![]() ![]() Thermal effects: RF fields have been studied in animals, including primates.WHO has also concluded that there is no convincing scientific evidence that exposure to RF shortens the life span of humans, or that RF is an inducer or promoter of cancer. A number of national and international peer review groups have concluded that there is no clear evidence of links between RF exposure and excess risk of cancer. However, because of differences in the design and execution of these studies, their results are difficult to interpret. Cancer-related studies: Many epidemiological studies have addressed possible links between exposure to RF and excess risk of cancer.There are also a number of studies that report non-thermal effects, where no appreciable rise in temperature can be measured. They probed into physiological and thermoregulatory responses, behavioural changes and effects such as the induction of lens opacities (cataracts) and adverse reproductive outcome following acute exposure to relatively high levels of RF fields. Most studies conducted to date examined health effects other than cancer. The average output power is very low - a few milliwatts - and so the units are not considered hazardous to health, even when used in very close proximity to the body. Speed control radars are hand-held by police in many countries. In accessible areas on most watercraft, these levels would fall to a few percent of present public RF exposure standards. Under normal operating conditions, with the antenna rotating, the average power density of the higher power systems within a metre of the antenna is usually less than 10 W/m2. ![]() Peak powers of these systems can reach up to 30 kW, with average powers ranging from 1 to 25 W. ![]() Marine radars can be found on small pleasure boats to large ocean going vessels. The military also use most other types of radars described below. Members of the public would not be exposed to these emissions because during ground testing of radars access to these areas by all personnel is prohibited. These units have relatively high average powers (kW) and small area antennas, making it possible to have power densities up to 10 kW/m2. However, small military fire control radars on aircraft can be hazardous to ground personnel. Outside the site boundary RF field levels are usually unmeasurable without using sophisticated equipment. However, because its power is radiated over a large surface area, the power densities associated with these systems vary between 10 and 100 W/m2 within the site boundary. Large size radars often evoke concern in communities living around them. Military radars are numerous and vary from large installations, which have high peak (1 MW or greater) and average powers (kW), to small military fire control radars, typically found on aircraft. As with air traffic control radars, under normal conditions, they pose no hazards to the public. They operate at higher frequencies but generally have lower average and peak powers. Weather radars are often co-located with air traffic control radars in remote areas at airports. Under normal operating conditions, these systems pose no hazard to the general public. Typical air traffic control radars can have peak powers of 100 kW or more, but average powers of a few hundred watts. They are generally located at elevated positions where the beam is inaccessible to persons on the ground. Some of the common types of radars encountered in daily life include the following.Īir traffic control radars are used to track the location of aircraft and to control their landing at airports. The basic dosimetric quantity for RF fields above 10 GHz is the intensity of the field measured as power density in watts per square metre (W/m2) or for weak fields in milliwatts per square metre (mW/m2) or microwatts per square metre (µW/m2).Įxposure to RF fields above 10 GHz at power densities over 1000 W/m2 are known to produce adverse health effects, such as eye cataracts and skin burns. RF fields above 10 GHz are absorbed at the skin surface, with very little of the energy penetrating into the underlying tissues. SAR is the quantity used to measure the dose of RF fields between about 1 MHz and 10 GHz.Īn SAR of at least 4 W/kg is needed to produce known adverse health effects in people exposed to RF fields in this frequency range. The unit of SAR is watts per kilogram (W/kg). Absorption of RF fields in tissues is measured as a Specific Absorption Rate (SAR) within a given tissue mass. The depth of penetration depends on the frequency of the field and is greater for lower frequencies. RF fields below 10 GHz (to 1 MHz) penetrate exposed tissues and produce heating due to energy absorption. RF fields within this part of the electromagnetic spectrum are known to interact differently with human body. They generate EMFs that are called RF fields. Radars usually operate at radio frequencies (RF) between 300 MHz and 15 GHz. ![]()
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