment should be performed only by trained technicians and only when the machines are turned off.
- Warnings should be posted to keep everyone away from the source of radiation except for those workers who are absolutely essential to performing the job.
- Microwave Ovens and their Hazards. Canadian Centre for Occupational Health and Safety (CCOHS). Identifies old or faulty door seals as the most common causes of microwave radiation leakage. Mechanical abuse, a build-up of dirt, or simple wear and tear of continued use can cause door seals to be less effective. Theoretically, there will be small amounts of leakage through the viewing glass but measurements have shown this to be insignificant. Safety tips for installation and maintenance of microwave ovens include:
- Take special care to ensure that no damage occurs to the part of the oven making contact with the door or door seals.
- Ensure that the microwave is unplugged or disconnected from electrical power before reaching into any accessible openings or attempting any repairs.
- Ensure that the adjustment of applied voltages, replacement of the microwave power generating component, dismantling of the oven components, and refitting of waveguides are undertaken only by persons who have been specially trained for such tasks. The services of a qualified repairman should be sought when any malfunction is suspected.
- Do not by pass the door interlocks.
- Do not test a microwave power generating component without an appropriate load connected to its output. The power generated must never be allowed to radiate freely into occupied areas.
- Microwave Oven. U.S. Food and Drug Administration (FDA), Center for Devices and Radiological Health (CDRH). Contains FAQs about microwave ovens, checking ovens for leakage, tips on safe microwave oven operation, and the erupted Hot Water Phenomena in Microwave Ovens.
Radio Broadcast Antennae
- Notice of Apparent Liability for Forfeiture. Federal Communication Commission (FCC), (January 6, 2005). Describes a violation of FCC rules resulting in a $10K fine. The case involves a worker climbing an FM broadcast tower.
Traffic Radar Devices
- Occupational Exposure of Police Officers to Microwave Radiation from Traffic Radar Devices. National Institute for Occupational Safety and Health (NIOSH), National Technical Information Service (NTIS) Publication No. PB95-261350, (June 1995). Recommends police officers take some simple steps which will sharply reduce their exposure to the low-level microwave radiation which these devices emit.
- Always point the device away from the police officer's body, or his/her partner's body, while it is turned on.
- Mount fixed radar antennas so that the beam is not pointed at any occupant of the patrol car.
- Whenever possible, turn off a hand-held unit when it is not in use. If the police officer's unit has a "standby" mode, always use it when not measuring the speed of a vehicle. Never rest the unit against the officer's body when it is turned on.
- When it is on, try to avoid pointing the device toward metal surfaces inside the police officer's car, such as the floor or a door, to avoid microwave reflection.