- Rajiv Anand
If you live in an urban area, chances are that you are continuously bathing in variety of WiFi, Bluetooth, Cellular wireless signals without which modern living in unimaginable. If we could see beyond frequencies of light, we will be blinded by such EM radiation.
If your workplace employs wireless location technologies such as active and passive RFID, WiFI or BLE, there are additional sources of such radiation present around you. Should you be concerned?
Awareness and concerns about possible health effects of such radio technologies has been in existence for a long time. The quantity used to measure how much RF energy is actually absorbed in a body is called the specific absorption rate (SAR). In the case of whole-body exposure, a standing human adult can absorb RF energy at a maximum rate when the frequency of the RF radiation is in the range of about 80 and 100 MHz. Because of this resonance phenomenon, RF safety standards are generally most restrictive for these frequencies. UHF RFID, WiFI and BLE technologies operate at much higher frequencies.
The first concern is thermal effect on the human tissues. Studies have shown that environmental levels of RF energy routinely encountered by the general public are typically far below levels necessary to produce significant heating and increased body temperature. Beyond thermal effects, a number of informal studies for most of the radio spectrum have failed to establish a link. However if you are close enough to the transmitting source at certain power levels, you could be exposed to hazardous levels.
According to the U.S. Federal Communications Commission (FCC), the organization with oversight responsibility for RF safety guidelines, devices which emit radio energy must be certified to meet maximum permissible exposure (MPE) requirements, as specified in FCC 1.1310. The limits specified by the FCC vary based on frequency and the power density limits are specified as an average value over a 6-minute time period. The power density limit for the 902-928 MHz band in which UHF RFID operate (defined as the 915 MHz Industrial, Scientific and Medical band) is 0.6 mW/cm². The FCC validates a device using a calculation distance of 20 cm (7.9 in.) and notes RF exposure drops rapidly with distance.
The FCC limits for exposure are based on the effects of tissue heating in behavioral studies in animal subjects and afford the public a margin of safety 50-fold lower than the adverse effect exposure threshold. Other organizations that recommend exposure limits, including the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the Institute of Electrical and Electronic Engineers (IEEE), have also adopted guidelines consistent with the FCC’s.
The California Council on Science and Technology (CCST) an independent organization, sponsored in part by the state’s major universities and federal laboratories, conducted a data analysis review, titled “Health Impacts of Radio Frequency from Smart Meters” to assess the potential health effects of smart meter operation, that runs on the same frequency spectrum as UHF RFID. Result of their investigation didn’t establish any correlation of RF exposure to human health at the levels allowed by FCC.
In spite of all evidences, there is still a general concern for human safety around radio signals. A fair reason is that the long term effects are yet to be observed by our society considering the proliferation of wireless signals at the current levels is fairly recent in human history.
Keeping this concern in mind, Tagit’s RFID system design includes special assessment of workplace environments near RFID antennas, where continuous exposure at close range to human beings is possible. In such cases, restrictive measures such as including a movement and proximity sensor into design allows powering such antennas only when needed and keeping exposure levels way below the FCC thresholds