Chapter 1 - Introduction. Chapter 2 - Engineering Controls. Chapter 3 - PPE. Chapter 4 - Admin Controls. Chapter 5 - Emergency Prep. Chapter 6 - Info and Training. Chapter 7 - Safe Chemical Use. Chapter 8 - Chemical Hazards. Chapter 9 - Haz Substances. Chapter 10 - Haz Chem Waste.follow url
RF and Microwave Radiation Safety
Chapter 11 - Hazardous Materials Shipping. Chapter 12 - Pesticides. Chapter 13 - Biohazards. Chapter 14 - Rad Hazards. Chapter 15 - Laser Hazards. Chapter 16 - Physical Hazards. RF radiation is produced by devices such as radio and TV transmitters, induction heaters, and dielectric heaters also known as RF sealers. MW radiation is produced by microwave ovens, parabolic dish antennas, and radar devices.
For the purposes of this manual we will be grouping RF and MW radiation together under RF as they have similar characteristics and reactions in human tissue. RF is a type of non-ionizing radiation. Common sources of RF radiation are shown below in Table 1.
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The nature and the degree of the health effects of overexposure to RF fields depend on the frequency and intensity of the fields, the duration of exposure, the distance from the source, any shielding that may be used, and other factors. The main effect of exposure to RF fields is heating of body tissues as energy from the fields is absorbed by the body. Prolonged exposure to strong RF fields may increase the body temperature, producing symptoms similar to those of physical activity. Hot spots can be caused by non-uniform fields, by reflection and refraction of RF fields inside the body, or by the interaction of the fields with metallic implants e.
There is a higher risk of heat damage with organs which have poor temperature control, such as the lens of the eye and the testes. There is currently no scientific studies or literature to support claims of non-thermal biological effects in humans due to RF exposures.
Radiofrequency Radiation (RF)
The response of the pacemaker or device is dependent upon the nature, frequency, and strength of the RF signal, the proximity of the pacemaker to the source, and the design of the pacemaker as it relates to the signal including shielding, sensing and polarity. Pacemakers that incorporate a sensing function are susceptible to EM interference by frequencies that mimic cardiac signals. Other hazards include contact shocks and RF burns. These can result from the electric currents which flow between a conducting object and a person who comes into contact with it while they are exposed to RF fields.
These effects should not be confused with shocks from static electricity. To date, these non-thermal effects are not known to result in health hazards in workers. Although we are constantly exposed to weak RF fields from radio and television broadcasting, no health risks have been identified from this low-level exposure.
Power density measures the amount of radiating energy crossing a given area in a given period of time. Both the EPA and OSHA have reported that in these cases it is possible for a worker to be exposed to high levels of RF energy if work is performed on an active tower or in areas immediately surrounding a radiating antenna.
Therefore, precautions must be taken to ensure that maintenance personnel are not exposed to unsafe RF fields.
Portable Radio Systems "Land-mobile" communications include a variety of communications systems that require the use of portable and mobile RF transmitting sources. These systems operate in narrow frequency bands between about 30 and 1, MHz.
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Radio systems used by the police and fire departments, radio paging services, and business radio are a few examples of these communications systems. There are essentially three types of RF transmitters associated with land-mobile systems: The antennas used for these various transmitters are adapted for their specific purpose. For example, a base-station antenna must radiate its signal to a relatively large area, and, therefore, its transmitter generally has to use higher power levels than a vehicle-mounted or handheld radio transmitter.
Although these base-station antennas usually operate with higher power levels than other types of land-mobile antennas, they are normally inaccessible to the public since they must be mounted at significant heights above ground to provide for adequate signal coverage.
Microwaves, Radio Waves, and Other Types of Radiofrequency Radiation
Also, many of these antennas transmit only intermittently. For these reasons, such base-station antennas have generally not been of concern with regard to possible hazardous exposure of the public to RF radiation. Studies at rooftop locations have indicated that high-powered paging antennas may increase the potential for exposure to workers or others with access to such sites, for example, maintenance personnel. Transmitting power levels for vehicle-mounted land-mobile antennas are generally less than those used by base-station antennas but higher than those used for handheld units.
Handheld portable radios such as walkie-talkies are low-powered devices used to transmit and receive messages over relatively short distances. Because of the low power levels used, the intermittence of these transmissions, and the fact that these radios are held away from the head, they should not expose users to RF energy in excess of safe limits. Therefore, the FCC does not require routine documentation of compliance with safety limits for push-to-talk two-way radios.
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Microwave Antennas Point-to-point microwave antennas transmit and receive microwave signals across relatively short distances from a few tenths of a mile to 30 miles or more. These antennas are usually rectangular or circular in shape and are normally found mounted on a supporting tower, on rooftops, on sides of buildings, or on similar structures that provide clear and unobstructed line-of-sight paths between both ends of a transmission path or link.
These antennas have a variety of uses, such as transmitting voice and data messages and serving as links between broadcast or cable TV studios and transmitting antennas. The RF signals from these antennas travel in a directed beam from a transmitting antenna to a receiving antenna, and dispersion of microwave energy outside of the relatively narrow beam is minimal or insignificant.
In addition, these antennas transmit using very low power levels, usually on the order of a few watts or less. Measurements have shown that ground-level power densities due to microwave directional antennas are normally a thousand times or more below recommended safety limits. Moreover, as an added margin of safety, microwave tower sites are normally inaccessible to the general public.
Significant exposures from these antennas could only occur in the unlikely event that an individual was to stand directly in front of and very close to an antenna for a period of time. Satellite Systems Ground-based antennas used for satellite-earth communications typically are parabolic "dish" antennas, some as large as 10 to 30 meters in diameter, that are used to transmit uplinks or receive downlinks microwave signals to or from satellites in orbit around the earth. The satellites receive the signals beamed up to them and, in turn, retransmit the signals back down to an earthbound receiving station.
These signals allow delivery of a variety of communications services, including long-distance telephone service. Some satellite-earth station antennas are used only to receive RF signals that is, just like a rooftop television antenna used at a residence and, since they do not transmit, RF exposure is not an issue. Because of the longer distances involved, power levels used to transmit these signals are relatively large when compared, for example, to those used by the microwave point-to-point antennas discussed above.
However, as with microwave antennas, the beams used for transmitting earth-to-satellite signals are concentrated and highly directional, similar to the beam from a flashlight. In addition, public access would normally be restricted at station sites where exposure levels could approach or exceed safe limits. Radar Systems Radar systems detect the presence, direction, or range of aircraft, ships, or other moving objects.
This is achieved by sending pulses of high-frequency electromagnetic fields EMF. Radar systems usually operate at radiofrequencies between megahertz MHz and 15 gigahertz GHz. Invented some 60 years ago, radar systems have been widely used for navigation, aviation, national defense, and weather forecasting. People who live or routinely work around radar have expressed concerns about long-term adverse effects of these systems on health, including cancer, reproductive malfunction, cataracts, and adverse effects for children.